This application is related to U.S. Patent 5,587,693, entitled "Polarized Electromagnetic Relay", filed on August 7, 1995, issued on December 24, 1996, and assigned to the same assignee as that of the present application.
The present invention relates to an electromagnetic relay featuring structure which retains the magnet in place during assembly and operation, according to the preambles of claims 1 and 4, as for example known from FR-A-2 254 873.
Electromagnetic relays generally include a frame structure for receiving a permanent magnet coupled magnetically between an electromagnetic block and an armature. Generally, cut-out portions along the magnet's perimeter align with posts protruding from a bobbin on the electromagnetic block to retain the magnet in place. Retention features, for example deformable plastic tabs located on the bobbin or other part of the frame, prevent the magnet from backing out.
Although these retention features retain the magnet on the block, however, in assembling the relay additional labor is required to align the magnet with the posts and in fixing the retention features. Further, the retention features may loosen their hold on the magnet over time due to the operation of the relay. Further still, since cut-out portions are provided on the magnet, the magnet's magnetism is reduced.
The principal objective of this invention is to provide improvements in the frame structure of an electromagnetic relay which permit controlled retention of the magnet assembly both during assembly and in operation.
These and other objects are achieved by the present invention which provides an electromagnetic relay according to claims 1 and 4.
Advantageously, the invention provides that the magnet retention element formed on the at least one of the pole pieces retains the magnet in place between the electromagnetic block and the armature. During operation the magnet retention element prevents the magnet from moving out of position.
Preferably, the permanent magnet consists of a bar-shaped or plate-shaped three-pole magnetized permanent magnet disposed between the free ends of the pole pieces, which magnet is magnetized to have the same poles at its lengthwise ends adjacent to the pole pieces and to have the opposite pole intermediate its ends adjacent to the central portion of the armature which is balanced upon this pole.
For better understanding of the invention, reference is made to the following description of an exemplary embodiment thereof, and to the accompanying drawings wherein:
Referring now to Figure 1, there is shown an electromagnetic relay of the present invention. The relay is of bistable operation and of single-pole double-throw contact arrangement. The relay comprises a base 10 of insulating material which defines a main or bottom plane for the relay. A pair of stationary or fixed contact terminals 11 and 12 are fastened in the base 10; these fixed terminals 11 and 12 are disposed perpendicular to the bottom plane and are provided with fixed contacts 13 and 14. A movable contact terminal 15 is disposed parallel to the fixed contact terminals. All the terminals are inserted into slots 16 (not visible) in the base 10 and are fixed by caulking or by any other suitable sealant or method. Further, coil terminals 17 and 18 and a common coil terminal 19 are fastened in the base 10 in a similar manner. A pair of suppression resistors 20 or other components may be arranged on the base 10 and connected to the coil terminals 17, 18 and 19 by clamping their wires between clamping nuts 21 in the base and fork-like clamping claws 22 of the respective coil terminals. In a single input version (not shown), the common coil terminal 19 as well as one of the suppression resistors 20 may be omitted.
An electromagnet block 30 arranged on the base 10 comprises a bobbin 31 with a pair of coils 32 and 33 wound thereon between end flanges 34 and 35 and a center flange 36. An iron core 37 of cylindrical shape is inserted axially into the bobbin and coils and is coupled at its ends to a pair of plates-like pole pieces 38 and 39 which are arranged in recesses 341 and 351, respectively, of the end flanges 34 and 35 and are provided with through holes 381 and 391, respectively, corresponding in diameter to the core 37.
A plate-like elongate permanent magnet 40 is disposed along one lateral side of the bobbin in a plane perpendicular to the base plane and bridging the end flanges 34 and 35 as well as the pole pieces 38 and 39. A magnet retention element 42 is formed on each of the pole pieces 38 and 39 to prevent the magnet 40 from backing out. As shown in Figures 2 and 3, the retention element 42 is a projection extending inwardly from a planar surface 41 of each pole piece 38 and 39. The projection is preferably stamped into each of the pole pieces 38 and 39.
