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J11 y 23, 1946. 2,404,553 N. B. WALES‘, JR ELECTRIC FUSE AND SETTING APPARATUS Filed Aug. 6, 1941 ‘ 6' Sheets-Sheet 1 SETTER 0-4 ATTO R N r ' July 23, 145~ N. B. WALES, JR ELECTRIC FUSE AND SETTI-NG APPARATUS Filed.Aug. 6,. 1941 . 25,404,553 _ ‘ ‘ 6-Sheets-Shee-i 2“ '7 ATTORNEYS " July 23, 1946. ' N; B. WALES, JR 2,404,553 ELECTRIC FUSE AND SETTING APPARATUS Filed Aug. 6, 1941 6 Sheets-‘Sheet 3 * )F3 1\ 52 43 ATTORNEYS Juiy 23, 14. ‘ N. B. WALES, JR I 2,404,553 ELECTRIC FUSE ANDv SETTING APPARATUS ' Filed Aug. 6, 1941 e snee?s-she'et 5 I I5 | BBC ARMED INERT 67 ‘INVE ‘ ,R' "_ . - ATTQRNEYs ‘ Juiy 23, 1946. N. B. WALES, JR ‘ 2,404,553 ELECTRIC FUSE AND SETTING APPARATUS “ Filed Aug. 6,- 1941 e ‘Sheets-‘Sheet s ' v4 gbxwvémg. m -EWJMP %N ‘IE 2 n. ATTORNEY$ ‘ ' Patented July 23, 1946 2,404,553 UNITED STATES PATENT OFFICE ~ 4 ‘ 2,404,553’ .. V . . , , ELECTRIC FUSE AND sarrmo APPARATUS Nathaniel B. Wales, Jr., New York, N. Y. _ > . Application August 6, 1941, Serial-No. 405,570" 9 Claims. (Cl. 102—70.2), , 1 This invention relates to electric timing sys tems and methods adapted to set and initiate the operation of ordnance devices, such as explosive shells, submarine depth. charges, aircraft bombs, ?ares and the like, at a predetermined time meas ured from the instant of ?ring or release thereof. Heretofore, time fuses which have been em ployed in practice for similar purposes have been largely limited either to pyrotechnic fuses or to mechanisms of a purely mechanical nature, simi lar to a type of clockwork with a controllable escapement. Although electrical time fuses have previously been proposed, they have been sub ject to many disadvantages which are overcome by the present invention. ignitioncircuit in the fuse so that each element _ of those circuits may be chosen for optimum per: formance in its location. _ Not only is it thus pos sible to choose, the circuit-elements speci?cally’ for their intended functions, .but from thisrre sults simpli?cation of the entire 'mechanism, [greatly improved reliability and reduction of the physical'size and of the cost ‘of manufacture. To illustrate: the timing circuit of the fuse must employ accurate component parts, but little'ac tual electrical energy is required purely for tim-. ing, whereas the ignition circuit should include ample electrical energy to assureignition, but as long as it is sufficient the exact‘ quantity of 15 ignition energy is not important.v Therefore, by The time fuses and fusesetting apparatus in means of this separation of elements‘I am able accordance with the present invention include a to use in the timing circuit of the fuse [accu large number of advantages among which may rate timing condensers, preferably of the paper be mentioned compactness which is of particular wound type, and small both in'size'and capacity, , ' importance in shell fuses, accuracy of timing 20 and in the ignition circuit a high-capacity con regardless of weather conditions, simplicity of denser which need not'be especially accurate but ’ fuse parts, rapidity and economy in manufacture, if it be of the electrolytic type it will combine high and safety in use. The construction according to the invention also allows of thorough testing capacity with small size and low cost. 0 " ' In order that the ignition circuit may be dis of the fuses under the same conditions as in 25 charged at the expiration of an accurately timed actual use. The fusesetting apparatus in accordance with the present invention makes possible the set ting of each time fuse immediately, before it is released with its projectile. This enables the set ting of each time fuse individually before it is ?red or released, whether it bev on the ground or in an aircraft, for example, thus introducing great ?exibility in the control of the timing of interval, the discharge in the ignition circuitis ‘ controlled by relayraction initiated-in the tim ing circuit. In accordance with the preferred 30 form of my invention this relay action may be performed by a gaseous discharge tube of the three-electrode type, and thus the invention com prises an electronic time fuse. H > As an example of the great improvementsin detonation, with many resulting advantages 35 compactness introduced by the fuse of thisin vention, it may be mentioned that only two’con which heretofore have been impossible of at densers of sufficiently large electrostatic capac tainment, especially in warfare. The mentioned ity to furnish detonating energy at reasonable ?exibility of control includes the ability to set voltages would, if they also must be of an accu simultaneously while in ?ight all of the bombs in an aircraft, if they are to be dropped on the 40 rate type to be used fortiming purposes, oc-j cupy a volume about four times as great as the same target; and in the event of emergency, the ability to instantly render the timing circuits of all Of the bombs inert to make possible jettison volume occupied by three condensers according to the present invention. , _ > ‘ By combining certain electrical and mechani ing the bombs without detonation. Furthermore, the fusesetting apparatus of this invention al 45 cal features in the design of the fuse of this invention an unusually large number .of safety lows of a considerable range of control of the devices have been made possible, some of which 7 time periods to which the fuses may be set and are interdependent whereby the possibility of’ ac also includes provisions assuring readiness and cidental detonation is further prevented. ’ I accuracy of the settings, and the entire equip By employing low levels of energy in'the tim 50 ment may be self-contained and portable. ing circuit it is possible not only to improve the Many of the advantages above mentioned, as structure and operation of the fuse, but it ‘.is well as others which will appear hereinafter, re sult from the fact that my invention introduces likewise possible to simplify the structure‘ and the functional separation of the component ele improve the operation of the fusesetting appa ments of the timing circuit from those of the 55 ratus, because the, required setting voltage may 2,404,553 :15 d then be lower than would be required for tim ing condensers previously proposed. Many additional features and advantages of the present invention will appear from the fol lowing description which is to be read in connec be the same, depending on the requirements. tion with the drawings, wherein: Figure 1 is a circuit diagram of a complete time fuse system in accordance with my invention, in cluding timing apparatus and setting apparatus therefor, and which is especially adapted for use with time fuses for shells; Fig. 2 is a circuit diagram of an alternative em bodiment of the timing apparatus for shell fuses; Fig. 3 is a view in vertical section taken through a shell fuse incorporating many of the features of the present invention; Fig. 4 is a horizontal section through the line 4'.—4 of Fig. 3; Fig. 5 is a horizontal section through the line 5-5 of Fig’. 3; Fig. 6 is a circuit diagram of a time fuse and These condensers C1 and C2 may be of the paper wound type and be of small but accurate rated capacities. One terminal of resistor R1 is con nected to the contact d and the other terminal is connected to the control electrode or grid G of the gaseous discharge tube I. The output or controlled circuit of tube I in cludes in series an ignition condenser C3 and a resitsance 44 which in this embodiment com prises the element to be controlled, viz: a deto nator resistance or ignitor. One terminal of ig nition condenser C3 is connected to the common terminal E0 and also to the cathode K of tube I, and the other terminal of condenser C3 is con nected to the pole of switch 2| which moves to make connection with the contacts 0 and (1 ac cording to whether that condenser is to be placed in a charge or discharge position. This ignition condenser C3 may conveniently be of the elec setting apparatus therefor, particularly adapted trolytic type which has a large capacity and is much cheaper in high capacity sizes than a paper for use with aircraft bombs and ?ares, or sub type condenser. marine depth charges; ' Fig. 7 is a graphical representation of the charging voltages required to effect a certain pre selected range of delay in the time of detonation of one example of the fuse circuit of Fig. 6; Being merely a source of igi tion voltage the magnitude of its electrostatic capacity is not critical. In the embodiment here being described this condenser was of 8 micro farads. Fig. 8 is a View in vertical cross-section of a time fuse constructed in accordance with my in The operation of this timing circuit is as fol lows: Assuming switches 20 and 2| to be moved to the left to make connection with contacts 0 vention and adapted for use in connection with aircraft ?ares, bombs and the like; Fig. 9 is a horizontal section through the COll’l and that appropriate potentials are applied at terminals E1, E0 and E2, respectively, condensers C1 and C3 will be charged with corresponding po posite plane 8-——8 of Fig. 8; Fig. 10 illustrates in broken section a combi nation charging plug ejector and isolation switch structure applicable as a modi?cation to the structure of Fig. 8 ; Fig. 11 is a view in partial cross section of a modi?ed form of the ejector and switching de vice of Fig. 10, together with additional safety tentials. Then if condensers C1 an C3 be there ; after connected to the discharge contacts 01 by movements of switches 20, 2|, the charge in ig nition condenser C3 will continue to be stored therein because of the normally nonconductive condition of the discharge path of discharge tube I between plate P and cathode K. However, as soon as connection between switch 20 and con mechanism suitable for an aircraft bomb or ?are; Fig. 