US 3319022 A
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May 9, 1967 w. FRoYD ETAL 3,319,022
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Patented May 9, 1967 3,319,022 SNAP SWITCH HAVING AN INTEGRAL OVER- CENTER SNAP SPRING BLADE Lawrence Wilbur Froyd and Jerry Willard Washburne, both of Princeton, Ind., assignors to American Machine & Foundry Company, a corporation of New Jersey Filed May 4, 1966, Ser. No. 547,601 7 Claims. (Cl. 261B-67) This invention relates to electrical snap switches and moe particularly to switches which combine a wiping contact movement with a true snap action.
Though prior art workers have provided snap acting switches of various types, there has heretofore been a continuing need for a snap switch capable of satisfactory operation and long operational life when handling relatively heavy currents of, for example, 20-25 amp. When used with such relatively heavy currents, conventional snap switches, and particularly those depending upon an over-center spring device for snap action, have been subject to excessive sticking or Welding of the contacts. Though numerous efforts have been made in the past to solve this problem by providing a Contact wiping action during operation of the switch, and by employing special contacts, none of the prior lart switches capable of being inexpensively manufactured have been truly satisfactory under relatively heavy current conditions.
It is accordingly a general object of this invention to provide a snap switch which exhibits a long operating life when switching relatively heavy currents.
Another object is to devise such a switch employing ya simple over-center spring device.
A further object is to provide a snap switch which combines a good contact wiping action, preparatory to contact separation, with a true snap action free from the tease or dead break actions, which have frequently characterized such devices.
In order that the manner in which these and other objects are achieved in accordance with the invention can be understood in detail, particularly ladvantageous embodiments thereof will be described with reference to the accompanying drawings, which form a part of this specication, and wherein: i
FIG. l is a longitudinal sectional view of a switch constructed in accordance with one embodiment of the invention, showing movable parts of the switch in their normal positions;
FIGS. 1A, 1B land 1C are fragmentary side elevational views showing successive -contact positions for the switch of FIG. 1;
FIG. 2 is a top plan view of the switch of FIG. l with the cover removed;
FIG. 3 is a side elevational view of the switch of FIG. l, with portions of the housing broken away for clarity, showing the movable parts of the switch in their actuated positions;
FIG. 4 is an enlarged fragmentary sectional View taken on line 4 4, FIG. 2;
FIG. 5 is an enlarged perspective view of a fulcrum member forming a part of the switch of FIG. 1;
FIG. 6 is an enlarged perspective View of a lever forming a part of the switch of FIG. l;
FIG. 7 is a perspective view of a spring blade and movable contact unit employed in the switch of FIG. 1;
FIG. 8 is Ia side elevational view, with portions broken away for clarity and with the cover removed, of a switch constructed in accordance with another embodiment of the invention; and 1 FIG. 9 is a fragmentary perspective view of the lever and fulcrum member employed in the switch of FIG. 8.
Turning now to the drawings in detail, and first to FIGS. 1-7, this embodiment of the invention comprises thin spring sheet metal.
a unitary base member 1 land a cooperating cover 2, both being rigid and of electrical insulating material. A first fixed contact member 3 is secured to base 1 by a suit-able combined fastener and terminal 4, which can comprise a hollow rivet threaded at one end to receive a screw for securing the conductor to be connected to the contact in use. A second fixed contact member 5 is secured to base 1 by combined fastener and terminal 6. Contact member 3 includes a metal strip extending along the top of base 1 and terminating in an end portion to which is welded a contact button presenting -a contact surface facing away from the base. Contact member 5 is secured to the tip of a boss 7 on base 1 and comprises a metal strip which projects from the boss to a position spaced above the contact surface presented by member 3. At its free end, member 5 carries a contact button presenting Aa contact surface directed toward the base in such fashion as to be spaced from and opposed to the contact surface presented by member 3.
