POLARIZED ELECTROMAGNETIC RELAY

Abstract: A polarized electromagnetic relay comprises a movable block including a pair of permanent magnet units, each composed of a parmanent magnet and a pair of generally U-shaped mag­ netic plates attached to opposite magnetic poles of said par­ manent magnet, respectively, each said magnetic plate hav­ ing a first end and a second end, said first end and second end of each of said magnetic plates being opposed when attached to the poles of said parmanent magnet, respectively, and a supporting member for supporting said parmanent magnet units at opposite ends thereof, respectively, and for actuating contact members responsive to movements of said parmanent magnet units: a core having opposite ends placed between the first ends of said magnetic plates, respectively; a yoke having opposite ends, each formed by a pair of opposing end pieces, the second ends of said magnetic plates being arranged in spaces, each defined by said oppos­ ing end pieces, respectively; a spool including a through-hole formed longitudinally through which said core is inserted, flanges formed at opposite ends and a center portion thereof, respectively, a plurality of protrusions protruding outwardly in both sides of each of said flanges, and a coil wound around said spool; and a pair of base members, each having grooves and re­ cesses for receiving the protrusions of said flanges of said spool, protrusions formed on side surfaces of inner walls of said base member for engaging with the protrusions of said spool by a longitudinal movement of the base member and contact members responsive to said movable block, said base members being assembled at said spool from both ends thereof.

Description: The present invention relates to a polarized electromagnetic relay (hereunder referred to as "PE relay") which comprises an electromagnetic block including an iron core and a coil wound thereon, and a pair of permanent magnet units. In the specification of a European patent which was published under the number 127308 on December 5 1984, there is proposed a polarized electromagnetic relay which has a core on which a coil is wound, a yoke having a pair of legs at each end and a pair of movable armature blocks each having a permanent magnet and pole pieces, the pole pieces being disposed in working gaps between the pairs of legs and the core and the armature blocks being slidably supported by guides arranged perpendicularly to the axis of the core. The specification of U.S. Patent No. 4,563,663, which was issued on January 7 1986 and which corresponds to German patent application No. 3320000 which was open to inspection on January 19 1984, proposes a permanent magnet relay having a core surrounded by a coil and a yoke with two side walls at one end, opposite to and on either side of one end of the core, and a movable member with a permanent magnet at its centre and two iron pieces arranged between the one end of the core and each respective side wall of the yoke. An example of a conventional PE relay is disclosed, for example, in U.S. Patent No. 4,538,126. Referring to Fig. 1, a magnetic circuit construction of the conventional PE relay includes a generally I-shaped iron core 91 on which an energizing coil 92 is wound, a yoke 93 having at each of the opposite ends thereof a pair of opposing end pieces 93a and 93b and a movable block 97. The block 97 is composed of a supporting member of a non-magnetic material having at the opposite ends thereof permanent magnet units 96a and 96b, respectively. Each of the units 96a and 96b is composed of a permanent magnet 95 and a pair of magnetic plates 94a and 94b attached to the magnetic poles of the magnet 95, respectively. The opposite ends of the core 91 are disposed between the yoke end pieces 93a and 93b, respectively, to form four magnetic gaps between the opposite end surfaces of the core 91 and the end pieces 93a and 93b of the yoke 93. The magnet units 96a and 96b are arranged such that each of the magnetic plates 94a and 94b is positioned in one of the four gaps to form energizing spaces, with the end piece 93a, the magnetic plate 94a, the end of the core 91, the magnetic plate 94b and the end piece 93b being layered. The movable block 94 responds to a direction of current to be supplied to the coil 92 to move in either direction A or B under a guidance of a coil spool (not shown) or a base member (not shown) to thereby actuate contact members (not shown). With such construction of the conventional relay, if the core 91 is not arranged exactly with respect to the yoke 93 or the magnetic plates 94a and 94b are not manufactured precisely, there may be an air gap G between the end piece 93b and the magnetic plate 94b as shown in Fig. 1B even when the core 91 is in contact with the plate 94a, resulting in a variation of magnetic resistance which makes a stable switching operation between the contact members impossible. Further, with such air gap G, when the magnet unit 96a is attracted to the side of the end piece 93a and the magnetic plate 94a comes in contact with the core 91, the plate 94b may vibrate, which causes a chattering phenomenon to occur at a time of switching. In order to obtain an improved dimensional accuracy, it is necessary to bent the respective end pieces 93a and 