US3912893A

US3912893A - Anti-intrusion, self regulating switch with discriminating, sensing actuator including silicon putty

Info

Publication number: US3912893A
Application number: US477445A
Authority: US
Inventors: Arie Stoler
Original assignee: Israel Aircraft Industries Ltd
Current assignee: Israel Aircraft Industries Ltd
Priority date: 1973-06-11
Filing date: 1974-06-07
Publication date: 1975-10-14
Anticipated expiration: 1992-10-14
Also published as: CA1027206A; NL7407588A; IL42470A; BE816169A; DE2427131C2; NL178205C; IL42470A0; IT1014956B; DE2427131A1; ZA743698B; NL178205B

Abstract

Described is a switching device, particularly useful in wirefence protective systems, capable of discriminating between a quick movement of the wire-fence to actuate a signal, and a slow movement of the wire-fence (e.g. caused by temperature changes) which does not actuate the electrical signal. The switching device comprises a housing carrying the movable member, an electrical switch within the housing and including a casing and a switch operator projecting therethrough, an actuator mounted within the housing and movable by the movable member to actuate the switch operator, and a flowable material such as silicone putty between the movable member and the actuator.

Description

United States Patent Stoler Oct. 14, 1975 [54] ANTI-INTRUSION, SELF REGULATING 2,863,017 12/1958 Thatcher........................... 200/80 R SWITCH W DISCRIMINATING 3,516,279 6/1970 Maziarka ZOO/82 C X SENSING ACTUATOR INCLUDING SILICON 1634638 200/6193 PUTTY lnventor:

l/l972 Savyon et a1.

Primary Examiner-James R. Scott 75 A'Stl,Bt-Y' ,I l 1 v "e 0 er a am Srae Attorney, Agent, or Firm-Ben amm .l. Barish [73] Assignee: Israel Aircraft Industries Ltd., Lod,

lsrael ABSTRACT June 7, 1974 [21] Appl. No.: 477,445

7 22 Filed:

Described is a switching-device, particularly useful in wire-fence protective systems, capable of discriminating between a quick movement of the wire-fence to -[30] Foreign Application Priority Data June 11, 1973 actuate a signal, and a slow movement of the wire- 42470- fence (e.g. caused by temperature changes) which does not actuate the electrical signal. The switching device comprises a housing carrying the movable member, an electrical switch within the housing and 2 mm 53 mm 0 H rpm 2 m 8 O" 0" 2 m m wm 9m 1" 6 N U a ML Um M N 5w including a casing and a switch operator projecting therethrough, an actuator mounted within the housing and movable by the movable member to actuate the 2 4 37 832 5 ime 32 4 7 u 95 i 6 0 9 07 .3 wh D64 /1 O ,m %C4 2%., m h3 ne a & W m3 0 5 l 403/288 switch operator, and a flowable material such as silicone putty between the movable member and the actuator.

References Cited UNITED STATES PATENTS 2,345,77] 4/1944 Reynolds 340/261 12 Claims, 4 Drawing Figures II-'I L Illllll US. Patent 0a. 14, 1975 FIG.1

FIG.4

ANTI-IN'IRUSION, SELF REGULATING SWITCII WITII DISCRIMINATING, SENSING ACTUATOR INCLUDING SILICON I'll'lTY trical switching device of the foregoing type particularly for use in a wire-fence protective system, the switching device being actuated (cg. to provide a signal or sound an alarm) whenthe wire fence is pulled or cut in order to gain entry, but is not actuated when slow movements of the wire fence are produced, such as arising from the expansion or contraction of the wire fence because of temperature changes. The electrical switching device therein described includes a housing formed with an internal chamber containing an electrical contact adapted to he physically connected to the external element whose movement is to he detected,

and a second electrical contact movable relative to the first contact to effect actuation of the switch. The device further includes a yieldable connection between the two contacts tending to cause the second one to move with the first one upon movement ofthc external element. A flowable material is provided which resists the movement of the second contact with the first one. The flowable material is free-flowing under a low stress but not under a sudden high stress. The arrangement is such that a sudden movement of the external element causes the flowable material to resist the movement of the second contact with the first one as the yieldable connection yields. thus effecting actuation of the switch; whereas a slow movement of the external element causes the flowable material to permit the movement of the second contact with the first one by the yieldable connection. thus not effecting actuation of the switch. A preferred flowable material that can be used is silicone putty.

Such a switching device has been successfully used in wire-fence protective systems which are capable of discriminating between a quick movement of the wirefcnce to actuate a signal. and a slow movement of the wire fence (e.g. caused by temperature changes) which does not actuate the electrical signal.

