IL30399A - Electrical switch responsive to movements - Google Patents

Description

ELECTRICAL SWITCH RESPONSIVE TO MOVEMENTS The present invention relates to electrica switches* and particularly to electrical switches responsive to movements or displacements of an external element.

Many types of movement-responsive or displacement-responsive electrical switches are known* All or most of the known ones, however, cannot distinguish between sudden or quick movements on the one hand, and slow movements on the other. There are some applications where it is desired to have the electrical switch responsive only to sudden or quick movements, and to be non-responsive to slow movements. For example, one such application would be in protective systems for wire—fenced areas, where it may be desired to actuate the protective system (e.g. to provide a signal or sound an alarm) when the wire fence is pulled or cut in order to gain entry, but not to actuate the protective system when slow movements of the wire fence are involved, such as arising from the expansion or contraction of the wire because of temperature changes.

An object of the present invention is to provide a simple electrical switch whic is responsive to sudden movements of an external element but is non-responsive to slow movements of the element* According to the invention* there is provided an electrical switch responsive to sudden movements of an external element9 characterized in that it includes a housing formed with an internal chamber containing a first electrical contact adapted to be physically connected to said external element to be moved thereby, a second electrical contact movable relative to said first contact to effect the actuation of said switch, a yield-able connection between said irst and second contacts tending to cause the latter to move with the former upon the movement of the former by said external element, and a flowable material tending to resist the movement of said second contact with said first contact, said flowable material being free flowing under a low stress but not under a sudden high stress, whereby a sudden movement of the external element causes the flowable material to resist the movement of said second contact with said first contact while said yieldable connection yields, thus effecting actuation of said switch, whereas a slow movement of the external element movement of said second contact with said first contact by said yieldable connection, thus not effecting actuation of said switch.

She flowabie material could conceivably be a liquid, e.g. a very viscous organic dielectric liquid, or even a paste.

According to a further important feature of the invention, however, the flowabie 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 ree flowing and even flows under its own weight. However, under sudden stress it acts as a solid; it will bounce when rolled as a ball and will even shatter like glass. This material is known and has been commercially available for a number of years. It is commonly used as a toy or novelty item and as an exerciser for crippled muscles. Particularly good results are attained when it is used as the flowabie material in the switch of the present invention. One product that may be used is that known as "General Electric Gf-B SS-91 Silicone Bouncing Putty .

Further features and advantages of description below.

The invention is herein described, by way of example only, with reference to the accompanying drawings* wherein: Pig.1 is a longitudinal sectional view of an electrical switch constructed in accordance with the invention; and Fig. 2 is a top plan view of the switch of Fig. 1.

She switch illustrated in the drawings comprises a cylindrical plastic housing 2 formed with an internal cylindrical chamber 4» The upper end of the chamber is closed by a cap 6 of resilient insulating material formed with an internal annular lip 8 adapted seat in an annular groove in the housing wall* The lower end of chamber 4 is closed by wall 10.

A metal rod 12 passes through resilient cap 6 and is anchored within the cap by a pair of annular rings 14 and 16 fixed to the rod.

A metal pin 18 is fixed to the lowe ring 16 and serves as one of the electrical contacts of the switch. The second electrical contact is in the form of a metal sleeve 20 supported by a resilient insulating sleeve 22 which is a continuation of resilient cap 6, contact 20 purpose the upper end of rod 14 carries a clamping element or hook 36 adapted to be clamped or hooked to the wire.

The operation of the switch will be apparent from the foregoing description.

Assuming that the switch is to be used for sensing the sudden movement of wire 34 of a fence, bracket arms 28 and 0 would be mounted to pole 29 of the fence with clamp % engaging the wire. One side of the electrical circuit (e.g. , a signalling or alarm circuit) would be connected to the wire 34; and the other side would be connected to the metal bracket 28 or to the post 29» if metal.

Under normal conditions* contact 18 is spaced from contact 20, and therefore this electrical circuit is open* When a stress is applied to wire 34» clamp ■ is permitted to pivot by resilient cap 6, this also causing electrical contact 18 to pivot. Contact 20» being mounted to contact 18 by means of resilient insulating sleeve 22 which acts as a yieldable connection, also tends to move with that contact, but this movement is opposed by the flowable silicone putty 32.

How, if the movement of wire 54 ie sudden and large, such as would be produced by someone pulling or cutting the wire to gain access into the protected area, a high stress is produced in the flowable silicone putty 32. Since this material is not free flowing unde high stress, it will resist the movemen of contact 20 with contact 18. Contact 18 will thus ena e contact 20, while the resilient sleeve 22 yields, and the switch will be actuated to sound the alarm or to provide the signal * On the other hand, if the movement of wire 34 is very slow, such as would be produced by the expansion or the contraction of the wire during changing temperature conditions, or by the wind, the flowable silicone putty 32 is subjected to a low stress. Shis material being relatively free flowing under low stresses, it wil not prevent the movement of contact 20 with contact 18 by resilient sleeve 22, and thus the two contacts will be held apart, and the switch will not be actuated.

Many changes, variations and other applications of the illustrated embodiment of

Claims (8)

WHAT IS CLAIMED IS:-

1. · An electrical switch responsive to sudden movements of an external element, characterized in that it includes a housing ormed with an internal chamber containing a first electrical contact adapted to be physically connected to said external element to be moved thereby, a second electrical contact movable relative to said first contact to effect the actuation of said switch, a yleldable connection between said first and second contacts tending to cause the latter to move with the former upon the movement of the former by said external element, and a flowable material tending to resist the movement of said second contact with said first contact, said flowable material being free flowing under a low stress but not under a sudden high stress, whereby a sudden movement of the external elemen causes the flowable material to resist the movement of said second contact with said first contact while said yleldable connection yields, thus effecting actuation of said switch, whereas a slow movement of the external element causes the flowable material to permit the movement of said second contact with said first contact by said yieldable connection, thus not effecting actuation of said switch.

2. An electrical switch according to Claim 1, wherein said flowable material is silicone putty.

3. An electrical switch according to either of Claims 1 or 2, wherein said second contact is a metal sleeve, and said yieldable connection is a resilient insulating sleeve normally supporting said second contact around and out of engagement with said first contact*

4. An electrical switch according to Claim 3» wherein said resilient sleeve is carried by a resilient cap closing the upper end of said housing* said resilient cap supporting said first contact in suspension and including a rigid member passing therethrough and adapted to be connected to said external element*

5. An electrical switch according to Claim 4, wherein said flowable material fills said housing chamber to the level of said second contact* the latter being tapered at its lower end*

6. An electrical switch according to any one of Claims 1-5. further includin a metal bracket arm attached to the housing at the lower end thereof, there being an electrical connection between said second contact and said bracket arm.

7. An electrical switch according to Claim 6, further including a second bracket arm attached to a mid-portion of said housing for mounting same to a support*

8. An electrical switch substantially as described with reference to and as illustrated in the accompanying drawings. COHEN ΖΕΌΈΚ AHD SPISEACH P.O. Box 1169, Tel Aviv Attorneys for Applicants