Self-aligning spring mechanism for an electrical switch

An electromagnetically operated relay having a spring which compensates for misalignment of a moveable block as shown and described. The movable block reciprocates within said relay housing in response to forces exerted by the electromagnet. The block includes projections which engage openings in an leaf spring which biases the block. The spring to block engagement provides compensation for misalignment of the block, and for unequal forces applied to the block and/or spring. The compensation provided by the spring to block engagement is achieved by a loose fit between projections on the slidable block and openings in the spring. The freedom of movement provided by the slots allows the spring to bulge in a direction opposite to the force on the spring end with respect to the sliding block. By creation of this bulge between the two two projections on the sliding block, compensation is provided to the spring system. The compensation is produced by the bulge which in turn forces the opposite end of the spring to move in the direction of movement of the first end. By this compensation, parallel movement of the sliding block is assured.

BACKGROUND OF THE INVENTION 
This invention relates to an electromagnetic relay, and in particular to an 
electromagnetic relay in which a movable block reciprocates in parallel 
relation for activating a contact mechanism. 
DESCRIPTION OF THE PRIOR ART 
Conventionally, in an electromagnetic relay of this type, a restoring means 
for the movable block is constructed by securing a middle portion of a 
sheet spring to a middle portion of a movable table by fitting means or 
the like so as not to become loose, and by engaging the two ends of this 
sheet spring to a fixed block. The spring is prevented from moving about 
the projection from the block which holds the spring. 
However, according to such a structure, there is a shortcoming that if the 
spring forces at the two ends of the sheet spring are not uniform because 
of some error in the bending angle, then the action timing of the movable 
block tends to be deteriorated, and it tends to move obliquely instead of 
in parallel relation, thereby damaging the action properties of the 
contact mechanism. 
BRIEF SUMMARY OF THE INVENTION 
A primary object of this invention is to provide an electromagnetic relay 
in which the instability of the action of the movable block arising from 
the unevenness of the spring forces of the sheet spring is diminished and 
the action properties are improved. 
To accomplish such an object, the electromagnetic relay of this invention 
is characterized by having two engagement portions provided in lengthwise 
mid portions of a sheet spring loosely engaged to projections provided in 
the movable block and by two ends of this sheet spring being engaged to a 
fixed block whereby the movable block is imparted with restoring force. 
The uneven bending produced by one spring end produces a bulge in the 
region between the projections which in turn produces a movement of the 
second end of the spring in the same direction as the first movement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIGS. 1 to 4, the electromagnetic relay of this invention is built as a 
high frequency relay and is generally comprised of a fixed block 1, and 
electromagnetic unit 10, a movable block 20, a pair of sheet springs 30, 
35, and a casing 40. 
The fixed block 1 is made by fixedly securing a terminal block 8 having 
fixed terminals 9a, 9b, 9c to a rectangular slot 3 of a base 2 which is 
integrally formed from appropriate resin. The contacts (tips) 9a', 9b'l , 
9c' of the fixed terminals are located in the slot and the internal wall 
of the slot 3 is provided with the ground contacts 6a, 6b, . . . 6f 
opposite to the contacts 9a', 9b', 9c'. Four ground terminals 7 project 
from the reverse surface of the base 2 and the ground terminals 7 are 
connected to the ground terminals 6a, 6b, . . . 6f by way of 
electroconductive film plated on the surface of the base 2. It goes 
without saying that the electroconductive film is insulated from the fixed 
terminals 9a, 9b, 9c. 
The electromagnetic unit 10 is made by inserting an I-shaped iron core 11 
through a spool 12, winding a coil 17 therearound, and integrally 
connecting the spool 12 and a yoke 19 and is attached to a depression 4 of 
the base 2. The spool 12 is connected to the yoke 19 by inserting a 
projection piece 19a of the yoke 19 into a hole 13a of a base block and 
engaging a side portion 13b of the base block to a projection piece 19b. 
And coil terminals 18 are mounted to the base blocks 13 and project 
downwardly from the base 2. 
The movable block 20 is built by fixedly securing the armatures 26a, 26b to 
frame portions 22 of the movable body 21 which is integrally formed with 
appropriate resin and interposing permanent magnets 27 therebetween and by 
fittingly inserting insulator bodies 28 having movable contact pieces 29 
into holes 23. This movable body 21 is so disposed that the armatures 26b 
oppose the projecting ends of the iron core 11 from the spool 12 at a 
fixed gap and are interposingly held by sheet springs in a reciprocable 
manner in parallel relation along the directions indicated by arrows 
A--A'. 
