EP1430499B1

EP1430499B1 - Low-voltage automatic circuit breaker with reduced number of components

Info

Publication number: EP1430499B1
Application number: EP02764787A
Authority: EP
Inventors: Bianc Giuseppe Bertolotto; Davide Malacalza
Original assignee: ABB Service SRL
Current assignee: ABB Service SRL
Priority date: 2001-07-23
Filing date: 2002-07-23
Publication date: 2005-09-21
Anticipated expiration: 2022-07-23
Also published as: WO2003010788A1; DE60206293D1; DE60206293T2; EP1430499A1; ITMI20011572A1; CN1465082A; ITMI20011572A0; ATE305169T1; CN1319099C

Abstract

An automatic low-voltage circuit breaker, comprising an enclosure that contains moving contact means (3) and fixed (4) contact means, the moving contact means comprising at least one moving contact and the fixed contact means comprising at least one fixed contact, a kinematic chain that includes a plurality of levers that move the moving contact between an open position and a closed position; its particularity consists of the fact that at least one of the levers (8) is constituted by a single body that comprises at least one first rigid portion (8b) and at least one second rigid portion (8a) that is adjacent to the first rigid portion and is connected thereto by means of a first flexible hinge (8c) constituted by a first elastic and resilient element.

Description

The present invention relates to a low-voltage automatic circuit breaker with reduced number of components. More particularly, the invention relates to an automatic low-voltage circuit breaker having reduced constructive complexity.
As is known, circuit breakers are protective devices which, when an electrical fault occurs in the circuit in which they are inserted, trip and interrupt the flow of current; for this purpose, they are provided with electrical contacts constituted by two conducting metallic parts, one of which is fixed and termed fixed contact or stationary contact, the other one being movable and being termed moving contact. The moving contact is actuated by a kinematic chain that allows its coupling or separation with respect to the corresponding fixed contact, accordingly closing or opening the circuit. Said kinematic chains are meant, in practice, to transmit motion and forces from the actuation component to the moving contacts and to amplify said movements and forces so as to perform the switching action, particularly the opening action, as rapidly as possible.
The kinematic chains currently used, despite allowing to perform adequately their tasks, have drawbacks.
In particular, one of the critical aspects of known kinematic chains resides in their complexity, since they are generally composed of a large number of components such as levers, joints, springs, et cetera.
An example of an automatic circuit breaker 1 of a known type, with the corresponding kinematic chain, is shown in Figure 1. According to embodiments that are widely used in practice, the circuit breaker 1 comprises an enclosure 2, from which an actuation arm 9 protrudes and which contains at least one moving contact 3 and at least one fixed contact 4, and a kinematic chain 10, which comprises multiple levers that move the moving contact 3 between an open position and a closed position. Generally, said multiple levers comprise a first lever 5, on which the moving contacts of the circuit breaker are mounted, and a second release lever 6, which is functionally associated with fault protection devices; Figure 1 schematically illustrates a single protection device provided with a release element 20. Said levers 5 and 6 are functionally connected to each other by virtue of a spring 11 and an element for connection to the arm 9, schematically designated by the reference numeral 7, which allow to couple/uncouple the relative movement of the two levers 5 and 6, depending on the operations to be performed. A spring 12 is furthermore generally associated with the pair of levers 5 and 6 and provides the kinematic chain with an amount of energy required to rapidly reach an adequate contact opening speed. Furthermore, in order to ensure adequate coupling pressure between the contacts, an additional spring 13 is usually used between the lever 6 and the moving contact 3. Finally, depending on the applications, the kinematic chain 10 can comprise additional components; in particular, the embodiment illustrated in Figure 1 uses an additional lever 8, which is shaped appropriately so as to interact functionally with the actuation arm 9 and with the body of the moving contact 3, and so as to allow, during an operation for closing the contacts by means of the arm 9, the retention of the moving contact 3 at a preset distance from the corresponding fixed contact 4. In this case also, a torsion spring 14 is generally associated with the retention lever 8 and facilitates its movement with respect to the arm 9 and the moving contact 3. Another example of an automatic circuit breaker of a known type is indicated in the patent application FR 2605454.
To summarize, it is evident that the considerable number of components causes high production costs, difficulties in assembly, calibration and setting, complexity of design, high sensitivity to working tolerances, and possible play and vibration.
The aim of the present invention is to provide an automatic low-voltage circuit breaker having a reduced number of components, particularly with reference to the kinematic chain of the circuit breaker.
Within the scope of this aim, an object of the present invention is to provide an automatic low-voltage circuit breaker in which the kinematic chain of the circuit breaker is provided by means of a structure that is simplified with respect to the known art and with a reduced number of components while maintaining the functional performance unchanged.
Another object of the present invention is to provide an automatic low-voltage circuit breaker in which the production and assembly costs and the time required to design the kinematic chain are reduced with respect to known types of circuit breaker.
Another object of the present invention is to provide a low-voltage automatic circuit breaker in which the play and vibration of the kinematic chain are minimized.
Another object of the present invention is to provide a low-voltage automatic circuit breaker that has a reduced weight by virtue of the reduced total number of components.
Another object of the present invention is to provide an automatic low-voltage circuit breaker that is highly reliable, relatively simple to manufacture, and at competitive costs.
This aim, these objects and others that will become apparent hereinafter are achieved by an automatic low-voltage circuit breaker, according to claim 1.
Further characteristics and advantages of the invention will become apparent from the description of preferred but not exclusive embodiments of the automatic circuit breaker according to the present invention, illustrated by way of non-limitative example in the accompanying drawings, wherein:

