GB2279809A

GB2279809A - A lockable rotary drive for a circuit breaker

Info

Publication number: GB2279809A
Application number: GB9413166A
Authority: GB
Inventors: Wolfgang Kutsche; Volker Heins; Gerd Voiss
Original assignee: Kloeckner Moeller GmbH
Current assignee: Eaton Industries GmbH
Priority date: 1993-07-03
Filing date: 1994-06-30
Publication date: 1995-01-11
Anticipated expiration: 2014-06-30
Also published as: GB9413166D0; ITMI941373A1; ITMI941373A0; DE4322215C2; DE4322215A1; GB2279809B; FR2708377A1; IT1271201B; FR2708377B1

Description

1 A Lockable Rotary Drive for a Circuit Breaker 2279809 The invention

relates to a lockable rotary drive for a circuit breaker. Electric circuit breakers in the form of low voltage switch devices often have a rocking lever which is connected to a switching link, the rocking lever moving between an ON- and an OFF-position. The rocking lever is connected, by way of the switching link of the switch latch, to the movable switching contacts of the circuit breaker by a spring pre- tensioned toggle lever arrangement which opens the contacts and which brings the rocking lever into a RELEASED position in dependency on specific releasing conditions when there is an excess current.

In order to protect the circuit breaker from unauthorised actuation, it is necessary lockably to latch it in the OFF switching position. However, this must not be possible when one or more of the switching contacts is/are welded or - as in the appropriate test - fixed by appropriate means. The operating element can then be brought into the OFF-position by force, but it cannot be locked in that position.

Accordingly, the standard IEC 947 prescribes that, when the contacts are welded or fixed, the operating part or the rocking lever provided therefor or the rotary handle in the case of a manually- actuated rotary drive, if the operating part also indicates the switching position, a) certainly does not reach the OFF position, or, b) when it reaches the OFF- position cannot be locked in that OFF position and clearly leaves the OFF position when the test force is removed again.

Due to the elasticity, the tolerances and the operating principle of the drive system arranged between the rotary drive or rocking lever and the movable switching contacts, in the case of small and average-sized circuit breakers it is not possible to prevent the OFF-position from being reached with the prescribed test force, even with welded switching contacts. Blocking the circuit breaker by means of a fixed abutment member is undesirable and unreliable for two reasons:

Firstly, the switching latch is already blocked by a fixed abutment before the maximum force has been applied to tear open the welded switching contacts. No further forces are transferred by the switching latch to the switching member. Instead, the forces are taken up by a fixed abutment.

If, on the other hand, the switch is operated by a fast motor drive, on each actuation the actuated element strikes against the fixed abutment, which 2 acts as a blocking member, because this latter has not yet released the blocking device due to the inertia of the switch shaft. This results in excessive wear to the motor drive and the blocking device.

In order to prevent the risks associated with the latching of the switch in the OFF-position with welded contacts, it is already known from EP-O 522 848 A2 to provide circuit breakers with a lockable rotary drive, wherein the rotary handle of the rotary drive can only be latched in the OFF-position if a blocking member associated with the rotary handle has previously been placed in a retaining opening fixed in the cover of the housing. Therein, a blocking pin which projects from the blocking member engages in the retaining opening on the housing, so that the blocking member frees an opening on the rotary handle for suspension therefrom of a shackle-type connector, and the rotary handle can thus be fixed in the OFF-position. With this rotary drive, due to the rigid drive transmission to the rocking lever, the rotary handle can however also be brought into the latching position by the application of force when the switching contacts of the circuit breaker are welded or when they are retained in the ON-switching position by other mechanical influences.

With this known rotary drive, the driving is carried out by the rotary handle on the rockable rocking lever on the circuit breaker by a slide member which is guided in a constrained manner on the housing of the rotary drive and which has a drive slot for the rocking lever, wherein a toothed rack sits on the slide member for engagement therein of a sectorshaped toothed segment which is positively connected to the rotary handle by way of a square section bolt.

The manufacture of the slide member with the lateral toothed rack drive which is displaceably guided on the housing bottom of the rotary drive also requires additional manufacturing expenditure. In addition, the slide member can also become jammed, whereas problems can then result when locking the rotary drive, even if the rocking lever of the circuit breaker is properly in the OFF-position.

