US3701062A

US3701062A - Electromagnetic relay

Info

Publication number: US3701062A
Application number: US145380A
Authority: US
Inventors: Hirohumi Koga; Ryuichi Sato
Original assignee: Omron Tateisi Electronics Co
Current assignee: Omron Corp
Priority date: 1970-05-26
Filing date: 1971-05-20
Publication date: 1972-10-24
Anticipated expiration: 1989-10-24
Also published as: GB1308770A; DE2126214B2; DE2126214A1

Abstract

An electromagnetic relay including a spool member having a base with recesses in opposite sides, a flange, and a stem portion connecting the base and flange. The stem portion surrounds the core, a coil is wound on the stem portion. The armature is disposed generally parallel with the core. A plug member is adapted to be fitted into the recesses in the spool base to hold the armature.

Description

United States Patent Koga et al.

[54] ELECTROMAGNETIC RELAY [72] Inventors: Hirohumi Km; Ryuichi Sato, both of Kyoto, Japan [73] Assignee: Ornron Tateisl Electronics Co.,

Kyoto, Japan 22 Filed: Ma 20,1971' [211 Appl.No.: 145,380

301' Foreign Application Priority Data May 26, 1970 Japan ..45/45s22 Sept. 9, 1970 Japan ..45/80118 s21 u.s.c|.....-, .L ..33s/13s,335/202 51 Int. Cl. ..H0lh 51/06 [58] Field of Search ..335/l35, 128, 281,131, 202, 335/179; 336/208, 198, 192

[56] References Cited UNITED STATES PATENTS 2,786,163 3/1957 V'igren et a]. ..335/28l [451 Oct. 24, 1972 2/1971 Horbach ..336/l98 11/1969 DEntremont ..'.336/ 198 Primary Examiner-Harold Broome Attorney-Christensen & Sanborn [57] ABSTRACT An electromagnetic relay including a spool member having a base with recesses in opposite sides, a flange, and a stem portion connecting the base and flange.

The stem portion surrounds the core, a coil is wound on the stem portion. The armature is disposed generally parallel with the core, A plug member is adapted to be fitted into the recesses in the spool base to hold the armature.

15 Claims, 21 Drawing Figures P'A'TENTEDucmmn 3.701.062 sum 3 or 6 ATTORNEYS PKTENTHI I973 3.701.062

saw u or 6 INVENTOR MFOHUM/ KOGA ELECTROMAGNETIC RELAY This invention relates to an electromagnetic relay wherein the contact is instaneously closed or opened upon energization of the coil and restored upon deenergization thereof.

There is known an electromagnetic relay which includes a stationary or fixed iron core and an armature supported at one end thereof so as to be movable relativeto the fixed iron core, and upon movement of the armature the movable contact directly or indirectly mounted on the armature is brought into or out of contact with a fixed contact provided at a suitable position. The relay of this type, therefore, chiefly comprises a coil, fixed iron core, an armature, a movable contact, a

fixed contact, a coil spool, etc.

In one known type of relay, the armature is secured by means of screws to the stationary iron core through a spring member, and the contact carrying members have their respective one ends secured to a frame or the coil spool by means of screws. Thus, a yoke, screws, spring members and various other parts are required to assemble the relay, and not only the work requires much time and labor but also adjustment of the parts is troublesome. Furthermore, it is difficult to make the relay compact'in size, and reduce the manufacturing cost.

Accordingly, the primary object of the invention is to provide an electromagnetic relay which is free from the above defects of known relays of similar types.

Another object of the invention is to provide such an electromagnetic relay as aforesaid which is compact in size, with various component parts arranged in a rational manner.

Another object of the invention is to provide such an electromagnetic relay as aforesaid, which requires a less number of component parts than in the prior art devices, with resulting easiness in assembling the parts into the relay.

Still another object of the invention is to provide such an electromagnetic relay as aforesaid, which requires no screws or like parts in assembling the components,-so that readjustment of the parts, if necessary after assembling the parts, becomes easy.