12 shows in side elevation the mechanism of Fig. 11 in a position in which it would be re leased from an aircraft; Fig. 13 is a circuit diagram of a preferred em bodiment of my invention as applied to aircraft tact d is made, condenser C2 which may be as sumed to have had no initial charge will begin to receive a charge from the potential of C1 fuse and fuse-setting apparatus; electrode G and cathode K of tube I. which will discharge through timing resistance R1. As the charge in condenser C2 increases, a rising potential is applied between the control This proc Fig. 14 illustrates graphically the time inter- ‘ _ ess continues at an exponentially decreasing rate determined by the magnitude of the resistance R1 and the initial charges in condensers C1 and C2 until the potential across G and K increases in a certain embodiment of the system shown 1n to the breakdown potential of the gas-discharge Fig- 13 path between those electrodes. As a typical ex An understanding of the timing system in ac cordance with my invention may be had by ref- . ; ample, this potential might be between 70 and 100 volts. When this potential is reached dis erence to Fig. 1 of the drawings, which is a cir vals as a function of impressed fuse voltages, for the several ranges of detonation time available cuit diagram of one modi?cation thereof as ap plied to the time fuse for a projectile such as a shell. In this circuit diagram is shown also a suitable fusesetting apparatus or circuit by which the timing circuits may be set to operate after a predetermined delay or time interval. In Fig. 1 the timing circuit proper is shown as charge occurs between G and K and the entire discharge path of the tube becomes ionized, and the effective resistance of the path between the plate P and cathode K is greatly decreased. This decrease in resistance of the discharge path a1 ows the charge stored in condenser C3 to be dis charged through resistance 44 which then be comes heated and effects the ignition or detona the bottom to a common terminal which com- -? 7 tion desired. The electrical charge stored in the comprising condensers Cl and C2 connected at prises a charging electrode E0 and to the oath ode K of a three-electrode gaseous discharge tube I. With switch pole 28 in connection with dis charge contact d, the other terminals of con densers C1 and C2 are connected together through a timing resistance R1 which, for example, may be of the order of magnitude of 150 megohms. In the particular embodiment of which Fig. 1 is a diagram, condensers C1 and C2 were of 0.5 mi ignition condenser should preferably be in ex cess of that required to effect ignition. From the foregoing description it will be ob served that gaseous discharge‘tube l is in eifect a relay, the discharge path between G and K being the control or input side and the discharge path between P and K being the controlled or output side. Thus, the discharge path of the relay tube operates effectively to couple the timing and igni crofarad each, although the capacities need not 75 tion circuits, these circuits otherwise being‘felec 2,404,553 6 trically isolated” from each other. or near the breach'mechanism soas to allow the shell to pass through the contacts in a continu The term “electrically isolated” is not used here nor in the appended claims to indicate that the ignition and timing circuits are electrically insulated from each other, but only that the ignition circuit is controlled by the timing circuit solely through the discharge path within the tube, and. that in all other respects the timing and ignition circuits, ous motion as it is moved toward or intothe breach. Thus, in rapid ?re operations, the timing of the fuses may be changed very rapidly and, im mediately before each shell is ?red. ‘ - J Switches 20 and 2| together with the electro magnet coil l5 represent an electro-mechanical relay which will be described in detail in con and the elements thereof, are functionally inde pendent of each other. Because this tube operates 10 nection with Fig. 3. It will here su?ice to state that switches 20 and 2| normally remain in the in response to an electrical impulse from the tim ing circuit to release the ignition energy its op neutral or unconnected position shown in Fig. 1, but when a charging potential is impressed across eration may be referred to as a “trigger” action. The use of such a relay introduces not only contact points Eo-—E2 the electromagnet I5 actu; the economies of space and expense, but also has 15 ates the relay and moves switches 20 andll to been found greatly to increase the accuracy of connect with the charging contacts 0, thusal timing and the raliability of operation of the entire system in the manner previously pointed lowing condensers C1 and C3 to be charged. After out. stored in these condensers and the charging volt- ‘ a very brief interval the'charge will have’ been ‘ Suitable timing circuit setting apparatus is 20 ages may be removed, whereupon switches 20,- 2i represented at the left of the charging terminals return to the neutral position shown. In this E1, E0 and E2, and may include any convenient position the charges will ‘be accurately retained source of direct current of sufficiently high volt and a minimum of leakage will occur even though age, an appropriate device for maintaining the thewexterior ofthe shell begimmer‘sed in water; output voltage constant under varying loads, and 25 Thereafter when the shell is ?red switches 20, 2| a control device whereby the charge stored in the are automatically moved by inertia'to make ‘con; timing circuit condenser may be adjustediin order nection'wi'th discharge contacts d whereupon the timing operation will commence and’ proceed 'as to set the timing circuit for the desired time in terval. The apparatus as here shown comprises a battery 52, such as a storage battery, and above described’until detonation occurs.v ator 5ll-5l. Generator 5| can be designed to have a higher voltage output thancould con veniently be obtained from a storage battery, for example. Any other suitable source of direct cur 35 rent at the required potential could of course be substituted; for instance, if alternating current ' "1 ” Fig. 2. is an alternative modi?cation of the a control switch 53 in circuit with a motor gener fuse‘ system shown in Fig. 1 and is in general sim: ilar thereto except that a four-pole switching ‘re-' lay, including coil l5 and switch arms Eli, 51, 58 and’ 59, is employed in place of the two¥pole switch shown in Fig. 1. . J ' In operation the circuit arrangement-of Fig. 2 differs from that of Fig. 1 in that both condensers C1 and C2 are charged to the same pro-selected charge type of voltage regulator tube T1 is shown 40 potential when the switch poles are thrown to the charging position 0. In this position the igni for maintaining more nearly constant the work were available a recti?er and ?lter could be em ployed. In the illustrated system a gaseous dis ing voltage of this voltage supply. A bleeder or potentiometer R3 is provided with tion storage condenser C3 is charged through switch pole-s 58,. 59 to a potential in itself capable of e?ecting. the necessary‘ ignition of resistance a ?xed tap 60 and an adjustable sliding contact indicated by the arrow. Thus the voltage as im 45 44 but incapable of discharging through the high resistance discharge'path P-—K" of gaseous dis-‘ pressed across charging condensers Cr and C5 will represent an adjustable voltage E1 and a ?xed charge tube l. However, when .the shell is ?red, voltage E2, respectively, in reference to the com i. e., on setback, the switches are thrown to the dis mon return or zero potential E0. This charging charge position 12 thus connecting condensers C1 system thus allows the calibration of potentiom and C2 in series across electrodes G and K of tube eter R3 in terms of time intervals, such as sec l, but with such polarities that the charges oppose onds. It is contemplated that the three contact points E1, E0, E2 may be connected by any suitable con each other and thus‘ resulting in an absence ‘of potential difference across. these two electrodes due to the initial equality, and opposition of their For this reason the discharge path ductive means, such as a multi-wire cable or 55 potentials. charging harness to three contacting areas or charging electrodes on the surface of the fuse body, such for example as those shown on the sur will not be triggered or ionized until condenser C2 has discharged itself su?'lciently through high resistance R1 as to produce'a difference of poten face of the shell fuse illustrated in Fig. 3, namely, tial between C1 and C2 'suf?cient to'initiate the 9, II and [6-H respectively. For the rapid set 60 required triggerldischarge between electrodes G ting of shell fuses a suitable box or receptacle may and K. Condenser C1 will discharge very slowly be arranged to include charging contacts so because there is connected across it the high re spaced that they will connect with the corre sistance R1 in series with the still higher.'resist~ sponding charging electrodes on the surface of ance of the non-conductive discharge path the shell. Thus before a given shell is ?xed it 65 G~—K. When this dischargeoccurs the relay ac; may be quickly inserted in such a charging re ceptacle and almost immediately withdrawn with the assurance that the timing and ignition con densers will have received the charges predeter mined to effect detonation after the desired de lay timed from the ?ring. A preferred embodi ment of such a charging receptacle provides for charging the fuses of shells as they are loaded into the breach of a gun. It may comprise an ar-. tion as described in connection with Fig. 4 results and the ignition charge stored in condenser C3 will be discharged through ‘detonator ignitor 44. The structure illustrated in Fig. 3 represents 70 