US2651687A - Alarm switch device - Google Patents

Description

Se t. 8, 1953 F. H. TOWNSEND EIAL 2,651,687 ALARM SWITCH DEVICE Filed Dec. 31, 1951 Inventor FEW/CA H. TOWN SEND flND- HIIRYEY S. HILL M, l Attorneys Patented Sept. 8, 1953 ALARM SWITCH DEVICE Frederick Henry Townsend and Harvey Sydney Hall, Cambridge, England, assignors to Cathodeon Limited, Cambridge, England, a British company Application December 31, 1951, Serial No. 264,302 In Great Britain October 25, 1951 The present invention relates to alarm switch devices for completing electrical circuits in the event of emergencies, more particularly to such devices that comprise an outer casing of frangible material having an elongated tubular form closed at one end, a rod electrode enclosed within said outer casing and extending substantially coaxially of the casing and for substantially the entire length thereof, and a coiled electrode surrounding and spaced from the rod, the two electrodes being adapted to be connected to a suitable electric circuit.

More specifically it is the object of the invention to provide a switch device of this kind which is positive in its operation and more emcient in use.

According to the invention there is provided an alarm switch device of the kind referred. to in which the end of the rod electrode at the closed end of the outer casing is located in a block of insulating material to prevent lateral movement of the rod in the inoperative state of the switch.

Preferably there is provided a second operating spring associated with a contact member electrically connected to the coiled electrode and surrounding and spaced from the rod, together with a co-operating contact member on the rod, the spring being held under load and the arrangement being such that in the event of fracture of the outer casing and consequent removal of the lower half thereof, the loading of the spring is removed to bring about contact between the two contact members.

The detector device may be adapted to cooperate with a separate socket device mounted on a suitable surface or it may be incorporated integrally with a mounting containing appropriate terminals.

In a preferred embodiment the coiled electrode is in the form of a spring held under compression within the outer casing and the second operating spring is mounted in end-to-end relationship with it also under compression so that in the event of fracture of the outer casing by sideways impact, completely removing the lower part of the casing, the coiled electrode moves to remove the compressive loading of the second operating spring whereby the latter expands longitudinally to allow the contact member with which it is associated to contact the co-operating member on the rod electrode.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which show certain specific embodiments thereof by way of non-limiting example and in which 11 Claims. (01. 200-52) Fig. 1 shows a section through one embodiment of switch used in conjunction with a separable mounting socket.

Fig. 2 shows a plan view along the line 22 of Fig. 1.

Fig. 3 shows a plan view along the line 33 of Fig. 1.

Fig. 4 shows a section through a second embodiment showing the incorporation of the device integrally with a mounting containing appropriate terminals.

Fig. 5 shows a plan view of Fig. 4.

Referring to the drawings, l represents the outer casing of the device which is preferably made from glass. The casing is of tubular elongated form closed at the lower end 2. At the upper end is provided a metal flange 3 which acts as a seating for centralising metal mounting t for the metal rod electrode 5. The rod 5 is mounted in the mounting 4 by means of a glass bead 1 which is sealed to the mounting 4 and to the rod.

The other end of the rod 5 is held and located by the member 8 of the insulating material.

Surrounding the rod 5 is a coiled electrode 9 in the form of a spring which bears at one end on a metal cup I0 centralised on the member 8 by tags I I. The base of the cup is apertured at E2 to allow the rod 5 to pass into the aperture It in the member 8. The aperture I2 is sufficiently large to clear the rod 5. At the other end of the spring electrode 9 is a further cup I4 having shoulders I 5 preventing inward movement of the electrode 9. The cup I4 also has an aperture [6 suiiiciently large to clear the rod 5.

The cup I4 is accommodated within another cup I! having flanges I8 preventing outward movement of electrode 9 and the cup I? also forms a mounting for a second operating spring 59 which is mounted between the shoulder 29 on the cup I! and the underside of mounting 4.

The cup I1 is provided with a constricted shoulder 2| which acts as a contact member for cooperation with contact 22 secured to the rod 5, as will be explained later.

The rod 5 is also provided with a further contact 23 near its other end as shown.

The mounting 4 is surrounded by a threaded portion 24 for co-operation with the socket shown in Figs. 2 and 3, underneath which is positioned a metal washer 6.

In assembling the device, the parts 3, 5 and 2d are connected together, e. g. by soldering and the springs 9 and I9 are of such normal length that they must be compressed for insertion into the casing l. The metal flange 3 is hermetically sealed on to the casing l whereby the ingress of moisture into the device is prevented so as to avoid risk of corrosion of the metal parts. A suitable termination for the rod 5 is shown at 25.