The invention will become apparent from the following detailed description of preferred embodiments thereof with reference to the accompanying drawings, wherein;

FIG. 1 is a front elevation of one embodiment of the invention;

FIG, 2 is top plan view of FIG. 1;

FIG. 3 is a bottom view of FIG. 1;

FIG. 4 is a left-hand side view of FIG, 1;

FIG. 5 is a right-hand side view of FIG. 1;

FIG. 6 is a perspective view of the coil spool;

FIG. 7 is an elevation of the coil spool as viewed in the direction of the arrow 7 in FIG. 6;

FIG. 8 is a left-hand side view of FIG. 7, with some parts being eliminated;

' FIG. 9 is a perspective view of the stationary iron core;

FIG. 10 is a perspective view of the armature;

FIG. 1 1 is a perspective view of the plug;

FIG. 12 is a side view of the plug;

FIG. 13 is a perspective view of the plate connecting the armature and the movable contact carrying members;

embodiment of FIG. 19; and

FIG. 14 is a perspective view of the lower fixed contact carrying member;

FIG. 15 is a perspective view of the movable contact carrying member;

FIG. l6'is a perspective view of the upper fixed contact carrying member;

FIG. 17 is a view similar to FIG. 1 but showing the relay in a different condition;

FIG. 18 is a sectional view taken along line 18-18 in FIG. 17 showing the relation between the stationary iron core and the armature;

FIG. 19 is a view similar to FIG. 1 but showing another embodiment of the invention;

FIG. 20 is a perspective view of the plug used in the FIG. 21 is a transverse section of the plug of FIG. 20 showing the engagement with the armature.

In the following descriptiomvarious terms expressing positions, such as upper, right-hand, left-hand,

etc, are used with respect to the position of the relay assembly as itis shown in the various figures, and should not be taken to have any restrictive meanings.

Referring now to the drawings, first to FIGS. 1-5, there is shown a spool 10 made of a suitable plastic material, on which a coil 11 is mounted. A stationary iron core 12 is E-shaped and comprises a middle leg 13, both side legs 14 and a base bar 15 connecting the middle leg and the side legs at their respective one ends. The middle leg 13 extends axially through the coil 11, with the side legs 14 extending generally parallel at the opposite sides of the coil. The bar 15 is mostly exposed at the underside (right-hand side in FIGS. 1-3) of the plastic spool 10.

An armature 16 is U-shaped, comprising a pair of side legs 17 and an outer transverse bar 18 connecting the legs 17 at their respective outer (left-hand) ends. The armature 16 has the inner (right-hand) ends of its side legs 17 secured to the spool 10 so that the outer (left-hand) ends of the legs 17 with the connecting bar 18 are vertically movable, as will be described later in detail. The armature 16 is so disposed relative to the stationary iron core 12 that the side legs 17 of the armature 16 are positioned below and generally parallel with the side legs 14 of the core 12.

A pair of vertically (as viewed in FIGS. 1, 4, 5) spaced fixed

contact carrying members

19 and 20 are provided at one side of the coil 11 and have their respective right-hand ends secured to the spool 10. A similar pair of fixed

contact carrying members

19 and 20 are provided at the opposite side of the coil 11. Between the

members

19 and 20 there is interposed a movable contact carrying member 21 having its righthand end secured to the spool 10. The

members

19, 20 and 21 are vertically aligned in a plane perpendicular to the plane of the stationary core 12.

The outer (left-hand) free ends of the movable contact carrying members 21 are connected to the armature 16 by means of connecting plate 22, so that when the armature 16 is moved, its movement is transferred to the free ends of the movable contact carrying members 21 through the connecting plate 22. The resiliency of the movable contact carrying members 21 normally biases the armature 16 downwardly away from the stationary iron core 12 through the connecting plate 22. Under the condition, a movable contact 23 on the lower surface of the free (left-hand) end of each member 21 contacts a fixd contact 24 on the upper surface of the outer (left-hand) end of each lower fixed contact carrying member 19. When the coil 1 1 isenergized to attract the armature 16 onto the stationary iron core 12, the free ends of the movable contact carrying members 21 are moved upward away from the lower fixed contact carry members 19 against the inherent resiliency of the material of the members 21, as far as a movable contact 25 on the upper surface of the outer end of each member 21 'is brought into contact with a fixed contact 26 on the lower surface of each upper fixed contact carrying member 20 (see FIG. 17).

When the coil 11 is deenergized, the movable contact carrying members 21 returning to their original lower position due to their resiliency, so that the armature 16 is moved away from the iron core 12 through the connecting plate 22 back to the original position shown in FIG. 1. I

A transparent cover 27 made of a suitable plastic material has a pair of holes 28 formed in the opposite side walls adjacent an end opening, through which the relay assembly is put into the cover. The cover 27 is secured to the spool by engagement of a pair of projections 29 formed on the opposite sides of the spool with the holes 28. Under the condition, the connecting bar of the stationary iron 12 is exposed at the lower (right-hand) surface of the spool 10, with a resulting increase in the cooling efficiency of the iron core 12.