EP 450 699 A2 discloses another rotary drive with a latching (or locking) lever which can only be brought into the locking position when the associated circuit breaker is really in the OFF-position, the contacts thus actually being open. To this end, with the contacts welded, a load moment is applied to the drive mechanism of the rotary drive by way of the rocking lever of the circuit breaker and by way of a direction- changing drive, with an intermediate member, which can be rotated counter to the force of a spring 3 with a certain amount of clearance, being moved in relation to the drive axis so that a finger of the intermediate member prevents the inner end of the latching lever from engaging in a recess in the drive housing. The drawback with this rotary drive is firstly the need for the intermediate arrangement of a direction- changing drive with a drive system to change over the rotational movement of the rotary drive into a rocking movement for the rocking lever, and secondly that the blocking effect of the intermediate member can be made ineffective, if, prior to the start of the switching off movement, the latching lever is pressed with sufficient force into the locking direction.

The aim of the invention is to design a lockable rotary drive consisting of a small number of functionally safe component parts which are easy to manufacture, in such a way that a blocking element connected thereto can be brought into the blocking position to prevent the rotary drive from being able to be locked with the utmost reliability only if the rocking lever of the circuit breaker is properly in the OFF-position, but not when the switching contacts are welded or retained.

This problem is solved according to the invention by a lockable rotary drive for a circuit breaker, comprising a switch latch which, with switching contacts in a welded or fixed condition, has a pivotable switching link spring-loaded in the ON switching direction and a drive system arranged between the rotary drive and the switch latch, the drive system moving a rocking lever of the switch latch backwards and forwards between the ON and OFF switching positions in response to actuation of the rotary drive, wherein the return force in the ON direction of the switch latch, with welded or fixed switching contacts, serves to prevent the rotary drive from being locked by means of a rotatable intermediate member with free play, wherein the drive system comprises a switching rocker arm which acts as an intermediate member and is mounted for rotational movement to the side of the rocking lever and engages over the rocking lever by means of a drive slot, and a blocking slide member which is displaceable in a plane which is parallel to the carrier slot and has inter-engaging latching means in the form of latching recesses and latching elements which engage into the latching recesses, the drive system being arranged such that at least one of the latching recesses is displaced towards its associated latching element when the switching contacts are welded or retained and when the rotary drive is actuated such that the latching recess in question is blocked for engagement of the latching element, and, as 4 a result, the blocking slide member cannot arrive at its lockable blocking position.

The invention is advantageous in that the rotary drive is reliably prevented from being latched (or locked) by the blocking slide member as soon as only one of the switching contacts of the circuit breaker is welded and thus the rocking lever which is spring pretensioned by the toggle lever drive of the switch latch always springs back from the OFFposition into an intermediate position, even when the rotary drive is actuated with force, and in this intermediate position it is not possible for the blocking slide member to reach its blocking- or latching position.

If one or more switch contacts is/are welded or fixed on a circuit breaker (Test according to IEC 947 Part 3), the switching axle or switching link (or connecting member) of the switch latch which is spring- loaded in the ON switching direction always strives to move back in the ON direction.

If no contact is welded, the return moment is no longer present after the switch latch has moved beyond the change-over point, and the switching axle or switching link automatically adopts the OFF position in which the return moment is equal to zero. This difference in the moments is used to latch the rotary drive.

The switching shaft or switching link can be brought into the OFF position by increased application of force by the rotary drive, so that the maximum amount of force can be transmitted to the movable switching contacts to break the weld. There is no blocking of the force applied.

The use of a fast motor drive for the rotary drive is likewise ensured without any constraint as no fixed abutment blocks the rapid switch-off movement of the circuit breaker and thus the inertia of the switching shaft does not play any role.

The available return moment of the switching shaft or switching link, after the externally applied force (test force) has been removed, brings the operating element or the indicator of the switching position back into a clear position in front of the OFF position.

Suitable mechanical devices can prevent the circuit breaker from being locked in the OFF position with the available return moment and with the welded contacts.

