US2228522A - Switch - Google Patents

Description

Jam 1941. c. F. JOHNSON SWITCH Filed Dec. 51, 1937 Patented Jan. 14,1941

PATENT OFFICE SWITCH Clair F. Johnson, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application December 31, 1937, Serial No. 182,769

Claims.

This invention relates generally to the art of switches and more particularly to a switch of the snap action type which employs a resilient operating member.

5 It is an object of this invention to provide a snap action switch which has a minimum number of parts and yet is efllcient in operation.

Another object is to provide a switch which will produce a type of snap action which is similar to that produced by a permanent magnet and yet which does not use a magnet but is entirely mechanical in its operation, and therefore is much cheaper to manufacture.

These and other objects will become apparent as the following specification is read with reference to the accompanying drawing, in which the single figure is a more or less diagrammatic representation of my snap action switch.

The present switch is operated by means of a bimetallic coil thermostat II which has a fixed end l2 and which carries at its free end by means of rivets l3, a resilient operating arm ll having an end which is bent over as shown at IS. A contact arm I6 is shown as having a hole I1 at one end thereof through which is insertedthe end l5 of the operating arm. The other end l8 of the contact arm is provided with a second hole i9 through which is inserted one end 20 of a bowed compression spring 2|, the other end 22 of which bears against a notch 23 in a stationary support 24 to form a knife edge bearing. The end H! of contact arm I6 is bent over as shown at 25-t0 restrain the movement of a leaf spring 26 riveted to the end I8 as shown at 21. Carried by spring 28 is a movable contact 28 which is adapted to engage stationary contact 30 which is adjustably I mounted in the stationary support 33. An electrical conductor 3| is connected to the bimetallic spiral II at l2 and conductor 34 is connected to the stationary contact 30 for the purpose of connecting the twitch into a suitable control circuit. In order to assist in explaining the action of this switch, reference numeral A will be used to designate the point of contact of spring 2| with the stationary support 24, B will designate the contact point between spring 2| and contact armiii, and

C will designate the contact point between contact arm I6 and resilient arm I.

Assuming the parts are in the position shown in the single figure of the drawing it will be seen that the compression spring 2| is exerting a downward pull on the contact arm l6 at B which in turn exerts a downward pull on the inturned end l5 of the resilient arm II at C. The effect of this force is to tend to swing the point C toward the left due to the angle between the arm I 6 and an imaginary line connecting point C and point l3 at which arm I4 is supported. This movement will be resisted by the thermostatic element I I which will cause a slight bend in the arm M. It will be noted that there is a component of force exerted by spring 2| on arm I8 holding the point B thereof against the stop 29. This force is due to the angle between the arm l6 and an imaginary line 32 connecting the points A and B, or in 10 other words, the angle ABC. The line 32 is the line of force of the spring 2|. The stop 29 engages arm |6 at the point B and hence this engagement has no effect at the point C.

As the temperature to which the bimetal coil 15 responds decreases arm llwill be permitted to swing to the left until point C is on the line AB, at which time the pressure between contact arm l6 and stop 29 will be zero. It might be pointed out that as point C is moved back and 20 forth the effect of the force exerted by spring 2| on arm I 6 is to try to make point B follow point C in such a manner as to keep the points A, B, and C in the same straight line. Therefore, on a further drop in temperature, arm II will be per- 26 mitted to move point C to the left of the line AB and spring 2| will move point B away from stop 29 to align the points A, B, and C again. It will be seen that as point B moves to the left the angle between the contact arm 16 and arm H 30 increases which will cause arm H to bend further to move point C further to the left and spring 2| will continue to move point B to the left to try to keep the points A, B, and C in a straight line. In order to do this the point B must move much 35 farther than the point C and the bending force exerted by arm IS on the arm I4 is increased so rapidly due to the increase in the angle between arm I6 and arm H, after B has once left stop 29 that the result is a snap action which causes con- 40 tacts 28 and 30 to engage and which causes arm IE to swing point C well to the left of the line AB.

It will be seen that as arm I 6 is snapped to the left causing contacts 28 and 30 to engage that spring 26 will be deflected until the stop 35 on end 45 I8 of arm It strikes contact 28. The pressure between the contacts 28 and 30 will be determined at this point by the angle between the line 32 and contact arm l6.

