US3911383A

US3911383A - Electromagnetic relay

Info

Publication number: US3911383A
Application number: US446601A
Authority: US
Inventors: Hitoshi Tabei; Munetada Kazama
Original assignee: Oki Electric Industry Co Ltd
Current assignee: Oki Electric Industry Co Ltd
Priority date: 1973-05-14
Filing date: 1974-02-28
Publication date: 1975-10-07
Anticipated expiration: 1992-10-07
Also published as: JPS505133U

Abstract

This invention relates to a small-sized electromagnetic relay having a contact assembly which is easy to assemble and operates with high stability.

Description

[4 1 Oct. 7, 1975 References Cited UNITED STATES PATENTS ELECTROMAGNETIC RELAY [75] Inventors: Hitoshi Tabei; Munetada Kazama,

Breitenstein........................

, Japan both of Tokyo 3,026,389 3/1962 Cheronnet 3,106,625 10/1963 [73] Assignee: Oki Electric Industry (10., Ltd., Tokyo, Japan Mar1ey.......,.....

8/1970 Harnada et a1.. 174/52 S 11/1971 Boisvert........i.. 174/52 S [22] Filed: Feb. 28, 1974 [21] Appl. No.: 446,601

3,634,793 1/1972 Sauer......,.,......... 335/78 4/1974 Hammell et a1.

[30] Foreign Application Priority Data Primary Harris May 14, 1973 Attorney, Agent, or FirmPeter L. Berger [57] ABSTRACT This invention relates to a small-sized electromagnetic relay having a contact assembly which is easy to assemble and operates with high stability.

[52] US. Cl. 335/106; 200/283; 335/128;

0 15 3m oo 1 lu 56 0 3 9O 3H22 1 1 5 H "n I 4 "77 n .1 a 8 "u? m 1 i In .5 ""3 m m r "a e 8 ma d t u .mfi Nod 55 9 Claims, 21 Drawing Figures US. Patent Oct. 7,1975 Sheet 1of7 3,911,383

FIG. 2 B PRIOR ART FIG 1 PRIOR ART PRIOR ART Sheet 2 of 7 US. Patent OCL 7,1975

US. Patent 0a 7,1975 Sheet 3 of7 3,911,383

FIG. 5

Sheet 4 0f 7 US. Patent Oct. 7,1975

FIG. 6-A

US. Patent 0a. 7,1975 Sheet 5 of7 3,911,383

FIGS-F US. Patent Oct. 7,1975 Sheet 6 of7 3,911,383

US. Pawn? Oct. 7,1975 Sheet 7 of7 3,911,383

FIGJO ELECTROMAGNETIC RELAY BACKGROUND OF THE INVENTION In FIG. 1 there is shown, in perspective, a typical example of the prior art miniature electromagnetic relays. In the figure, numeral 1 denotes a header, 2 a contact assembly, 3 an electromagnetic assembly, 4 a return spring, and 5 a back stopper. FIG. 2A is a perspective view of the header 1 and contact assembly 2. The header 1 consists of a sole plate 1a and a series of contact pieces lb 1i which are hermetically sealed to said sole plate 1a. The contact assembly comprises

stationary contact springs

2a, 2b, 2c, 2d, and

movable contact springs

2e, 2f. All of these contact springs 2a 2f are welded to the respective contact pieces 1b,

Id

1f, 1h, 1i which project beyond the surface of said sole plate 1a. The sole plate la is also formed with a recess lj. The

stationary contact springs

2a, 2a and movable contact spring 2e constitute, in combination, a switch contact assembly, and the

stationary contact springs

2b, 2c and movable contact spring 2f constitute another switch contact assembly. FIG. 2B show, in perspective, a part of the electromagnetic assembly 3 including a return spring 4 and a back stopper 5. The electromagnetic assembly 3 comprises a-pair of

coils

3a, 3b, a yoke 3c, a pair of

bobbins

3d, 3e, an armature 3f, a shaft 3g, and a pair of

cores

3h, 3i. The armature 3f is secured to the shaft 3g which, in turn, is rotatably supported by the yoke 30. Secured to both ends of said armature 3f are driving

bars

3j, 3k which carry at their

ends insulating balls

31, 3m, respectively. These

insulating balls

31, 3m are so arranged as to actuate the

movable contact springs

2e, 2f, respectively. The ends of the

coils

3a, 3b are connected to the terminals 10, 1 g, respectively. The return spring 4 is coiled around the shaft 3g. The stopper 5 is secured to the yoke 3c and disposed between the contact assembly 2 and the electromagnetic assembly 3 so as to define the scope of actuation of said

driving bars

3j, 3k secured to the armature 3f. The yoke 3c is securely fixed in the recess 1 j of the sole plate la.