The present invention provides an improved electrical switching device of the foregoing type having a number of important advantages.

SUMMARY OF THE PRESENT INVENTION According to the present invention, the switching device comprises a housing carrying the movable memher, an electrical switch mounted within the housing and including a casing and switch operator projecting therethrough, an actuator mounted within the housing and movable by the movable member to actuate the switch operator; and the flowable material interposed between the movable member and the actuator. The

flowable material is of the same types as in US Pat. No. 3,634,638. That is, it is relatively free-flowing under a low stress, but not under a high stress such that it effects a motion-transmitting coupling between the actuator and the movable member upon sudden movement of the latter to move the actuator sufficiently to actuate the switch operator; but upon slow movement of the movable member the flowable material effects a slip-coupling between the movable member and the actuator so that the actuator is not moved sufficiently to actuate the switch operator.

As in the preferred embodiment disclosed in the above-cited patent, the flowable material is preferably silicone putty. This material has the appearance of ordinary putty but possesses a unique combination of physical properties. Under low stress it is plastic and free flowing, and even flows under its own weight. However under sudden stress it acts as a solid: itwill bounce when in ball form and will even-shatter like glass.- This material is known and has been commercially available for a number of years. One product that has been found particularly advantageous for use is that known as General lilectric ('i-li SS-H Silicone Bouncing Putty."

According to a further feature of the invention the actuator includes a cylindrical cup open at the top and containing the flowable material, and a separate ele-' ment movable with respect to the cup and embedded in the flowable material.

According to a further feature, the top of the cylindrical cup is rounded to form a ball socket, and the separate element of the actuator includes a rounded portion pivotable within the socket. Also, the rounded portion of the actuator element is substantially semisphcrical, and the embedded portion is substantially conical.

According to further features of the invention, the switch casing is carried by a block which is movable to preset the position of the switch operator with respect to the actuator. The switch block is presettable by a threaded cap received within a threaded opening at the bottom of the housing, the cap including a mechanical coupling between it and the block effective to nonrotatably move the block axially of the housing upon threading the cap into or out of the housing.

According to still further features, the movable member includes an external element projecting through the top of the housing and pivotably mounted to the housing, and an internal element engaging the actuator within the housing. In the described embodiment, the movable member is pivotably mounted to the housing by means of a pivot pin disposed perpendicular to the axis of the actuator. The external element of the movable member is threaded for receiving a nut to clamp to the movable member the fence wire whose movement is to be sensed by the switching device.

When the switching device is constructed in accordance with all the foregoing features, a number of important advantages are provided: First, the improved construction enables the use of simple snap-action switches which are commercially available at low prices and which provide a positive snap-action contact when actuated. Also, the contacts of the electrical switch are closed within a casing and are therefore not exposed to the silicone putty which may tend to corrode them. Similarly, the electrical conductors leading from the electrical contacts are also not exposed to the silicone putty. Further, the improved construction enables the switching device to be easily assembled and disassembled for repair or maintenance purposes.

An additional advantage in the improved construction is that it enables the sensitivity of the switch to be easily preset, by threading the bottom cap to accurately preset the position of the switch operator with respect to the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the invention will be apparent from the description below.

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a side elevational view of an improved electrical switching device constructed in accordance with the invention, the switching device being embodied in a wire fence protective system;

FIG. 2 is an enlarged longitudinal sectional view of the switching device of FIG. 1;

FIG. 3 is a transverse sectional view along lines 1"- -III of FIG. 2; and

FIG. 4 is a transverse sectional view along lines lVlV of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The switching device illustrated in the drawings is particularly designed for use in a wire-fence protective system, to actuate a signal or a sound an alarm when the wire fence is moved or cut in order to gain entry, but to be non-responsive to small movements of the wire-fence, e.g. as arising from expansion or contraction of the wire because of temperature changes.

FIG. 1 illustrates the switching device, generally designated 2, mounted to a pole 4 of the wire fence by means of a clamp 6. The wires 8 of the fence are clamped to the switching device by means of a nut 10 threaded onto a bolt 12, the threaded end 12' of which projects from the top of the switching device. Bolt 12 is formed with an enlarged head 14 also exterior of the switching device. The fence wires 8 (e.g. barbed wire) are clamped between the head 14 and a washer 16 when nut 10 is threaded firmly onto bolt 12.

