Mechanism for an enclosed residual current-operated circuit breaker

Abstract

 A mechanism, for an enclosed residual current-operated circuit breaker, has a relay provided with a piston adapted to act on a tripping mechanism, a handle for resetting the tripping mechanism and for acting on the piston of the relay in order to return it to the normal operating condition, a preadjusted elastic member arranged between the handle and the piston so that the force applied to the piston is set by means of the elastic member and does not depend on the force applied to the handle.

Description

[0001] The present invention relates to a mechanism for an enclosed residual current-operated circuit breaker.

[0002] Residual current devices are adapted to open circuit breakers when an earth fault current exceeds, for the time optionally selected, the threshold value for which the device has been set.

[0003] The residual current device has a relay provided with a piston adapted to act on a tripping mechanism connected to the circuit breaker.

[0004] The relays used in residual current devices are extremely sensitive electromechanical systems and it is necessary to pay great attention during resetting of the mechanism, when one acts on the piston of the relay, in order to avoid damaging the relay.

[0005] The aim of the present invention is to provide a mechanism, particularly for a residual current-operated circuit breaker, that is improved with respect to the mechanisms used so far.

[0006] An important object of the invention is to provide a mechanism in which, during the resetting step, the force applied to the piston of the relay is perfectly calibrated according to specific requirements.

[0007] Another object of the invention is to provide a mechanism that offers the greatest assurance of safety and reliability in operation.

[0008] Another object is to provide a mechanism that is constructively simple and has a small number of components.

[0009] This aim and these and other objects that will become better apparent hereinafter are achieved by a mechanism for an enclosed residual current-operated circuit breaker as claimed in the appended claims.

[0010] Further characteristics and advantages of the invention will become better apparent from the description of preferred but not exclusive embodiments thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein:

Figure 1 is a schematic perspective view of a circuit breaker and of the corresponding enclosed residual current-operated circuit breaker;

Figure 2 is a schematic perspective view of the mechanism according to the invention;

Figure 3 is a perspective view, taken from the opposite side with respect to Figure 2, of the mechanism according to the invention;

Figure 4 is a side elevation view of the mechanism, shown in the normal operating position;

Figure 5 is a side elevation view of the mechanism, shown in the position in which the test button is pressed;

Figure 6 is a side elevation view of the mechanism, shown in a second step of operation after the position in which the test button is pressed;

Figure 7 is a partial enlarged-scale side elevation view of the mechanism shown in the condition in which it has tripped;

Figure 8 is a view, similar to Figure 7, of a first step of the resetting of the mechanism;

Figure 9 is a view, similar to Figure 8, of the mechanism in the reset condition.

[0011] With reference to the above figures, the mechanism according to the invention, generally designated by the reference numeral 1, is particularly usable in a residual current device 2 adapted to open a circuit breaker 3 when an earth fault current exceeds the threshold value for which the device has been preset, in a per se known manner.

[0012] The mechanism 1 of the residual current device is substantially contained in a supporting frame 5 inserted in the body of the device 2 and has a relay 4 provided with a piston 6 which is adapted to act, if tripping occurs, on a release lever 7, which actuates the snap action of a slider 8 pushed by a main release spring 9.

[0013] The device further comprises a system for adjusting the relay 4, which has an adjustment screw 11 that operates in contrast with an adjustment spring 10.

[0014] The residual current device further comprises a test circuit, whose main steps of operation are illustrated in Figures 4 to 6. The test circuit has a test button 12, which is pivoted to the pivot 13 and is adapted to act, when pressed, on a test button spring 14, which makes contact with a test button closure contact 15, as shown in Figure 5.

[0015] The test button spring 14 has a flap 16 which, in the normal operating position of the device, shown in Figure 4, is in contact with a fixed test circuit opening contact 17, but when the test button is pressed, the flap 16 performs a snap action and moves away from the contact 17, interrupting the supply of power to the test circuit, as shown in Figure 6. If a residual current is present, the piston 6 protrudes and, by virtue of the release lever 7, the slider 8 is subjected to a snap action by means of the main release spring.

