US3270157A

US3270157A - Snap mechanism for slow-break electric switches

Info

Publication number: US3270157A
Application number: US398999A
Authority: US
Inventors: David W Johnson
Original assignee: Arrow Hart and Hegeman Electric Co
Current assignee: Arrow Hart and Hegeman Electric Co
Priority date: 1964-09-24
Filing date: 1964-09-24
Publication date: 1966-08-30
Anticipated expiration: 1983-08-30
Also published as: GB1100648A

Description

Aug. 30, 1966 D. W. JOHNSON 3,270,157

SNAP MECHANISM FOR SLOW-BREAK ELECTRIC SWITCHES Filed Sept. 24, 1964 INVENTOR.

20 @0V/d l/l/L/O/VUSOU BY /7/'5 Uf/omeys MMM.

United States Patent C) 3,270,157 SNAP MECHANISM FOR SLOW-BREAK ELECTRIC SWITCHES David W. Johnson, Newington, Conn., assignor to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn., a corporation of Connecticut Filed Sept. 24, 1964, Ser. No. 398,999 2 Claims. (Cl. 200-67) This invention relates to electric switches. More particularly, it relates to overcenter switch mechanisms which act with a snap action to cause engagement and disengagement of switch contacts.

Heretofore, switch mechanisms have been known for use in A.C. circuits for opening switch contacts an optimum distance by what is known as a slow-break. In such devices, an operating member lwas moved between two positions, but it could be held in inbetween positions in which the movable and iixed contacts were neither fully engaged nor fully separated. In such intermediate positions, the contact pressure was not suicient for firm contact and the contacts could overheat, ora small arc could develop, damaging the contacts in either case. Hence, the ability to tease these switches was undesirable.

For many years, overcenter switch mechanisms have been used to snap a movable contact from one position to another, but the movable contact member commonly moved as a unit with overcenter operated member. These switches, beside being relatively expensive, did not possess the advantage of the slow break, optimum-contact separation features.

In recent years, increased horsepower ratings and needs for switches with a longer life required a re-evaluation of the switch structure in the light of the new and heavier duties, such switches are required to perform, such as in connection with floor polishers and other appliances. Manufacturers of such appliances demanded a switch structure which would perform satisfactorily for upwards of 100,000 cycles or operations.

Therefore, it is an object of this invention to provide an improved switch mechanism embodying advantages heretofore available in only one or another types of prior switches, which improved mechanism will be capable of greatly increased life and yet can be made and sold at competitive prices.

Another object of the invention is to provide a switch mechanism embodying the advantages of movement of the movable contact from one position to another independent of the handle or operating member, in combination with slow-break, optimum contact separation features.

Other objects and advantages will appear as the invention is described in connection with the accompanying drawing.

In `the drawing:

FIG. l is la longitudinal section view through a switch embodying the invention, showing the switch in opencircuit position.

FIG. 2 is a View similar to FIG. 1, but with the contacts in closed-circuit position.

FIG. 3 is an exploded view showing in perspective the operating button, the operating member and yoke member.

Referring to the drawing, the parts may be housed in a casing, preferably of generally rectangular shape having coperating top and bottom parts such as hollowed out base and an internally recessed cover 12 molded from insulating material.

One or two pairs of fixed and movable contacts may be provided, each pair being located along one longitudi- ICE nal casing wall. Fixed contact 14 may be conveniently stamped from sheet metal and may have a contact button 14e affixed in downwardly facing direction to an overhanging arm 14a of the contact. The contact may also be provided with a conventional terminal portion 14t accessible from the outside of the base for connection of conductor wires, as usual.

The movable contact 16 may be stamped from thin flexible sheet metal as a long narrow strip having la button 16C on one end adapted to engage and disengage the xed contact button 14a` as the movable Contact 16 is operated. The opposite end of the movable contact is axed to a terminal member 18 stamped conventionally from sheet metal and having a portion accessible from the outside of the casing for connection of conductor wires, as usual. The movable contact is normally biased toward engagement with the fixed contact 14C.

To move the movable contact 16 against its bias and away from the fixed contact 14e` and also to allow the movable contact to engage the fixed contact, a swingable yoke member designated generally by the numeral 20 is provided.

The yoke may be lformed of tough ilexible synthetic insulating material, such as nylon, in generally U-shape with oppositely out-turned feet 23 and 24 at the ends of its

parallel arms

21 and 22 and may have axially aligned

cylindrical trunnions

25 and 26 extending beyond the ends of said feet for pivotally supporting the yoke. The trunnions may be seated in opposite bearing notches or recesses 25u formed in the sides of the base 10 at or near the top edges of said sides. To move the movable contact against the bias in order to disengage xed :and movable contacts, cam surfaces 27 are formed on the inner or under surfaces of each of the feet 23 and 24 of the yoke 20.

To swing the yoke 20 between two opposed positions a coiled compression spring 28 is provided which arts with an overcenter action to snap the yoke between its two positions, as the line of action of the spring is swung through its overcenter position in known fashion. The spring may be seated at one end on a nub 29 formed in the transverse portion of the yoke. The opposite end o the spring seats against tan-d engages with a finger 32 formed on an actuating member 30.

The spring actuating member may be of any convenient shape with a pivot pin 34 passing transversely therethrough adapted to seat in bearing recesses 36 formed in the cover 12. The cover 12 is recessed or apertured centrally to receive the portion of the operating member located above the pivot 34. For actuating the operating member 30, an arm 38 is directed radially from the pivotal axis of the operating member toward a recess 42, formed in an operating button which is reciprocable between depressed and elevated positions.

The operating buttom-member designated generally by the numeral 40 is slidably mounted in the casing. The buttom member is preferably formed or molded from insulating material into the form best illustrated in FIG. 3 with a main body portion 41 from which upwardly extends a cylindrical button portion 44 adapted to be operated manually or by foot pressure.

