ELECTROMAGNETIC RELAY

Abstract: An electromagnetic relay has a casing of electrically insulative material which is divided by an insulating partition into a coil space for receiving an electromagnet and a switching space for receiving a contact assembly. An armature is magnetically coupled to the electromagnet and is operatively connected to the contact assembly for switch­ ing contact operation thereof in response to energization of the electromagnet. The partition extends along the entire length of the electromagnet without leaving any communica­ tion path between the coil space and the switching space, such that the electromagnet in the coil space can be insulatively separated from the contact assembly in the switching space within the length of the electromagnet.

Description: BACKGROUND OF THE INVENTION 1. Field of the invention The present invention relates to an electromagnetic relay, and more particularly to an electromagnetic relay including a mount base provided with an insulation partition for separating an electromagnet from a contact assembly, and starts from DE-A-3 202 043. 2. Description of the prior art Electromagnetic relays, particularly relays requiring a high contact rating within a small-sized casing are known to have a partition wall dividing the interior of a relay casing into two spaces, one for mounting an electromagnet and the other for a contact assembly. The relay construction having the above partition for separating the electromagnet from the contact assembly becomes more essential for designing a miniature relay in which components are densely-packed with a maximum insulation resistance between the electromagnet and the contact assembly. Prior relays having the above partition are disclosed, for example, in US-A-4,101,856, 4,302,742, and 4,339,735, in all of which the partition extends along the length of the electromagnet for separation thereof from the contact assembly. However, the partition employed in each prior art relay must have a slot or opening within its length for passing therethrough a card or like actuating member which operatively connects the electromagnet to the contact assembly in order to actuate the switching operation of the contact assembly in response to the energization of the electromagnet. Unfortunately, due to the slot or opening formed in the partition, the partition fails to achieve complete insulation between the contact assembly and the electromagnet within the entire length of the electromagnet, and therefore the slot or opening is likely to form between the electromagnet and the contact assembly a shortcut leakage path through which a possible arcing originating from the contact assembly may extend to and damage the electromagnet. With the partition of the prior relays, therefore, the electrical insulation is interrupted at a portion of the partition, thereby considerably reducing the effectiveness of the partition and providing but unsatisfactory insulation, which is a hindrance to designing a miniature relay having a high contact rating in which magnetic and electric components are required to be dense-packed at a maximum insulation resistance. DE-A-3 202 043 discloses an electromagnetic relay with the features included in the first part of claim 1. There, the free end of the movable contact is driven by the relay armature via an actuator plate. The actuator plate is slidably received in a channel which forms a communication between the coil space containing the electromagnet and the switching space containing the contact assembly. The above-indicated problem resulting from a shortcut leakage path between the electromagnet and the contact assembly is not solved satisfactorily in this known relay design. The same is even more true with respect to another electromagnetic relay known from DE-A-3 424 076, where a coupling lever transmitting the movement of the relay armature to a slider carrying the movable contacts extends through a large opening interconnecting the coil space and the switching space. SUMMARY OF THE INVENTION It is an object of the present invention to provide an electromagnetic relay in which the danger of a leakage path forming between the contact assembly and the electromagnet is substantially eliminated, thereby permitting a miniaturisation of the relay, while assuring maximum insulation between the electromagnet and the contact assembly. This object is met by the relay characterised in claim 1. The fact that the partition between the contact assembly and the electromagnet extends along the entire length of the latter, in combination with the provision of mutually overlapping flaps and skirts covering a recess through which part of the armature extends between the two spaces at an end edge of the partition, results in a highly effective insulation which eliminates the formation of any shortcut leakage path through the partition. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exploded perspective view of an electromagnetic relay; Fig. 2 is an exploded perspective view, as viewed in a different direction and shown with a majority of parts being removed, of the above relay; Fig. 3 is a longitudinal section, partly in front elevation, of the above relay; Fig. 4 is an exploded top view illustrating how a contact assembly is incorporated into the above relay; Fig. 5 is an exploded perspective view of an electromagnetic relay in accordance with an embodiment of the present invention; Fig. 6 is a longitudinal section, partly in front elevation, of the relay of Fig. 5; Fig. 7 is an exploded perspective view of an armature employed in the above relay; Fig. 8 is a top view, partly in section, of the armature; Fig. 9 is a side view of the above relay; Fig. 10 is a horizontal section of the above relay; Fig. 11 is an exploded perspective view of a modification of the electromagnet employed in the electromagnet relay; and Fig. 12 is a schematic illustration of the electromagnet of Fig. 11. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to Figs. 1 to 4, there is shown an electromagnetic relay which comprises a mount base 1 for mounting an electromagnet 30, an armature 50, and a contact assembly 70. The mount base 1 is made of electrically insulative material such as molded plastics in the form of a casing opened at its top and one longitudinal end face. A shield cover 2 of like insulative material fits snugly over the mount base or casing 1 to close the top and the end face. The casing 1 has a rectangular bottom wall 3, a pair of opposite side walls 4 and 5 extending upwardly from the lateral sides of the bottom wall 3, and an end wall 6 extending upwardly from the longitudinal end of the bottom wall 3 and joining said side walls 4 and 5 at its lateral ends. A partition 7 integrally extends from the end wall 6 between the opposed side walls 4 and 5 in parallel relation with the bottom wall 3 so as to divide the interior of casing 1 into a coil space 8 for mounting said electromagnet 30 and a switching space 9 for said contact assembly 70. Said partition 7 extends a distance greater than the length of the electromagnet 30 and terminates at an edge which is recessed with respect to the longitudinal open end of the casing 1 to leave thereat a recess 10 through which said coil space 8 is communicated with said switching space 9. Said electromagnet 30 comprises a U-shaped yoke 31 having a pair of parallel legs 32 connected by a web 33, a core 34 extending from the web 33 in parallel relation to the yoke legs 32, and a winding 36 wound around the core 34 to magnetize the free ends of the yoke legs 32 to a polarity opposite to that of the core 34. The winding 36 is carried around a coil bobbin 37 molded from electrically insulative plastics material which is embraced between the yoke legs 32 and is supported thereon by means of said core 34 being inserted through the coil bobbin 37 to be connected to the web 33 of the yoke 31. One of the yoke legs 32 is provided at its free end with a bridge member 38 which extends integrally from upper end thereof. The bridge member 38 is bent at a right angle toward the other yoke leg 32 and is then clamped thereto by any known technique for rigid connection between the free ends of the yoke legs 32, reinforcing the yoke 31 to have good dimension stability against possible shocks which may be applied thereto at the time of assembling the relay. The bridge member 38 is thus spaced upwardly from an enlarged flat pole end 35 of the core 34 and serves as a pole member of the same polarity as the yoke legs 32 but of opposite polarity to the pole end 35. The electromagnet 30 thus constructed is fixed in place within said coil space 8 with protrusions 39 formed on the yoke legs 32 being snapped in complementary eyelets 11 formed in the upper end portion of the side walls 4 and 5 of the casing 1. A plurality of coil terminal lugs 40 provided at one longitudinal end of said coil bobbin 37 extend downwardly through individual vertical slots 13 formed in an upstanding section 12 at the juncture of the end wall 6 with the partition 7 to project outwardly of the bottom wall 3 of the casing 1, as best shown in Figs. 3 and 4, for connection with an external relay control circuit. Extending horizontally from the other longitudinal end of the coil bobbin 37 are a pair of support arms 41 for pivotally supporting the armature 50. For this purpose, each support arm 41 has in its free end a bearing hole 42 with an open slit 43. Said armature 50 includes a mold