US3213229A

US3213229A - Plunger operated alternate action electrical snap switch

Info

Publication number: US3213229A
Application number: US288276A
Authority: US
Inventors: Ernest R Carlson; Mackiewicz Czeslaw
Original assignee: Harvey Hubbell Inc
Current assignee: Harvey Hubbell Inc
Priority date: 1963-06-17
Filing date: 1963-06-17
Publication date: 1965-10-19
Anticipated expiration: 1982-10-19

Description

1965 E. R. CARLSON ETAL 3,213,229

PLUNGER OPERATED ALTERNATE ACTION ELECTRICAL SNAP SWITCH Filed June 17, 1963 INVENTORS.

United States Patent 3,213,229 PLUNGER OPERATED ALTERNATE ACTION ELECTRICAL SNAP SWITCH Ernest R. Carlson, Fail-field, and Czeslaw Mackiewicz,

Trumbull, Conn., assignors to Harvey Hubbell, Incorporated, Bridgeport, Conn., a corporation of Connecticut Filed June 17, 1963, Ser. No. 288,276 11 Claims. (Cl. 200-68) This invention relates to an electrical switch and, more particularly, to a pushbutton switch especially suited for alternating current applications.

It has been discovered in practice that the make are developed during switching of alternating current deteriorates switching contacts faster than does the break arc. A fast making speed has been found to minimize arc damage. Conversely, it has been discovered that a slow breaking speed is preferable to a fast breaking speed in the prevention of arc damage. The reasons behind these discoveries are not completely understood; however, the reason for the making phenomenon appears selfevident, viz., reduced time and space for formation and duration of arcing, whereas the reason for the breaking phenomenon appears less clear, but is believed to be that the arc will extinguish itself during a slow break at a minimum separation. If the break occurs at a faster speed, however, the arc becomes larger before it is extinguished by the normal reversal of the alternating current.

Another factor to be taken into consideration in switch development is that, for many residential and commercial lighting applications, the pushbutton switch has become quite popular. This type switch has a single pushbutton element which is depressed to both open and close the circuit. In contrast to the older type toggle switches and double pushbutton switches, switches of this type often lack the force required to break contacts which may have become partially welded during the previous closing stroke.

Accordingly, it is the primary object of this invention to provide an improved pushbutton switch for AC. use. Other objects are to provide such a switch wherein a positive mechanical force may be applied for opening the switch, and to provide such a switch having a relatively slow break speed and a fast make speed. These objects and others are attained by the novel switch mechanism of this invention. The switch of this invention may be most readily understood by reference to the following specification, the appended claims, and the figures of the attached drawing, wherein:

FIG. 1 is a plan view, partially broken away for clarity, of a switch constructed in accordance with this invention;

FIG. 2 is an elevational view, also partially broken away, of the switch of FIG. 1;

FIGS. 3 and 4 are cross sectional views of the switch operating mechanism illustrating the operation of the switch;

FIG. 5 is an isometric View of the operating mechanism of the switch of FIGS. 14;

3,213 ,229 Patented Oct. 19, 1965 portions are combined to provide recesses enclosing the switch mechanism. The housing is enclosed by a cover plate 12 which defines a central opening surrounding a push button 14. Push button 14 is substantially rectangular in horizontal section and includes first and second flanges 14a and 14b which extend beneath the cover plate 12 for retaining the push button 14 in position. The electrical switching contacts are located in a switch chamber formed mainly in housing portion 10b. Housing portion 10a serves as a cover for the switch chamber and also provides an intermediate shelf 16 between the housing portions. The flanges 14a, 14b of the push button are urged upwardly against the cover plate 12 by means of

coil springs

18, 20 which are compressed between the flanges and the shelf 16.

Push button 14 is hollowed out to form an internal V-shaped slot 22 which is bounded by vertical side walls 22a, 221). A pivot pin 24 extends between the side walls 22a, 22b and pivotally supports the end of a T-shaped plunger 26. Plunger 26 is positioned with the cross arm of the T-extending downwardly into the housing of the switch. A central cavity in the housing portion 10a includes a pair of angled shoulders, 28a and 28b, on one side of the T and a similar pair of shoulders on the oppo site side (not shown). Each pair of angled shoulders is so positioned as to contact one end of the cross bar of the T-shaped plunger 26, and thereby serve as stationary cams for centering the plunger as it moves upwardly on the release of the push button, as will be described in more detail infra.

