GB2279810A

GB2279810A - A lockable rotary drive for a circuit breaker

Info

Publication number: GB2279810A
Application number: GB9413171A
Authority: GB
Inventors: Rainer Arenz; Erwin Kuhn; Guido Dedenbach
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: FR2708376A1; ITMI941372A1; IT1271200B; GB9413171D0; ITMI941372A0; HK1003813A1; DE4322214C2; DE4322214A1; GB2279810B; FR2708376B1

Description

p k 2279810 1 A Lockable Rotary Drive for a Circuit Breaker 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 OFFposition 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 locked 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 become jammed, and problems can then result when locking the rotary drive, even if the rocking lever of the circuit breaker is properly in the OFFposition.

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 shaft or coupling shaft 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 directionchanging 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 with a pivotable switching connecting member which is spring-loaded in the ON-switching direction when the switching contacts are welded or fixed and with a drive system arranged between the rotary drive and the switch latch, the drive system moving the rocking lever of the switch latch backwards and forwards between the ON and OFF switching positions in dependency on 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 spring- loaded intermediate member which is rotatable with play in relation to the drive- or coupling shaft, a switching rocker arm mounted for rotational movement laterally adjacent to the rocking lever and engaging over the rocking lever with a drive slot, a blocking slide member displaceable with respect thereto in a parallel plane and a rotary coupling which acts as an intermediate member with inter-engaging latching means in the form of latching recesses and latching elements engaging into them, wherein at least one of the latching recesses is/are, with welded or retained switching contacts and actuated rotary drive, displaced towards the associated latching element and blocked.

4 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 pre-tensioned 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, 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 partial side view, from the right, of a circuit breaker with a rotary drive on the circuit breaker housing, the rotary drive having a lockable latching (or interlocking) device, wherein the mutually cooperating parts of the carrier system are indicated by broken lines between the circuit breaker and the rotary drive; Figure 2 is a plan view of the rotary drive mounted on the circuit breaker, in the ON or I switching position of the circuit breaker; Figure 3 is a part section through the rotary drive along the sectional line III - III in Figure 2; Figure 4 is another part section through the rotary drive along the sectional line IV - IV in Figure 2; Figure 5 is a partial view of the mutually cooperating parts of the rotary drive and of the circuit breaker in the ON or I switching position; Figure 6 is a partial view of the principal cooperating component parts of the rotary drive and circuit breaker in the OFF or "0" switching position; Figure 7 is another partial view of the mutually cooperating parts of the drive system with its associated blocking slide member in the ON or I switching position; Figure 8 is a partial view of the mutually cooperating parts of the drive system with associated blocking slide member in the OFF or "0" switching position; Figure 9 is a disassembled view of a rotary coupling for the rotary drive of the drive system with a helical steel torsion spring; Figure 10 is a view in perspective of a plastics torsion spring for a rotary coupling of this kind; Figure 11 is a partial view of the rotary coupling of the drive system, wherein the rotary drive is turned with the tensioned torsion spring in the OFF switching direction until it meets an abutment; Figure 12 is another partial view of the rotary coupling and associated blocking slide member in the OFF switching position, wherein the switching contacts of the circuit breaker are not welded and the torsion spring aligns both coupling parts of the rotary coupling over the whole of their width with each other, on release of the rotary drive, for the blocking element of the blocking slide member to engage in the radial latching recesses on the rotary coupling; and Figure 13 is another partial view of the rotary coupling and blocking slide member with blocking element, wherein the switching contacts of the circuit breaker are welded or retained, and the switch latch therefore loads the switching rocker arm of the rotary drive, so that when the rotary drive is loaded both coupling parts of the rotary coupling are twisted relative to 6 p i;i each other, opposite the blocking element, in such a way that on release of the rotary drive the blocking element of the blocking slide member cannot engage into the mutually overlapping retaining recesses on the rotary coupling.

Figures 1 to 13 show a lockable rotary drive 2 for a circuit breaker 3 with a switch latch which has a per se known pivotable switching link which is spring-loaded in the ON switching direction and a drive system 7 arranged between the rotary drive 2 and the switch latch in a housing 5 located on the circuit breaker 3, the drive system moving the rocking lever 6 of the switch latch backwards and forwards between the switching positions ON/I and OFF/Oin dependency on actuation of the rotary drive 2. The drive system 7 has a drive member with a drive slot 7 which engages over the rocking lever 6 of the switch latch.