an elevational view in section of a shell fuse which includes many features of the invention, although the construction is equally well adapted to a timing fuse for use in connection with any rangement of charging contact ?ngers secured to 17,5 type of projectile which would inpractice be sub, 2,404,553 ‘7 8 iected to a reasonably ‘high initial or discharge The shell fuse body of Fig. 3 is as a whole, as an ignition energy storage condenserwhich may preferably be of the electrolytic type, and in any event need not be of especial accuracy in rated shown, composed of two separable assemblies. capacitance, although it vshould be large enough The upper of these assemblies consists of the an nular metal block I6 and its associated parts, to store a charge more than normally required to e?ect ignition. These condensers may be re tained in their respective'cavities in any suitable manner, such as by a sealing compound. .Insu lated terminal lugs '28 serve as electrical tie points to interconnect the upper and lower as velocity. while the lower assembly consists of the metallic casing I'I, together with the components held within or secured to it. Upper block I6 forms with metallic plates 41 a chamber retaining an electromagnetic ?eld winding I5. The magnetic circuit of this winding includes magnetically permeable elements including block I6, plate 4? semblies in the stages of manufacture, after which the lower and upper assemblies may be secured together ‘by set screws 54. Cup 34 of suitable material which may be and the cylindrical armature slug I4 which is cen~ trally guided and axially free to move within a 15 screwed into casing I'I contains a detonating compound such as black powder, in Which ‘is im non-magnetic guiding sleeve 45. Screw I9 se bedded an ignition ?lament wire 44. The de cures to the lower extremity of the armature slug tonating leads 42 and 43 are connected to the ig I4, an insulating washer I8 carrying a peripheral nition wire terminals 45 and are suitably insulat groove 26. In this groove are carried spring switch leaves 20 and 2!. These switch leaves 20 ed, as shown, where they pass through the ‘walls of cup 34. Conduit holes 3| serve to carry leads when moved upwardly make contact, respectively, .132 and 43 up to the terminal tie-points 28. In with the upper or charge contacts 24 and 23, projectiles requiring accurate dynamic balance, and when moved to the downward position make duplicate holes 3| may be formed in the opposite contact, respectively, with the discharge contacts 25 and 24. Switch leaves 23 and 21%, as well as 25 side of the casing. The lower extremity of cas ing I'I carries, as shown, an external base thread the contact leaves or strips which carry contacts 32 which may engage a shell forging, and an vin 23 and 2d are shown more clearly in Fig. 5. Con ternal thread 33 which may be utilized to engage tact strips 22 and 25 are arranged similarly on a booster cup which usually includes a powder the opposite side of switch leaves 2i and 20. In charge, a centrifugal safety gate and other ele the drawings the same reference characters have ments of the usual ordnance shell. , been used for the switch contact leaves and for The upper assembly of the fuse includes a relay the contacts carried thereon. As many contact in the form of a gaseous discharge tube I which leaves and contacts as required may, of course, be is seated on an annular hard rubber cushion I3 All of the contact and switch leaves are spaced 35 within the cylindrical cavity of an insulating form employed. and insulated from each other by spacing insula tion 36 and 37 and insulating gaskets 35 and 38. ii which may be of Bakelite, for example. Be tween insulating form 8 and the wall of tube I a sleeve or tube 6 of suitable material such as fiber Six screws 2‘! symmetrically spaced secure the may be interposed. A rubber cushioning cap ‘I upper assembly parts into a unitary structure. Insulating and spacing members 35, 36 and 38 40 serves to complete the protection of relay tube I centralize and insulate screws 2'! from contact with leaves 26 to 25, inclusive. The upper extremity of armature slug I4 is formed to include a cam-shaped head 6i! which cooperates with two spring pins 12 to form look ing means for the armature and the switch leaves. As shown in Fig. 4 these pins pass diametrically through the entire upper fuse assembly in such by pressing it resiliently against the cushion I3. Within tube i are included, in the device illus trated, three electrodes of tungsten or other suit able metal, two of which‘~ may be in the form of rods, comprising the anode or plate 2 and the grid or control anode 3. These electrodes should be spaced closer together than any other pair in order that the break-downv potential between them be much less than between any other pair. side after the upper assembly has been completed 50 A semi-cylindrical and coated conductive sheet '4 with its support 5 constitute the cathode of ‘this and tested. Pins I2 normally limit the motion relay or gaseous discharge tube. This relay is of the armature slug M- against downward motion represented in the schematic circuit diagrams of from its central position, as illustrated, due to the Figs. 1, 2, 6 and 13 by reference numeral I and conical shoulder on the head liI. Armature AI may move upwardly a distance equal to the the three electrodes 2, 3 and 4 thereof as P,'G and K, respectively. The envelope of relay tube length of the post shown just below the head 4i. I encloses the electrodes in a gaseous atmosphere However, when the projectile which carries the manner that they may be inserted from the out described fuse is given an initial acceleration due to ?ring, as from a gun, the force of inertia on which may comprise an inert gas such as helium, argon, nitrogen, mercury vapor or a suitable slug I4 will tend to spread apart spring pins I2 60 mixture thereof. While the drawing of Fig.3 is by reason of the cam action of head ill, and the not exactly to scale, it, together with Fig. 4, illus slug will move downwardly to a limiting position trates the order of magnitude of curvatures of the de?ned by the backing plate 39. electrodes which have been determined after ex Included in the lower assembly is a cylindrical tensive experiment ‘to meet the unusual require lower casing I'i which, for example, may be made ments of such a relay for the described purpose. of aluminum and formed to include several cav The various engineering requirements involved in ities. The upper cavity 29 is shaped to accommo the design of such a tube include consideration date, in a preferred embodiment of the invention, of the ignition voltage, pre-ignition ‘current, two timing condensers which are designated in cathode current density and differential ?eld the circuit diagrams of Figs. 1, 2, 6 and 13 by gradient necessary for correct operation at a reference characters C1 and C2. These timing given gas pressure. Also, the stress requirements condensers may preferably be of the impregnated of initial acceleration of the order of 1500 grave paper wound variety, and in any event should be of a high grade and accurate type but small in ‘dimensions. it-ies as well as extreme compactness ‘must enter into ‘the design for a tube to be used in high‘ve The cavity 30 is formed to include 75 locity shells. For low velocity purposes, "as ‘in 2,404,553 , the case of Fig. 8, the design is not so critical, and commercially available tubes may be em ployed. Furthermore, the more lenient require ments of fuses in which’ setback is absent would alternatively permit the use of an electrochemical V _ 10 greater than the spring pressure of the Contact leaves 20 and 2|. 7 s > > ' -7 ' As soon as contacts 20, 25 and 2 l, 22 are closed the timing action of" the fuse is set into opera: tion. The circuit connections may then be il-f type of relay adapted to trigger at a predeter lustrated by Fig. 1 or Fig. 2 under the conditions mined control current in place of the equivalent when switches 54 to 59, inclusive, are in the dis gaseous discharge relay. charge position represented by contacts marked Metal cap 9 secured to insulating form 8 by d. Thus when the timing circuits'are connect screw I9 completes the entire assembly which 10 ed in this discharge position the cletonaktihg'dgé:i presents three external metal surfaces, 9, II and vice will be actuated at theexpiration'of the I6—l1, insulated and spaced from each other time represented by the‘ predeterminedcharge and which form three external electrodes stored in the timing condensers as' described through which charging potentials may pass, previously in connection with Figs.‘ 1 and '2‘. ' when such contact electrodes are placed in suit An important advantage of this invention re-' able conlnection with corresponding charging sides in that it makes possible the complete test-1 contacts arranged to cooperate therewith, as de ing of all the operating portions‘ of" the» fuse scribed in connection with Fig. 1. under normal operating conditions. This re; The mechanical operation of the fuse struc sults from the fact that the, weighto-f 'slugM' ture illustrated in Figs. 3, 4 and 5 is as follows: 20 is such ‘that when the‘fuse is‘ stood upright; the ' When a suitable electric current is passed spring-tension, if ‘any, of the switch 'leaves'_;is through ?eld winding l5 the resulting magnetic overcome, and contacts 22, 25 close, providing of , flux tends to draw armature slug It upward to course that spring pins It have not been’ in; ward the head of the fuse until it subtends the serted. Thus, before pins it are inserted,"both greatest ?ux density. This motion displaces 25 the timing and the ignition ‘circuits and the the spring switch leaves 28 and 25 away from their normal central position as shown. In the normal or central position the switch leaves do not make connection with any other contacts. This magnetically actuated motion of leaves 20 and 2| brings them into connection with the upper ?xed contacts 24 and 23, respectively, and this connection is maintained only so long as relay l5 may readily be tested. , _ " " The system illustrated schematically'in ,Figé‘?, represents a complete time ' fuse. and ‘ fusesetting apparatus which ' broadly speaking is similar ‘to that of Fig. 1. Howevergthe‘ system of Fig.5 is different in certain respectswand includes ad,’ vantages additional to those :of Fig.