Figure 1 is a schematic view of a portion of an automatic circuit breaker according to the background art;
Figure 2 is a partial view of the automatic circuit breaker according to the present invention;
Figure 3 is a detail view of a first lever of the kinematic chain of the circuit breaker according to the present invention;
Figure 4 is a view of a second lever of the kinematic chain of the circuit breaker according to the present invention.

In the description that follows, identical reference numerals designate elements that are identical or technically equivalent to components that are already known in the art.
With reference to Figures 2 to 4, the automatic circuit breaker according to the present invention, generally designated by the reference numeral 1, comprises an enclosure 2 from which an actuation arm 9 protrudes externally; said enclosure contains moving contact means and fixed contact means. The moving contact means comprise at least one moving contact 3 and the fixed contact means comprise at least one fixed contact 4.
A kinematic chain, which includes a plurality of levers that move the moving contact 3 between an open position, in which it is coupled to the fixed contact 4, and a closed position, in which it is separated from said fixed contact, is arranged in the enclosure 2.
Advantageously, in the automatic circuit breaker according to the present invention the above cited kinematic chain comprises at least one first lever constituted by a body that is formed monolithically and comprises at least one first rigid portion and at least one second rigid portion that is adjacent to the first rigid portion and is connected thereto by means of a first flexible hinge constituted by a first elastic and resilient element; in particular, depending on the requirements and/or needs of the application, and as will become apparent in detail in the description that follows, the flexible hinge, which allows the mutual movement of the rigid portions, can be provided by means of a metallic insert that is at least partially embedded in the lever body, or by reducing the thickness of a portion of the body of said lever with respect to the thickness of the portions that are adjacent thereto.
In this manner, said lever can be considered a compliant mechanism, i.e., a mechanism which, when subjected to mechanical stress, undergoes deformation and then resumes the initial position and integrates monolithically the structure and functions performed in the known art by two or more levers with corresponding springs.
Accordingly, with respect to the known art, the number of necessary components is reduced substantially, with the advantage of reducing production costs as well as assembly costs and times. Furthermore, the reduction in the number of components leads to greater simplicity in designing the automatic circuit breaker, reduced wear of the components, and reduces or eliminates play as well as any vibration and noise.
Preferred embodiments for levers that belong to the kinematic chain of the circuit breaker 1 are now described by way of non-limitative example.
In particular, in the embodiment shown in Figure 3, said first lever is a retention lever 8, which is suitable to lock the moving contact 3 at a preset distance from the fixed contact 4 during closure performed by operating the arm 9. As shown in Figures 2 and 3, said retention lever 8 comprises a single body that has: a first rigid portion 8b, which is rigidly pivoted on a pivot 29 that is fixed to the enclosure 2; a second rigid portion 8a, which is conveniently contoured so as to have a recess 25 that is suitable to engage a corresponding protrusion 26 of the moving contact 3, and a contoured profile with a protrusion 27 for interaction with the arm 9 during closure under the action of the arm 9; the two portions 8a and 8b are interconnected by a flexible hinge 8c. As shown, said hinge 8c is preferably constituted by a reduction in the thickness of a part of the body of the lever with respect to the thickness of the portions 8a and 8b that are adjacent thereto; as an alternative, it can be obtained by means of a metallic insert that is embedded at least partially in the body of said lever and functionally interconnects the two portions.
In this manner, during operation the lever 8, differently from the known art, no longer rotates about its own pivot; the necessary movement is in fact obtained by virtue of the hinge 8c, which allows the part 8a to move with respect to the part 8b and by virtue of its elastic and resilient behavior allows the deformation of said lever and its subsequent resumption of the initial shape, performing in practice the functions performed previously by the spring 14 and thus entailing a saving of components and of the corresponding assembly and calibration operations.