The drawings illustrate a preferred embodiment of the invention, wherein:

Figure 1 is a perspective view of a circuit breaker with a rotary drive on the switch housing, the rotary drive having a lockable latching (or interlocking) device in the ON position of the circuit breaker; Figure 2 is a schematic side view of the circuit breaker with the rotary drive on it, wherein the closed switching contacts and their rocking lever drive are shown purely schematically; Figure 3 is a perspective view corresponding to Figure 1 of the circuit breaker with a locked rotary drive in the OFF position; Figure 4 is a side view, corresponding to Figure 2, of the circuit breaker with a locked rotary drive in the OFF position, wherein here too the opened contacts and their rocking lever drive inside the circuit breaker are shown purely schematically; Figure 5 is a vertical longitudinal section through the rotary drive with a lockable latching device, along the sectional line V - V in Figure 4; Figure 6 is a horizontal section through the rotary drive with a lockable latching device, along the sectional line VI - VI in Figure 5; Figure 7 is another horizontal section through the rotary drive with a lockable latching device, along the sectional line VII - VII in Figure 5, in the open position; Figure 8 is a sectional view, corresponding to Figure 7, through the rotary drive with lockable locking device, in the latching position; Figure 9 is a side view, corresponding to Figures 2 and 4, of the circuit breaker with rotary drive and lockable latching device, with the switching contacts welded; and Figure 10 is a section, corresponding to Figures 7 and 8, through the lockable latching device, along the sectional line X - X, with welded switching contacts according to Figure 9.

Figures 1 to 10 show a lockable manually operated rotary drive 2 for a circuit breaker 3 with a pivotable switching link 4 which is springloaded in the ON/I switching direction, the free end of the switching link having a rocking lever 6 which projects from an opening in the housing 5 of the circuit breaker 3. The rocking lever 6 is adjustable between the various switching positions by means of a drive system 7 (Figures 5 to 10) connected to the rotary drive, with a drive slit 8 which engages over the rocking lever 6. The movable switching contacts 9 of the circuit breaker 3 are actuated in a known manner by the switching connecting member 4 by means of a toggle lever system, not shown.

6 As can be seen in detail in Figures 5 to 10, the rotary drive 2 for the rocking lever 6 has a rotary handle 10 and a lockable latching slide member 11 which cooperates, by way of a slidable blocking slide member 12 displacable transversely to the rocking lever 6. with both the drive system 7 and the rocking lever 6, in such a manner that the latching slide member 11 can only be moved into its latching (or locking) position, with simultaneous displacement of the blocking slide member 12, when two separate latching (or interlock) recesses 13, 14 of the blocking slide member 12 firstly laterally engage over the rocking lever 6 to block it in the OFF/O position and secondly blockingly engage with a latching (or interlock) element 15 on the drive system 7.

To this end, the drive system 7 has a switching rocker arm 16 for the rocking lever 6 which is pivotally mounted about a rotary axle 18 which is arranged perpendicularly to the pivotal axle 17 of the switching link 4 or the movable switching contacts 9 of the circuit breaker 3 and adjacent to the path of movement of the rocking lever 6, and engages over the rocking lever 6 with a substantially X-shaped drive slot 8 with appropriate clearance or free movement 19 in the direction of movement 20 of the rocking lever 6 or switching link 4.

The blocking slide member 12 is so arranged to be moveable backwards and forwards in a plane parallel to the switching rocker arm 16 and perpendicularly to the direction of movement 20 of the rocking lever 6 that, when the circuit breaker 3 is in the OFF or O-position with open contacts 9, the blocking slide member, by means of its first latching recess 13, lockingly engages over the free end of the switching rocker arm 16, oppositely disposed to the rotary axle 18, and by means of its second latching recess 14, simultaneously lockingly engages laterally over the rocking lever 6 (Figure 8), but when the switching contacts 9 are welded (Figures 9 and 10), as a result of the spring-loading 21 of the switching link 4 or of the rocking lever 6 and as a result of the use of the free clearance or free movement 19 at the X-shaped drive slot 8 for the rocking lever 6, the blocking slide member, by means of a transverse edge 22 adjacent to or outside the second latching recess 14 comes into a position laterally on the rocking lever 6 such that the rocking lever 6 prevents lateral displacement of the blocking slide member 12 into the double latching state by the two latching projections 13, 14. Therefore, the blocking slide member 12 is prevented from reaching the 7 left-hand end position for the OFFIO position of the circuit breaker 3, and therefore prevents the rotary drive 2 from being able to be locked.

The blocking slide member 12 is guided on the housing 23 of the rotary drive 2 so that it is longitudinally displaceable on either side of and parallel to the direction of movement 20 of the rocking lever 6, and it has an opening 24 which surrounds the rocking lever 6 with a large clearance, the opening having the transverse edge 22 which extends in the direction of movement 20 of the rocking lever 6 and which is interrupted by the latching recess 14 which engages over the rocking lever 6 in the OFF/0 position.