The permanent magnet 40 is magnetized in a three-pole manner so as to have the same magnetic poles (south poles S) at both ends and the opposite pole (north pole N) in its center. An elongate, plate-like armature 50 which is slightly bent into a V-shape, is balanced on the center pole N of the permanent magnet 40 so as to form air gaps between its end portions and either one of the pole pieces 38 and 39. Either end of the armature is divided into a pair of legs 51 and 52, respectively, by means of recesses 53 and 54, respectively.
A strip-like movable contact spring 55 which is made from a resilient material like stainless steel, is fastened to the central part of the armature 50 by means of rivets 56 or the like. A pair of movable contacts 57 and 58 are fixed to the ends of the movable spring 55 by welding or any other suitable method. Since the movable spring 55 is made from a metal having poor conductivity, a flexible composite copper braid 62 is welded directly between the movable contacts 57 and 58 and the movable spring 55 to carry the load current between these movable contacts and the movable contact terminal 15.
The movable spring has a pair of torsion pivot arms 59 extending transversely in opposite directions from a central portion thereof and defining a pivot axis for the armature 50. Each of the pivot arms 59 has an eyelet 60 for fastening the movable spring 55 and the armature 50 on the center flange 36 of the bobbin 30. For receiving the pivot arms 59, the bobbin 30 forms a pair of posts 43 extending from the center flange 36 on either side of the armature, and the pivot arms may be fastened by any suitable method.
When the relay parts are assembled along the broken lines shown in Figure 1, the central part of the braid 62 is welded to the terminal 15. Further, winding terminals 44, 45 and 46 which are anchored in the bobbin flanges 34, 35 and 36, are connected by welding or any other suitable method to the coil terminals 17, 18 and 19. The assembled relay is shown in Figure 4. A plastic cap, not shown, may be put over the assembled relay to form a closed casing together with the base 10.
In operation which the coils 32 and 33 are deenergized, the armature 50 is held or kept latched in either of the two stable positions on either one of the pole pieces 38 or 39, respectively. For moving the armature from one position to the other, a voltage pulse is applied across an appropriate coil 32 or 33 in case of a dual input wiring. In this case, the two coils 32 and 33 are wound in a common direction and have end terminals 44 and 45 as well as a common terminal 46. Armature transfer will occur by applying a voltage pulse across one of the coils 32 or 33. In case of a single input wiring, the two coils 32 and 33 are connected in series, and the center winding terminal 46 as well as the common coil terminal 19 can be omitted. In this case, armature transfer will occur by toggling the voltage pulse polarity across the two coils 32 and 33 connected in series.
An exploded view of an alternative embodiment of the electromagnetic relay is shown by Figure 5. The relay generally operates in the same manner and comprises the same components as the relay shown by Figures 1-4, except for the pair of torsion pivot arms 59 included in the latter. Specifically, a magnet 100 is secured to a bobbin 102 by two pole pieces 104 and 106 having a magnet retention element 108 to prevent the magnet 100 from backing out.
When the relay parts are assembled along the broken lines shown in Figure 5, a movable spring 110 is fastened to an armature 112 on a center flange 114 of the bobbin 102 by means of rivets 116 or the like. A pair of movable contacts 118 and 120 are fixed to the ends of the movable spring 110 by welding or any other suitable method. The bobbin 102 is provided on a base 122 having a bottom plane which is perpendicular to fixed terminals 124 and 126. Fixed contacts 128 and 130 are disposed through fixed terminals 124 and 126 and braid 132 to secure the fixed terminals 124 and 126 to the relay. The central part of the braid 132 is welded to terminal 134. Further, winding terminals 136, 138 and 140 which are anchored in the bobbin flanges 142, 144 and 146, are connected by welding or any other suitable method to coil terminals 148, 150 and 152 to fully assemble the relay.
The embodiments described herein are merely illustrative of the principles of the present invention. Various modifications may be made thereto by persons ordinarily skilled in the art, without departing from the scope of the invention as defined by the claims.