GB2180403A

GB2180403A - Quick-break switch

Info

Publication number: GB2180403A
Application number: GB08620184A
Authority: GB
Inventors: Edwin Czarnetzki
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co OHG
Priority date: 1985-09-09
Filing date: 1986-08-19
Publication date: 1987-03-25
Also published as: FR2587139B1; GB8620184D0; DE3532055A1; GB2180403B; FR2587139A1

Abstract

A quick-break switch comprises a contact pair (2), a contact surface (12) which establishes a current- carrying contact (14) between the contacts of the contact pair and which can be brought into two end positions by means of a swivelling switching arm (3) and a snap switch mechanism (4) which is connected with the switching arm (3), on the one hand, and with an actuating device (5), on the other hand. So as to ensure a reliable and quick making of contact without bouncing of the contacts, the quick change-over is effected by a change in the position of the actuating device (5) with respect to the switching arm (3), the contact force acting between the contact surface and the contact pair being independent of the change in the position of the actuating device and being constant. <IMAGE>

Description

SPECIFICATION Quick-break switch This invention relates to a quick-break switch with a contact pair and with a contact surface which establishes a current-carrying contact between contacts of the contact pair and which can be brought into either of two end positions by means of a swivelling switching arm communicating with an actuating device via a snap switch mechanism.

A quick-break switch is known, for example, from British Patent Specification (GB-PS) No.

773,712. In this known switch a movable contact is fastened to a leaf spring having a longitudinal bridge portion separated from the remaining part of the lead spring by slots running in parallel with the longitudinal sides of the leaf spring. When there is a sudden change-over brought about by a deformation of the bridge portion of the leaf spring the movable contact will strike an opposite fixed contact.

As this striking action will be extremely quick the movable contact will only come to rest and provide a definite making of contact after several bounces. Said bouncing greatly depends on the actuating speed and can have a negative influence on the life of the switch in case of heavy loads.

A further disadvantage of such switches consists in that the force urging the movable contact against the fixed contact mainly depends on the switch actuating force which thus must be kept as great as possible. Further said force is not constant but decreases as the actuating distance advances.

It is thus an object of the present invention to provide a switch of the said type wherein the above-listed disadvantages will largely be avoided. The switch should have a simple design and allow easy series production. It should permit easy adjustment or regulation and comprise components manufacturable at low costs. Further, the changeover action should occur within a very small period (msec range).

According to the present invention there is provided a quick-break switch with a contact pair and with a contact surface which establishes a current-carrying contact between contacts of the contact pair and which can be brought into either of two end positions by means of a swivelling switching arm communicating with an actuating device via a snap switch mechanism, characterised in that the quick change-over is brought about by a change in the geometric position of the actuating device with respect to the switching arm and in that the contact force (FK) acting between the contact surface and the contact pair is independent of the change in the position of the actuating device and is constant.

Thanks to a simple and reliable design the inventive switch achieves a switching behaviour characterised by a hysteresis. That means that in a first relative position of the actuating device in respect of the switching arm, which will correspond to the distance covered by the actuating device, the switch will change over while during a following movement of the actuating device in the opposite direction, it will not switch back again when said first position is passed but will rather be switched back only when a second position is passed.

According to an advantageous embodiment of the invention the contact pair is formed by two adjacent leaf springs insulated with respect to each other, the elastic prestress of said leaf springs providing the constant magnitude of the contact force.

In a further preferred embodiment a stop is provided for the switching arm, said stop being adjustable from the outside. This will result in a particularly simple way of regulating and adjusting the desired differential distance between the change-over positions, that is the first and second positions referred to above.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a section through a switch of the invention, said switch being in its "ON" position; Figure 2 is the top view of the arrangement of a contact pair together with a printed circuit board of the Figure 1 embodiment, and Figure 3 is a graphical representation of the switch's switching behaviour characterised by a hysteresis.

The switch shown in Figures 1 and 2 comprises a housing 1 wherein a contact pair 2 formed by two leaf springs 20, 21, a switching arm 3, as well as a snap switch mechanism are arranged. In the illustrated example, said snap switch mechanism is formed by a prestressed tension spring 4. Tension spring 4 is hooked with one of its ends to a suitable pin 18 fastened at the switching arm 3 below a contact surface 12. The other end of the tension spring 4 is hooked into a loop 19 fastened at a sliding element 7 of an actuating device 5. The lower fastening point of the tension spring 4 in the loop 19 constitutes a point of reference of the actuating device 5.

The meaning of said point of reference will be explained in more detail in connection with the mode of operation of the inventive switch.

The actuating device 5 displaceably arranged in the lower part of the housing 1 has an actuating rod 6 communicating with the sliding element 7. A cylindrical recess 9 is provided in the sliding element's 7 front face averted from the actuating rod 6. Said cylindrical recess 9 receives one of the ends of a compression spring 10. The other end of said compression spring 10 supports itself in a recess 11 of the wall of the housing 1. The compression spring 10 provides the resetting force required for the return of the actuating device 5.

