US2729714A - Double snap action switch - Google Patents

Description

Jan. 3, 1956 v F. J. BROCH ,7

DOUBLE SNAP ACTION SWITCH Filed Oct. 21, 1950 4 Sheets-Sheet 1 gg K fa 61w 15L.

Jan. 3, 1956 F. J. BROCH DOUBLE SNAP ACTION SWITCH 4 Sheets-Sheet 2 Filed Oct. 21, 1950 frzvenia 7 1:20? Jfiroa/Tv/ wwnyw Jan. 3, 1956 F. J. BROCH 2,729,714

DOUBLE SNAP ACTION SWITCH Filed Oct. 21, 1950 4 Sheets-Sheet 4 United States Patent DOUBLE SNAP ACTION SWITCH Frederick J. Broch, Cambridge, Mass.

Application October 21, 1950, Serial No. 191,447

13 Claims. (Cl. 200-67) This invention relates to snap action mechanisms such as are used to actuate electrical contacts, valves, and other similar off and on devices.

When such devices are operated by the usual single snap action mechanism, the contacts or valves are subject to arcing or chattering as the mechanism passes through its dead center position unless friction is introduced to delay the operation until sufiicient energy or force is built up to insure a rapid transfer through the dead center position. As the friction varies with aging, corrosion, and change in elasticity, the reliability of such mechanisms is uncertain particularly when operated by a slow moving actuator such as a pressure bellows or temperature responsive bimetallic strip.

It is accordingly the principal objects of this invention to provide a snap action mechanism which will actuate an associated device, which will operate positively at any actuating rate, which is not aiiected by vibration, which requires a small actuating force, which operates equally well in both directions, which is light in weight, which is small in size, and which advances the art generally.

A snap switch according to the invention comprises a contact carrying arm pivotally or otherwise operatively attached to a supporting base so that the movable contact carried by the arm selectively makes with one or more stationary contacts carried by the base. Two members, preferably flexible, are interconnected at their free ends, either integrally or by means of a hinged or pivoted joint, the opposite ends of the members being operatively attached, for example by a suitable movable joint, to points upon the contact carrying arm and base respectively thereby to form a snap action. The points of attachment are relatively located so that the force exerted either by a separate spring or because of the inherent resiliency of the members stresses the members in tension and compression respectively in one state of equilibrium of the snap action. The resulting movement upon the contact carrying arm normally maintains the movable contact in a fixed relation with respect to the stationary contacts during such state of equilibrium. An actuator is provided for relatively moving the members so that the eifective line of action of the member under tension coincides with the effective line of action of the member under compression thereby causing the snap action to pass through its dead center point with an abrupt snap movement of the interconnected ends of the members. The point of attachment of the end of the corresponding member to the contact carrying arm is relatively positioned to reverse the movement upon the arm thereby to transfer the movable contact.

These and other objects, aspects and features will be apparent from the following description of an illustrative specific embodiment of the invention referring to drawings in which Fig. 1 is a schematic diagram of a double snap action movement incorporating a compression'spring;

Fig. 1a is a schematic diagram of a modification of the movement in Fig. 1;

Fig. 2 is a schematic diagram of a second type of double snap action movement incorporating a tension spring;

Fig. 3 is a view in partial section of a mechanism incorporating the snap action movement shown in Fig. 2;

Fig. 4 is a sectional view on line 4-4 of Fig. 3;

Fig. 5 is a schematic diagram of a third type of double snap action movement incorporating a leaf spring showing the positions assumed by the various elements as the movement is actuated;

Fig. 6 is a view similar to that shown in Fig. 5 showing the positions assumed by the various elements as the movement is returned;

Fig. 7 is a plan view of an embodiment of a double snap action electrical switch incorporating the movement illustrated in Figs. 5 and 6;

Fig. 8 is an elevation view in partial section of the switch shown in Fig. 7;

Fig. 9 is a plan view of another embodiment of a double snap action switch having a counterweighted contact carrying arm;

Fig. 10 is an elevation view in partial section of the switch shown in Fig. 9;

Fig. ll is a plan view of a further embodiment of a double snap action switch incorporating a tension spring; and

Fig. 12 is an elevation view in partial section of the switch shown in Fig. 11.

