EP1241688A1

EP1241688A1 - A contact device for medium and high voltage circuit breakers and switches.

Info

Publication number: EP1241688A1
Application number: EP01830180A
Authority: EP
Inventors: Matteo Technoelectric s.r.l. Anelli; Oris Technoelectric s.r.l. Lorenzoni; Giuseppe Technoelectric s.r.l. Ziliani
Original assignee: Technoelectric Srl
Current assignee: Technoelectric Srl
Priority date: 2001-03-15
Filing date: 2001-03-15
Publication date: 2002-09-18

Abstract

The electric connection between the stationary contact (10) and mobile contact (20) is made by a plurality of bridges (30) each being extended from the stationary contact to the mobile contact and having the outer wall pressed elastically by a spring (41) which in turn receives a loading force directed radially towards the device axis (A-A) from a case (50), the spring being a flexure spring (41) and its connection with the bridge (30) being a restrain joint (53) - (Fig. 4).

Description

This invention refers to a contact device for medium and high voltage circuit breakers and switches (in the following, only circuit breakers will be referred to) wherein the mobile contact is connected with the stationary contact by a plurality of bridges along which the mobile contact may slide until it is no longer in contact with the bridge and the electric continuity in the device is broken.
The most advanced prior art as known to the applicant is described with reference to figures 1, 2, 3 that will be commented in detail further on. The device is comprised in a peripheral case wherein the stationary and mobile contacts of substantially equal outer diameter are received; each leaf spring of a plurality of leaf springs positioned peripherally in the case presses a relevant bridge that connects electrically the stationary contact with the mobile contact when in make position. Once the mobile contact is retracted as a consequence of an opening outer action, it is no longer in contact with the bridge so that the circuit breaker is open. By a make operation, the mobile contact penetrates within the bridges thanks to their round edges and resets in the make position.
The disadvantage of the prior art lies in the notable time for assembling the parts of the device, mobile and stationary contacts, bridges, leaf springs and the case, even if each bridge is usually hold sideways in a guide or housing made in the inner wall of the case.
This invention solves the problem of switching off a current temporarily along an electric line and is a contact device for medium and high voltage circuit breakers wherein the electric connection between the stationary contact and mobile contact is made by a plurality of bridges, each being extended longitudinally from the stationary contact to the mobile contact and having the outer wall, viz. the wall opposite the longitudinal axis of the device, pressed elastically by a spring which in turn receives the loading force from a case covering the two contacts totally or partially, the loading force being directed radially towards the longitudinal axis of the device so that the bridge urges with its ends, respectively, the mobile contact and the stationary contact; the invented device is characterized in that the spring is a flexure spring connected with a corresponding bridge by a restrain joint. Preferably, the flexure spring is restrained on that bridge end which loads the mobile contact. Preferably again, the case part which presses the plurality of springs has an inner peripheral tooth against which the free ends of the springs engage in order to make permanent the connection between the stationary contact, the bridges and the case.
The main advantage of the invention is that the various parts of the device may be assembled very quickly; even the disassembling of said parts is very quick since an auxiliary tool penetrates along the inner wall of the case untill the springs are disengaged from the case tooth so allowing to remove the case and have access to the various parts without damaging them; finally, this device is more compact than the known ones as the springs are positioned into an end of the bridges.
The prior art as known to the applicant is described in the appended Figures 1, 2, 3 (figures 1, 3 are longitudinal cross sections and figure 2 is a front view) whereas the invention is described by way of example and with reference to the drawing wherein

Fig. 4 is a longitudinal section,
Fig. 5 is a cross section through B-B of figure 4 and
Fig. 6 is a cross section of a detail.

Figures 1 and 2 show a device in make position; the stationary contact 1 and mobile contact 2 of equal outer diameter are connected electrically by a plurality of bridges 3 each urged on the contacts by a corresponding spring 4 which in turn is hold in position by a case 5 and a central extention 6 engaged in a recess 7 made in the same bridge; the bridges 3 are prevented from sliding along the contacts since one of their ends is received in a corresponding seat in the contacts. In Fig. 3 the device appears in opening position; the mobile contact 2 is retracted along the longitudinal axis A-A and is disconnected from the bridges 3.
Figures 4 and 5 show an invented device in make position; the tubular contacts, stationary 10 and mobile 20, are connected electrically by a plurality of bridges 30; the stationary contact 10 has seats 11 wherein corresponding ends of bridges are hold to prevent sliding of the bridges on the stationary contact; the upper wall of each bridge, in correspondence with the mobile contact, has a transversal recess 40 wherein the eye shaped end of a flexure spring 41 is forced; the shape of the recess and of the eye end are such as to realize a restrained joint between the spring 41 and the bridge 30, that eye shaped end being formed by bending a steel plate suitable for that spring, as a very simple technical solution. The mechanical characteristics of the springs and said strained joint cause both ends of the bridges to urge on the contacts so as to assure the desired electric continuity in the device. In the assembling operation, the tubular case 50 has been directed along the mobile contact 20 untill it meets the springs 41 and bends them to cause the necessary loading effect on the springs. Inside the end of case 50 there is a peripheral tooth 12 and the free ends 13 of springs 41 engage against such tooth in order to make permanent the connection between the stationary contact, the bridges and the case. This effect in the device is improved by the following feature; the outer diameter of the mobile contact 20 is smaller than the outer diameter of the stationary contact 10 so that the bridges 30 are sloping from an upper position on the stationary contact to a lower position on the mobile contact and the outer wall of the bridges has a hollow 51 wherein the flexure springs 41 are received when they are bent by the tubular case 50 so as to allow the peripheral edge of case 50 to stop against a shoulder 52 made at the upper end of the hollow. The bridges are held sideways within longitudinal guides, not shown in the drawing, made in the case inner wall. As in the prior art, such guides may be large enough to receive even two bridges side by side. The bridges are supported by the peripheral edge of the stationary contact 10 when the mobile contact 20 is retracted.
Fig. 6 shows that the restrain joint 53 between the flexure spring 41 and the bridge 30 is realized by forcing an end of the blade spring into a corresponding seat in the bridge.

Claims

A contact device for medium and high voltage circuit breakers wherein the electric connection between the stationary contact (10) and mobile contact (20) is made by a plurality of bridges (30) each being extended longitudinally from the stationary contact to the mobile contact and having the outer wall pressed elastically by a spring (41) which in turn receives a loading force directed towards the device longitudinal axis (A-A) from a case (50) covering the two contacts, characterized in that the spring is a flexure spring (41) and the connection of the spring (41) with the bridge (30) is a restrain joint.
A contact device according to claim 1 characterized in that the restrain joint is realized on that bridge end which urges on the mobile contact (20), the spring being extended over the outer wall of the bridge towards the opposite end thereof.
A contact device according to claim 2 characterized in that the case part which provides the plurality of springs (41) with the loading force has an inner peripheral tooth (12) against which the free ends (13) of the springs engage in order to prevent the case from removing.
A contact device according to claim 3 characterized in that the outer diameter of the mobile contact (20) is smaller that the outer diameter of the stationary contact (10) so that the bridges (30) are sloping from an upper position on the stationary contact to a lower position on the mobile contact and the outer wall of the bridges has a hollow (51) wherein the flexure springs (41) are received when they are bent by the tubular case (50) so as to allow the peripheral edge of the latter (50) to stop against a shoulder (52) made at the upper end of said hollow (51).