The free end of the switching rocker arm 16 which is remote from the rotary shaft 18 on the housing 23 of the latching device has a blocking element 15 in the form of a bent latching lug which passes through a circular guide slot 24a in the latching slide member 12, wherein the latching recess 13 for the latching lug is arranged on the guide slot 24a radially outside the latching recess 14 for the rocking lever 6.

The blocking slide member 12 is spring-loaded by a compression spring 25 in the direction of the latching slide member 11, and the latching slide member 11 is held by a compression spring 26 in its rest position in the ON/I position of the circuit breaker 3 according to Figures 1, 2, 6 and 7.

The longitudinal edge 27 of the latching slide member 11 facing the blocking slide member 12 has two compensating pins 29, 30 which project from the front end 28 of the blocking slide member 12 and which cooperate with two mutually parallel inclined surfaces 31, 32 on the front side of the blocking slide member 12 to displace it, and after the blocking position of Figures 3, 4 and 8 has been reached, lockingly engage the front edge 28 of the blocking slide member 12 which is offset correspondingly parallel to the direction of displacement 33 of the latching slide member 11.

The front end of the blocking slide member 12 of the latching slide member 11 is displaceable to an extent delimited by an abutment, against the action of the compression spring 26, and parallel to the direction of movement 20 of the rocking lever 6, and the free end of the latching slide member which projects from the housing 23 away from the switching direction ON/I of the handle 10 has a bent transverse limb 34 with at least one opening 35 for suspension therefrom of one or more lockable blocking means, such as shackle type connectors 36, or the like.

The rotary drive 2 for the rocking lever 6 of the circuit breaker 3 is designed with an eccentric disc 38 which is rotatably mounted to the housing 8 cover 37 by way of the switching rocker arm 16 and the blocking slide member 12, the eccentric disc engaging, by way of a radial guide slot 39, over the free end of the bent locating lug 15 which projects from the end of the switching rocker arm 16.

The housing 23 of the rotary drive 2 is square in design and has a housing bottom 40 which can be positively placed on the switch housing 5 on the rocking lever 6, from which housing bottom two mounting flanges 41, 42 with coaxially oriented mounting elements are bent parallel to each other to provide a pivotal arrangement at corresponding mounting locations 43, 44 on the circuit breaker housing 5.

Instead of the afore-described latching lockable latching device of the blocking slide member 12 by means of the latching slide member 11 it is also possible for the blocking slide member 12 to be provided directly with a lockable latching device, e.g. in the form of a security lock on the housing 23 of the rotary drive 2, the blocking member of which engages on the blocking slide member 12 and latches this latter in the OFF-position of the circuit breaker 3.

9

Claims

1. A lockable rotary drive for a circuit breaker, comprising a switch latch which, with switching contacts in a welded or fixed condition, has a pivotable switching link spring-loaded in the ON switching direction and a drive system arranged between the rotary drive and the switch latch, the drive system moving a rocking lever of the switch latch backwards and forwards between the ON and OFF switching positions in response to actuation of the rotary drive, wherein the return force in the ON direction of the switch latch, with welded or fixed switching contacts, serves to prevent the rotary drive from being locked by means of a rotatable intermediate member with free play, wherein the drive system comprises a switching rocker arm which acts as an intermediate member and is mounted for rotational movement to the side of the rocking lever and engages over the rocking lever by means of a drive slot, and a blocking slide member which is displaceable in a plane which is parallel to the carrier slot and has inter-engaging latching means in the form of latching recesses and latching elements which engage into the latching recesses, the drive system being arranged such that at least one of the latching recesses is displaced towards its associated latching element when the switching contacts are welded or retained and when the rotary drive is actuated such that the latching recess in question is blocked for engagement of the latching element, and, as a result, the blocking slide member cannot arrive at its lockable blocking position.

2. A rotary drive according to Claim 1, wherein, of the two retaining recesses of the blocking slide member, in the OFF switching position when the switching contacts are properly separated a first latching recess engages over a latching element which projects from the switching rocker arm and a second latching recess engages over the rocking lever whereas, when the switching contacts are welded the rocking lever is displaced in the carrier slot of the switching rocker arm laterally in the ONswitching direction towards the second latching recess of the blocking slide member and thus prevents the blocking slide member from arriving at its lockable blocking position.

