US2752446A - Snap switch - Google Patents

Description

June 26, 1956 CARLSON 2,752,446

SNAP SWITCH Filed Oct. 19, 1955 JNVENTOR. JOHN E. CARLSON TORNEYS United States Patent SNAP SWITCH John E. Carlson, West Cheshire, Conn.

Application October 19, 1953, Serial No. 386,730

4 Claims. (Cl. 200-67) This invention relates to snap acting electrical switches, and more particularly to such switches of the type wherein a toggle mechanism is utilized to bring about the switching operation.

In electrical switches, toggle type mechanisms have many advantages in providing compact, simple and rugged structures for performing various actuating movements. Such structures have one serious operational disadvantage, however, when arranged for actuation of the toggle mechanism by a control device whose movement may be slow and deliberate, such as a bellows or a bimetallic element. In such an arrangement, as the toggle arms approach their dead-center position, they are unable to exert more than slight force to move the switch contacts either together, in closing the switch, or apart, in opening the switch. This reduction of force on the contacts renders the contacts likely to are severely just before they are either positively closed or positively moved apart far enough to air-quench the arc. Such arcing is of course a serious operational disadvantage, and is likely to cause pitting and carbonization, with its attendant decrease in the life and utility of the switch.

It is an object of the present invention to provide a snap acting switch which is particularly suitable for operation with a minimum of arcing.

Another object is to provide a snap acting switch in which, during opening of the switch, an even pressure is maintained between the switch contacts up to the last instant before their separation.

Another object is to provide a switching device which is particularly suited to the performance of an abrupt switching operation responsive to displacement to a predetermined position of an actuating member adapted for movement in a slow and deliberate manner.

Other objects will be in part obvious, and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application of which will be indicated in the appended claims.

In the drawing:

Fig. 1 is a plan view of a snap acting switch constructed in accordance with the present invention;

Fig. 2 is a side view of the structure shown in Fig. 1 with the switch contacts in their open position; and

Fig. 3 is a side View of the structure shown in Fig. 1 with the switch contacts in their closed position.

Referring to the drawing, a snap acting switch constructed in accordance with the present invention includes a support 2 having a base 4 and a pair of upstanding parallel spaced posts 6, 8 to which the movable portions of the switch are pivotally connected. The posts may be formed from a single strip of material, bent as shown into a generally U-shape and fastened at its center to the base 4, as by means of rivets 10.

Secured to the support on base 4, and spaced apart from posts 6, 8 is a fixed switch contact 12. Cooperating with fixed switch contact 12 is a movable switch contact 14 which is carried by a movable switch arm 16. The movable switch arm is pivotally supported in V-shaped notches 18 cut in the sides of the upstanding parallel posts 6, 8 and transversely aligned so that switch arm 16 pivots in the plane of the posts and the fixed switch contact 12. The movable switch arm 16 is preferably provided with a square notch at its pivot end so as to form external flanges 20 which prevent transverse movement of the switch arm relative to support 2. On base 4 there is provided an anchor 22 in the form of a pin struck up from the center of the strip forming posts 6, 8, to which is secured one end of a spring 24. The other end of the spring is hooked into an aperture 26 positioned midway along switch arm 16. Spring 24 is a tension spring and serves to bias switch arm 16 resiliently toward fixed switch contact 12. The anchor 22 for spring 24 is aligned with fixed switch contact 12 along what may be considered a reference line, from which the pivot point 28 of switch arm 16, i. e. the apex of notches 18, is perpendicularly or laterally displaced, as shown in Figs. 2 and 3. The relative position of the pivot points or pivot axes of the remaining movable parts will be described in relation to this arbitrary reference line.

A driven toggle arm 30 is pivotally connected to the support 2 by reason of the disposition of its one end in transversely aligned V-shaped notches 32 cut in the same side of the posts 6, 8 as notches 18. The notches 32, however, are disposed laterally further from the reference line between anchor 22 and fixed switch contact 12 than are notches 18.

On the opposite side of the posts 6, 8 from driven toggle arm 30 and switch arm 16 is provided a pair of transversely aligned V-shaped notches 36 in which is pivotally mounted a driving toggle arm 38. The notches 36 are positioned with substantially the same lateral displacement from the reference line as are the notches 32. Thus it may be seen that the driving and driven toggle arms 38, 30 are arranged in substantially end-to-end relation. A tension spring 40 is connected at its ends at points intermediate the length of driven toggle arm 30 and driving toggle arm 38. Thus it may be seen that driving toggle arm 38 and driven toggle arm 30 are related by means of tension spring 40 so as to operate in the manner of the usual toggle mechanism, having a dead-center position in which the two arms are substantially aligned and at which spring 40 is able to exert very little force to pivot the arms, and having extreme positions in which the arms are sufficiently angularly disposed that spring 40 can exert substantial force on them.

