US3038043A - Snap acting switch - Google Patents

Description

June 5, 1962 D. G. woLFE SNAP ACTING SWITCH Filed June 8, 1960 United States Patent O Filed .lune 8, 1966, Ser. No. 34,716 Claims. (Cl. 20G- 67) This invention relates to switch mechanism and more particularly to a heavy duty snap `acting switch.

Much diiculty has been experienced with snap acting switches heretofore generally used in conjunction with slow moving actuators of the type embodied in thermostatic control devices. Progressive application of a switch operating force by a thermostatic element requires a relatively high contact pressure force to assure mating convtact until the instant of snapo-ver. In order to prevent welding of the mated contacts, many conventional switches provide -a wiping action to the movable contact relative to the stationary contact. However, it has been found that the wiping action force also causes a decrease 1n the contact pressure force, which enhances the welding problem and, in some instances, initiates chattering between the mated contacts.

It is, therefore, an object of this invention to elimieate the foregoing problems by `a relatively simple switch structure.

Another object of this invention is to use separate and independent forces for the wiping action and the contact between mated switch contacts.

Another object of this invention is to maintain the magnitude of the contact pressure force substantially constant until the instant of snapover in a snap acting switch.

A further object of this Vinvention is to preclude the components of the wiping action force between mated contacts in a snap acting switch from affecting the magnitude of the contact pressure force.

In one aspect of this invention, an actuating lever is moved by an applied force to actuate an overcenter spring which exerts a contact pressure force on'an actuated blade. Prior to snap action, the lever movement also causes a shifting of the blade to provide a wiping action between mated contacts and such wiping action is accomplished without affecting the contact pressure force.

Other objects and advantages -of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a longitudinal sectional view of a switch housing and switch mechanism embodying this invention;

FIG. 2 is a View similar to FIG. l showing a second position of the switch mechanism; and

FIG. 3 is an exploded perspective View of a portion of the switch mechanism shown in FIG. 1.

As is illustrated in FlG. l, a two-part switch housing, indicated generally at lil, is formed of a molded plastic or like dielectric material and comprises a top cover member 12 secured to a base member 14 by any suitable means (not shown). A pair of xed contacts 16 and 18 are mounted in spaced parallel relation by means of - terminals 26 and 22, respectively, which extend through a wall of the base member 14 to be electrically connected to conventional lead wires.

A current carrying switch blade 24 has a generally rectangular configuration and is made from a good conducting material, such as copper or the like, so `as to be substantially inexible. The substantially rigid blade 24 has a movable end portion 26 carrying a contact 28 which is disposed in the space between the fixed contacts 16 and 18 that serve as stop members to define the limited movement of the switch blade 24 in a vertical direction. Adjacent the movable end portion 26, the blade 24 has a rectangular opening 3? and an aper rice tured tab 32 extends into opening 30 from the movable end portion 26. Intermediate its ends, the blade 24 is reduced in width so as to present a pair of bearing surfaces or edges 34 and 36 disposed-on opposite sides of the longitudinal 1axis of blade 24. Adjacent the bearing edges 34 and 36, the blade 24 is provided with a U-shaped resilient portion 38, the end of which terminates in spaced mounting tabs 40 and 41. A third mounting tab 42 is formed by cutting or stamping a U-shaped aperture in the rear leg of resilient portion 3S so -as to be in the same parallel plane as, but oppositely disposed to, the tabs 40 and 41.

As is illustrated in IFIG. 3, a combined lmounting terminal bar 44 is fabricated from a single piece of material into a pair of oppositely extending horizontal members joined by a vertical member. The lower horizontal member 46 extends through a sidewall of the base member 14 for connection to -a suitable lead wire. The vertical member 48 lies flush against the inside surface of the sidewall of base 14 and is provided with a downwardly lextending retaining lug 50. The second hori-v zontal member 52 has a pair of spaced rectangular openings 54 and 55 adjacent its edge joining the vertical member 48; the apertures 54 and 55 are disposed to be in alignment for receiving the spaced mounting tabs 40 and 41 of the blade 24. Adjacent its forward edge, the horizontal member 52 has `a pair of spaced depressions 56 and 57, the front edges of which are located so as to be in substantially the same vertical plane as' deined by the bearing surfaces 34 and 36 of the blade 24 when such blade is in the position shown in FIG. 1.