A suitable socket for the device of Fig. l is shown in Figs. 2 and 3. The socket comprises a body 26 of suitable material such as metal having a mounting flange 2'? for attachment to a suitable surface, e. g. by screws passing through apertures 22"; therein.

An insulated bush 29 lines the body 26 and is prevented from turning therein by a suitable key 3% situated at the base thereof fitting closely in aperture 3! in the body. The bush 2?) locates a spring 32 which itself is prevented from turning in the bush by forming one end with a radiallyprojecting portion 33 fitting in a slot 34 cut in the bush 29 from its top to the key 30.

The spring 32 is adapted to receive the switch device. The pitch of the spring is less than the pitch of the threads on the threaded portion 24, so that when the switch is screwed into the socket the spring is placed under tension thereby ensuring good connection between the parts and 42.

t the same time it forms a convenient means of reducing the transmission to the switch of any vibrations of the surface on which the device is mounted. The washer 5 causes the end of the spring d2 to jam in the top of the thread in member 2 before the radially-projecting portion 33 comes up against the bottom of the slot 3a in the bush 29.

The upper end of spring 32 has a projecting portion 35 soldered to a terminal member 36 located in a recess 3? in a terminal block 38 of insulating material. The latter has a further recess 39 accommodating a second terminal 43 soldered to lead M which goes to a centre contact stud 52 located in a recess 43 in the underside of block 38. The two terminals 35 and ill are soldered to 35 and M respectively thereby securing them in position and providing electrical connection. 323 and it respectively to clamp external circuit leads.

The block 38 is secured to the body 26 by screws ii (see Fig. 4). A rubber washer 48 separates the block 38 and the body 26.

Channels 4 9 and 5B are made in the block 38 for electrical leads to the terminals 35 and 4B. These channels 4%}, 50 are provided with rubber seals 5!, 5 2 located in suitable recesses, through which external circuit leads are connected to the terminals. This forms a convenient means of waterproofing the lead entry.

The block 38 also has screw holes 53 for affixing a cover plate 56. A rubber washer 55' is interposed between the cover plate 5 and the block 38.

The switch device is screwed into the spring 32 and a cover 56 is engaged over it. The cover is of metal and has threads 5i to engage threads 58 on the outside of body 26. A rubber gasket 59 serves to cushion and support the switch and provide waterproofing.

There is thus electrical continuity between terminal 36, spring 32, threads 24, mounting 4, spring l9, cup ll, cup M, spring electrode 9 and cup In, and between terminal Ml, contact stud 42, terminal 25, rod 5 and contacts 22 and 23.

To operate the switch it is only necessary to strike a blow on the casing i from any direction. If the blow is sideways, acting to remove completely the lower part of the glass casing, there will be no support for the compressed coil spring Screws M and 35 are provided in terminals electrode 9 which will thus expand and remove its support from the second operating spring Hi. The latter will move longitudinally until contact shoulder 2! strikes contact member 22 on the rod 5 establishing electrical contact between terminals 3% and 60 by the electrically conducting paths set out above. Thus, if the terminals 36 and 40 be connected in a suitable alarm circuit, breaking of the casing I will institute an alarm.

If the blow on the casing I be end-on, crushing the glass in a longitudinal compressing action, the spring 9 will be further compressed until the cup ii] strikes the contact 23 thereby establishing electrical continuity over the paths provided.

If the blow be a sideways one, it is feasible that no longitudinal movement of the contacts is possible but the sideways pressure will cause contact to be made between the coiled spring electrode 9 and the rod electrode 5.

Figs. 4 and 5 show an embodiment of the switch incorporating its own mounting and terminals as an integral structure.

All the operating parts are the same as the embodiment of Fig. l and have the same reference numerals. The closure devices for the upper end of the case are, however, difierent to provide for the integral mounting.

Surrounding the metal mounting 4 is an annular closure member Ell having a radially extending flange 6!. This flange provides a mounting bracket for the device and to this end is provided with apertures 82 for the passage of screws or the like. The member 66 is soldered to the mounting a.

The rod 5 is connected by a lead st to an external terminal 65. The upper portion of the device as now constituted is placed in a suitable mould that grips the edges of the flange 6! and a synthetic resin material is poured in which, when set, produces a block 66 of insulating material that seals off the upper portion completely, suitably embedding the terminal 65. The mould has a suitable plug to form a recess 6'! for connection of a suitable lead to the terminal which is threaded at 68 for a fixing screw.