The switching arm 3 which is supported in the housing 1 so as to swivel around a pivot 17 has an arched plastics contact surface 12 at its end. Said arched plastics contact surface 12 has a printed circuit board 14 at one of its longitudinal edges. On the one hand, a stationary stop 15, e.g., designed in one piece together with a housing wall and, on the other hand, an adjustable stop 16 are provided to limit the swivelling motion of the switching arm 3. Said stop 16 is formed by a set screw screwed into a threaded bore in the opposite housing wall. Upon actuation of the switch, the sliding element 7 will move along a guideway 30 in the housing 1. On said guideway 30 there are two switch points X1, X2 important for the operation of the switch, the meaning of said points being explained in more detail further below.

In the following, the mode of operation of the inventive switch will be explained in connection with Figure 3 showing the switch's switching behaviour characterised by a hysteresis, reference being made to the diagrammatic illustration of the dependence of respectively the contact force FK and the angular position of the switching arm 3 on the distance SB covered by the actuating device 5.

These explanations start from the rest positon of the system which is shown in Figure 1.

The actuating device 5 is in its first end position corresponding to the ON position of the switch.

The printed circuit board 14 establishes an electrically conducting contact between the leaf springs 20, 21 and the arched contact surface 12 is kept against the stationary stop 15 by the action of a retaining force which equals that constituent of the spring force of the prestressed tension spring 4, which acts in this direction.If at the actuating rod 6 an advancing movement of the actuating device 5 is initiated to the left along the guideway 30, the angie enclosed between the longitudinal axis of the tension spring 4 and the central axis of the switching arm 3 will diminish until that moment when the first switch point X1 is reached by the actuating device's 5 point of reference mentioned in connection with the arrangement of the tension spring 4, the switching arm 3 abruptly changes its position, the contact surface 12 abuts against the adjustable stop 16, and the electrically conducting contact of the leaf springs 20, 21 is interrupted.Considering the friction existing between the contact pair 2 and the printed circuit board 14 the first switch point X, will not be exactly in the point of intersection of the central axis of the switching arm 3 and the guideway 30, but will be offset by a slight amount to the left. During this change-over the angular amount M, will also abruptly change to the minimum value.,,=0. (Section 12-3-X, in Figure 3). The contact force FK acting between the contact pair 2 and the contact surface 12( and illustrated by the broken line in Figure 3) will remain unchanged, and this is independently of the change in the distance of the actuating device 5.The contact surface 12 now will support itself at the adjustable stop 16 whose position in respect of the switching arm 3 determines the second end position ("OFF" position) of the switch, which is illustrated by the broken line in Figure 1.

As regards the resetting movement of the actuating device 5 which will be initiated by the action of the spring force of the compression spring 10 the change-over will be analogous, thus the switching arm 3 reaching its original first end position only at that moment when the second switch point X2 will have been reached by the actuating device's 5 point of reference mentioned in connection with the arrangement of the tension spring 4. At that moment the angular amount again will reach its maximum M, (section X,-X2-1 in Figure 3).

The offset position of the second switch point X2 in respect of the point of intersection of the central axis of the switching arm 3 and of the guideway 30 again is due to the friction between the contact pair 2 and the contact surface 12.

By using the adjustable stop 16 it is possible to change the switching hysteresis of the switch, said hysteresis corresponding to the differential distance, i.e., to the distance of the switch points Xz, X2. As the set screw is advanced into the interior of the housing 1 there will be a change in the position of the second switch point X2 which will approach the first switch point X, and thus will diminish the differential distance.

Claims

1. A quick-break switch with a contact pair and with a contact surface which establishes a current-carrying contact between contacts of the contact pair and which can be brought into either of two end positions by means of a swivelling switching arm communicating with an actuating device via a snap switch mechanism, characterised in that the quick changeover is brought about by a change in the geometric position of the actuating device (5) with respect to the switching arm (3) and in that the contact force (FK) acting between the contact surface (12) and the contact pair (2) is independent of the change in the position of the actuating device (5) and is constant.

2. A switch as claimed in claim 1, characterised in that the actuating device (5) is arranged so as to be relatively displaceable with respect to the switching arm (3).

3. A switch as claimed in claim 1, characterised in that the snap switch mechanism is formed by a tension spring (4) one of the ends of which is connected with the switching arm (3) and the other end of which is connected with the actuating device (5).

4. A switch as claimed in claim 3, characterised in that the one end of the tension spring (4) is hooked to a pin (18) fastened at the switching arm (3), the other end of the tension spring (4) being hooked into a loop (19) which forms a part of a sliding element (7) of the actuating device (5).

5. A switch as claimed in claim 1, characterisd in that the contact pair (2) is formed by two adjacent leaf springs (20, 21) insulated with respect to each other, the elastic prestress of said leaf springs (20 21) providing the contact force (FK).

6. A switch as claimed in any one of the preceding claims, characterised in that a stop (16) is provided which is adjustable from the outside of the switch and which serves to adjust the distance between those positions of the actuating device at which change-over occurs.

7. A quick-break switch substantially as herein described with reference to and as illustrated in the accompanying drawings.