‘ 1.. The‘ system of Fig. 6 is adaptedmoreparticularlyto I the actuating current passes through the ?eld the requirements for time fuses and setting ,aps' . coils l5. The time of this contact may be called 35 paratus for aircraft bombs'andj?ares which it the “charging time” and during this period the is desired to ignite at'a predetermined. time electrical connections are those of Figs. 1 and 2 aftertheir release from the aircraft; 'It is' usu-" when the switches 58 to 59, inclusive, are in the charging position indicated by the contacts des ally desirable to initiatethe timing ‘automatically ignated 0. At this time the potentials necessary to charge the timing condenser Ci of Fig. 1, and condensers C1 and C2 of Fig. 2, and the ignition condensers C3 of both ?gures are applied to those condensers through suitable connections stalled in the aircraft. This characteristic is, also desirable in a fusedesigned for anti-sub-i to electrodes 9, II and l6-—ll on the surface of 45 at the instant of separation of the bomb .01‘ ?are and its fuse from the fusesetting apparatus in‘; marine depth (:harges'wherethe desired depth for detonation is predetermined in terms of 'its' time rate of sinking. . ' " ' .‘ , , 7 the fuse. When the charging is completed and As indicated previously herein an unusual‘ ad the ?ow of this actuating current is stopped, vantage of the presentinvention resides inlthe contact springs 20 and 2| will return to their fact that itmakes. possible the setting of‘ each normal position, as shown. In this position the timeffuserindividually the instant beforev itis external contacts or electrodes 9, II and IB-l'l 50 released from the. aircraft. This enablesthe are completely disconnected from the circuits detonation of the bomb or ?aretoibe jeifected of the fuse, whereby the charges stored in the at any desired altitude or at theexpiration of condensers will be unaffected by surface moisture any desired time interval after release from the or other conditions which might tend to short aircraft regardless of the altituderof the aircraft circuit the external electrodes, and the accu 55 itself at the time ofv release. In previously‘ known racy of the timing will be assured. time fuses for aircraft use it has been neces-' Spring pins l2 normally limit the motion of sary to estimatein advance the probable altié the armature slug it against downward move tude of the aircraft at the time of releaseof all ment from its normal central position shown, of the bombs or ?ares because it was necessary due to the conical shoulder on the lower portion 60 to set the timing of the fuses before the bombs of the head 4i. However, when the shell is sub or ?ares were loaded in the aircraft. 'Once’ the jected to setback in the initial acceleration re ?ares or bombs had thus been loaded in‘the air-L sulting through its discharge, as from a gun, craft it was impossible thereafter to change the the force of inertia on slug ill will urge apart setting of the'timing mechanismvrithout first 65 the spring pins 12 by cam action, and the slug landing the aircraft, _ > a . 7 v} Q will move downward as previously described to‘ In connection 'with- the systemof Fig. 6v (and a position limited by the backing plate as. This with Fig. 13)' it is to be understood that an'ap-v- ' motion carries spring switch leaves 29 and 2| propriate charging cable harness will be em into connection with lower ?xed contacts 25 ployed to ‘connect the fusesetting apparatus with and 22, respectively. Furthermore, the contacts 70 the several bombs or ?ares stored in the bomb will be locked in this position even after the requires bay of the merely aircraft. the ‘necessary, Generallyconnecting-"wires speaking, setback acceleration has ceased because the upper contour of head lil after passing spring grouped into a cable running from the terminals pins 12 is unable to spread pins l2 by reason ‘it-13 inclusive of Fig. 6 and'dividedinto as many of the fact that the spring pressure thereof is 75 electrically parallel branches as there are fuses 2,18.104.22.168,L5 53 11 toibe set. ,At the terminal of each branch is an appropriate charging plug which 'is placed in electrical contact with the charge electrodes of 12 of the knob 6!. However, it is evident that whether this mechanism of ‘scale separation be used or whether the several scales be inscribed on one meter face, economy of space and ease each individual fuse. Such plugs are described in more detail in connection with ‘the fuse struc 5 of accurate setting by the multiplication of ef fective scale lengths will be effected by the divi .tllres illustrated in Figs. _8 to 12. sion of the fusesetting control Rs into several Referring now to Fig. 6. above terminals 1043 ranges, each of which produces a full‘scalemeter are shown the circuit connections of a ,fuseset de?ection, thus allowing rapid setting of ,each ting apparatus suitable for use in aircraft and which’ in itself may be compact and rapidly ad 10 fuse in terms of time. system above described provides an ad justed to set the fuses connected thereto individ justable voltage E1 to the charging cable harness ually for any desired time delay of detonation. connection ‘1’ l, a ?xed voltage IE2 at connection 1.3 This setting apparatus is adjustable by means for charging the ignition storage condenser Q3 of of a multiple switch shaft 62 ‘having a plurality of positions arranged to subdivide the setting 15 the fuse, and a zero or ground return E0 ‘at con nection if. A fourth connection 10 is provided voltages, corresponding to the total range of time which is connected by a jumper in the charging intervals over which the fuse is operable, into a cable plug to the zero potential lead 12. number of contiguous scale-ranges. A pointer The circuit arrangement and circuit elements or knob Bl indicates the scale-range in opera tion. ;In the drawing, three such scale-ranges are illustrated and labeled A, B and 0 respec tively, and these cover the decade time intervals of the time fuse apparatus are similar to that of Fig. 1 except for certain improvements now to be described. The components of the fuse com prise as before, preferably timing condensers C1 and C2 of the accurate paper-insulated variety, The poles S2 and S3 of switch 62 are connected so as to progressively subtend three adjacent in 25 an ignition energy storage condenser C3 prefer ably of the electrolytic type, a detonator or ignie tervals of voltage across a bleeder resistance tion wire All, gaseous discharge tube I, ahigh comprising resistors R8, R9, R10 and R11. The resistance leakage resistor R1 and a-limiting re potentials along this bleeder are sustained by current source 69, here represented as a battery sistor of medium ‘resistance value R2 later to be but which may comprise any suitable source of 30 described. The timing condensers may be of 0.5 direct current as explained in connection with microfarad and the ignition condenser of about Fig. 4. This current source has three progres 20 microfarads capacity. A structure suitable for sively higher potential taps E4, E5 and E6. A such a fuse circuit, together with a charging plug potentiometer R3 is connected across switch poles therefor, is described in connection with Figs. 8 to S2 and S3 and the adjustable slider on this po 35 12 inclusive. tentiometer is connected as shown through The operation of the fuse represented in Fig. ‘6 charging contact ‘H to charging electrode E1 of is similar to that of the fuse represented in‘ Fig. 1, the fuse. Thus there are three adjacent ranges it being recalled that the fuse of Fig. 1 is especial of voltage which can be delivered to the fuse, l-y adapted for use in connection with a shell of these ranges being selectable by the switches S2 40 comparatively high velocity whereas that of Fig. and S3, and within each range the Voltage may 6 is more especially adapted for-use in connection be subdivided by potentiometer ‘R3. Switch S5 with missiles of low velocity such as aircraft is ‘provided. to conserve the current when the bombs and ?ares. fusesetter is not in use. During the time when the fuse of Fig. 6 is con The movement of a voltmeter 68 is connected 4.) nected to the setting contacts 18-13 the condenser so as ,to indicate the vsubdivision of the interval C2 is shortcircuited by a shortcircuiting connec of ,10-20, 20-30, and 30-40 seconds, respectively. which the adjustable tab of potentiometer ‘R3 tion or jumper between contacts Hand ‘12. This jumper may be included in the wiring of _a suit of this meter movement may be produced by the able charging harness which would ‘intercon voltage available in each range, providing the 50 nect the fusesetting apparatus and the several subtends. CQnseqllently, a full scale de?ection series multiplier resistance connected in circuit with themeter is selected to yield full scale de fuses as already described. While condenser G2 is shortcircuited no voltage is impressed across ?ection for the total voltage in each interval. electrodes G—K of tube l and no discharge of This selection of correct meter multiplier resist that tube can occur. However, due to the‘large 5.5 ance is effected by switch pole S1 which succes value of timing resistance R1 this external short sivelyintroduces multiplier resistances R5, R6 circuit does not prevent the adjustable tap of and ‘R7 automatically