Title of Invention

AN ADJUSTMENT DEVICE OF THE CIRCUIT BREAKER THERMAL TRIP DEVICE WITH A BIMETAL STRIP

Abstract

The present invention relates to an adjustment device of the circuit breaker thermal trip device with a bimetal strip, comprising; an adjusting screw accessible from outside and arranged to act on the position of the foot of the trip device, a support joined via one of its ends to the foot of the bimetal strip and co-operating with the adjusting screw which presses against the base of the support in the zone joining the support and the foot of the bimetal strip and means for returning the bimetal strip to an initial position corresponding to the slackened state of the adjusting screw characterized in that the other end of the support is articulated on a fixed pivot securedly united to the circuit breaker case, and the foot of the bimetal strip is connected by a shunt to a. contact pad to achieve electrical continuity.

Full Text

The invention relates to a device for adjusting the thermal trip device or bimetal strip of a circuit breaker comprising an adjustment screw arranged to act on the position of the foot of this trip device. In a known manner, adjustment devices of this type comprise an adjustment screw acting directly on the foot of the bimetal strip deforming the latter so as to adjust the position of a thermal slide associated to the bimetal strip and having the function of performing opening of the movable contact in the event of overheating. This adjustment is performed in the factory and enables the tripping threshold of the circuit breaker to be defined. This embodiment wherein the action of the screw is exerted directly on the foot of the bimetal strip implies a symmetrical construction of the assembly and prevents a relatively wide bimetal strip from being fitted. In addition, fixing of the foot of the bimetal strip by welding in an electrical continuity zone where the circuit breaker shunt release is also located can give rise to problems. The object of the invention is to overcome the drawbacks of known constructions by achieving an adjustment device as defined above, which enables efficient adjustment of the circuit breaker in the factory and a more compact construction of the assembly. This object is achieved by the device according to the invention characterized in that it comprises : - a support joined by one of its ends to the foot of the bimetal strip and articulated at its other end on a fixed pivot, the adjustment screw being accessible from outside, and pressing against the base of the support in the zone linking the support and the foot of the bimetal strip, - and return means arranged to bias the bimetal strip by means of said support to an initial position corresponding to the slackened position of the adjustment screw. According to a preferred embodiment, this device is mounted on the same side with respect to the mid-axis of the circuit breaker, dissymmetrically with respect to this axis. Accordingly the present invention provides an adjustment device of the circuit breaker thermal trip device with a bimetal strip, comprising; an adjusting screw accessible trom outside and arranged to act on the position of the foot of the trip device, a support joined via one of its ends to the foot of the bimetal strip and co-operating with the adjusting screw which presses against the base of the support in the zone joining the support and the foot of the bimetal strip and means for returning the bimetal strip to an initial position corresponding to the slackened state of the adjusting screw characterized in that the other end of the support is articulated on a fixed pivot securedly united to the circuit breaker case, and the foot of the bimetal strip is connected by a shunt to a contact pad to achieve electrical continuity axis. The present invention will be better understood with reference to the description and drawings illustrating in non-restrictive manner a preferred embodiment in which : - Figure 1 is a partial view of a circuit breaker equipped with a device according to the invention, - Figure 2 is a partial axial sectional view representing the device of the invention as shown by figure 1 in a position where the adjustment screw is slackened, - Figure 3 is a similar view to figure 2 in which the adjustment screw is tightened, - Figures 4 and 5 are similar views to those of figures 2 and 3 but representing construction alternatives, notably as far as the connector contact terminal is concerned, - Figure 6 represents a transverse sectional view of the circuit breaker partially represented by figures 4 and 5, along the line M-M1, and - Figure 7 represents an alternative embodiment of the device according to the invention. With reference to figures 1, 2 and 3, the circuit breaker 10 represented partially comprises a case 11 in which the essential components which are well known in themselves are assembled. Among these components there figures a thermal slider 12 which drives a trip lever in case of overheating, this trip lever (not represented) having the function of performing unlocking of a small connecting rod retaining a plate linked to a movable contact, that is to say of breaking the mechanical link between this connecting rod and this plate. The plate being stressed by a spring, breaking of the mechanical link between the connecting rod and the plate results in opening of the movable contact. The thermal slider 12 is linked to a thermal trip unit with bimetal strip 13, on which it is mounted by means of a moulded shoe which engages on one end of the bimetal strip when a slight pressure is exerted. The other conventional components which can be seen In the drawing are a braided strip 15 linked to the bimetal strip 13 and supported by a braided strip support 16, an arcing horn 17 and a shunt 18 linked to a contact pad 19 and also a device 20 for adjusting the thermal trip unit. It Is the design and achievement of this adjustment device which constitute the main object of this Invention. The end of the bimetal strip 13 which is opposite the end linked to the thermal slider 12, that Is to say the foot of the bimetal strip, is securedly united to a flexible or rigid support 21 in the form of a rod whose free end Is articulated on a fixed pivot 22. In practice, this pivot 22 Is formed by a protuberance of suitable shape, moulded or adjoined to and securedly united to the case, and