When the switching contacts are welded or retained when the circuit breaker 3 is being tested, the return force of the switch latch serves to prevent the rotary drive from locking by virtue of a switching rocker arm 16 which is mounted for rotational movement about a rotary axle 18, laterally adjacent to the rocking lever 6, and engaging over the rocking lever 6 with its carrier slot, and a blocking slide member 12 which is displaceable parallel thereto being provided with inter-engaging latching means in the form of latching (or interlock) recesses 13, 14 and a latching (interlock) element 15, which engages in them. These are formed such that at least one of the latching recesses 13, 14 is displaced in relation to its/their associated latching element 15, when the switching contacts are welded or retained and by way of a rotary drive 2 actuated by a rotary handle 10 in such a way that the latching recesses 13, 14 are blocked from engagement of the latching element 15, and, as a result, the blocking slide member 12 cannot reach its lockable blocking position.

To actuate the switching rocker arm 16, arranged between that arm and the rotary handle 10 is a rotary coupling 50 with two coupling parts 52. 53 which can be twisted relative to each other, and to an extent delimited by an abutment, against the action of a torsion spring 51. A coupling axle 54 sits on the upper coupling part 53, the coupling shaft having a rotary handle 10 which is fixed thereto. Each of the two coupling parts 52, 53 has an outwardly open latching recess 13 or 14, radial to the coupling axle 54, for the blocking slide member 12 which is displaceable parallel to the switching rocker arm 16 and transversely to the coupling shaf t 54 and provided with the 7 &W 1-4- latching element 15, such that in the OFF-position when the switching contacts are properly separated and when the rotary drive 2 is released according to Figures 8 and 12, the lateral latching recesses 13, 14 of the rotary coupling 50 are oriented congruently to each other by the effect of the torsion spring 51 for engagement of the latching element 15 in the form of a latching lug, whereas, when the switching contacts are welded, and consequently, when the switching rocker arm 16 is loaded by the switch latch counter to the OFFswitching direction, the latching recesses 13, 14 of the two coupling parts 52, 53 are turned relative to each other by the rotary drive 2 which is actuated in the OFF-switching direction, according to Figure 13, and, on release of the rotary drive 2, the return force of the switch latch which acts upon the switching rocker arm 16 turns the coupling parts with respect to the blocking element 15 such that the blocking element 15 is prevented from entering the latching recesses 13, 14.

To this end, the two coupling parts 52, 53 of the rotary coupling 50 have at least two claw members which inter-engage in the direction of rotation with clearance such that axial annular sections 55 of the one coupling part 52 or 53 engage into axial annular recesses 56 of greater length in the direction of rotation on the other coupling part 52, 53 such that the radial latching recesses 13, 14 partly overlap each other when the coupling parts 52, 53 are twisted relative to each other, as shown in Figure 11, with the rotary drive 2 which is turned until final abutment is made in the OFF or "0" switching direction, and as shown in Figure 13 by the actuated rotary drive 2, with welded switching contacts.

The torsion spring 51 between the two coupling parts 52. 53 of the rotary coupling is designed, as shown in Figure 9, as a helically wound steel torsion spring with radial spring legs 57, 58, each of which engages into corresponding radial receiving slots 59, 60 on the two coupling members 52, 53.

However, as shown in Figure 10, it is also possible for the torsion spring 51 to be designed as a polygonal disc-like torsion spring element of plastics material and to be inserted on each of the two coupling parts 52, 53 between appropriately shaped holding means which make positive contact on the torsion spring element.

Therein, the torsion spring 51 consists of a polygonal moulded part which is moulded from plastics material and which has a polygonal central bore 8 61 for a polygonal central pivot which projects from one of the two coupling parts 52 or 53 into a retaining opening on the other coupling part.

With both embodiments, the rotary coupling 50 is connected, by way of a gearwheel drive, to form a drive with the switching rocker arm 16. The gearwheel drive 62 consists of a gearwheel section 63 which sits on the bottom coupling part 52 of the rotary coupling 50, and of an arcuate companion tooth configuration 64 on the switching rocker arm 16.

The blocking slide member 12 is displaceable towards the rotary coupling 50, in the direction of movement of the switching rocker arm 16, and receives the rotary coupling 50 by way of an oval elongate opening 65 which extends in the direction of movement 12a of the blocking slide member 12 (Figures 7 and 8) such that the parallel longitudinal limbs 66. 67 sit on either side of the opening 65. on a cylindrical guide stage 68 on the rotary coupling 50 (Figure g).

In addition, it has a latching element 15, or retaining lug, which engages into the radial latching recesses 13, 14 on the rotary coupling 50, and these latching elements, or latching lugs, are equal in width peripherally to the two latching recesses 13, 14 on the rotary coupling 50.

At the opposite end, the blocking slide member 12 has a tongue portion 69 which projects from the housing 5 of the rotary drive 2, in the blocking position, through a slot 71, the tongue portion having an opening 70 for suspension therefrom of one or more shackle type connectors, or the like.