with the turning of shaft potentiometer R3 from maintaining a preselected 62 by manual selector knob 6|. voltage on timing condenser 01. Consequently Provision is made to check the total voltage across the bleeder by displacement of switch S4 60 when the bomb or flare containing this fuse is dropped the resultant breaking of the connections to ‘the alternative position from that illustrated. ' at contacts ‘lit-l3 removes the shortcircuit from The resulting connection introduces meter mul C2 and thereby initiates the exponential rise of tiplier R13 in circuit with the meter so that full potential in condenser 02, which comprises the scale meter deflection then corresponds to the peak voltage across the bleeder. The series reg 65 timing process as described in connection with vFig. ‘Z. ulation rheostat R12 allows adjustment of the The value of resistance R2 being negligible in bleeder "voltage to a predetermined operating value. comparison with resistance R1 the rising poten graduations of one second each, may be carried on a plurality of cylindrically polygonal faces so phased with the range positions of shaft 62 that only ‘the corresponding scale presents itself on the ‘face of the instrument at any given setting 75 between electrodes G and K of tube I. The sub sequent discharge will be transferred as before tial in condenser C2 will at the predetermined As a convenience in reading the meter sepa rate scales 64, 65 and 66, each subdivided in 1-0 70 time reach the breakdown potential of the path described, by relay action through the discharge path of the tube to the power electrodes P-K, thereby actuating the detonation by heating ig 2,404,558 13 niter M with the discharge of the energy stored in ignition condenser C3. , 14 ” increasingly larger corresponding uncertainty in the exact time of ignition. The mechanical construction of a time fuse Limiting resistor R2 may be connected in se ries with a control electrode G to insure that the ?nal discharge characteristic of the tube I will be identical with those measured during the test having various safety and control features, allrin accordance with the present invention, is illus and inspection operations of manufacture. This precaution derives fhom the discovery that any discharge within the cold cathode type of tube 8-12, inclusive. It is to be understood thatv the fuse mechanism in these ?gures may include, for example, the time fuse circuit illustrated in Fig. 6, trated together with certain modi?cations in Figs. ' 7 such as tube i which exceeds certain minute 10 or in Fig. 13. This structure, with its modi?ca values of current density will probably alter the characteristics of the tube for its next discharge. tions, was originally designedas a fusejfor air craft ?ares and bombs, but it is also applicable Thus without some means for compensating for to other uses, as will occur to those skilled in the ' such alteration of characteristics the mere test Referring ?rst to Figs. 8 and 9, a cylindrical ing of the circuits including such a gas discharge 15 fuse body ,I ll is shown to be closed at its upper tube may change the characteristics thereof so end by a head bushing l l 8 intowhich is threaded that when it is thereafter employed for the in an arming vane switch casing 18. A base I I9 for tended purpose it will not operate according to the fuse body supports an adaptor I20 bearing the characteristics observed during the test. art. Furthermore, since the value of ignition poten tial is a function of the pre-breakdown control electrode current any series limiting resistor, such as must be used in manufacturing inspection to prevent alteration of the discharge potential characteristics will change the exact required voltage at which the rising potential will ignite the tube. For this reason resistor R2, which in the embodiment described Was of 10,000 ohms, is . , ' , . external threads i2l provided to engage the bomb ' forging or ?are body as the case may ‘be. .A small propeller or air vane 14, here represented as including two vanes, is secured to bushing 15 which is journaled axially in casing 18 ,so that hearing balls 1'! receive the thrust of air pressure on vanev T4. Rotation of vane 14 due'to the free ' fall of the bomb or ?are to the nose of which it is attached rotates a driving spur gear 19 which is secured to bushing 75. ' . permanently incorporated in the fuse both for Axially threaded in the bushing 15 is a sleeve manufacturing tests and for ?nal operation so 30 49 which is integral with a driven gear'80. This that the behavior of the tube will be identical driven gear differs by one tooth from driving under both circumstances. Such resistor should spur gear 19. Pinion gear‘ 8| engages both of not be incorporated in the plate electrode or ig nition circuit as it would limit the detonating cur gears 1'9 and 80 and is arranged to revolve freely a ?xed axis. Thus the rotation of bushing However, the discharge potentials of the 35 on 75 will slowly revolve screw sleeve 49 by reason rent. plate-to-cathode (P-K) path obtained without and with such a limiting resistor in the control circuit do not differ sufliciently to be of signi? of the epicyclic gear action resulting from" the gear train just described. Since this screw sleeve , £59 is threaded into bushing 15, as shown, the ro cance, nor does the presence of this. limiting re 40 tation of the sleeve will progressively move the sistor in any way affect the accuracy of timing sleeve downward. 7 V ' because the initiation of discharge is the sole , Secured to sleeve .49 is an insulating stud 82 to function of the control electrode due to the fact which is secured contact disk 83 and springebacks that the potential which is supplied to the ig .ing washer 84. The downward motion of sleeve nition energy condenser C3 is intentionally in d9 above described will therefore progressively adequate to produce discharge across the dis carry the contact disk 83 downward until, after charge path P—K without aid from the trigger a predetermined number of revolutions of the . discharge effective between electrodes G—-K. sleeve, contact screws 35 and 86 will be connect The graph illustrated in Fig. '7 represents the ed together by contact disk 83. Contact screws relation between the charging voltage (E1) stored 50 85 and B6 are insulated from base plate 81 by in timing condenser C1 and the time required to washers 88. These contact screws are connected trigger the discharge path G-K. of tube I in Fig. in the ignition circuit preferably in series with 6. This curve is of course exactly representative the igniter or detonator resistance so that it is only of a certain time fuse circuit with certain impossible for detonation to take place until the components as employed in the measurements 55 circuit through these contact screws is closed. from which the curve of Fig. 7 is derived. How This arrangement, which may be termed an arm ever, it may be taken as generally representative ing switch, acts as a safety device to prevent pre of the relations which may be expected from a mature detonation and to allow detonation only fuse circuit of the type described and indicates after the air vanes have turned through several the order of magnitude of the charging voltages 60 hundred revolutions, for example. This switch is required to be impressed on condenser C1. This indicated in Fig. 13 by reference character S14; curve of Fig, 7 indicates that due to the exponen and it is to be understood that a similar switch‘ tial nature of the time-voltage relation, the suc may be inserted in the circuit of Fig. .6. It will cessive decade time ranges corresponding to the be obvious that the motion of sleeve 49 may be positions A, B and. C of the range selector knob made to engage any suitable switching device at 6| in Fig. 6 will subtend decreasing ranges of the'predetermined'nuniber of vane revolutions, voltage. and that this switching operation may comprise It is also to be noted in connection with Fig, 7 the complete electrical disconnection or short that as the slope of the curve becomes more ?at eircuiting, or both, ,of ignition device I23 (Fig. the statistical mean deviations of fuse timing op~ 7 0 .8). It will be seen that when this safety or arm erations from the preselected values may be ex ing switch is open detonation by actuation of the pected to increase due to the consequence that a ignition circuit cannot occur under any circum given uncertainty, either in the ignition voltage stances. and also that it cannot occur until, by of the tube or in the constancy of the voltage operation of the air vane mechanism, the bomb supply to the setting apparatus, will subtend an or ?are ‘carrying this air vane has dropped a suf 2,404,553 15 16 ficient distance to e?ect electrical connection described ejection of the charging plug discon across contacts 85 and 86. Prior to release of the fuse from the aircraft, vanes ‘I4 are prevented from rotation by stop nects internally within the fuse structure all con nections from the charging receptacle contacts to the circuits of the fuse, thus preventing rain arm ‘I6, secured to bushing ‘I5, which is locked or secured to bracket 89 ai?xed to the fuse body I IT. A so-called “arming wire” 9| locks together stop ‘IE and bracket 89 by passing through suit ternal contact surfaces, necessarily exposed after ejection of the charging plug, from electrically or moisture which may accumulate on the ex affecting operation of the fuse in any manner. A so-called “shipping wire” 90 and tag H5 able holes therein. When it is desired to release the bomb 0r ?are from the aircraft, arming wire 10 attached thereto are provided as an additional safety feature by threading wire 9a through the BI is withdrawn from the bracket and stopped, plunger and bushings 92, I33 as well as through either manually, or by reason of the fact