ELECTROMAGNETIC RELAY

Abstract: An electromagnetic relay includes a base of electrically insulation for mounting an electromagnet, an armature and at least one contact assembly including a movable contact. In­ tegrally molded with the base is an envelop having side walls and a top wall for receiving therein the electromagnet which envelop defines on the base outwardly thereof a space for mounting the contact assembly. The side wall of the envelop extends along the entire length of the electromagnet in order to completely separate the contact assembly located out­ wardly ofthe envelop from the electromagnet along the entire length thereof for increased insulation resistance therebe­ tween. The armature is mounted on the top wall of the en­ velop to be movable within a horizontal plane on the top wall and is operatively connected to the movable contact of the contact assembly by a card extending over the side wall adja­ cent thereto. The electromagnet, contact assembly and arma­ ture are arranged in dense-packed manner on the base while the electromagnet is effectively insulated by the envelop from the contact assembly, whereby assuring higher current car­ rying capacity with a miniaturized construction of the relay.

Description: BACKGROUND OF THE INVENTION 1. Field of the invention The present invention relates to an electromagnetic relay, and more particularly to a low profile miniature electromagnetic relay having a base with an integrally molded envelope for receiving therein an electromagnet and insulatively separating the same from a contact assembly mounted on the base outwardly of the envelope, 2. Description of the prior art Electromagnetic relays, particularly relays requiring a higher 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 partitions 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 only providing an unsatisfactory insulation effect, which prevents designing a miniature relay having a high contact rating in which magnetic and electric components are required to be densely packed at a maximum insulation resistance. FR-A-2 392 484 discloses an electromagnetic relay in which the contact assembly is separated from the relay coil by an insulating partition extending the entire length of the relay. No separation, however, is provided between the contact assembly and the ferromagnetic portions of the armature, which are part of the electromagnetic system. Further, the contact assembly is disposed on top of the relay coil, which results in an increased overall height of the relay. DE-A-2 453 980 discloses an electromagnetic relay with the features included in the first part of claim 1. In that relay, contact systems as well as the legs of a U-shaped armature are disposed on both sides of the relay coil, so that a flat overall relay structure is obtained. Just as in the relay referred to above, direct openings are provided between the contact system and the armature through which a contact actuating card passes. These openings are in the vicinity of one end of the coil. The known structure thus leaves comparatively short leakage paths through which arcing originating from the contacts may take place. SUMMARY OF THE INVENTION It is an object of the present invention to provide a miniature relay with reduced height and length dimensions in which a satisfactory insulation between the electromagnet and the contact assembly is ensured. This object is met by the invention defined in claim 1. In the electromagnetic relay of the invention, the overall electromagnet is enclosed by an envelope integrally formed with the mount base of the relay and the fact that the contact actuating card extends over the sidewall of the envelope at a position lengthwise offset from a window through which pole means connected to the armature extends into the interior of the envelope provides a large and efficient separation of the contact system from the electromagnet without affecting the length or height of the overall relay. Preferred embodiments of the invention will now be described with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of an electromagnetic relay in accordance with a first embodiment of the present invention; Fig. 2 is an exploded perspective view of the above relay; Fig. 3 is an exploded perspective view of the above relay with its contact assemblies removed; Fig. 4 is a cross section of the above relay with a cover attached, taken along a corresponding line 4-4 of Fig. 1; Fig. 5 is an exploded perspective view of a relay base, coil bobbin and a yoke constructing the above relay; Fig. 6 is an exploded perspective view of the relay base and an additional coil terminal to be embeded therein; Fig. 7 is a schematic illustration of the magnetic coupling between an electromagnet and an armature of the above relay; Fig. 8 is a schematic illustration of the connection between a movable spring and a card of the armature employed in the above relay; Fig. 9 is a horizontal section, in somewhat schematic representation of a relay in accordance with a modification of the above relay; Fig. 10 is a perspective view of a yoke employed for the relay of Fig. 9; Fig. 11 is a perspective view of an electromagnetic relay in accordance with a second embodiment of the present invention; and Fig. 12 is partial view, in perspective representation, of the relay of Fig. 11. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to Figs. 1 to 8, there is shown an electromagnetic relay in accordance with a first embodiment of the present invention. The relay comprises a base 1 for mounting an electromagnet 30, a pair of contact assemblies 50, and an armature 60. The base 1 is made of electrically insulative plastic material to include an integrally molded envelope 10 extending along the substantial length of the base 1 and leaving on both sides thereof spaces for mounting the contact assemblies 50. The envelope 10 has a bottom wall common to the base 1 and is defined by a pair of parallel side walls 11, a rear end wall 12 and a top wall 13. The envelope 10 is open at its front end to define thereat a mouth 14 through which the electromagnet 30 is assembled into the envelope 10. Integrally extending laterally from the front edge of each side wall is an insulation lip 15 which terminates at the side extremity of the base 1 to close the front end of said space for mounting the contact assembly 50. A rim 16 extends integrally along the front edges of the top wall 13 and the insulation lips 15 to define on the front of the envelope 10 or insulation dips 15 a recess 17. A cover 5 of like insulative material fits on the base 1 to enclose therebetween the contact assemblies 50 and the armature 60. In the present embodiment, the electromagnet 30 is of a two-coil type having a set coil and a reset coil, each passing a current of the opposite direction for reversing the switching operation of the contact assemblies 50. As best shown in Fig. 2, the electromagnet 30 comprises a coil bobbin 31 around which the set and reset coils 32 are wound, a U-shaped yoke 33 with parallel legs 34 joined by a web 35, and a core 36 which extends through coil bobbin 31 and is connected at its end to the web 35. The core 36 extends in parallel relation with the yoke legs 34 so that a gap is defined between the other end thereof and the free end of each yoke leg 34. The coil bobbin 31 is molded of an electrically insulative plastic material to have at its front end a laterally extending flange 38 through which the yoke legs 34 extend rearward with the web 35 being held therein. The flange 38 is dimensioned so as to be snugly fitted within said recess 17 at the front end of the envelope 10 and carries two coil terminals 40 respectively at the lateral end portions. Each of the coil terminals 40 embeded in the flange 38 has its upper end connected to the one end of each of the set and reset coils 32 and has its lower end or lug portion extending downwardly through a notch 2 in the front edge of the base 1 for connection with external control circuits. A separate coil terminal 41 is supported by one of said insulation lips 15 to have its upper end 42 connected to the common end of the set and reset coils. As best shown in Fig. 6, the coil terminal 41 is fixed in position with its middle portion including a rearward tab 43 being inserted into an indent 18 formed in the front surface of said insulation lip 15. The lower end or lug portion of the coil terminal 41 extends downwardly through a slit 3 continuous with said notch 2 of the base 1 for connection with the external control circuits. The indent 18 is only opened at its front end for insertion of the coil terminal 41 and does not constitute any communication path with the space behind the insulation lip 15 so that the coil terminal 41 is completely separated from the contact assembly 50 mounted rearwardly of the insulation lip 15 in the same fashion as the coil terminals 40 on the flange 38 of the coil bobbin 31 are insulated therefrom by the insulation lips 15. Each of the contact assemblies 50 comprises a movable contact 51 in the form of an elongate leaf spring and a fixed contact 55. The movable contact or spring 51 extends alongside of the envelope 10 with its one end supported by a terminal plate 53 fixed on the base 1 just behind the insulation lip 15, and has on the other end a contact tip 52 engageable with a contact tip 56 on the fixed contact 55 at the rear end of the base 1. The terminal plate 53 and the fixed contact 55 are provided respectively with lugs 54 and 57 which extends downwardly through the base 1 to form respective contact terminals. The relay of the present embodiment is of polarized type incorporating a permanent magnet 62 in the armature 60. The armature 60 comprises a flat-shaped swing plate 61 of an electrically insulative plastic material provided on the underside of its rear end with a pair of pole pieces 63 magnetized to have opposite polarities by the permanent magnet 62 which is interposed between the adjacent ends of the pole pieces 63. The permanent magnet 62 and the pole pieces 63 are embeded in a depending frame 64 at the rear end of the swing plate 61 in such a way that the major portions of the pole pieces 63 project on the underside of the swing plate 61. Formed at the rear end of the top wall 13 of said envelope 10 is a window 19 through which the pole means thus constructed extends into the envelope 10 where it is magnetically coupled to the pole end of the electromagnet 30. That is, as schematically shown in Fig. 7, each of the pole pieces 63 extends into a gap defined between the free end of the core 36 and each of the yoke legs 34 so as to be movable within the gap upon energization of the set and reset coils 32. Turning back to Figs. 1 through 3, the swing plate 61 of the armature 60 has in its front end a bearing hole 65 which receives a pivot pin 20 on the front end of the top wall 13 so that the armature 60 is pivotally supported on the top wall 13 and pivots about the pivot pin 20 within a horizontal plane on the top wall 13 of the envelope upon energization of the coils. Integrally formed on either side of the swing plate 61 is a card 66 which extends over the adjacent side wall 11 of the envelope 10 so as to catch the movable contact 51 of each contact assembly 50 for actuation thereof upon the pivotal movement of the armature 60. Each of the cards 66 is of a generally L-shaped as viewed in a horizontal plane composed of a first leg 67 in perpendicular relation to the length of the armature 60 and a second leg 68 in parallel relation thereto. Formed on the underside of the second leg 68 is an integral skirt 69 which