The first embodiment of the invention chosen for the purpose of diagrammatic illustration comprises an arm 1 which is pivoted at one end at point 0 as is shown in Fig. 1, the opposite end being biased against a stop S1 by means of an elastic member such as the helical compression spring 3 hingedly connected at P to the free or lower end of arm 1. The arm 1 and the spring 3 comprise the elements of a primary snap action movement which is tripped by means of an actuator which exerts a force represented by the arrow F. The actuator F may be any one of the well known suitable devices operated mechanically, electrically, thermally, hydraulically or otherwise for applying a component of a force to the arm 1 which results in a turning movement about the pivot point 0 so that the common connecting point P between the arm 1 and the spring 3 follows an arcuate path of travel A. As the point P moves along the path A, the spring 3 is compressed until the point P1 is reached, the actuator F supplying the energy required for this compression. The point P1 lies in the line C passing through the arm pivot point 0 and a point R at the lower end of the spring 3 which bears against a stop C1. The line of action of the spring 3 coincides with a line C extending from the point P1 to the pivot point 0, this being the critical or dead center position of the primary movement. When the actuator F moves the arm 1 a differential distance beyond the line C, a component of the spring force is developed tangent to the path A so that the arm 1 is rotated about point 0 by the spring force component until the point P has moved along the remainder of the path A until it reaches the fixed stop S2 and comes to rest at P2. As the energy for completing the movement of the arm 1 beyond the line C is obtained from the expansion of the spring 3 rather than from the actuator F, such movement is trip free.

During its trip free travel the arm 1 of the primary movement trips a secondary movement comprising an arm 2 (one end of which is pivoted at O), and the spring 3 which is common to both movements, the spring and the free or upper end of arm 2 being hingedly connected at the point R which moves along an arcuate path A' about the center The tripping of the second movement occurs when the free lower end of the arm 1 reaches the point P3 which is a head center position of the secondary movement where the line of action of the spring 3 coincides with the axis 0 of the arm 2 so that a differential move ment of the free lower end of arm 1 beyond P3 results in a spring force component tangent to the path of the point R which transfers the free upper end of arm 2 to the position 2 against the stop C2. The return action is symmetrical, the same or a different actuator applying force F to move the arm 1 in a counterclockwise direction until the end i again rests against the stop Si, the primary movement passing with a trip free movement through a second dead center position (not illustrated} located upon the opposite side of the center line T from its above mentioned first dead center position, the movement being tripped during such trip free movement in a manner analogous to that described in detail above.

A modification of the above-described embodiment is shown in Fig. la wherein the pivot points 0 and O are both located upon the same side of the spring 3 rather than upon opposite sides thereof as is the case of the first embodiment illustrated in Fig. 1.

In the second embodiment of the invention shown in Fig. 2, a tension spring 3a is the elastic member employed to interconnect the respective ends of the arms in and 2:; whose opposite ends are pivotally attached at the points 0a and 6's respectively. The travel of the end Pa of the arm 1a at which the spring 3a is connected, is limited by stops Sid and S211. 2, connected to the opposite end of the spring 3a, is limited by the stops Clo and C201. The device is tripped by means of a component of force Fa, exerted by an actuator (not shown), to move the point he along the arcuate path Art to the dead center position Pla of the primary movement where the line of action of the spring 3:: and the axis of the arm 1a coincide, the energy for the remaining travel of the arm in to the stop 32a being supplied by the spring so that the travel is trip free.

As the arm end Pa passes beyond the point F351, at the dead center position of the secondary movement where the line of action of the spring 3a coincides with the axis of the arm 2a, the spring force has a component tangent to the arcuate path of the arm end Ra which moves the arm 2a. until it rests against the stop C'Z a. The return action of the movement is symmetrical, the primary movement after passing a second dead center position upon the opposite side of the center line Ta from its first dead center position, trips the secondary movement in a manner analogous to that described above.

If the stops C1 and C2 (or Cla or CZa) are made stationary electrical contacts and the arm 2.- (or 2a) carries a correlated movable contact, it will be evident that the rate of movement or vibration of the actuator will have no effect upon the contacts moved by the secondary movement which is tripped after the primary movement is in a trip free condition beyond the control of the actuator thus eliminating the burning and arcing of the contacts encountered in conventional switches because of reduction of contact pressure at the dead center position.