93b of the yoke 91 at exactly right angle, making the manufacturing of the relay difficult. Furthermore, in the conventional structure, the core 91 and the end pieces 93a and 93b are arranged oppositely at the same height. Therefore, in order to transmit a magnetic force exerting on the plates 94a and 94b to contact members (not shown) disposed outside the permanent magnet units 96a and 96b, the movable block 97 for supporting the magnet units should have an actuating part formed to avoid the contact with the end pieces 93a and 93b. As a result, it becomes impossible to transmit a composite force exerting on the magnet units 96a and 96b to the contact members efficiently. The actuating member satisfying the above requirement should be so thin that it is impossible to obtain a sufficient mechanical strength of the relay. To resolve this problem, the height and thickness of the movable block 97 should be large enough, respectively, which leads an increased size of the relay. Further, the magnet units 96a and 96b tend to move in the same direction. However, since the units 96a and 96b are connected to each other by the supporting member, it is difficult to obtain a smooth switching operation. This is due to the facts that it is difficult to move a long member such as the movable block 97 in parallel because of friction between the magnet units 96a and 96b and the guide member (not shown) and that one of the magnet units tends to delay in operation with respect to the other. Bending and/or twisting of the movable block 97 which is long with respect to its width may affect the smooth movement of the movable block adversely. In one conventional relay, four sets of contact members are arranged on a single long base member (not shown) to achieve an effective use of magnetic flux paths and an arrangement of a number of contacts. Therefore, the productivity of the base member may be lowered due to an additional probability of the occurrence of defective lead terminals and/or movable contact springs which constitute the contact members. Further, since the length of the base member is large compared with the width thereof, the tendency of bending and twisting thereof is increased, and thus dimensional accuracy of an assembled relay is lowered and relative positions of the contact members (not shown) may vary, causing a malfunction to occur. In the specification of a European patent, which was published under the number 157029 on October 9 1985, there is proposed a polarized relay having a yoke body which is bifurcated at one end, and a core wound with a coil, one end of the core being disposed within the bifurated portions of the yoke body and being of a polarity which is different from that of each of the bifurcated portions. A movable C-shaped permanent magnet block having its legs in the spaces between the bifuracted portions and the end of the core is moved according to the energisation of the core. An object of the present invention is to provide an improved PE relay. In one embodiment to be described below a bistable type electromagnetic relay comprises: a movable block including a pair of permanent magnet units, each composed of a permanent magnet and a pair of generally U-shaped magnetic plates attached to opposite magnetic poles of said permanent magnet, respectively, each said magnetic plate having a first end and a second end, said first end and second end of each of said magnetic plates being opposed when attached to the poles of said permanent magnet, respectively, and a supporting member for supporting said permanent magnet units at opposite ends thereof, respectively, and for actuating contact members responsive to movements of said permanent magnet units; a core having opposite ends placed between the first ends of said magnetic plates, respectively; a yoke having opposite ends, each formed by a pair of opposing end pieces, the second ends of said magnetic plates being arranged in spaces, each defined by said opposing end pieces, respectively; a spool including a through-hole formed longitudinally through which said core is inserted, flanges formed at opposite ends and a center portion thereof, respectively, a plurality of protrusions protruding outwardly in both sides of each of said flanges, and a coil wound around said spool; and a pair of base members, each having grooves and recesses for receiving the protrusions of said flanges of said spool, protrusions formed on side surfaces of inner walls of said base member for engaging with the protrusions of said spool by a longitudinal movement of the base member, and contact members responsive to said movable block, said base members being assembled at said spool from both ends thereof. Embodiments of the present invention will be described below, by way of example, with reference to the accompanying drawings in which: Figs. 1A and 1B are diagrams of a basic structure of a conventional PE relay; Fig. 2 is a perspective view of an embodiment of the present invention; Fig. 3 is a perspective view of a portion of the embodiment shown in Fig. 2, in a disassembled state; Fig. 4A and 4B are diagrams for describing a magnetic structure of the embodiment shown in Fig. 2; Figs. 5A and 5B are diagrams for illustrating an operation of the magnetic structure shown in Fig. 4A, in