depends along the inner edge thereof in spaced relation with a complementary flap 70 depending from the outer edge of the free end portion of the second leg 68 so as to define therebetween a slot 71, as best shown in Fig. 8. It is this slot 71 that catches an intermediate portion of the movable spring 51 for actuation thereof by the pivotal movement of the armature 60. In operation, when the electromagnet 30 is energized by flowing a current of given polarity through the set coil, the armature 60 is driven to pivot in one direction at which occurrence one of the card 66 actuates the corresponding movable contact or spring 51 against the bias thereof into contacting engagement with the fixed contact 55 for closing the contacts of the contact assembly 50 on one side of the base 1 and simultaneously the other card 66 actuates the corresponding movable spring 51 against the bias thereof out of contacting engagement from the fixed contact 55 for contact breaking of the contact assembly 50 on the opposite side of the base 1. In this sense, the former contact assembly 50 constitutes a normally-open contact while the latter constitutes a normally-closed contact which is opened in so-called lift-off fashion by the card 66 of the armature 60. When the electromagnet 30 is magnetized to the opposite polarity by the current flowing through the reset coil, the armature 60 is driven to pivot in the opposite direction, thus reversing the switching operation of the contact assemblies 50. The rear end portion of the envelope 10 is formed with an upward extension 21 along the upper edges of the rear end wall 12 and the side wall 11, which extension 21 cooperates with similar upward extensions 22 on the insulation lips 15 at the front end of the envelope 10 to define support walls the upper ends of which terminate in a horizontal plane above said armature 60 and serve to support the ceiling of the cover 5, leaving between the top wall 13 of the envelope 10 and the ceiling of the cover 5 a header space 6 within which said armature 60 can move free from collision with the cover 5, as best shown in Fig. 4. Formed interior of the cover 5 are a pair of partitions 7 each extending from the rear face thereof in spaced relation with the side face and joining by a bent portion 8 (Fig. 3) with the side face just behind the front face. In the assembled state of the cover 5 onto the base 1, each partition 7 extends between the contact assembly 50 and the adjacent side wall 11 of the envelope 10 and overlaps the side wall 11 so as to further improve the electrical insulation of the contact assembly 50 from the electromagnet 30 as well as from the pole means of the armature 60 exposed in the window 19 at the rear end of the top wall 12 of the envelope 10. That is, the partition 7 can serve to substantially close the window 19, which is inevitable for magnetic coupling between the armature 60 and the electromagnet 30, in such a way as to effectively insulate the electrically conductive parts of the electromagnet 30 and the armature 60 from the contact assemblies 50. The partition 7 is formed in its intermediate portion of its length with an aperture 9 which allows the first leg 67 of the card 66 to extend therethrough for coupling with the movable contact 51. It is noted at this time that said skirt 69 depending from the second leg 68 of the card 66 is in overlapping relation with the aperture 9 so as to substantially close the same. The above structure, in addition to the arrangement that the aperture 9 is offset lengthwise from the window 19, can certainly reduce to a maximum extent the formation of communication path from the contact assembly 50 to the electrically conductive parts of the electromagnet 30 and the armature 60 through the window 19. Said bent portion 8 of each partition 7 overlaps the corresponding insulation lip 15 just behind the same so as to ensure the separation between the contact assembly 50 and the coil terminals 40 and 41 received in the recess 17 at the front end of the envelope 10. Referring to Figs. 5 and 6, the envelope 10 is formed in the inner surface of each side wall 11 with a furrow 24 into which each of the yoke legs 34 of the electromagnet 30 is slid at the assembling of the relay. The height of the furrow 24 is dimensioned to equal that of each yoke leg 34 so that the yoke legs 34 are snugly fitted on the inner surface of the side walls 11 to be fixed in position. The inner distance D between the opposed side walls 11, or the furrows 24 is dimensioned to be exactly equal to the outer distance between the opposed yoke legs 34 in order that the yoke legs 34 are kept in intimately contacting engagement with the inner surfaces of the side walls 11, or the bottoms of the furrows 24. This is a safe measure against possible deformation of the yoke legs 34 due to the force which may be applied thereto each time the pole piece 63 of the armature 60 strikes the yoke leg 34 during the pivotal movement of the armature 60. Otherwise, the yoke legs 34 would be caused to spread outwardly by the repetitive application of such force over a longer period of the relay operation. This is also effective for stably maintaining the gap distance between the core 36 and each of the yoke legs 34, thus effecting the accuracy with which the armature 60 can pivot for actuating the switching operation of the contact assemblies 50 and therefore increasing a response sensitivity. For the same purpose, a rear flange 39 which is provided at the rear end of the coil bobbin 31 to support the free ends of the yoke legs 34 on both side thereof has exactly the same width as the inner distance between the opposed yoke legs 34. Although the present embodiment only illustrates the electromagnet 30 with the set and reset coils, an electromagnet 30 with a single coil may be of