A substantially rigid actuating lever 58 comprises a pair of spaced parallel arm members 60 and 62 disposed in an edgewise manner and joined intermediate their ends by a horizontal web portion 63. Adjacent the mounting end of the lever 58, the two arms 60` and 62 are formed with upper mounting bearings' 64 and 65,"respectively, and lower V-shaped bearing notches 66 and 67, respectively. As is illustrated in FIG. l, the upper bearings and lower notches are disposed in the same vertical plane With the upper bearings 64 and 65 being disposed in the depressions 56 and 57 of the terminal mounting bar 44 and with the lower notches 66 and 67 receiving the bearing edges 34 and 36, respectively, of the switch blade 24.v Adjacent the free end of the lever 58, the arms 60 and 62 -terminate in upwardly extending leg members 68 and 69, respectively, each of which `is formedwith a V-shaped bearing notch 70 and 71, respectively, that serves as a pivotal axis.

A toggle link 72 has a substantially V-shaped configuration, the forward end being a pair of downwardly sloping spaced parallel arms 74 and 75 terminating in knife edges 76 and 77, respectively, which are adapted to be respectively disposed in the V- shaped notches 70 and 71 of the lever 53. The rearward end 78 of link 72 has a stop member 79 to engage the upper surface of blade 24 when the switch is in the position shown in FIG. l. From the stop 79, the rearward end 78 is reduced in width so as to extend through the aperture 30 in the blade 24 and terminates in a second stop ange 80 which engages the undersurtace of the blade 24 when the switch is moved to the position shown in FIG. 2. A notch on the rearward end 72 receives one end of the tension coil spring 84, the other end of which is looped through the apertured tab 32 of the blade 24.

An operating plunger 86 slidably extends through the casing 1t) and engages the web portion 63 of the actuating lever to apply an operating force thereto.

In the operation of the device illustrated in FIG. l, an operating force is applied to the plunger S6 and transmitted to the actuating lever 58. The biasing force of the coil spring S4 is exerted on the free end of the blade toggle link ,72 tending to rotate the same `in a counterclockwise direction about the pivot axisvdefined by the Vnotches'7fi and 71,V since the line of action of spring lpasses below the pivot axis defined by notches 70 and 7l. Pivotal movement of link 72 ,in a counterclockwise directionY is limited by the upper ange stop 79 that engages the upper surface o1 the blade 24 and thus increases the contact-pressure force.

As the operating force is increased,'the actuating lever 58 is pivoted clockwise about an axis delined by the Vmounting bearings 64 and 65causing the pivotal axis Ydefined by the V-shapecl Vnotches 70 andr 7i 'to move vdownwardly to .a critical position where such pivotal axis `is moved into coincidence with the line of action of spring 84. At this-critical position, the spring'for'ce tending to .rotate the toggle link 72 about the pivot axis defined by y- notches 70, 71 is Zero because the line of action of the 4coil spring 84 passes through'the axis of pivotal moveexert a downward pull onthe movable end 26 so that the contact pressure force remains substantially unchanged until the toggle notch S2 is moved toits upward l position. With such an arrangement, the contact pressure `force is not affected untily theinstant of changeover y because theftension .of the coil spring 84`is not appreciably Y.ment of link 72; However, the end of the coil spring 84 Y whichis hooked on Vthe apertured tab 32 continues tov member 38. Such a movement causes a longitudinal Y shifting of the blade 24 lto supply a wiping action between the contacts 2S and 18 which is in a plane substantially perpendicular to the direction Vof the Vsnap action. 1t should be .noted that the displacement of .the bearing surfaces 34 and 36 of the blade 24 is substantially horizontal, iie., in a direction which'is perpendicular to the vertical direction of the movable contact 23. Inasmuch as the bearing surfaces 34 and 36 are moved in `substantially lthe Vsame horizontal ldirection as the apertured tab 32 in accordance with movement-of lever 5S during the wiping action force; accordingly, the wiping action force V'uses its full magnitude as the horizontal component and does not diminish the contactpressureforce because the vertical component has zero magnitude. The contact pressure force which is exerted bythe coil spring 28 is unaffected by the wiping action force so that substantial lever 58. As is shown in FIG. 2, the toggle connected end of vthe coil spring 84 is disposed above the strip 24 so that the spring force exertedon the free end 26 has a direction that is reverse to FIG. l and the movable contact 28 is held in engagement with the upper ixed contact 16. Because of the increase of the force applied on the plunger 86, the lever 5S is rotated and causes a slight depression of the VU-shaped member 38 of the blade 24 which thus performs the second function of a return spring.' The'coil spring84 never overcomes the bias of lbeU- shaped portion Sgin one position, it adds to the bias 4 against the plunger 36 and in the other position, it subtracts. Consequently, the operatingrlever 5S is always biased in one direction by the U-shaped member 38 so that operating force may be automatically applied by means of a thermostatic element.