In use the flange 6! acts as one terminal so that the device can be secured to a suitable metal fixing to which one lead of the alarm circuit is made, the other lead being taken to terminal 65.

The operation of the device of Figs. 4 and 5 is precisely the same as that of Fig. 1.

The invention thus provides an extremely simple alarm switch operable by breaking the casing I. It may, therefore, be used as a crash-detector switch for vehicles, particularly aircraft, when it could be secured to the craft to depend downwards immediately behind the outer skin or even externally from its body to effect actuation of an alarm circuit on impingement. The alarm circuit may comprise a simple warning signal device such as a lamp or buzzer or, preferably for this purpose, it may comprise a fire-fighting installation whereby a crash landing will automatically actuate fire-prevention or fire-fighting devices, such as sprays for fire-extinguishing compounds.

Alternatively, of course, the device may merely be mounted in a wall and connected to suitable warning circuits so that it may be used as an emergency signal device.

In order to be able to test the installation, the rod 5 may have a connection such as that shown at 69 in Fig. l. The connection 69 is sealed into and through the wall of the cover I to project externally at iii. If then a connection be made externally of the device between point 10 and the flange 6|, the circuit in which the device is connected will be completed whereby continuity of the circuit and effectiveness thereof may be rapidly tested.

We claim:

1. An alarm switch device for completing electrical circuits in the event of emergencies comprising an outer casing of frangible material having an elongated tubular form closed at one end, a rod electrode enclosed within said outer casing and extending substantially coaxially of the easing and for substantially the entire length thereof, a coiled electrode surrounding and spaced from said rod electrode, a block of insulating material supported by the closed end of said frangible envelope. means for locating said rod electrode in said block of insulating material out of contact with said coiled electrode, an external contact on said casing, means for connecting said external contact to said coiled electrode, said rod electrode being sealed into but projecting out of said casing, and sealing means for hermetically sealing said casing against the ingress of fluids and gases.

2. An alarm switch device as claimed in claim 1, in which the external contact is a screw thread and the projecting rod electrode is arranged coaxially with it.

3. An alarm switch device comprising a socket, two terminal contacts in said socket, an external screw thread on said socket, a demountable switch removably engaging in said socket and comprising an outer casing of frangible material having an elongated tubular form closed at one end, a rod electrode enclosed within said outer casing and extending substantially coaxially of the casing and for substantially the entire length thereof, a coiled electrode surrounding and spaced from said rod, a block of insulating material supported within said frangible casing at the closed end thereof, means for locating said rod electrode in said insulating block out of contact with said coiled electrode, contact means externally of said casing connected respectively to said two electrodes, said contact terminals in said socket being positioned for contact with said two external contacts on said switch device casing when said switch device is mounted within said socket, a closure device comprising a cap centrally apertured and having an internal screw thread so located and arranged that said closure device may be slipped over said casing protruding from said socket to allow the threads internally arranged on said closure device to engage over the threads externally arranged on said socket, and a flexible gasket arranged between the end of said socket and the interior of said closure device to cushion said demountable switch within said socket and closure device assembly.

4. An alarm switch device comprising a socket, two terminal contacts in said socket, a demountable switch removably engaging in said socket and comprising an outer casing of frangible material having an elongated tubular form closed at one end, a rod electrode enclosed within said outer casing and extending substantially coaxially of the casing and for substantially the entire length thereof, a coiled electrode surrounding and spaced from said rod, a block of insulating material supported within said frangible casing at the closed end thereof, means for locating said rod electrode in said insulating block, and contact means externally of said casing connected respectively to said two electrodes, said contact terminals in said socket being positioned for contact with said two external contacts on said switch device casing when said switch device is mounted within said socket.

5. An alarm switch device as claimed in claim 4, comprising a coil spring in said socket, locating means in said socket for locating said spring therewithin, and means connecting said coil spring to one of said contact terminals in said socket.

6. An alarm switch device as claimed in claim 4, comprising electrically-conducting external screw thread means on said frangible casing adapted to engage within the convolutions of said coil spring in said socket, said screw thread on said frangible casing comprising an external terminal connected to one of said electrodes within said casing.

