GB1578274A

GB1578274A - Electrical contact mechanism

Info

Publication number: GB1578274A
Application number: GB2471677A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1978-04-04
Filing date: 1978-04-04
Publication date: 1980-11-05

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRICAL CONTACT MECHANISMS (71) We, STANDARD TELEPHONES AND CABLES LIMITED, a British Company of 190 Strand, London W.C.2. England., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to electrical contact mechanism such as may be used in microswitches, limit switches, push button and toggle switches.

According to the present invention there is provided an electrical contact mechanism wherein a leaf spring has two separated points along its length located by stationary fulcra in such a way that the portion of the leaf spring between the two fulcra is held in longitudinal compression such that the leaf spring can be switched, wherein the switching is effected by causing the leaf spring to be snapped from being bowed in one direction to being bowed in the opposite direction, wherein the leaf spring is extended beyond one of the fulcra so as to have an extension portion aligned with and extending beyond that one of the fulcrum, and wherein the extension portion of the leaf spring controls electrical contact means formed by, or carried by, that extension portion, which contact means is moved into or out of electrical contact with an associated stationary contact dependant on the direction in which the portion of the leaf spring between the locating fulcra is bowed.

Embodiments of the present invention will now be described with reference to the drawings accompanying the provisional Specification, in which: Figures 1 and 2 show alternative forms of electrical contact mechanisms embodying the invention.

Figure 3 is a contact arrangement usable with the mechanism of Figure 5 or 6.

Figures 4 and 5 are further contact mech am sins embodying the invention, Figure 6 shows a further contact arrange ment, Figures 7 and 8 show alternative forms of mechanisms for activating the electrical contact mechanisms.

Referring to Figure 1 a leaf spring 10 is held in longitudinal compression between a portion 11 of a housing for the contact mechanism and a further portion 12. The portion 11 has a groove in which one end of the leaf spring is engaged. The portion 12 carries a fulcrum member 13 with a groove which the leaf spring 10 engages such that length-wise movement through the fulcrum member is not possible. For this purpose the fulcrum member may thread a slot in the leaf spring so placed that the end of the spring is in the groove. Alternatively the leaf spring may pass through a slot in the fulcrum member and may have shoulders wider than the slot so that they engage the groove on both sides of the slot. In each case the distance between the base of the groove in the portion 11, and that in the fulcrum member 13 is less than the length of the portion of the leaf spring lying between the slot or soulders and the end engaged in the groove. Therefore the leaf spring is bowed in either in the manner indicated by solid lines in Figure 1 or in the manner indicated by the broken lines.

The free end of the leaf spring carries an electrical contact 14 which forms the movable contact of the mechanism. In one of the bowed states of the leaf spring this movable contact 14 is held agaisnt a co-operating stationary contact 15, while in the other bowed state it is held against a second co-operating stationary contact 16. These stationary contacts may be carried on reeds such as 17 providing a certain measure of compliance. If changeover contact operation is not required, one or other of the stationary contacts may be dispensed with.

If either or both of the two grooves supporting the leaf spring in longitudinal compression are made of relatively non-hard wearing material such as plastics material, they may be lined with a harder-wearing material such as a metal insert (not shown).

In an alternative form of electrical contact mechanism of Figure 2 the right-hand half of the mechanism is identical with that of the mechanism of Figure 1. The left-hand half is different, and is a mirror image of the righthand half, thereby providing a symmetrical mechanism with two further stationary contacts.

Figure 3 shows anothel form of contact usable at the end of a leaf spring, (a) and (b) being two cross-sections thereof, taken at right angles to each other In this, the end 20 of the leaf spring is wrapped round a cylindrical member 21 the end plates 22, 23 of which are metallic for contact makil g. The body portion 24 consists of one of two (as shown) insulating bushes. When such an arrangement is used with fixed contact pins (see Figure 5 and 6) this enables the contacts at the ends of the leaf spring to be insulated from each other.

Figure 4 is a simpler contact end portion usable with the arrangements of Figures 5 and 6, when insulation between the ends is unnecesaary.

In Figure 5, in which the two ends of the spring are identical, the cylindrical contact portion 30 at one end co-operates with three stationary pin contacts, 31,32, and 33. As shown, in one position the contact portion 30 on the spring bridges pins 31 - 32 or 32 - 33 dependent on the positions of the leaf spring.

Figure 6 has its right-hand end similar to the end of the leaf spring in Figure 5, while its left hand end has a rolled-up portion 35, similar to that shown in Figure 4 in a groove in the housing member 36. The loins 37 and 38 shown dotted are intendetl to limit the travel of the leaf spring, so that they define its two rest positions.

The leaf springs in the devices of Figures I, 2, 5 and 6 are switched between two positions in snap-action manner by push-buttons or other forms of operation and two methods of operating such devices will now be described.

Figure 7 shows two positions of a pushbutton type of arrangement for operating the mechanism. The buttons (not shown) have a shank 40 with a recess in which the leaf spring is received. The left-hand portion of Figure 7 shows the device at rest with the leaf spring in the position 41 indicated, thus there is a slight pre-travel before the leaf spring starts to move. The dotted portion 42 shows the position at which the leaf spring starts to snap over, and when it does so it snaps to the position 43 in the right-hand portions Figure 7. The push-button movement is against the urgence of the spring 44.

On release of the push-button, the spring 44 drives the shank upwards and here also there is a short pre-travel before the shank causes movement of the leaf spring. When it reaches the dotted position it snaps over to the rest position 41.

