US2695524A - Alternate action snap mechanism - Google Patents

Description

Ndv. 30, 1 954 M. w. EATON 2,695,524

ALTERNATE ACTION SNAP MECHANISM Filed Jan. 5, 1951 Invewfar ww ww compression. mounting end 6 limits rotation of the toggle 8 in one United States PatentOfilice ALTERNATE ACTION SNAP MECHANISM Malcolm W. Eaton, Freeport, 111., assignor to Minneapolis- Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application January 5, 1951, Serial No. 204,568

Claims. (Cl. 74-100) This invention is concerned with a mechanism adapted to move to alternate positions with a snap action upon successive motions in the same directions of reciprocable operating means. Alternate action mechanisms have been known for a long time but those on the market especially in the form of electrical switches have not been satisfactory. In general they are made up of a multitude of parts assembled together. This larger number of parts is to a considerable extent responsible for the inconsistency in operation due to the accumulation of tolerances. In addition, these switches are generally built as cheaply as possible so the parts are not very accurately made and do not fit together as Well as they should. It is not at all uncommon on purchase of such switches to find that they are inoperative before being installed. Such a situation is in fact so common that purchasers frequently make allowance for such faulty switches and purchase more than are absolutely needed in order to be sure that they have enough workable switches.

It is among the objects of this invention to provide a reliable snap acting alternate action mechanism, to provide a snap acting alternate mechanism having a minimum number of parts, to provide a snap acting alternate action electrical switch without current carrying pivots, and to provide a mechanism of the type described that may be quickly and easily assembled by unskilled labor. It is a further object of this invention to provide an alternate action snap acting mechanism in which rotation of the toggle is accurately limited so as to provide long life by limiting the stresses in the snap acting spring mechanism. It is also an object of this invention to provide an alternate action snap acting mechanism in which the stresses resulting from limiting the rotation of the toggle are kept at the lowest practical minimum.

In the drawings:

Figure 1 is a side view partly broken away of a switch incorporating this invention;

Fig. 2 is a top view of the switch shown in Figure 1 with the button, operating mechanism and shell removed;

Fig. 3 is a perspective view of the toggle employed in the switch shown in Figs. 1 and 2;

Fig. 4 is a plan view similar to Fig. 2 showing another species of the invention;

Fig. 5 is a sectional view along the line 5-5 of Fig. 4, and

Fig. 6 is a perspective view of the spring used in the switchshown in Figs. 4 and 5.

In the embodiment of this invention shown in Figs. 1 and 2 the snap spring 1 comprises tension members 2 and compression member 3 joined together at end 4 which is free to move and upon which is mounted a movable contact 5. The tension members are also con- .nected by a mounting end 6 having a straight edge 7 facing the free end 4 to form a pivot for a toggle 8. The

end 6 of snap spring 1 is mounted in cantilever fashion as by rivets or part punches 9 on a plate or anchor 10,

having integral therewith the terminal 11 into which is threaded the terminal screw 12. The toggle 8, also referred to as the alternator, in this embodiment comprises a piece of electrical insulating material having a seat 13 hearing against the edge 7 so that the toggle 8 pivots thereon. A groove 14, spaced from and opening in the opposite direction from said seat 13, pivotally supports the unattached end 15 of'the compression member 3 so that the compression member 3 is held in bowed An abutment 16 engageable with the 2 direction while another abutment 17 is engageable with the anchor 10 to limit rotation of the toggle 8 in the opposite direction. These abutments are so located as to permit the groove14 to carry the end 15 from one side to the other of the plane of tension members 2, or, as it may otherwise be expressed, to move the compression member 3 through an axis of maximum stress or position of unstable equilibrium, or overcenter with respect to the line of action of tension members 2 to produce a snap action. The dihedral angle formed by the intersection of two surfaces 18 and 19 forms a ridge or apex 20 parallel to the seat 13 and groove 14. A projection 21, spaced from the ridge 20 on surface 18, forms a valley 22 with the surface 18. In like manner, projection 23, spaced from ridge 20, forms with the surface 19 a valley 24. The ridge 20 is so located that the seat 13 is on a line substantially bisecting the angle between surfaces 18 and 19. The parts previously mentioned .form a subassembly mounted in the U shaped base 25 by sliding the anchor-10 from one end of the base into, a slot and grooves (not shown) formed in the upstanding walls forming the legs of the U so that the terminal 11 and terminal screw 12 are outside the wall while the anchor 10 and the other parts are inside. A stop establishing an upper limit for movement of free end 4 is provided by a contact 26 mounted on terminal 27 having a terminal screw 28 threaded into it. This contact 26, ter minal 27 and screw 28 form another sub-assembly slipped into a slot (not shown) in the other end of the U-shaped base 25, so that the terminal 27 passes through the wall and screw 28 is outside while the contact 26 is inside in position to be engageable by moving contact 5. The lower stop is formed by contact 29 mounted on terminal 30 having a terminal screw 31 threaded therein. This sub-assembly is similarly mountecl'in a slot in the end of base 25. r

