Electromagnetic relay

In an electromagnetic relay, one of the spring members of the electromagnetic relay is fixed to a cubic corner protrusion of a base block of a housing. Side projections provided in the spring member are fitted into deep holes which adjoin a slot in the cubic corner protrusion so that the spring member becomes firmly fixed to the base block.

TECHNICAL FIELD 
The present invention relates to an electromagnetic relay, particularly to 
the structure for the fixing of a spring member of the electromagnetic 
relay to the base block of the housing of the electromagnetic relay. 
BACKGROUND OF THE INVENTION 
The electromagnetic relay of the present invention is of a small size, for 
example 32.times.35.times.32 mm, wherein an assembly of elements of the 
electromagnetic relay, such as an electromagnet, an armature, a card, a 
movable contact carried on a movable contact spring, a fixed contact 
carried on a fixed contact spring, and a restoring spring, is encased in a 
housing formed by a plastic base block and a plastic cover. 
A prior art structure for fixing one of the springs of the electromagnetic 
relay, for example, the restoring spring, to the base block is illustrated 
in FIG. 1. The electromagnetic relay of FIG. 1 comprises a plastic base 
block 1', a restoring spring 2', a movable contact spring 3', a fixed 
contact spring 4', a card 5', an armature 6' and an electromagnet 7'. The 
electromagnet 7' comprises a core 73', a bobbin 72', a coil 71' and a yoke 
74'. 
The two terminal conductors (not shown) of the coil 71', the terminal 
conductor 32' of the movable contact spring 3', and the terminal conductor 
42' of the fixed contact spring 4' penetrate through the corresponding 
apertures of the base block 1' so that the structure of the electromagnet 
is coupled to the base block 1'. Also, in order to ensure the fixing of 
the restoring spring 2' to the base block 1', one end of the restoring 
spring 2' is pressed into a slot 111' in the cubic corner protrusion 11' 
of the base block 1'. 
However, in the prior art structure of FIG. 1, there is a problem in that 
the restoring spring 2' is not sufficiently firmly fixed to the cubic 
corner protrusion 11', because such a mere pressing of the restoring 
spring 2' into the slot 111' cannot achieve a firm holding of the 
restoring spring 2' by the cubic corner protrusion 11'. This is because, 
when the restoring spring 2' is subjected to frequent spring action or is 
subjected to vibrations, the restoring spring inevitably becomes loosened 
from the cubic corner protrusion 111'. 
In the structure of FIG. 1, the thickness of the restoring spring 2' cannot 
be thicker than a predetermined thickness, due to the design requirements 
of the electromagnetic relay, while the gap length of the slot 111' cannot 
be smaller than a predetermined length due to the plastic moulding process 
requirements. Under these circumstances, in the prior art structure, a 
restoring spring is constructed in which the thickness of the end portion 
corresponding to the slot of the cubic corner protrusion is larger than 
the thickness of the rest of the restoring spring or in which a depression 
is formed by a shock-pressing process near the end portion of the 
restoring spring corresponding to the slot of the cubic corner protrusion 
causing the effective thickness of the end portion to be increased, so as 
to make the thickness of the end portion of the restoring spring match the 
width of the gap of the slot in the cubic corner protrusion. 
However, there is also another problem in that the manufacture of such a 
restoring spring, consisting of portions having different thicknesses, 
increases the cost of the production of the device and in that the fixing 
of the restoring spring, having such a depression in the end portion, to 
the slot of the cubic corner protrusion does not provide a completely firm 
fixing there between. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide an improved structure of 
the electromagnetic relay of the type described above, wherein the above 
described problem is solved and a satisfactorily firm fixing between an 
element of the electromagnetic relay and the base block of the housing is 
achieved, so that a satisfactory structure and a reliable operation of an 
electromagnetic relay are ensured. 
According to the present invention, there is provided an electromagnetic 
relay comprising a base block, an electromagnet, an armature, a card and a 
plurality of spring means, wherein a cubic protrusion is formed on a 
predetermined portion of said base block, a slot having deep holes 
adjoining said slot is formed in said cubic protrusion, a plurality of 
side projections are formed in a portion of at least one of said spring 
means, and said portion of said spring means having said plurality of side 
projections is inserted into said slot of said cubic protrusion, in such a 
manner that said plurality of side projections are inserted into said deep 
holes of said slot.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The structure of an electromagnetic relay in accordance with an embodiment 
of the present invention is illustrated in FIGS. 2 through 8. A 
perspective view of the electromagnetic relay is illustrated in FIG. 2. A 
perspective view of the important portion of FIG. 2 is illustrated in FIG. 
3. The detailed structure of the electromagnetic relay of FIG. 2 is 
illustrated in FIGS. 4, 5, 6, 7A, 7B and 8. 
