EP1218898A1 - Low-voltage power circuit breaker comprising a switching chamber and a displaceable contact unit - Google Patents

Abstract

The invention relates to a low-voltage power circuit breaker, comprising a contact unit (5), specifically designed to accommodate contact levers (8), which has receiving bores (12) for a bearing bolt (10) that passes through the contact lever (8). Lateral bearing arms (15) with projecting lugs (16) allow a pivotal displacement of the contact unit (5) for making and breaking contact. Said bearing arms mesh with bearing points (4) of the switching chamber. A lever chain (7) is used to transmit an actuating force from a drive device (6) to the contact unit (5). Bearing means (21) for an articulated bolt (22) are provided on said contact unit to couple the lever chain (7). The contact unit (5) is supported against forces which act in a transverse direction to its pivotal axis by lateral guide surfaces (23). Receiving means (20) for a spring (18) which maintains the final position can also be fitted to the contact unit (5). Said receiving means holds the contact unit (5) under tension in its circuit-breaking final position. The contact unit (5) and its aforementioned features is produced from plastic as a single-piece multi-purpose part. The inventive contact unit (5) is particularly suitable for multi-pole low-voltage power circuit breakers, in which the neighbouring pole lies a short distance away.

Description

description

Low-voltage circuit breaker with a switching chamber and a movable contact carrier

The invention relates to a low-voltage circuit breaker with a switching chamber and a contact carrier arranged pivotably in the switching chamber for receiving contact levers with the following features: receiving openings for a bearing pin passing through the contact lever,

Receiving pockets for contact force springs, lateral bearing arms for the pivotable mounting of the contact carrier in bearing points of the switching chamber for the purpose of transferring the contact carrier into a switch-on position or a switch-off position, and

Bearing means for a hinge pin for coupling the contact carrier with a drive device of the circuit breaker which serves to pivot the contact carrier into the switch-on position or the switch-off position.

So far, composite constructions have always been used in circuit breakers for high rated currents with correspondingly large contact carriers which have a plurality of parallel contact levers, in which one body only serves to accommodate the contact levers and side walls or levers on the side of this body, generally designed as metal parts, by Scrub or are attached in some other way, which then enable the contact carrier to be pivoted in the associated bearing points of the switching chamber.

A movable contact carrier of this type is due to the

DE 35 39 786 AI become known. Here are the bearing arms Part of a bracket, which is adapted to a holding body for the contact lever to size. It is a construction consisting of several metal parts. Since the entire contact carrier is live, an insulating intermediate member must be inserted between the contact carrier and the associated drive device.

Movable contact carriers are also known, the bearing arms of which are attached to a central main body that receives the contact levers (DE 296 15 566 Ul). The bearing arms can consist of metal, while the central main body, which can be combined from sections, can consist of insulating plastic. Since the lever chain leading to the drive device acts on the main body, no separate isolating intermediate link is required if the main body consists of insulating plastic.

The constructions composed of several individual components in the known manner described are simple and expedient, but result in a relatively large width tolerance due to the sum of several individual tolerances, namely a sheet metal tolerance on both sides and a tolerance of the central part. There is also the advantage of customized manufacturing processes for the individual parts in that several manufacturing steps are required to produce the contact carriers from the individual parts, and errors can occur. Furthermore, in the case of bearing arms made of metal or sheet metal, there is the advantage of good strength with small dimensions that tension can be carried over from the contact levers to the area of the bearing pins, which may require additional measures to maintain the mutual insulation of adjacent poles of the circuit breaker that undesirably increase the pole spacing. The invention is based on the object of designing a low-voltage circuit breaker in such a way that the outlay for the movable contact carriers is markedly reduced and the inherent shadow of the circuit breaker is improved overall.

This object is achieved according to the invention in that the contact carrier for limiting a deflection transverse to the direction of the pivoting has lateral guide surfaces for interacting with counter surfaces of the circuit breaker of the circuit breaker, and the complete contact carrier with the above-mentioned features is produced in one piece from plastic as a multifunctional part is.

