GB2376800A

GB2376800A - Multipole electrical switching device with latch

Info

Publication number: GB2376800A
Application number: GB0214003A
Authority: GB
Inventors: Franz Boeder; Guido Dedenbach; Bogdan Zabrocki; Guido Eifert
Original assignee: Moeller GmbH
Current assignee: Eaton Industries GmbH
Priority date: 2001-06-19
Filing date: 2002-06-18
Publication date: 2002-12-24
Anticipated expiration: 2022-06-18
Also published as: DE10129498C1; FR2826175B1; GB0214003D0; GB2376800B; FR2826175A1; ITMI20021317A1

Abstract

A multipole switching device 2 with switch-position indication contains a multipole contact system 17 with a common interrupter shaft 16 and a latch 18. The latch 18 contains, between stationary side plates 19, a non-positively mounted actuating arm 28, a toggle-lever mechanism with a spring force storing device and a supporting lever (58, Fig. 3). The actuating arm 28 is provided with a rigid counter-stop 66, which after a tripping operation when contacts 34, 36 have not opened properly, comes up against a stop 32 of interrupter shaft 16 under the dynamic action of the spring force storing device.

Description

1 2376800

Description

Multipole electrical switching devices with latch The invention relates to multipole switching devices with a latch, in particular, although not exclusively to, circuit breakers or load-breaking switches for low voltage with switch-position indication.

10 A circuit breaker for low voltage, the operating lever of which is movable within a certain angular range, is known from publication EP0462769-A2. The switching device includes a housing in which a latch, connecting means, a contact system and a release system are arranged. The multipole contact system contains stationary contact arrangements and movable contact arrangements, which are connected across all 15 poles by a transverse interrupter shaft and can be brought into and out of contact with the stationary contact arrangements, thereby making or breaking a continuous electrical connection between the opposite connecting means. The latch consists of an actuating arm, which has tillable mounting in stationary side plates on both sides and projects with an operating lever from an opening in the housing, of a toggle-lever 20 mechanism with an upper toggle lever, a lower toggle lever and a spring force storing device, wherein the toggle levers are hinged together via a toggle-lever spindle, the spring force storing device engages between toggle-lever spindle and actuating arm and the lower toggle lever has a hinged connection to the interrupter shaft, and of a supporting lever housed between the side plates, which on the one hand has a hinged 25 connection to the upper toggle lever and on the other hand can be brought into contact with a release mechanism, whereupon the supporting lever is supported against the release mechanism. The release mechanism is actively connected to an electronic tripping system, which detects the pole currents flowing through the switching device and, when adjustable limits are exceeded, effects a delayed or immediate release of 30 the supporting lever, which under the influence of the spring force storing device leads to tripping of the latch and therefore opening of the contact system. The latch is designed in such a way that the actuating arm assumes a definite ON position when the contact system is closed and a clearly distinguishable OFF position when the contact system has been opened. The lower toggle lever is provided with an

extension, which strikes the interrupter shaft when there is an attempt to move the actuating arm to the OFF position in the case of a movable contact arrangement that cannot be separated from its corresponding stationary contact arrangement - for example when there are welds as a result of a short circuit. This blocks a forcing of 5 the actuating arm to the OFF position, in order to prevent, in particular, a locking of the operating lever in the OFF position when the contacts are not properly opened.

Disadvantages of this solution are, on the one hand, the small force transmitted from the operating lever to the interrupter shaft for breaking the contacts that have not opened properly, and on the other hand that because of the restricted movement of the 10 actuating arm when the contacts are not properly opened, a motor drive or electromagnetic drive connected to the operating lever runs the risk of being damaged. It is obvious to a person skilled in the art that the electronic tripping system can be replaced by a thermomagnetic tripping system.