course employed. As shown in Fig. 8, the one of the cards 66 coupled with the movable spring 51 forming the normally-closed contact arrangement is configured to have a flat portion 72 on one of the opposed faces of the slot 71 receiving the movable spring 51, which flat portion 72 is in face-to-face contacting engagement with the portion of the length of the movable spring 51, while the other face is in a point contacting relation with the movable spring 51 with respect to the length thereof. Said flat portion 72 terminates at a rear edge of the card 66 and provides a face-to-face contact between the rear end of the card 66 and the movable spring 51, such that when the armature 60 actuates the movable spring 51 in the direction (indicated by an arrow X) of disengaging it from the fixed contact 55 against the bias of the spring in the so-called lift-off manner, the movable spring 51 can effectively and rapidly cease its vibration associated with the abrupt movement of the movable spring 51 from the stable position of closing the contacts, thus preventing the bouncing of the contacts and ensuring rapid interruption of possible arc developed between the contacts. Also, the above description is only directed to the relay of bistable operation in which the yoke legs 34 establish with the adjacent ones of the pole pieces 63 the magnetic paths of the same magnetic resistance so that the armature 60 is stable at either of its positions as one of the pole pieces 63 is kept attracted to the corresponding yoke leg 34 by the action of the permanent magnet 62, it is equally possible to provide a relay of monostable operation by differentiating the magnetic resistance of the magnetic paths between the yoke legs 34 and the corresponding pole pieces 63 of the armature 60. Referring to Figs. 9 and 10, there is shown a modification of the first embodiment which is identical in construction thereto except for the detailed configurations of the yoke legs 34 and the corresponding side walls 11 of the envelop 10. The inner width between the opposed side walls 11 of the envelop 10 is wider at the front end than at the rear end for facilitating the molding of the envelop 10 as well as insertion of the electromagnet 30 into the envelop 10. The width at the rear end of the envelop 10 is dimensioned so that the rear end portion of each yoke leg 34 is in intimate engagement with the side wall 11 for providing an accurate positioning of the yoke legs with respect to the armature 60 to assure accurate movement of the armature 60 in much the same way as in the previous embodiment. The yoke 33 is formed to have on the front end portion of each leg 34 a protrusion 37 which is struck outwardly therefrom for engagement with the front widened portion of the side wall 11 for stably fixing the electromagnet 30 within the envelope 10. Referring to Figs. 11 and 12, there is shown a relay in accordance with a second preferred embodiment of the present invention which is similar in construction to the above first embodiment except that it includes only a single contact assembly 80 on one side of a relay base 1 including an envelope 10 of substantially the same configuration as in the first embodiment. Like numerals designate like parts. Mounted on the top wall 13 of the envelope 10 is an armature 90 which comprises a flat swing plate 91 of electrically insulative plastic material carrying on the underside of its rear end pole pieces 63 and a permanent magnet 62 interposed therebetween. The armature 90 is magnetically coupled with the electromagnet 30 received within the envelope 10 by the pole means extending into the envelope 10 so that it is movable upon energization of the electromagnet 30 within a horizontal plane on the top wall 13 about a pivot pin 20 projected on the front end of the top wall to extend into a complementary bearing hole 65 in the front end portion of the swing plate 91. Projecting from the lateral side of the armature 90 is a card 66 of similar construction as above, having a first leg 67, second leg 68, skirt 69, flap 70, and a slot 71 for engagement with the movable spring 81 of the contact assembly 80. The pivot axis of the armature 90 or the pivot pin 20 is arranged on an extension of the length of the movable spring 81 extending alongside the envelope 10 so that the pivot axis is in alignment with the connection between the card 66 and the movable spring 81 along the length of the movable spring 81, whereby the pivotal movement of the armature 90 causes little or substantially no friction of the card 66 along the length of the movable spring 81, in contrast to a case in which the pivot axis of the armature were offset laterally from the extension of the movable spring 81. With this structure, the relay of the present embodiment can have an increase response sensitivity. In operation, the armature 90 is urged in one direction by the bias of the movable spring 81 and is pivoted in the other direction upon energization of the electromagnet 30 to drive the movable spring 81 into contact with a fixed contact 85 against the bias of the movable spring 81. It is to be noted at this time that a cover (although not shown in the figures) of similar construction as in the first embodiment is adapted to fit over the relay base 1 so that the relay of the second embodiment also provides an increased insulation effect between the electromagnet 30 and the contact assembly 80 in much the same way as in the first embodiment. In the present embodiment, there is only disclosed the contact assembly 80 of normally-open switching arrangement; however, it is of course possible to include a contact assembly of normally-closed switching configuration instead. In this event, the card could be connected with the movable spring in a similar manner as described with reference to Fig. 8.