The operating mechanism shown in connection with the invention comprises a spring 32 supported on ledges 33 in the base 25 which spring supports a driver 34. A button 35 has a groove 36 to position the driver 34 on spring 32 in alignment with the pivot 7. The spring 32 biases the driver 34 and button 35 toward their normal positions. The operating mechanism is retained on the switch mechanism and the switch mechanism sub-assemblies are prevented from coming out of the base 25 by a-shell 37 in the form of an open rectangle having a flange 38 engageable with a flange 39 on the button 35 to retain said button 35 in proper relationship with the base 25. The rectangular portion of the shell 37 fits around the open top of the U-shaped base 25 and rests 'upon steps 40 thereon. Depending ends 41 of shell 37 cover the open ends of base 25 preventing the subassemblies from becoming disassembled from base 25. Bars 42 on the shell 37 provide mounting means for the switch.

The ridge 20 on toggle 8 is so positioned that it moves from one side to the other of a plane through the pivot 7 and thenormal position of the driver 34 as the toggle 8 is rotated from one limiting position to the other. The projections 21 and 23 are so positioned that each always remains on one side of this plane. The surfaces 18 and 19 are alternately positioned to form an obtuse angle with respect to the line of motion of the driver 34. Rotation of toggle 8 is limited to an angle substantially smaller than the supplement of the dihedral angle formed by the surfaces 18 and 19 so that, as shown in Figure 1, when the button 35 is depressed, the driver 34 engages the surface 19 and is deflected against projection 23. Further movement of the button 35 causes the driver 34 to exert a torque on toggle 8, rotating it clockwise to its limiting position, with abutment 16 engaging mounting end 6, and so moving the compression member 3 upward overcenter causing the movable contact 5 to snap from stationary contact 26 to stationary contact '29. When the button 35 is released, the driver returns to its normal position without moving the toggle 8. The next time the button 35 is depressed, the driver 34 engages surface 18 and is deflected against projection 22. Further movement of button 35 causes the driver 34 to exert a torque on toggle 8, rotating it counterclockwise to its limiting position with abutment 17 engaging anchor 10.

This movesv the compression member 3 downward overcenter to the position shown in Figure 1, causing the movable contact 5 to snap from stationary contact 29 to stationary contact 26. When button is released spring 32 returns driver $4 :ndbutton 35 m their normal positions and the switch parts are all again in the'position's wn ra r H r From a theoretical standpoint it isniost desirableto limit rotation of the toggle in such a manner that movement of the supported member is limited with respect to the supportingrnember. Therefore; it is desirable to have the toggle stop against the supporting member which may or m yi s d a re nf t fi in b l he species shown in Figs. 1, 2 and 3 thi s p'rinciplehas been employed satisfactorily because movement of the driver is limited by limiting movement of the button. In some applications it isimpossible or impractical to limit movement of the driver except by the toggle itself; When this condition isencountered, the construction described is undesirable from a practical standpointsince it subjects the supporting member to severe bending stresses when it stops movement of the abutments and also because the toggle is at the same time subjected to severe stress :at the pivot when lower abutment stops motion of the toggle. Sometimes it is impractical to strengthen these parts, as in electrical switches in which the toggle is made of plastic to insulate the operating mechanism from the live switch parts. Size is limited and costs must be kept down in order to meetcompetition so that more material cannot be used to strengthen the parts adequately. To meet this difiiculty, .the construction shown in Figs. 4, 5 and 6 may be used. While not as accurate in limiting toggle rotation, it limits the severe stresses referredto with regard to Figs. 1,2 and 3 by having the abutments on the sarne side of the pivot as theforce applied by the driver and by stopping against the more rigid base rather than the supporting member.