7. An alarm switch device for completing electrical circuits in the event of emergencies comprising an outer casing of frangible material having an elongated tubular form closed at one end, a rod electrode enclosed Within said outer casing and extending substantially coaxially of the easing and for substantially the entire length thereof, a coiled electrode surrounding and spaced from said rod electrode, a block of insulating material supported b the closed end of said frangible envelope, means for locating said rod electrode in said block of insulating material out of contact with said coiled electrode, a metal closure cap for the open end of said frangible casing, means for connecting said cap to said coiled electrode, a mounting flange associated with said cap, said rod electrode being sealed into but projecting out of said casing out of contact with said cap, a terminal for external connection connected to said projecting rod electrode, and a block of insulating material moulded around said cap and terminal and over said flange but allowing a portion of said flange to protrude for mounting purposes and leaving exposed a portion of said terminal for external connection.

8. An alarm switch device as claimed in claim 7, and comprising further a second operating spring, a first contact member electrically connected to said coiled electrode within said casing, said operating spring being associated with said contact member and surrounding and spaced from said rod electrode, a second cooperating contact member on said rod located normally out of contact with said first contact member and means for normally holding said second operating spring under load, whereby in the event of fracture of the frangible casing the loading of said operating spring is removed to bring about contact between said two contact members.

9. An alarm switch device for completing electrical circuits in the event of emergencies comprising an outer casing of frangible material having an elongated tubular form closed at one end, a rod electrode enclosed within said outer casing and extending substantially coaxially of the casing and for substantially the entire length thereof, a coiled electrode surrounding and spaced from said rod electrode, means for locating said rod electrode out of contact with said coiled electrode, an operating spring, a first contact member electrically connected to said coiled electrode Within said casing, said operating spring being associated with said first contact member and surrounding and spaced from said rod electrode, a second cooperating contact member on said rod located normally out of contact with said first contact member, and means for normally holding said second operating spring under load whereby in the event of fracture or the frangible casing the loading of said operating spring is removed to bring about contact between said first and said second contact members, an external contact on said casing, means for connecting said external contact to said coiled electrode, said rod electrode being sealed into but projecting out of said casing, and sealing means for hermetically sealing said casing against the ingress of fluids.

10. An alarm switch device comprising a socktwo terminal contacts in said socket, an external screw thread on said socket, a demountable switch removably engaging in said socket and comprising an outer casing of frangible material having an elongated tubular form closed at one end, a rod electrode enclosed within said outer casing and extending substantially coaxially of the casing and for substantially the entire length thereof, a coiled electrode surrounding and spaced from rod, a block of insulating material supported within said frangible casing at the closed end thereof, means for locating said rod electrode in said insulating block out of contact with said coiled electrode, an operating spring, a first contact member electrically connected to said coiled electrode within said casing, said operating spring being associated with said first contact member and surrounding and spaced from said rod electrode, a second cooperating contact member on said rod located normally out of contact with said first contact member, and means for normally holding said second operating spring under load whereby in the event of fracture of the frangible casing the loading of said operating spring is removed to bring about contact between said first and said second contact members, contact means externally of said casing connected respectively to said two electrodes, said contact terminals in said socket being positioned for contact with said two external contacts on said switch device casing when said switch device is mounted within said socket, a closure device comprising a cap centrally apertured and having an internal screw thread so located and arranged that said closure device may be slipped over said casing protruding from said socket to allow the threads internally arranged on said closure device to engage over the threads externally arranged on said socket, and a flexible gasket arranged between the end of said socket and the interior of said closure device tocushion said demountable switch within said socket and closure device assembly.

11. An alarm switch device comprising a socket, two terminal contacts in said socket, a demountable switch removably engaging in said socket and comprising an outer casing of frangible material having an elongated tubular form closed at one end, a rod electrode enclosed within said outer casing and extending substantially coaxially .of the casing and for substantially the entire length thereof, a coiled electrode surrounding and spaced from saidrod, a block of insulating material supported within said frangible casi g at the closed end thereof, means for locating said rod electrode in said insulating block, an operating spring, a first contact member electrically connected to said coiledv electrode within said casing, said operating spring being associated with said first contact member and surrounding and spaced from said rod electrode, a second cooperating contact member on said rod located normally out of contact with said first contact member, and means for normally holding said second operating spring under load whereby in the event of fracture of the frangible casing the loading of said operating spring is removed to bring about contact between said first and said second contact members, and contact means externally of said casing connected respectively tosaid two electrodes, said contact terminals in said socket being positioned for contact with said twoexternal contacts on said switch device casing when said switch device is mounted within said socket.

FREDERICK HENRY TOWNSEND. HARVEY SYDNEY HALL.

Name Date Graham et al Apr. 24, 1917 Number

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