15 Publication DE-3336207-C3 discloses a circuit breaker with stationary contacts and with movable contacts, which are carried by corresponding arms that are connected together rigidly by means of an interrupter shaft and, in the ON position of the switch, are pressed against the stationary contacts by contact pressure springs, and with an actuating arm that is connected by a toggle-lever system to at least one of the arms, in 20 order to move the arms abruptly by energy storing springs to one of two positions, in which the contacts are either closed or open. The actuating arm, which has positive mounting, is connected rigidly to a part which, in the case of welded contacts, strikes against a corresponding stop element of one of the arms at an intermediate position of the contact gap of the actuating arm and thus prevents movement of the actuating arm 25 to the OFF position. The stop element consists of a profile, which is secured to the corresponding arm carrying a movable contact and has a leg on which the contact pressure springs are anchored, which press the movable contacts against the stationary contacts' Relative to the interrupter shaft, the leg is arranged on the side of the arm opposite to the movable contact. In this solution, the force transmitted to the 30 interrupter shaft for breaking welded contacts is greater than in the aforementioned solution, but it still has the disadvantage that, with the contacts welded, a motor drive or electromagnetic drive connected to the operating lever runs the risk of being damaged.

A circuit breaker of this type with a multipole contact system is known from publication US-3614685-A. The latch consists of an actuating arm with tillable mounting in stationary side plates with an operating lever, of a toggle-lever mechanism with an upper toggle lever, a lower toggle lever and a spring force storing 5 device, and of a supporting lever housed between the side plates. The toggle levers are hinged together via a toggle-lever spindle. The spring force storing device engages between the toggle-lever spindle and the actuating arm. The lower toggle lever has a hinged connection to an interrupter shaft. The interrupter shaft carries movable contact arrangements with single-arm movable contacts that can swivel against the 10 action of contact pressure springs within the so-called travel. The supporting lever has a hinged connection to the upper toggle lever. After a tripping operation the latch can be reset by bringing the supporting lever, by moving the actuating arm to the other side beyond its OFF position, into supporting contact, under the action of the spring force storing device, with a release mechanism that is actively connected to tripping 15 means. The interrupter shaft is provided with a rigid stop element. If, after a tripping process, in at least one pole the contacts do not open on account of welding, the supporting lever is released by the release mechanism and the actuating arm still remains in its ON position. The actuating arm can, because it is mounted exclusively non-positively on account of the spring force storing device, be moved by force 20 towards its OFF position when the contacts are welded. In this case, however, it is not possible to bring the supporting lever back into engagement with the release system, because if there is an attempt to move the actuating arm by force beyond the OFF position, the movement of the supporting lever is limited by coming up against the stop element. After release of the operating lever operated by force, the actuating arm 25 returns to the ON position. In this solution, the circuit-breaking movement of a motor drive or electromagnetic drive connected to the operating lever can, if there is welding of the contacts in the switching device, be performed without damaging the drive.

What must be regarded as a disadvantage is that when the actuating arm is forced into the OFF position only a small force for breaking the welded contacts is transmitted to 30 the interrupter shaft.

The aforementioned disadvantages of the state of the art also occur when the solutions described are transferred to load-breaking switches with or without tripping means.

An object of preferred embodiments of the present invention is therefore to be able to exert a high opening force on contacts when they have not opened properly and to force the actuating arm out of the ON position.

5 Starting from switching device of the type stated at the outset, the object is achieved according to the invention by the characterizing features of the independent claims, whereas advantageous developments are presented in the dependent claims.

Owing to the direct connection of the lower toggle lever and the interrupter shaft, 10 regardless of the degree of wear of the contacts, the actuating arm occupies a precise ON position or a precise OFF position depending on the switching state of the switching device. The precision of the ON and OFF position is particularly advantageous in contact systems that are equipped with contact bridges as movable contacts, because the associated double contact-break distance means that the opening 15 travel is halved and therefore only relatively small interrogation distances are available for the actuating arm opposite the movable contacts. If, after a circuit-

breaking attempt by force (with or without a previous tripping process), not all of the contacts open properly, the counter-stop of the actuating arm meets the stop of the interrupter shaft, and in mild cases this results in breaking of welded contacts. In 20 serious cases at least one contact pair remains unopened, and the actuating arm maintains a position that is clearly distinguishable from the OFF position. If the actuating arm is moved by force to the OFF position in the case of contacts that have not opened properly, the spring force storing device is overstrained by the actuating arm that is mounted non-positively in the side plates and therefore an increased force 25 is transmitted via the counter-stop of the actuating arm onto the stop of the interrupter shaft for forced opening of the contacts that have not opened properly. In an unsuccessful attempt at opening, in particular in the case of failure to break welded contacts, after release of the operating lever the actuating arm can clearly be seen to leave the OFF position under the action of the spring force storing device. With 30 appropriate dimensioning, the non positive, i.e. flexible mounting of the actuating arm protects a motor drive or electromagnetic drive that is connected to the operating lever from being destroyed.