Even if the disadvantage is taken into account that the lateral bearing arms made of plastic have to be made thicker than metal parts, there is an advantage from the fact that there is only one tolerance, namely that of the uniform plastic body. There is also no need for space for fasteners, such as protruding screw heads or the like, and the smooth side walls of the contact carrier ensure good tightness against the passage of switching gases in this area. What is important in this connection is the guidance of the contact carrier on the walls of the switching chamber, which provides support against forces which can occur when switching transversely to the pivoting movement of the contact carrier. These transverse or torsional forces are thus kept away from the bearing arms, which significantly simplifies the dimensioning of the bearing arms and the associated bearing points in the walls of the switching chamber. The surprising advantage of the improved guidance of the contact carrier in the switching chamber is that lower resistance to movement when switching short circuits. This is due to the fact that the joints of the lever chain, which connects the contact carrier to its drive device, are also less stressed by tilting and are essentially only stressed by tensile and compressive forces. This therefore enables the entire drive chain to be dimensioned more favorably than previously used switching mechanisms.

Although different designs are conceivable and can be suitable for the interaction of the bearing arms of the contact carrier and the associated bearing points of the switching chamber, it has proven expedient within the scope of the invention that the bearing arms project laterally projecting cylindrical pins for engaging in adapted bearing openings of the switching have chamber. Such pins are in particular particularly suitable for the one-piece production of the contact carrier, especially since it has been shown that the increase in the diameter of the plastic pins required compared to metal pins can be kept in a frame compatible with the overall dimensions of the contact carrier.

A significant improvement of the circuit breaker can be achieved according to a development of the invention in that the contact carrier has receiving means for an end position retaining spring. Before going into details of the design and arrangement of such receiving means, the meaning of the end position retaining spring mentioned will first be explained. The purpose of such a spring is to hold the contact carrier (s) and the connected parts of the drive device, in particular the selector shaft, in their switched-off state with a certain force in their end position. The end position retaining spring therefore acts in the sense of Switching, but because of its relatively low force, should not be confused with an opening spring, as is required for circuit breakers for other areas of application, for example medium or high voltage. As a result, an end position retaining spring in a low-voltage circuit breaker is significantly weaker than the other springs intended for switching on and off.

For example, US Pat. No. 5,731,560 shows the drive mechanism of a multipole low-voltage circuit breaker for high currents and high electrodynamic forces. Here an end position retaining spring acts on the selector shaft. This means that all poles are pulled to the OFF position. This arrangement is unsuitable for current-limiting circuit breakers with a single pole opening.

Another low-voltage circuit breaker is shown in US Pat. No. 3,832,504, in which two tension springs act on one side of a crossbar connecting the switching poles and on the other side of the crossbar

Structure of the switch is anchored. These springs do not allow polar contact on individual contact carriers. Here, too, all poles are therefore acted upon together, which, as already mentioned, is unsuitable for current-limiting circuit breakers with a single pole opening.

The fact that, according to the aforementioned development of the invention, means for accommodating an end position retaining spring are arranged in the contact carrier, makes it possible to provide each pole of a multi-pole circuit breaker with a

End position retaining spring and to ensure that with individual current-dependent opening of each pole, that the contact carrier remains open regardless of the control shaft. The effort for the production of the receiving means for the end position retaining spring on the contact carrier is negligible, since it is an integral part of the multifunctional part made of plastic.

While in principle receiving means for one end position retaining spring seem sufficient, it is advisable to provide receiving means for a second end position retaining spring and to arrange both receiving means symmetrically on the contact carrier. This symmetrical arrangement can preferably be realized in that the receiving means are arranged in the side bearing arms of the contact carrier.

In the above context, it proves to be advantageous if the end position holding spring is designed as a helical compression spring and the receptacle provided for its support is designed as a receiving pocket for one end of the end position holding spring. Compared to tension springs, for example in accordance with US Pat. No. 3,832,504, the advantage is achieved that the end position holding spring can be arranged as a compression spring between a rear wall of the switching chamber and the contact carrier, so it can be easily assembled or disassembled when the rear wall is removed for maintenance becomes.

While pocket-like depressions were considered above as the exception means for the end position retaining spring, the receiving means can be designed with the same effect and when using the same springs (helical compression spring) as a receiving pin. This means no difference for the manufacture of the contact carrier as a multifunctional part.