Extending upwardly from base portion 10b and positioned directly beneath the pivot pin 24 are a pair of knife-

edged support members

30a, 30b. The support members 30a, 3012 are spaced apart sufiiciently to allow room for an actuating coil spring 32 to extend between them. Mounted for rotation on the

support members

30a, 30b is a hell crank 34. The bell crank 34 is partially bifurcated to allow sufficient room for clearance from coil spring 32. The construction of the bell crank 34 is most clearly illustrated in FIG. 5 and will be seen to include V notches 36 which are mounted on the knife-edged

support members

30a, 30b. The upwardly extending arm of the bell crank 34 terminates in a pair of elongated V-shaped sockets 34a, 34b. The horizontally extending arm of the bell crank is actually divided into two parallel arms 38a,

38b. The extremities of arms 38a, 38b terminate in a transversely extending actuating bar 40. The ends of actuating bar 40 are slotted, as is clearly shown in FIG. 5. Through these slots extend the ends of the movable

switch contact arms

42, 44. The

switch contact arms

42, 44 carry

movable switching contacts

46, 48 which are arranged to contact either the upper fixed contacts 50 or the lower

fixed contacts

54, 56. The switch contact arms illustrated in FIGS. 1-4 are bent from strip stock so as to.include downwardly curved legs, such as 42', riveted, as by rivet 58 of FIG. 2, to respective contact terminal plates 60. In the embodiment of FIGS. l-4, the switch contact arms are pivotable upward or downward about their bent portions. It is to be understood, however, that the

switch contact arms

40, 42 are not resilient in the sense of being springy. The details of the terminal construction are not required for an understanding of the mechanism of the invention. External wiring connections are made in the usual manner by means of binding screws 62.

As has been previously explained, the actuating coil spring 32 extends in a generally horizontal position between the

support members

30a, 30b and between the horizontal arms 38a, 38b of bell crank 34. One end of the coil spring is secured to the actuating bar 40, as, for example, by being hooked into the first eyelet 90. The

J spring is stretched so as to be under tension and its other end is hooked into a second eyelet 92 which may be formed from a loop of wire anchored securely within the housing 10.

The operation of the invention illustrated in FIGS. 1-5 is as follows: The push button 14 is depressed (FIG. 2), thereby lowering the T-shaped plunger '26 until the cross bar of the T engages the V-shaped socket 34a on bell crank 34. As the button is further depressed to the position illustrated in FIG. 3, it will be noted that the vertical displacement of the push button 14 and plunger 26 has been converted to rotational movement of the bell crank 34. Bell crank 34 rotates in a counterclockwise direction, which raises the actuating bar 40 to the position illustrated in FIG. 3. At this point in the operation cycle, the right hand end of the coil spring 32 has been raised to the point where the center line of the spring passes through the axis of rotation of the bell crank 34. This is, accordingly, the dead center position. At the same time it will be noted that, because the slot in the actuating bar 40' is wider than the thickness of the

switch contact arms

42, 44 the contact arms themselves have not yet been affected. As soon as this dead center position is passed, however, the spring 32 takes over the operation and rotates the bell crank 34 to its extreme counterclockwise position illustrated in FIG. 4. During this interval, the lower edges of the slots in actuating bar 40 contact the

switch contact arms

42, 44 and raise them upward, breaking contact with the lower

fixed contacts

54, 56 and making contact With the upper fixed contacts 50. This position is illustrated in FIG. 4 and it will be noted that the V-shaped socket 34a of the bell crank 34 has moved completely away from the T-shaped plunger 26, solely under the influence of the spring 32. Accordingly, regardless of how slowly the push button 14 may be depressed, the speed with which the movable contact approaches the upper fixed contact is fast and fixed by the spring constants. Further, if tripping of the contact does not occur from spring action, because of prior contact welding, additional pres- .sure on the push button will directly cause such tripping as a result of the direct contact of the lower edges of the slots in actuator 40 with the

contact arms

42, 44 to break the weld. Further still, due to the wide slots, a damping etfect is created which reduces contact bounce on make, as well as causing overtravel which generates increased contact pressure.

