FR2513009A1 - Line protection circuit breaker with indirect thermal trigger - has direct electromagnetic ratchet with insulation over engagement point formed in cavity in armature - Google Patents

Abstract

The ratchet (2) bears upon an armature (3) at its engagement point (4). Between the armature (3) and its yoke, a heating winding is arranged along a bimetallic strip for thermal release. When the magnetic field of the current through the yoke attracts the armature (3), the ratchet (2) can be disengaged. The point of engagement (4) is covered by a moulded insulating part (8) which is either cold-pressed or injected hot into a recess in the armature (3). This part (8) may have elastic tails or tapered pawls overlapping the wall of the armature at the engagement point. It may surround a hard metallic part which is disengaged or exposed at the point of engagement but elsewhere coated with insulating material. This variant ensures a metallic contact for high ratchet pressure.

Description

Protection circuit breaker
The present invention relates to a line protection circuit breaker, the pawl of which is directly engaged with the armature of an electromagnetic trip device, the armature constituting a support for the pawl at the point of latching, and which bears, on a bimetallic strip, between this frame and the cylinder head, a heating coil which acts as a functional element of a thermal trip device.

 During the shutdown process, it may happen that a high voltage drop occurs on the heating winding of the bimetallic strip of the thermal trip unit, which can cause disruptive discharges towards the snap point of the armature. During this discharge, there is a current path which is parallel to the current path provided for the switch, and which then destroys the sensitive components. This is a problem characteristic of thermal triggers, the bimetallic strip of which carries a heating coil and which therefore include indirect heating.

 The object of the present invention is to develop a protective circuit breaker comprising an electromagnetic trip device with direct latching and a thermal trip device with indirect heating, in the case of which accidental discharges at the latching point are avoided.

 The present invention makes it possible to solve this problem, in the case of a protection circuit breaker of the type defined above, by the fact that the support at the snap point is covered by a molded piece of insulating material. Due to the potential separation at the trigger point, an electrical arc cannot therefore be established between the armature, which constitutes the support, and the pawl, during the unlatching process, even in the event of fault causing tripping of the circuit breaker. We can therefore safely benefit from the advantages of the electromagnetic trip device with direct latching. In the case of switches with indirect latching, such high voltages, which could lead to accidental discharges, cannot, it is true, not occur, because of the principle of construction of these switches, but these require the implementation of more significant means. Indirect snap-in indeed requires a larger number of components. In the case of these known switches, plastic parts have also already been used at the snap point, in order to act on the mechanical sequence of the release.

 According to the present invention, the part mounted in insulating material can be arranged in a recess in the frame. For this purpose, it can be put in place by cold pressure or can be formed directly on the frame by hot injection.

 According to another characteristic of the present invention, the molded piece of insulating material can be provided with elastic or snap-on tails, which overlap the wall of the frame at the point of latching. Such a molded part can be put in place by snap-fastening on the wall of the frame, and it is possible for this purpose also to provide, in a manner known per se, snap-on beads.

The present invention will be better understood on the basis of the detailed description of several embodiments taken as nonlimiting examples and illustrated, very schematically, by the appended drawing, in which
- Figure 1 is a partially exploded view of a direct latching protection circuit breaker
- Figure 2 is a perspective view of a thermal trigger with indirect heating and an electromagnetic trip of a circuit breaker
- Figure 3 is a section of an embodiment of the snap point
- Figure 4 is an elevational view of the locking point according to Figure 3, but without pawl
- Figure 5 is a section of another embodiment, shown identically to that of Figure 3
- Figure 6 is an elevational view of the snap point according to Figure 5
- Figure 7 is a section of another embodiment of the snap point; and
FIG. 8 is an elevation view of the latching point according to FIG. 7.

 The protective circuit breaker 1 according to FIG. 1 has a pawl 2 and an armature 3 constituting at the snap point 4, a support for the pawl 2. Between the armature 3 and its cylinder head 5, according to FIG. 2, a winding of heater 7 is arranged on a bimetallic strip 6 and acts as a functional element of a thermal trip device. When the armature 3 undergoes the attraction of the magnetic field produced by the passage of current in the yoke 5, the pawl 2 can be released from the snap point 4.

 The support at the snap point 4 is covered with a mounted part 8 made of insulating material, as is particularly clear from FIGS. 3 and 4. The mounted part 8 is placed in a recess 9 in the frame 3.

According to this first embodiment, the molded part 8 can be placed in the recess 9 by cold pressure or also by hot injection. FIGS. 5 and 6 represent another embodiment of a molded part 8, similar to that of the mode of representation of FIGS. 3 and 4.

 The molded piece 8 of insulating material can also, according to FIGS. 7 and 8, be provided with elastic or snap-on tails 10 and 11, which overlap the wall of the frame 3 at the point of latching. The snap tail 10 is thinner and tapered, which makes it particularly flexible.

 With a latching bead 12, it can be hooked in a corresponding recess of the frame 3. The elastic or snap-in tail 11 then rather serves as a reference base.

 The molded part 8 can surround a hard elastic metal part, which is released or exposed to the point of latching. This metal part is then lined with the insulation, except for the click surface itself. A metallic coating is thus obtained for a high pawl pressure, while at the same time ensuring a galvanic separation of the elements which present a risk of accidental discharge.

Claims (4)

 1.- Protective circuit breaker, the pawl of which is directly latched with the armature of an electromagnetic trip device, the armature constituting a support for the pawl at the latching point, and which bears, on a bimetallic strip, between this armature and the cylinder head, a heating coil which acts as a functional element of a thermal trip device, characterized in that the support at the snap point (4) is covered by a molded part (8) made of insulating material.  2. Circuit breaker according to claim 1, characterized in that the molded part (8) is arranged in a recess (9) of the frame (3).  3.- Circuit breaker according to claim 1, characterized in that the molded part (8) of insulating material is provided with elastic or snap-on tails (10, 11) which overlap the wall of the frame (3) at the point of snap-on.  4.- Circuit breaker according to claim 1, characterized in that the molded part (8) of insulating material surrounds a hard elastic metal part, which is released or exposed at the point of latching.