In the embodiment,shownin lfigs. 4, Sand 6 the snap spring 43 shown in Fig. 6 is made of leafspring material having a U-shaped slot to form elongated members 44 and tongue 45 interconnected atend 46 which; is free to move and upon which is mounted contact 47.

.The opposite ends of'the elongated members a're connected by a bridge 48 having a straight edge 49 on the side nearest the end 46 to act as a pivot. The mounting portion 50 is connected to the elongated members 44 by side members 51 The 'mounting portion 50, the side members 51 andthe bridge 48 forrnthe boundaries of an aperture 52. The mounting portionSil and side members 51 are clamped between two U-shaped anchors 53 fastened to the base .54 as by a screw 55 threaded into an insert (not shown) passing through base 54. The

toggle 56 pivoted atbearin'g 57 on straight. edge 4? has a groove 58 supporting end 59 in pivotal fashion to stress tongue 45 in bowed compression. The abutment 66 'on one side of the bearing 57 is engageabie withv base 54 to li it counterclo kwise rotation of toggle 5'6. Abi itrnent 61 on the other side of bearing 57 is adapted to pass through aperture 52 and engage base 54 a) limit clockwise rotation of toggle 5 6, These ab it'inents are so positioned with respect to bearing 57 v and groove 58 to p errnitrnovement of groove 5 8 frorr 1 one side to the other of the plane of tension members 44 to move the tongue through an axis of maximum stress and so cause, the free end 46 to move with a snap action from one limiting position to another. A ridge 62 and projections 63 on the toggle 56 are similar to and perform the same function as the corresponding parts described in connection with Figs. 1,2 and 3. Contact 64, fastened to base 54, by screw 65 threaded into a metal insert (not shown) passing through base 54, and contact 66, retained on the base 54 by screw 67 threaded into another metal insert (not shown) passing through base 54, serve as "stopsto limit tr'avel of the free end 46 Te'rminals 68 on the exterior of base .54 are retained on the base by screws 69 threaded into the inserts mentioned above and serve to connect the switch to an external circuit. V i H Any suitable operating mechanism such as that shown in Figure 1 may be employed with this switch mechanisin, the switch mechanism operating inthe same manner as that described in connection with Figs. 1, 2 and 3 except that rotationof the toggle 56 ,is v abutments 6t) and 61. engaging .bas'e54; It will thus b;e seen that the abutment 60 or 61 limiting rotation of the tq .5 is t e s m s f the. Pi 9 r2 t the force applied by the driver to move the toggle 56 in order to reduce the stress in the supporting member 48 and in the toggle 8 whenever it is impossible or impractical to limit movement of the driving member.

I claim:

1. In combination, a leaf spring having a pair of spaced side members joined at each end, a flexible tongue integral with a first of said ends and extending between said side members in spaced relation therefrom to define therewith a U-shaped aperture, and a mounting portion at the second of said ends having an edge thereof extending transversely between said side members and forming a fulcrum, a toggle having two surfaces intersecting to form a ridge and defining a dihedral angle, said toggle having projections extending outwardly respectively from each of said surfaces in spaced relation from said ridge, said toggle being formed with a notch therein defining a bearing for pivotally mounting the toggle which is disposed in a plane substantially, bisecting said angle, abutments to limit rotation of said toggle about said pivot to an angle substantially smaller than the'supp'lement of saiddihed'ral angle, sai'd'tog'gle being formed with a groove spaced from the pivotal mounting of. the toggle, said toggle being pivotally mounted with said bearing on said fulcrum 'on and supporting the free end of the tongue in said groove to how the tongue in compression and stress said side membersin tension, at base, means for immovably mounting the leafspring at said mounting portion thereof incantilever fashion on said base, a pair of stops limiting motion of said fi'r st end of the leaf spring positioned to permit the toggle groove to cross the plane of said side members as said toggle is rotated between its limiting positions to snap said first end of the leaf spring fromon'e' stop to the other, and a reciprocable driver operable to be moved toward said toggle pivot to engage one of said toggle surfaces and to be deflected therealong into engagement with one of said projections to move said toggle from one limiting position to the other. 7 i