Having the above-described arrangement, this prior art miniature electromagnetic relay operates as follows.

When the electromagnetic assembly 3 is nonexcited, the armature 3f is set at its initial position under the pressing force of return spring 4. In the contact assembly 2, the movable contact spring 22 is in contact with the stationary contact spring 2a under a predetermined pressing force produced by the bending of the spring, while the movable contact spring 2f is also similarly in contact with the stationary contact spring 2e. When the

coils

3a, 3b, are energized, the armature 3f is attracted to the

cores

3h, 3i, so that the

insulating balls

31, 3m depending from both ends of said armature 3f move the

movable contact springs

2e, 2f to cause them to be pressed against the respective

stationary contact springs

2d, 2b, thereby effecting contact switchover.

However, in assembling such a miniature electromagnetic relay, the terminals lb 1i must be inserted and hermetically sealed one by one, and also the stationary contact springs 2a 2d and movable contact springs 22, 2f must be secured one by one to the corresponding terminal pieces lb, 1e, If, 11', Id, lg. Therefore, the assembly work is very inefficient and a number of parts as well as many steps are required for adjustment. Also, when it is desired to form a multiple switchover contact system by using such contact assemblies, the size of the relay unit becomes large and can hardly be formed as a miniature size. Further, for effecting loaded actuation of the movable contact springs in such a contact assembly, there is employed a so-called flexure type where any actuating force is supplied from the outside, so that the contact opening and closing operations of the unit are low in reliability.

OBJECTS OF THE INVENTION An object of the present invention is to realize a reduction of the number of parts, the number of assembling steps and the number of adjusting steps required in assembling the unit, by directly combining a movable contact spring assembly to which the movable contact pieces are welded and a terminal assembly to which said movable contact spring assembly and stationary contact pieces are welded.

Another object of the present invention is to allow easy construction of a contact assembly having a plurality of switchover contacts by using the above-said arrangement and also to allow employment of a highly reliable liftoff type mechanism for loaded actuation of the movable contact springs.

Still another object of the present invention is to obtain a relay unit with a flat construction.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view showing an example of the prior art miniature electromagnetic relays;

FIGS. 2A and 2B are perspective views of the principal parts of the electromagnetic relay shown in FIG. 1;

FIG. 3 is a top plan view of an electromagnetic relay according to an embodiment of the present invention;

FIG. 4 is a side elevation of the electromagnetic relay of this invention thereof;

FIG. 5 is an exploded view of the invention illustrating the method of assemblage;

FIGS. 6A to 6.] are assembly drawings of the header and contact assembly in the electromagnetic relay shown in FIGS. 3 to 5;

FIGS. 7A and 7B are top plan views showing operation of the contact assembly; and

FIGS. 8 to 10 are perspective views of an electromagnetic relay according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, FIG. 3 is a top plan view of a miniature electromagnetic relay embodying the present invention, and FIGS. 4 and 5 are a side elevation and an assembly drawing thereof respectively. In these figures, numeral 106 designates a header, 107 a contact assembly, 108 a card member, 109 an electromagnetic assembly, l10 a return spring, 111 a support member, and 112 a cover. These elements are assembled into a unit by first fixing the contact assembly 107 in position on the header 106 and then joining the card member 108, electromagnetic assembly 109, return spring 110, support member 111 and cover 1 12 in that order.

The header 106 and contact assembly 107 are built up in the process shown in FIG. 6. That is, firstly, a metal sheet 106a is punched as shown in FIG. 6A and then bent in an L shape so as to form first arms l06b and second arms 206C as shown in FIG. 68. Then a metal frame 106d such as shown in FIG. 6c is mounted on and fixed by a glass sheet 106e to said L-shaped metal sheet 106a as shown in FIG. 6D. The first arms 106b of the L-shaped metal sheet 106a are exposed on one side of the glass sheet 1062 while the second arms 106C protrude'beyond the other side of said glass sheet.