Since the dimensions of the end position retaining spring for a given force-displacement characteristic curve depend on the length and properties of the depending on the spring wire used, an appropriate outer diameter can result which is larger than the wall thickness of the bearing arms. Instead of providing this with a corresponding thickening to create a support for the entire cross section of the end position retaining spring, according to one embodiment of the invention, the bearing arm in question can have a recess on one narrow side with wall surfaces arranged opposite one another in such a way that the end position retaining spring also includes protruding on both sides over the wall thickness of the bearing arm is recorded centering.

A fiber-reinforced plastic is particularly suitable as the material for producing the contact carrier as a multi-functional part, it being possible for both mineral and organic fibers to be used.

The invention will be explained in more detail below for a better understanding with reference to a preferred exemplary embodiment shown in the figures, which does not restrict the scope of protection.

Figure 1 shows a switching chamber of a low-voltage circuit breaker with a contact carrier and adjacent parts, partly in section.

FIG. 2 shows a contact carrier in a perspective view with a view of the side provided for receiving contact levers.

In FIG. 3, the contact carrier is also in perspective with a view of the opposite side, which is provided for connection to a drive device. The switching chamber 1 of a low-voltage circuit breaker shown in FIG. 1 is composed of a rear wall 2 and a front part 2. In a known manner, the rear wall supports connecting rails for connecting the circuit breaker to an external circuit. In the area of the parting line between the rear wall 2 and the front part 3 there is a bearing point 4 for the pivotable mounting of a contact carrier 5. A schematically indicated drive device 6 and a lever chain 7 connecting the drive device 6 to the contact carrier 5 serve to contact the contact carrier 5 Switch the circuit breaker on and off to pivot bearing 4.

In the following detailed description of the contact carrier, reference is also made to FIGS. 2 and 3, since some of the characteristics of the contact carrier 5 can be seen more clearly from these than from FIG. 1 alone.

The contact carrier 5 serves to receive contact levers 8 (FIG. 1) which are arranged parallel to one another in a number corresponding to the rated current of the circuit breaker. The contact lever 8 is penetrated by a bearing pin 10, 5 bearing openings 12 are provided for receiving it in the lateral cheeks 11 of the contact carrier. Each two contact force springs 13 act on a contact lever 8 and ensure an adequate contact force when the circuit breaker is switched on. The contact force springs rest in pockets 14 on the contact carrier 5.

The lateral cheeks 11 mentioned merge downward (in the direction of the bearing points 4) into bearing arms 15, which have laterally projecting pins 16 for engaging in the bearing points 4. Below the area of the contact lever 8 contain the bearing arms 15 receiving means 17 for end position retaining springs, one of which is visible in FIG. 1. These receiving means 17 are designed as receiving pockets for the ends of the end position retaining springs 18 designed as helical compression springs. Although the end position retaining springs 18 have a diameter that is greater than the wall thickness of the bearing arms 15, they are centered by the receiving means 17. This is done by means of oppositely arranged wall surfaces 20, the radius of which is adapted to the end position retaining spring 18. Between these wall surfaces 20, the receiving pocket is open laterally, so that the spring can protrude beyond the bearing arm 15, but its force is introduced centrally into the bearing arm.

The end position holding springs 18 are supported with their ends facing away from the contact carrier on the rear wall 2 of the switching chamber 1. End position retaining springs 18 are therefore easily accessible for assembly and disassembly when the rear wall 2 is removed. Despite their position in the switching chamber, influences of switching arcs are kept away from the end position holding springs, since an apron 19 shown in FIG. 1 reflects the switching gases or prevents the passage downwards (in the direction of the bearing points 4).

As already mentioned, the contact carrier 5 is connected to the drive device by the lever chain 7. As a means for coupling the lever chain 7 to the contact carrier 5, the latter has on its side facing the drive device 6 bearing means 21 in the form of two molded bearing eyes, in which there are openings for receiving the ends of a hinge pin 22 shown in FIG. The lever chain 7 can consist entirely of metal parts, because the contact carrier 5 consists of insulating plastic and is ensured by the electrical insulation of the drive device from the live contact levers (Figure 1).