Both driven toggle arm 30 and driving toggle arm 38 are provided with square notches at their pivot ends forming external flanges 42, 44 by means of which the arms are secured within the respective notches 32, 36 against transverse displacement. The upper sides of each of the V- shaped notches 18, 32, 36 in posts 6, 8 serve as limit stops on support 2 to define the uppermost position of the toggle arms 30, 38 and the switch arm 16.

At the outer end of driven toggle arm 30 is provided a downward projection 48 which serves as a striker by means of which driven toggle arm 30 engages switch arm 16 and drives it down into a position where the two switch contacts 12, 14 close. This projection 48 is of such a length in relation to the spacing of the outer ends of switch arm 16 and driven toggle arm 30 that there is some lost motion between the two, so that the driven toggle arm 30 is enabled to complete part of its pivotal motion from its uppermost or furthest laterally displaced position, as shown in Fig. 2 of the drawing, toward its lowermost or least laterally displaced position, as shown in Fig. 3 of the drawing, before striker 48 engages switch arm 16. The lateral spacing of the pivot points of driven toggle arm 30 and switch arm 16 is preferably such that driven toggle arm 30 is able to be pivotally moved well past its dead-center position before striker 43 engages switch arm 16. p p j The switch arm 16 is alsoprovided at its outer end with a laterally and backwardly bent portion forming a hook 50 which embraces and confines the outer end of driven toggle arm 30 between its shank portion 52 and its distal end 54. As shown in Fig. 3, the lateral spacing of the distal end 54 of the hook 50 from the point at which striker 43 engages switeh' arm 16 is substantially greater than the lateral dimension of striker 43, so that there is room for substantial lost motion of driven toggle arm 30 between the shank 52 and distal portion 54 of book 50.

In the operation of the device during closing of the switch, there is no engagement of striker and switch arm 16 until driving toggle arm 33 is moved past deadcenter position relative to driven toggle arm so and there is'substantial force exerted by tension spring 49 acting to pull driven toggle arm 30 toward its lowermost position. When this happens, the driven toggle arm 3% moves toward its lowermost position in the positive and abrupt fashion characteristic of toggle mechanisms, and, after the driven toggle arm 30 has moved a substantial part of the distance to its lowermost position, striker 48 engages the outer end of switch arm 16 with a sharp blow and drives the switch arm down so that the switch contacts 12, 14 close abruptly. Thus, switch contacts 12, 14 close without hesitating or faltering, and arcing is kept to a minimum.

During opening of the switch, by reason of the spacing between the distal portion 54 of hook Sit and driven toggle arm 30, and the lost motion it affords, as driving toggle arm 38 is moved past dead center relative to driven toggle arm 30, the driven toggle arm 3t? is moved far enough from its dead-center position that spring 4% is able to exert substantial force before driven toggle arm 30 engages the distal end 54 of hook 5t and exerts any force on the switch arm 16 to open switch contacts 12, 14. Thus, driven toggle arm 30 does not act to open switch contacts 12, 14 against the bias of spring 24, until it has commenced its abrupt forceful toggle motion toward its uppermost position. In this way, as driven toggle arm 30 engages hook 50 of switch arm 16 to open the switch, it does so with considerable force and velocity and produces an abrupt position opening of the switch contacts with a minimum of arcing.

The spring 24 serves in the closed position of switch arm 16 to retain the switch arm in it's closed position until hook 59 is struck smartly by the upward motion of driven toggle arm 39 in traveling toward its uppermost position. This preserves a steady, substantially constant pressure between switch contacts 12, 14 until the very instant when they are abruptly opened. Likewise, spring 24 biases switch arm 16 toward fixed switch contact 12 while the switch arm is held in its uppermost position by the driven toggle arm 30, and in this way insures that switch arm 16 will move smartly toward its closed switch position as soon as the driven toggle arm permits such movement.

Thus, it may be seen that driven toggle arm 30 serves in a manner analogous to that of a pilot member which, though not directly actuating the switch, moves in a positive and abrupt manner to either close or open the switch smartly responsive to the arrival of driving toggle arm 38 at predetermined positions relative to the support. With a switch constructed and arranged in the manner above described, it may be appreciated that the driving toggle arm 33 is particularly suited for actuation in a slow progressive manner by external elements such as bellows, bimetallic elements, or the like, since, even though the driving toggle arm may approach its predetermined switching position very slowly and deliberately, therarrangement of the parts is such that no switching action will take place until the driving toggle arm arrives at its exact predetermined position, and then the resulting switching action will be forceful and abrupt to insure a minimum of arcing.

