GB2037080A - Push-button keyboard switch - Google Patents

Abstract

Several adjacent circuits on a printed-circuit board (1) are arranged to be connected by at least one push key (7) which is provided with laterally arranged projections (3). At least one resiliently deformable component, preferably in the form of a coil spring (2), running along the circuits is supported by supports (4) extending from the printed circuit board (1) at a spacing from the contact areas (6) of the circuits. The arrangement is such that, when a push key (7) is depressed, the coil springs (2) are pressed by the laterally arranged projections (3) of the push key onto the contact areas (6) of the related circuits whereby an electrically conductive connection is made. The springs (2) are preferably silver plated and are fixed onto pins (5) at their ends. The p.c.b. (1) may have recesses to receive supports (4) and pins (5) which are moulded on the inside of a casing (not shown) and also serve to secure the board therein. <IMAGE>

Description

SPECIFICATION Programming keyboard The invention relates to a programming keyboard more particularly for devices in communications, in which several adjacent circuits can be connected to a common electrical connection via push keys related to the circuits and provided with laterally arranged projections.

Programming keyboards of this type, as used for example in sets of press keys of television sets, have in the past had electrically conductive leaf springs for switching on one of the actuated circuits associated with the push keys. These leaf springs may be brought out of their position of rest into connection with contact pins with the aid of trip cams. Even if the leaf springs are constructed in one piece they must be individually readjusted on assembly, since it can not be assumed that all of the contact springs have the desired switching and contact characteristics.

The present invention aims to provide a programming keyboard which is cheap to manufature and which takes up the smallest possible space.

According to the invention, there is provided a programming keyboard in which several adjacent circuits are arranged to be connected by at least one push key, the or each push key being provided with laterally arranged projections, wherein the adjacent circuits are arranged in the form of a printed circuit on a printed circuit board and at least one resiliently deflectable component running along the circuits is supported by supports extending from the printed circuit board at a spacing from the contact areas of the circuits; the arrangement being such that, when the or a push key is depressed, the resiliently deflectable component or components is/are pressed by the laterally arranged projections of the push key onto the contact areas of the related circuit(s) whereby an electrically conductive connection is made.

The or each resiliently deflectable component preferably comprises a coil spring which may be coated with silver. Thus, the coil spring is pressed by the laterally arranged projections on the press key onto the contact areas of the relevant circuit when a respective push key is actuated, and it therefore makes an electrically conductive connection. By pressing the desired push key, the lateral projections on the push key press the coil spring in such a mannerat double contact is achieved between the contact areas of the relevant circuit and of the coil spring. This arrangement has the further advantage that, when pressing the coil spring(s) onto the contact areas of the relevant circuit, the contact areas of the coil springs and the contact areas of the relevant circuit clean themselves.

According to one embodiment of the invention, the or ditheach coil spring is fixed by placing it on cylindrical pins inserted into the printed circuit board.

According to another ambodiment of the invention, recesses are provided in the printed circuit board and the said board is fixed in a casing by placing it on the supports which are moulded on the inside of the casing, said supports extending through the recesses in the board, and the or each coil spring is fixed by placing it onto pins which are also moulded on the inside of the casing.

The invention will now be further described, by way of example, with reference to the drawings, in which: Figure 1 is a section through one embodiment of a programming keyboard in accordance with the invention taken along the line A-B in Fig. 2; and Figure 2 is a plan view of a portion of the programming keyboard shown in section in Fig. 1.

Referring to the drawings, adjacent circuits having contact areas 6 are printed onto a printed circuit board 1. The conducting paths of the printed circuit are clearly shown in Fig.

2. Two coil springs 2 are passed along via the contact areas 6 of the circuits in the form of resiliently deflectable components and are fixed at their ends by placing them onto cylindrical pins 5 which are inserted into or passed through the printed circuit board 1.

The coil springs 2 are electroplated with silver to achieve better electrical conductivity and are electrically conductively connected in each case at the fixing points to the pins 5 on a conductive track of the printed circuit board 1. They are retained by several supports 4 inserted into the printed circuit board 1 at a spacing from the contact areas 6 of the circuits.

Projections 3 are arranged laterally on push keys 7 and apply a slight prestress to the two coil springs 2 in position 3, to maintain said springs in contact with the support 4. When pressing the push keys 7 into the position 32 the coil springs are pressed onto the contact areas 6 of the circuits such that, for each contact path, electrically conductive connection between the respective coil spring and the contact areas 6 of the relevant circuit is made, said connection being formed from double contacts. Each push key 7 can be retained in thetposition 32 by means of a respective locking device (not shown) and it only returns to position 3, on actuation of an adjacent push key 7.

The printed circuit board 1 may be mounted in a casing (not shown) and in this case the supports 4 may be moulded on the inside of the casing and extend through apertures or recesses in the printed circuit board to secured said board in position in the cas ing. The pins 5 may also be moulded on the inside of the casing.

Claims (5)

1. A programming keyboard in which several adjacent circuits are arranged to be connected by at least one push key, the or each push key being provided with laterally arranged projections, wherein the adjacent circuits are arranged in the form of a printed circuit on a printed circuit board and at least one resiliently deflectable component running along these circuits is supported by supports extending from the printed circuit board at a spacing from the contact areas of the circuits; the arrangement being such that, when the or a push key is depressed, the resiliently deflectable component or components is/are pressed by the laterally arranged projections of the push key onto the contact area of the related circuit(s) whereby an electrically conductive connection is made.

2. A programming keyboard according to Claim 1, wherein the or each resiliently deflectable component comprises an electrically conductive coil spring.

3. A programming keyboard according to Claim 2, wherein the or each coil spring is coated in silver.

4. A programming keyboard according to Claim 2 or Claim 3, wherein the or each coil spring is fixed by placing it on to cylindrical pins inserted into the printed circuit board.

5. A programming keyboard according to Claim 2 or Claim 3, wherein recesses are provided in the printed circuit board and the said board is fixed in a casing by placing it onto the supports which are moulded on the inside of the casing and wherein the or each coil spring is fixed by placing it on to pins which are also moulded on the inside of the casing.