At the end of the switching cycle, as illustrated in FIG. 4, it will be noted that the plunger 26 is displaced from the vertical. Upon the release of push button 14, the button is urged upwardly by springs 18, to its original position. As the button rises, one end of the cross bar of the T-shaped plunger 26 contacts the angled shoulder 28a and the other end contacts the similar shoulder (not shown) on the other side of the plunger. These serve to cam the plunger 26 back to a central position. It will now be apparent that, with push button 14 raised and the plunger 26 centered, the cross bar of the plunger T will be directly above the V-shaped socket 34b. Accordingly, a second depression of the push button 14 will cause the bell crank to be rotated in a clockwise direction and will thereby return the switch to its original state. Spring 32 powers the clockwise rotation of the mechanism in the same fashion as the counterclockwise rotation, causing

contacts

46, 48 to close rapidly against contacts 54,

66, they are provided with tongues which are recessed into corresponding grooves 82 in the terminal blocks. In order to retain the knife edges within their corresponding grooves, a positive axial force must be applied to the contact arms. Accordingly, the actuating bar 84 of this embodiment does not include the widely slotted ends of the actuating bar 40. Rather, the actuating bar 84 is closely fitted to the cont-

act arms

64, 66 and abuts against a shoulder 64', 66' provided on each of the arms. Spring pressure from the coil spring 32 is then sufiicient to retain the contact arms in the grooves.

In the FIGS. 6, 7 and 8 modification, the switching mechanism trips free as soon as the push button has been depressed sulficiently to cause movement of the end of the coil spring past its dead center position. Prior to such tripping, the movable switch contacts are directly lifted off the fixed contacts by the actuator 84. This is a relatively slow break, which is desirable, and a direct forceful one which will break any contact weld. However, once the dead center position is reached, the coil spring takes over the operation and pulls the movable contact arms rapidly into the make position regardless of the speed of movement of the push button. It is also important to note that the initial break is actuated by direct mechanical pressure against the push button. The advantage of this is that any slight welding which may have occurred between the closed contacts can be broken by exerting additional pressure on the push button. Accordingly, the switch of this invention will often be operable under circumstances wherein spring operated switches, for example, will remain welded closed.

While the preferred forms of this invention have been shown here, it will be obvious to those skilled in the art that many other variations and modifications may be made in its construction without departing from the spirit and scope of the invention as defined in the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical switch which comprises: a housing; a cover on said housing having an opening therein; push button means positioned within said opening and resiliently retained therein for movement into and out of said housing; elongated plunger means pivotally mounted by a first end on said push button means and having a second end extending into said housing; bell crank means pivotally retained within said housing for rotation between a first and a second position and including a first and a second arm, the first arm of said bell crank means being positioned for engagement by said plunger means upon depression of said push button means to rotate said bell crank means between said first and second positions; switch contact means movable between a first and a second switch position; actuating bar means atfixed to the second arm of said bell crank means for movement therewith and substantially parallel to the axis of rotation of said bell crank means and arranged to actuate said switch contact means between said first and second switch positions; and spring means operable against said actuating bar means to urge said switch contact means into the other of said switching positions.

2. The device of claim 1 wherein the first arm of said bell crank means defines thereon first and second sockets positioned to alternatively receive the second end of said plunger means when in said first and second positions.

3. The device of claim 1 wherein said spring means comprising a tension coil spring having a first end secured to said actuating bar means for movement therewith and a second end secured to said housing, the center line of said spring passing through the axis of rotation of said bell crank means during rotation of said bell crank means between said first and second positions.