The above-described principle of operation of the movement illustrated in Fig. 2 is utilized in the switch embodiment shown in Figs. 3 and 4- wherein the various analogous elements and positions bear the same indicia as in Fig. 2. This embodiment comprises a hollow, generally rectangular base 1 having an open top and two opposed side walls which are provided with aligned circular recesses or grooves which accommodate corresponding circular ends of a hollow actuator Fa having the general shape of a truncated pyramid. A U-shaped member 12 of a conducting material is fastened by its crosspiece to the bottom of the base 10 so that the legs of the, member extend up into the hollow actuator thereby to provide a support for the pivots 0a and Oa of the arms in and 2a,

The travel of the end Ra of the arm respectively. The arms 1a and 2a are shaped similarly to double cranks with their crankpins deformed as is shown in Fig. 4 to provide seats for securing the respective ends of the spring 3a. The opposite ends of the shaft of the crank arm 1a are journaled respectively in aligned apertures near the top of the opposed legs of the member 12, the axis of the shaft forming the pivot point 0a. The ends of the shaft of the crank arm 2a are likewise journaled in aligned apertures in the supporting member 12, the shaft axis forming the pivot O'a. The ends of the shaft of crank arm 2a are extended through the support legs 12 into the adjacent side walls of the actuator Fa thereby to provide a pivot about which the actuator can be moved.

The above-described switch is tripped by rotating the actuator Fa about the pivot Oa so that the inner wall Sin thereof bears against the crank portion of the arm in to move it beyond the dead center position Pla whereupon the arm moves until it contacts the opposite inner wall S211 of the actuator Fa which acts as a stop, such movement being trip free as described in detail in connection with the embodiment shown in Fig. 2. The arm 2a remains against a stop Cia, Which is also an electrical contact, until the arm in passes through the dead center position Pile: of the secondary movement whereupon the arm 21; moves into contact with its other contact stop C251. The movement of the actuator Pa in the opposite direction returns the arms to their original position, the sequence of operations being similar to that described above with respect to the first operation of the switch.

in Figs. 5 and 6 is schematically shown a further double snap action movement wherein the primary movement comprises a non-rigid link 3 one end of which is pivotally attached at 36 to a supporting base (not shown) or other relatively stationary point. The opposite end of the link 3d is joined to one end of a compression spring member whose line of action is represented by the line 26, the common end point of the link and spring being designated 28. The secondary movement includes a substantially rigid contact carrying arm 29 which is pivoted at one end at the relatively fixed point 22. The arm 2i) is biased at one limit of its travel in its normal position shown in full lines against the lower contact 24 by means of the compression spring member 26 whose opposite end is pivotally connected at a point 3% upon the contact carrying arm Zil intermediate its ends.

The upward movement of the joined end 28 at the opposite end of the spring member is limited by a stop 32. The horizontal movement to the left of the joined end point 23 along the face of the stop 32 is limited by the non-rigid link 34, one end of which is pivotally connected at the relatively stationary point 36 as described above. As the opposite end of the non-rigid link 34 is attached to the end of the spring member 26 at 28, the link is under a tension stress which holds the spring member in compression. The downward component of the spring force, exerted by the spring member upon the point 30, acts through a lever arm, equal in length to the portion of the arm 20 between the points 2230, thereby to bias the end of the arm 25? against the normally closed contact 24 as mentioned above. It will be noted that the contact force between the arm 20 and the contact 24 would be increased by raising the position of the stop 32 relatively to the fixed pivotal point 22 thereby to increase the downward force component.

The switch is operated by means of an actuator 38 which bears against an intermediate point of the link 34. As the link is non-rigid and pivotally secured at point 36, the movement of actuator 38 to the position 38' deforms the link so that it now has the configuration indicated by the broken line designed 34'. As the overall length of the link 34 remains constant, the common end point 28 slides horizontally, to the right, along the face of the stop 32 until the point 28' is reached.