that one stop and bracket ‘It, 89. This shipping wire would end of the wire 9| has been secured to the struc be removed after insertion of the arming wire at ture of the aircraft from which the fuse is 15 the time the bomb or ?are is loaded into the air dropped. In order to prevent fouling of the charging cable harness and at the same time to provide certain switching facilities desirable to perform at the instant of release of the fuse, an ejection ‘plunger 92 is provided to slide through bushing 93 (Fig. 8) . Secured to the opposite side of the fuse body III is an insulating bushing I09 carry ing suitable contacts IIlS (this bushing and con tacts being formed as a receptacle) to which may be secured connecting wires such as 9'! and 98 connecting with the appropriate elements of the timing circuit. A spring 9t acting against an insulating plate 95 on plunger 58 tends to urge the plunger through the receptacle to press against charging plug IUI which terminates the charging cable I02. Spring 94 should be of suf ?cient strength to insure, when released, the elec tion of charging plug I8 I . As will be observed from the drawings, arm ing wire 9| when in position is arranged not only to lock the air vane from revolving but also to craft. The remaining components of the fuse and its mechanism are housed in the lower portion of the cylindrical fuse body II'I. Casing I24 en closes the several electrostatic condensers such as C1, C2 and C3 of Figs. 6 and 13, and elements I I 4 and I25 comprise a suitable gaseous discharge tube and its socket. As previously indicated, the requirements for a gaseous discharge tube suitable for use in connection with aircraft bombs and ?ares are not so exacting as those required. for use in high velocity shells and therefore the relay tube Iii may be of a type commercially available, although the tube illustrated in Figs. 3 and 4 is admirably suited for the purpose. A suitable detonating ignition device I23 is secured to adaptor I25 and .projects into the powder booster cup I22 which screws into adaptor I20. These portions of the fuse may be understood to be similar to corresponding components hereto fore employed in connection with aircraft bombs prevent ejection plunger 92 from moving in the and flares. direction of plug IBI. This result is achieved by Fig. 10 shows a modi?cation of the ejector and providing holes through bushing 93 and plunger switching device shown in Figs. 8 and 9. Here 40 92 through which the arming wire passes. As a the charging plug NH is retained against the consequence of this additional locking feature force of spring~actuated ejection pins I 36 and I31 plunger 92 is unable to move until the instant of (there being as many as required) by the re release of the fuse at which time the withdrawal straining action of arming wire 9| which Passes of arming wire 9| permits plunger 92 to eject through bushing I32 and through plug IIII. With plug IBI and disconnect it from contacts I68, 45 the elements in the relative positions illustrated, ?nally coming to rest against stop shoulder or pins I36 and I3‘! not only make electrical contact head I60. . at the points I43 and I44 respectively of the plug, Secured to plunger 92 is an insulating plate but also make contact at their other ends with 95 which therefore moves with the plunger. This contact leaves I34 and I35. These contact leaves plate carries four (or a different number if re 50 are connected respectively to wires 97 and 98 quired) spring switch leaves I26-I29 which, in the charging position prior to the ejecting action of plunger 92, connect with switch contact points which it is to be understood connect with the cir cuits of the fuse as described in respect to Figs. single pole double-throw switch, whereas the re maining poles may be simply single-throw poles, plug and ring, thus functionally replacing arm ing wire ill of Fig. 10 in locking plug IOI in posi tion until the time of release. Otherwise the combined ejection and switching, mechanism of 8 and 9. I04--I?‘I. These contact points are secured to Upon withdrawal of arming wire 9|, pins I36 an insulating plate I03 which in turn is secured 55 and I 31 are forced to move by springs I48 and to the base H8 of the fuse body by suitable sup M8 which press on the stops I40, I4I secured to porting brackets IIB. This construction facili those pins. This movement will take place to tates assembly of the entire structure. By com ward the left, in the drawings, through guide bining this switch means with the charging plug holes in insulating plates I33 and I42. The re ejection means an additional feature of safety 60 sulting pressure on the charging plug through the and accuracy is provided by enabling the auto contacts I43 and I44 ejects the plug and simulta matic changing of circuit connections at the in neously moves pins I36 and I3‘! out of contact stant the fuse is disconnected from the charging with leaves I34, I 35. These pins thus perform both of the operations of ejection and switching. cable. In certain fuse circuits (see Fig. 13) it is de 65 In Figs. 11 and 12 a further modi?cation is sirable, not only to break but also to make con illustrated in which a retaining ring I46 secured tact at the instant of release of the fuse. For to charging plug HM and having ears, as shown, this purpose a contact point 48 is provided so is arranged to cooperate with brackets I48 and that the associated switch leaf functions as a I 159 shaped to conform with the contour of the as shown. The switch poles and corresponding contacts just described are illustrated at the lower portion of Fig. 13 in a modi?ed embodiment of Fig, 11 may be understood to be similar to that this invention. It is also to be noted that the 75 of Fig. 10. These retaining brackets I48 and I49, 2,404,553 ' 17‘ in their cooperation with the ears of retaining select therangedesired. a ‘PolesVSs and S10 of this » ring I46, are positioned on the fuse body II‘! in switch ‘are >_connecte'd"to introduce an adjustable . potentiometerresistor R3 series with the bleed-> er; resistors‘ in such/a way thatthe ratios of re SiStOrfBB'tO‘ theselectedw values. of the. ?rst bank ofbleedereresistorsRn to R18 and the second bank’ such manner that when the fuse body, as stored in the aircraft, is dropped or released therefrom, the movement of the fuse body will be in a direc tion such as to permit the separation of the fuse body from the charging plug in the manner illus of rbleederiresistorsRré tovRzg will cause potenti olmeteriRg ~tofprovide successive "and predeter trated in Fig. 12 where the arrow below the draw ing represents the direction of movement of the mined rangesof potentia1.> r -. > I fuse body with respect to the plug IIII which re 10 . ‘However, since» the’ .total-lvalu'e. of resistor R3 maynotfbeiconveniently-changed and since it is mains attached to cable I02. Since in the ar rangement of Figs. 11 and 12 the separation'of requiredio subtend ‘different potentials it -fol the fuse from the contacts of the receptacle with‘ lows that the total bleeder resistance forw'di?ier? which it is adapted to make connection, is by a entirangels will change. FThis change inloadjis v sliding motion it is evident that the form of the highly-undesirable:where greateconstancy. in the contacts will differ from that of the contacts in setting ‘voltage- Fig-‘desired, ' and? consequently by Fig. 8, for example, where the contacts of the plug means :of switch-vy-pole S12’ a’ different. parallel are actually inserted into corresponding recep compensatingresistor is introducedfor each set ting; ofqjthe switches S9 and S10. These-parallel tacle contacts. It will be evident from the fore going that any form of receptacle and cooperat ing plug may be employed so long as it be func tionally suited to the purpose. If it be desired to combine the charging cable release arrangement of Figs, 11 and 12 witha switching device controlled by an arming wire,v 20 compensatingfresistors R29 .‘ to» Rs: should be chosenso that-thetotalparalleL resistance load remains A constant.‘ .-No~ actual values. of-these resistpfs are here siren bécause'thermar basal: cinema one 5killed;in the’ at. ‘one. the'cir'r I , cuitl‘cvonditions and other ; constants’ are selected. For example, if the potential source happened to the structure shown in association with spring actuated plunger switch I80 in Fig. 11 may be be of about the value re'quiredfor' thelfirstrangef used. In this arrangement the arming wire ‘91' the ?rst’ resistor in the bankmight‘ be of a very retains spring-actuated switch plunger I5I~with low resistance-value, or’ even: ‘of, ‘zero Valuer; in the bushing I52 by reason of the fact'that'theJ 30 ‘A bleeder resistance connectedvacross thevdi wire is threaded through holes in the bushingand rect-current source 55 and “dividedginto sections; in the plunger. Upon withdrawal of the arming designated R24 and Rzsfinclusive, is associated wire, switch I80 is actuated by the springwithin with.v switch S11 soars to provideselection of. a it to effect any necessary switching operation, and number‘ of vpredetermined polarizing potentials may be understood to perform any of the switch .for the timing circuit of the fuse. .The-advan-j ing operations which are performed by ‘ the tage of using'these polarizing potentials will be switches described in Figs. 8, 9 and 10, forex ample. The shipping wire 90 is included for- the described in more detail in connection with Fig. reason mentioned in connection with Fig. 8. ' ' The system of Fig. 13 represents the preferred embodiment of my invention, and includes a time fuse and setting apparatus therefor, both espe cially useful in connection with aircraft bombs and ?ares, The circuit arrangement of the time fuse of Fig. 13 is essentially the same as that of Fig. 6, most of the differences being in the fuse setting apparatus, the connections