US2698369A - Bridging contactor for electric switches - Google Patents

Description

1954 A. M. DAILY ETAL BRIDGING CONTACTOR FOR ELECTRIC SWITCHES Filed June 8, 1953 MDazZy Jase 2Z1 G. vssich LesZerE.H1Z2man United States Patent F BRIDGING, CONTACTOR FOR ELECTRIC SWITCHES Arthur .M. Daily, Joseph 'G. Veatch, Jr., and Lester E. Hileman,Elkhart, Ind., assignors to Chicago Telephone Supply Corporation, Elkhart, Ind., a corporation of Indiana Application June 8, 1953, Serial No. 360,006

7 Claims. (Cl. 200-166) This invention relates to electric switches and has more particular reference to improvements in bridging contactors for single pole single throw switches of thextype disclosed in the copending application of Arthur M. Daily and Mervin B. Arisman, Serial No. 301,116 filedmJuly 26, 1952 now Patent No. 2,660,651, issued November 24, 1953.

As disclosed in said copending application, switches of this type feature compactness; and are used extensively in radio and television apparatus, beinggenerally mounted upon the back of a variable resistance device to be actuated by the rotatable control shaft thereof.

-It has been customary to provide such switches with a bridging contactor bent flatwise to substantially U-shape so as to provideflat-wise flexible arms which are engageable between spaced stationary contacts on the switch base in the closed position of the switch. During closure ofthe switch,the yieldable outer end portions of the arms are forcefully driven or wedged between the stationary contactsso as to engage them with a desirable wiping action and to be so tensioned thereby as to maintain good contact pressure between their contact portions and the stationary contacts in 'the switch closed position.

Heretofore in switches of this type, especially in the smaller sizes thereof considerable diificulty has been experienced in maintaining the proper wiping action between the contacts as well-as engagement'of the necessarily shorter arms of the bridging contactor with the stationary c'ontacts'under the proper degree of tension throughout the life of the switch. The flatwise flexible contactor arms have beenobserved to losetension after thesWitch'hasbeenin operation for some-time, and this phenomenon is believed to result from the over travel of the contactor due-towearing of the cooperating stops defining the switchclosed position. The wearing of these stops, 'of course, allows the bridging contactor to be forcefullydriven or'wedged'progressively farther into the space between the stationary contacts, and eventually results in flexure of the arms beyond their elastic limit. When this occurs, thedesirable wiping action between thebridging and stationary'contacts is largely destroyed, and contact pressure may even'be diminished to a value far below that ordinarily considered essential.

In addition, itis extremely diflicult to form such contactors with consistent accuracy and uniformity by production methods of -manufacture when they are bent flatwise to the desired U-shape. This means, of course, that'there is apt to be considerable variation in such characteristics as contact pressure and wiping action in switches otherwise identical.

With these objections in mind it is the main purpose of'this invention to provide a contactor for single pole single throw switches of the character described in which wearing of the cooperating stops defining the closed position of the switch will have no ill effect upon the flexing characteristics ofthe contactor arms or upon their wiping engagement withthe stationarycontacts under proper spring tension.

More-specifically it is the purpose of thisinvention to providea" bridging contactor for single pole single throw switches of the type herein concerned in which the shape of the contactor may be controlled more accurately than was heretofore. possible by reason of the fact that the majonportion of the contactor is a'flat stamping of substantially .U.-shape, providing contact arms which .fiex edgewiserather than flatwise'as wasthe case inthe past.

, 2,698,369 Patented Dec. 28, 1954 In this connection it is a further object of this invention to provide a bridging contactor having edgewise flexible arms for engagement with a pair of spaced stationarycontacts, and wherein the desireddegree of flexure of the arms is obtained through the expedient of so shaping the generally U-shaped bridging contactor that its arms will have va maximum effective length and spring range while occupying a minimum amount of space within the switch housing.