A pair of terminals 30 are secured to the spool 10 to supply energizing current to the coil 11.

As mentioned above, the fixed iron core 12, the armature 16, the contact carrying-

members

19, 20, 21 and the terminals 30 are all secured to the spool 11). FIGS. 6-8 show the spool in detail. The spool 10 comprises a stem portion 51 on which the coil 11 is wound, a base 52 and a flange 53. The base 52 has its opposite side portions 54 thicker than the middle portion thereof.

In each side portion 54 there are formed a first recess 57 defined by

walls

55 and 56, and a'second recess 59 defined by

wall

56, 58 and 67. In the first recess 57 there are formed three

grooves

61, 62, 63 extending along the axis of the stem portion 51, with a groove 64 extending transversely of the walls defining the grooves 61-63. A groove or notch 65 is formed in the middle wall 56. In the second recess 59 of each side portion 54 of the base of the spool 10 there is formed a slot 66 which extends horizontally in alignment with the slot 66 formed in the recess 57 of the opposite side portion 54 of the spool base, as most clearly shown in FIGS. 7 and 8. The common center line of the slots 66 crosses the axis of the stem portion 51 of the spool 10.

In the second recess 59 there is provided a block 68 projecting from the inner side of the wall 67. The block 68 defines a space 69 between itself and the middle wall 56 and a small gap 71 between itself and the lower wall 58 and also has a groove 70 extending in the same direction as the groove 64 in the first recess 57.

The lower fixed contact carrying member 19 as shown in FIG. 14 has its one end secured in the groove 63 of the first recess 57; the movable contact carrying member 21 as shown in FIG. 15 has its one end secured in the groove 62; and the upper fixed contact carrying member as shown in FIG. 16 has its one end secured in the groove 61.

The fixed iron core 12 has its middle leg 13 (FIG. 9) inserted through an axial bore 51' of the stem portion 51 of the spool 10 in the direction of an arrow 7 (FIG. 6), with the side legs 14 of the core passing through the slots 66 to extend alongside the stem portion 51 and the connecting bar 15 being fitted in the slots 66. The terminals 30 are secured in the gaps 71.

With the iron core 12, the contact carrying members 1921 and the terminals 30 having been secured in place in the above-mentioned manner, a block or plug generally designated by 81 in FIGS. 11 and 12 is fitted into the

recesses

57 and 59 in-each side portion 54 of the spool base thereby to fix the member in place. The plug 81 is made of a suitable plastic material and comprises a head 82 adapted to be fitted into the first recess 57, a stem portion 83 adapted to engage in the notch 65, and

projections

84 and 85 adapted to engage in the space 69 and the gap 71, respectively. As the head 82 is fitted into the recess 57, a projection 86 formed on the head 82 engages into the groove 64. A groove 87 (FIG. 12) is formed in the projection 86 so that the projection 86 will not completely fill the groove 62.

The stem portion 83 of the plug 81 is borne against the lateral side of each side leg 14 of the iron core 12 to securely hold the core in place. To put it in further detail, the side legs 14 of the iron core 12 have a notch 140 as shown in FIG. 9, in which the stem portion 83 of the plug 81 is fitted into the side recesses of the base of the spool 10, the iron core 12 will not fall off unless the plug 81 is removed therefrom. The projection 84 of the plug engaging in the space 69 in the recess 59 of the spool base helps to securely hold the iron core in place by sandwiching the side leg 14 between the projection of the plug and the middle wall 56 of the spool base 52.

The plug 81 is bonded to the spool base 52 by means of a suitable adhesive or supersonic waves.

The projection 84 of the plug 81 is formed on its upper surface 88 with a groove 89, which defines a shoulder at one end of the projection 84. The armature 16 is supported by means of the groove 89 and the shoulder 90 so that the outer free end of the armature is vertically movable. As shown in FIG. 10, the side legs 17 of the armature 16 have their respectove one ends recessed as at 91 to define a finger 92. The shoulder 90 of the plug 81 loosely engages in the recess 91, with the finger 92 loosely engaging in the groove 89 (FIG. 1). Under the condition, the upper surface of the shoulder 90 contacts the under surface of the side leg 14 of the stationary iron core 12, thereby preventing the armature from falling off from the plug while ensureing the verticlal movement thereof relative to the fixed iron core 12.