Claims: An electromagnetic relay comprising a mount base (1⊘) of electrically insulating material provided with integrally molded side walls (11), a contact assembly (50; 80) mounted on the base (1⊘) outwardly of one of said side walls (11) and including a movable contact (51; 81) extending along said one side wall (11), an electromagnet (30) electrically insulated along its entire length from the contact assembly (50; 80) by said side wall (11), a flat actuator (60; 90) generally extending within a plane parallel to the plane of the base (1⊘) and being magnetically coupled with a pole end at the rear end of the electromagnet (30), a card (66) of electrically insulating material for transmitting the movement of the actuator (60; 90) to the movable contact (51; 81), and a cover (5) cooperating with the base (1⊘) to enclose said electromagnetic relay, characterized in that a top wall (13) is integrally formed with said base side walls (11) to form an envelope (10) around the electromagnet (30), that the actuator (60; 90) is made of electrically insulating material and mounted on the top wall (13) of said envelope (10) for pivotal movement within its plane, and bears at its rear end pole pieces (62, 63) extending through a window (19) in the rear portion of said top wall (13) for cooperation with said pole end of the electromagnet (30), that the base (1) has support walls (21) extending above the actuator (60; 90) into supporting contact with the ceiling of the cover (5) to leave a moving space (6) for the actuator (60; 90) between the top wall (13) of the envelope and said cover ceiling, and that said cover (5) has a vertical partition wall (7) overlapping the side wall (11) of the envelope (10) for laterally closing said moving space (6) except in regions (9) where said card (66) extends over the side wall (11) of the envelope (10) into engagement with the movable contact (51; 81), said regions (9) being offset lengthwise from the window (19). The relay of claim 1, wherein the coil bobbin (31) of the electromagnet (30) is formed at its front and with a flange (38) carrying coil terminals (40), and wherein said envelope (10) is formed with an insulation lip (15) extending sidewards and forwardly from the front end of said side wall (11), said envelope (10) forming in front of the insulation lip (15) a recess (17) for receiving the flange (38) of the bobbin (31). The relay of claim 2, wherein said electromagnet (30) includes a set coil and a reset coil (32) and a further terminal (41) common to the set and reset coils (32), said insulation lip (15) of the envelope (10) being provided in its front surface with an indent (18) for receiving said further terminal (41) separated from the contact assembly (50; 80), which contact assembly is disposed behind the insulation lip (15). The relay of any of claims 1 to 3, wherein said electromagnet (30) includes a U-shaped yoke (33) with parallel legs (34) defining a gap within which said pole pieces (62, 63) of the actuator (60; 90) move, the outer face of each yoke leg (34) being in intimate contact with the inner surface of the adjacent side wall (11) of the envelope (10). The relay of any of claims 1 to 4, wherein a pair of contact assemblies (50) are mounted on the base (1) one on either side of the said envelope (10), and said actuator (60) has a pair of contact actuating cards (66) each engaging the movable contact (51) of the respective contact assembly (50). The relay of any of claims 1 to 4, wherein a single contact assembly (80) having a movable contact in the form of an elongate spring (81) is mounted on the base (1), and the pivot axis of the actuator (90) is located on a lengthwise extension of the contact spring (81).

Inventors: MOTOYAMA, MASANORI, NAKAGAWA, MASASHI, NISHIKAWA, TOYOTAKA
Applicants: EURO-MATSUSHITA ELECTRIC WORKS AKTIENGESELLSCHAFT
Application year: 1986
Main classification: H01H51
IPC codes: H01H51, H01H50