The electromagnetic relay of FIG. 2 comprises a plastic base block 1, a 
restoring spring 2, a movable contact spring 3, a fixed contact spring 4, 
a card 5, and armature 6 and an electromagnet 7. The electromagnet 7 
comprises a core 73, a bobbin 72, a coil 71 and a yoke 74. The fixed 
contact spring 4, the movable contact spring terminal 32 and the two 
terminal conductors of the coil 71 penetrate through the apertures 12, 13, 
14 and 15, respectively. The assembly of the electromagnet 7, the armature 
6, the card 5, the fixed contact spring 4, the movable contact spring 3 
and the restoring spring 2 is encased in a housing consisting of the base 
block 1 and a cover (not shown). 
When the coil 71 of the electromagnet 7 is energized, the lower portion of 
the armature 6 is attracted by the core 73 to effect a pivoted motion of 
the armature 6, and hence the upper portion of the armature 6 pushes the 
card 5 upwardly. The free end of the movable contact spring 3 is pushed 
upwardly by the upward motion of the card 5 to cause the fixed contact 41 
to come in contact with the movable contact 31. At the same time, the left 
end of the restoring spring 2 connected to the card 5 is pushed upwardly 
by the upward motion of the card 5 against the resilient force of the 
restoring spring 2. 
When the coil 71 of the electromagnet 7 is deenergized, the resilient force 
of the restoring spring 2 causes the card 5 to move downward, and hence 
the free end of the movable contact spring 3 is pushed downward by the 
downward motion of the card 5 to cause the movable contact 31 to become 
disengaged from the fixed contact 41. 
The restoring spring 2 is fixed at its right end to a cubic corner 
protrusion 11 of the base block 1, as illustrated in FIGS. 2, 3, 4 and 5. 
The fixing structure will be described with reference to FIGS. 6, 7A, 7B 
and 8. 
The cubic corner protrusion 11 of the base block 1 has a horizontal slot 
111 in the direction parallel with the surface of the restoring spring 2. 
At the bottom of the horizontal slot 111, there are provided a plurality 
of deep holes 111a, 111b. Between these deep holes 111a and 111b, a cubic 
column 111m is formed. 
The restoring spring 2 has, in general, a rectangular shape, except that 
towards one end thereof a plurality of side projections 21 and 22 is 
provided. The width w.sub.a of the deep hole 111a illustrated in FIG. 7A 
is a little less than the width w.sub.b of each of the side projections 
21, 22. The restoring spring 2 is provided at one end, opposite to that on 
which the projections are located with a rectangular hole 24 into which 
the upper end of the card 5 is fitted. At the end portion where the side 
projections 21, 22 are located, a downward depression 25 of the restoring 
spring 2 is provided, said depression 25 being formed by a shock-pressing 
process or the like. The restoring spring 2 may be provided with a 
circular hole 26, shown in broken lines, through which the upper portion 
of the fixed contact spring 4 is allowed to penetrate. It is possible to 
provide depressions 211 and 221 in the side projections 21, 22, said 
depressions 211 and 221 being formed by a shock-pressing process or the 
like. 
The fixing of the restoring spring 2 to the cubic corner protrusion 11 of 
the base block 1 is carried out by inserting one end of the restoring 
spring 2 into the slot 111 of the cubic corner protrusion 11. When the end 
portion of the restoring spring 2 is inserted into the slot 111 of the 
cubic corner protrusion 11, the side projections 21 and 22 are inserted 
into the deep holes 111a and 111b, respectively. The top of the cubic 
column 111m abuts against the side edge portion 23 of the restoring spring 
2 between the side projections 21 and 22. Thus, the end portion of the 
restoring spring 2, including the side projections 21 and 22, is firmly 
fixed to the cubic corner protrusion 11 of the base block 1, as 
illustrated in FIGS. 2, 3 and 6. 
According to the fixing structure illustrated in FIGS. 2, 3 and 6, even 
when the restoring spring 2 is frequently subjected to a spring action and 
vibrations, the cubic corner protrusion 111 and the restoring spring 2 
remain firmly fixed, so that no loosening of the restoring spring 2 from 
the cubic corner protrusion 111 takes place. 
Although a preferred embodiment has been described hereinbefore with 
reference to FIGS. 2 through 8, various modifications are possible in the 
embodiments of the present invention. For example, it is possible to form 
the side projections 21 and 22 in the direction other than a right angle 
with respect to the longitudinal direction of the restoring spring 2, 
although in the embodiment of FIG. 7B the side projections 21 and 22 are 
formed in the direction of a right angle with respect to the longitudinal 
direction of the restoring spring 2. 
Also, it is possible to form the side projections having a tapered edge in 
order to make the insertion of the side projection into the deep holes 
easy. Also, it is possible to increase the number of the side projections, 
although the restoring spring having two side projections is illustrated 
in FIG. 7B. Also, although the structure illustrated in FIGS. 2 through 8 
relates to the fixing structure of the restoring spring, it is possible to 
adopt this fixing structure for the fixing of the fixed contact spring or 
the movable contact spring to the base block.