GB2055249A

GB2055249A - Electric circuit breakers

Info

Publication number: GB2055249A
Application number: GB8017451A
Authority: GB
Original assignee: Dorman Smith Switchgear Ltd
Current assignee: Dorman Smith Switchgear Ltd
Priority date: 1979-07-17
Filing date: 1980-05-28
Publication date: 1981-02-25
Also published as: GB2055249B

Abstract

Stem 21 of an indicator element, separate from the circuit breaker operating member 15, in the form of a plunger 20, has its front end 38 exposed at the front face of wall 23 of the circuit breaker housing 10 to provide visual indication of the trip condition of the breaker which is determined by the condition of a toggle linkage to which the plunger 20 is pivotally connected by way of a bistable lever 26. Optionally, the breaker has secured thereto a motorised actuator 39 which acts on operating dolly 15 by way of a carriage 45. A slide 52 serves to indicate, through a window 53, whether the dolly 15 is in the "on" or "off" position. A sensor peg 55 senses the position of the plunger 20 and is effective, upon tripping of the breaker, to bring a tongue or flag 69 into a position masking the slide 52 from the window 53 and providing at the latter an indication that the breaker is tripped. <IMAGE>

Description

SPECIFICATION Electric circuit breaker This invention concerns electric circuit breakers.

In manually-operable circuit breakers, it is usual to provide a manually-displaceable member, such as a dolly, which can be shifted between the "on" and "off" positions. The position of the dolly naturally would be expected to provide, therefore, a visual indication of the condition of the circuit breaker. However, in practice, when such a circuit breaker is tripped, it is not unusual for the manually-displaceable member to assume an intermediate position which is normally midway between the on and off positions. Thus in general the condition of the circuit breaker, whether "on", "off" or "tripped", may be readily determined by visual observation.

Visual indication of breaker condition is not generally possible, however, where the circuit breaker has fitted to it a motorised actuator which enables the breaker to be actuated mechanically, e.g. from a remote point. Such an actuator normally has two basic conditions corresponding to the "on" and "off" positions of the dolly of the circuit breaker. Accordingly, if the circuit breaker should be tripped whilst its dolly is held in the "on" position by the actuator, the dolly will remain in such "on" position. Thus, visual inspection of the actuator, or any indicator which may be provided thereon, can give a false indication of the condition of the circuit breaker.

An object of this invention is to provide a construction of electric circuit breaker having a form of indicator means which can be used to provide a visual indication of the condition of its internal tripping mechanism, the arrangement being such that said circuit breaker can be fitted with a motorised actuator with the indicator means cooperating with means incorporated in the actuator for similarly providing an indication of the condition of the mechanism of the electric circuit breaker.

Pursuant hereto, the present invention provides an electric circuit breaker characterised by tripcondition indicator means separate from a manually-displaceable member of the breaker and including an element having an indicator face exposed at a front face of a housing of the circuit breaker, and resilient means serving, when the circuit breaker is in its nontripped condition, to urge the element towards a normal disposition and being adapted, upon tripping of the breaker, to move the element into a second disposition indicative that the breaker has been tripped.

With the construction of the invention, when the circuit breaker is in use without a motorised actuator, the element provides a visual indication of the condition of the tripping mechanism of the breaker, in addition to that of the dolly.

The said element is conveniently in the form of an axially-displaceable plunger a front end of which constitutes the indicator face.

The arrangement is preferably such that in the normal position, the said front end is flush with or nearly flush with the front face of the housing, and in the second position the said end is withdrawn inwardly of the housing. With such an arrangement, when the plunger is in its normal position, e.g. with its said end visible by reason of its being flush with or nearly flush with the front surface of the cricuit breaker's housing, the said mechanism is in its nontripped condition; when the plunger is in its second position, e.g.

withdrawn so that its said end is inwardly displaced from its flush position and no longer visible, the tripping mechanism is in its tripped condition.

In the arrangement of the invention, the said resilient means preferably comprises a bi-stable spring-loaded lever system adapted to be shifted from a first stable position, corresponding to the normal position of the element, to a second stable position, corresponding to the second position of the element, upon tripping of the breaker.

The construction of the circuit breaker is conveniently such as to include a tripping mechanism including a pivoted trip latch which is released upon tripping of the breaker and which then permits the resilient means to displace the plunger into the second position.

As has already been mentioned, the arrangement of the invention is such as to enable a motorised actuator to be assembled to the circuit breaker, and means on the latter to provide the visual indication of the circuit breaker's condition. Accordingly, the invention further provides a circuit breaker as aforesaid and having a motorised actuator assembled thereto to overlie the front face of the housing of the breaker, said actuator including a sensor engaging the indicator face of the element and serving to provide, at a convenient location on the actuator (e.g. at the front thereof) a visual indication of the trip condition of the breaker.