The connecting bar 18 of the armature 16 has its central portion a little recessed as at 93 in the direction away from the outer free end of the middle leg 13 of the iron core 12. With this arrangement, when the armature 16 is attracted by the stationary iron core 12, the side legs 17 of the armature 16 contact the side legs of the iron core 12, but the connecting bar 18 of the armature does not contact the free end of the middle leg 13 of the iron core 12 due to the presence of a gap 93' caused by the recess 93 (see FIG. 18). This gap helps cause rapid disappearance of the remaining magnetic flux when the coil 11 is deenergized, so that continuation of the attracted condition of the armature 16 to the fixed iron core 12 is prevented. In stead of the recess 93, the outer end of middle leg 13 of the core 12 may be bent upwardly to avoid contact with the connecting bar 18 of the armature.

As previously mentioned, the movable contact carrying members 21 and the armature 16 are operatively connected by the connecting plate 22. To enable this connection a pair of notches 94 are formed in the outer ends of the side legs 17 of the armature 16 as best shown in FIG. 10. The connecting plate 22 has a pair of projections 96 on the under edge thereof, which engage the notches 94. The plate 22 is also formed with a pair of projections 95 on the upper edge thereof, each of which engages in a notch 21a (FIG. formed in the outer free end of each I movable contact carrying member 21. Thus, the two movable contact carrying members 21 are connected to the armature 16 by means of the plate 22. A recess 97 is formed in the lower edge of the plate 22 so as to make it possible to see through the recess 97 the connecting bar 18 of the armature 16 being attracted by the middle leg 13 of the stationary iron core 12 (FIG. 4).

The flange 53 of the spool 10 is provided at each of its opposite side edges with a pair of laterally projecting fingers or

stoppers

98 and 99 which are vertically spaced across a gap 100. The movable contact carrying member 22 has its outer free end passed through the gap between the

fingers

98 and 99, and the upper and lower fixed contact carrying members and 19 are urged adjacent their respective outer ends against the upper and

lower fingers

98 and 99, respectively, so that a constant gap is defined between the upper and lower fixed contacts 26 and 24 (see FIG. 1).

A projection 101 is formed on the outer surface of the flange 51 below the axial bore 51, and the connecting bar 18 of the armature is disposed between the projection 101 and the outer end of the middle leg 13 of the stationary iron core 12 which projects from the axial bore 51'. Under the condition that the coil 11 is deenergized, the armature is away from the iron core 12 but not farther down beyond the projection 101. In other words, the projection 101 helps keep constant the distance the armature is moved away from the stationary iron core 12.

In the embodiment of FIG. 1, the plug 81 is provided with the projection 84 having an extension along the length of the side leg 17 of the stationary iron core. This extension may be dispensed with. FIG. 20 shows a plug 81 the projection of which has no such extension. This plug 81 has a projection 84' adapted to be fitted into the space 69 formed in the side end of the base 52 of the spool 10. A rise 102 is formed on the upper surface of the projection 84, so that the notch 91 in each side leg 17 of the armature 16 loosely engages in this rise 102 (FIG. 21). With this arrangement, the inner (right-hand) end of each side leg 17 of the armature is secured by the plug 81 to the base 52 of the spool 10 within the space 69 as shown in FIG. 19 so that its outer (left-hand) end is vertically movable as in the previously described embodiment.

What we claim is:

1. An electromagnetic relay comprising: an E-shaped stationary iron core having a middle leg, side legs, and a transverse bar connecting said legs at their respective one ends;' a spool means comprising a base having recesses in opposite sides thereof, a flange, and a stem portion connecting said base and flange, said stem portion surrounding said iron core middle leg; a coil wound on said stem portion, said iron core side legs extending alongside said coil at both sides thereof; an armature disposed generally parallel with said stationary core and adapted to be attracted by said iron core upon energization of said coil; a pair of movable contact carrying members disposed so as to extend at both sides of said coil generally parallel with said iron core side legs; at least a pair of fixed contact carrying members opposed to said movable contact carrying members; plug means having portions adapted to be fitted into said recesses in said spool base so as to hold the end portions of said armature and said movable and fixed contact carrying members; means connecting said armature to said movable contact carrying members so that upon energization of said coil, said armature is attracted by said core thereby to cause the contacts on said movable contact carrying members to be moved into or out of contact with the contacts on said fixed contact carrying members.

