FR2839196A1 - Current security limiter circuit breaker contact mechanism having isolating container with rotating switching shaft having symmetrical springs and contact bridge contacting via control cams. - Google Patents

Abstract

The contact element has an isolating container (4) with a rotating switching shaft (6) and a rotating contact bridge (10) and two sets of torsion springs, and connection bars (24). The switching shaft has springs (36) in symmetry with a contact bridge via control cams (34).

Description

project the electric arc into the chamber (26).

  The invention relates to a contact arrangement for current limiting protection circuit breakers in the low voltage range, in particular for current limiting power circuit breakers, with an insulating housing, comprising : a switching shaft rotatably mounted around a fixed transverse axis in the insulating housing, a rotary contact bridge which extends in a housing provided with a clearance, the switching shaft along the median plane of the pole and which has, opposite and in point symmetry both contact parts which cooperate with fixed contacts in the switching on position and control cams, two pairs of tension springs with contact force, are each on opposite sides of the contact bridge, arranged inside the switching shaft, with first ends of springs fixed on the contact bridge and second ends spring mites fixed on the switching shaft, the first spring ends and the second spring ends being respectively opposite to each other in point symmetry on each side of the contact bridge, and two connection bars each connected with the one of the fixed contacts and which, in the event of very high currents, cause an electrodynamic passage of the contact bridge from the position of

  switching on to the repulsion position.

  EP-0 314 540 B1 discloses such a contact arrangement for a multipolar low voltage power circuit breaker with an insulating housing, which has a switching shaft which is rotatable about a fixed transverse axis by means sliding bearings made in the housing, the axis being perpendicular to the longitudinal median plane of each pole. Each pole includes two fixed contacts connected with connection bars, a rotary contact bridge which extends along the median plane in a housing provided with a clearance, the switching shaft and the opposite contact parts. to the others, which cooperate in the switching-on position with the fixed contacts, and two tension springs mounted inside the switching shaft, which act on the contact bridge and thus ensure a determined contact pressure of the parts contact on the fixed contacts, one end of each tension spring cooperating with a drive element of the switching shaft. The two springs are mounted in the housing provided for the contact bridge, the other end of each spring being mounted on a fixing element of the contact bridge. The two fastening or drive elements, respectively, of the two springs are opposite to each other in point symmetry with respect to an imaginary axis of rotation of the contact bridge or of the fixed transverse axis of the shaft switching, respectively. This arrangement of the springs ensures a free displacement capacity of the imaginary axis of rotation of the contact bridge relative to the fixed transverse axis of the switching shaft, and simultaneously allows a torque to force to distribute the pressure evenly. contact as well as an elastic positioning of the contact bridge with two degrees of freedom in translation, the contact bridge being maintained in an equilibrium position thanks to the self-centering effect of the springs on the median plane. The connection bars with the fixed contacts are made in the form of loops so that when they are crossed by a short-circuit current, they generate electrodynamic forces repelling the contact bridge against the effect of the force of tension springs towards repulsion position. In such a contact arrangement, there is a risk that the movable contact bridge, projected by the electrodynamic forces in the event of a short circuit, damages its stop or falls too quickly, which can lead to unwanted re-strikes.

  electrical arcs and / or contact welds.