Then, the unnecessary portion of the metal sheet 106a is cut off, thereby obtaining a header 106 provided with two rows of L-shaped terminals 113a 113n. In the actual manufacturing process, cutting-off of the unnecessary portion is practiced after fixing the contact assembly 107 in position. The metal sheet 106a is also formed with guide holes 106f, 106g, and the metal frame 106d is provided with recesses or cut-out portions 106/1 106k.

The contact assembly 107 is built up in the following way. The stationary contact pieces 107a 107d are connected vertically to the first arms 106b of the

respective terminals

113b, 1136, 11312, 113k.

Next, two metal sheets 107s and 106f, which have been punched as shown in FIGS. 6F and 6G, are subjected to L-shape bending work to form raised-up strip protions 107g and their base portions 10711 as shown in FIGS. 6H and 61. (Each strip portion with its base portion describes an L shape). The strip portions 107g serve as movable contact springs 114a 114d, ll4e 114/1. Secured to one side of each of said movable contact springs 114a 114h is a corresponding one of the movable contact pieces 115a 11511. Mounting of the metal sheet 107e to the header 106 is accomplished by first positioning them relative to each other by registering the guide holes 106f, 106g, at both ends of the metal sheet 106a with the corresponding guide holes 10711, 10712 formed at both ends of the metal sheet 107e, then welding the first arm portions 10619 of the

corresponding terminals

113d, 113g, ll3j, 113m exposed on the surface of the header 106 to the base por- 4 tions 10711 of the associated movable contact springs 114a 114d, and then cutting off the unnecessary portion of the metal sheet 107e. Fixing of the metal sheet 107f to the header 106 can also be accomplished similarly by first positioning them relative to each other by registering the guide holes 106f, 106g with corresponding holes 107i, l07j, then welding the base portions 10711 of the associated movable contact springs 114e 11411 to the first arm portions l06b of the corresponding terminals 113C, 1 13f, 1 13a, 1131, and then cutting off the unnecessary portion of the metal sheet 107f. After uniting the header 106 and contact assembly 107 in the above-said manner, the unnecessary portion of the metal sheet 106a is cut off, thereby obtaining a combined structure of header 106 and contact assembly 107 as shown in FIG. 6]. The movable contact springs 114a 114/1 contact the corresponding stationary contact pieces 107a 107d by the action of their elastic pressure.

The electromagnetic assembly 109 consists of a bobbin l09a, a coil 109b, a core 109e, a yoke 109d and an armature 109e. The coil l09b is wound around the bobbin 109a, and the core 1096 is inserted in said bobbin 109a, with one end of said core being secured to the L- shaped yoke 109d. Both ends of the coil l09b are connected to the

terminals

113a and 113n, respectively. On the top surface of said yoke 109d are provided a pair of

protuberances

109f, 109g adapted to define the positions of the return spring 110 and support member 111 when they are assembled together.

An end 109/1 of the armature l09e is worked circularly so that it is rotatably supported by the support member 111. The other end of said armature is formed with recesses 109i, 109j and disposed in opposition to the core 109C. The return spring is L-shaped and formed with guide holes 110a, 1 10b which fit with the protuberances 109F, 1093, respectively, provided on the yoke 109d. In one end of said return spring 110 are formed recesses 1100, 110d for supporting the card plate 108. Said card plate 108 is provided with protuberances 108a 108d (1086 and 108d being not shown) disposed corresponding to the stationary contact pieces 107a 107d and greater in width than said contact pieces 107a 107d. Also provided at one end of said card plate are

protuberances

108e, 108f that fit in the recesses 109i, l09j, respectively, formed in the armature 109e, and at the other end of said card plate are provided protuberances 108g, 10811 that fit in the recesses 1 100, 1 10d, respectively, formed in the return spring 1 10. The card plate 108 is supported by said armature l09e and return spring 110 so as to lie parallel to the contact assembly 107.

The support member 1 11 is made from a metal sheet which has been punched and bent into a desired shape. In the top face of said support member are formed guide holes 111a, lllb which fit with the

protuberances

109f, 109g, respectively, on the yoke 109d. In assemblage, said support member is secured by said

protuberances

109f, 109g together with the return spring 110 as for instance by calking. At both ends of said support member 111 are provided

legs

111e, 111a and 111e, l 1 1f which fit securely in the respective recesses 106h 106k formed in the metal frame 106d of the header 106. At an upper end of said support member 111 are also provided recessed

portions

111g, 111/1 (111/1 being not shown) adapted for rotatably retaining an end 109]: of the armature 109e, and below said recessed portions 111g, 1 l lh are provided back stoppers 111i, lllj (111j being not shown) for the armature 109e.

