US2498032A

US2498032A - Thermal circuit breaker

Info

Publication number: US2498032A
Application number: US732268A
Authority: US
Inventors: Albert H Dell; Jules H Sreb
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-03-04
Filing date: 1947-03-04
Publication date: 1950-02-21
Anticipated expiration: 1967-02-21

Description

Feb. 2l, E950 A. H. DELL ET Al. 2,498,032

THERMAL CIRCUIT BREKER Filed Maron 4, 1947 |TO PRIMER INFLUENCE CONTROL 4*- t/ nsj FIG. 2 [3 e, il n BY X22, i5/L4.

ATTORNEY Patented Feb. 21, 1950 Washington,' D. C., assigfnors to the 'United States of America 'as represented by the Secretary of the Navy Applicashun/meh 4, 1947,'seria1-No. 732,268

1 The present invention relates `to circuit breakers and specifically to :those of the type employed in proximity fuzes.

A proximity uze vis a device for detonating an ordnance missile. It comprises electrical control circuits (hereinafter referred to as influence control) which yproduce a signal of suicient strength to fire an electrically ignitable primer when vthe Vmissile comes close to a target. The primer then detonates the missile. In order to prevent undesired detonation as the missile leaves the point from which it is sent, the primer ignition wire is protectively short-circuited at and before the initiation of flight. The short-circuit is removed after the missile has departed a safedistance 4from that point. It is desirable that this short circuit be removed after a predetermined delay following the initiation of missile flight. A shortingn device is placed in shunt with the primer to provide a short circuit. There is an auxiliary device designed to accomplish the removal of this short circuit. 'This auxiliary "unshorting device includes a combustible heatproducing element and has an ignition circuit which is essentially in shunt with the primer, for igniting said element. "This circuit should be removed after ignition has occurred. Toward this end a fusible conducting member is placed in series with the said ignition circuit. Said fusible conductor becomes melted and dispersed, thus removing the ignition circuit from across the primer and allowing the auxiliary unshorting device to accomplish its function of breaking the primer short circuit after the desired delay.

The fusible member is disintegrated as a secondary action, following said combustion ofv the heat source by ignition action of the same battery which energizes the influence control. It is important that excessive drains on that battery and impairment of the `operation of the influence control be prevented and that the circuit through the fusible member and the battery be broken not later than the time that the short circuit is removed from the primer. To keep said circuit closed would interfere with the proper operation of the influence control circuits and drain the battery.

` This object is attained by so arranging the circuits that the battery supplies an initial igniting current to a squib. A squib is a known device comprising an inflammable composition in which an igniting wire is imbedded. The squib is ignited electrically and heat is then produced by its combustion; A metal pin or rod projects out of the I2 Claims. (Cl. LOZ-170.2)

squib. The tip of this rod has soldered to it one end of a springwi-re which lconstitutes the short circuit Yacross the primer. Time delay is lcontrolledby the character of pin material, its shape and its dimensions, as these affect the temperature-time characteristic at the tip of the pin. The result is that the primer is placed in condition -for operation after a predetermined interval following the beginning oi missile flight and interference by the squibwith the normal operationof the -influencelcontrol circuits on the primer is prevented.

It will be seen *that there are provided a squib, a source of energy for igniting the squib, and means responsive to ythe heat of the squib for disconnecting the squib from that source. The squib'and the last-named means are included in the 'improved thermal circuit breaker.

It is an object ci lthis -invention to provide a battery-actuated yarrangement for removing a short fcircu'it from a primer after a predetermined time delay, which arrangement has such operation Vthat does not 'impair the operation of inluence lvcontrol circuits, energized by the same battery, for firing the primer.

In the accompanying drawing-s: y

Eig. l. Ais asi'deview of rthe -housing of the improved--thermalncircuit breaker;l

Fig. '2' is ya diagram of the electrical circuits with which the improved circuit'breaker is asso-'- ciated; l

Fig. 3` is anenlarged sectional view of the circuit breakerfs'howing 'the thermal delay squib and certain electrical connections associated therewith; and r Fig. 4 is anenlarged `sectional view showing details ofthe circuit breaker fastenings.

