GB2207284A

GB2207284A - Key-disabled membrane switch

Info

Publication number: GB2207284A
Application number: GB08816121A
Authority: GB
Inventors: Rudolf Schmeykal; Johannes Haftmann
Original assignee: TA Triumph Adler GmbH
Current assignee: TA Triumph Adler GmbH
Priority date: 1987-07-24
Filing date: 1988-07-06
Publication date: 1989-01-25
Anticipated expiration: 2008-07-06
Also published as: SE464380B; GB2207284B; DE3724530C1; CH675926A5; JPS6441129A; SE8802422L; IT1217895B; JPH0658772B2; FR2618592A1; GB8816121D0; SE8802422D0; IT8821071A0

Description

2 1r12T 7 2 8 4 1; - 1 Key-operated switch for electrical or electronic

equipment This invention relates to key-operated switches for electrical or electronic equipment. Such key-operated switches serve to secure a machine or equipment against unauthorized use. Such a keyoperated switch is known, for example, from German petty patent 19 04 276. Since socalled foil (or membrane) keyboards are gaining increasing acceptance on modern equipment, for example typewriters, the use of known key-operated switches is very extravagant and therefore expensive. In particular, electrical conductors have to be taken to the switch contacts, which also means additional expenditure on assembly. It is the object of the invention to provide a key- operated switch which can also be used with membrane keyboards.

In accordance with the invention there is provided a key-operated switch for electrical or electronic equipment in which the switch contacts comprise a pair of membrane contacts which are normally spaced apart and are actuated by means of a spring loaded contact pin which can be locked in its inactive position by means of a control member which can be actuated by the lock cylinder of the switch.

This arrangement has the advantage that two is membrane contacts can also be used as switch contacts. Thus no separate contacts or conductors need to be provided for the key-operated switch. Simple assembly results from the cooperation of the control member with the contact pin of the key-operated switch since the contact pin is part of the key-operated switch.

Preferably the control member is in the form of a wedge-shaped lug which can be inserted between the switch foils and the contact pin.

Because of the wedge shape of the lug, a problem-free and reliable cooperation results between this and the contact pin. If the lug is pushed in between the contact pin and the contact point of the membrane, by turning the key, the contact pin can be prevented, in a simple manner, from actuating the contact. The switch can be integrated with a keyboard, with the advantage that there is no need to provide separate fastening elements for the switch or current leads. It is immaterial what kind of keyboard is involved. The arrangement and development of a keyoperated switch according to the invention is possible in the keyboard of a typewriter, of a computer, of a cash register as well as in the keyboard of a telephone apparatus.

one form of switch in accordance with the invention will now be described by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a perspective illustration of a key-operated switch, the individual parts being illustrated in an exploded view; and Figure 2 shows a partial plan view of a keyboard.

The drawings show a key-operated switch 1 which can be actuated by means of the key 2. A i 3 j control member 4, which comprises a lug 5 in the embodiment shown, is rotatable with the lock cylinder 3. In order to ensure that the control member 4 is reliably entrained by the lock cylinder 3, a square (or other non-circular) hole 6 is provided in the control member 4, in which hole there engages a square pin, not visible in the drawing of the lock cylinder 3. Also provided on the key-operated switch 1, parallel to the axis of the lock cylinder 3, is a contact pin 7 which is acted upon by a spring (not shown), in the direction of the arrow A.

Membrane (or foil) contacts are provided in known manner on the membranes 8 and 9, a known spacer being disposed therebetween. In the switching region 10, the spacer has an aperture, so that when pressure is is applied to the switching region 10, the membranes and hence their contacts are so deformed that the contacts touch. This means that the above-mentioned spring of the contact pin 7 must be made so strong that it can press the membrane 8 so far through that its switch contact is applied against the other switch contact of the membrane 9, through the spacer.

When the lock cylinder 3, and with it the control member 4, is turned in the direction of the arrow B by means of the key 2, the lug 5 is interposed, as a result of its wedge shape, between the membrane 8 and the contact pin 7, which is thus lifted to such an extent that the bent membrane 8 returns to its initial position, and the contacts are separated in the switching region 10 so that the circuit is interrupted. Since the lug 5 of the control member 4 is made larger than the aperture in the spacer between the membranes 8 and 9, the contact cannot be closed so long as the lug 5 covers the switching region 10.

It may be mentioned here that the construction of the control member 4 with the lug 5 is only one of 1 - 4 many conceivable examples. Nevertheless, it is an extremely low-cost construction which thus enjoys a particular advantage.

In Figure 2, a keyboard 11 is seen which is inserted in a frame 13 and consists of the keys 12. At the bottom left, the key-operated switch 1 of Figure 1 is shown by way of example in place of one of the keys 12. In this case, the membrane keyboard 8/9 can likewise be secured to the frame 13 of the keyboard 11. As already mentioned, this development has the advantage that no separate contacts have to be provided for the key-operated switch 1.

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Claims

CLAIMS:

1. A keyoperated switch for electrical or electronic equipment in which the switch contacts comprise a pair of membrane contacts which are normally spaced apart and are actuated by means of a spring loaded contact pin which can be locked in its inactive position by means of a control member which can be actuated by the lock cylinder of the switch.

2. A key-operated switch according to claim 1, wherein the control member is in the form of a wedgeshaped lug which can be inserted between the switch membranes and the contact pin.

3. A key-operated switch according to claim 1 or 2, wherein switch is integrated with a keyboard.

4. A key-operated switch substantially as herein described with reference to the accompanying drawings.

Published 1988 at The Patent Office. State House. 66 771 High Holborn. London WC1R 4T.P. further copies inay be obtained d from lhe Patent Office, Sales Branch, St Mary Cray. Orpington, Ken' BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray. Kent Con. 1 87