In this way, the contact assembly 107 is unitarily combined with the header 106 and then the card plate 108, electromagnetic assembly 109 and return spring 110 are assembled together so as to be supported by the support member 111, and thereafter the cover 112 is airtig'htly mounted over the metal frame 106d which constitutes the header 106.

The miniature electromagnetic relay according to the present invention which has the above-described arrangement operates as follows.

Referring to FIGS. 7A and-7B, there are shown top plan views of the contact assembly 107 for illustrating the operation of the present device. FIG. 7A shows the condition of the contact assembly 107 where the electromagnetic assembly 108 is inoperative, and FIG. 7B shows the situation where the electromagnetic assembly 108 is operative.

In FIGS. 7A and 7B, the protuberances 108a 108d provided on the card plate 108 are disposed adjacent the stationary contact pieces 107a 107d to actuate the movable contact springs 114a 114h to perform touching and separating operations relative to the stationary contact pieces 107a 107d.

Now, let it be supposed that the electromagnetic assembly 109 is in an initial inoperative condition; then the card member 108 will be moved to the position of the

back stoppers

111i, 1 1 l j by the return spring 110, and the protuberances 108a 108d will actuate the

movable contact springs

114a, 1 14b, 1 14g, 1 14/1 to let them separate from the respective

stationary contact pieces

107d, 1070, 107b, lO7a, while making contact between stationary contact piece 107a and movable contact spring 114d, between stationary contact piece 107b and movable contact spring 1140, between stationary contact piece 1070 and movable contact spring 114f, and between stationary contact piece 107d and movable contact spring 114e, under elastic pressure of

movable contact spring

114d, 1 14c, l 14f, l 142, respectively, as shown in FIG. 7A.

Let it now be assumed that power is connected to the coil 10912 of the electromagnetic assembly 109 to energize the latter. Then the armature 109e supported rotatably by the support member 1 1 1 will be attracted by the core 109C and the card member 108 fitted in the recesses 109i, 109j in the armature 1092 and recesses 1100, 1 [Odin the return spring 110 will be actuated by attraction of the electromagnetic assembly 109 to move parallel to the contact assembly 107 against the restorative force of the return spring 110, thus separating the movable contact springs 114d, 1 14c, l 14f, l 142 away from the respective

stationary contact pieces

107a, 107b, 1070, 107a, while making contact between stationary contact piece 107a and movable contact spring 1l4h, between stationary contact piece 10717 and movable contact spring 114g, between stationary contact piece 107C and movable contact spring 1141;, and between stationary contact piece 107d and movable contact spring 114a, under elastic pressure of the movable contact springs 114h, 114g, 114b, 114a, respectively, as shown in FIG. 7B. When power is disconnected from the coil 109b, the card member 108 is again forced back to its original position by the action of return spring 1 10, bringing the contact assembly 107 back into the condition of FIG. 7A. Thus, as apparent from FIGS. 7A and 7B, four switchover contact assemblies centered by the stationary contact pieces 107a 107d, respectively, are formed in the miniature electromagnetic relay of the present invention.

FIGS. 8 shows, in perspective, a miniature electromagnetic relay with a more flat construction according to another embodiment of the present invention. In FIG. 8, reference numeral 106 indicates a header and 107 a contact assembly built up on said header 106. This header 106 and contact assembly 107 are the same as that shown in FIG. 6. Another contact assembly 107 is not shown to avoid redundancy. Numeral 116 denotes a supporting base plate on which said header 106, return springs 117, an electromagnetic assembly 118 and card member 119 are mounted. The return springs 117a, 1 17b, have their one end secured to both ends of the header 106, and recesses 117C, 1 17d are formed toward the other ends of said springs. The electromagnetic assembly 118 comprises a bobbin 118a, a coil 118b, a core 1180, a yoke 118d, an armature 118e, and a stopper 118f. The core 1186 is secured at its one end to the yoke 118d. The yoke 118d is L- shaped, with one side thereof being secured to the core 118C and the other side to the base plate 116. The armature 118e is opposed to the other end of the core 118C, with one end of said armature being rotatably supported on said base plate 116 and a protuberance 118g is provided at the other end of said armature. The back stopper l18f is secured to the yoke 118d to define the movable range of the armature 118e. The card member 119 is disposed on the contact assembly 107 so as to extend parallel to the header 106 and fits securely in the recesses 1170, 117d in the return springs 117a, ll7b. Toward one end of the card member 119 is formed an opening 119a through which a protuberance 118g of the armature 118e is inserted. Said card member 119 is also provided with protuberances 119b 119e (119d and 11% being not shown) corresponding to the stationary contact pieces 107a 107d of the contact assembly 107.