4. An electrical switch which comprises: a housing; a cover on said housing defining an opening therein; push button means resiliently retained within said opening for movement into and out of said housing; elongated plunger means pivotally mounted by a first end on said push button means and having a second end extending into said housing; bell crank means pivotally retained within said housing for rotation between a first and a second position and including a first and a second arm, the first arm of said bell crank means being positioned for engagement by said plunger means upon depression of said push button means to rotate said bell crank means between said first and second positions; first and second switch contact arms movable between first and second switch positions; actuating bar means atfixed to the second arm of said bell crank means for movement therewith and substantially parallel to the axis of rotation of said bell crank means, said actuating bar means arranged to displace both of said switch contact arms from either of said first and second switch positions; and spring means operable against said actuating bar means to urge said switch contact arms into the other of said switch positions.

5. The device of claim 4 wherein said actuating bar means com-prises a first slotted end and a second slotted end, each of said switch contact arms passing through the slotted portion of a diiferent one of said slotted ends.

6. The device of claim 5 wherein the width of the slot in each slotted end is greater than the thickness of the corresponding switch contact arm passing therethrough.

7. The device of claim 4 wherein said spring means comprises a tensioned coil spring having a first end secured to said actuating bar means for movement therewith and a second end secured to said housing, the center line of said spring passing through the axis of rotation of said bell crank means during rotation of said bell crank means between said first and second positions.

8. The device of claim 4 wherein said plunger means is substantially T-shaped and includes a cross arm at its second end; and wherein said housing includes stationary cam means positioned to engage said cross arm to urge said plunger means into a central position upon movement of said push button means out of said housing.

9. The device of claim 8 wherein the first arm of said bell crank means defines a first and a second groove thereon, positioned to be alternatively engaged by said plunger means upon inward movement of said push button means to selectively rotate said bell crank means between said first and second positions.

10. The device of claim 4 wherein each of said switch contact arms is substantially L-shaped and flexes about its bent portion into said first and second switch positions.

11. The device of claim 4 wherein each of said switch contact arms includes a pivot end having a knife edge thereon and wherein said housing comprises a first terminal block defining a V-groove therein receiving the knife edge of said first contact arm, and a second terminal block defining a V-groove therein receiving the knife edge of said second contact arm.

References Cited by the Examiner UNITED STATES PATENTS 2,684,418 7/54 Koch 200-453 3,051,810 8/62 Wahlstrom 200-153 FOREIGN PATENTS 896,130 5/62 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

Claims

1. AN ELECTRICAL SWITCH WHICH COMPRISES: A HOUSING; A COVER ON SAID HOUSING HAVING AN OPENING THEREIN; PUSH BUTTON MEANS POSITIONED WITHIN SAID OPENING AND RESILIENTLY RETAINED THEREIN FOR MOVEMENT INTO AND OUT OF SAID HOUSING; ELONGATED PLUNGER MEANS PIVOTALLY MOUNTE BY A FIRST END ON EACH PUSH BUTTON MEANS AND HAVING A SECOND END EXTENDING INTO SAID HOUSING; BELL CRANK MEANS PIVOTALLY RETAINED WITHIN SAID HOUSING FOR ROTATION BETWEEN A FIRST AND A SECOND POSITION AND INCLUDING A FIRST AND A SECOND ARM, THE FIRST ARM OF SAID BELL CRANK MEANS BEING POSITIONED FOR ENGAGEMENT BY SAID PLUNGER MEANS UPON DEPRESSION OF SAID PUSH BUTTON MEANS TO ROTATE SAID BELL CRANK MEANS BETWEEN SAID FIRST AND SECOND POSITIONS; SWITCH CONTACT MEANS MOVABLE BETWEEN A FIRST AND A SECOND SWITCH POSITION; ACTUATING BAR MEANS AFFIXED TO THE SECOND ARM OF SAID BELL CRANK MEANS FOR MOVEMENT THEREWITH AND SUBSTANTIALLY PARALLEL TO THE AXIS OF ROTATION OF SAID BELL CRANK MEANS AND ARRANGED TO ACTUATE SAID SWITCH CONTACT MEANS BETWEEN SAID FIRST AND SECOND SWITCH POSITIONS; AND SPRING MEANS OPERABLE AGAINST SAID ACTUATING BAR MEANS TO URGE SAID SWITCH CONTACT MEANS INTO THE OTHER OF SAID SWITCHING POSITIONS.