GB2172144A

GB2172144A - Improvements in or relating to switch latches

Info

Publication number: GB2172144A
Application number: GB08530112A
Authority: GB
Inventors: Wilhelm Wessling; Norbert Schulz; Martin Beck; Horst Fedder
Original assignee: Felten and Guilleaume Energietechnik AG
Current assignee: Felten and Guilleaume Energietechnik AG
Priority date: 1985-03-07
Filing date: 1985-12-06
Publication date: 1986-09-10
Also published as: DE3508110A1; GB2172144B; DE3508110C2; GB8530112D0

Abstract

The closing speed of the contacts in, e.g. an earth-leakage circuit breaker is increased by means of a latching arrangement. Member (3) bearing the moving contact is clockwise rotatable by means of a manually operable switch knob and is connected via linkages (5) and (7) to a shaft (8) bearing a disc (9) which rollingly engages a spring-loaded locking element (13). The locking element (13) holds the shaft (8) in such a.position that the full clockwise rotation of member (3) is prevented and the contacts remain open. As increasing force is applied to the switch knob energy is stored in the operator's hand and in "play" and elastic deformation in the system. When a selectable surmounting force is reached, the locking element (13) is swung back against the spring and the disc (9) rolls out of engagement therewith, the stored energy ensuring rapid completion of closing of the contacts. <IMAGE>

Description

SPECIFICATION Improvements in or relating to switch latches The invention relates to a switch latch, for instance of the type comprising a switching mechanism for control by a switch knob for increasing the closing speed of electrical contacts of a low voltage switching device.

A switch for a switch latch of this type is disclosed in published German Application No 30 31 005. In this arrangement, an actuating member in the form of a rotating knob engages with two springs. One of the springs already acts through its arm, at the beginning of movement of the rotating knob in a clockwise direction, upon a stop pin of the switching apparatus casing rigid with the casing. In this way, the spring can be tensioned up to its maximum spring force. After reaching the highest switch-on resistance of this spring, the arm of the spring slides off the stop pin and the switch-on resistance rapidly falls, thus ensuring additional torque for increasing the switch-on speed. However, a relatively expensive design is necessary, for which purpose it is essential to change the switch hood and the rotating knob in order to accommodate the individual parts for the switch latch.

According to one aspect of the invention, there is provided a switch latch as defined in the appended claim 1.

It is thus possible to provide a switch latch of the type described above such that the required increase in the closing speed of the contacts of the associated switching device is achieved without changing parts and can readily be fitted in existing switching apparatus.

The increase in the closing speed can essentially be achieved by two components, namely by a resilient locking element and a disc. The disc may already be present in the latch and the locking element can be fitted as a subsequently fitted component in existing switching apparatus without great difficulty and without special aids. Unnecessary frictional losses are avoided by allowing the disc to roll on an attachment of the locking element.

Preferred embodiments of the invention are defined in the appended sub-claims.

By the selection of springs for the locking element, the surmounting force can be varied over a wide range, so that a wide clearance is available for the requirements.

The spring for the locking element can also be dispensed with entirely, by making this component inherently resilient.

According to another aspect of the invention, there is provided a switch latch as defined in the appended claim 6.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front view of a switch latch constituting a preferred embodiment of the invention with the front latch plate removed, in the off position; Figure 2 is a side cross-sectional view on line I-I of Figure 1; Figure 3 is a front view of the switch latch of Figure 1 with the front latch plate removed, in the on position; and Figure 4 is a cross-sectional view on line IV IV of Figure 3.

As shown in Figures 1 to 4, a contact member 3 mounted on a switch knob shaft 2 is associated with a switch latch. A switch knob (not shown) can be secured to the switch knob shaft in order to be able to rotate the contact member in a clockwise direction against the force of a spring 4. The contact member is articulated on an intermediate member 5 which is joined to two further intermediate members 6 and 7 in a bell-crank arrangement. The intermediate member 6 is directly connected to a catch 11 by way of a hinged joint, whereas the intermediate member 7 directly embraces a switch shaft 8 which is movable in an elongate hole 10 of a rear latch plate 18 as viewed from the front. Between the rear latch plate and the intermediate member 7 the switch shaft is surrounded by an annular disc 9.A locking element 13 can be swung out against the force of a spring 16 about an axis of rotation constituting a spring pin 19 between the rear latch plate 12 and a front latch plate 17. An attachment 14, ending in a circular profile 15 which faces the disc 9 and on which the disc can roll, is integral with or rigidly connected to the locking element. A lever arrangement 12 cooperating with the catch 11 is pivotable about an additional rotary shaft.