As many changes could be made in the above con struction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

I claim:

1. In a two-position snap-acting switch, a support having a fixed switch contact, a driving toggle arm pivoted to said support at a first point laterally displaced from a reference line through said fixed switch contact, a driven toggle arm pivoted to said support in end-to-end relation with said driving toggle arm, a first tension spring connected between said driving and driven toggle arms, a rigid switch arm pivoted to said support at a second point laterally disposed between said first point and said reference line and carrying a movable switch contact for engaging said fixed switch contact, a second spring biasing said switch arm toward said fixed switch contact, a striker on said driven toggle arm for engaging said switch arm after said toggle arms pass dead center in moving toward said reference line to snap. said switch contacts closed, and a projection on said switch arm disposed for engagement by said driven toggle arm after said toggle arms pass dead'center in moving away from said reference line to snap said switch contacts open, said projection having a lateral spacing from the point of engagement of said strike with said driven toggle arm equal to a substantial portion of the throw of said driven arm.

2. In a two-position snap-acting switch, a support having a fixed switch contact and an anchor, a driven arm pivoted to said support at a first point laterally displaced from a reference line between said fixed switch contact and said anchor, a driving arm pivoted to said support in end-to-end relation with said driven arm at a point laterally adjacent said first point, a first tension spring connected between said driven and driving arms at points intermediate their lengths to form a toggle, a rigid switch arm pivoted to said support at a third point laterally disposed between said first point and said reference line and carrying a movable switch contact for engaging said fixed switch contact, a striker on said driven arm for engaging said switch arm after said driven arm passes dead center in moving toward said reference line, a hook on said switch arm loosely encircling said driven arm for engagement thereby to pull said switch arm open after said driven arm passes dead center in moving away from said reference line, said hook having a lateral spacing between its shank and distal ends equal to a substantial portion of the throw of said driven toggle arm, and a second tension spring connected between said anchor and an intermediate point on said switch arm.

3; In a two-position snap-acting switch, a support having a fixed switch contact and an anchor, a driven arm pivoted to said support at a first point laterally displaced from a reference line between said fixed switch contact and said anchor, a driving arm pivoted to said support in end-to-en'd relation with said driven arm at a point laterally adjacent said first point, a first tension spring connected between said driven and driving arms at points intermediate their lengths to form a toggle, a rigid switch arm pivoted to said support at a third point laterally disposed between said first point and said reference line and carrying a movable switch contact for engaging said fixed switch contact, a striker on said driven arm for engaging said switch arm at a position of said driven arm between dead center and said reference line, a hook on said switch arm adapted to be engaged by said driven arm in a position on the opposite side of dead center from said reference line, said hook having a lateral spacing between its shank and distal ends equal to a substantial portion of the throw of said driven toggle arm, and a second tension spring connected between said anchor and a point on said switch arm.

4. In a two-position snap-acting switch, a support having a pair of spaced parallel arms and a fixed switch contact spaced from said arms, a driving toggle arm pivoted to one side of said arms at a first axis laterally displaced from a reference line between said fixed switch contact and one end of said arms, a rigid switch arm pivoted to said support at a second axis laterally disposed between said first axis and said reference line and carrying a movable switch contact for engaging said fixed switch contact, said switch arm being bent back at its outer end to form an inturned hook, a driven toggle arm pivoted at one end to the other side of said parallel arms in end-to-end relation with said driving toggle arm and having its other end disposed between the shank and distal portion of said hook for movement therebetween with lost motion, said hook having a lateral spacing between its shank and distal ends equal to a substantial portion of the throw of said driven toggle arm, a tension spring connected between said driving and driven toggle arms at points intermediate their length, and a tension spring connected between said switch arm and a point on said support substantially aligned with the switch arm in its open switch position, whereby said driven toggle arm engages said distal portion and snaps said switch contacts open when toggled past dead center away from said fixed switch contact and said driven toggle arm engages said shank portion and snaps said switch contacts closed when toggled past dead center toward said fixed switch contact.

References Cited in the file of this patent UNITED STATES PATENTS 2,328,154 Lennholm Aug. 3], 1943 2,666,108 Brown Jan. 12, 195- FOREIGN PATENTS 206,944 Great Britain Nov. 22, 1923

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