Switching device 2 comprises a cylindrical plastic housing 20 formed with an internal cylindrical chamber 22 (FIG. 2). Preferably, the upper end 20a of housing 20 has a slightly larger external diameter than the lower end 20b. The upper end of the housing is closed by a rubber cap 24 formed with a depending annular skirt 26 frictionally engaging the side wall of housing 20, and the lower end of the housing is closed by a plastic cap 28 formed with threads 30 engaging corresponding threads 32 formed in the inner surface of the housing.

Bolt 12 includes an extension 34 passing through cap 24 and terminating in a flat circular face 36 within housing 20. Bolt 12 is pivotably mounted to the housing by means ofa pivot pin 38 passing through a transverse bore formed in extension 34 and received between a pair of aligned openings 40 formed in the upper end of the housing. A rigid retainer ring 42 received within an annular groove in cap 24 firmly secures bolt 12 within the opening of the cap.

An electrical switch is disposed in the lower end of chamber 22 of the housing 20. Switch 50 may be a conventional snap-action electrical switch having a switch operator 52 projecting through the upper end of the switch casing 54. The electrical contacts (not shown) of the switch are connected to electrical conductors 56 passing through grommet 58 inserted within an opening in the wall of housing 20. Switch 50 is mounted within the housing by means ofa switch block 60 to which it is attached by any conventional means.

A switch actuator, generally designated 62, is interposed between the bottom face 36 of bolt 12 and the operator 52 of switch 50. Switch actuator 62 includes a cylindrical cup 64 formed with a depending stem 66 engagable with switch operator 52 and with a separate coupling element generally designated 68, formed with a flat circular face 70 at its upper end engagable with flat circular face 36 of bolt extension 34. Coupling element 68 is formed with an upper semi-spherical portion 72, and with a lower conical portion 74. The upper end of cup element 64 of the actuator is rounded, as shown at 76, and serves as a socket for receiving the semispherical portion 72 of the actuator coupling elements 68.

The interior of the cup member 64 contains the flowable material 78 having the properties described above, a preferred example of which is silicone putty. Conical portion 74 of the actuator coupling element 68 is embedded within this flowable material.

The lower face of stem 66 of the actuator 62 is normally spaced above switch operator 52 by means of coil spring 80 interposed between an annular shoulder 81 formed on the actuator, and switch mounting block 60. The exact position of switch operator 52 may be preset by threading the bottom cap 28 more or less within housing 20, the cap including a mechanical coupling between it and switch block 60 effective to nonrotatably move the switch block axially of the housing when the cap is so threaded within the housing. The latter mechanical coupling includes a disc 82 depending from the bottom of switch block 60, which disc is disposed within a semi-circular interned flange 84 formed at the upper end of cap 28. The lower face of the cap may have a slot 86 to facilitate rotation of the cap, and the cap may be sealed within the housing by a sealing ring 88.

In use, the switching device is mounted onto a pole 4 (FIG. 1) of the fence by means ofa clamp 6, and the fence wires 8 are clamped to external bolt portion 12 of the switch by means of nut 10.

It will be seen that bolt 12 projecting exteriorly of the housing together with its extension 34 disposed internally of the housing forms a movable member which pivots around pin 38 when the fence wire 8 clamped thereto is moved. The lower circular face 36 of the internal extension 34 is in contact with the upper circular face 70 of the actuator coupling element 68, so that any pivotable movement of bolt 12 will also tend to pivot coupling element 68 within cup 64 of the actuator. However, the lower conical portion 74 of coupling element 68 is embedded within the previously described flowable material, for example silicone putty, and therefore this pivotable movement of the coupling element, and the cup 64 in which it is disposed, will be affected by the silicone putty.

Thus, when there is a sudden movement of the movable member (i.e. external bolt 12 and its internal extension 34), the silicone putty 78 will be subjected to a sudden high stress, and therefore will not be freeflowing. It will therefore effect a motion-transmitting coupling between element 68 and cup 64 of the actuator, whereby the pivotable movement of the lower face 36 of bolt 12 causes the actuator, including its coupling element 68 and cup member 64, to be lowered against the action of spring 80 until the bottom face of stem 66 of the actuator engages switch operator 52 and actuates the switch. The sudden movement of the wire fence will thus result in the actuation of the switch, which switch can be used to sound a signal or alarm to indicate this condition.

However, when the fence wire 8 is gradually moved, for example because of expansion and contraction of the fence wire arising from temperature changes, the resulting pivotal movement of bolt 12 will apply a low stress to the silicone putty 78. Under such conditions, the putty will flow and will thus permit coupling element 68 to pivot or rotate within the socket edges 76 of cup member 64. A slip-coupling is thus produced between

elements

68 and 64 of the actuator, such that the lower stem 66 of the actuator is not depressed to actuate switch operator 52.