The switch employs an over-center snap spring device comprising a fulcrum member 8, FIG. 5, a rigid operating lever 9, FIGS. 4 and 6, and a spring blade 10, FIG. 7. Member 8 is a rigid metal piece including a mounting leg 11 having an aperture 12, and a fulcrum leg 13 which projects from the mounting leg at right angles. Leg 13 has a pair of identical transversely aligned outwardly opening `rect-angular notches 14, 15. Lever 9 includes a flat elongated body portion 16, a transverse end ange 17 projecting at right angles to the plane of body portion 16, and, -at the end of the lever opposite ange 17, a fulcrum end portion including a centrally disposed shoulder 18 and two longitudinally extending projections 19 and 20 spaced apart transversely of the lever and disposed each at a different end of shoulder 18. Flange 17 is provided With a straight groove 21, FIGS. 4 and 6 which extends transversely of the lever and opens away from body portion 16. Groove 21, and the combination of shoulder 18 and projections 19, 20, are spaced from the plane of body portion 16, both the groove and the fulcrum end portion of the lever being on the same side of that plane.
Blade 10 is formed as an integral unit from a suitable For example, the blade can be of beryllium-copper alloy sheet on the order of .008 thick. The blade includes two elongated parallel side arms 22 and 23 interconnected at their respective ends by transverse portions 24 and 25. Portion 24 has a central aperture 26. Portion 25 has rigidly secured there-to in any conventional fashion a pair of opposed contact buttons 2'7 and 28, contact 27 having a generally spherical contact surface 29 and contact 28 having a generally spherical contact surface 30. A tongue 31, integral with transverse portion 25, extends from that portion toward portion 24 and is disposed between arms 22, 23. Tongue 31 is rectangular in plan and terminates in a straight bearing edge 32 which extends transversely of the blade and is exposed toward transverse portion 24.
Considering the spring blade 10 to be in its completely relaxed, undistorted condition, as seen in FIG. 7, arms 22 and 23 are iiat for the greater portion of their length, ibut are each lbent out of the normal plane of the 4blade in transversely aligned areas to provide identical curved portions 33 4and 34, respectively, which are concave as viewed from the side of the blade occupied by contact 27 and convex as viewed from the side of the blade occupied by contact 28. Still considering blade 10 in its completely relaxed condition, the straight portions of arms 22 and 23, and the two transverse portions 24 and 25 all lie in a common plane, but the tongue 31 is curved progressively out of that plane in the same direction in which contact surface 29 of contact 27 faces.
Fulcrum member 8 and blade 10 are secured to base 1 by a combined fastener and terminal 35, the shank of the fastener passing through apertures 12 and 26. Mounting leg 11 of the fulcrum member overlies transverse portion 24 of the blade, and these two portions are clamped rigidly against the base, as by the action of screw 36 engaged in a threaded bore of the shank of the combined fastener and terminal 35. Blade extends longitudinally along the base in such fashion that the center of transverse portion, carrying contacts 27 and 28, is disposed between fixed contacts 3 and 5. Fulcrum leg 13 of member 8 is centered between arms 22 and 23 of blade 10 and projects away from the base, and away from the adjacent plane of arms 22, 23, at right angles. Lever 9 is centered between arms 22 and 23 and arranged with projections 19 and 20 engaged respectively in notches 14 and 15, with shoulder 18 engaging that surface of leg 13 which faces the fixed contacts, and with bearing edge 32 of tongue 31 engaged in groove 21.
The distance between shoulder 18 and the bottom of groove 21 is significantly greater than the distance between fulcrum leg 13 and bearing edge 32 when the lever 9 is not in place and the spring blade is in its relaxed or undistorted condition. Accordingly, in order that lever 9 can be accommodated, tongue 31 is displaced away from transverse portion 24, placing arms 22 and 23 under tension.
In this embodiment, the switch is so designed that movable contact 27 normally engages fixed contact 3. To assure that this normal `condition is positively retained, and to achieve return of the movable contacts to their normal position, a helical compression spring 37 is engaged between body portion 16 of lever 9 and base 1. The base is provided with a cylindrical recess 38 in which one end portion is seated. The other end of the spring engages the side of -body portion 16 which is nearer the base. Body portion 16 of the lever is provided with a dimple 39, projecting toward the base, the corresponding end of spring 37 embracing the dimple so that the spring engages the lever at a fixed position. Spring 37 thus resiliently biases lever 9 away from the base.