Figure 4 illustrates a second lever that can be used in the circuit breaker according to the invention in addition and/or as an alternative to the previously illustrated lever 8.
In this case, said lever, designated by the reference numeral 56, is a lever for actuating and supporting the moving contact 3, which is pivoted on a pivot that is rigidly coupled to the enclosure 2 and also has a single body that comprises a first rigid portion 5', on which the moving contact 3 is mounted and which is functionally associated with the arm 9 by means of a connecting element 7, generally a U-shaped member that can slide in a seat 18; a second rigid portion 6', which is suitable to interact functionally with a release device 20 of the circuit breaker, for example a relay, and has a hook-shaped end 19 that interacts with the U-shaped member 7 so as to engage it and couple its own movement to the movement of the portion 5' when necessary; and at least one first flexible hinge for mutually connecting the two rigid portions 5' and 6'.
As shown in Figure 4, said first hinge is constituted by an elastic and resilient metallic plate 15 that interconnects the two portions 5' and 6', allowing their mutual movement and thus allowing to combine in a single component the functions performed in the known art by the two separate levers 5 and 6 and by the corresponding spring 11. As an alternative, the two rigid portions 5' and 6' might be interconnected by a flexible hinge constituted by one or more portions the are thinner than the adjacent parts, according to a solution that is described in a co-pending Italian patent application nr. MI2001A001574 in the name of the present Applicant.
Advantageously, the lever 56 can comprise a second flexible hinge suitable to connect the first rigid portion 5' to the enclosure 2 so as to allow movement with respect to it; as shown in Figure 4, the second hinge is constituted by an elastic and resilient metallic lamina or insert 16, which is embedded at one end in the first rigid portion 5' and is arranged at the other end so as to react on the inner face of the enclosure 2, for example against a suitable protrusion, not shown. In this manner, the spring 12 used in the known art is no longer present, since its function is integrated in the body of the lever 56; accordingly, the corresponding positioning, setting and assembly operations are avoided.
Furthermore, the body of the lever 56 can comprise at least one third flexible hinge that is suitable to connect the lever 56 to the moving contact 3 mounted thereon so as to allow relative mutual motion; preferably, the third hinge is constituted by a resilient and elastic metallic insert 20, which is at least partially embedded in the first rigid portion 5'. In this manner, with an additional advantage, the functions performed in the known art by the spring that couples the body of the moving contact to the lever on which it is mounted are also integrated in the structure of lever 56.
In particular, Figure 4 shows in dashed lines an additional metallic insert 21, which is suitable to connect the body of the lever 56 to a second moving contact 3 that is fully equivalent to the first one and is generally used in the circuit breaker associated with a corresponding fixed contact.
Finally, the body of the lever 56 can comprise a fourth flexible hinge 17, which connects the hook-shaped end 19 to the remaining part of the second portion 6'; in this case also, said fourth flexible hinge 17 can be provided by reducing the thickness of a part of the second rigid portion that lies proximate to said shaped end, or by means of a metallic insert that is embedded in the body of the lever proximate to the hook-shaped end. In this manner, the hook-shaped end, during the opening of the circuit breaker, rotates about the hinge 17 and disengages the U-shaped member 7, leaving the two portions 5' and 6' free to rotate with respect to each other; at the end of the action, the end 19, by virtue of the elastic return of the corresponding hinge, resumes the initial configuration and reengages the U-shaped member 7.
In practice it has been found that the automatic circuit breaker according to the present invention fully achieves the intended aim and objects, since the corresponding kinematic chain is provided by means of a reduced number of components, to the advantage of production costs, installation times, and the reliability of the device as a whole.
The automatic circuit breaker thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with other technically equivalent elements.