As the actuator 38 is depressed further, the sliding horizontal movement of the point 28 and the accompanying increase in compression of the spring member continues until a point 28" corresponding to an actuator position 38" is reached. It will be noted that in this position 38", the actuator deforms the link 34 to the position designated 34 where the portion of the link to the left of actuator position 38 coincides with the line of action 26 of the spring member. or dead center position of the primary movement. A subsequent further differential movement of the actuator to a point below the point 38 moves the part of the link 34 which is to the left of the point 38" below the line of action of the spring member 26 so that there is nowadownward component of the force exerted by said spring member at the point 26". This downward force component is unopposed so that the part of the link 34 which is to the left of the point 38" pivots about the final point of application of the actuating force and the spring member 26 pivots about the point 30. In this connection it will be noted that an are, such as is indicated by the dotted line 28b having a radius 28"30, equal in length to the compressed length of the spring member when the actuator is at its lowest point, lies within an arc 28a traced by the pivotal movement of the point 28" about the point which represents the lowest position of the actuator so that the spring member expands during this movement. This expansion of the spring member supplies energy so that the point 28" moves until it reaches 28t against the face of a lower stop 40 without further action on the part of the actuator 38.

As the line of action 26 of the spring member passes the line 26d (Fig. which passes through the points 22 and 30 on the arm 20, the torque exerted on the arm by the spring member is reversed, i. e., this is a first dead center position of the secondary movement so that a further differential movement of the line of action 26 of the spring member pivots the arm about the point 22 to the position designated 20" wherein its contact end rests against a stationary contact 44 and the intermediate pivotal point 30 moves to 30". This movement of the end of the spring member to the point 30" shifts the line of action of the spring member so that the component of spring force tangent to the arc 28a is increased thus aiding the movement of the joined end of the link and spring member to the point 281. The movement of the point 30 to 30" also permits the spring member to expand, thus supplying energy for operation of the secondary movement. The line of action of the spring memher after the above-described movement and expansion assumes the position designated 26" (Fig. 6). It will be evident from the above that the component of the force of the spring member forcing the arm 20 against the contact 44 would be increased if the stop 40 were lowered.

The arm 20 is returned by the spring to its normal position wherein it makes with the contact 24 upon release of the actuator 38, by reason of the fact that the pivot point 36 is spaced above the line 22-30. As the force exerted by the actuator 38 is removed from the link 34, the portion of the link between the actuator and the end 28 straightens out, taking the position designated 341-, so that the common end 28 moves along the face of the stop 40 from the point 28t to the point 28! which results in a decrease in the force exerted against the contact 44.

In the position Mr that portion of the link which lies between the actuator and the end 28 coincides with the line of action of the spring member 26 which is the second dead center position of the primary movement, but at this time the link is not yet straight but from the actuator to the point 36 is inclined more steeply than to the left of the actuator thus holding the spring under abnormal stress. Since the actuator is free to rise, the spring force tends to straighten the link, causing further upward movement of the actuator which results in an upward component of spring force which, being unopposed, moves This position is the first critical 8 the joined end to the point 28" along the arc 28c, whose center of curvature is the actuator point 38" until the point 28" upon the face of the stop 32 is reached. Dur ing this movement of the point 28"): along the arc 28c, the spring member expands by an amount indicated by the distance between this are and an are represented by the dotted line 28d which is the locus which would be traced if the end of the spring member were rotated about the point 30" without expanding. This expansion of the spring member provides energy for moving the common end 28.

As the dead center position 26'd of the secondary movement is reached, the component of the spring force upon the arm 20 is reversed, returning the arm to its original position in which it makes with the contact 24. The end of the spring member conjointly moves from 30" to 30 and shifts the line of action of the spring member so that the component of spring force tangent to the arc 28c is increased, thus aiding the movement of the joined end of the link and spring member to the point 28'. The movement of the point 30" to 30 also permits the spring member to expand, thus supplying the energy for the operation of the secondary movement.

In Figs. 7 and 8 is shown a first practical embodiment of a double snap action switch which operates according to the principles described in detail above in connection with the schematic diagrams shown in Figs. 5 and 6. Accordingly the various components of the switch are numbered to correspond with the lines and points of the diagrams in Figs. 5 and 6 which have generally similar functions. This switch comprises a base 50 molded or otherwise formed of a nonconducting material such as a suitable plastic. The lower, normally closed stationary contact 24' is carried upon the upper end of a conducting insert 24a whose lower end is molded into the base 50. The lower end of the base has an aperture with internal threads for engaging a screw 24b for electrically connecting the contact to the lead (not shown) from an external circuit. The upper contact 44 is carried upon the lower side of one end of a bridge member 44a whose opposite end is secured to the top of an insert 44b by means of a screw 44c. The bottom of the insert 44b is molded in the base 50 and provided with a threaded aperture for a connecting screw similar to the screw 24b in the insert 24a described above.