principle; Fig. 6 is a cross sectional view of a modification of the structure shown in Fig. 4A for illustrating an effect of the present invention; Figs. 7A to 7C are diagrams of the first, the second and the third modifications of the magnetic structure shown in Fig. 4A, respectively; Figs. 8A and 8B are cross sectional views of the fourth and the fifth modifications of the structure shown in Fig. 4A, respectively; Figs. 8C and 8D are cross sectional views of the first and the second modifications of the structure shown in Fig. 7B, respectively; Figs. 9A and 9B are views for illustrating a manufacturing process of the portion of the relay shown in Fig. 3; Figs. 9C and 9D are views to show portions of the structure in Fig. 3 in detail, respectively; Fig. 10 is a view for illustrating a portion of the structure shown in Fig. 3 in an assembled state; Fig. 11 is a view to show a modification of a portion of the structure shown in Fig. 3; and Fig. 12A to 12C are views for illustrating an operation of a contact arrangement in the structure shown in Fig. 11. In the drawings, same reference numerals depict same structural elements. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 2, an embodiment of the invention comprises a movable block 6 including a pair of permanent magnets, an electromagnetic block 20 including an iron core and a yoke, a pair of base members 7a and 7b equipped with contact members (70a and 70b, in Fig. 3) and a cover member 8 for covering the base members 7a and 7b. The relay shown in Fig. 2, which is of a bistable type, will be described in detail with reference to Fig. 3. Referring to Fig. 3, the movable block 6 is composed of a supporting member 60 and permanent magnet units 4 and 5 provided in opposite end portions of the supporting member 60, respectively. Each of the magnet units 4 and 5 is composed of the permanent magnet 43(53), a pair of generally U-shaped magnetic plates 41 and 42(51 and 52) attached to opposite magnetic poles of the magnet 43(53), respectively. In this embodiment, the plates 41 and 51 are attached to N poles of the magnets 43 and 53, respectively, and the plates 42 and 52 are attached to S poles of the magnets 43 and 53, respectively. The magnetic plates 41, 42, 51 and 52 are of magnetic material such as iron. The supporting member 60 includes supporting portions 65 for supporting the units 4 and 5, contact spring actuating parts 64 provided on both sides of each supporting portion 65, a connecting portion 62 having four bearing protrusions 61a, 61b, 61c and 61d which constitute a bearing portion and an insert-molded reinforcing frame 63. The electromagnetic block 20 is composed of the core 1, a coil spool 2, a coil 27 wound on the spool 2 and a yoke 3. The core 1 is of magnetic material such as pure iron and inserted into a through hole 24 formed longitudinally in the spool 2. The spool 2 has flanges 21a, 21b and 21c provided at both ends and a center thereof, respectively. The flanges 21a and 21c are formed with paired legs 25a and 25c, respectively. The legs 25a have protrusions 22a and 24a on both side thereof for engagement with the base 7a, and the legs 25c have similar protrusions 22c and 24c on both side thereof for engagement with the base 7b. The flange 21b is formed with paired legs 25b. The legs 25b have protrusions 22b and 24b on both sides thereof. The flange 21b further includes a pair of pins 26a and 26b formed on an upper portion thereof which constitute a rotary shaft for the movable block 6 and each of which has a generally semicircular cross section. The yoke 3 is of magnetic material such as iron and has a pair of upright end pieces 31a and 31b at one end thereof and a pair of upright end pieces 32a and 32b at the other end thereof. The yoke 3 is fixedly supported by the paired legs 25a, 25b and 25c of the flanges. The base members 7a and 7b have contact members 70a and 70b, respectively. The member 70a includes a movable contact spring 72a having one end fixed to a common terminal 71a and the other end positioned between a stationary contact terminal 73a (e.g. a make side terminal) and another stationary contact terminal 74a (e.g. a break side terminal). The member 70b includes a movable contact spring 72b having one end fixed to a common terminal 71b and the other end positioned between stationary contact terminals 73b (e.g. make side) and 74b (e.g. break side). A switching operation between the make and break sides is performed by the actuating part 64 of the movable block 6. The base member 7b is constituted identically to the base member 7a with an arrangement of the contact members being symmetrical with respect to the base member 7a. Movable contacts (not shown) are formed on both surfaces of free ends of the contact springs 72a and 72b, respectively. A stationary contacts (not shown) is formed on an inner surface of each of the electrically conductive terminals 73a, 73b, 74a and 74b, to face to the electrically conductive springs 72a and 72b. Each of the base members 7a and 7b is formed with grooves 75 and recesses 77 and protrusions 76 and 78 for assembling purpose to the spool 2. That is, the spool 2 is fixedly secured to the base members 7a and 7b by engaging the protrusions 22a and 24a, and the protrusions 22c and 24c with the grooves 75 and the