3. A rotary drive according to Claim 1 or Claim 2, wherein the switching rocker arm is pivotally mounted about a rotary axle arranged perpendicularly to the pivot axis of the switching link or movable switching contacts of the circuit breaker, adjacent to the path of movement of the rocking lever, and engages over the rocking lever with an approximately X-shaped drive slot, having appropriate clearance or free movement in the direction of movement of the rocking lever or switching link, and that the blocking slide member is arranged so that it can move backwards and forwards in a plane which is parallel to the switching rocker arm, perpendicularly to the direction of movement of the rocking lever, such that when the circuit breaker is in the OFF or O-position with the switching contacts open, the blocking slide member, by means of a first latching recess, engages over the free end of the switching rocker arm, oppositely disposed to the rotary shaft, and by means of a second latching recess simultaneously blockingly engages laterally over the rocking lever, whereas when the switching contacts are welded, as a result of the spring- loading of the switching link or of the rocking lever and as a result of the use of the clearance or free movement at the X-shaped drive slot for the rocking lever, the blocking slide member, by means of a transverse edge adjacent to or outside the second retaining recess, comes into a position laterally to the rocking lever such that the rocking lever prevents lateral displacement of the blocking slide member in the double latching state whereby the blocking slide member cannot arrive at the end position for the OFF/O position of the circuit breaker, thereby preventing the rotary drive from being lockable.

4. A rotary drive according to one of Claims 1 to 3. wherein the blocking slide member on the housing of the latching device is guided so that it is longitudinally displaceable on both sides of the rocking lever and perpendicularly to the direction of movement of the rocking lever and has an opening which surrounds the rocking lever with a wide clearance, the opening having a transverse edge which extends in the direction of movement of the rocking lever, the transverse edge being interrupted by a latching recess which engages over the rocking lever in the OFF position.

5. A rotary drive according to one of Claims 1 to 4, the switching rocker arm, at the free end remote from the rotary shaft on the housing of the latching device, has an angled latching lug in the form of a latching element which passes through the blocking slide member in a circular guide slot, and the latching recess for the latching lug is arranged at the guide slot radially outside the latching recess for the rocking lever.

11

6. A rotary drive according to one of Claims 1 to 5, wherein the rotary drive has a lockable latching slide member which cooperates, by way of the blocking slide member which is displaceable transversely to the rocking lever, both with the drive system and with the rocking lever such that the latching slide member is movable into its locking position with simultaneous displacement of the blocking slide member only when the two separate retaining recesses of the blocking slide member, on the other hand lockingly engage laterally over the rocking lever in the OFFIO position and, on the other hand are lockingly engaged with the retaining element of the switching rocker arm.

7. A rotary drive according to Claims 1 to 6, wherein the blocking slide member is spring-loaded in the direction of the latching slide member.

8. A rotary drive according to Claims 1 to 7, wherein the locking slide member, at its longitudinal edge facing the blocking slide member, has projecting compensating pins adjacent to the front end of the blocking slide member, these compensating pins cooperating with inclined surfaces on the front of the blocking slide member to displace this latter, and, after the blocked position has been reached, make locking contact at the front edge, parallel to the direction of displacement of the latching slide member, of the blocking slide member.

9. A rotary drive according to Claims 1 to 8, wherein the latching slide member at the front end of the blocking slide member is displaceable to an extent delimited by an abutment parallel to the direction of movement of the rocking lever against a spring force, and the free end of the latching slide member which projects from the housing of the latching device, away from the switching direction ONII of the rotary handle, has a bevelled transverse web with at least one opening for suspension therefrom of one or more lockable blocking means such as shackle type connectors, or the like.

10. A rotary drive according to one of Claims 1 to 9, wherein the rotary drive for the rocking lever of the circuit breaker is designed with an eccentric disc which is rotatably mounted to the housing cover of the latching device by way of the switching rocker arm and the blocking slide member, and the eccentric disc engages, by way of a radial guide slot, over the free end 12 of the bevelled retaining lug which projects from the end of the switching rocker arm.

11. A rotary drive according to one of Claims 1 to 10, wherein the housing of the latching device is square in design with a housing bottom which can be placed positively onto the switch housing on the rocking lever, from which housing bottom two mounting flanges with coaxial bevelled mounting elements are disposed parallel to each other to provide a pivotal arrangement at the correspondingly designed rotary mounting locations on the switching housing.

12. A rotary device substantially as hereinbefore described with reference to the accompanying drawings.