Still another object of this invention resides in the provision of a bridging contactor for an electric switch having a generally U-shaped configuration, the major portion of the contactor including its bight and the opposing arms. extending therefrom lying in a single plane and having flanges turned up along their remote edges to not only provide contact portions having surfaces normal to the plane of the contactor but to also provide driving lugs on the arms intermediate their ends by which switch opening andclosing motion may be imparted to the .contactor by a suitable contact carrier.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described, and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention constructed in accordance with the best mode so far devised for the practical application of the principles thereof, and in which:

Figure l is a view partly in side elevation and partly in longitudinal section showing an electric switch embodying the contactor of this invention in place on the back of a variable resistor;

Figure 2 is a view looking into the front end of the switch housing, with the switch removed from the variable resistor, and depicting the switch closed position of the bridging contactor;

Figure 3 is a view similar to Figure 2 but illustrating the switch open position of the bridging contactor; and

Figure 4 1s a perspective view of the bridging contactor of this invention.

Referring now more particularly to the accompanying drawing in which like reference characters indicate like parts throughout the several views, the number .5 generally designates an electric switch having the novel contactor 6 of this invention incorporated therein. The switch is shown mounted upon the back wall '7 of the housing 8 of a variable resistor 9 to be controlled by the rotatable operating shaft 10 of the variable resistor.

The shaft projects into the interior of the housing of the variable resistor to terminate a distance ahead of'its rear wall 7, and has a lever 11 fixed to its inner end. A rearwardly bent lug 12 on the lever is engageable with one side or the other of an indentation 13 in the housing to limit back and forth rotation of the operating shaft. The lever also has a driving lug 14 formed thereon to pro-' vide for actuation of the switch 5 in a manner'to'be described later.

The switch 5, as stated, is mounted on. the back of the variable resistor and is enclosed within a housing having a side wall comprised of a cylindrical metal shell 17, and a back wall 18 joined to the rear of the shell and having a large central opening 19 therein to allow the switch terminals 20 to project from the housing and to be accessible at the rear thereof. At its front, the shell 17 abuts the back wall 7 of the variable resistor housing, and the switch housing is secured thereto in a conventional manner as by a series of tangs 22 projecting forwardly from the shell through suitable slits in the end wall 7 and bent over upon the inner face thereof.

The switch includes a circular relatively flat switch base of insulating material 24 fixed in and closing the rear of the switch case, a contact carrier 25 comprising a flat disc of insulating material flatwise overlying and spaced from the inner face of the base a distance sulficient toaccomrnodate the bridging contactor 6'therebetween, the carrier being confined between the base and an actuating member generally designated 26. The actuating member is of the sliding pitman type disclosed in the copending application of Wilkie L. Bush and Arthur M. Daily, Serial No. 255,270 filed November 7, 1951, now Patent No. 2,660,634 issued November 24, 1953.

There are two stationary contacts 28 and 29 on the base, fixed thereto in spaced relation to one another and at opposite sides of the center of the base, and these stationary contacts are preferably provided by the inner ends of combined stationary contact and terminal members clinched or riveted to the base in the manner disclosed in Patent No. 2,524,784 issued October 10, 1950 to A. E. Franks et al.

The stationary contacts 28 and 29 have relatively fiat portions opposite and nearly parallel to one another and lying in zones at opposite sides of and equidistant from the center of the switch base. At one end thereof, shown as uppermost in Figures 2 and 3, the stationary contacts have contact portions 30 formed thereon. These contact portions are of substantially semi-cylindrical shape and have their convex sides normal to the base and facing toward one another, and the space between them is considerably less than that between the relatively flat portions of the stationary contacts. These contact portions 30 are substantially rigid, and are arranged to lie opposite one another along a line spaced above the center of the base. The edges of the stationary contacts which face the underside of the contact carrier 25 lie in a common plane parallel to the inner face of the base, and cooperate with the actuating member 26 to constrain the contact carrier 25 therebetween to edgewise motion in a plane parallel to the inner face of the base.

The bridging contactor 6 of this invention is a flat blanked piece of sheet metal having a generally U-shape. Hence, the major portion of the contactor including its opposite arms 32 and bight 33 are fiat and coplanar; and being stamped from a flat piece of metal can be formed with great accuracy as to its U-shape.

The bridging contactor fiatwise overlies and slides upon the inner face of the base 24, and operates in a central zone thereof between the two stationary contacts 28 and 29, with the extremities of its arms 32 adjacent the contact portions 30 on the stationary contacts and its bight portion 33 adjacent to the opposite ends of the fixed contacts, remote from the contact portions 30 thereof.