protrusions 76 of the base members 7a and 7b, respectively. The protrusions 22b and 24b are engaged with the recesses 77 and the protrusions 78 of the bases 7a and 7b. A pair of coil terminals 79a and 79b are press-fitted to either one of the base members 7a and 7b for an electrical connection to the coil 27. The relay is assembled by assembling the movable block 6 to the electromagnetic block 20 with the opposite ends 1a and 1b of the core 1 being sandwiched between the magnetic plates 41, 42 and 51, 52, respectively, and putting the cover 8 thereon. In this embodiment, the spool 2, the base members 7a and 7b and the cover 8 are of electrically insulative resin material. An operation of the embodiment of the invention will be described with reference to Figs. 4A, 4B, 5A and 5B. As mentioned previously, the relay of the present invention is composed, basically, of the block 20 (including the core 1, the coil 27 and the yoke 3) and the movable block 6 including the pair of the magnet units 4 and 5. As also mentioned previously, the end pieces 31a and 31b formed in the one end portion of the yoke 3 are formed in a facing relation by bending them at right angle, and the end pieces 32a and 32b formed in the other end portion of the yoke 3 are bended similarly. The height of the pieces 31a, 31b, 32a and 32b are determined to be lower than the position of the core 1. Each of the magnetic plates 41, 42, 51 and 52 has an upper end 41a, 42a, 51a and 52a and a lower end 41b, 42b, 51b and 52b, respectively. The core ends 1a and 1b are positioned between the upper ends 41a and 42a of the plates 41 and 42 and between the upper ends 51a and 52a of the plates 51 and 52, respectively. The movable block 6 is positioned such that the lower plate ends 41b and 42b are positioned within a space defined between the yoke end pieces 31a and 31b in facing relations thereto and the lower plate ends 51b and 52b are positioned within a space defined between the yoke end pieces 32a and 32b. The plates 41 and 51 and the plates 42 and 52 serve as N poles and S poles, respectively, due to the permanent magnets 43 and 53. On the other hand, the core 1 is magnetized by a current supplied to the coil 27 wound thereon, with the core ends 1a and 1b being opposite magnetic polarities which depend upon the direction of the current. The movable block 6 is pivotted in an arrow direction (Fig. 4A) due to an attractive or reactive force exerting between the stationary poles by the magnets 43 and 53 and the switchable poles of the core 1 produced by energization of the coil 27. A center shaft 69 of the pivot motion of the block 6 is constituted with the pins 26a and 26b of the spool 2 and the protrusions 61a, 61b, 61c and 61d of the movable block 6. In Fig. 5A, the magnet units 4 and 5 are shown in a state in which the plate end 42b of the unit 4 is attracted to the side of the yoke end piece 31a and the plate end portion 51b of the unit 5 is attracted to the side of the yoke end piece 32b. Magnetic flux ø A passes from the magnet 43 through the plate end 41a - the core end 1a - the core end 1b - the plate end 52a - the magnet 53 - the plate end 51b - the yoke end piece 32b - the yoke end piece 31a - the plate end 42b - the magnet 43, providing a closed magnetic circuit to hold the attracted condition. When a current is supplied to the coil 27 such that the core ends 1a and 1b become an N pole and an S pole, respectively, reactive forces are produced between the core end 1a and the plate end 41a and between the core end 1b and the plate end 52a and attractive forces are produced between the core end 1a and the plate end 42a and the core end 1b and the plate end 51a. As a result, the movable block 6 is pivotted to a position shown in Fig. 5B. Magnetic flux ø B forms a closed magnetic circuit in the path, the magnet 43 through the plate end 41b - the yoke end pieces 31b - the yoke end pieces 32a - the plate end 52b - the magnet 53 - the plate end 51a - the core ends 1b - the core end 1a - the plate end 42a - the magnet 43. Even when electric current supply is cut off, the block 6 hold the state by itself due to the magnetic flux of the magnets 43 and 53. That is, the block 6 operates bidirectionarily to form a bistable type relay. Fig. 6 shows a magnetic structure wherein a distance A between a right side surface of the core end 1a and an inside surface of the yoke end piece 31b does not coincide with a distance B between an inside surface of the magnetic plate 42 and an outside surface of the plate 41 (A > B) due to insufficient precision in bending work on the yoke end pieces 31a and 31b. In such case, there may be a gap provided between the end piece 31b and the plate end 41b even when the magnet unit 4 is moved by a total magnetic force F exerted thereon and the core end 1a becomes in contact with the plate end 42a. However, due to an attractive force acting between the end piece 31b and the plate end 41b and a reactive force acting between the end piece 31a and the plate end 42b, the magnet unit 4 is subjected to a rotational force Q acting around a fulcrum point P and rotated clockwisely within a range defined by guide members (not shown) while tilting, so that the end piece 31b can be in contact with the plate end 41b. In this manner, the core end 1a, the yoke