As a further essential feature, the contact carrier 5 according to the invention has lateral guide surfaces 23 (FIGS. 2 and 3) which interact with counter surfaces 24 (FIG. 1) on the walls of the switching chamber 1. The contact carrier is manufactured as a one-piece multifunctional part so that the guide surfaces 23 face the counter surfaces 24 with only a small tolerance. As a result, forces acting transversely to the pivoting plane of the contact carrier 5 are introduced over a large area into the walls of the switching chamber 1, while the bearing arms 15 with the pins 16 (FIGS. 2 and 3) and the associated bearing points 4 are free from these additional stresses. For the effectiveness of this support of the contact carrier 5, it contributes that the guide surfaces 23 and the counter surfaces 24 are attached as far as possible from the pins 16, namely on the cheeks 11, between which the current-carrying contact levers 8 are located (FIG. 1).

The counter surfaces 24, one of which is partially visible in FIG. 1, are arranged in an arc shape around the bearing journal 16 in accordance with the swivel radius of the contact carrier 5.

The arrangement described is equally suitable for single-pole or multi-pole circuit breakers. The explained support of the contact carrier against lateral forces has a particularly advantageous effect in the case of multi-pole circuit breakers with a small distance between the adjacent switching chambers, because in these circuit breakers the mutual influence of the adjacent poles by forces originating from the current is pronounced.

Claims

claims 1. Low-voltage circuit breaker with a switching chamber (1) and a contact carrier (5) pivotably arranged in the switching chamber (1) for receiving contact levers (8) with the following features: - Receiving openings (12) for a bearing pin (10) passing through the contact lever (8), - receiving pockets (14) for contact force springs (13), - lateral bearing arms (15) for the pivotable mounting of the contact carrier (5) in bearing points (4) of the switching chamber (1) for the purpose of transferring the contact carrier (5) into an on position or an off position , Bearing means (21) for a hinge pin (22) for coupling the contact carrier (5) to a drive device (6) of the circuit breaker for pivoting the contact carrier (5) into the switch-on position or the switch-off position, characterized in that - the contact carrier (5 ) to limit a lateral deflection to the direction of the pivoting lateral guide surfaces (23) for cooperation with counter surfaces (24) of the switching chamber (1) of the circuit breaker, and the complete contact carrier (5) with the above-mentioned features in one piece as a multifunctional part Plastic is made. 2. Movable contact carrier according to claim 1, characterized in that the bearing arms (15) have laterally projecting cylindrical pins (16) for engaging in adapted bearing points (4) of the switching chamber. 3. Movable contact carrier according to claim 1 or 2, so that the contact carrier (5) has receiving means (17) for an end position retaining spring (18). , Movable contact carrier according to claim 3, so that further receiving means (17) are provided for an end position retaining spring (18) and both receiving means (17) are arranged symmetrically on the contact carrier (5). 5. Movable contact carrier according to claim 4, so that the receiving means (17) for the end position retaining springs (18) are arranged in the lateral bearing arms (15) of the contact carrier (5). 6. Movable contact carrier according to one of claims 3 to 5, characterized in that the end position retaining spring (18) is designed as a helical compression spring and the support means provided for its support (17) are each designed as a receiving pocket for one end of the associated end position retaining spring (18) is. 7. Movable contact carrier according to one of claims 3 or 5, characterized in that the receiving means is designed as a receiving pin for engaging in the end position retaining spring designed as a helical compression spring (18). 8. Movable contact carrier according to claim 6, characterized in that for the use of end position retaining springs (18) with a wall thickness of the bearing arms (15) exceeding the diameter, the bearing arms (15) have a recess on a narrow side with oppositely arranged wall surfaces (20) that the end position retaining springs (18) are centered with a protrusion on both sides over the wall thickness of the bearing arm (15). 9. Low-voltage circuit breaker according to claim 3 or one of the following, characterized in that the end position retaining spring (s) (18) between the receiving means (17) on the contact carrier (5) and a rear wall (2) of the switching chamber (1 ) extends or extend and that between the end position holding springs (18) and the contact levers (18) on the contact carrier (5) an apron (24) is arranged as protection against the effects of switching gases. 10. Movable contact carrier according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the plastic is a fiber-reinforced plastic.