ELECTROMAGNETIC RELAY

Abstract: 1. Electromagnetic relay containing a magnetic circuit consisting of a yoke (16) with two vertical branches (20, 22) between bases (26, 28) whereof a permanent magnet is installed, and of a moving flap closing the magnetic circuit, together with a con­ trol circuit coiled on one (20) of the vertical branches (20, 22) of the yoke, characterized in that bases (28) of the said verti­ cal branches (20, 22) are connected together by a horizontal magnetic shunt branch (34) parallel to the lines of force of the magnetic flux created by the permanent magnet.

Description: The present invention relates to an electromagnetic relay. It more especially concerns a so-called "differential" relay designed to ensure the opening of a circuit breaker which cuts off the power supply from the circuit when a fault current develops in the user circuit. Patent application FR-A-2 371 766 describes and illustrates an electromagnetic relay containing a magnetic circuit consisting of a yoke with two vertical branches between the bases whereof a perma­ nent magnet is installed and of a moving flap closing the magnetic circuit, together with a control circuit coiled on one of the verti­ cal branches of the yoke. A spring subjects the moving flap to a fle­ xible return force slightly less than the holding attraction force due to the magnetic flux created by the permanent magnet. This document proposes doing away with the necessity of shunting the permanent magnet via a shunt branch, by using a perma­ nent magnet in a very costly semi-remanent material; moreover it only proposes a basic pattern for the structure of the magnetic circuit without proposing the method of embodiment, easy to industriiialize. Document FR-A-2 448 784 describes and illustrates a type of electromagnetic relay currently employed in the field of safety con­ tactors in which the permanent magnetic is installed below the lower branch of the magnetic yoke. This arrangement, apart from the fact that it requires a more powerful permanent magnet, increases the overall height of the relay. The purpose of the present invention is to propose an elec­ tromagnetic relay which remedies the drawbacks latent in the types of relay which have just been described. For this purpose the invention proposes an electromagnetic relay, characterized in that the bases of the said vertical branches are connected together by a horizontal magnetic shunt branch parallel to the lines of force of the magnetic flux created by the permanent magnet. According to another characteristic if the invention, the said vertical branches and the said horizontal branch form a single part in magnetic material obtained by cutting out a plate and bending it parallel to the vertical direction of the said branches. The various objects, characteristics and advantages of this invention will now be detailed in the following description, provided as a nonexhaustive example, with reference to the accompanying draw­ ings: - Figure 1 is a vertical cross-sectional view of an electro­ magnetic relay in accordance with the teachings of this invention, - Figure 2 is a top view of the relay in Figure 1, the cover of the housing of the latter being removed, - Figure 3 is a perspective view of the relay in Figure 1, - Figure 4 is a cross-sectional view, at larger scale, of the cover of the housing of the relay in Figure 1, - Figure 5 is a top view of the cover in Figure 4, and, - Figure 6 is a simplified perspective view, at larger sca­ le, of the yoke of the relay in Figure 1. The electromagnetic relay 10 shown in the drawings contains a housing 12, closed by a cover 14, which contains the magnetic cir­ cuit of the relay and its control circuit. The magnetic circuit basically consists of a yoke 16 and a flap 18 closing the magnetic circuit. Yoke 16 contains two branches 20, 22 parallel and vertical (as shown in the drawings). A permanent magnet 24 is installed between the respective bases 26, 28 of the vertical branches 20, 22 of the yoke. The perma­ nent magnet has a rectangular parallelepipedic form and its two par­ allel polar faces 30, 32 are placed parallel to the vertical plane in which branches 20 and 22 of yoke 16 extend. According to the present invention the two vertical branches 20 and 22 are connected together by a horizontal magnetic shunt branch 34 which extends perpendicularly to the vertical plane of the two branches whose bases 26, 28 it connects, and parallel to the li­ nes of force of the magnetic flux created by the permanent magnet 24. As can be easily observed on Figure 6, and according to the invention, an advantageous embodiment is that yoke 16 consists of a single part formed of the two vertical branches 20, 22 and of connec­ ting branch 34. Yoke 16 can be produced very simply by cutting out the deve­ loped structure of the yoke in a thick plate, in magnetic material, then through two successive bending operations along a direction pa­ rallel to the vertical direction of the two branches. The closing flap 18 is hinged to yoke 16 close to the free end of branch 22 via a fastener 36 crimped to the said branch. In the so-called "held" position the flap lies on the hori­ zontal faces of the free ends of branches 20, 22. It is kept in this position by the magnetic flux created by the permanent magnet 24 which is guided in the magnetic circuit. A return spring 38 whose one end is secured to the fastener, and whose other end is secured to flap 18 applies to the latter an elastic return force slightly less than the holding attraction force due to the permanent magnet 24. The circuit controlling the relay here consists of a coil 40 wound round branch 20 of the yoke. When a control current flows through coil 40, the latter creates a magnetic flux reverse to that due to the magnet which suf­ fices to switch over flap 18 which then occupies its position con­ trolling the circuit breaker, shown as a dot-and-dash line in Figure 1, in which the push pin 42 operates mechanically on a component of the circuit breaker. The differential relays of the type just described are high sensitive relays, and so as to maintain the sensitivity as constant as possible in the course of time, it is necessary to provide for certain positioning of the permanent magnet in relation to the yoke. For this purpose, and according to the invention, the yoke is inserted vertically into grooves 44, 46 in the housing which co-­ operate with the lateral faces 48, 50 opposite vertical branch 22. In this way yoke 16 is locked in position transversally in relation to housing 12. The yoke is inserted into housing 12 with the permanent ma­ gnet 24 installed between bases 26, 28 and horizontal branch 34 be­ tween which it is not yet positioned accurately. The lower face 52 of magnet 24 bears on the frame of coil 20 so as to define the height of the latter in relation to the horizontal plane delimiting bases 26, 28 of the vertical branches 20, 22. Cover 14, whose position in relation to housing 12 is defi­ ned exactly when closing the housing, contains a rectangular paralle­ lepipedic recess 54. When housing 12 is closed by cover 14, the upper protruding section of yoke 16 and of permanent magnet 24 is installed in recess 54 which is of suitable shape and size. Two inclined faces 72, 74 located on sides 56 and 58 of re­ cess 54 co-operate with the flat faces 82 and 84 of bases 26 and 28 of yoke 16 so as to lock the latter in position in housing 12. An inclined face 76 located on side 58 of recess 54, through a stepping 86 in base 28, co-operates with the polar face 32 of mag­ net 24 so as to force the latter back in abutment against the inner face 62 of the vertical branch 20. In this way the magnet always oc­ cupies the same transverse position in relation to the vertical bran­ ches 20, 22 of yoke 16 and a constant air gap is maintained between the polar face of 32 of magnet 24 and the inner face 64 of the verti­ cal branch 22. In the same way the lateral and vertical positionings of magnet 24 are obtained by two inclined faces 78 and 80, formed on si­ de 68 of recess 54, which co-operate with the lateral face 70 of the permanent magnet 24. It is easily understandable that, on completion of the as­ sembly of the various components of the relay and after closing the cover 14 on housing 12 by bonding or soldering, the position of mag­ net 24 in relation to the magnetic circuit is obtained in an accura­ te, reliable and constant manner. The final setting of the relay's sensitivity is only made after it has been fully assembled and inserted into the circuit whose safety it ensures, by modifying the magnetization of the permanent magnet. This latter operation is made very easy through the position of yoke 16 and magnet 24 located in recess 54 of the cover, on either side of which two polar branches can be brought close to a magnetiza­ tion/demagnetization device.