Since both tongue 31 and bent portions 33, 34 of arms 22 and 23 are initially concave with respect to base 1, insertion of lever 9 so that tongue 31 is placed under axial compression and arms 22 and 23 are stressed in tension results in resilient distortion of the blade 10 in such fashion that the plane of transverse portion 25 slants toward the base. This distortion is accentuated by the biasing action of spring 37 and causes movable contact surface 29 to be urged firmly against fixed contact 3.
Cover 2 includes a flat top wall 40 and dependent side walls 41, the latter being adopted for telescopic engagement with corresponding portions of base 1. Top wall 40 is provided with a cylindrical bore 42 which slidably embraces the plain cylindrical shank 43 of an actuating plunger 44. Plunger 44 has an enlarged conical tip 45 of electrical insulating material, the tip tapering to a rounded apex which engages the side of lever body portion 16 at a point near dimple 39 but located between the dimple and flange 17. With blade 10 in its normal position, with contact 27 engaging contact 3, and with tip 45 engaging lever 9, the shank 43 projects outwardly well beyond wall 40 so as to be exposed for engagement by any suitable operating means (not show-n).
When plunger 44 is moved toward base 1, lever 9 is pivoted (counterclockwise yas viewed in FIG. l), swinging the free end of tongue 31 toward the base, and compressing biasing spring 37. Such action first increases the tension on arms 22, 23, causing these arms to effectively elongate because of the resulting distortion of bent portions 33, 34. As this pivotal movement of the lever progresses, bearing edge 32 of tong-ue 31 ultimately reaches the cross-over point of the snap spring mechanism, at which point the tension on arms 22, 23 is effective to distort lblade 10 in a direction causing transverse portion 25 to slant toward fixed contact 5, so that movable contact surface 30 is brought firmly into engagement with fixed contact 5, as seen in FIG. 3. This distortion of blade 10 occurs with a true snap action, causing movable contact surface 29 to separate cleanly from contact 3 and movable contact surface 30 to make instantaneous contact with contact 5.
When plunger 44 is first actuated, and lever 9 first begins to pivot toward base 1, the resulting effective elongation of arms 22, 23 causes transverse portion 25 to move away from portion 24, so that movable contact surface 29 shifts across the face of fixed contact 3 (from right to left as viewed in FIG. 1), without any separation of the two contact surfaces occurring. This wiping action of contact surface 29 across the face of contact 3 continues until the cross-over point of the spring blade is reached and clean separation of the contacts occurs. The shifting motion of contact 27 relative to contact 3 is not rectilinear but is rather in the nature of a rocking movement resulting from the progressive decrease in inclination of blade portion 25 relative to base 1. Thus, as will be seen by comparison of FIGS. 1A, 1B and 1C, the disc-like body of contact button 27 is initially inclined at a substantial angle relative to the base, when the switch is in its normal position. As pivotal movement of lever 9 toward `base 1 progresses, this angle decreases, as seen in FIG. 1B. Finally, as the -crossover point of the spring blade is reached, the body of contact button 27 reaches a position in which it is essentially parallel to the base and to the flat face presented by contact 3, as shown in FIG. 1C. The spherical form of contact surface 29 assures that, as this change in inclination occurs, a point on contact surface 29 will always be firmly engaged with contact 3, there being a smooth wiping action o-f surface 29 on contact 3 as the button 27 is rocked.
As the movement of plunger 44 carries 'bearing edge 32 Ibeyond the cross-over point, and the spring blade snaps generally pivotally away from base 1 to bring contact surface 30 into engagement with contact 5, the force tending to compress ton-gue 31 decreases and, therefore, the tension on arms 22, 23 decreases. Accordingly, the effective length of blade 10 decreases progressively, :and the movable contact surface 30 tends to -wipe across the face of contact V5 (shifting from left to right as viewed in FIG. 3) with a rocking action in the same fashion described with reference to movement of surface 29 relative to contact 3.
When plunger 44 is released, spring 37 pivots lever 9 away from base 1, causing a reversal of the sequence of movements just described. Accordingly, c-ontact surface 28 is first rocked and wiped across the surface of ycontact 5, as the effective length of arms 22, 23 increases and the cross-over condition for the blade is approached, and the movable contacts are then snapped toward the base, bringing the switch again to the condition of FIG. 1.