The actuator preferably incorporates a display indicative of the on and off condition of the actuator, the sensor serving, upon tripping of the breaker, to obscure the display to provide a visual indication that the breaker is in its tripped condition.

The invention further includes within its scope, of course, the actuator as aforesaid, independently of the circuit breaker.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a fragmentary sectional side elevation illustrating a preferred embodiment of the electric circuit breaker of the invention with a motorised actuator fitted thereto, the section corresponding approximately to the line I-I of Fig. 2; and Fig. 2 is a front view of the circuit breaker of Fig. 1, with the motorised actuator removed and part of the front of the housing of the circuit breaker omitted or removed to permit certain of the interior components to be seen.

In the figures of the drawings, for ease of understanding the invention, various of the circuit breaker's components have been omitted.

As shown, the preferred embodiment of the electric circuit breaker of the invention comprises a housing, indicated generally by the reference numeral 10, of insulating material and having, for each pole of the breaker, a moving contact arm assembly, indicated generally by the reference numeral 1 1, carrying a moving contact 12 which cooperates with a respective fixed contact 1 3.

Where the circuit breaker is a multi-pole circuit breaker, the moving contact arm assemblies 11 are coupled together to move in unison, and a pivoted dolly 14, having a handle 15 projecting through a slot in the front of the housing 10 is coupled with the assembly or assemblies 11 by way of a spring-loaded toggle linkage (not shown).

The dolly 14 is shown in the "on" position corresponding to the toggle linkage being in its straightened condition and the moving contact arm assembly or assemblies 11 in the "on" position with the moving contact(s) 12 engaging the fixed contact(s) 13. Movement of the dolly 14 to the "off" position by pivoting it downwards, manually, from the illustrated position, causes the toggle to collapse, and the contact arm assembly or assemblies 11 to swing away from the fixed contact(s) 13, to open the circuit(s) through the circuit breaker.

A main trip latch 1 6 of a tripping mechanism provides support for one of the pivots of the toggle linkage just referred to, and in the non-tripped condition of the breaker this latch 1 6 is (as shown) engaged by its nose and 1 7 under a pivoted retainer 18. Upon passage through the pole (or one of the poles) of the circuit breaker of a shortcircuit current or a sustained overload, a trip bar 19 is pivoted, by appropriate means (not shown), and serves to cause the retainer 1 8 to release the latch 1 6. The latch 1 6 being released, the toggle linkage between the dolly 14 and the moving contact arm assembly or assemblies 11 is collapsed and cannot straighten.The breaker is then in the tripped condition, with the moving contact(s) 12 separated from the fixed contact(s) 13.

For resetting the circuit breaker after it has been tripped, the dolly 14 has to be moved firstly to the "off" position to cause the nose end 17 of the latch 1 6 to engage under the retainer 1 8.

Thereafter, upon the dolly 14 being shifted back to the illustrated "on" position, provided the fault which caused tripping has now been eliminated, the toggle linkage is straightened to cause contact closure once again.

As so far described, the circuit breaker corresponds generally to known constructions. In accordance with the invention, however, the breaker comprises indicator means which not only can provide, at the front of the circuit breaker housing 1 0, a visual indication of the trip condition of the circuit breaker independently of the position of the dolly 14, but can also cooperate with a display arrangement provided in a motorised actuator 39 (to be described later) even though, when tripped, the dolly 14, is held by the actuator in the ON position which maybe misleading to anyone checking the breaker.

This indicator means comprises an indicator element in the form of a plunger 20, having a reduced diameter stem portion 21 guided in an opening 22 through front wall 23 of the housing 10 and having a shoulder 24 facing the inner surface of the front wall 23. This plunger 20 is pivotaily connected, at its inner end, by a pivot 25, to a first flat plate-like lever 26 which forms part of a bi-stable resiliently-loaded lever system and which is swingably mounted, by a pivot 27, alongside an adjacent fixed circuit breaker mechanism side plate 28.A spring 29 extends between a peg 30 projecting from the lever 26, and a laterai lug 31 on a second plate-like lever 32 whose plane is substantially parallel with that of the lever 26 (see Fig. 2). This second lever 32 is fixed by pegs 33 to a bracket 34, composed of a plurality of laminations for strength and manufacturing convenience, this bracket 34 also having a pivot stub 35 projecting from it to engage in a hole in a second circuit breaker mechanism side plate 36. It will thus be understood that the lever 32 is swingable about the pivot axis provided by the opposing holes in the two mechanism side plates. A locator peg 37, projecting from the bracket 34 cooperates with the latch 16, engaging the latter adjacent the nose end 1 7 but at the end of the latch away from the nose.