The button portion extends through an aperture in the cover 12. To guide the movement of the button in a rectilinear path, a leg 46 extends downwardly or inwardly from the body of the button member and slidably tits within a Irecess or well 47 formed in the base of the casing. Preferably the leg and guide recess will be rectangular or non-circular in cross section to prevent the buttom member from rotating about i-ts vertical axis.

The button-member 40 is normally pressed upwardly or outwardly of the casing by a coiled compression spring 48 seated in a well or bore 49 in the base of the casing and pressing at its lower end upon the bottom of the bore 49 and at its top against the body portion 41 of the button-member. The button-member is kept from being pressed out of the casing by shoulders 43 on the body portion engaging the inner surface of the cover 12 adjacent the circular aperture through which the button portion 44 of the button-member extends.

It will thus be seen that when the button is in normal positon, it is elevated by the bias of the spring 48. In such position, the parts occupy the positions illustrated in FIG. l wherein the actuating member 30 is tilted With the linger 32 inclined to the left in what may be called the seven oclock position. The yoke 20 is thus biased by the overcenter spring 28 into the position where the high point 27h of the cam surface 27 presses the movable contact 16 downwardly to cause disengagement of the movable contact button 16e from the fixed contact button 14C.

When the button is depressed, the actuating member 30 is moved to the position shown in FIG. 2 by reason of the counterclockwise rotation thereof caused by engagement of the arm 38 with the Walls of recess 42 in the button-member 40. Such counterclockwise movement causes overcenter action of the overcenter spring and snaps the yoke 20 from the position of FIG. 1 to the position of FIG. 2. This causes the cam surface to be substantialy parallel to the top and bottom surfaces of the casing or, in other words, horizontal as viewed in FIG. 2. Such movement of the cam surface permits the movable Contact 16 -to move upwardly under its normal bias and to engage the fixed contact button 14C.

It will be noted that the amount of movement permitted the movable contact with respect to the ixed contact is certain and can be predetermined so that the movable and fixed contacts will separate the optimum distance for most effective arc-quenching.

Moreover, movement between `open and closed positions of the contacts, although it is initiated by movement of the operating button 40 is nevertheless free of and independent from movement of the ope-rating button once the `overcenter spring has passed through its overcenter position. It is not possible, therefore, to tease the movable contact or to hold the movable contact in an intermediate position or in any position inbetween its normal on and normal oft positons. This prevents the operator of the switch from interfering with the proper opening and closing movements of the contact or maintaining it between the normal open and closed posi- 4 tions wherein arcing, overheating and other deleterious effects could take place.

Furthermore, the opening and closing movement of fthe switch contact 16 is relatively slow in spite of the fact a fast-moving overcenter mechanism causes such movement. This is due to the camming action of the yoke acting on the contact. As the cam surface wipes over the movable contact strip 16, in an arc, only the component of such action which is perpendicular to the surface of the contact strip acts to move the contact button 16a` away from contact 14C.

Modifications within the scope of the invention will occur to those skilled in the art. Therefore, the invention is not limited to the specific form and detail of the parts as illustrated and described.

What is claimed is:

1. In an electric switch, a housing, fixed contact means mounted in said housing, a exible metallic strip forming movable contact means engageable with and disengageable from said fixed contact means, a pivoted yoke member, an operating member, overcenter-spring means engaged with said yoke member and said operating member to swing said yoke member between two at-rest positions with a snap action as said operating member is moved, cam means on said yoke engaging said movable contact strip and causing movement of said movable contact strip as said yoke member swings, final movement of the contact means into said at-rest positions being free of' control by said operating member, said cam means being formed to move said movable Contact means at a slower rate of speed than said yoke, so as to provide a slow break contact-separating movement.

2. An electric switch as claimed in claim 1 having means pivotally mounting said operating member, and a manually operable member engaging with said pivoted operating member, and means mounting said manual member in said housing for rectilinear movement.

References Cited by the Examiner UNITED STATES PATENTS 2,407,378 9/19'46 Miller et al. 2,623,960 12/1952 Haydon. 2,725,438 11/ 1955 Bentley. 2,881,292 4/ 1959 Winter et al.

ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner.

D. SMITH, IR., Assistant Examiner.

Claims

1. IN AN ELECTRIC SWITCH, A HOUSING, FIXED CONTACT MEANS MOUNTED IN SAID HOUSING, A FLEXIBLE METALLIC STRIP FORMING MOVABLE CONTACT MEANS ENGAGEABLE WITH AND DISENGAGEABLE FROM SAID FIXED CONTACT MEANS, A PIVOTED YOKE MEMBER, AN OPERATING MEMBER, OVERCENTER-SPRING MEANS ENGAGED WITH SAID YOKE MEMBER AND SAID OPENING MEMBER TO SWING SAID YOKE MEMBER BETWEEN TWO AT-REST POSITIONS WITH A SNAP ACTION AS SAID OPERATING MEMBER IS MOVED, CAM MEANS ON SAID YOKE ENGAGING SAID MOVABLE CONTACT STRIP AND CAUSING MOVEMENT OF SAID MOVABLE CONTACT STRIP AS SAID YOKE MEMBER SWINGS, FINAL MOVEMENT OF THE CONTACT MEANS INTO SAID AT-REST POSITIONS BEING FREE OF CONTROL BY SAID OPERATING MEMBER, SAID CAM MEANS BEING FORMED TO MOVE SAID MOVABLE CONTACT MEANS AT A SLOWER RATE OF SPEED THAN SAID YOKE, SO AS TO PROVIDE A SLOW BREAK CONTACT-SEPARATING MOVEMENT.