  From document EP-0560597-B1, there is known a low voltage power circuit breaker with a contact arrangement by pole which is equipped with two pairs of tension springs arranged symmetrically with respect to each other, on both sides of the contact bridge which extends in the median plane of the pole. The tension springs of each pair are arranged on both sides of the axis of rotation of the contact bridge and each have one end mounted on the contact bridge via a common retaining rod. To brake and if necessary to retain the contact bridge pushed back by electrodynamic effect from the fixed contacts, an opposite end of the springs is mounted on the respective ends of a rod produced as a transverse axis, arranged to slide in a switching shaft engagement notch, and the contact bridge has a pair of control cams arranged in point symmetry which are designed so that in the section at the end of the repulsion stroke of the bridge contact, they each cooperate with one of the rods to slow the movement of the contact bridge. The rods are mounted with limited displacement in the interlocking notches, the opposite interlocking notches in point symmetry extending approximately along the active line of the associated springs. The springs ensure elastic positioning of the contact bridge in the recess of the switching shaft and here define the imaginary axis of rotation of the contact bridge relative to the switching shaft. The profile of the control cams arranged with respect to the movable contact parts causes a displacement of the rods in the interlocking notches as well as a continuous tension of the springs corresponding to the pivoting movement of the contact bridge towards the position of repulsion, with an accumulation of energy in the springs. The profile of the control cams can be designed so that the contact bridge engages in the repulsion position; and the rotatably mounted switching shaft is actuated by a power circuit breaker actuating mechanism and the opening travel of the contact bridge is limited such that rotation of the switching shaft causes during the setting movement

  off-circuit lifting of the rods from the control cams.

  During the pivoting movement of the contact bridge towards the repulsion position, the active line of each spring moves and shortens the lever arm here, whereby the return force torque exerted by the springs on the bridge contact is reduced. The disadvantages of this contact arrangement are the additional need for the movable rods and the insufficient effect of braking in the event of high repulsion forces due to the low friction surfaces as well as the low coefficients of friction between the

  steel rods and copper contact bridge.

  In the case of a contact arrangement according to document EP-978 858-A2, four tension springs responsible for the contact pressure attack tabs articulated between the engagement notches of the rotary contact bridge and on the shaft. switching, the articulated legs being able to pivot so that the contact bridge projected by electrodynamic effect cannot automatically fall back into the closed position. According to a contact arrangement according to document WO-99 62092-A1, four tension springs exerting the contact pressure attack between four rods. Two of the rods are mounted in housings of the switching shaft and directly attack the rotary contact bridge. The two other rods are guided in displacement in slots of the switching shaft and engage in the tabs connected to the contact bridge, these also having the effect that the contact bridge projected by electrodynamic effect cannot fall back automatically in the closed position. The disadvantage of these two solutions is that costly and complex tabs to be connected to the switching shaft are necessary and that, on the other hand, by the forced retention of the contact bridge in the projected position, a protective circuit breaker equipped such a contact arrangement is not suitable for contact arrangements

selective switching.

  The invention therefore aims to simplify a contact arrangement with improved delay behavior of the contact bridge

  rotating projected by electrodynamic effect.

  From a contact arrangement of the aforementioned type, the objective is achieved according to the invention by the fact that in the switching shaft, elements making additional springs are arranged at point symmetry with respect to the transverse axis, which in the event of electrodynamic repulsion, come in motion inhibiting connection with the contact bridge via the control cams. Advantageous improvements of the invention emerge from the

description of the drawings.

  In the event of a very high current flow following a short circuit in the electrical installation to be protected by the protective circuit breaker, control cams produced on the contact bridge projected by electrodynamic effect come into active connection with spring elements mounted in the switching shaft, whereby the bridge

  contact is braked or actively inhibited in its movement.

  When the contact bridge falls back into the switching-on position due to the tension springs at contact force and, if necessary, additionally as a result of the pushing back of an end stop, the bonding by force cooperation described above acts

  also inhibitively on the movement of the contact bridge.

  There is thus obtained a delay of the contact bridge in the whole so as to prevent a fall of the contact bridge in the position of switching on in time before the final opening of the contact arrangement by triggering protective members. The inhibition function can be influenced in a multiple manner according to the usual techniques by a constructive configuration and / or by a dimensioning of the control cams and of the spring elements, for example in the sense that the inhibitory function more strongly influences the fallout in the switch-on position as the switch to the repulsion position. The proposed contact arrangement does not require any technologically complex part to manufacture and fix in order to obtain the aforementioned braking or inhibit on effect. Protective circuit breakers fitted with such contact arrangements are advantageously suitable for protective circuit breakers which, at the appearance of an extremely high current, in particular a short-circuit current, either stop automatically in connection with members protective devices or are separated from the short-circuit current by other protective circuit breakers within a circuit breaker arrangement constituted by protective circuit breakers selectively staggered in terms of their capacity to

short circuit current load.