FIGS. 8 and 9 illustrate another embodiment of the invention which, as in the embodiment just described, comprises a base 51, fixed contacts 53 and 55, a fulcrurn .member 58, an operating lever 59, and a spring blade 60. Base 51, fixed contacts 53 and 55, and blade 60 are identical to the corresponding parts hereinbefore described with reference to FIGS. 1-7. Blade 60` carries movable contacts 77 and 78 which cooperate with contacts 53 and 55, respectively, in the same manner as contacts 27 and 28, FIG. 1, cooperate with contacts 3 and 5.
The fulcrurn leg `63 of member 58 is provided with a single aperture 64 which is centered Itransversely of the leg and spaced significantly from blade 60 on the side thereof opposite base 51. The fulcrum end portion of lever 59 includes a single longitudinal projection 69 aligned with the longitudinal axis of the lever. Shoulder 68 comprises, two identical portions disposed each at a different side of projection 69. At its opposite end, the lever has a transverse end fiange 67 provided with a groove 71 which accommodates the Ibearing edge of tongue 81 of blade 60. Body portion 66 of lever 59 is bent along a transverse line intermediate the ends of the lever so as to comprise two portions 66a and 66b which diverge away from base 51. A half punch 89 is provided at the center of the junction between portions 66a and Mb, the half punch projecting toward base 51.
Base 51 has a cylindrical recess 88 which opens toward the junction between lever portions 66a and 66b and extends at -an angle such that the recess is inclined away from the end of the ibase on ywhich member 58 is mounted and toward the opposite end of the base. Recess 88 loosely accommodates a coil spring 87, one end of the spring seatin-g on the bottom end of the recess and the other end encircling half punch 89.
A cover 52 is provided and the cover supports an actuating plunger 94 for rectilinear movement toward and away from the base, the cover and plunger being identical with the corresponding parts of the switch of FIG. 1. The rounded tip 9S of plunger 94 engages lever 59 at the bend between portions 66a and 6611.
When pivoted under the inuence of plunger 94 of spring 87, lever 59 lmoves in such fashion that the bend between portions `66a and 65h follows an essentially cir cula-r path. The recess 88 is so positioned that the biasing action of spring 87 is applied along a line which is tangential to that circular path. As seen in FIG. 9, half punch 89 provides a definite shoulder which faces generally toward the pivotal axis of the lever so as to be positively engaged by the end convolution of spring 87. Operation of the switch of FIGS. 8 and 9 is essentially the same as described with reference to FIGS. 1-7.
In both embodiments of the invention, the manner of en-gagement between the fulcrum end of the operating lever and the upstandiug leg of the fulcrum member properly -centers the lever on the base and provides without undue cost or complexity a pivot for the lever which depends only on loosely interengaged elements and the resilient force applied longitudinally by the tongue of the spring blade. This pivot arrangement acts in conjunction with the engagement of the relatively long bearing edge of the tongue of the spring blade in the groove on the lever to assure a stable assembly in whi-ch neither the free end of the spring blade nor the lever itself is subject to lateral displacement under shock or Vibration.
While particularly advantageous embodiments have been described to illustrate the invention, various changes and modifications can be made therein without departing from the scope of the invention as defined i-n the appended claims.