end pieces 31a and 31b and the plate ends 41a, 41b, 51a and 51b can contact with each other, respectively, even if the bending inaccuracy of the yoke 3 and/or the assembling inaccuracy of the electromagnet block 20 is not negligible. Therefore, it is possible to realize a stable contact switching operation with minimized variation of magnetic resistance of the magnetic circuits. Further, since the plates 41 and 42 can contact with the end pieces 31b and 31a reliably, respectively, there is no vibration of the magnet unit 4 and thus it is possible to restrict the chattering at the moment of contact switching. These effects are commonly observed for the magnet unit 5. A magnetic structure of a monostable type PE relay according to the present invention will be described below. Referring to Fig. 7A, a first modification of the magnetic structure shown in Fig. 4 is made so that the size of the yoke end piece 31a (32b) is made different from that of 31b (32a). Specifically, the area of the yoke end piece 31b (32a) facing to the magnet unit 4 (5) is larger than that of the yoke end piece 31a (32b) facing to the magnet unit 4 (5). Therefore, the magnetic resistance on the side of the yoke end piece 31a (32b) is larger than the other, and the magnetic resistance balance is disturbed. Thus the magnet units 4 and 5 are attracted to the yoke end pieces 31b and 32a, respectively, due to a composite force of the magnetic forces and the spring forces when deenergized. When a current is supplied to the coil 27 such that the core end 1a becomes an S pole, the magnet units 4 and 5 are attracted to the yoke end pieces 31a and 32b, respectively, to actuate the contact members (not shown). Referring to Fig. 7B, a second modification of the structure shown in Fig. 4 is made so that the yoke end pieces 31a and 32b are removed to provide an unbalanced magnetic resistances. In this modification, it may be possible to provide stopper members (not shown) on the base members 7a and 7b or the cover 8 to restrict the movements and vibrations of the plates 42 and 51, respectively. Referring to Fig. 7C, a third modification of the structure in Fig. 4 is made so that the areas of the plate ends 42b and 51b are reduced to obtain an unbalanced magnetic resistances. Other magnetic structures of a monostable type PE relay having residual plates will be explained. Fig. 8A shows a fourth modification of the structure in Fig. 4. In this modification, a residual plate of non-magnetic material is used to form an air gap in the magnetic circuit thereof. Thick residual plates 44a are provided on an inside surface of the plate end 41a and on an outside surface of the plate end 42b, respectively, and thin residual plates 44b are provided on an inside surface of the plate end 42a and on an outside surface of the plate 41b, respectively. The plates 44a and 44b function to release the contact condition of the plates 41 and 42 with the yoke end pieces 31a, 31b and the core end 1a smoothly when the magnet unit 4 is moved and to make the magnetic resistances of the circuit unbalanced due to the difference in thickness. Referring to Fig. 8B, a fifth modification of the structure in Fig. 4 is made so that the residual plates 44a and 44b are attached to the core end 1a on the side of the end piece 31b and on the side of the yoke end piece 31a, respectively. Fig. 8C shows a modification of the magnetic structure having the yoke 3 shown in Fig. 7B. In this modification, the yoke end piece 31a is eliminated and the residual plates 44 are attached to the inside and outside surfaces of the plate 41. Fig. 8D shows another modification of the structure having the yoke 3 shown in Fig. 7B. In this structure, a stopper 33 of non-magnetic material such as non-magnetic alloy is mounted by, for example, pressure pressing, instead of the eliminated yoke end piece 31a. In any of Figs. 8A to 8D, the magnetic balance is broken positively. Therefore, the magnet unit 4 is attracted to the side of the yoke end piece 31b due to a composite force including the spring forces acting on the contact members (not shown), when it is deenergized. In Figs. 8A and 8B, the magnetic unbalance is provided by the difference of the residual plate thickness. Although described for the magnet unit 4, the same is applicable for the magnet unit 5 which is symmetrical thereto about the shaft 69 (Fig. 4A). The supporting member 60 shown in Fig. 3 will be described with reference to Figs. 9A to 9C. A plurality of the supporting members 60 can be produced simultaneously described as follows: preparing a plate of non-magnetic, high strength metal such as phosphor bronze and having a plurality of mutually connected reinforcing frames 63 (Fig. 9A); insert-molding the frames 63 with insulating resin; forming the supporting parts 65, the actuating parts 64 and the connecting portions 62 including the bearing protrusions 61a, 61b, 61c and 61d; and cutting portions shown by dotted lines (Fig. 9B) away. With the insert-molding of the frames 63, it is possible to restrict bending and/or twisting thereof to be occurred at the connecting portions 62 between the magnet units 4 and 5. Thus it is possible to produce the supporting members 60 which can provide a high assembling accuracy at low cost. A production line of the members 60 