block 51 of electrically insulative plastic material which holds a pair of pole plates 52 and 53 and a permanent magnet 54. The pole plates 52 and 53 have their rear end portions embedded in the mold block 51 with the permanent magnet 54 interposed therebetween so as to be magnetized to opposite polarity. Projecting transversely from either side of the mold block 51 is a pivot pin 55 which is snapped into each of said bearing holes 42 through said open slit 43 so that the armature 50 is held by said support arms 41 for pivotal movement about a horizontal axis perpendicular to the longitudinal axis of the electromagnet 30. As best shown in Fig. 3, the armature 50 has its major portion received within said coil space 8 adjacent the longitudinal end of the electromagnet 30 and is coupled thereto in such a way that said pole end 35 of the core 34 extends between the pole plates 52 and 53 and at the same time that the upper pole plate 52 extends between the pole end 35 and the bridge member 38. With this coupling, the armature 50 is driven to rotate in a direction indicated by an arrow in the figure to an operative position where the upper pole plate 52 is attracted to the pole end 35 of the core 34 when the electromagnet 30 is energized by a given polarity of voltage. When the electromagnet 30 is deenergized the armature 50 responds to rotate in the opposite direction into a stable position of Fig. 3 where the upper pole plate 52 is attracted to the bridge member 38 as the lower pole plate 53 to the pole end 35 of the core 34 for completing the magnetic circuit of the permanent magnet 54 and is retained at this stable position until the electromagnet 30 is again energized by the given polarity of voltage. In this sense, the relay of this embodiment is a polarized relay having a monostable armature operation. Integrally formed with the mold block 51 of the armature 50 is a generally L-shaped card 56 which passes around the open end of said partition 7 or through said recess 10 to extend into the switching space 9 for connection of the armature 50 with the contact assembly 70. The card 56 is formed at the free end of its horizontal segment with a catch slit 57 for coupling with a movable contact spring 71 of the contact assembly 70. The contact assembly 70 comprises the movable contact spring 71 and a pair of fixed contact plates 72 and 73 both being of generally L-shaped but having different lengths. Each of the fixed contact plates 72 and 73 carries at its one end each one of contact tips 74 and 75 and is formed at the other end with each one of downwardly extending terminal lugs 76 and 77. Said fixed contact plates 72 and 73 can be fixed to the casing 1 from the exterior thereof in a manner shown in Fig. 4. That is, the fixed contact plates 72 and 73 have their contact tip carrying portions inserted into the switching space 9 through respective ports 14 and 15 formed in the side walls 4 and 5 so as to locate the contact tips 74 and 75 in vertically spaced relation within the switching space 9, and are held in place by their side leg portions being press fitted into longitudinal grooves 16 and 17 formed in the outer surfaces of the side walls 4 and 5. The ports 14 and 15 are formed at portion below said partition 7 and adjacent to said end wall 6 such that the contact tips 74 and 75 or switching contact portion of the contact assembly 70 is disposed deep inside of the switching space 9 so as to be apart a maximum distance from said recess 10 leading to the coil space 8 where the electromagnet 30 is mounted, thus substantially insulating the electromagnet 30 from the switching contact portion by the partition 7, end wall 6 and the side walls 4 and 5. Said terminal lugs 76 and 77 of the fixed contact plates 74 and 75 are fitted respectively in vertical grooves 18 and 19 continuous with the longitudinal ends of said lengthwise grooves 16 and 17 opposite to the ports 14 and 15 so that they extend downwardly and outwardly of the bottom wall 3. Said movable contact spring 71 is in the form of an elongate blade having its one end portion connected to a contact base 80 with a terminal lug 79 and having on the upper and lower sides of the other end portion contact tips 81 which are engageable with the respective one of the contact tips 74 and 75 of said fixed contact plates 72 and 73. The movable contact spring 71 can be also fixed to the casing from the exterior thereof in a manner shown in Fig. 4. The movable contact spring 71 is introduced through the open end of the casing 1 into said switching space 9 and is secured to the casing 1 by inserting the lateral edges of said contact base 80 in a press-fitted manner into end slits 20 formed in the inner surface of the side walls 4 and 5 