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Патент USA US2404553

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J11 y 23, 1946.
Filed Aug. 6, 1941
6' Sheets-Sheet 1
July 23, 145~
Filed.Aug. 6,. 1941
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July 23, 1946.
Filed Aug. 6, 1941
6 Sheets-‘Sheet 3
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' Filed Aug. 6, 1941
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Juiy 23, 1946.
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Patented July 23, 1946
Nathaniel B. Wales, Jr., New York, N. Y. _ > .
Application August 6, 1941, Serial-No. 405,570"
9 Claims.
(Cl. 102—70.2), ,
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.
" '
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.
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. ’
accuracy of the settings, and the entire equip
By employing low levels of energy in'the tim
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
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
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
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
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. ‘
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
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
ofthe shell begimmer‘sed in water;
output voltage constant under varying loads, and 25
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
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
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,
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
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
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
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
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
greater than the spring pressure of the Contact
leaves 20 and 2|.
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.
' "
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
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
bay of the
the ‘necessary,
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,,L5 53
toibe set. ,At the terminal of each branch is an
appropriate charging plug which 'is placed in
electrical contact with the charge electrodes of
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
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
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
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
niter M with the discharge of the energy stored
in ignition condenser C3.
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.
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
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,
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
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
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
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
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.
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 '
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
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:
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‘
switch S13.
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
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
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
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
potential’ and
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
.. ..
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,
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
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
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
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
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
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
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.
Certi?cate of Correction
Patent No. 2,404,553.
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.
First Assistant Commissioner of Patents.
Certi?cate of Correction
Patent No. 2,404,553.
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.
First Assistant Commissioner of Patents.
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