between that apparatus and the fuse, and the incorporated 14; >The's'ource of direct currentfromwhich the necessary potentials are derived is here rep-' resented as a battery 69', andthis source is pro- ' tected by safety fuses I64and I65 as well as by‘ an on-o? switch S13. ' . ~ . » e In order to maintain the output potentialsof the current source within exceedinglyclose lim ‘ its without the use of metering equipment either too delicate or too heavy for general aircraft use, a ‘potential-regulating‘ systemv including two-elec trode gaseous discharge tub‘eQT1 a milliammeter switching arrangements. With this fusesetting I63 and'rheostat R12 maybe employedv and vcon apparatus it is possible for the bombardier or 50 necte'd, as shown". ,In this regulatingisystem ad-' operator of the device ?rst to select the range in vantage is taken of the'very ?at slope which the which the desired time appears and then quickly current-voltage characteristic of gaseous dis to set another indicator to the exact second of charge tubes display within: certainranges; On that range. Then by throwing a, charging con, the basis of this phenomenon the difference (of 'a' trol, the fuses at that time connected to the ap ‘ ‘fraction of .a volt in several hundred across the paratus will immediately be charged to e?ect detonation at the expiration of the desired num-v ber of seconds following release from the aircraft. This apparatus of Fig. 13 also includes mecha nism by which before the fuses are set the poten tial supply may be checked, and adjusted if neces sary, to make certain that the desired fuse setting will be accurate. The system of Fig. 13 will be seen to be gener ally similar to the system of Fig, 6 and to, include certain features of Fig. 1, but as will become'evi dent it includes many advantages in additionlto those mentioned in connection with Figs. 1 and 6., In this system as illustrated, ?ve potential two electrodes of the tube will correspond to a , change in currentthrough such a discharge tube of suf?cient'magnitude to be easily' observed on an insensitive short scale meter suitable for use in aircraft. For this'reason it is possible to ad' just the potential e?ective across the entire po-. tential-supply bleeder system by adjusting the see ries currentdimitinarheostat.Rm until a prede termined‘ current “is observed in‘ meter I63 to be ?owing through the discharge tube T1. By thus checking, and adjusting if, necessary, the current source immediately before setting the controls of the fusesetting apparatus the accuracy of such setting will be assured. In order ‘to set the fuses ranges are made available to set the‘fuse", each‘ 70 it is necessary. that ‘control knob I59 at'the left range covering 5 seconds. Hence, in the exam of ,Fig..13 be turned to the “armed” position. ple here described, the bombs may be set to det onate at any desired setting from 5 to '30 sec onds after release. To this'end a multiple switch This knob rotates shaft I58 of a multiple switch comprising poles S6—_—Ss so as-to connect the cute put of the fusesetting apparatus through the‘ I6I and. its control knob I62 are provided to 75 charging cable harness to the fuses;themselves.“v 2,464,553‘ 1 , _ , 20 19 When this ‘knob (58 is thrown to the “inert” posi tion the three potential-carrying wires of the main charging cable are shortcircuited and grounded. This feature of the invention operates as "a safety device to prevent accidental charg ing of the timing circuits of the fuses which hap pen then to be‘connected to the charging harness, shown in dotted lines in Fig. 13. In other words the solid line connections indicate the charging arrangement of the fuse circuits and the dotted line connections indicate the discharge or timing operation connections effected after separation ‘of the fuse from the charging harness, assuming the use of a fuse constructed as in Figs. 8 and-9. As has been described in connection with Figs, 1 and not only thus prevents accidental operation and 6 the timing interval is a function of the ad of the fuse circuits, but also assures 1‘Ihat when the fusesetting operation is commenced the con 10 justable potential E1, and since precautions-have densers in the fuse circuits will receive’ their pre selected'charges when in ‘a completely discharged been taken by means of tube T1, rheostat R-rztand meter i?3 to regulate the effective, potentialLirn-l pressed on the charging circuit'j of they setting apparatus, it is possible to calibrate directly‘ in ‘ This_'~_“armed'-’inert”‘ ‘control is also especially valuable-in aircraft operation during’ warfare be 15 seconds the dial associated with dial pointer ‘IE6 condition: ‘ ' cause its use enables the bombardier instantly to discharge all‘ the timing circuits in the bomb f'u'se'lshaboard his aircraft, so that in an emergency at the top of Fig. 13, in terms of several ranges‘ of time. This dial pointer which‘ controls the slider of potentiometer Ra‘lcorresponds in general to the meter pointer 61 of/Fig. 6, and it maybe the bombs, may be jettisoned over friendly‘ ter ritory without being detonated. The connections, 20 moved by any convenient means such'as' knob below the double dash-dot lines, to the duplicate but unlettered terminals beneath terminals E2 to The operation of the'fuse and setting, apparel En are intended to represent all the parallel tus therefor of Fig. 13 is as follows: In‘the fuse branches of the charging harness connecting to circuits of this system not only are timing con all of the time fuses and bombs stored in the-air denser C1 and ignition condenser Ca ‘initially craft. To'simplify the drawings the duplicate charged, but timing condenser C2 is also given an I51.‘ fuses are'not shown. - ‘As shown in the drawings, selector switches S9 and S10, which‘in this instance make available ?ve ' . . ' ‘ initial polarizing charge predetermined ‘for, the given range of timinglinvolved, sothatdt will either decrease or increase the amount _of charge time 30 necessary to be transferred from condenser; C1 ranges are interconnected- in uni-control arrange through resistor R1 before the potential across ment by shaft I61 rotatable by the range selector condenser C2 is adequate to, trigger offthe relay knob I62. This knob is, as shown, arranged with tube 1. rThis polarization of the condenser C2, in different potential’ and corresponding an index to indicate the five different time ranges which a charge is builtrrup to the discharge orv from A to E inclusive. On this same shaft IBI is 35 relay point, may be either positive___or, negative arranged the pole of switch S11 which connects to the various sections R24—R2s of the bleeder re sistance above referred to from which are derived with respect to the common potential terminal 107 of C1 and C2. In either case ‘however itkmust not exceed thev ignition, voltage of the tube , T1.‘ the polarizing potentials, which may be applied between G and KY thereof if the tube, is to. be pre to a condenser in the timing circuit of the fuze 40 vented from discharging prematurely. .The, in order to extend the total timing range pos values of the mentioned circuit. elements. maybe. sible with a given value of condenser capacity. the same as those given the description of. Switch S12, also connected to the same shaft 6! so Figs. 1 and 6. .. .. . .. as to operate simultaneously with the other The timing operation is initiated when switch switches, connects with the same number of con 45 pole I28 completes thetransfer path between con-. tact points‘ as do the other four switches just re densers C1 and C2 by. connectingv with contact. ferred to.‘ The bank of resistors Rae-$2.33 there point 48 at the instant of .release of the fuse. shown as connected respectively to the different Subsequently, and when the safety airl- vane points of this switch and connected in common switch- S14 (comprising contact elements. 83,05, 50 to the positive terminal of the potential supply and 86> of Fig. 8). has closed, adequate chargewill system is introduced as a compensator in order to be added to- the polarizing-charge in’ condenser keep the load on the potential supply source con C2, whether that polarizingcharge be negative‘ or stant under the varying conditions of load inci positive, to'cumulatively ionize the discharge-path dent to selection of the different points on the G--K of relay tube I, ‘This will initiate the relay 55 range selector. The compensating resistors R29— action in tube 1 and release the energy‘ of ignition R33 therefore must be chosen with this purpose in condenser C3 to ignite detonator' 44; The action mind and the resistance values thereof required of the limiting resistor R2 is the same as in the under any particular circuit conditions may be circuit illustrated in Fig.6, and its-value may calculated by one skilled in the art. Arrows [IQ-H3 inclusive near the bottom of Fig. 13 represent the pins or connectors of a charging plug, and blocks 91-100 inclusive repre sent the corresponding contacts on the fuse‘. It will be noted that these charging plug contact pins, together with the corresponding contacts and the switch elements l26-—|29 and NHL-I01 and 4.8 correspond to the elements similarly desig nated in the assembly shown in Figs. 8 and 9. Prior to release of the fuse and to ejection or dis connection of the charging plug therefrom the 70 circuit is that of the con?guration shown in solid lines in the drawing. However, on withdrawal of likewise be 10,000 ohms. ' " - ' By reference'to the curves of Fig. 14 the effect‘ of the several different ‘polarizing voltages (poi tential‘s) employed to charge condenser C2‘ may be seen; as well as' the relation between the charging voltage E1 of condenser C1 aiod'thev re'-' sulting timing of the fuse. These voltages are'sim ilar to the voltages which would be produced by measuring 'themtime-voltage. fuse characteristics‘ fora series of discharge‘ wtubes having progres sively higher ignition potentials. The five voltage andntime ranges marked A—E Fig.13v are here represented ‘by the same letters. These ?ve curves show the rangesinrseconds which were s‘e-' the arming wire 9! either switch plate 95 (Fig. 8) or its equivalent switch plunger I51 (Fig. 11) cured, with the-_circuit as shown inFigI when moves the switch poles l26—l29 into the positions 75 employing elements as described in connection 2,404,553? therewith, with two di?erent variables. The ?rst variable is the different polarizing voltages E3 and the second is the different chargingv or tim ing voltages E1 represented by the ordinates on the graph. As pointed out in connection with Fig. 13 the selector of the different polarizing po tentials results from moving switch II, and the selection of the different potential ranges is ef fected by switches S9 and S10, whereas the ?ne selection of potential within each range is ef fected by potentiometer R3. The different polar izing potentials are applied to timing condensers 22‘1 and meals for 'tintroducingseparate electrical charges simultaneously in all three condensers. 