[0016] Figure 7 is a partial view of the mechanism 1 shown in the tripped position. The mechanism comprises a resetting handle 18, which is pivoted to the frame 5 of the mechanism in the handle pivot 19 and has a coaxial spring 20 adapted to push the handle 18 in the tripped mechanism position. A cross-member 21 acts on the handle 18 and has an end that is pivoted in the handle 18 and a second end that is engaged in a slot 22 of the slider 8 and in a second slot 32 of the engagement lever 7, so that the longitudinal movement of the slider 8, during tripping, leaves free the end of the cross-member in order to allow the handle to turn due to the spring 20.

[0017] The relay is reset by means of the handle 18, which actuates a relay resetting lever 23 by means of a relay resetting spring 24.

[0018] The relay resetting spring 24 is coaxial to the pivot 25 of the relay resetting lever and comprises a first end 27, which is engaged in a slot 26 of the handle 18, and a second end 28, which rests on the relay resetting lever, so that by acting on the handle 18 the action on the resetting lever 23 is mediated by the resetting spring 24 and is not direct. In this manner, the force applied to the piston 6 of the relay is determined exclusively by the adjustment of the resetting spring 24.

[0019] The slider 8, in its longitudinal movement during tripping, actuates contacts 33 having auxiliary functions, while the free end of the slider acts on the release device of the circuit breaker if the residual current device is arranged below.

[0020] If the residual current device is laterally adjacent to the circuit breaker, there is a pin 34 inserted in an appropriate seat of the slider 8.

[0021] In practice it has been observed that the invention achieves the intended aim and objects, a mechanism having been provided which is particularly advantageous in a residual current device and is improved with respect to the mechanisms used so far.

[0022] A particular advantage of the invention is that, during resetting, the force applied to the piston of the relay is perfectly calibrated according to specific requirements.

[0023] The mechanism according to the invention is susceptible of numerous modifications and variations, within the scope of the appended claims. All the details may be replaced with technically equivalent elements.

[0024] The materials used, as well as the dimensions, may of course be any according to requirements and to the state of the art.

Claims

1. A mechanism for an enclosed residual current-operated circuit breaker, comprising a relay provided with a piston adapted to act on a tripping mechanism, a handle adapted to actuate the resetting of the tripping mechanism and to act on the piston of the relay in order to return it to the normal operating condition, characterized in that it comprises a preadjusted elastic member arranged between said handle and said piston so that the force applied to the piston is set by means of said elastic member and does not depend on the force applied to the handle.

2. The mechanism according to claim 1, characterized in that it comprises a release lever on which said piston of said relay acts, said release lever being adapted to actuate the snap action of a slider pushed by a main release spring.

3. The mechanism according to claim 1 or 2, characterized in that it comprises a test circuit that comprises a test button, which is pivoted in a pivot that is rigidly coupled to a supporting frame of the mechanism, and is adapted to act, when pressed, on a test button spring, which makes contact with a test button closure contact.

4. The mechanism according to one or more of the preceding claims, characterized in that said test button spring has a flap which, in the normal operating position of the device, is in contact with a fixed test circuit opening contact, when the test button is pressed, said flap performing a snap action and moving away from the contact, interrupting the supply of power to the test circuit, said piston protruding and, by means of the release lever, producing the snap action of the slider due to the main release spring.

5. The mechanism according to one or more of the preceding claims, characterized in that said resetting handle is pivoted to said frame of the mechanism in a handle pivot and has a coaxial spring that is adapted to push the handle in the tripped mechanism position; a cross-member acting on said handle and having an end that is pivoted in the handle and a second end that is engaged in a slot of said slider, so that the longitudinal movement of the slider during tripping allows the rotation of the handle.

6. The mechanism according to one or more of the preceding claims, characterized in that it comprises a relay resetting lever, which is adapted to act on said piston by way of the actuation of said handle, said preadjusted elastic member being constituted by a relay resetting spring, which is coaxial to a pivot of the relay resetting lever and comprises a first end, which engages a slot of the handle, and a second end, which rests on the relay resetting lever, so that by acting on the handle the action on the resetting lever is mediated by the resetting spring and is not direct.

Drawing