  An advantageous inhibitory behavior is obtained for the contact bridge pushed back by electrodynamic effect when by means of a usual technical constructive configuration and / or by a dimensioning of the control cams and of spring elements, the contact bridge can overcome a maximum of the couple of forces to be inhibited between the on position and the repulsion or reverse position, respectively. By configuring and / or dimensioning the control cams and / or the spring elements, it is also possible to produce interlocking links between the control cams and / or the spring elements at the end of the repulsion stroke. The projected contact bridge is thus retained after reaching the repulsion position until S it is detached from this closing position after the tripping of the protective circuit breaker when the final opening of

the contact arrangement.

  An advantageous improvement of the invention, from the technological point of view, lies in the fact that the spring elements are produced in the form of leaf springs which are housed at one end in the switching shaft, which cooperate with the cams and are supported with an intermediate region against the switching shaft. For this purpose, it is advisable that the control cams opposite to each other in pairs are made in the shape of a nose and the free ends are made in the shape of convex arcs with respect to the control cams. From a technological point of view and from a cost point of view, it is advantageous to mount together respectively two second spring ends of a pair of tension springs and the linked end of one of the elements springing up around pins which are themselves -same parallel to the transverse axis in second notches in the switching shaft. It is inexpensive to produce the pairs of tension springs as double U-shaped tension springs with a connecting piece between the first spring ends of the individual tension springs. By avoiding retaining rods for hanging the first spring ends, the tension springs are simply mounted with the connecting pieces in notches of the bridge

of contact.

  To ensure that the movements of the contact bridge take place safely, it is provided * an oblong kou through which is guided a fixed mounting axis extending in the transverse axis of the switching shaft. By the polar composition of the switching shafts from associated pole-by-pole switching shaft segments, the contact arrangement is suitable for circuit breakers.

  protection which can be composed by modules.

  Other details and advantages of the invention appear from the following embodiment explained with the aid of drawings. These show: FIG. 1, an embodiment, shown in perspective, of the contact arrangement according to the invention in the switching on position; Figure 2, a sectional representation along the median plane xy according to Figure 1, the contact arrangement being in the switching position; FIG. 3, a representation in section along the median plane xy according to FIG. 1, the contact arrangement being in the repulsion position; and Figure 4, a perspective representation of a spring element

  as a detail of Figures 1 to 3.

  The contact arrangement 2 according to the inventi on of FIGS. 1 to 3 is provided for a pole of a multipolar low voltage power circuit breaker not shown in detail. The circuit breaker comprises an insulating housing 4 in several parts, a switching lock to be actuated manually or by a motorized drive, input and output connection elements as well as tripping devices for overload and short circuit. In the housing 4, a switching shaft 6 is rotatably mounted around a transverse axis z fixed, the axis kansversa1 z extending perpendicular to the median plane xy of the pole. The switching element 6 is made up of switching shaft segments associated by pole. The switching shaft 6 has lateral recesses 8 in which engage mechanical connection means (not shown) for the switching locking to enter. A rotary contact bridge 10 extends along the median plane xy in a housing 12 provided with a clearance, the switching shaft 6, and has contact parts 14 opposite to each other, which cooperate with fixed contacts 16 outside of the switching shaft 6 in the on position. The contact bridge 10 has an oblong hole 11 with which it is mounted on a fixed mounting axis 7 extending in the transverse axis z of the switching shaft 6. In the housing 12 two respective tension springs 18 are arranged on both sides of the contact bridge 10 and the median plane xy and apply the necessary contact force between the parts

  contact 14 and fixed contacts 16.