Claims

An automatic low voltage circuit breaker (1), comprising an enclosure (2) from which an actuation arm (9) protrudes, said enclosure (2) containing moving contact means and fixed contact means, the moving contact means comprising at least one moving contact (3) and the fixed contact means comprising at least one fixed contact (4), a kinematic chain that includes a plurality of levers that move the moving contact (3) between an open position, in which it is separated from the fixed contact (4), and a closed position, in which it is coupled to said fixed contact (4), whereby said plurality of levers comprises at least a first lever (8,56) constituted by a single body characterized in that said body comprises at least one first rigid portion (8a,5') and at least one second rigid portion (8b,6') that is adjacent to said first rigid portion (8a,5') and is connected thereto by means of a first flexible hinge (8c) constituted by a first elastic and resilient element, one of said rigid portion (8a,8b,5',6') being pivoted on said enclosure (2).
The automatic circuit breaker (1) according to claim 1, characterized in that said first flexible hinge is suitable to facilitate the mutual movement of said first (8a,5') and second rigid portion (8b,6').
The automatic circuit breaker (1) according to claim 2, characterized in that said flexible hinge is provided by means of a metallic insert that is at least partially embedded in the body of said lever.
The automatic circuit breaker (1) according to claim 2, characterized in that said flexible hinge is provided by reducing the thickness of a portion of the body of the lever with respect to the thickness of the portions that are adjacent thereto.
The automatic circuit breaker (1) according to one or more of the preceding claims, characterized in that said first lever is a compliant mechanism.
The automatic circuit breaker (1) according to one or more of the preceding claims, characterized in that said first lever is a retention lever (8) that is suitable to lock the moving contact at a preset distance from the fixed contact during closure, said retention lever (8) having a first rigid portion (8a) that is pivoted to a pivot (29) that is rigidly coupled to the enclosure (2) and a second rigid portion (8b) that is suitable to interact functionally with said moving contact (3) and with said actuation arm (9), said first (8a) and second rigid portions (8b) being interconnected by a flexible hinge.
The automatic circuit breaker (1) according to one or more of the preceding claims, characterized in that said first lever is a lever (56) for actuating and supporting the moving contact (3), said actuation and support lever (56) having a first rigid portion (5') on which said moving contact (3) is mounted, said first rigid portion (5') being functionally associated with the actuation arm (9) by virtue of a connecting element (7), a second rigid portion (6'), which is suitable to interact functionally with a release device (20) of the circuit breaker (1), and at least one first flexible hinge for mutually connecting said first (5') and second rigid portions (6').
The automatic circuit breaker (1) according to claim 7, characterized in that said actuation lever (56) comprises a second flexible hinge that is suitable to connect the first rigid portion (5') to said enclosure (2) so that it can move with respect to said enclosure (2).
The automatic circuit breaker (1) according to claim 8, characterized in that said second flexible hinge comprises at least one metallic plate (16) that on one side is embedded in said first rigid portion (5') of the actuation lever (56) and is suitable to react, on the other side, against the inner face of the enclosure (2).
The automatic circuit breaker (1) according to one or more of claims from 7 to 9, characterized in that said actuation lever (56) comprises at least one third flexible hinge suitable for connection to the moving contact (3) so that it can move with respect to said contact (3).
The automatic circuit breaker (1) according to claim 10, characterized in that said third flexible hinge is constituted by a metallic insert (16) that is at least partially embedded in said first rigid portion (5').
The automatic circuit breaker (1) according to one or more of the claims from 7 to 11, characterized in that said second rigid portion (6') of the actuation lever (56) comprises a hook-shaped end (19) that is suitable to interact functionally with said connecting element (7) and is connected to the remaining part of the second portion (6') by virtue of a fourth flexible hinge.
The automatic circuit breaker (1) according to claim 12, characterized in that said fourth flexible hinge is provided by reducing the thickness of a part of the second rigid portion (6') that is proximate to the hook-shaped end (19) or by means of a metallic insert (16) that is embedded in the body of the lever (56) proximate to the hook-shaped end (19).