In the illustrated condition of the circuit breaker, that is to say with the tripping mechanism in its non-tripped state, the dolly 14 in the on position, the plunger 20 is in a normal position which is an extended position abutting by its shoulder 24 against the inner surface of the-front wall 23 of the housing 10 so that its front end face 38, which constitutes an indicator face, is flush with or nearly flush with the front surface of the front wall 23 of the housing 10.

When the motorised actuator 39 is not present, the presence of the front end face or indicator face 38 of the plunger 20 flush with the front surface, or nearly so, as just described, is indicative of the tripping machanism being in its said non-tripped condition, and it will readily be understood that the tripping machism remains untripped, and the plunger remains in its illustrated extended position when the dolly 14 is shifted by hand to the "off" position.

In the event of the circuit breaker tripping, as previously explained, the nose end 1 7 of the latch 1 6 is released by the retainer 1 8. Accordingly, when viewed as in Fig. 1, the latch 1 6 is able to swing through a limited angle about its pivot 40 in a clockwise direction. Since the peg 37 of the bracket 34 abuts the latch 16, this movement of the latch 1 6 permits the bracket 34 also to pivot in a clockwise direction about the axis of the pivot stub 35, and the second plate 32 pivots correspondingly, with the upper part of said plate 32, including the lug 31, moving to the right as viewed in Fig. 1.As soon as the line of action of the spring 29 moves past an imaginary line through the axis of the pivot 27 and the peg 30, the spring 29 acts to pivot the first plate 26 in an anticlockwise direction about the pivot 27, until it is arrested by abutting against an adjacent mounting base 41 of the circuit breaker mechanism. This movement of the first plate 26 results in the plunger 20 being withdrawn inwardly relative to its illustrated position to a second or withdrawn position. This withdrawn position, wherein the end face 38 of the plunger 20 is no longer flush with the front face of the front wall 23 of the housing 10, and is therefore not readily visible, is indicative of the mechanism of the breaker being in the tripped condition.It will readily be understood that upon the breaker being reset, the latch 1 6 shifts the bracket 34 and second lever 32 back to the illustrated positions, thereby causing the line of action of the spring 29 to move back past the line through the pivot 27 and the peg 30 and the first lever 26 to be swung positively back to its illustrated position and the plunger 20 to be restored to its flush position.

As already mentioned, the plunger 20 can serve to provide a visual indication, in addition to that available from the dolly 14, of the trip-condition of the circuit breaker when motorised actuator 39 is not present. The actuator 39, however, incorporates means which cooperates with the plunger 20 to ensure that such visual indication is still provided when the actuator 39 is fitted.

The actuator 39, as shown, comprises a casing 42 which is secured to the front wall 23 of the housing 10 by way of mounting blocks 43 and which encloses guide rails 44 upon which runs a carriage 45 driven by an electric motor (not visible) adapted to be controlled e.g. from a remote location. A pair of pegs 46 on the carriage are spaced apart sufficiently for the handle 1 5 of the dolly 14 to enter there-between, and it will readily be understood that upon the carriage 45 being driven downwards from the illustrated position the dolly 14 will be moved to the "off" position. A spring 47 is secured by one end to a peg 48 fixed to a mounting plate 61 and by its other end to a peg 49 at the remote end of a lever 50 pivoted at 51 to the mounting plate 61.The lever 50 in turn is connected to an indicator slide 52 which is visible through a window 53 in front wall 54 of the casing 42. As the carriage 45 moves the dolly 14 to the "off" position, a projection 70 engages with a formed end 72 of slide 52 and the lever 50 is switched across with a snap action to move a part of the slide 52, bearing the word "off" into register with the window 53.

Upon return of the carriage 45 to the illustrated position and of the dolly 1 4 to the "on" position, the lever 50 snaps back to the illustrated position as projection 70 engages the other formed end 71 of slide 52 thereby causing the portion of the slide 52 marked "on" to be in register with the window 53. This arrangement accordingly provides for a visual indication of the dolly position as determined by the position of the carriage 45.