  The tension springs 18 have a first spring end 21 mounted on the contact bridge 10 and a second spring end 22 mounted on the switching shaft 6. On each side of the contact bridge 10, the first spring ends 21 are opposite in point symmetry with respect to the point axis of symmetry of the contact bridge 10, and the second spring ends 22 of the respective tension springs 18 are opposite in point symmetry with respect to the transverse axis z of the shaft switching 6. The tension springs 18 are arranged symmetrically with respect to the median plane xy. Two first ends of springs 21 located respectively on opposite sides of the xy plane are connected in one piece via connecting pieces 20 extending transversely, and two second ends of springs 22 lying respectively on opposite sides of the plane xy are suspended in pins 23 located transversely and made of steel. The connecting pieces 20 form, with the associated pairs of tension springs 18, double tension springs in the form of a U-shape and rest by force cooperation in the first notches 25 of the contact bridge 10. The steel pins 23 rest in second corresponding notches 27 of the switching shaft 6. To each of the two fixed contacts 16 is connected a connection bar 24 in the form of a loop. The shape of the loop has the effect that during the passage of a short-circuit current, the contact bridge 10 will be pushed back by electrodynamic forces against the force effect of the kaction springs 18 from the position of switching on according to FIG. 2 in the direction of a repulsion position according to FIG. 3. The contact arrangement 2 is further completed at the two ends by arc extinguishing units 30 fixed in the housing 4 and by electromagnetic slot motors 32 retained

  insulated from connection bars 24.

  According to the invention, two control cams 34 located opposite in point symmetry are also formed on the contact bridge 10 and two spring elements 36 are mounted in the switching shaft 6 via the steel pins 23 The control cams 34 are produced in the form of a nose on short opposite sides of the contact bridge 10 at a short distance radially from the oblong hole 11. As can be seen in more detail in FIG. 4, the spring elements 36 are produced in the form of leaf springs. They are arranged in the median plane xy and are cut by it perpendicularly in their surface. The spring elements 36 are mounted with one end, that is to say with the linked end 38 around the steel pins 23, between the two spring ends 22 of the double tension springs. At the other end, that is to say at the free end 39, the spring elements 36 are made in the shape of an arc and are opposed to the control cams 34 in pairs with their side in relief. The intermediate regions 40 between the ends 38, 39 are curved in a slightly convex shape opposite to the buttocks 42 produced

  planes on the inner wall of the switching shaft 6.

  In the event of a short-circuit current, the control cams 34 of the contact bridge 10 ejected by electrodynamic effect arrive in active connection with the free ends 39 of the spring elements 36. The spring elements 36 mounted in the switching shaft 6 with their linked ends 38 here bear with their intermediate regions 40 against the buttresses 42 in the switching shaft. The elastic forces transmitted between the free ends 39 and the control cams 34 and the friction forces which occur act against the other accelerating forces acting on the contact bridge 10. When passing the bridge contact 10 from the switch-on position shown in Figure 2 to the repulsion position shown in Figure 3, these accelerating forces are caused by the electrodynamic repulsion forces which act here against the pressure forces of the tension springs 18. When the contact bridge drops from the repulsion position shown in FIG. 3 towards the switching-on position of FIG. 2, the contact pressure forces of the tension springs 18 and , if necessary, the reverse pulse caused by the impact of the contact bridge 10 against the housing 4 causes said accelerating forces which act

  here against forces of repulsion possibly still present.

  In both directions, a movement inhibiting torque is exerted on the contact bridge 10 by the cooperation of the control cams 34 with the spring elements 36. This torque is determined individually by the conformation, the arrangement and the configuration of the material of the control cams and of the spring elements and it is adapted in the usual way to the required requirements. The adaptation can take place here with the aim that the inhibitory rotation torque goes through a maximum when passing the contact bridge 10 from the switch-on position to the position

circuit cutting.