adjacent the bottom wall 3 with the terminal lug 79 extending outwardly through a notch 22 in the bottom wall 3 of the casing 1. Formed in the middle portion of the movable contact spring 71 is an aperture 82 which has its edge 83 inserted into said catch slit 57 at the free end of the card 56 for connection therewith. Thus, the movable contact spring 71 is operatively connected to the armature 50 and is movable therewith in response to the energization and deenergization of the electromagnet 30. Said switching contact portion including the contact tip 81 of the movable contact spring 71 is accessible through either port 14 or 15 from the exterior of the casing 1 and therefore can be adjusted its contact gap by the use of a suitable adjusting tool insertable through the port 14 or 15. The ports 14 and 15 are closed by the shield cover 2 fitted over the casing 1. Referring to Figs. 5 to 10, there is shown an electromagnet relay in accordance with an embodiment of the present invention which is similar in construction to the relay described above except for a contact assembly 90 and for the detailed configuration of the armature 50. The like numerals are employed to designate like parts. In this embodiment, the contact assembly 90 includes two sets of contact units each comprising a movable contact spring 91 and a pair of fixed contact plate 92 and 93. The fixed contact plates 92 and 93 of each contact unit are introduced into the switching space 9 of the casing 1 by inserting the carrier portion for contact tips 94 and 95 through each of the ports 14 and 15 in the side walls 4 and 5 and are fixed to the casing 1 by their side legs press-fitted into longitudinal grooves 24 in the outer surface of each of the side walls 14 and 15. Like above, terminal lugs 96 and 97 integral with the fixed contact plates 92 and 93 of each contact unit are received in vertical grooves 25 continuous with the longitudinal grooves 24 so as to extend downwardly of the bottom wall 3. The contact tips 94 and 95 of the fixed contact plates 92 and 93 of each contact unit are vertically aligned with a contact tip 98 of each movable contact spring 91 interposed therebetween, these contact tips defining switching the contact portion of each contact unit. The two sets of contact units thus constructed and received in the switching space 9 are transversely spaced and have their switching contact portions separated from each other by a separator 27 depending from said partition 7 and continuous with the end wall 3, as shown in Fig. 10. Each of the movable contact springs 91 is in the form of elongate blade having a terminal lug 99 at its one end and having on the upper and lower sides of the other end said contact tips 98 which are engageable with the respective one of the contact tips 94 and 95 of the fixed contact plate 92 and 93. Each movable contact spring 91 extends longitudinally within the switching space 9 and is fixed to the casing 1 by inserting the upper end of the terminal lug 99 in a press-fit manner into a vertical slit 26 formed in the open end side of the bottom wall 3 adjacent each of the side walls 4 and 5. As best shown in Fig. 7, the armature 50 of this embodiment is further formed in each of the lateral sides of the horizontally extending section of the card 56 with a furrow 60 into which the side edge of the rear half portion of each movable contact spring 91 is loosely fitted. The furrow 60 is formed at a portion near the free end of the card 56 with a wedge portion 61 at which portion said movable contact spring 91 is clamped to the card 56 for transmitting the force therethrough from the armature 50 to the movable contact spring 91. A V-shaped catch opening 62 is formed at the extremity of each furrow 60 for easily catching the edge portion of the movable contact spring 91 at the time of inserting the horizontal section of the card 56 into the switching space 9 for connection with the movable contact springs 91. In this respect, the movable contact springs 91 act as a horizontal guide for easy insertion of the card 56 into the switching space 9 of the casing 1. It is noted at this point that said pivot pins 35 of the armature 50 can be snapped through the open slit 43 into the bearing holes 42 of the electromagnet 30 at the time of inserting the card 56. Thus, the armature 50 can be easily combined with the electromagnet 30 and the contact assembly 90 simply by inserting it into the casing 1. The coupling between the armature 50 and the contact assembly 90 is such that, when the armature 50 is brought into its stable position of Fig. 6 in response to deenergization of the electromagnet 30, the movable contact spring 91 of each contact unit is kept in contacting engagement with the upper