According to this arrangement, when the electromagnetic assembly 1 18 is inoperative, the card member 119 is moved to the position where the armature l18e is held back by the back stopper 1l8f, and when the electromagnetic assembly 118 is energized, the armature 118e now is attracted by the core 1180 to move against the restorative force of the return springs 117a, 1 17d. Making and breaking of contact assembly 107 is effected in accordance with said movement of the card member 119. Thus, in this embodiment, as the electromagnetic assembly 118 is disposed substantially flush with the header 106, the height of the unit is appreciably reduced to provide a flat miniature electromagnetic relay.

FIG. 9 is a perspective view of a miniature electromagnetic relay with a flat construction according to still another embodiment of the present invention. In FIG. 9, numeral 106 designates header, 107 contact assembly (not shown), 116 support base, 117 return springs, 118 electromagnetic assembly, 119 card member, and 120 back stopper. The electromagnetic assembly 118 consists of a bobbin 118a, a coil 118b, a core 118C and a yoke 118d. The bobbin 118a is secured to the yoke 118d and the core 1186 is arranged movable in said bobbin 118a. Said yoke 118d is secured to the support plate 1 16. The card member 1 19 is disposed on the contact assembly 107 while supported by the return springs 117a, 1 17b. Said card member 119 is provided on both sides thereof with protuberances 1191) 119e and recesses l 19f, l 19g designed to define the movable range of the card member 119. Said card member also has at its one end a protruding portion 1 19h adapted to join with the core 1180 of said electromagnetic assembly 118. The back stoppers 120a, 120b are secured to both sides of the header 106 and fit in the recesses 119f, 119g, respectively, formed in the card member 119.

When the electromagnetic assembly 118 is inoperative, the card member 119 is forced by the return springs 117a, 117b to one of the positions defined by the back stopper 120, and when the electromagnetic assembly 118 is energized, said member 119 is now attracted by the core 1180 to move to the other position defined by said back stopper 120. Contact opening and closing of the contact assembly 107 is effected with said movement of the card member 119.

FIG. 10 shows, in perspective, still another embodiment of the present invention. As will be seen, header 106, return springs 1 17, electromagnetic assembly 118, back stopper 120 and driving lever support 121 are mounted on a base plate 116. The electromagnetic assembly 118 consists of a bobbin 118a, a coil 118b, a core 118C, a yoke 118d and an armature 1l8e. The core 1186 is secured to the yoke 118d which is in turn secured to the base plate 116. The card member 119 is supported parallel to the header 106 on the contact assembly 107 by return springs 117a, l 17b. Supported swingably by the support 121 is a working lever 122 of which one end 122a is pivotally secured to a central part of the card member 119 and the other end l22b has secured thereto the armature 118e of the electromagnetic assembly 118. The back stopper 120 is fixed at a location opposed to the core 118C for defining the movable range of the armature 1182 secured to the working lever 122. In a situation where the electromagnetic assembly 118 is inoperative, the card member 119 is moved to the position defined by the back stopper 122 under elastic pressure of the return springs 117a, 117b, and when said electromagnetic assembly 118 is energized, the armature ll8e secured to the working lever 122 is attracted by the core 118C to let the card member 119 move with swing of the working lever 122, thus effecting touching and separation of contacts of the contact assembly 107 through protuberances 1l9b 11% on the card member 119.

Thus, according to the present invention, the header assemblage can be accomplished by merely mounting groups of integrated terminals on the base plate, while the contact assembly can be formed by merely fixing the integrated movable contact springs to the header. Also, highly stable operation is ensured as the contact assembly employs a lift-off system in which closing or touching of contacts is accomplished by the force of elastic pressure of the movable contact springs while separation of contacts is effected by utilizing a driving force opposing said elastic pressure of said movable contact springs.

in a certain embodiment of the present invention, there was shown a miniature electromagnetic relay in which the terminals are secured by a glass sheet in a metal frame, with the support member being fixed to said metal frame, but a similar relay can be also obtained without using said metal frame, by instead fixing the terminals to the opposing sides of the glass sheet and securing the support member to said glass sheet.

