HK1061305B - Switching contact arrangement for a power switch - Google Patents

Description

Switching contact arrangement for an electric switch

The invention is in the field of electric switches and can be applied to the design of a rigid element used as a contact carrier for a contact.

In the known electrical switch of this type, a plurality of contact levers forming the contacts are rotatably fixed by means of a bearing pin on a contact carrier, which has at least three bearing elements (E0222686B 1) for radially supporting the bearing pin. The contact carrier comprises a metal frame which consists of two side walls and a plurality of pins which connect the side walls. The metal frame is hinged via a connecting pin to an insulating connecting element which serves to connect the contact carrier to a switch actuating mechanism (schaltatriebe). The two supporting elements provided at the two ends of the supporting pin are formed by the side walls of the metal frame. In order to avoid undesirable radial deflections of the contact lever bearing pins by using as little additional material as possible, in the contact carrier two intermediate bearings are provided between adjacent contact levers in the axial intermediate section of the bearing pins, forming additional bearing elements, which are here articulated on the connecting pin. In order for the connecting pins to pass through these intermediate supports, the contact brackets must have through holes. Such a bearing element, which is integrated in the contact carrier and is additional to the two outer bearing elements, must be positioned for the mounting of the bearing pin shaft, depending on its pivotability about the connecting pin.

Starting from an electric switch (E0222686B 1) having the features of the prior art described above, the technical problem to be solved by the invention is: the manufacture and assembly of the contact holder is simplified.

The above-mentioned object is achieved according to the invention in that at least three of the support elements are designed as sections of a one-piece molded part forming the contact carrier. In the context of the present invention, a one-piece shaped part is understood to be a component in which a plurality of functional elements are connected to form a single composite component which cannot be separated from one another in terms of assembly technology during the production process of the prototype, for example during an extrusion, coining, casting, injection molding or sintering process.

In one such embodiment, the three support elements are rigidly integrated in the contact carrier at defined positions as sections of the contact carrier. In this case, the three bearing elements are already aligned along the axis of the bearing pin during the production of the contact carrier, so that practically no tilting of the bearing pin due to errors occurs during the operation of the switch. The bearing pin supported in this way is subject to only a small maximum deflection even in the presence of large short-circuit currents or pulse currents and therefore has the ability to withstand high short-circuit currents and pulse currents.

The novel switching contact arrangement can have a large number of contact rods each with a single tolerance from a given nominal dimension and, if appropriate, intermediate bearings which likewise have a single tolerance from their nominal dimension, but these intermediate bearings can be part of the contact rods, since these large numbers of contact rods are divided into several parts, each of which is arranged axially between two adjacent bearing elements in a defined manner. According to such a definition of the contact rods of the various parts in the axial direction (according to the electrodynamic forces acting between them), the movement of the contact rods of a part in the axial direction is limited to the axial section of the bearing pin defined by the associated bearing element, in which case the maximum value of the movement is not greater than the sum of all the individual tolerances of the contact rods of this part and of the intermediate bearings which may be present. It is therefore possible to geometrically assign the contact rods with contact force springs in such a way that their spring force is not reduced by bending or skewing. Thus, accurately configuring the contact force spring with respect to the contact beam geometry helps to improve the ability of the switching contact arrangement to withstand both short circuit currents and pulsed currents.

An electrically insulating design for the connecting pin can be dispensed with if the shaped part is at least partially designed as a plastic molded part. The mechanical strength of such a plastic molded part can be increased by the following measures: at least one reinforcing element is embedded at least partially in the plastic molded part. Typically, for plastic mouldings, a thermosetting plastic, for example fibre-reinforced, and for reinforcing elements a steel, for example diamagnetic, is used. Furthermore, other plastics, pure or reinforced, for example by ceramic or glass fibers, can also be used for the plastic molded parts, and other metals or metal sheets can also be used for the reinforcing elements.

A preferred embodiment of the novel switching contact arrangement provides that at least one of the support elements comprises a metal part which is at least partially embedded in a plastic molding.

Such a metal piece may be part of the reinforcing element, thereby simultaneously increasing the mechanical strength of the part of the contact bracket constituting the support element.

If the metal part is designed as a sheet metal part, for example made of a diamagnetic sheet metal, a first subsection of which has undercuts (hinderschneidungen) which is embedded in the plastic molding and a second subsection of which has a hole for the passage of the bearing pin protrudes from the plastic molding, the cross section of the bearing element can advantageously be reduced such that it is not greater than the spacing between the contact rods which is required for separating the contact rods, and thus does not lead to additional widening of the contact carrier, a further advantageous development of the novel switching contact arrangement provides that the bearing element comprising metal parts is spaced apart from a metal connecting part in the axial direction of the bearing pin when the contact carrier is connected to a switching spindle (schaltwedle) which can be rotated by means of a switching actuating mechanism. In a simple manner, therefore, potential grounding (spannungsverschelppung) and insulation problems between the contact carrier and the switch actuating element can be avoided. In this embodiment, the entire material depth of the contact carrier which is already present transversely to the bearing pin axis direction can be used for the rigid embedding of the first subsection of the bearing element which consists of sheet metal.