s The solution according to the invention can be used in switching devices that have a tripping latch with a swivellable supporting lever, and in switching devices that have a stationary supporting lever. The first group of switching devices includes circuit breakers and load- breaking switches with tripping means, and the second group of 5 switching devices includes load-breaking switches without tripping means.

An advantageous development of the invention consists of formation of the stop and/or of the counter-stop as a lever arm. As a result, on the one hand the point of impact of the stop and counter-stop can be established in the course of forced 10 movement of the actuating arm, and on the other hand it is possible to achieve a favourable action of force on the interrupter shaft to force open contacts that have not opened properly. It is advisable to limit the movement of the actuating arm beyond the OFF position by a stop on the side plates.

15 In another advantageous development, because of an elastic positive locking between the actuating arm and the switching device housing, in particular its cover part, occurring when the actuating arm is moved to the OFF position by force, an additional breaking force is exerted on welded contacts via the stop and counter-stop.

20 In an advantageous version, the multipole contact system is equipped with a number of doubly interrupting contact bridges, in particular rotatable contact bridges, their number corresponding to the number of poles. In another advantageous embodiment, the interrupter shaft consists of interrupter-shaft sections with connecting elements between them, which are at least partly connected to the lower toggle lever.

Further details and advantages of the invention can be seen from the following exemplary embodiment, which is explained with the aid of Figures, in which: Fig. 1: is an exploded view of a switching device according to the invention; 30 Fig. 2: is an assembled perspective view of the latch and central pole of the contact system of the switching device according to Fig. 1; Fig. 3: is a partially dismantled side view of the latch and central pole in the ON position;

Fig. 4: is a partially dismantled side view of the latch and central pole in the released position with properly opened contacts; Fig. 5: is as Fig. 4, but with welded contacts and released operating lever; Fig. 6: is as Fig. 5, but with operating lever moved by force to the OFF position.

Fig. 1 shows a triple-pole switching device 2 constructed as a lowvoltage circuit breaker and provided with a double housing. For each of the three poles there is a stationary contact arrangement with two stationary contact bars 4 and 6, a movable contact arrangement 8 in the form of a rotationally-symmetrical, swivellable contact 10 bridge and two arc extinguishing chambers 10, which are arranged together in a switch chamber housing, consisting of an upper part 11 and a lower part 12. Each movable contact arrangement 10 is mounted in an interrupter shaft section 14, which in its turn is mounted in the switch chamber housing 11, 12. The three interrupter shaft sections 14 that swivel about an interrupter shaft axis 13 (see Fig. 2) are joined 1 S together by two connecting elements 15 so that they cannot twist. The three interrupter shaft sections 14 and the two connecting pieces 15 form an interrupter shaft 16 that is common to all the poles. The stationary contact arrangements 4 and 6, the movable contact arrangements 8 and the interrupter shaft 16 form the triple-pole contact system 17 of the switching device 2. The construction of this type of contact 20 system and its assembly and mounting in this type of switch chamber housing are described in detail in publication EP1037239A2. The interrupter shaft 16 is coupled to a latch 18, which serves for closing, opening and tripping of the switching device 2 and is arranged above the central pole. The lower part 12, the upper part 11 and the latch 18 are joined together non-positively by common securing means in the form of 25 screws 20 and threaded holes 21, which are arranged in side plates 19 on both sides of latch 18. The switch chamber housing 11, 12 and the latch 18 are arranged in a switching device housing consisting of a bottom part 22 and a cover part 24. The cover part 24 is provided with an opening 26, through which an actuating arm 28, provided with a curved plate 29, of latch 18, projects to the outside with an operating 30 lever 30. In the finished state of the switching device 2, the bottom part 22 is screwed to the cover part 24, and the plate 29 is underneath the cover part 24.