The mode of operation of the switch latch shown in Figures 1 to 4 is as follows: In order to reach the on position from the off position, the contact member 3 is turned in a clockwise direction by means of the switch knob. The switch shaft 8 is moved in the elongate hole 10 in the switch-on direction by way of the intermediate members 5 and 7. In this connexion, the disc 9 is brought towards the attachment 14 of the locking element 13.

The contacts of the associated switching device are not yet closed in this position, but are just about to close. The pre-stressed locking element 13 holds the switching shaft 8, which effects the transfer to the contacts of the switching device, by way of the disc 9 up to a selectable switch-on force on the switch knob. Increasing the switch-on force on the switch knob results in storage of energy in the hand of the operator and of energy on account of the available play in the system by "tilting" the switch shaft 8 and of energy by resilient deformation. When the selectable "surmounting force" has been reached, the pre-stressed locking element 13 is swung out and is rolled into the disc 9 of the switch shaft 8 on the attachment 14 of the locking element. When the pre-stressed locking element 13 is accordingly swung out, the disc 9 is disengaged from the attachment 14 and drives the switch shaft 8 on account of the release of the previously stored energies in the switch on direction and produces a sudden switch-on of the contacts of the switching device.

By increasing the switch-on speed, the contacts are rapdily closed, thereby considerably reducing the risk of contact burn. This also ensures a prolonged life of the associated switching device.

Claims

1. A switch latch comprising a switching mechanism for control by a switch knob for increasing the closing speed of electrical contacts of a low-voltage switching device, the switching mechanism comprising a contact member for actuation by the switch knob having a bell-crank arrangement which is formed by intermediate members and which is connected to a switch shaft for actuating the contacts of the switching device, the switch shaft being movable in an elongate hole of a rear latch plate and surrounded by the annular disc, the bell-crank arrangement being further connected to a catch so that, as the switch knob is actuated, the switch shaft is held by a spring-loaded locking element until a predetermined switch-on force is reached, thereby increasing the switch-on force and resulting in storage of energy in the hand of the operator on account of the available play in the switch shaft and of energy on account of resilient deformation, and so that, after the predetermined force has been reached, the locking element is swung out, the disc rolls on the locking element and becomes disengaged from the locking element, the switch shaft is suddently released on account of the release of the previously stored energies in the switch-on direction, the contacts are suddenly switched on, and the switching mechanism is locked in this position by a catch.

2. A switch latch as claimed in claim 1, in which the locking element comprises an elongate part which is disposed in the longitudinal direction of the latch plate and is rotatable about a spacing pin in the region of the shaft of the switch knob, and the locking element is provided on its side facing the bell-crank lever arrangement with an attachment which ends in a circular profile which faces the disc and the radius of which is slightly less than the radius of the disc.

3. A switch latch as claimed in claim 1 or 2, in which the locking element is provided with an exchangeable spring for setting the predetermined switch-on force.

4. A switch latch as claimed in claim 1 or 2, in which the locking element and the attachment are formed by an inherently resilient component.

5. A switch latch substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

6. A switch latch comprising a rotatable input shaft, a laterally displaceable shaft, a linkage for displacing the displaceable shaft in response to rotation of the input shaft, a disc rotatably mounted on the displaceable shaft, and a cam surface urged towards the disc, so that the disc rolls on the cam surface, the cam surface being curved towards the path of displacement of the displaceable shaft and being movable so as to release abruptly the disc from engagement with the cam surface.

7. A switch including a switch latch as claimed in any one of the preceding claims.