2. The relay of claim 1, wherein said armature is U- shaped having two side legs spaced apart from each other and a transverse bar connecting the outer ends of said side legs, with a recess being formed in the one end of each of said armature side legs at the inner sides thereof, and wherein said spaced pair of movable contact carrying members have their respective free ends formed with a recess directed in the direction opposite to that of said recess formed in each said armature side leg, and wherein said connecting plate has a first pair of projections adapted to engage in said recesses in said armature side legs and a second pair of projections adapted to engage in said recesses in said movable contact carrying members.

3. The relay of claim 1, wherein said spool is provided with a stop means for restricting the distance said armature is moved away from said stationary iron core when said coil is deenergized.

4. The relay of claim 1, wherein said spool is provided with a stop means for determining the position of each said fixed contact carrying member relative to each said corresponding movable contact carrying member.

5. The relay of claim 2, wherein a gap is formed between said iron core middle leg and said connecting bar of said armature under the condition that said connecting bar is attracted by said iron core middle leg upon energization of said coil.

6. The relay of claim 1, wherein each said stationary iron core side leg has its one end supported by said base.

7. The relay of claim 1, further including a protective cover detachably mounted on said spool so as to cover the parts on said spool, with most of said transverse bar of said iron core being exposed outside said protective cover for cooling of said iron core.

8. The relay of claim 1, further including a pair of terminals secured to said spool base by means of said plug means.

9. The relay of claim 1, wherein each said plug means is provided with a projection and wherein said armature is U-shaped comprising a pair of armature side legs and a transverse bar connecting the free ends of said ara 7 mature side legs, the opposite end of each of which is supported by said projection of said plug means so that said free ends of said armature side legs with said connecting bar are movable relative to said fixed iron core.

10. The relay of claim 9, wherein said projection of said plug means has an extension along each of said iron core side legs, each of said armature side leg ends being supported by said extension.

11. The relay of claim 9, wherein said spool base is further provided with slots for said transverse bar of said iron core to be engaged in, and each said side leg of said stationary iron core has a notch formed adjacent the juncture with said transverse bar, and each said plug means has a portion engaging said notch in each said recess formed in said spool base thereby securing said iron core to said spool base.

12. The relay of claim 10, wherein said spool base is further provided with slots for said transverse bar of said iron core to be engaged in, and each said side leg of said stationary iron core has a notch formed adjacent the juncture with said transverse bar, and each said plug means has a portion engaging said notch in each said recess formed in said spool base thereby securing said stationary iron core to said spool base.

13. The relay of claim 1, wherein one of said recesses in each side portion of said spool base is provided with a plurality of grooves in each of which the one end of each of said movable and fixed contact carrying members is engaged.

14. The relay of claim ll, wherein one of said recesses in each side portion of said spool base is provided with a plurality of grooves in each of which the one end of each of said movable and fixed contact carrying members is engaged, and a groove crossing said first-mentioned grooves, and said spool base is further provided with slots for said transverse bar of said iron core to be engaged in, and each said side leg of said stationary iron core has a notch formed adjacent the juncture with said transverse bar, and each said plug means has a first portion engaging with said notch in said one recess, and a second portion having along each said side leg of said stationary core an extension which supports one of said side legs of said armature.

15. An electromagnetic relay comprising: an E- shaped stationary iron core having a middle leg, both side legs and a transverse bar connecting said legs at their respective one ends; a spool comprising a base having recesses in opposite sides thereof, a flange and a stem portion connecting said base and flange, said stem portion surrounding said iron core middle leg; a coil wound on said iron core middle leg; a coil wound on said stem portion, with said iron core side legs extending alongside said coil at both sides thereof; an armature disposed generally parallel with said stationary core and adapted to be attracted by said iron core upon energization of said coil; a pair of movable contact carrying members disposed so as to extend at both sides of said coil generally parallel with said iron core side legs; at least a pair of fixedcontact carrying members opposed to said movable contact carrying members; plug means having portions adapted to be fitted into said recesses in said spool base so as to hold the end portions of said armature, movable and fixed contact carrying members; means connecting said armature to said ovable contact c in membersso that u on energ ization of said coii, 831C? armature 1s attracte d by said core thereby to cause the contacts on said movable contact carry members to be moved into or out of contact with the contacts on said fixed contact carrying members, said recesses in each side portion of said spool base being provided with a plurality of grooves in each of which the one end of each of said movable and fixed contact carrying members is engaged, and a groove crossing said first-mentioned grooves, said spool base being provided with slots for said transverse bar of said iron core to be engaged in, each said iron core side leg having a notch formed adjacent the juncture with said transverse bar, each said plug means having a first portion engaging with said notch in said one recess and a second portion having along each said side leg of said stationary core an extension which supports one of said side legs of said armature.