According to Fig. 2 and Fig. 3, the interrupter shaft 16 is provided with a rigid stop 32, which is formed as a projection like a lever arm on one of the connecting pieces

15. The movable contact arrangements 8 that are carried by the interrupter shaft sections 14 are provided at both ends with movable contacts 36, which rest on stationary contacts 34 of contact bars 4 and 6 under the action of contact pressure springs 39. When the switching device 2 changes from the ON to the OFF state, 5 before the actual opening of contacts 34, 36, the interrupter shaft section 14 must travel a distance D, until the striking surfaces 37 of interrupter shaft section 14 meet the opposite striking surfaces 38 of the movable contact arrangement 8. The distance D decreases with increasing wear of contacts 34, 36 and is adjusted by the contact pressure springs 39.

The U-shaped actuating arm 28 of latch 18 is provided, opposite the operating lever 30, with a U-shaped cut-out 40, with which the actuating arm 28, under the action of a spring force storing device 42 in the form of a helical tension spring is mounted non positively and tillable on journals 44, which are fitted to the stationary side plates 19.

15 With the contact system 17 closed, the actuating arm 28 occupies an ON position and with contact system 17 opened it occupies an OFF position or a tripped position, which are displaced clockwise relative to the ON position shown in Fig. 2 and Fig. 3-

The latch 18 contains a toggle-lever mechanism with the spring force storing device 42 and in each case one upper toggle lever 46 and one lower toggle lever 48 arranged 20 on both sides of the spring force storing device 42. The toggle levers 46, 48 are hinged together by means of a toggle-lever spindle 50. The spring force storing device 42 engages with the toggle-lever spindle 50 on the one hand and with the actuating arm 28 below the operating lever 30 on the other hand. The lower toggle levers 48 each have a hinged connection via a first articulated spindle 52 with a connecting 25 piece 15 and therefore with the interrupter shaft sections 14 (see Fig. 1). Other parts of latch 18 include a release mechanism 54 that is actively connected to tripping means that are not shown, and a supporting lever 58 that is pivoted on a bearing spindle 56 between the side plates l9. The supporting lever 58 has a hinged connection, via a second articulated spindle 60, to the upper toggle arms 46. Under 30 the dynamic effect of the spring force storing device 42, the supporting lever 58 bears, via its release surface 62, against a detent 64 of release mechanism 54. In the region of the U-shaped cut-out 40, the actuating arm 28 is provided with a rigid counter-stop 66 in the form of a lever arm.

Fig. 4 shows how, after the occurrence of a fault in the load circuit connected to switching device 2, for example as a result of an overload or a short circuit, the latch 18 has changed to the tripped state and all contacts 34, 36 of contact system 17 have been opened properly. As a result of the tripping operation, the supporting lever 58 5 has been released by the release mechanism 54. The released supporting lever 58 swivels under the action of spring force storing device 42 anticlockwise about its bearing spindle 56, whereupon the toggle-lever system is jerked upwards. The consequence of this is that, on the one hand, the interrupter shaft sections 14 are swivelled clockwise about their interrupter shaft axis 13 by the upward movement of 10 the lower toggle levers 46, and on the other hand, the actuating arm 28 with its operating lever 30 assumes, by tilting about the journals 44, the tripped position as shown, which is between the ON position and the OFF position. As a result of the swivelling ofthe interrupter shaft section 14, after first travailing the distance D (see Fig. 3), the present movable contact arrangement 8 is separated from the 15 corresponding stationary contact arrangement 4, 6. When the contact system 17 opens properly, no contact occurs between the counter-stop 66 of actuating arm 28 and the stop 32 of interrupter shaft 16.

Fig. 5 shows how, after occurrence of a short circuit in the load circuit connected to 20 the switching device 2, the contact system 17 does not open properly, on account of welds between contacts 34, 36. After operation of the actuating arm 28 towards the OFF position, i.e. when the actuating arm 28 swivels clockwise about the journals 44, the togglelever system tries, under the action of spring force storing device 42, to pull the lower toggle levers 48 upwards. The same sequence of movements also takes 25 place after release of the supporting lever 58 as a result of a tripping operation.