Figure 8 is in general similar to Figure 1 with an operating mechanism formed by two roughly parallel pivotted levers 46 and 47, these are controlled by a forked member with rollers at its end. When the mechanism is moved down the rollers cause lever 46 to bear on the leaf spring to cause snap-over, and on release, lever 47 causes the snap action return to the position shown.

The operating device can be a push-button with a return spring, as in Figure 7.

WHAT WE CLAIM IS: 1. An electrical contact mechanism wheres a leaf spring has two separated points along its length located by stationary fulcra in such a way that the portion of the leaf spring between the two fulcra is held in longitudinal compression such that leaf spring can be switched, wherein the switching is effected by causing the leaf spring to be snapped from being bowed in one direction to being bowed in the opposite direction, wherein the leaf spring is extended beyond one of the fulcra so as to have an extension poriton aligned with and extending beyond that one of the fulcra, and wherein the extension portion of the leaf spring controls electrical contact means fonned by, or carried by, that extension portion, which contact means is moved into or out of electrical contact with an associated stationary contact dependant on the directions in which the portion of the leaf spring betweer the locating fulcra is bowed.

2. A mechanism as claimed in claim 1 and wherein one end of said leaf spring is received in a groove in support means for the mechanic said groove providing one of said fulcrum.

3. A mechanism as claimed in claim 1 or 2, and wherein an end of the spring passes through a slot in a stationary member, which slot provides a said fulcrum, the slot being shorter than the width of the leaf spring but the spring having shoulders which engage the sides of the slot.

4. A mechanism as claimed in claim 1 or 2, and wherein and end of the spring has a slot through which passes a stationary member so as to form the fulcrum.

5. A mechanism as claimed in claim 3 or 4, as appended to claim 1, wherein both ends of the spring are similarly supported.

6. A mechanism as claimed in any one of claims 1 to 5, and wherein the or each end of the spring has an extension which carries said contact.

7. A mechanism as claimed in any one of claims 1 to 6, and wherein the or each said contact includes a cylinder of conductive material having circular end plates, the end of the spring being bent over said cylidner.

8. A mechanism as claimed in any one of claims 1 ot 6, and wherein the or each said contact si a bent-over end of the leaf spring.

9. A mechanism as claimed in any one of claims 1 to 8, wherein the changeover of the mechanism from its rest to its operated position is effected by a push-button which sits on the leaf spring between its end, and wherein on relase of the push-button the mechanism returns to rest.

10. An electrical contact mechanism, substantially as described with reference to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. mechanism with two further stationary contacts. Figure 3 shows anothel form of contact usable at the end of a leaf spring, (a) and (b) being two cross-sections thereof, taken at right angles to each other In this, the end 20 of the leaf spring is wrapped round a cylindrical member 21 the end plates 22, 23 of which are metallic for contact makil g. The body portion 24 consists of one of two (as shown) insulating bushes. When such an arrangement is used with fixed contact pins (see Figure 5 and 6) this enables the contacts at the ends of the leaf spring to be insulated from each other. Figure 4 is a simpler contact end portion usable with the arrangements of Figures 5 and 6, when insulation between the ends is unnecesaary. In Figure 5, in which the two ends of the spring are identical, the cylindrical contact portion 30 at one end co-operates with three stationary pin contacts, 31,32, and 33. As shown, in one position the contact portion 30 on the spring bridges pins 31 - 32 or 32 - 33 dependent on the positions of the leaf spring. Figure 6 has its right-hand end similar to the end of the leaf spring in Figure 5, while its left hand end has a rolled-up portion 35, similar to that shown in Figure 4 in a groove in the housing member 36. The loins 37 and 38 shown dotted are intendetl to limit the travel of the leaf spring, so that they define its two rest positions. The leaf springs in the devices of Figures I, 2, 5 and 6 are switched between two positions in snap-action manner by push-buttons or other forms of operation and two methods of operating such devices will now be described. Figure 7 shows two positions of a pushbutton type of arrangement for operating the mechanism. The buttons (not shown) have a shank 40 with a recess in which the leaf spring is received. The left-hand portion of Figure 7 shows the device at rest with the leaf spring in the position 41 indicated, thus there is a slight pre-travel before the leaf spring starts to move. The dotted portion 42 shows the position at which the leaf spring starts to snap over, and when it does so it snaps to the position 43 in the right-hand portions Figure 7. The push-button movement is against the urgence of the spring 44. On release of the push-button, the spring 44 drives the shank upwards and here also there is a short pre-travel before the shank causes movement of the leaf spring. When it reaches the dotted position it snaps over to the rest position 41. Figure 8 is in general similar to Figure 1 with an operating mechanism formed by two roughly parallel pivotted levers 46 and 47, these are controlled by a forked member with rollers at its end. When the mechanism is moved down the rollers cause lever 46 to bear on the leaf spring to cause snap-over, and on release, lever 47 causes the snap action return to the position shown. The operating device can be a push-button with a return spring, as in Figure 7. WHAT WE CLAIM IS:

1. An electrical contact mechanism wheres a leaf spring has two separated points along its length located by stationary fulcra in such a way that the portion of the leaf spring between the two fulcra is held in longitudinal compression such that leaf spring can be switched, wherein the switching is effected by causing the leaf spring to be snapped from being bowed in one direction to being bowed in the opposite direction, wherein the leaf spring is extended beyond one of the fulcra so as to have an extension poriton aligned with and extending beyond that one of the fulcra, and wherein the extension portion of the leaf spring controls electrical contact means fonned by, or carried by, that extension portion, which contact means is moved into or out of electrical contact with an associated stationary contact dependant on the directions in which the portion of the leaf spring betweer the locating fulcra is bowed.

the drawings accompanying the provisional Specification.