fixed contact plate 92 and out of contacting engagement with the lower fixed contact plate 93. When the armature 50 rotates in a direction indicated by an arrow of the same figure in response to energization of the electromagnet 30, the movable contact spring 91 is urged by the card 56 into contacting engagement with the lower fixed contact plate 93 and out of contacting engagement with the upper fixed contact plate 92. Said armature 50 is further formed on both sides of the mold block 51 with integral skirts 64 which are located below said recess 10 at the open end of the partition 7 and extend toward the side walls 4 and 5 of the casing 1 with its front portion kept in close relation to the end of the partition 7, as shown in Figs. 6 and 9. A pair of flaps 28 are integrally formed with the side walls 4 and 5 at portions just above the rear ends of the movable contact springs 91 but below said recess 10. Each flaps 28 extends inwardly toward the underside of each skirt 64 in such a manner as to be in overlapping relation therewith, thus leaving between the armature 50 and the side walls 4 and 5 only a zig-zag paths which serve to considerably elongate the communication path extending through said recess 10 between the switching space 9 and the coil space 8. As a result, a possible arcing or the like flashover is prevented from running through said recess 10 from the contact assembly 90 to the electromagnet 30 or the electrically conductive portion of the armature 50. The recess 10 is thus substantially closed by the combination skirts 64 and the flaps 28 so that the coil space 8 can be insulatively separated from the switching space also at the open end of the casing 1. The electromagnet 100 shown in Fig. 11 is identical in construction to that of the previous embodiment except that another lower bridge member 44 is added to extend over the free ends of the yoke legs 32 in vertically spaced relation to the upper bridge member 38. The like numerals are employed to designate like parts as in the previous embodiment. The other constructions of the relay are as above. The added lower bridge member 44 is also made of magnetic material serving as a pole member of the same polarity as the upper bridge member 38 and of opposite polarity to the pole end 35 of the core 34. These bridge members 38 and 44 are equally vertically spaced from the pole end 35 interposed therebetween. As shown in Fig. 12, the electromagnet 100 thus constructed is magnetically coupled to the armature 50 of like construction (although only the permanent magnet 54 and the pole plates 52 and 53 thereof are illustrated in the figures) in such a manner that each of the pole plates 52 and 53 extends between the pole end 35 and each of the upper and lower bridge members 38 and 44. With this arrangement, the armature 50, in response to the electromagnet 100 being energized by the voltage of opposite polarity, is driven to rotate into opposite positions at each of which the one of the pole plates 52 and 53 is attracted to the pole end 35 of the core 34 and at the same time the other pole plate is attracted to each of the bridge members 38 and 44. Upon deenergization of the electromagnet 100, the armature 50 is kept at each of the above positions as the magnetic circuit of the permanent magnet 54 is completed through the pole plates 52 and 53, core 34, yoke legs 32 and 33, and through each of the bridge members 38 and 44. Consequently, the armature 50 can have the two stable positions, thereby giving a bistable switching characteristic to the contact assembly (not shown) to be connected to the armature 50 in the same manner as above. Said lower bridge member 44 may be a separate piece to be clamped at its both ends to the free ends of the yoke legs 32 or may be a continuous piece which extends integrally from one of the yoke legs 32 and which is to be bent toward the other yoke leg and is then clamped thereto. LIST OF REFERENCE NUMERALS 1 mount base (casing) 2 shield cover 3 bottom wall 4 side wall 5 side wall 6 end wall 7 partition 8 coil space 9 switching space 10 recess 11 eyelet 12 upstanding section 13 vertical slot 14 port 15 port 16 longitudinal groove 17 longitudinal groove 18 vertical groove 19 vertical groove 20 end slit 22 notch 24 longitudinal groove 25 vertical groove 26 vertical slit 27 separator 28 flap 30 electromagnet 31 yoke 32 leg 33 web 34 core 35 pole end (core) 36 winding 37 coil bobbin 38 bridge member 39 protrusion 40 coil terminal lug 41 support arm 42 bearing hole 43 open slit 44 bridge member 50 armature 51 mold block 52 pole plate 53 pole plate 54 permanent magnet 55 pivot pin 56 card 57 catch slit 60 furrow 61 wedge portion 62 catch opening 64 skirt 70 contact assembly 71 movable contact spring 72 fixed contact plate 73 fixed contact plate 74 contact tip (fixed contact) 75 contact tip (fixed contact) 76 terminal lug (fixed contact) 77 terminal lug (fixed contact) 79 terminal lug (movable contact) 80 contact base 81 contact tip (movable contact) 82 aperture 83 edge 90 contact assembly 91 movable contact spring 92 fixed contact plate 93 fixed contact plate 94 contact tip (fixed contact) 95 contact tip (fixed contact) 96 terminal lug (fixed contact) 97 terminal lug (fixed contact) 98 contact tip (movable contact) 99 terminal lug (movable contact) 100 electromagnet