A movable contact 200 for selectively making with the stationary contacts 24 or 44 is carried upon the end of a substantially rigid arm 20 of a conducting material such as bronze or magnesium. The opposite end of the arm 20 is forked and the ends of the resulting tines are notched to engage respectively circumferential grooves in two pins 22 which are secured in inserts 22a molded in the opposite end of the boss 20 from the end at which the contacts are mounted so that the pins form a pivot about which the arm moves to make with the stationary contacts. One or both of the inserts 22a are provided with an internally threaded aperture to receive a screw 22b for connecting to the lead (not shown) of an external circuit.

Re-enforcing strip 20a is welded or otherwise fastened to the bottom of the respective tines of the arm 20 thereby to form two steps 30 against which bear the ends of the compression spring members 26. The opposite ends of the spring members 26 are formed integrally with one end of link 34 as at the common joined end 28. The opposite end of the link 34' has an aperture which engages a circumferential groove under the head of a screw member 36 maintaining the spring members 26 under compression so that the arm 20 is biased against the lower contact 24. The travel of the joined end 28 of the link 34 and the spring members 26 is limited to the screws 32 and 4% which engage threaded apertures in the base 50.

The switch is tripped by the conical shaped end of an actuator 38 whose shaft is guided in an aperture in a cover 55 for the base 50. The apex of the actuator 38 depresses the link 34 until the axis thereof coincides with the line of action of the spring members 26 at the first dead center position of the primary movement whereupon the joined end 28 travels the remaining distance to the stop 40. As the joined end 28 passes through the first dead center of the secondary movement, the contacts transfer so that the movable contact 20c makes with the normally open stationary contact 44. Upon the releasing of the actuator 38, until it returns to a second dead center position of the primary movement where the axis of the link 34 coincides with the line of action of the spring members 26, the joined end 28 returns so that it again is in contact with the under side of the head of the screw 32. During the return travel of the joined end 28, the line of action of the spring members 26 passes through the second dead center of the secondary member so that the arm 20 returns the contact 200 to the normal position against contact 24.

The switch shown in Figs. 9 and is generally similar and operates upon the same principles as the switch described in detail immediately above with the exception of its counterweighted contact arm 120 which is rigidly formed from one piece of metal. The arm 120 is provided with two knife edges 122a which engage corresponding V-notches in ears 122 which are bent up from a supporting plate 1232b. The plate 12212 is secured to the base by means of a flat headed screw 1220 of relatively great diameter which is provided with a threaded axial hole for a screw 122d for connecting a lead (not shown) from an external circuit to energize the movable contact 200 carried upon the end of the arm. The opposite end of the arm 12%) is extended beyond the knife edges 122a to support two counterweights 122e and 122 made, for example, of lead so that the arm is statically balanced about its pivot points. The weights 122a and 122 are fastened to the end of the arm 129 by means of two screws 122g, the base 150 and cover 155 being modified so that they do not interfere therewith. The remaining switch elements are similar in construction and bear the same indicia as the corresponding elements in the embodiment of the switch shown in Figs. 7 and 8 and described in detail heretofore.

A further embodiment of the invention, wherein the compression spring members 26 are replaced by two rigid members 126 and the compression stress is introduced by means of a helically wound tension spring 134, is shown in Figs. 11 and 12. One end of the spring 134 is secured against a knife edge forming one wall of a small aperture in the center of the joined ends 128 of the members 126. The opposite end of the spring 134 is similarly secured in an aperture near one end of a comparatively rigid link 134a. The opposite end of the link 134a is provided with a second aperture whose wall engages a circumferential groove in a screw 136. The contact carrying arm 20 is generally similar to the arm 26 shown in Figs. 7 and 8 and described heretofore, but is provided with a greater ofifset and modified pivotal connections 130 with the ends of the compression members 126 respectively. The remaining elements are similar in construction and bear similar indicia to the corresponding elements in the two embodiments described in detail above.