VReference is now made specifically to Fig. "2',

in which are shown a circuit schematic of a primer', means :whereby the primer is coupled to the influence' control of -a proximity uze, fand means whereby the lprimer remains safe for apredetermined period following the initiation of flight of a missile in which it is installed. A primer Il is coupled to the influence control I6 of a proximity fuze by the conductors |2--I3 and Ill-l5. It will be understood that when the missile comes into proximity to a target the unit I6 has such operation that a relatively heavy current flows through circuit I3, l2, Il, I4, l5. This current is the space current of the electronic output tube oi the unit I6. The circuits of unit i6 are energized byjabattery l1. In order to prevent the primer'from being ignited and from causing detonation of the missile when at a point close to the gun or launcher from which it is 'iii-ed, the primer `is initially short-circuited by a shorter I3. A series combination of the shorter IB and a heat-conducting member |9 having a f fusible terminal is accordingly placed in shunt across primer It is desirablethat the short. ircuitprovided by unit `|8 be removedfrom the primer after a predetermined delay. That objective is accomplished by melting solder that is at the tip ofy heat conducting member I9 ata predetermined .time after the initiation of flight. To this end,

member I9 is secured .in heat-receiving connection to a squib 2|.

battery by the conductor 23-24-|5, and the other lead of *which` is connectedto the battery through conductor 26, a metalioil member forming part of unit 27 and conductor y28---2l. In shunt with the circuit of igniting wire 22 there is placed a low-spin` safety switch 3|.

The operation of :this rcircuit is as follows: When the missileis iired from a gun, say, the riing of the gun causes it to spin. The action of the spin is such as toopen switch 3| and to remove the shortcircuit across the igniting wire The igniting wire' is then unprotected and 22. battery causes arelatively heavy current now therein. This current ignites the thermal delayr After a predeterminable delay, whichL squib 2|. isa function of the structures and the heat evolved, the heat of the squib causes the foil The two conductors 2B, 28 of the circuit of ignition wire 22 are connected to these terminal plates. By means of

screws

44, 44, passing through the tubular rivets, the laminated mat is fixed with the conducting foil 38 insulated'from direct e1ectrica1-contact-with the external case of squib 2| by a thin sheet of mica 3S. When The squib includes an ignitl ing wire 22, one lead of which is connected to the circuit of wire 22 is excited and the internal charge of the squib is ignited, the hot squib supplies heat to the yfoil at a high temperature and the foil is disintegrated thereby and breaks that circuit. lThe thermal destruction of the conducting foil 21T-and the melting of the fusible joint between member I9 and the shorter I8 are delayed by the ytime required forthermal conduction from the hot squib to thefoil 38 and to the fusibler material -such as solder on the tip of the heat conducting y' pin. f

member 21 to disintegrate and thus yseparates igniting wire 22 fromfbattery breaking the electrical connection between that battery and the thermal squib. The lheat produced bythe squib causes solder at thetip of heat conductive pin I9 to melt and, under the influence of mechanical force, in this case force due to spin, ythe short circuit'is removed from across the primer. The primer innow in `condition to respond to a signal from the influence control I6 and the operation of the influence control and fbattery is not impaired by the presence of the former circuit of igniting wire 22.

. Reference is now made specically to Fig. 1. The igniting squib and its associated members are placed in a rear fitting designed to be installed in a fuZe. This tting includes a cylindrical housing 32 of insulating material, a cover 33 closing the iront of the housing, and a metallic base 34. The base is attached atthe rear of the housing with an interposed spacing disc 35 and a washer 36.

The essential elements of the improved circuit breaker are illustrated in Fig. 3. The foil memf ber 21 includes a laminated mat made up of a sheet 38 of foil, sheets 39 of mica and an external Bakelite backing 40. These laminations, to#

said squib to uncouple said source from said squib.'

gether with terminal plates 4 l ,4| are clamped togetherby a pair of spaced

tubular rivets

42, 42.

; After the shorter I8 has been disconnected from the fusible materialen the tip of I9, the shorter may be swung away from the fusible member by the centrifugalk force due to the spinning projectile, as indicated by the arrow in Fig. 2.

- Obviously many modications and variations of the `present invention are possible in the light of the above teachings. It is therefore to` be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim: l V

1. In a proximity fuze, an electrical primer, means for short-circuitingsaid primer, and timedelay means` for disabling said short-circuiting means, said time delay means including a squibya source of energyy for igniting said squib, and means initially operative to couple said source to said squib but responsive to heat conveyed from REFERENCES CITED The following references are of record in the me Vof this patear:

FOREIGN PATENTS Country Date Great Britain May 5, 1919 Number