may be automated easily, according to this method. In the best mode, a portion of the frame 63 is exposed to minimize the resin molded portion as shown in Fig. 9B. This is important because, when, in the insert-molding process, resin injection is not sufficient, the thickness of resin on opposite surfaces of the frame 63 may becomes non-uniform and asymmetrical and thus small bendings of the frame 63 may occur during shrinkage of the resin when hardened. On the other hand, when resin is injected with too much pressure, the frame 63 may be bent and/or deformed. Therefore, it is desired to minimize the molded portion and to increase the number of connecting points connecting the frames 63 each other in the molding process. However, if the thickness of the resin can be controlled suitably, it may be possible to mold all of the frames 63 and then to form the members 60. Referring to Fig. 9C, each actuating part 64 is formed with a slit 640 into which the contact member is to be inserted. In upper portions of the yoke end pieces 31a and 31b, which are lower in level than the core end 1a, spaces are provided. The actuating part 64 can transmit linearly a magnetic force acting on the magnetic plates 41 and 42 with the aid of the spaces and provide a sufficient structural strength without increasing the height of the supporting member 60. Fig. 9D shows the bearing structure for guiding the rotation of the movable block 6 (Fig. 3), in detail. The pins 26a and 26b protruding upwardly from the flange 21b of the spool 2 are disposed in between the bearing protrusions 61a and 61b provided in the connecting portion 62 of the supporting member 60 and in between the bearing protrusions 61c and 61d provided in the same, respectively. That is, the pins 26a and 26b are held loosely with the connecting portion 62 being there-between, so that the movable block 6 can be pivotted in arrow directions. In this bearing structure, minute particles generated by friction between the pins 26a, 26b and the protrusions 61a, 61b, 61c, 61d may be released therefrom. Therefore, a smooth movement can be maintained for the bearing portion for a long period of time due to a lubricating function thereof. Further, this does not prevent a slight tilting of the magnet units 4 and 5. As mentioned above, the supporting member 60 is compact in size and light weight while having a sufficient mechanical strength and accuracy to realize a satisfactory contact switching operation. An assembling of the spool 2 and the base members 7a and 7b will be described with reference to Figs. 3 and 10. The base member 7a is pushed up to the structure until the protrusions 22a of the spool 2 reach the bottom of the grooves 75 and then slided laterally and fixed, along an arrow C. The base member 7b is assembled similarly, with the sliding direction being opposite as shown by an arrow D. That is, since the spool 2 and the base members 7a and 7b are fixedly assembled easily by the fittings between the protrusions 22a, 22b, 22c, 24a, 24b and 24c of the spool 2, and the protrusions 78 and 76 of the base members 7a and 7b, it is possible to prevent vibration of the structure at the contact switching time. After the base members 7a and 7b are assembled to the spool 2, lateral movements thereof are prevented by inner walls of the cover 8 assembled thereafter, to thereby prevent an accidental disassembling of the structure. Since this assembling process can be achieved without using fixening members such as screws, the assembling process of the relay can be facilitated with minimum cost. Further, due to the employment of the paired base members 7a and 7b, the number of parts to be mounted on each base member becomes a half comparing with the conventional base member and thus the probability of defective products is reduced considerably, resulting in an improved productivity. Furthermore, due to the length of the base member which is a half comparing with the conventional base member, the bending and/or twisting thereof is minimized, resulting in an improved assembling accuracy. Since the movable block 6 is rotated about the shaft 69 (Fig. 4A), a positional relationship between the make-side and the break-side of the contact member becomes symmetrical about a point and therefore the base members 7a and 7b may be identical in structure. It should be noted that the protrusions 24a, 24b and 24c may be omitted, if necessary. Further, since the grooves 75 are formed so as to penetrate partially the base members 7a and 7b (See Fig. 10), if sealing process of the structure with using resin for sealing the base members 7a, 7b and the cover 8 is employed, same resin adheres to the protrusions 22a, 22b and 22c to provide an additional fixening strength. A modification of the base member shown in Fig. 3 will be described with reference to Fig. 11. The base member 7c has two contact members 70c and 70d. The member 70c includes a pair of movable contact springs 721a and 722a. The springs 721a and 722a have one ends fixed to common terminals 711a and 712a, and the other ends opposing to stationary contact terminals 73a and 74b, respectively. The common terminals 711a and 712a are connected together within the base member 7c and protrude from the bottom thereof as a single terminal. It is possible to regulate