It will be evident that in the normal position of the switch, as indicated by the solid lines in Fig. 12, the tension in the spring 134 causes a force to act upon the points 130 of the arm 2i) which is the equivalent to force exerted by the spring members 26 upon points 36 of the arms in the previously described embodiments so that the movable contact 205 is biased against the lower stationary contact 24. As the actuator 38 is depressed, it contacts the link 134a which pivots about the screw 136. As the link 134:: is substantially rigid, the end connecting with the spring 134 is moved downwardly until the line of action of the spring coincides with the axis of the members 126 which is the first dead center position of the primary movement.

it should be noted that the link 134a acts as a lever so that the required movement of the actuator 38 is reduced.

Upon reaching the above mentioned dead center position, the primary movement moves to the position shown in broken lines with the joined end 128 resting upon an abutment of the base 50a which acts as a stop. The downward movement of the link 134a is arrested by by means of a stop such as the screw 140a. During this movement the arm 20 is moved so that the contact 200 is transferred to make with the upper stationary contact 44 in a manner similar to that which has been described in detail in connection with previous embodiments.

Upon the release of the actuator 38, the spring 134 moves upwardly until its line of action coincides with the axis of the members 126 whereupon the spring and link return to their original position, the arm 20 returning during this trip free movement so that the contacts 200 and 24 again make.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. A snap action switch comprising an elongate base, means adjacent to one end of the base for supporting at least one fixed electrical contact, a substantially rigid contact carrying arm extending longitudinally of the base, fixed means adjacent to the opposite end of the base defining a horizontal pivotal axis for the contact carrying arm, said arm having a contact adjacent to its free end which is arranged selectively to make with the fixed contact, two elongate elements extending longitudinally of the base, those ends of said elements which are nearer to the fixed contact being joined together, one of said elongate elements being normally in tension and the other in compression, means anchoring that end of the tensioned element, which is nearer to the pivot means for the contact carrying arm, to the base, the corresponding end of the compression element engaging the contact carrying arm at a point intermediate the ends of said arm and normally exerting force against the contact carrying arm in a direction to keep the movable contact in engagement with the fixed contact, means for limiting motion of the joined ends of the tension and compression elements, and actuating means for applying force to the tension element, at a point nearer to the anchored end of said element than to its other end, so as to decrease the effective length of the tension element and thereby shift the effective line of action of the tension element until said line of action first coincides with and then passes the normal line of action of the compression element, thereby causing an abrupt snap motion of the joined ends of said elements and a shift in the line of action of the compression element such that the latter now exerts force on the contact carrying arm in a direction opposite to the force applied by the actuating means thereby carrying the movable contact away from the fixed contact.

2. A snap action switch according to claim 1, wherein the fixed contact is located wholly to one side of the longitudinal center line of the base, one end of the contact carrying arm being bifurcated to provide spaced parallel legs disposed symmetrically at opposite sides of the longitudinal center line of the base, each leg terminating at one end in a horizontal knife edge, said edges being aligned and engaging the pivot means carried by the base, the free end portion of the contact carrying arm on which the movable contact is mounted being unsymmetrical in plan and comprising a portion which overhangs the fixed contact and on which the movable contact is mounted.

3. A snap action switch according to claim 2, wherein each leg of the contact carrying arm has a step spaced from the knife edge, the compression element having two parallel elongate members joined together at one end to one end of the tension element, the latter being interposed between said parallel members, the free ends of said parallel members of the compression element seating against the steps of the corresponding legs of the contact carrying arm, and means fixedly anchoring the other end of the tension element to the base.

