Патент USA US2411339код для вставки
NOV- 19, 1945- H. J. RoLFEs ET AL FIRING MEANS Filed Dec. 16, 1942 2,4ÍL339 Patented Nov. 19, 1946 ì, ' î - . ,2,411,339y f ` nrimNef MEANS ¿Hans .lay Rolfes, `Melrose,~'1`ransvaal, and Eric. i Clifford’llalliday, Parktown North, Transvaal,- , ' , :il ` ‘- -- , , ' ' ` Union of'South Africa Y , Application December’lfî, 1942„ SerialrNo. 469,244 »- » ' ¿Inïthe Union of South AfricaSeptember 25, 1941 ' ' ' v1 claim. f (C1. 1oz-f2s) This invention relates gto rneansffor safeguarding-,the >electricfigniters of blasting detonators against accidental' ñringçby electric currents or spark discharges produced respectively in, or in earthbut leavesa residual chargein'oneilead or theA other, no` now of currentin the igniter orig-` niters suilicient to `set off’thellatter, will result. As will be -appreciated, the self-inductance the vicinity or”, the iiring means of the igniter> by 5 meanslshould beas smallinïdímensions as is con atmospheric electricity. , , ' Itfisobvious that a possible solution to this problem isto surround thef two electricY leads of sistent with its capability ofproducing the req uisite choking. »effect~ Preferably, therefore, the self-inductance means comprises a continuous- the igniterat a position ia-saferdistanee from the soft iron or other magnetic >ocre in the »form of ñring meansthereof by` an earthed mass of a ma- 10 an oval link, ring, or the like on 'opposite halves terial; whichgwill exhibit ahigh resistance at voltn ages of the magnitude used fqriintentionally nring the igniter and a low resistance» at voltages of Vthe magnitude of the electrostatic charges of which the igniter or blasting circuit leads (en closed in their usual insulated- covering)- are wound»l 1@or the samerea'son, the one leady inthe case vjust-mentioned ‘isvvoundin- the form of a which produce the currents and spark discharges 15 right-hand fhelix and the .f other in a left-hand- aforesaid. , . ‘ One means of obtaining a solution of the prob- . lem 1in the Vmannerjust„indicatedis described in the Yzzo-,pendingPatent,Application No. 455,235, helix, so 'that theinductancesof thetwo helices or coils add> together. ‘ ' vThree embodiments of 4the invention will novv- » lee-described, by'way of example, with reference now Patent 2,403,125, viz. to Aemploy a material 20 to theannexed-drawing, in which: which oñers av complete _ or substan-tially com- Fig. l is-a sectional elevation of a combined-lil plete resistanceto voltages oi the'magnitude used for intentionally ñringthe Vigniter and which, on its» being subjected to voltages of the magnitude termeans andself-inductance means enclosed in afiseparatel casing. Fig-2 is an elevation, partly in section, of a self of, electrostatic Charges caused by atmospheric »25 inductance. means enclosed in a container with a electricity, becomes> locally conductive through ñltel‘ means and detonator. coherer; action along a path or paths permitting ' FigfS is a diagrammatic View of a self-'induct the kpassage therethrough of the high voltage ance means and ñlter meansapplied to a b1ast~ Charge, , ing circuit including a groupof detonators. In any Solution .as above, itis important that 30 Referríngrto 1 the drawing.: thepath' V01“ :paths to earth aiîorded by the mass In the embodimentshownin Fig. «1, the self-im of material (which will hereinafter be referred to dllCÈaTlCe means COIISiStS 0f a Soft-iron oval core as the “ñlter means”) to high voltage charges l which is elongated in the direction of its en should be such as to ensure that as far as possi- ClOSîYlg Coppel' Casing 2 S0 aS 150 fît neatly there ble, the whole charge passes instantaneously to 35 Ín- O‘Il the ODDOSîte halves 0f the @Ore Í, the i11 earth, without leaving any residual charge in one Sllïated igniter leads 3, 4 are WOlmd, the lead 3 lead or the other capable of producing a now of current in the ñring means, e. g. bridge-wire, suf- being Wound on the left-hand half of the core in the fOI‘m 0f a right-hand helíX 3a and the lead 4 ficient to heat the latter to incandescence. It being wound on the right-hand half in the form may not be possible, however, to discharge the 40 of a left-hand helix 4a, so that the inductances whole of the high voltage charge through the íil0f the ’GWG helices add ÈOgei'fhel‘. ter means to earth in every case, e. g. in the case of exceptionally heavy charges or charges of ex- The 10We1’ ends 3b, 4b 0f the leads 3, 4 are 60n nected to the igniter (not shown) and on the side ceptionally high voltage. of the inductive helices 3a, ila remote from these According to the invention we provide, in com.. 45 ends, the leads 3, 4 are bared for a short distance bination with a filter means as aforesaid, a selfet parts 3c, 4° and SU-I‘I'Oul’lded by a ñlter means inductance means located in the igniter or blast5. This means may C0nsîst 0f any earthed mass ing circuit leads between the filter means and the 0f vmaterial which will exhibit, as aforesaid, a igniter or igniters, whereby flow of current high resistance at voltages of the magnitude used caused in one lead or another by atmospheric 50 for