a contact pressure to be preliminarily applied to the contact springs 721a and 722a by twisting the respective common terminals 711a and 712a separately. In order to drive the contact members 70c and 70d, a pair of slits may be formed in the actuating part 64 of the movable block 6 to form three-prolonged fork. A construction of the contact member of the base member 7c shown in Fig. 11 will be described with reference to Figs. 12A to 12C. In order to drive the contact member, the actuating part 64 comprises an outer stad 641, a center stad 642 and an inner stad 643 as mentioned with reference to Fig. 11. The stationary contact terminals 73a and 74a have stationary contacts 731 and 741, respectively, and the movable contact springs 721a and 722a have movable contacts 7211 and 7221, respectively. The springs 721a and 722a have contact pressures predetermined such that they are in contact with the terminals 73a and 74a, respectively. The stad 643 pushes the spring 722a so that the contacts 7221 and 741 are broken and the stad 642 pushes the spring 721a so that the contacts 7211 and 731 make (Fig. 12A). The magnet unit (not shown) is moved slightly by magnetic force in a direction E, so that the pushing forces of the stad 642 and 643 acting on the springs 721a and 722a are released. Then, due to the predetermined contact pressures, the contacts 741 and 7221 make together and the contacts 731 and 7211 are kept in contact (Fig. 12B). When the magnet unit (not shown) moves further, the stad 641 pushes the spring 721a to break the contact between the contacts 731 and 7211 (Fig. 12C). Thus, an early-make-before-break contact in which the movable contact 7211 is opened after the movable contact 7221 is closed is realized. It is possible to assemble the base member 7b having a contact member composed of a single movable contact spring and the base member 7c having a contact member composed of a pair of movable contact springs to a single spool, so that a variety of contact constructions are realized in a single relay. As described hereinbefore, according to the present invention, it is possible, in view of magnetic circuit construction, to obtain a stable closed magnetic circuit even if the assembling accuracy thereof is not satisfactory, and, in view of contact driving construction, to improve the assembling process as accurate as possible, therefore, a highly reliable relay is achieved.

Claims: A polarized electromagnetic relay including a pair of permanent magnet units (4, 5), each having a permanent magnet (43, 53) and a pair of magnetic plates (41, 42; 51, 52) attached to opposite magnetic poles of the permanent magnet (43, 53), respectively, a bar-like core (1), a yoke (3) having opposite ends, each end formed by a respective pair of opposing end pieces (31a, 31b; 32a, 32b), a spool (2) including a hole (24) formed longitudinally therethrough, the core (1) being inserted through the hole (24), flanges (21a, 21b, 21c) formed, at opposite ends and at a centre portion of the spool (2) respectively, a coil (27) wound around the spool (2), and a base (7a, 7b) having contact members (70a, 70b) responsive to the magnet units (4, 5), the polarized electromagnetic relay being characterised in that each of the magnetic plates (41, 42, 51, 52) of the permanent magnet units (4, 5) is a generally U-shaped plate having a first end (41a, 42a, 51a, 52a) and a second end (41b, 42b, 51b, 52b), the first end and the second end of each of the magnetic plates (41, 42, 51, 52) being opposed when attached to the poles of their respective permanent magnets (43, 53), in that the pair of permanent magnet units (4, 5) is supported by a supporting member (60) at opposite ends thereof respectively to form a movable block (6) for actuating the contact members (70a, 70b) responsive to movements of the permanent magnet units (4, 5), in that the core (1) has opposite ends (1a, 1b) placed between the first ends (41a, 42a; 51a, 52a) of the magnetic plates (41, 42, 51, 52), respectively, in that the second ends (41b, 42b, 51b, 52b) of the magnetic plates are arranged in spaces, each space being defined by the opposing end pieces (31a, 31b; 32a, 32b) of the yoke (3), respectively, in that the spool (2) further includes a plurality of protrusions (22a, 24a, 22b, 24b, 22c, 24c) protruding outwardly on both sides of each of the flanges (21a, 21b, 21c), in that the base (7a, 7b) is separated into a pair of base members (7a, 7b), each base member having grooves (75) and recesses (77) for receiving the protrusions (22a, 24a, 22b, 24b, 22c, 24c) of the flanges (21a, 21b, 21c) of the spool (2), and in that protrusions (76, 78) are formed on the side surfaces of the inner walls of each of the base members (7a, 7b) for engaging with the protrusions (22a, 24a, 22b, 24b, 22c, 24c) of the spool (2) by a longitudinal movement of the base members (7a, 7b) and the contact members (70a, 70b) responsive to the movable block (6), the base members (7a, 7b) being assembled with the spool (2) from both ends thereof. A polarized electromagnetic relay as claimed in claim 1 further including residual plates (44, 44a, 44b) of non-magnetic material placed within gaps defined by the opposite ends (1a, 1b) of the core (1) and the opposing first ends (41a and 42a, 51a and 52a) of the