As the applied force on the plunger 86 is decreased, the resiliency of the U-shaped portion 38 causes the bearing Vedges 34 and 36 ofthe blade 24- and the notches 66 and 67 of the lever 58 to move longitudinally to the right as viewed in FIG. 2 and thus provide a wiping actionbetween the movable contact 28 and the'ixed contact 16. When `the operating force decreases to a value below its critical value, the toggleV link 72 is rotated counterclockwise and eifects a snap actingrrnovement of the movable contact 28 to its original position, as shown in FIG. l.

vIt should also be noted that the wiping action l.produces av self-cleaning eifect `on the contact sur-faces and 'is also effective to break any weld that may have been formed between contact surfaces during a previous contact making action. In the event a weld occurs, the wiping action force is increased to a value sufficient to shear the welded contact surfaces.

inasmuch as Vvarious changes maybe made inthe foregoing description and drawings, it is intended that the disclosure Iherein be interpreted as illustrative and not in a limiting sense.

'I claim:

l. in a Vsnap acting switch, `the combination comprising a pair of spaced stationary contacts, a Asubstantially rigid current carrying :blade having a `ixed end portion and a movable end portion, contact means affixed to said movable end portion 4and disposed for alternate engagement with said stationary contacts,.an actuating lever having a mounting end disposed adjacent said xed end portion and a connecting end disposed adjacent said movable-end portion, pivot means `for-med. on said connecting end, a

Vtoggle member having connecting means lon one end and means on said movable end portion isbiased into engage- :wiping action, there vis no vertical component to the ment with one of said stationary contacts, means for the mounting end Vof said lever defining a pivotal axis therefor, said lever being movable about its pivotal axis by an applied force to rotate the pivot means lon its -connecting end through a critical position where the pivot means on said connecting end is in alignment-with said linovable end portion causing said toggle memberto swing about its pivot means and said spring means to Amove through a dea'dcenter position whereby the biasing force exerted on said movable end portion reversed its direction to transfer said contact means to the other of said Y stationary contacts with a snap action, a resilient U-shaped member integrally formed on said blade adjacent its fixed end-portion and being compressi'ble in response to longitudinal movement of said blade, and means on said lever adjacent its mounting end engaging said blade adjacent said U-shaped member for exerting a force on the same and longitudinally moving said blade in a direction substantially perpendicular to the snap action movement of said contact means whereby the ksame is provided with a wiping action without influencing the magnitude of the biasing force exerted by said spring means.

2. A snap acting mechanism comprising a frame, an actuating mem-ber mounted at one end upon said frame for-pivotal movement about a iirst axis, an actuated member having a resilient U-shaped mounting portion at one resiilent mounting portion to bias said actuating member to a first end limit of pivotal movement about said rst axis, a toggle member mounted at one end upon the other end of said actuating member for pivotal movement about a second axis parallel to said first axis, tension spring means coupled at one end to 4the other end of sai-d toggle member for pivotal movement about a third axis parallel to said rst axis and coupled at its other end to the other end of said actuated member for pivotal movement about a fourth axis parallel to said first axis, the line of action of said spring means passing through said third and said fourth axes in perpendicular relationship thereto, stop means on said toggle member engagea-ble with said arm portion when said actuating member is in its normal position to establish a normal position of said actuated member wherein the line of action `of said spring means is laterally offset from said second axis at one side thereof to thereby resiliently bias said other end of said actuated member to its normal position, and means for pivoting said actuating mem-ber about said first axis against the `biassing action of said mounting portion to an actu-ated position wherein said second axis is shifted into laterally offset relationship with the line of action of said spring at the other side thereof to thereby resiliently bias said actuated member away from its normal position.