What is -claimed is:
1. In a snap switch of the type described, the combination of a base of electrical insulating material;
a first fixed contact including a contact surface facing away from said base;
a second fixed contact including a contact surface opposed to the contact surface of said first fixed contact;
said first and second fixed contacts secured to said base and spaced from each other spacing the contact surfaces thereof one from the other;
an integral thin spring sheet metal over-center snap spring blade comprising two elongated longitudinally extending arms spaced transversely apart, and first and second transverse portions each interconnecting said arms at one end of said blade opposite from the other,
said second transverse portion having a tongue projecting therefrom toward said first transverse portion and being disposed between said arms;
said tongue having a bearing edge disposed transversely of the blade and exposed toward said first transverse portion;
said arms having transversely aligned portions bent out of the normal plane of the blade and capable of being resiliently distorted to increase the effective length of the blade;
movable contact means fixed to said second transverse portion and having first and second contact surfaces each facing away from a different side of said blade;
a rigid fulcrum member including a mounting leg and a fulcrum leg disposed at an an-gle to said mounting les;
said fulcrum leg having a face directed toward said fixed contacts and disposed transversely of said blade, and at least one opening;
fastener means fixedly securing said first transverse portion and said mounting leg to said base;
a rigid operating lever `being disposed generally between said arms of said 'blade and comprising an elongated body, a transverse flange projecting from one end of said body, and a fulcrum end portion at the other end of the body;
said transverse flange having a groove opening away from said body and being disposed transversely of said lever to engage and retain said bearing edge;
said fulcrum end porti-on having an end shoulder engaging said face and at least one longitudinal projection extending from said end shoulder and loosely within said opening when said fulcrum end engages said fulcrum leg and provides a pivotal connection for said lever;
the distance between said shoulder of and said groove of said lever being greater than the distance between said face and said bearing edge when said blade is undistorted so that said tongue is distorted 4and said fulcrum end is biased into pivotal engagement with said fulcrum leg by engagement of said bearing edge in said groove;
spring means operatively engaged between said lever and base to urge said lever to pivot at its fulcrum end and away from said 'base t-o a normal position wherein said groove is spaced from the side of blade opposite from said base and such distortion of said tongue causes said second transverse portion to slant rfrom said tongue toward said base and cause the first contact surface of said movable contact means to engage the contact surface of said first contact;
actuating means engaging said lever and in response to an actuating force causing said lever to pivot at its fulcrum end and move progressively toward said base until cross-over of said over-center snap spring -blade results wherein said tongue and second transverse portion are snapped to a position slanting away from said base causing lthe second contact surface of said movable contact means to engage the contact surface of said second contact;
such pivotal movement of said lever from its normal position causing said arms to effectively increase progressively and said second transverse portion to progressively change the slant thereof relative to said base by distortion of said transversely aligned bent portions and causing said first contact surface to wipe over and rotate relative to the contact surface of said first contact; and
said spring means causing said lever to return to its normal position when said lever is released by said actuating means.
2. A snap switch according to claim 1, wherein said body portion of said Ilever is fiat, and
said groove and said fulcrum end portion are both displaced from the plane of said body portion thereof on the side thereof opposite said base.
3. A snap switch according to claim 1, wherein said fulcrum end portion of said lever includes two projections spaced transversely of the lever and said end shoulder is disposed between said projections, and
- said fulcrum leg of said fulcrum member is provided with two transversely aligned notches each dimensi-oned and disposed to loosely accommodate a different one of said projections. 4. A snap switch according to clairn 1, wherein said yfulcrum end portion of said lever includes a single,
centrally disposed projection and said shoulder comprises two portions disposed each on a different side of said projection, and said fulcrurn leg of said fulcrurn member is provided with a single, transversely centered opening dimensioned to loosely accommodate said projection. 5. A snap switch according to claim 1, wherein said spring means comprises a helical -compression spring,
said base having a recess aligned with and opening toward said body of said lever and in which said spring is disposed, and said actuating means is disposed to engage said body portion of said lever at a point between the location of said spring and said transverse flange. 6. A snap switch according to claim 1, wherein the length of said tongue is less than one .half the distance lbetween said lirst and second transverse portions of said blade, and said transversely aligned bent `out portions of said arms are located between said second transverse portion 'of said 'blade and said bearing edge of said tongue.
7. A snap switch according to claim 1, wherein said body of said lever is -bent along a transverse line intermediate the ends thereof, the parts of said body on opposite sides of said 'line diverging away from said base, and said spring means includes a helical compression Spring,
said base having a recess in which said spring is seated, said spring extending from said recess into engagement with said lbody of said lever at said transverse line, and said recess loosely constraining said spring to act along a line generally tangential to the circular path followed by said transverse line as said lever is pivoted.
References Cited by the Examiner UNITED STATES PATENTS 2,326,874 8/ 1943 Meuer 200-67 2,374,986 5/1945 Petter 200--67 2,387,089 10/1945 Peters-on et al. 200-67 2,417,652 3/ 1947 Kunzler 200-67 ROBERT K. SCHAEFER, Primary Examiner.
D. SMITH, JR., Assistant Examiner.
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