GB2120016A

GB2120016A - Lockable electrical switch

Info

Publication number: GB2120016A
Application number: GB08312220A
Authority: GB
Inventors: Franz Rutterschmidt
Original assignee: Preh GmbH
Current assignee: Preh GmbH
Priority date: 1982-05-11
Filing date: 1983-05-04
Publication date: 1983-11-23
Also published as: GB2120016B; FR2526997B3; DE8213561U1; FR2526997A1; GB8312220D0

Abstract

A button-operable electrical switch (1) which is adapted and arranged to be operable to perform a predetermined switching operation only with the cooperation of a security key (10), the switch (1) comprising a button (5) movable in a predetermined direction towards a housing (2) to operate the switch (1) to perform said predetermined switching operation, and a blocking member (9) which projects resiliently from the button (5) substantially in said predetermined direction to abut against a fixed surface (8) of the switch (1) thereby to prevent movement of the button (5) in said predetermined direction without the use of a security key (10), the button (5) comprising an aperture (6) in which an appropriate security key (10) can be inserted to deflect the blocking member (9) away from its abutment against said fixed surface (8) to pass through a window (17), thereby to release the button (5) for movement in said predetermined direction. <IMAGE>

Description

SPECIFICATION A key-operable electrical switch This invention relates to a button-operable electrical switch which is adapted and arranged to be operable to perform a predetermined switching operation only with the cooperation of a security key.

An example of such a key-operable switch is a switch which can be operated only by turning a key or by inserting a key. The switch can therefore only be operated if the user is in possession of the correct key. There are many different types of key-operable switches. They are used for example to operate drive motors of rolling doors at the front of garages, factories, store doors, and at many other places, always when the switching-on and -off, or even only the switching-on, of a drive or appliance in question is intended to be restricted to a certain group of people who have a key therefor. Key-operated switches in the form of push-button switches with keys are also used in appliances associated with the radio and television industry, in order in particular to prevent an appliance being switched-on by unauthorised persons. Switching-off can be carried out both with and without keys.

According to the present invention there is provided a button-operable electrical switch which is adapted and arranged to be operable to perform a predetermined switching operation only with the cooperation of a security key, the switch comprising a button movable in a predetermined direction to operate the switch to perform said predetermined switching operation, and a blocking member which projects resiliently from the button substantially in said predetermined direction to abut against a fixed surface of the switch thereby to prevent movement of the button in said predetermined direction without the use of a security key, the button comprising an aperture in which an apropriate security key can be inserted to deflect the blocking member away from its abutment against said fixed surface, thereby to release the button for movement in said predetermined direction.

A development of the invention comprises a further blocking member which projects resiliently from the button substantially in said predetermined direction to abut against a fixed surface of the switch thereby to prevent movement of the button in said predetermined direction without the use of the security key which, when inserted into said aperture, deflects both blocking members away from their abutment against the cooperating associated fixed surface, thereby to release the button for movement in said predetermined direction.

In the development, preferably the two blocking members extend side-by-side and are urged away from one another by the security key when it is inserted in the aperture to a position in between the two blocking members.

For a better understanding of the invention and to show how it may be put into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is an exploded perspective view of one embodiment of a key-operated switch according to the present invention, in combination with an appropriate security key; Figure 2 is a sectional lateral elevation of a front part of the key-operated switch of Fig. 1; Figure 3 is a plan view of a front part of the key-operated switch in partial section, the upper half of the key-operated switch being shown without the key and the lower half being shown with the key; and Figure 4 is a front elevation of the operating button with a hub and guide ribs on the inside of the button shown in broken lines.

The key-operated switch indicated as a whole by 1 in Fig. 1 comprises a housing 2, in which an electrical switching system is accommodated. Since the design of the switching system is of no significance as far as the invention is concerned, it is not shown in the figures. Only associated soldering lugs 1 2 projecting out of the housing 2 are visible in Fig. 1. A right-angled metal retaining clip or mounting plate 8 is mounted on the front end of the housing 2, which clip serves to secure the key-operated switch 1 for example to a chassis.