4. In an electrical time fuse, ‘the combinationv which comprises‘ a timing circuit’ including- two , capacitors and at least one’ resistor, a ‘separate ignition circuit including a third capacitor and an, ignition element, a gaseous discharge tube having‘three electrodes and adischarge-pa‘th'beé. I, tween the ?rst and second of saidv electrodes, the 10 third electrode being electrically associated with said path, connections including said ?rst and second electrodes in series in said ignition'circuit and connections between said ?rst and’ third elec trodes and said timing circuit. 5. In an electrical time fuse the combination vertical line is the voltage simultaneously applied 15 which comprises a gaseous discharge tube in to timing condenser C1. All of the voltages, 0r cluding three electrodes, a limiting resistance, a potentials, represented in Fig. 14 were employed timing circuit including a timing resistance and successfully in connection with a discharge tube two condensers connected on ‘one side each to as represented in Figs. 3, 4 and 8. a common terminal and to a ?rst electrode of The consequence of the series of progressive 20 said tube, and connected on the other side through polarizations shown in Fig. 14: is to permit a sub said timing resistance to each other, one termi stantially wider range of time intervals to be nal of said timing resistance being connected covered with a single set of component circuit through said limiting resistance to a second elec values and also improved accuracy throughout trode of said tube, an ignition circuitincluding all of the ranges due to the steeper slope of the an ignition element and an ignition condenser, curve obtained by subdivision of the total possible said ignition condenser being connected on one time range into a group of appropriately polar side to said common terminal and being con ized ranges. nected on the other side through said ignition ele It has already been explained that the electric ment to a third electrode of said tube. time fuses and setting apparatus therefore above 6. In an electrical time fuse, the combination described were designed for use especially with which comprises a gaseous discharge tube in aircraft bombs and flares and high velocity shells. cluding three electrodes, a limiting resistance, a However, it will be evident to those skilled in the timing circuit including a timing resistance and art that the several features of my invention will have a wide range of applicability wherever tim 35 two condensers connected on one side each to a‘ common charging terminal and to ya ?rst elec ing circuits, or ignition circuits are required, or trode of said tube and connected on the other wherever charging apparatus or electrical fuse side through said timing resistance to each other, setting apparatus is employed. said timing resistance having two terminals, one I claim: 1. In an electrical time fuse, the combination 40 terminal of said timing resistance being con nected through said limiting resistance to a sec of a timing circuit, an ignition circuit and a gase ond electrode of said tube, said limiting resist ous discharge tube having a discharge path con ance having a greatly lower value than that of nected effectively in common to said circuits, said said timing resistance, and the other terminal of timing circuit including a ?rst timing condenser said timing resistance being connected to a sec connected to receive a timing charge, a second 45 ond charging terminal, and an ignition circuit timing condenser connected to receive a polariz including an ignition element and an ignition I ing charge, and a timing resistance connectable condenser, said ignition condenser being connect between said condensers, said ignition circuit in ed on one side to said common charging terminal cluding an ignition condenser connected to re and being connected on the other side through ceive an ignition charge which is independent of 50 saliod ignition element to a third electrode of said the charges in said ?rst and second condensers, tu e. and an ignition element connected to receive ig 7. In an electronic time fuse, the combination nition energy from said ignition condenser. which comprises, a gaseous discharge tube in 2. In an electrical time fuse, the combination cluding a cathode, an anode and a control elec of three condensers, an ignition element and a 55 trode, a discharge path within said tube between plurality of coupling means, connections for cou said cathode and anode, a timing circuit including pling two of said condensers by one of said cou a timing condenser and a timing resistance con pling means in a timing circuit whereby said connected between said cathode and control elec densers are connected to receive separate elec trode, an ignition circuit including an ignition trical charges, coupling means connected between 60 condenser and a detonating device connected in one of said two condensers and an ignition circuit, series between said cathode and anode, and con said ignition circuit including the third condenser nections through which said condensers may be and said ignition element, and means for con charged, said timing and ignition circuits being necting said third condenser to receive an elec electrically isolated from each other except 65 trical charge independent of the charges in said through said discharge path within the tube. two condensers. 8. In an electronic time fuse, the combination 3. In an electrical time fuse, the combination which comprises, a gaseous discharge device in of three condensers, an ignition element, a re cluding three electrodes, a discharge path within sistance and a three-electrode gaseous discharge said device associated with said electrodes, altim tube, connections for coupling two of said con C2 and charge the same to those potentials. The voltage range indicated on each curve by the densers by said resistance, one of said two con densers being connected to two electrodes of said tube, an ignition circuit including said ignition element, the third condenser, one of Said two electrodes and the third electrode of said tube, 75 ing circuit including as elements a timing con denser and a timing resistance connected to a ?rst and a second of said electrodes, an ignition circuit including as elements a detonator and an ignition condenser connected to said third 23 2,404,553" electrode and to one of' said ?rst two electrodes, and connections through which said- condensers may- be charged, said timing and ignition circuits being electrically isolated from each other except through said discharge path within the tube. 9. In an electronic time fuse, the combination which comprises, a gaseous discharge device in cluding three electrodes, a discharge path within said device associated with said‘ electrodes, a tim ing circuit including as elements a timing resist l0 ance and a timing condenser effectively con nected between a ?rst and a second of said elec 24v trodes, an ignition circuit. including‘ as elements a detonator and an ignition‘ condenser effectively connected between said third electrode and one of said first two electrodes, said timing condenser being of accurate low loss type and said ignition condenser having a capacity‘ value much greater than that of said timing condenser, and con nections through- which said condensers may be charged, said timing and ignition circuits being electrically isolated from each other except through said discharge path. , NATHANIEL B. WALES, JR. Certi?cate of Correction Patent No. 2,404,553. NATHANIEL B. WALES, JR. July 23, 1946. It is hereby certi?ed that errors appear in the printed speci?cation of the above numbered patent requiring correction as follows: Column 5, line 65, for “?xed” read ?red; column 8, line 11, before “stages” insert last; column 13, line 8, for “fhom” read from; column 19, line 40, for “fuze” read fuse; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 15th day of October, A. D. 1946. [M] LESLIE FRAZER. First Assistant Commissioner of Patents. Certi?cate of Correction Patent No. 2,404,553. NATHANIEL B. WALES, JR. July 23, 1946. It is hereby certi?ed that errors appear in the printed speci?cation of the above numbered patent requiring correction as follows: Column 5, line 65, for “?xed” read ?red; column 8, line 11, before “stages” insert last; column 13, line 8, for “fhom” read from; column 19, line 40, for ‘ffuze” read fuse; and that the said Letters Patent should be read with these correctlons therein that the same may conform to the record of the case in the Patent O?ice. Signed and sealed this 15th day of October, A. D. 1946. [ml-1 LESLIE FRAZER.’ ' First Assistant Commissioner of Patents.