3. In a snap acting switch having a frame, a pair of vertically spaced fixed contacts on said frame, a movable contact mounted at one end of an elongate contact carrying member, and means supporting the other end of said contact carrying member on said frame to support said movable contact for vertical movement between said fixed contacts; an actuating member having means thereon defining a horizontal pivot axis, means supporting said actuating member on said frame for movement between a normal position and an actuated position along -a path wherein said pivot axis is moved in a substantially vertical direction adjacent said one end of said contact carrying member with said axis extending in a direction normal to the longitudinal extent of said contact carrying member, a link mounted Ion one end of said actuating member -for pivotal movement about said axis, a tension spring coupled at one end to the other end of said link, means coupling the other end of said tension spring to said one end of said actuating member ywith the line of action of said spring lying in a vertical plane normal to said axis, stop means in said link engageable with said contact carrying member when said actuating member is in said normal position to establish a rest position of said link wherein the line of action of sai-d spring passes below said horizontal axis to apply a resilient biassing force to said contact carrying member having a vertical component urging said movable contact against one of said fixed contacts, said actuating member being operable upon movement from said normal position to said actuated position to shift said horizontal axis downwardly to alocation below the line of action of said spring to reverse the direction of the vertical component of biassing force applied by said spring to said contact carrying member to thereby bias said movable contact against the other of said `fixed contacts.

4. In a snap acting switch having a frame, a pair of vertically spaced fixed contacts on said frame, a movable Contact mounted upon one end of an elongate contact carrying member, and means supporting the other end of said contact carrying member on said frame to support said movable contact for vertical movement between said fixed contacts .and horizontal movement longitudinally of said contact carrying member; an actuating member mounted at one end upon said frame for pivotal movement about a first horizontal axis extending in a direction normal to the longitudinal extent of said contact carrying member at a local spaced above said contact carrying member adjacent said one end thereof, said actuating member extending laterally from said first axis in a direction longitudinally of said contact carrying member to an opposite end located adjacent said one end of said Contact carrying member, means on said opposite end of said actuating member defining a second pivotal axis extending parallel to said first axis, a link mounted at one end of said actuating member for pivotal movement about said second axis, a tension spring coupled at one end to the other end of said link, means coupling the other end of said tension spring to said one end of said contact carrying member with the line of action of said spring lying in a vertical plane perpendicular to said second axis, means for swinging said actuating member in pivotal movement about said first axis between a normal position and an actuated position, abutment means upon said link engageable with said contact carrying member when said actuating member is in said normal position to establish a rest position of said link wherein the line of action of said tension spring passes below said second axis to apply a resilient biassing force to said contact carrying member having a vertical component urging said movable contact against one of said fixed contacts, said actuating member being operable upon movement to its actuated position to shift said second axis downwardly to a location below the line of action of said spring to reverse the direction of the vertical component of biassing force applied by said spring to said contact carrying member to thereby bias said movable contact against the other of said lfixed contacts.

5. In a snap acting switch as defined in claim 4, where said means supporting the other end of said contact carrying member on said frame include resilient means exerting a biassing force directed longitudinally of said contact carrying member; means on said actuating member engaging said contact carrying member for shifting said contact carrying member longitudinally against the action of said resilient biassing means upon movement of said actuating member from said normal position t0 said actuated position whereby said actuating member is resiliently biassed to its normal position. l

References Cited in the file of this patent UNITED STATES PATENTS 2,537,682 Ljungfeldt Ian. 9, 1951 2,573,588 Miller Oct. 30, 1951 2,697,145 Winet Dec. 14, 1954 2,729,715 Broch Jan. 3, 1956 2,789,172 Happe Apr. 16, 1957 2,825,779 Kelleigh Mar. 4, 1958

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