Claims

1. An electromagnetic relay comprising: an E-shaped stationary iron core having a middle leg, side legs, and a transverse bar connecting said legs at their respective one ends; a spool means comprising a base having recesses in opposite sides thereof, a flange, and a stem portion connecting said base and flange, said stem portion surrounding said iron core middle leg; a coil wound on said stem portion, said iron core side legs extending alongside said coil at both sides thereof; an armature disposed generally parallel with said stationary core and adapted to be attracted by said iron core upon energization of said coil; a pair of movable contact carrying members disposed so as to extend at both sides of said coil generally parallel with said iron core side legs; at least a pair of fixed contact carrying members opposed to said movable contact carrying members; plug means having portions adapted to be fitted into said recesses in said spool base so as to hold the end portions of said armature and said movable and fixed contact carrying members; means connecting said armature to said movable contact carrying members so that upon energization of said coil, said armature is attracted by said core thereby to cause the contacts on said movable contact carrying members to be moved into or out of contact with the contacts on said fixed contact carrying members.

2. The relay of claim 1, wherein said armature is U-shaped having two side legs spaced apart from each other and a transverse bar connecting the outer ends of said side legs, with a recess being formed in the one end of each of said armature side legs at the inner sides thereof, and wherein said spaced pair of movable contact carrying members have their respective free ends formed with a recess directed in the direction opposite to that of said recess formed in each said armature side leg, and wherein said connecting plate has a first pair of projections adapted to engage in said recesses in said armature side legs and a second pair of projections adapted to engage in said recesses in said movable contact carrying members.

9. The relay of claim 1, wherein each said plug means is provided with a projection and wherein said armature is U-shaped comprising a pair of armature side legs and a transverse bar connecting the free ends of said armature side legs, the opposite end of each of which is supported by said projection of said plug means so that said free ends of said armature side legs with said connecting bar are movable relative to said fixed iron core.

14. The relay of claim 1, wherein one of said recesses in each side portion of said spool base is provided with a plurality of grooves in each of which the one end of each of said movable and fixed contact carrying members is engaged, and a groove crossing said first-mentioned grooves, and said spool base is further provided with slots for said transverse bar of said iron core to be engaged in, and each said side leg of said stationary iron core has a notch formed adjacent the juncture with said transverse bar, and each said plug means has a first portion engaging with said notch in said one recess, and a second portion having along each said side leg of said stationary core an extension which supports one of said side legs of said armature.

15. An electromagnetic relay comprising: an E-shaped stationary iron core having a middle leg, both side legs and a transverse bar connecting said legs at their respective one ends; a spool comprising a base having recesses in opposite sides thereof, a flange and a stem portion connecting said base and flange, said stem portion surrounding said iron core middle leg; a coil wound on said iron core middle leg; a coil wound on said stem portion, with said iron core side legs extending alongside said coil at both sides thereof; an armature disposed generally parallel with said stationary core and adapted to be attracted by said iron core upon energization of said coil; a pair of movable contact carrying members disposed so as to extend at both sides of said coil generally parallel with said iron core side legs; at least a pair of Fixed contact carrying members opposed to said movable contact carrying members; plug means having portions adapted to be fitted into said recesses in said spool base so as to hold the end portions of said armature, movable and fixed contact carrying members; means connecting said armature to said movable contact carrying members so that upon energization of said coil, said armature is attracted by said core thereby to cause the contacts on said movable contact carry members to be moved into or out of contact with the contacts on said fixed contact carrying members, said recesses in each side portion of said spool base being provided with a plurality of grooves in each of which the one end of each of said movable and fixed contact carrying members is engaged, and a groove crossing said first-mentioned grooves, said spool base being provided with slots for said transverse bar of said iron core to be engaged in, each said iron core side leg having a notch formed adjacent the juncture with said transverse bar, each said plug means having a first portion engaging with said notch in said one recess and a second portion having along each said side leg of said stationary core an extension which supports one of said side legs of said armature.