2. An alternate action mechanism comprising a base, a flat snap spring having a first portion immovably mounted on said base, said first portion having an edge forming a fulcrum which is fixed with respect to said base, said snap spring being movable through a position of unstable equilibrium between two stable positions in response to movement of a second portion of said snap spring with respect to said mounted first portion of the snap spring, an alternator pivoted on said fulcrum on said first portion of the snap spring and operably connected to said snap spring to effect movement of said second portion thereof, projections on said alternator disposed at opposite sides of the pivot therefor, and a driver re'ciprocable with respect to said base in adire'c'tion perpendicular to the face of said snap sprin and operative to engage said projections alternately to rotate said alternator in opposite directions and move said snap spring alternately from one stable position to the other.

3. A snap acting switch comprising 'a base, a pair of spaced opposed stops mounted on said base, at least one of said stops defining a fixed contact, a flat snap spring mounted in cantilever fashion at one end on said base and at its other end carrying a mobile contact movable between said spaced opposed stops for engagement alternately therewith, said one end of said s'na'pfs'pring having an edge which is fixed with respect to said base and forms a fulcrum, said snap spring including a flexible member spaced from the mounted end of the snap spring and interconnectedwith the contact c'arrying movable end of the snap spring, an alternator pivoted on said fulcrum on said one end of the snap spring and in spaced relation from its pivotal mounting engaging the end of said flexible member remdte from the contact-carryin'g movable end of the snap spring for effecting snap action movement of said movable endofthe snap spring to move said mobile contact substantially directly away from one of said stops into engagement with the other of said stops, projections on said alternator disposed on opposite sides of the pivotal mounting for the alternator, and a driver reciprocable with respect to said base in a direction perpendicular to the face of said snap spring and operative to engage said projections alternately upon successive icipiocations of the driver to rotate said alternator in opposite directions and move said mobile contact from one stop to another.

4. In combination, a leaf spring having a pair of spaced side members and end members integrally joined with the side members at each end, a flexible tongue integral with a first of said end members and extending between said side members in spaced relation therefrom to define therewith a U-shaped aperture, the second of said end members having an edge thereof extending transverse said side members and forming a fulcrum, a base, means for immovably securing said second end member to said base and supporting said fulcrum in fixed relation to said base, a toggle having a first pair of surfaces intersecting to form a ridge, projections on said toggle extending outwardly respectively from each of said surfaces in spaced relation to said ridge, said toggle having a second pair of intersecting surfaces defining a notch the apex of which is disposed substantially in the plane bisecting the angle between said first pair of surfaces, said second pair of surfaces diverging relative to a plane through the apex of said notch and perpendicular to the plane bisecting the angle between said first pair of surfaces, said toggle having a groove therein spaced from said notch and opening in a direction opposite thereto, said toggle being pivotally mounted on said leaf spring with the apex of said notch seated on said fulcrum and supporting the free end of said tongue in said groove to bow the tongue in compression and stress said side members in tension, said second pair of surfaces providing abutments to limit rotation of said toggle about said fulcrum, a pair of stops for limiting motion of the free end of said leaf spring positioned to permit the toggle groove to cross the plane of said side members as said toggle is rotated between its limiting positions to snap the free end of the leaf spring from one stop to the other, and a reciprocable driver operable to be moved toward said toggle fulcrum to engage said toggle surfaces and be deflected therealong into engagement with one of said projections to move said toggle from one limiting position to the other.

5. The combination of claim 4 wherein said means for securing said second end member to said base includes a support plate secured to said second end member and underlying said second end member adjacent said fulcrum, and means for fixedly securing said support plate to said base.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,502,785 Kerwin July 29, 1924 2,021,041 Altamura Nov. 12, 1935 2,295,484 Krieger Sept. 8, 1942 2,460,087 Hollis Jan. 25, 1949 2,537,682 Ljungfeldt Jan. 9, 1951 FOREIGN PATENTS Number Country Date 985,620 France Mar. 14, 1951

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