GB2157498A

GB2157498A - Multi-input electrical switch

Info

Publication number: GB2157498A
Application number: GB08508283A
Authority: GB
Inventors: John T Grant
Original assignee: Maximal Security Products Ltd
Current assignee: Maximal Security Products Ltd
Priority date: 1984-04-09
Filing date: 1985-03-29
Publication date: 1985-10-23
Also published as: GB2157498B; GB8508283D0

Abstract

A personal attack or panic switch such as used in security systems in which an actuator (22) is displaceable to a switching position in response only to two or more operating devices such as push buttons (12, 14). The operation of one button only, produces insufficient (or no) displacement of the actuator (22) to reach the switching position. The switch is less susceptible of accidental operation since to effect switching two (or more) buttons have to be depressed simultaneously, or successively i.e. one is depressed while the other(s) is (are) held down. In the preferred embodiment the actuator (22) carries a magnet into or out of close proximity with a magnetic reed switch, the actuator (22) including a linkage (50) having portions that are flattened by respective pushbuttons (12, 14). <IMAGE>

Description

SPECIFICATION Electrical switch This invention relates to an electrical switch more particularly, but not exclusively, a "personal attack" or "panic" switch such as used in security systems.

Hitherto, these switches have made use of a single push button which when operated opens or closes an electrical alarm circuit, the circuit remaining open or closed even when the push button is released. It can be reset only by means of a key. The state of the circuit is indicated by a coloured marker visible through an aperture in the switch housing. In many security systems operation of such switches results in a silent alarm signal which is relayed to some remote location calling for a response by (e.g.) the police, security officers or medical teams.

With this increasing use of p.a. or panic switches the number offalse alarms due to accidental operation of a switch, often whilst cleaning or decorating close to the switch, there has been a corresponding increase in false alarms. Clearly, false alarms are undesirable if only because of the time wasted in responding thereto, and one object of the present invention is to provide an electrical switch particularly suited for use as a p.as. or panic switch and less susceptible of accidental operation.

In accordance with the present invention we propose an electrical switch having an actuator which is displaceable to a switching position in response to at least two operating devices preferably in the form of push buttons, the arrangement being such that in response to operation of one device only the displacement of the actuator, if any, is insufficient to reach the switching position. The operating devices may act either directly or indirectly upon an elongate member to produce lateral deflections thereof, one end of the elongate member being fixed relative to the switch housing and the other being free to move causing displacement of the actuator, which is preferably mounted for sliding in the switch housing between an inoperative and an operative or switching position.

In the preferred embodiment, the elongate member is convoluted and may be flexible or hinged or otherwise foldable at intervals along its length. The operating devices in the form of push buttons, when depressed act directly or indirectly on the member tending to flatten peaks therein so extending the member. Only when the push buttons are depressed simultaneously or one is depressed while the other or others is or are held down, is the actuator moved to the operative or switching position. Two push buttons are, in general, adequate to safeguard against accidental operation of the switch.

If movement of the actuator is resisted by friction of some other biasing force, a clearance or lost motion may be provided as in the embodiment described below whereby lateral deflection of the elongate member in response to operation of one device or push-button may increase the height of the peak presented to the other push-button, such that there is no extension oftheflexible member until the second push-button is depressed. It will be appreciated however, that the flexible member may extend in response to depression of each pushbutton, the extension being cumulative and such that only when both buttons are depressed is the displacement of the actuator sufficient to reach the switching position.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, ofwhich: Figure 1 is a front view of a p.a. switch; Figure 2 is a part cross-sectional side view of the switch of Figure 1; Figure 3 is a rear view also partly in cross-section of the switch of Figure 1; Figure 4 is a cross-section taken on line A-A in Figure 3; and Figures 5a-5b illustrate operation of the switch shown in Figures 1 to 4.

The switch 10 in the illustrated embodiment is similar in size and shape to commonly available electrical fittings but is operable by two pushbuttons 12, 14 disposed within adjacent recessed openings in the front cover 16 of the switch. In addition, the cover is formed with a keyhole 18 for inserting a resetting key, and a viewing aperture 20 through which a coloured marker, red when "set" and green when "reset", is visible to indicate the state of the switch. Operation of the switch depends upon movement of a sliding actuating member 22 carrying on one side a magnet 24 received in one of two receptacles 26,28 provided for the purpose in a laterally extending wing 30.As the slide is moved in the direction of the longitudinal axis XX thereof, so that magnets are brought into close proximity of a magnetic reed switch 32 mounted in a recess 34 of the switch housing so making or breaking contact betweeen electrical terminals connected in e.g. an alarm circuit. Whether contact is made or broken will depend upon which receptacle contains the magnet.

On the other side of the sliding member is a second lateral wing 36 carrying a projection 38 which when the slide 22 is in the switch operating position with the magnet adjacent the reed switch, is disposed in the arcuate path 40 swept by a key inserted in the key-hole. In the absence of spring loading, the switch can be reset (by moving the slide to the position shown in Figure 3) only by means of a key. It will, however, be understood that the slide could be held in the switch operating position against the action of biasing means, by a locking device releasable by means of a key or in some other secure manner.

Aflexible actuating strip 42 is mounted within the actuating slide 22, with one end 44 thereof fixed relative to the switch housing. The other end 46 of the strip abuts an end piece of the slide 22. In the reset position illustrated, the strip which is hinged 48 at intervals along its length is convulated such that two peaks 50 are formed. Adjacent each peak is a spring loaded push-button 12,14 having a finger pad and a plunger which enters a recess 52,54 in the switch housing and passes through an elongate hole 56 in the strip whereby the strip can move relative to the push-buttons in the direction of the longitudinal axis XX.

With reference now to Figures 5a to 5d, if any one button 12, is depressed, the peak 56 under the button will flatten and cause the peak 56 underthe other button to rise. The unattached end 46 of the flexible actuating strip 22 will not produce sufficient pressure on the actuating piece to overcome its frictional restraint. If both buttons are pressed, or any one button followed by the other is pressed, then the flexible actuator will be flattened and its unattached end 46 will move causing the actuating piece 22 to move longitudinally. The actuating slide 22 is suitably made of a strong thermoplastics material such as acetal copolymer and may also be coloured red. Part of the red actuating piece may be visible through the aperture 20 when the switch is operated. When the switch is reset a green or other colour marker on the actuating piece will be visible through the aperture.

Claims

CLAIMS:

1.An electrical switch having an actuatorwhich is displaceable to a switching position in response to at least two operating devices, the arrangement being such that in response to operation of one device only the displacement of the actuator, if any, is insufficient to reach the switching position.

2. A switch according to claim 1 wherein the operating devices act upon an elongate member to produce lateral deflections thereof, one end of the member being fixed relative to the housing and the other being free to move causing displacement of the actuator.

3. A switch according to claim 2 wherein the elongate member is convoluted and foldable at intervals along its length, the operating devices acting directly or indirectly on the elongate member to flatten peaks therein so extending the member.

4. A switch according to any one of claims 1 to 3 wherein the actuator is mounted for sliding in the switch housing between an inoperative position and the switching position.

5. A switch according to claim 4 comprising a magnetic reed switch, the actuator carrying a magnet which is brought to or moved from close proximity of the reed switch to effect operation thereof by displacement of the actuator.

6. An electric switch constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.