The switching system is operated with the aid of a slide switch rod 3, which is displaceable in the housing 2 against the force of a compression spring 4. A plastics operating knob or button 5 made of plastics is pushed onto the free end of the slide switch rod 3.

Securing of the knob 5 on the end of the rod 3 is effected by the fact that there is formed, on the upper half of the interior of the frontal wall 7 of the operating knob 5, a hollow hub 1 8 which receives the free end of the slide switch rod 3 in a force fit. This arrangement can be seen in Fig. 2.

In the lower half of the frontal wall 7 of the operating knob 5 is an insertion aperture 6 for a security key 1 0. This key 10 consists of a key head part 23 and a key bit 21, whose front end has an inserting bevel 1 6 on both sides. Cast in the centre of the key bit 21 is a flat, raised bar 24. Situated on the bar 24 are two engaging lugs 22, whose distance from the head part 23 of the key corresponds more or less to the thickness of the frontal wall 7 of the operating knob 5. With the aid of these engaging lugs 22, which engage behind the frontal wall 7, the key 10 can be retained in the operating knob 5.In order that the engaging lugs 22 can engage more efficiently, the bar 24 is cut way at its underside at least in the area of the engaging lugs 22, so that the bar 24 can flex when the key bit 21 is being inserted into the operating knob 5, until the key bit 21 notches into place with the lugs 22 engaging at the rear side of the wall 7.

In order to prevent the switch from being operated without a key 10, a blocking means is provided. This blocking means consists of two spring limbs 9 (one being visible in Fig.

1) moulded onto the interior of the frontal wall 7 of the operating knob 5, which limbs 9 coact with the retaining clip 8 in such a manner as to effect locking or unlocking. The spring limbs 9 are moulded in such a way that they extend towards each other when no key 10 is inserted. Each spring limb 9 consists of a first section 1 3 and a second section 14, the first section 1 3 having a smaller cross-section compared to the second section 14. This is so because a better spring effect can be achieved thereby when the spring limbs 9 are splayed when the key 10 is inserted.

Situated on the free end of the second section 14 of each spring limb 9 is an abutment shoulder 11, which, when no key 10 is inserted (as shown in the upper half of Fig. 3) abuts the edge of a window 1 7 in the front wall of the retaining clip 8, thus preventing displacement of the knob 5 and the slide switch rod 3 in the direction towards thefront wall of the retaining clip 8. If the key 10 is inserted (as shown in the bottom half of Fig.

3) the spring limbs 9 are splayed apart and thus enable the knob 5 and the rod 3 to be displaced towards the front wall of the clip 8.

The second sections 14 of the limbs 9 simply pass freely through the windows 1 7. In order to facilitate the splaying-apart of the spring limbs 9, each first limb section 1 3 merges into the second limb section 14 by means of an approach bevel 1 5. When the key is being inserted, the insertion bevels 1 6 act on the approach bevels 1 5 to urge the limbs 9 apart.

In order to guide the key 10 in the operating knob 5, two first guide ribs 1 9 are formed on the lower parting wall of the hollow hub 18. A second guide rib 20 is formed on the inner lower wall of the knob 5 in opposite and spaced arrangement relative to the first guide ribs 19, the spaces between the ribs 1 9 and 20 being matched to the thickness and shape of the key bit 21.

The fact that key-operable switches which are according to the invention and its developments may be mass-produced articles means that even very small cost savings in a particular design can be crucial. When the key 10 is inserted, the resilient limbs 9 are splayed in such a way that they project exactly into or through the windows 17. When the switch is operated then, no additional force for the sliding process needs to be applied. There is a basic tendency in mains switches to make the switch as readily operable as possible. Bearing this in mind, disadvantageously an additional force would have to be applied if the spring limbs 9 were moulded to the housing 2, since the spring limbs 9 would then exert a continuous lateral force onto the key 10, so that an additional frictional force would then have to be overcome between the key 10 and spring limbs 9 during displacement.