A projecting piece 31 in a middle portion of the sheet spring 30 is 
inserted into a groove 5a of the base 2 and the two ends of the sheet 
spring 30 are inserted into grooves 24 of the movable body 21. Notches 36 
of the sheet spring 35 loosely receive small projections 25 formed in the 
movable body 21 and the two ends of the sheet spring 35 are inserted into 
grooves 5b of the base 2. 
In the above described structure, when the coil 17 is not magnetized, the 
movable block 20 is affected by the magnetic force of the permanent 
magnets 27 in such a manner that an attractive force acts between the pole 
surfaces of the iron core 11 and the armatures 26b, the movable block 20 
moves in the direction indicated by the arrow A', the two ends of the 
movable contact piece 29 a engage to the contacts 9b', 9c', and the two 
ends of the movable contact piece 29b contact the ground terminals 6a, 6b. 
When the coil 17 is energized, an attractive force is produced between the 
pole surfaces formed in the two ends of the iron core 11, and the 
armatures 26a in such a manner that the movable block 20 moves in the 
direction indicated by the arrow A, the two ends of the movable contact 
piece 29b contact the contacts 9a', 9c', and the two ends of the movable 
contact piece 29a contact the ground contacts 6d, 6f. 
The load curve in the action of the above described embodiment is shown by 
a curve X shown in FIG. 6. This load curve is made by combining the spring 
forces a, b of the sheet springs 30, 35 and the spring forces c, d of the 
movable contact pieces 29a, 29b. The adjustment of the load curve is made 
by primarily changing the spring forces arising from the bending angles of 
the sheet springs 30, 35. As clearly shown in FIG. 6, the spring force a 
of the sheet spring 30 is expressed by an inclined straight line, and its 
change causes an overall vertical displacement of the load curve. The 
spring force b of the sheet spring 35 is indicated by a straight line 
which is bent in a middle portion of the stroke of the movable block 20 
and its change primarily determines the inclination angle of the load 
curve. 
Meanwhile, because the notches 36 of the sheet spring 35 loosely receive 
the small projections 25 of the movable body 21, even when there is some 
unevenness between the spring forces at the two ends the sheet spring 35 
by itself shifts itself according to the gap between the notch 36 and the 
small projection 25 and the difference between the spring forces is 
absorbed, thereby allowing reciprocating motion of the movable block 20 
with an appropriate degree of parallel relation. 
Specifically, as shown in FIGS. 4 and 5, notches 25a are formed above and 
below the root of the projection 25 projecting from the movable body 21, 
and the notch 36 of the sheet spring 35 loosely receives this root 
portion. Therefore, the sheet spring 35 is freely movable in four or eight 
directions in the vertical plane by the distances corresponding to the gap 
between the notch or opening 36 and the root of the small projection 25 
and is prevented from coming off. 
The spring 35 extends transversely to the movement of the block 20 as shown 
by arrows A and A' of FIG. 2. 
And as shown in FIG. 5, when a pressing force in the direction indicated by 
the arrow B acts upon the left end 37, the left support portion is shifted 
slightly and the middle portion of the sheet spring 35 is bulged out and 
the right support portion is shifted slightly and the right end 37 also 
bends in the same direction as that indicated by the arrow B. This shift 
of the spring with respect to the left support is in a longitudinal 
direction with respect to the spring. This slight shift perits the center 
of the spring to bulge forward in the direction of block movement. This 
shift is transverse to the direction of block movement. 
In other words, even when there is unevenness in the bending angles of the 
sheet spring 35, it adjusts itself so that the angle theta is identical in 
any instance, by automatic compensation. As a result, the spring forces at 
the two ends 37 of the sheet spring 35 become equal to each other, and the 
instability that the movable block 20 is inclined as it is activated is 
eliminated, and the action properties of the switching of the contact 
mechanism are improved. 
As can be seen in FIG. 5b, opening or notch 36 is larger than notch 25a of 
projection 25 and extends in a longitudinal direction. 
The electromagnetic relay of this invention is not limited by the above 
described embodiment, but may be modified in various manners, without 
departing from the spirit of the invention. For instance, the engagement 
portion of the sheet spring 35 may not be a notch 36, but may be a hole 
(see FIGS. 5a, 5b), and may be straight, without being bent at the ends 37 
thereof. However, if the sheet spring 35 is bent along the direction of 
its action, as shown in FIG. 5, the fulcrum of the sheet spring 35 itself 
is more stabilized, and the ends 37 are prevented from engaging to the 
movable body 21, as an advantage. 
As can be seen from the above description, according to this invention, 
because two engagement portions provided in the lengthwise middle portions 
of the sheet spring are loosely engaged to the projections provided in the 
movable block, the spring forces of the sheet spring are automatically 
adjusted by the gap in the loosely engaged portion, the unstable action is 
eliminated, and the action properties are improved.