magnetic plates (41, 42, 51, 52) of the permanent magnet units (4, 5), respectively. A polarized electromagnetic relay as claimed in claim 2 wherein the residual plates (44a, 44b) are different in thickness to make the magnetic resistance of the magnetic circuit unbalanced. A polarized electromagnetic relay as claimed in claim 3 further including residual plates (44a, 44b) having different thicknesses placed within gaps defined by the end pieces (31a, 31b, 32a, 32b) of the yoke (3) and the second ends (41b, 42b, 51b, 52b) of the magnetic plates (41, 42, 51, 52) of the permanent magnet units (4, 5), respectively. A polarized electromagnetic relay as claimed in claim 1 wherein the opposed areas of the end pieces (31a, 32b) of the yoke (3) are disposed diagonally and the second ends (42b, 51b) of the magnetic plates (42, 51) which are disposed diagonally are different from the opposed areas of the remaining end pieces (31b, 32a) of the yoke (3) which are disposed diagonally and the remaining ends (41b, 52b) of the magnetic plates (41, 52). A polarized electromagnetic relay as claimed in claim 1 wherein the contact member (70c, 70d) of at least one of the base members (7c) has two movable contact springs (721a, 722a) fixed to a common terminal (711a, 712a) on one end thereof and opposed to different stationary contact terminals (73a, 74a) on the other end thereof. A polarized electromagnetic relay as claimed in claim 1 wherein the supporting member (60) has magnet unit supporting portions (65) of insulating resin formed at opposite ends thereof, a connecting portion (62) of insulating resin for connecting the magnet unit supporting portions and a non-magnetic reinforcing frame (63), the magnet unit supporting portions and the connecting portion being formed on the reinforcing frame by insert-molding. A polarized electromagnetic relay as claimed in claim 7 wherein the reinforcing frame is partially exposed in the connecting portion. A polarized electromagnetic relay as claimed in claim 7 wherein the connecting portion has first and second bearing protrusions (61a, 61b) protruding horizontally and third and fourth bearing protrusions (61a, 61d) protruding horizontally in the opposite direction to the first and second protrusions and wherein the flanges (21b) of the spool (2) which are formed at the centre thereof include first and second pins (26a, 26b) protruding upwardly, the first and second pins (26a, 26b) being disposed between the first and second bearing protrusions (61a, 61b) and between the third and fourth bearing protrusions (61c, 61d), respectively, to form a rotary drive shaft of the movable block (6). A polarized electromagnetic relay as claimed in claim 1 wherein two end pieces (31a, 32b) of the yoke (3) which are arranged diagonally to each other are removed whereby each of the opposite ends of the yoke (3) has only one end piece (31b, 32a). A polarized electromagnetic relay as claimed in claim 10 further including residual plates (44) of non-magnetic material placed within gaps defined by the opposite ends (1a, 1b) of the core (1) and the opposing first ends (41a, 52a) of the magnetic plates (41, 52) of the permanent magnet units (4, 5) on the side of the pieces (31b, 32a) of the yoke (3), respectively. A polarized electromagnetic relay as claimed in claim 11 further including residual plates (44) having different thicknesses placed within gaps defined by the end pieces (31b, 32a) of the yoke (3) and the second ends (41b, 52b) of the magnetic plates (41, 52) of the permanent magnet units (4, 5), respectively. A polarized electromagnetic relay as claimed in claim 10 wherein the contact member (70c, 70d) of at least one of the base members (7c) has two movable contact springs (721a, 722a) fixed to a common terminal (711a, 712a) on one end thereof and opposed to different stationary contact terminals (73a, 74a) on the other end thereof. A polarized electromagnetic relay as claimed in claim 10 wherein the supporting member (60) has magnet unit supporting portions (65) of insulating resin formed at opposite ends thereof, a connecting portion (62) of insulating resin for connecting the magnet unit supporting portions and a non-magnetic reinforcing frame (63), the magnet unit supporting portions and the connecting portion being formed on the reinforcing frame by insert-molding. A polarized electromagnetic relay as claimed in claim 14 wherein the reinforcing frame is partially exposed in the connecting portion. A polarized electromagnetic relay as claimed in claim 14 wherein the connecting portion has first and second bearing protrusions (61a, 61b) protruding horizontally and third and fourth bearing protrusions (61c, 61d) protruding horizontally in opposite direction to the first and second protrusions and wherein the flanges (21b) of the spool (2) which are formed at the centre thereof include first and second pins (26a, 26b) protruding upwardly, the first and second pins (26a, 26b) being disposed between the first and second bearing protrusions (61a, 61b) and between the third and fourth bearing protrusions (61c, 61d), respectively, to form a rotary drive shaft of the movable block (6).

Inventors: KAMO, YUICHI, MIKAMI, NOBUO
Applicants: NEC CORPORATION
Application year: 1986
Main classification: H01H51
IPC codes: H01H51