Claims: 1. Electromagnetic relay (10) containing a magnetic circuit consisting of a yoke (16) with two vertical branches (20, 22) between bases (26, 28) whereof a permanent magnet (24) is installed, and of a moving flap (18) closing the magnetic circuit, together with a con­ trol circuit (40) coiled on one (20) of the vertical branches (20, 22) of the yoke, characterized in that bases (28) of the said verti­ cal branches (20, 22) are connected together by a horizontal magnetic shunt branch (34) parallel to the lines of force of the magnetic flux created by the permanent magnet. 2. Relay as claimed in claim 1, characterized in that the said vertical branches (20, 22) and the said horizontal branch (34) form a single part (16) in magnetic material. 3. Relay as claimed in claim 2, characterized in that the said single part (16) is obtained by cutting out a plate in magnetic material and bending it parallel to the vertical direction of the said branches (20, 22). 4. Relay according to any one of claims 1 to 3, characteri­ zed in that the said permanent magnet (24) is a rectangular paralle­ lepipedic magnet whose two polar faces (30, 32) are parallel to the vertical plane of the said branches. 5. Relay according to any one of claims 1 to 4, characteri­ zed in that it also contains a housing (12) in which the said yoke (6) is inserted, closed by a cover (14) in which a recess (54) is formed whose faces (58 and 68) co-operate with the faces (32 and 70) opposite the said permanent magnet in order to define the position of the latter in relation to the said vertical branches.

Inventors: LE ROLLAND, PIERRE, POTIRON, JEAN-YVES
Applicants: ITT INDUSTRIES INC.
Application year: 1986
Main classification: H01H71
IPC codes: H01H71