If a mounting for the shielding body is provided on at least one of the supporting elements in the contact mount provided with a shielding body, this can help the shielding body to be supported against the gas pressure which occurs when the switch is switched on. In such a design, the size of the fastening leg section which bears laterally against the contact carrier can be reduced or, if necessary, eliminated, as a result of the reduced load.

Fig. 1 to 9 show various embodiments of the novel switching contact arrangement. In the drawings:

fig. 1 is a schematic cross-sectional view of a low-voltage circuit breaker with a switching contact arrangement consisting of a stationary contact assembly and a movable contact assembly,

fig. 2 shows a movable contact assembly with a contact carrier which is at least partially formed from a plastic molding according to a first embodiment,

fig. 3 shows a reinforcing element, which can be embedded in the plastic molding of the contact carrier according to fig. 2,

fig. 4 shows a second embodiment of a contact carrier which is at least partially formed from a plastic molding, some of the support elements which are designed as sheet metal being partially embedded in the plastic molding,

figure 5 shows a cross-sectional view of the contact holder of figure 4 taken perpendicular to the bearing pin axis,

fig. 6 shows a reinforcing element, which can be embedded in the plastic molding of the contact holder according to fig. 4,

figure 7 shows a cross-sectional view of a contact carrier with embedded reinforcing elements according to figure 6, taken perpendicular to the bearing pin axis,

FIG. 8 shows another cross-sectional view of the contact mount of FIG. 4 taken along line A-A of FIG. 5, an

Fig. 9 shows a contact lever carrier corresponding to fig. 4 with a shielding.

The electrical switch shown in fig. 1, which is used in low-voltage supply networks and has a voltage range of up to approximately 1000V, has a switching pole housing 1, in which a number of switching chambers 2 are designed in parallel according to the required number of poles. A switch spindle 4 which can be rotated by means of a switch actuating mechanism 3 is used for the joint actuation of switching contact arrangements which each consist of a fixed contact arrangement 5 and a movable contact arrangement 6. For this purpose, two levers 7 (see fig. 8) which project radially from the switch spindle 4 are each connected to a metal connecting piece 8 which is articulated to the movable contact assembly 6. These contact assemblies 5, 6 are connected in a known manner to externally accessible connecting busbars 9, 10. Two embodiments 6a and 6b of the movable contact arrangement 6 are explained below with reference to fig. 2 and 3 or fig. 4 to 9.

As is apparent from fig. 2, a contact carrier 11 belongs to the movable contact assembly 6a, which contact carrier 11 has a plastic molding 12 as an integrally formed part, which is formed during an extrusion process with the embedding of a reinforcing element as shown in fig. 3. The contact carrier is mounted rotatably in the housing 1 (see fig. 1) and can be moved by means of the switch actuating mechanism 3 (for this purpose, only one drive rod 15 is shown in fig. 1, which is mounted on a spring force store 14) via the switch spindle 4 into a switched-on position or switched-off position relative to the fixed contact arrangement 5. A plurality of contact levers 16, 17 arranged parallel to one another on the contact carrier 11 can be rotated about a bearing pin 18 relative to the contact carrier 11, wherein contact-force springs 19 (see fig. 1) pre-stress the contact levers 16, 17 in the direction of the fixed contact assembly 5. Flexible conductors 20 in the form of twisted wires or strips are used to connect the contact bars 16, 17 to the underlying connecting bus 10 in such a way that the mobility of the contact bars 16, 17 and the contact carrier 11 is not impeded during the switching process.

The number of contact levers 16, 17 mounted on the contact carrier 11 depends on the magnitude of the current that should flow through the circuit breaker during operation. As can be seen from fig. 2, of the total of 22 contact beams present, 8 contact beams 16 are shorter and have only one main contact zone 21, and not the secondary contact zones 22 and the arc angles 23, as do the remaining contact beams 17.

In the ready-to-operate state, all contact levers are arranged between the lateral cheeks 24a, 24b of the contact carrier 11 oriented transversely to the bearing pin 18. These side cheeks 24a, 24b, which are provided with mounting holes 25a, 25b for the bearing pin 18, form a first and a second bearing element for bearing the ends of the bearing pin, which is axially positioned and radially supported by means of them. A portion 29a or 29b (see fig. 3) of the reinforcing element 13, which has a through hole 27a or 27b for supporting the pin, can extend in each of the cheeks. The cheeks 24a, 24b transition downwardly to contact a support arm 26 of the bracket 11.