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Claims

IP 1. A lockable rotary drive for a circuit breaker, comprising a switch latch with a pivotable switching connecting member which is spring-loaded in the ONswitching direction when the switching contacts are welded or fixed and with a drive system arranged between the rotary drive and the switch latch, the drive system moving the rocking lever of the switch latch backwards and forwards between the ON and OFF switching positions in dependency on 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 spring-loaded intermediate member which is rotatable with play in relation to the drive- or couplAng shaft, a switching rocker arm mounted for rotational movement laterally adjacent to the rocking lever and engaging over the rocking lever with a drive slot, a blocking slide member displaceable with respect thereto in a parallel plane and a rotary coupling which acts as an intermediate member with inter-engaging latching means in the form of latching recesses and latching elements engaging into them, wherein at least one of the latching recesses is/are, with welded or retained switching contacts and actuated rotary drive, displaced towards the associated latching element and blocked.
2. A rotary drive according to Claim 1, wherein for actuation of the switching rocker arm, the rotary coupling is arranged between the rocker arm and the rotary handle, the rotary coupling having two coupling parts which can be twisted relative to each other against the action of a torsion spring to an extent delimited by an abutment, wherein each of the two coupling parts has an outwardly open latching recess which is radial to the coupling axle for the blocking slide member which is displaceable parallel to the switching rocker arm and transversely to the coupling axle and is provided with the latching element such that in the OFF- switching position, when the switching contacts are properly separated, and when the rotary drive has been released, the lateral latching recesses of the rotary coupling are oriented so that they are congruent with each other, by the effect of the torsion spring, for engagement of the latching element, wherein, when the switching contacts are welded, and, consequently, when the switching rocker arm is loaded by the switch latch away from the OFF-switching position, the retaining recesses of the coupling parts are turned relative to each other by the rotary drive which is actuated in the P 7L OFF-switching direction, and, on release of the rotary drive, the return force of the switch latch which acts upon the switching rocker arm turns them with respect to the blocking element such that the blocking element is prevented from entering the latching recesses.
3. A rotary drive according to Claim 1 or Claim 2, wherein the two coupling parts of the rotary coupling have at least two claw members which inter-engage with play in the direction of rotation in such a way that axial annular sections of the one coupling part engage in axial annular recesses of greater length in the direction of rotation on the other coupling part such that the radial latching recesses partly overlap each other when the coupling parts are turned towards each other.
4. A rotary drive according to one of Claims 1 to 3. wherein the torsion spring between the two coupling parts of the rotary coupling is formed as a helically wound steel torsion spring with radial or/and paraxial spring legs, each of which engages into corresponding radial receiving slots on the two coupling parts.
5. A rotary drive according to one of Claims 1 to 4, wherein the torsion spring between the two coupling parts of the rotary coupling is formed as a polygonal disc-like torsion spring element of plastics material, and is inserted between holding means which make positive contact thereon, on each of the two coupling parts.
6. A rotary drive according to Claim 5, wherein the torsion spring is formed as a polygonal moulded article of plastics material with a polygonal central opening for a polygonal central pin which projects from one of the two coupling parts of the rotary coupling into a retaining opening on the other coupling part.
7. A rotary drive according to one of Claims 1 to 6, wherein the rotary coupling forms a driving connection with the switching rocker arm by way of a gearwheel drive.

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8. A rotary drive according to Claim 7, wherein the gearwheel drive consists of a gearwheel section which sits on the rotary coupling and an arcuate companion tooth configuration on the switching rocker arm.
A rotary drive according to one of Claims 1 to 8, wherein the blocking slide member is displaceable relative to the rotary coupling in the direction of movement of the switching rocker arm.
10. A rotary drive according to one of Claims 1 to 9, wherein the blocking slide member receives the rotary coupling by means of an oval elongate opening which extends in the direction of movement of the blocking slide member, and by way of the parallel longitudinal limbs on either side of the opening sits on a cylindrical guide stage on the rotary coupling.
11. A rotary drive according to one of Claims 1 to 10, wherein the blocking slide member has a retaining element, or retaining lug, which engages into the radial retaining recesses on the rotary coupling, the retaining element or retaining lug being equal in width peripherally to the two retaining recesses on the rotary coupling.
12. A rotary drive according to one of Claims 1 to 11, wherein, in the blocked position, the blocking slide member has a tongue portion which projects from the housing of the rotary drive through a slot, the tongue portion having an opening for suspension therefrom of one or more shackle type connectors, or the like.
13. A rotary drive substantially as herein before described with reference to the accompanying drawings.