  In the contact system 2 described above, the fallout of the repelled contact bridge 10 is delayed until the safe interruption via the triggered switching lock. A protective circuit breaker equipped with such contact systems exhibits excellent selective properties. Another possibility lies in the fact that the control cams 34 are produced in such a way that after reaching the repulsion position, they engage an interlocking link with the spring elements 36. When the protective circuit breaker is turned on off by the next trip, the switching shaft 6 moves clockwise, as shown in Figure 3, the interlocking connections between the control cams 34 and the spring elements 36 being of

  again detached by the impact of the contact bridge 19 on the housing 4.

Claims (10)

claims   1. Contact arrangement for at least unipolar current limiting safety circuit breakers in the low voltage range, with an insulating housing (4), comprising: - a switching shaft (6) mounted rotatably about an axis transverse (z) fixed in the insulating housing (4), - a rotary contact bridge (10) which extends in a housing (12) provided with a clearance, with the switching shaft (6), along the median plane (xy) of the pole and which presents, opposite and in point symmetry both contact parts (14) which cooperate with fixed contacts (16) in the switching on position and cams control (34), - two pairs of tension springs with contact force (18), each located on opposite sides of the contact bridge (10), arranged 1S inside the switching shaft (6) , with first ends of springs (21) fixed on the contact bridge (10) and second ends of springs (22) fixed on the switching shaft ation (6), the first ends of springs (21) and the second ends of springs (22) being respectively opposite to each other in point symmetry on each side of the contact bridge, and - two connecting bars (24) connected each with one of the fixed contacts (16) which, in the event of very high currents, cause an eleckodynamic passage of the contact bridge (10) from the switching on position to a repulsion position, characterized in that - in the switching shaft (6), additional spring elements (36) are arranged at point symmetry with respect to the transverse axis (z), which in the event of electrodynamic repulsion, come in motion inhibiting connection with the contact bridge (10) via the control cams (34).   2. Contact arrangement according to the preceding claim, characterized in that between the switching-on position and the repulsion position or vice versa, a maximum braking torque occurs   between the spring elements (36) and the contact bridge (10).   3. Contact arrangement according to one of the preceding claims,   characterized in that the control cams (34) and the spring elements (36) are produced in such a way that after having reached the repulsion position, they engage in a detachable engagement connection.   4. Contact arrangement according to one of the preceding claims,   characterized in that the spring elements (36) are produced in the form of leaf springs arranged in the median plane (xy), they are each housed by a linked end (38) in the switching shaft (6), they cooperate in the region of a free end (39) with the control cams (34), and they bear with an intermediate region (4)) against a stopper (42) in the switching shaft (6) and in that the control cams (34) extend along the median plane (xy).   5. Contact arrangement according to the preceding claim, characterized in that the control cams (34) are made in the shape of a nose and the free ends (39) are made in the shape of arcs.   convex relative to the control cams (34).   6. Contact arrangement according to one of the two claims   previous, characterized in that the second spring ends (22) of said tension spring pairs (18) and the linked ends (38) of the spring elements (34) are mounted around pins (23) which are themselves parallel to the transverse axis (z) in   second notches (27) in the switching shaft (6).   7. Contact arrangement according to one of the preceding claims,   characterized in that the first spring ends (21) of said pairs of tension springs (18) are connected in one piece to each other via connecting pieces (20) extending parallel to the transverse axis (z).   8. Contact arrangement according to the preceding claim, characterized in that the connecting pieces (20) are housed in   first notches (25) on the contact bridge (10).   9. Contact arrangement according to one of the preceding claims,   characterized in that the contact bridge (10) is mounted with an oblong hole (11) on a fixed mounting pin (7) extending in the axis   cross (z) of the switching shaft (6).   10. Contact arrangement according to one of the preceding claims,   characterized in that the switching shaft (6) consists of   associated switching shaft segments pole by pole.