Pulling of the lower toggle levers 48 upwards is successful, however, by the movable contact arrangement 8 that is held stationary as a result of welding of the contacts, only as far as travelling the distance D (see Fig. 3) by the interrupter shaft section 14.

As a result of being acted upon with an external torque M in the direction of the OFF 30 position, for example by an operator or a motor drive, the counter-stop 66 of actuating arm 28 impinges on the stop 32 of interrupter shaft 16. If the contacts are lightly welded, this impingement can cause contacts 34, 36 to open, so that the contact system 17 opens properly. Otherwise, the actuating arm 28 and its operating lever 30 remain in the position shown, which is sufficiently different from the OFF position.

Fig. 6 shows the case when, starting from the situation shown in Fig. 5, through impingement with a force F. the actuating arm 28 is forced clockwise, beyond the position according to Fig. 5, to the OFF position. The force F can either be applied 5 manually by an operator or it can be applied by a driving means connected to the actuating arm 28. In this forced movement of actuating arm 28, its lever-like counter-

stop 66 bears upon the lever-like stop 32 of interrupter shaft 16, so that the actuating arm 28 with its U-shaped cut-outs 40 is lifted from the journals 44 against the dynamic action of the spring force storing device 42. The side plates 19 form a 10 limiting stop 68, which limits forcing of the actuating arm 28 beyond the OFF position. In the course of forced movement of actuating arm 28 to the OFF position, its curved plate 29 comes increasingly into mechanical contact with the underside of cover part 24. As a result of the elastic deformation of cover part 24 this produces, an additional dynamic action is exerted via actuating arm 28 by the counter-stop 66 on 15 stop 32, which can possibly break the welded contacts 34, 36.

The flexibility of latch 18 that has been described has two effects: Firstly. when an attempt is made to switch off switching device 2 in which contacts 34, 36 are welded, a driving means that is connected to the actuating arm is protected for a certain time 20 against destruction. Secondly, the dynamic effects acting on the actuating arm 28, produced on the one hand by the spring force storing device 42 and on the other hand by the elastic positive locking between cover part 24 and plate 29, will be transmitted via the counter-stop 66, the stop 32 and the interrupter shaft 16 to the movable contact arrangement 8, which in some cases can lead to breaking of the welded contacts 34, 25 36 and therefore proper opening of the contact system 17. The torque that is then exerted on the movable contact arrangement 8 increases with progression of the forced movement of actuating arm 28 to the OFF position. After release of the operating lever 30 of the actuating arm 28 that has been moved by force to the OFF position, the actuating arm returns, under the action of the spring force storing device 30 42 and the elastic recovery of the cover part 24, to the position according to Fig. 5, so that the improper opening of the contact system 17 is clearly indicated. In addition, devices are known, for example according to publication EP0450699A2, which prevent the locking of a switching device when the contacts are not properly opened.

With a supporting lever 58 fixed between the side plates 19 by an additional securing spindle 57 (cf. Fig. 3), we have a switching device according to the invention, the latch of which cannot be tripped, so that the tripping means and release mechanism are superfluous. With this solution as well, when contacts 34, 36 have not opened 5 properly, a high opening force is exerted, and forced movement of actuating arm 28 from the ON position to the OFF position is made possible.

The present invention is not limited to the embodiment described above, but also includes all embodiments having the same effect in the sense of the invention. Thus, 10 the invention can for exurnple be modified so that a contact bridge capable of linear displacement or a single-arm, swivelling contact arm is used as the movable contact arrangement. 15 List of reference numbers: 2 switching device 4, 6 stationary contact arrangement 8 movable contact arrangement 20 10 arc chamber 1 1, 12 switch chamber housing 13 interrupter shaft axis 14 interrupter shaft section 15 connecting piece 25 16 interrupter shaft 17 contact system 1 8 latch 19 side plates 20, 21 securing means 30 22, 24 switching device housing 26 opening 28 actuating arm 29 plate 30 operating lever