4. A snap action switch comprising an elongate base of insulating material, means near one end of the base supporting vertically spaced upper and lower contacts, a substantially rigid contact carrying arm extending longitudinally of the base, means defining a horizontal pivotal axis for one end of said arm adjacent to the other end of the base, a movable contact mounted on the other end of said arm and interposed between the stationary contacts, two elongate flexible elements extending lengthwise of the base, one being in tension and the other in compression, those ends of said elongate flexible elements which are nearer to the fixed contacts being joined together, the opposite end of the tensioned element being anchored to the base adjacent to the fulcrum means for the contact carrying arm, the corresponding end of the compression element engaging a step carried by the contact carrying arm at a point intermediate the ends of said arm and normally exerting force on said arm in a direction to keep the movable contact engaged with one of said fixed contacts, said arm and flexible elements constituting a snap action mechanism having two states of equilibrium, actuating means for applying deflecting force to one of said elongate flexible elements thereby to shift the effective line of action of the tensioned element until said line first coincides with and then passes the normal line of action. of the compression element thereby causing an abrupt snap movement of the joined ends of said elongate elements and a shift in the line of action of the compression element such that the contact carrying arm is moved to engage the movable contact with the other fixed contact, and means for determining the contact pressure between the movable and the respective fixed contacts comprising two independently adjustable stops.

5. A snap actionswitch of the kind wherein an elongate rigid insulating base is provided near one end with means supporting upper and lower vertically spaced fixed contacts, a movable contact engageable alternatively with the respective fixed contacts, and a rigid lever of conducting material on one end of which the movable contact is mounted, means carried by the base adjacent to the opposite end of the base and which defines a fixed horizontal pivotal axis for the opposite end of the contact carrying lever, an elongate tension element, a portion at least of whose length is flexible, means anchoring one end of said tension element to the base adjacent to said pivotal axis, a compression spring element joined at one end to the other end of the tension element, means limiting motion of the joined ends of said elements upwardly and downwardly, the opposite end of the compression spring element seating against a step carried by said lever at a point intermediate the ends of the latter, the step facing toward that end of the base at which the fixed contacts are located, the parts being so arranged that the compres sion spring element normally exerts a component of force such as to urge the movable contact toward the lower fixed contact, a movable actuator which engages the tension element at a point intermediate the anchored end of the latter and the point where the tension and compression spring elements are joined, saidactuator constituting means whereby downward force may be exerted transversely of the tension element to cause portions of the latter to lie in planes which intersect to form an obtuse angle Whose apex is directed downwardly and so positioned relatively to the horizontal plane of said pivotal axis as to cause a shift in the direction of the force exerted by the compression spring element thereby moving the movable contact toward the upper fixed contact.

6. A snap action switch according to claim 5, wherein the pivotal axis for the contact carrying lever is in a horizontal plane which is below the lower of the fixed contacts.

7. A snap action switch according to claim 5, wherein the anchored end of the tension element is at a point above the horizontal plane of the pivotal axis for the contact carrying lever.

8. A snap action switch according to claim 5, having means for relatively varying the vertical distance between the point of anchorage of the tension element to the base and the horizontal plane of the pivotal axis of the contact carrying lever.

9. A snap action switch according to claim 5, further characterized in that the tension element is transversely flexible throughout substantially its entire length but normally substantially rectilinear from its anchorage point to its junction with the compression spring element.

10. A snap action switch according to claim 5, wherein the means for limiting upward and downward movement of the point at which the compression and tension elements are joined comprises independent elements disposed at opposite sides of the horizontal plane of the pivotal axis of the contact carrying lever. 1

11. A snap action switch according to claim 5, wherein the means for limiting motion of the point of junction of the tension and compression spring elements consists of two screws, having threaded engagement with the base, the junction point of the tension and compression elements being interposed between the head of one screw and the tip of the other screw.

12. A snap action switch according to claim 5, comprising means operative statically to balance the contact carrying lever about its pivotal axis.

13. A snap action switch according to claim 5, wherein the contact carrying lever is provided with a bracket extending to the opposite side of the pivotal axis, and a counterweight carried by said bracket operative statically to balance the contact carrying lever about said axis.

References Cited in the file of this patent UNITED STATES PATENTS Re. 17,646 Johnson Apr. 22, 1930 1,910,510 Warner May 23, 1933 2,144,120 Parks Jan. 17, 1939 2,228,523 Johnson Jan. 14, 1941 2,459,661 MacFarland Jan. 18, 1949 2,476,045 Kaminky July 12, 1949 2,508,040 Ransome May 16, 1950 2,510,021 Kaminky May 30, 1950 2,566,534 Reger Sept. 4, 1951 2,589,563 Miller Mar. 18, 1952 FOREIGN PATENTS 965,336 France Sept. 8, 1950

Images