In still another embodiment of the present invention, there is an arrangement in which the movable contact springs are provided in pairs so as to be contactible with the opposed sides of the stationary contact pieces, with the protuberances provided on the card member being disposed between said movable contact springs. It is also possible to obtain a desired miniature electromagneticrelay by employing an arrangement in which a single movable contact spring is provided contactible with the side of each stationary contact piece, so that said movable contact spring will be actuated by a corresponding protuberance on the card member.

What is claimed is:

l. A miniature electromagnetic relay including a header comprising an insulating base plate and a plurality of L-shaped terminals, said terminals being arranged in two rows with the first arms of said respective terminals being positioned on one side of said insulating base plate and the second arms of said respective terminals being projected out from the other side of said insulating base plate; a contact assembly comprising stationary contact pieces secured vertically to the first arms of one group of terminals and movable contact springs secured at one end to the first arms of the other group of said terminals, each of said movable contact springs being arranged in contactable relationship at its other end with a corresponding one of said stationary contact pieces; a card structure movable in a direction parallel to the surface of said header and having protuberances provided adjacent corresponding stationary contact pieces; an electromagnetic assembly adapted to attract said card structure to thereby effect a touching and separation operation between said stationary contact pieces and said movable contact springs; and a return spring adapted to restore the original position of the card structure after it has been moved by the said electromagnetic assembly.

2. A miniature electromagnetic relay as set forth in claim 1 and further including a support member to which said electromagnetic assembly and said return spring are secured and which is fixed on said header, wherein said card structure is supported at its one end by an end of said return spring and also supported at its other end by an end of an armature in said electromagnetic assembly, so as to retain said card structure movable parallel to the header surface.

3. A miniature electromagnetic relay as set forth in claim 1, wherein said plurality of terminals are secured to the opposing sides of said insulating base plate and said support member is also fixed to said insulating base plate.

4. A miniature electromagnetic relay as set forth in claim 1, wherein said card structure is supported movable parallel to the header surface by a plurality of return springs.

5. A miniature electromagnetic relay as set forth in claim 1, further including another base plate for mounting the header thereon, said another base plate also having amounted thereon said electromagnetic assembly.

6. A miniature electromagnetic relay as set forth in claim 1 and further including another base plate adapted for mounting thereon said header and said electromagnetic assembly, wherein said armature of said electromagnetic assembly and said card structure are connected by a lever supported to be swingable about a fixed pin and parallel to the surface of said second base plate.

7. A miniature electromagnetic relay as set forth in claim 1, wherein said movable contact springs are provided in pairs for each of the stationary contact pieces so as to be contactable with the opposing side faces of said stationary contact pieces, with said protuberances being disposed between each said pair of movable contact springs.

8. A miniature electromagnetic relay as set forth in claim 1 and further including a metal frame and a cover, said header being secured airtightly surrounding said insulating base plate, wherein said cover is airtightly fixed to said metal frame so as to seal at least said electromagnetic assembly, said card structure, and said contact assembly.

9. A miniature electromagnetic relay as set forth in claim 1, wherein the movable contact springs are provided one for each of the stationary contact pieces.

Claims

1. A miniature electromagnetic relay including a header comprising an insulating base plate and a plurality of L-shaped terminals, said terminals being arranged in two rows with the first arms of said respective terminals being positioned on one side of said insulating base plate and the second arms of said respective terminals being projected out from the other side of said insulating base plate; a contact assembly comprising stationary contact pieces secured vertically to the first arms of one group of terminals and movable contact springs secured at one end to the first arms of the other group of said terminals, each of said movable contact springs being arranged in contactable relationship at its other end with a corresponding one of said stationary contact pieces; a card structure movable in a direction parallel to the surface of said header and having protuberances provided adjacent corresponding stationary contact pieces; an electromagnetic assembly adapted to attract said card structure to thereby effect a touching and separation operation between said stationary contact pieces and said movable contact springs; and a return spring adapted to restore the original position of the card structure after it has been moved by the said electromagnetic assembly.