the free end which is articulated on this pivot has the shape of a fork 23 with two branches engaged on each side of this protuberance. An adjustment screw 24 is housed in a suitable cavity of the case, accessible from outside, and presses against the base of the flexible or rigid support 21, In the zone linking this support and the bimetal strip 13. Adjustment of the bimetal strip is performed in the factory and defines the tripping threshold of the circuit breaker. When the support 21 Is flexible. It constitutes a sufficient return means in itself to bias the bimetal strip to an initial position corresponding to the slackened position of the adjustment screw 24. When the support 21 Is rigid, a return spring, as represented by figure 7, must be associated thereto to perform the function described above. Figures 2 and 3 are Identical views to that of figure 1, but wherein a fixed tunnel input terminal 25 has also been represented connected to the contact pad 19. In figure 2, the adjustment screw 24 has been tightened, which causes it to move in the direction of the arrow A. This tightening has the consequence of moving the thermal slider 12 in the direction of the arrow B, due to the pivoting of the support 21 in the direction of the arrow C around the pivot 22. In case of slackening, return of the bimetal strip to Its position is achieved by the return means described above. Figures 4 and 5 illustrate another embodiment wherein the fixed tunnel terminal is replaced by a movable tunnel terminal 30 comprising an upper pad 31 associated to the arcing horn 17, a lower pad 32 associated to the shunt 18 and a screw 33 for clamping the cables. The steel upper pad supports the forces involved in connection and the copper lower pad ensures a direct electrical continuity with the bimetal strip 13. The thermal trip device adjustment device is identical to that described previously. It comprises a bimetal strip 13, the support 21 pivoting around a fixed pivot 22 and the adjustment screw 24. Figure 4 shows the screw in the slackened state and figure 5 shows the screw in the tightened state. The difference of position of the thermal slide can be noted in the two figures. Figure 6 shows a cross-sectional view of the circuit breaker of figures 2 and 3 along an axis M-M1 of these figures. The mid-axis X of the circuit breaker 10 passes through the axis of the fixed tunnel terminal 25. On the other hand, the bimetal strip 13, of relatively wide construction, imposes an off-centre construction of certain components. Notably, the H-shaped magnetic yoke 40 is dissymmetrical. The movable contact 41 housed in the opening of the magnetic H is off-centre, as is the breaking cassette 42 in which the movable contact is located. This particular construction enables all the components to be integrated in a case of relatively small dimensions. Notably, the trip device adjustment device is mounted dissymmetrically inside the circuit breaker case, on one side with respect to its mid-axis. Figure 7 is a schematic view illustrating the circuit breaker 10 in a particular embodiment. The support 21 is rigid and comprises a first end 51 wound into an arc of a circle or a full circle, and a second end folded into a bracket. The first end wound into an arc of a circle is engaged in a partially open circular cavity around a virtual pivot defined by the centre of said circular cavity. The second end performs fixing of the bimetal strip. A return spring 54 is fixed on one hand to the support 21 and on the other hand to a fixed pin 55 securedly united to the case. The adjustment screw 24 presses against the support 21 and is housed in a hole 56 of hexagonal cross-section arranged in the case. Other particular constructive features could be envisaged, notably as far as the end 51 of the support 21 is concerned. The pivot on which this support is articulated could be formed by a pin added on or moulded in a single part with this case. WE CLAIM: 1. An adjustment device of the circuit breaker thermal trip device with a bimetal strip, comprising; an adjusting screw (24) accessible from outside and arranged to act on the position of the foot of the trip device, a support (21) joined via one of its ends to the foot of the bimetal strip (13) and co-operating with the adjusting screw (24), which presses against the base of the support (21) in the zone joining the support (21) and the foot of the bimetal strip (13), and means for returning the bimetal strip (13) to an initial position corresponding to the slackened state of the adjusting screw (24) characterized in that the other end of the support (21) is articulated on a fixed pivot (22) securedly united to the circuit breaker case, and the foot of the bimetal strip (13) is connected by a shunt (18) to a contact pad (19) to achieve electrical continuity. 2. The device according to claim 1, wherein the support (21) is rigid, and that the return means comprise a return spring (54) one end whereof is fixed to the support and the other end whereof is secured to a fixed pin securedly united to the circuit breaker case. 3. The device according to claim 1, wherein the support (21) is elastic, and that the return means are formed by the support itself. 4. The device according to claim 1, wherein the end of the support (21) articulated on said fixed pivot (22) presents a fork shape. 5. The device according to claim 4, wherein fixed pivot (22) is formed by a moulded or added protuberance securedly united to the circuit breaker case. 6. The device according to claim 1, wherein said fixed pivot is formed by one end of the support (21) rolled in an arc of a circle and engaged in a circular cavity (53) open on a sector. 7. The device according to claim 1, wherein it is fitted on one side with respect to the mid-axis of the circuit breaker, dissymmetrically with respect to this axis. 8. An adjustment device of the circuit breaker thermal trip device with a bimetal strip, substantially as herein above described with reference to the accompanying drawings.

Documents:

911-mas-1996 abstract.jpg

911-mas-1996 abstract.pdf

911-mas-1996 claims.pdf

911-mas-1996 correspondence-others.pdf

911-mas-1996 correspondence-po.pdf

911-mas-1996 description (complete).pdf

911-mas-1996 drawings.pdf

911-mas-1996 form-1.pdf

911-mas-1996 form-26.pdf

911-mas-1996 form-4.pdf

911-mas-1996 form-9.pdf

911-mas-1996 others.pdf

911-mas-1996 petition.pdf