Claims

1. A button-operable electrical switch which is adapted and arranged to be operable to perform a predetermined switching operation only with the cooperation of a security key, the switch comprising a button movable in a predetermined direction to operate the switch to perform said predetermined switching operation, and a blocking member which projects resiliently from the button substantially in said predetermined direction to abut against a fixed surface of the switch thereby to prevent movement of the button in said predetermined direction without the use of a security key, the button comprising an aperture in which an appropriate security key can be inserted to deflect the blocking member away from its abutment against said fixed surface, thereby to release the button for movement in said predetermined direction.

2. A switch according to claim 1, and comprising a further blocking member which projects resiliently from the button substantially in said predetermined direction to abut against a fixed surface of the switch thereby to prevent movement of the button in said predetermined direction without the use of the security key which, when inserted into said aperture, deflects both blocking members away from their abutment against the cooperating associated fixed surface, thereby to release the button for movement in said predetermined direction.

3. A switch according to claim 2, wherein the two blocking members extend side-by-side and are urged away from one another by the security key when it is inserted in the aperture to a position in between the two blocking members.

4. A switch according to any preceding claim, comprising a housing receiving an electrical switching system.

5. A switch according to any preceding claim, wherein the button is mounted on one end of a spring-loaded switch actuating slide.

6. A switch according to claim 5, wherein the button has an inner surface at which is moulded a hub securely containing the one end of the spring-loaded switch actuating slide.

7. A switch according to any preceding claim, wherein the aperture is in a frontal wall of the button.

8. A switch according to any preceding claim, wherein the or each blocking member is moulded onto the inner surface of a front wall of the button.

9. A switch according to any preceding claim, wherein the or each blocking member comprises a shoulder to abut against said fixed surface, thefixed surface being on a mounting plate attached to a housing of the switch.

10. A switch according to claim 2, or any of claims 3 to 9 when appended to claim 2, wherein the blocking members extend slightly towards one another when the security key is not inserted.

11. A switch according to any preceding claim, wherein for the or each blocking member said fixed surface comprises a window through which the blocking member can pass when the security key is inserted, thereby to permit movement of the button in said predetermined direction with the or each blocking member passing through its associated window.

1 2. A switch according to any preceding claim, wherein the or each blocking member comprises a first portion, adjacent the button, having a relatively narrow cross-section and a second portion, connected to the first portion, having a larger cross-section, the first and second portions being interconnected by a portion including a bevel which cooperates with a bevel on a security key when the key is inserted, thereby to achieve the deflection of the or each blocking member away from its blocking abutment with said fixed surface.

1 3. A switch according to any preceding claim, wherein the button comprises two key bit guide ribs at one side of said aperture and a key bit guide rib at an opposite side of said aperture, the space between the ribs corresponding to the thickness and shape of a security key bit.

1 4. A switch according to claim 1 3 when appended to claim 6, wherein said two guide ribs are moulded onto a wall providing part of said hub.

1 5. A switch according to claim 1 3 or 14, wherein the opposite guide rib is moulded onto an inner surface of an outer wall of the button.

16. A switch according to any preceding claim, when in combination with an appropriate security key.

1 7. A switch according to claim 16, wherein the key comprises a head portion, and an engagement means which projects from the key at a distance from the head portion which correspinds substantially to the thickness of a wall of the button defining said aperture, whereby when the key is inserted this wall is sandwiched between the head portion and the engagement means of the key.

1 8. A switch according to claim 17, wherein said engagement means comprises two raised lugs.

1 9. A switch according to claim 1 7 or 18, wherein said engagement means are moulded on a bar portion of the key which is reduced in thickness at the region of the engagement means thereby to promote flexing of the key at this region.

20. A switch according to any preceding claim, wherein the button is plastics.

21. A button-operable electrical switch substantially as hereinbefore described with reference to Figs. 1 to 4 of the accompanying drawings.

22. A button-operable electrical switch according to claim 21 and in operable combination with a security key substantially as hereinbefore described with reference to Figs. 1 to 4 of the accompanying drawings.