Claims: An electromagnetic relay comprising a mount base (1) of electrically insulative material having a coil space (8) for receiving an electromagnet (30), a switching space (9) for receiving a contact assembly (90), and an insulating partition (7) separating the coil space (8) from the switching space (9), and an armature (50) magnetically coupled to said electromagnet (30) and operatively connected to a movable contact (91) of said contact assembly (90), characterised in that said partition (7) extends along the entire length of the electromagnet (30) and has at an end edge a recess (10) through which said coil space (8) and switching space (9) communicate with each other, that said armature (50) is formed on its lateral sides with skirts (64) of electrically insulative material extending toward sidewalls (4, 5) of said mount base (1), and that said sidewalls (4, 5) are formed at portions adjacent said recess (10) with inwardly extending flaps (28) each overlapping a respective one of said skirts (64) substantially to close the recess (10) for insulation of said electromagnet (30) from the electrically conductive portions of said contact assembly (90). The relay of claim 1, wherein said armature (50) includes a card (56) of electrically insulative material which passes around the end edge of said partition (7) to extend into said switching space (9) for engagement of said movable contact (91). The relay of claim 1 or 2, wherein said electromagnet (30) comprises a U-shaped yoke (31) having its opposite legs (32) connected by a web (33), a core (34) extending from said web (33) parallel to said legs (32), a winding (36) wound about the core (34), and a bridge member (38) rigidly inter-connecting the ends of said legs (32). The relay of claim 3, wherein said bridge member (38) serves as a pole member of a polarity opposite to that of said core (34) and is spaced from the free end (35) of the core (34) in a direction perpendicular to the plane of said yoke legs (32), and wherein said armature (50) includes a pair of pole plates (52, 53) spaced in a direction perpendicular to the plane of said yoke legs (32) and magnetised to opposite polarities by a permanent magnet (54) interposed therebetween, one of said pole plates (52) extending between the core (34) and the bridge member (38) to provide a stable armature position when said one pole plate (52) is attracted to said bridge member (38) upon deenergisation of the electromagnet (30). The relay of claim 4, wherein the free ends of said yoke legs (32) are inter-connected by a second bridge member (44) serving as a pole member of a polarity opposite to that of the core (34), with the two bridge members (38, 44) being spaced from each other in a direction perpendicular to the plane of said yoke legs (32), with the free end (35) of said core (34) interposed therebetween, and wherein each of said armature pole plates (52, 53) extends between said core (34) and a respective one of said bridge members (38, 44) to provide two stable armature positions in which either pole plate (52, 53) is attracted to the adjacent bridge member (38, 44) upon deenergisation of the electromagnet (100). The relay of any of claims 1 to 5, wherein at least one of said sidewalls (4, 5) is formed with a port (14, 15) through which said movable contact (71, 91) is accessible from the exterior of said mount base (1). The relay of any of claims 1 to 6, wherein said contact assembly (90) includes two sets of contact units each comprising a movable contact (91) and at least one fixed contact (92, 93), and wherein said partition (7) is formed with a separator (27) depending therefrom to divide said switching space (9) into separate compartments each for receiving one of said contact units.

Inventors: MATSUMURA, SUEYOSHI, NOBUTOKI, KAZUHIRO, OKAHASHI, KEIJI, ONO, KENJI, Matsumura, Sueyoshi Matsushita Electric Works Ltd, Nobutoki, Kazuhiro Matsushita Electric Works Ltd, OKAHASHI, KEIJI MATSUSHITA ELECTRIC WORKS LTD, ONO, KENJI MATSUSHITA ELECTRIC WORKS LTD
Applicants: EURO-MATSUSHITA ELECTRIC WORKS AKTIENGESELLSCHAFT
Application year: 1985
Main classification: H01H50
IPC codes: H01H51, H01H50