Due to the comparatively large width of the switching contact arrangement, when the switching contact arrangement is in the closed state, in addition to the force of the contact force spring 19, further forces due to high currents, such as short-circuit currents or pulse currents, are added, which results in the section of the bearing pin extending between the two lateral bearing elements 24a, 24b being subjected to comparatively strong bending loads.

This section of the bearing pin is prevented from flexing by an additional third bearing element which axially centrally supports the bearing pin. The third supporting element is formed by a rib 28 of the contact carrier, which rib 28 is arranged transversely to the bearing pin axis, the rib 28 being provided with a mounting opening 25c (not visible in the drawing) for the bearing pin 18, and a metal part 29c, which is part of the reinforcing element 13 and is completely embedded in the plastic molding 12, with a through-opening 27c for the bearing pin, extending within the rib 28 (see fig. 3).

Fig. 4 shows only a second embodiment 30 of the contact carrier for a second embodiment 6b of the movable contact arrangement. In this contact carrier 30, two supporting elements, which are designed as sheet metal plates 31, serve to radially support the section of the supporting pin that extends between the two supporting elements, which are designed as side cheeks 32a, 32 b. The two intermediate support elements 31 are embedded with their first subsections 33 in the plastic molding 34 of the contact carrier 30 and with their second subsections 35 project from the plastic molding.

According to fig. 5, the metal sheet 31 has undercuts 36 on the first subsection 33 embedded in the plastic molding, which serve to ensure that the respective metal sheet is reliably anchored in the plastic molding even when the bearing pin is subjected to high bending loads. The second subsection 35, which is provided with a bore 38 through which the bearing pin 37 passes, additionally has a recess 39 for accommodating a shielding 40, which is shown in detail in fig. 9. Two reinforcing elements 41, 42, one of which is shown in fig. 6, can be embedded in the plastic molding of the contact carrier, according to fig. 7.

According to fig. 8, the two metal sheets 31 are spaced apart from the metal connecting piece 8 (see fig. 1) in the axial direction in order to avoid potential grounding between the bearing pin of the contact lever, which is at a low voltage potential, and the metal connecting piece 8, which is at ground potential, and thus the switch actuating mechanism.

According to fig. 9, tongues 43 (see also fig. 5) which are inserted into the recesses 39 provided in the metal sheet are formed on the shield 40, and the shield 40 protects the turn-around region of the contact carrier 30 and further switching components, not shown further, which are located below the contact regions 21, 22 (see fig. 1) from falling burning products and condensed switching gas. The shielding 40 is therefore supported against the gas pressure generated during switching in such a way that its lateral fastening leg sections 44a, 44b fastened to the contact carrier are subjected to a lower load.

Claims (7)

1. A switching contact arrangement for an electrical switch, having a contact carrier (11; 30) to which a plurality of contact levers (16, 17) are rotatably fixed by means of a bearing pin (18; 37), wherein the contact carrier (11; 30) has at least three bearing elements for radially supporting the bearing pin, characterized in that: at least three of the supporting elements (24a, 24b, 28; 32a, 32b, 31) are designed as sections of a molded part of the contact carrier, said molded part being produced in one piece.

2. The switch contact assembly of claim 1, wherein: the molded part is designed at least partially as a plastic molded part (12; 34).

3. The switch contact arrangement of claim 2, wherein: at least one metal reinforcing element (13; 41, 42) is at least partially embedded in the plastic molding (12; 34).

4. A switch contact arrangement according to claim 2 or 3, characterized in that: at least one of the support elements has a metal part (29a, 29b, 29 c; 31) which is at least partially embedded in the plastic molding (12; 34).

5. The switch contact arrangement of claim 4, wherein: the metal part (31) is designed as a sheet metal part, a first subsection (33) of which has undercuts (36) is embedded in the plastic molding (34), and a second subsection (35) of which has a hole (38) for the bearing pin (37) to pass through protrudes from the plastic molding (34).

6. The switch contact arrangement of claim 4, wherein: when the contact carrier (30) is connected to a switching spindle (4) by means of a metal connecting piece (8), the bearing element comprising a metal piece (31) is spaced apart from the connecting piece (8) in the axial direction of the bearing pin (37).

7. The switch contact arrangement of claim 2, wherein: in the contact carrier (30) provided with a shield (40), a recess (39) for mounting the shield (40) is provided on at least one of the supporting elements.