intentionally ñring the igniter and a low re electricity is choked back or prevented from vsistance at voltages of the magnitude of the elec reaching or setting off the igniter or igniters, In >trostatic charges induced by atmospheric elec particular, the self-inductance means ensures that, even in cases in which the whole of the high tricity. For example, the filter means 5 may be a coherer plug as described in the co-pending voltage charge does not pass instantaneously to 55 Patent Application No, 455,235, now Patent 2,411,339 4 spectively around the opposite halves of a mag 2,408,125, and the leads 3, 4 may, Whatever be netic ring I9, the one lead I'I being wound as a right-hand helix and the other lead I8 being wound as a 1eft-hand helix. The magnetic core I9 is located in the circuit between the detonators I6 and a filter means 5 shown earthed diagram e. g, discharge points constituted by outwardly matically at 20. While the group of detonators directed teeth 3d, 4d are formed on the bared illustrated is a series-connected group, it is to be parts 3C, 4c of the leads 3, 4 within the filter understood that this filter and self-inductance mass 5 shown in Fig. 1. The casing 2 is closed at the ends by rubber 10 `means may be applied similarly to the circuit of plugs 6, 'I or other sealing means secured in place » a parallel-connected group of detonators. By this use of a self-inductance means in the by crimping 8, 9 at the said ends, and a rubber leads of the blasting circuit, the necessity for sep plug or other sealing means I0 is provided be arate self-inductance means in the leads 2|, 22 tween the ñlter mass 5 and core I. With the means illustrated, high voltage elec 15 (Fig. 3) of the individual detonators I 6 can be the filter means used, be provided or associated with discharge points to promote or facilitate the discharge of the high voltage charge from the leads or either of them into the earthed mass; trostatic charges induced in the lead 3 and/or lead 4 will normally be discharged wholly and in avoided. As the result of experiment it has been deter stantaneously through the discharge points 3d and/or discharge points 4d, and thence through mined that the self-inductance means should the filter mass 5 and the copper casing 2 to earth. of 30 milli-henries or thereabout, i. e. 15 milli henries or thereabout in each lead. preferably have as a minimum a self-inductance Any tendency for the high voltage charge to pass down the lead 3 and/or lead 4 t0 the igniter is If desired, the magnetic core may be made prevented by the choking effect of the inductance flexible to some degree, e. g. by building up lthe means I, 3a and 4a. Thus, even in the case of same from a length or strands of thin soft iron exceptionally heavy charges, or charges of excep 25 wire. tionally high Voltage, which might otherwise It is to be understood that in the appended leave a residual charge in one lead or the other, claim the term “igniter leads” is intended to i11 clude the leads of either an individual igníter or no ñow of current takes place through the lead 3 or 4 to the firing means or bridge-wire suñicient to set off the igniter. In the embodiment illustrated in Fig. 2, the in the leads of a group of series-connected or par 30 ductance means consists of a soft-iron link or core I I around which the leads 3, 4 are wound in the form of right and left hand helices 3a and 4a respectively. The inductance means is located Within an aluminium container I2 which also contains the ñlter means 5 and a detonator I3 (which latter may be of any known type, e. g. instantaneous, Eschbach, or provided With a sep arate igniter and intervening ñexible fuze) . allel-connected igniters, and that by the term “filter means” we signify a ñlter means as here inbefore referred to. We claim: In a blasting unit, electrically-responsive firing means, electric leads serving such means, a pri mary safeguarding means in electrical contact with such leads and electrically inert to normal voltage ñring charge through said leads and fully conductive to current flow from said leads of an The 40 abnormal voltage current throughsaid leads, and ñlter means 5 is adapted to be earthed, e. g. by copper Wire I4 wound round the copper casing of the detonator I3 and also connected if desired, as shown diagrammatically at the points I 5, to the a secondary safeguarding means between the ig nition means and said primary means, said sec ondary means being within the electrical influ ence of the leads and preventing flow through In function, as will 45 said leads to the ignition means of residual or interior of the container I2. be appreciated, the filter and inductance means Shown in Fig. 2 are similar to those described with reference to Fig. 1. Fig. 3 shows the application of the invention to the protection of a group of detonators I6. The 50 leads I‘I, IB of the blasting circuit are wound re like current flow uncontrolled by the primary means, said secondary means including a mag netic core on which the leads are Wound in rela tively-reversed helix form respectively. HANS JAY ROLFES. ERIC CLIFFORD HALLIDAY.