32 stop 34 stationary contact 36 movable contact 37; 38 striking surface S 39 contact pressure spring 40 cut-out 42 spring force storing device 44 journal 46 upper toggle lever 10 48 lower toggle lever 50 toggle-lever spindle 52 first articulated spindle 54 release mechanism 56 bearing spindle 15 57 securing spindle 58 supporting lever 60 second articulated spindle 62 release surface 64 detent 20 66 counter-stop 68 limiting stop D distance F force 25 M torque

Claims

1. A multipole electrical switching device, such as circuit breakers or load-breaking switches with tripping, with 5 - a switching device housing consisting of a bottom part and a cover part, - a multipole contact system, consisting of stationary contact arrangements with stationary contacts, a common interrupter shaft provided with a rigid stop and movable contact arrangements carried by the interrupter shaft with contacts that can swivel against the action of contact pressure springs 10 - and a latch, consisting of an actuating arm, which on the one hand is provided with an operating lever and on the other hand is mounted substantially non positively in stationary side plates under the action of a spring force storing device and occupies an ON position when the contact system is closed, but an OFF position when contact system is opened, a toggle-lever mechanism with 15 at least one upper toggle lever, at least one lower toggle lever and the spring force storing device, the toggle levers being hinged together via a toggle-lever spindle, the spring force storing device engages between the toggle-lever spindle and the actuating arm and the lower toggle lever has a hinged connection to the interrupter shaft, and a supporting lever housed in the side 20 plates, the said supporting lever has a hinged connection to the upper toggle lever and can be brought into supported contact with a release mechanism under the action of the spring force storing device, the said release mechanism being actively connected to tripping means, wherein - the actuating arm is provided with a rigid counter-stop, which comes up 25 against the stop of the interrupter shaft when contacts have not opened properly and forced movement of actuating arm to the OFF position has occurred with the dynamic action of the spring force storing device.

2. A multipole electrical switching device, such as a load-breaking switch without 30 tripping, with - a switching device housing consisting of a bottom part and a cover part, - a multipole contact system, consisting of stationary contact arrangements with stationary contacts, a common interrupter shaft provided with a rigid stop and

movable contact arrangements carried by the interrupter shaft with contacts that can swivel against the action of contact pressure springs and a latch, consisting of an actuating arm, which on the one hand is provided with an operating lever and on the other hand is mounted substantially non 5 positively in stationary side plates under the action of a spring force storing device and occupies an ON position when the contact system is closed, but an OFF position when contact system is opened, a toggle-lever mechanism with at least one upper toggle lever, at least one lower toggle lever and the spring force storing device, the toggle levers being hinged together via a toggle-lever 10 spindle, the spring force storing device engages between the toggle-lever spindle and the actuating arm and the lower toggle lever has a hinged connection to the interrupter shaft, and a supporting lever fixed between the side plates, the said supporting lever having a hinged connection to the upper toggle lever, wherein 15 - the actuating arm is provided with a rigid counter-stop, which comes up against the stop of the interrupter shaft when contacts have not opened properly and forced movement of actuating arm to the OFF position has occurred with the dynamic action of the spring force storing device.

20

3. A switching device according to claims 1 or 2, wherein the stop and/or the counter-stop are in the form of a lever arm.

4. A switching device according to any one of the previous claims, wherein the side plates form a limiting stop for the actuating arm to limit its movement beyond the 25 OFF position.

5. A switching device according to any one of the previous claims, wherein when the actuating arm is moved by force to the OFF position it comes into mechanical contact with the elastically deformable cover part.

6. A switching device according to any one of the previous claims, wherein the movable contact arrangements are in the form of contact bridges.

7. A switching device according to the claim 6, wherein the contact bridges have pivoted mounting in the interrupter shaft.

8. A switching device according to any one of the previous claims, wherein the 5 interrupter shaft consists of interrupter shaft sections assigned to each pole land connecting pieces arranged between them, connected to the lower toggle lever.

9. A switching device substantially as described herein, with reference to the drawings hereof.

is