The actuator 39 further includes a sensor peg 55 which registers with and projects into engagement with the plunger 20 of the circuit breaker. This peg 55 is guided by a pin 56 engaging in a slot 57 thereof, and a further pin and slot connection 58 connects the peg with a bellcrank lever 59 which is pivoted at 60 to the mounting plate 61 fixed with the casing 42. A sensor-loading spring 62 connects by one end with the lever 59 and by the other end with a peg 63 on the guide 44 to load the lever 59 to pivot in the clockwise direction, thereby to urge the sensor peg 55 into engagement with the plunger 20. The action of the spring 29, however, is greater than that of the spring 62, so that the plunger 20 is not pressed inwards thereby.The outer end of the bell-crank lever 59 is connected, by pin and slot connection 65, with a slide 66, guided by pins 67, projecting from the plate 61, engaging in a long slot 68 therein, said slide 66 carrying a tongue or flag 69 bearing a marking "tripped". It will readily be understood that upon the circuit breaker being tripped, the plunger 20 is withdrawn, thereby permitting the sensor peg 55 to extend into the opening 22. The slide 66 is correspondingly raised to bring the word "tripped" into position in front of the window 53 to provide a visual indication of the tripped condition of the circuit breaker, at the same time obscuring the "on" or "off" indiation given by the slide 52. Upon the circuit breaker being reset, of course, the slide 52 returns to the illustrated position under the influence of the spring 29.

The illustrated arrangement according to the invention has a number of advantages of which the following are significant: 1. The actuator, as illustrated, can if desired be employed in conjunction with a conventional circuit breaker not having the plunger 20. In this event, the sensor peg 55 merely abuts the front surface of the housing of the circuit breaker.

2. The tongue or flag 69 of the trip-condition indicator in the actuator has its operative position positively defined and therefore gives positive and definite indication of the trip condition in correct register with the window aperture 53.

3. When the breaker is tripped the flag 69 obscures the on/off indicator of the actuator and therefore ensures that the proper condition of the breaker is displayed at the window 53.

4. The derivation of intelligence from within the circuit breaker is very positive and can accommodate wide variations in manufacturing tolerances which can occur from breaker to breaker. This is achieved by the "over-centre" or bi-stable nature of the mechanism involved.

5. When the actuator 39 is not present, it is not possible effectively to tamper with the indicator on the breaker; if in the illustrated condition the plunger 20 should be pushed inwards, it will spring back to the flush position under the action of the spring 29.

Whilst the foregoing gives details of a preferred construction according to the invention, it is to be understood that modifications can be made thereto without departing from the scope of the invention. For instance, the indicator element need not be in the form of a plunger, such as the plunger 20, which is displaceable in a longitudinal or axial direction. It could, for example, be in the form of an element, such as a disc, which is rotatable between its normal and second dispositions corresponding to the non-tripped and tripped conditions of the breaker.

Claims

1. An electric circuit breaker characterised by trip-condition indicator means separate from a manually-displaceable operating member of the breaker and including an element having an indicator face exposed at a front face of a housing of the circuit breaker, and resilient means serving, when the circuit breaker is in its non-tripped condition, to urge the element towards a normal disposition and being adapted, upon tripping of the breaker, to move the element into a second disposition indicative that the breaker has been tripped.

2. An electric circuit breaker as claimed in claim 1 in which the said element is an axiallydisplaceable plunger a front end of which constitutes the indicator face.

3. An electric circuit breaker as claimed in claim 2, in which the plunger, in the normal position, has its front end flush with or nearly flush with the front face of the housing and, in its second position, has its said front end withdrawn inwardly of the housing.

4. An electric circuit breaker as claimed in claim 1, 2 or 3 in which the resilient means comprises a bistable spring-loaded lever system adapted to be shifted from a first stable position, corresponding to the normal disposition of the element, to a second stable position, corresponding to the second disposition of the element, upon tripping of the breaker.

5. An electric circuit breaker as claimed in any preceding claim in which a tripping mechanism of the circuit breaker includes a pivoted trip latch which is released upon tripping of the breaker and which then permits the resilient means to move the element into the second disposition.

6. An electric circuit breaker having a tripcondition indicator substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. An electric circuit breaker as claimed in any of claims 1 to 5 and having a motorised actuator assembled thereto to overlie the front face of the housing of the breaker, said actuator including a sensor engaging the indicator face of the element and serving to provide, at a convenient location on the actuator, a visual indication of the trip condition of the breaker.

8. An electric circuit breaker as claimed in claim 7 wherein the sensor provides the visual indication at the front of the actuator.

9. An electric circuit breaker as claimed in claim 7 or 8 wherein the actuator incorporates a display indicative of the on and off condition of the actuator, the sensor serving, upon tripping of the breaker, to obscure the display to provide a visual indication that the breaker is in its tripped condition.

1 0. An electric circuit breaker having a tripcondition indicator, and having a motorised actuator assembled thereto, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

11. A motorised actuator adapted for assembly to an electric circuit breaker as set forth in claim 1 to overlie the front face of the housing of the breaker, and having a sensor for engaging the indicator face of the plunger and adapted to provide, at a convenient location on the actuator, a visual indication of the trip condition of the breaker.

1 2. A motorised actuator adapted for assembly to an electric circuit breaker substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the accompanying drawings.