Assuming now that the temperature begins to 50 rise, bimetal coil II will begin to unwind until it builds up enough force in arm ll to swing point C to the right in opposition to the force exerted by contact arm l6. As point C moves to a position on the line AB the contact pressure between 65 stop 35 and contact 28 will be zero but contacts 28 and 30 will still be held closed by spring 26. Upon further movement of point C to the right the spring 2| will move point B to the right to keep it aligned with points A and C which will reduce the angle between arms 16 and H. The reduction of this angle reduces the moment arm through which the arm I6 exerts its bending force on the arm [4. Thus the bending force is reduced and arm 14 will straighten out slightly which will in turn move point C farther to the right. Point B will follow and cause a further reduction in the bend in arm H which moves C still farther to the right. This action occurs rapidly once point B has started moving and the result is a snap action.

The snap action is accomplished because of the resilience of the arm l4. As the switch snaps to the left from the position shown in the drawing a force is stored in arm I4 by bending it more than it is bent in the drawing. This bending is caused by the increase in the angle between arms i6 and 14. As the switch is moved to the right the angle between arms l6 and I4 is reduced which reduces the bending force and the force stored up in arm I4 is released to produce the snap action.

It will therefore be seen that I have devised a snap action switch which is extremely simple and reliable in operation and which employs a minimum number of parts. This switch has the added advantage that it will be cheap to manufacture.

As certain modifications and changes may occur to those who are skilled in the art it is to be understood that I am not limited by the specific embodiment disclosed, but the limits of this invention are to be determined by the scope of the appended claims.

I claim as my invention:

1. A snap action mechanism comprising in combination, a compression member, a control member, a relatively fixed support, one portion of said compression member engaging said fixed support and another being operatively connected to said control member at a first point, a resilient actuating member connected to a second point on said control member, said second point lying in an area extending between the relatively fixed support and said first point, said actuating member being supported at one side of said control member so that said control member exerts a bending force on said actuating member tending to move said second point across a line connecting the two portions of said compression member, and means for causing said actuating member to move said second point across said line whereby the compression member moves said control member in a direction to increase said bending force resulting in a further movement of said second point independently of said last mentioned means whereby a snap action is produced.

2. A snap action mechanism comprising in combination, a compression member, a control member, a relatively fixed support, one portion of said compression member engaging said fixed support and another being operatively connected to said control member at a first point, a resilient actuating member connected to a second point on said control member, said second point'l'ying in an area extending between the relatively fixed support and said first point,said actuating member being supported at one side of said control member and lying generally along side thereof so that said control member exerts a bending force on said actuating member tending to move said second point across a line connecting the two portions of said compression member, and means for causing said actuating member to move said second point across said line whereby said compression member moves said control member in a direction to increase the angle between said control member and actuating member and thereby increase the bending force, thus producing a snap action.

3. Snap action mechanism comprising in combination, a compression spring reacting at one end against a fixed support, a floating control arm, said compression spring reacting at its other end on said control arm near one end thereof, and a resilient actuating member mounted at one side of and connected to the other end of said control arm at a point lying in an area extending between said fixed support and the said other end of the compression spring, whereby said control arm exerts a bending force on said resilient actuating arm tending to move the said other end of the control arm between the ends of said compression spring.

4. A snap action mechanism comprising in combination, a compression member, a control member, a relatively fixed support, one portion of said compression member engaging said fixed support and another being operatively connected to said control member at a first point, a resilient actuating member connected to a second point on said control member, said second point lying in an area extending between said relatively fixed support and said first point, said actuating member and said point being at one side of a line connecting said two portions of said compression member so that said control member exerts a bending force on said actuating member tending to move it across said line, a first stop, said compression member holding said first point on said control member against said first stop as long as said second point is on said one side of said line, a second stop, and means for causing said actuating member to move said second point across said line whereby said compression member moves said control member in a direction to increase said bending force and hence moves said first point into engagement with said second stop with a snap action.

5. A snap action mechanism comprising in combination, a control member, a relatively fixed support, an elongated spring member reacting at a first point against said support and exerting a substantially longitudinal force on said control member at a second point, a resilient actuating member connected to said control member at a third point in such a manner that said control member exerts a bending force on said actuating member, said third point lying in an area extending between said first and second points whereby the force exerted by said spring member on said control member tends to keep the three points in alignment, and means for causing said actuating member to move said third point laterally with respect to said control member and across a line connecting said first and second points whereby the leverage between said control member and actuating member is changed resulting in said resilient actuating member being bent in the direction of its movement whereby said control member moves with a snap action.

CLAIR F. JOHNSON.

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