Thus the switching device illustrated is capable of discriminating between fast movements and slow gradual movements of the fence wire, and will be responsive to the former but not to the latter.

As indicated earlier, the switching device illustrated has a number of important advantages over the construction illustrated in the above-cited prior patent. Thus, switch 50 may be one of the many standard snapaction switches which are commercially available at low cost. Further, the snap-action of the switch produces a more positive operation than the non-snapaction illustrated in the above-cited patent. Also, the contacts of the switch are protected within the casing, and are therefore not exposed to the silicone putty material which may corrode the contacts over a period of time. The electrical conductors leading to the switch are also not so exposed. In addition, the sensitivity or pretravel of the switching may be accurately preset by rotating cap 28 to preset the operating position of switch operator 22 with respect to the lower end of the actuator 62. Still further, the improved design facilitates the assembly of the switching device, and also its dissassembly for purposes of repair or maintenance.

Many variations and other applications of the illustrated embodiment will be apparent.

What is claimed is:

1. An electrical switching device responsive to sudden movements of a movable member, comprising: a housing carrying the movable member; an electrical switch mounted within the housing and including a casing and a switch operator projecting therethrough; an actuator mounted within the housing and movable by the movable member to actuate the switch operator; and a flowable material between the movable member and the actuator, said flowable material being relatively free-flowing under a low stress but not under a high stress such that it effects a motion-transmitting coupling between the actuator and the movable member upon sudden movement of-the latter to move the actua-.

tor sufficiently to actuate the switch operator, but upon slow movement of the movable member the flowable material effects a slip-coupling between the movable member and the actuator so that the actuator is not moved sufficiently to actuate the switch operator.

2. A switching device according to claim I, wherein said flowable material is silicone putty.

3. A switching device according to claim 1, wherein said actuator includes a cylindrical cup open at the top end and containing said flowable material, and a separate element movable with respect to said cup and embedded in the flowable material.

4. A switching device according to claim 3, wherein the top of the cylindrical cup is rounded to form a ball socket, and said separate element of the actuator includes a rounded portion pivotable within said socket.

5. A switching device according to claim 4, wherein said rounded portion of the actuator element is substantially semi-spherical, and said embedded portion is substantially conical.

6. A switching device according to claim 3, wherein said actuator includes a stem depending below said cup, and said housing includes a spring normally biasing said stem away from the switch operator.

7. A switching device according to claim 1, wherein said switch casing is carried by a block which is movable to preset the position of the switch operator with respect to the actuator.

8. A switching device according to claim 7, wherein said block is presettable by a threaded cap received within a threaded opening at the bottom of the housing, said cap including a mechanical coupling between it and the block effective to non-rotatably move the block axially of the housing upon threading the cap into or out of the housing.

9. A switching device according to claim 8, wherein said mechanical coupling includes a disc formed at the end of the block and disposed within a semi-circular inturned flange formed at the end of the cap.

10. A switching device according to claim 1, wherein said movable member includes an external element projecting through the top of the housing and pivotably mounted to the housing, and an internal element engaging the actuator within the housing.

11. A switching device according to claim 10, wherein theimovable member is pivotably mounted to the housing by means of a pivot pin disposed perpendicular to the axis of the actuator.

12. A switching device according to claim 10, wherein the external element of the movable member is threaded for receiving a nut to clamp to the movable member the wire whose movement is to be sensed by the switching device.

Claims

1. An electrical switching device responsive to sudden movements of a movable member, comprising: a housing carrying the movable member; an electrical switch mounted within the housing and including a casing and a switch operator projecting therethrough; an actuator mounted within the housing and movable by the movable member to actuate the switch operator; and a flowable material between the movable member and the actuator, said flowable material being relatively free-flowing under a low stress but not under a high stress such that it effects a motion-transmitting coupling between the actuator and the movable member upon sudden movement of the latter to move the actuator sufficiently to actuate the switch operator, but upon slow movement of the movable member the flowable material effects a slip-coupling between the movable member and the actuator so that the actuator is not moved sufficiently to actuate the switch operator.

2. A switching device according to claim 1, wherein said flowable material is silicone putty.

11. A switching device according to claim 10, wherein the movable member is pivotably mounted to the housing by means of a pivot pin disposed perpendicular to the axis of the actuator.