The inner end portions 35 of the arms, adjacent to the bight 33 are substantially parallel, while their outer end portions 36 converge toward their extremities. Flanges 38 bent up from the remote side edges of the arms, at right angles thereto, extend from the extremities of the arms inwardly to points near the bight end of the contactor. These flanges provide contact portions on the arms, near their outer ends, which engage between and bridge the stationary contacts 30 during sliding of the contactor substantially lengthwise of its arms, toward the switch closed position as seen in Figure 2.

The arms 32 are flexible edgewise as distinguished from the fiatwise flexure of the arms of conventionally formed contactors, and of course, are flexed toward one another when wedged between the stationary contact portions 30 during closure of the switch. During such closure of the switch, the flanges 38 on the outer end portions of the arms have good wiping engagement with the convex surfaces of the stationary contact portions 30 by reason of the flexure of the arms.

In order to enhance the edgewise fiexibility'of the arms 32 and thus increase their spring range, the bight 33 of the contactor has its center portion 40 bent edgewise inwardly into the space between the arms, in the plane thereof, so that the closed or bight end of the contactor may be said to have substantially sinusoidal curvature. This increases the effective length of the arms 32 and assures that they will have the proper flexing characteristics during the life of the switch. When so constructed, the contactor is not subject to loss of tension as was experienced in the past when the arms of the U-shaped contactor were flexible in a fiatwise direction.

Moreover, the increase in the length of the arms 32 is achieved without addition to the overall dimensions of the contactor or having it take up more room than neces sary inside the switch housing.

Near the junctions of the arms with the bight 33 of the contactor, the upstanding flanges 38 on the remote side edges of the arms are widened, or extended away from the flat plane of the contactor, to provide lugs 42 substantially parallel to one another. These lugs project forwardly through rectangular openings 43 in the contact carrier so as to drivingly connect the bridging contactor therewith.

As stated previously, the actuating member 26 is of the sliding pitman type. At one end the pitman has a stem 45 slidably projecting through a slot 46 in the side wall 17 of the switch housing and cooperating with a pair of lobes 47 at the other end of the pitman slidably projecting through other slots 48 in the side wall 17 of the housing opposite the stem slot to constrain the pit man to reciprocatory motion substantially diametrically across the housing with its stem portion 45 lying in a plane containing the axis of the housing and passing midway between the stationary contacts 28 and 29. The actuating member or pitman overlies the front face of the contact carrier 25 and thus confines the same to edgewise motion in a plane parallel to the inner face of the base 24, in the space between the pitman and the adjacent edges of the stationary contacts 28 and 29.

The pitman has a driving lug 50 on its stem 45 projecting rearwardly through a relatively close fitting aperture 51 in the central portion of the contact carrier to constrain the latter to reciprocate with the pitman. At the upper end of the pitman a stop lug 52 formed thereon between the lobes 47 is bent rearwardly out of the plane of the lobes, and is engageable with the adjacent inner surface of the side wall 17 of the switch housing to define the switch closed position seen in Figure 2. An additional function of the stop lug 52 is thatsince it is engaged in a shallow notch 53 in the periphery of the contact carrier, it prevents rotary movement of the carrier about the driving lug 50 on the pitman.

In this way the bridging contactor 6 on the contact carrier may be driven back and forth along a perfectly straight path toward and from a switch closed position at which the flanges 38 on the outer end portions of the contactor arms are wedged between the contact portions 30 of the stationary contacts with substantially equal contact pressure between the arms and their stationary contacts, and with substantially balanced wiping action assured during closure of the switch.

In the switch open position seen in Figure 3 the driving lug 14 on the lever 11 fixed to the operating shaft of the variable resistor has been carried over the high point 55 of a cam 56 on the pitman, and engages the cam to hold the pitman as well as the contact carrier and the bridging contactor 6 thereon in the switch open position, against the expansive force of a compression spring 57 encircling the stem 45 of the pitman and confined between the cam 56 thereon and the side wall 17 of the switch housing.

When it is desired to actuate the switch to the closed position, the operating shaft 10 is rotated in a direction to carry the driving lug 14 clockwise as seen in Figure 3 and as it passes over the high point 55 of the cam, it suddenly releases the pitman and effects spring propulsion of the contactor to the switch closed position seen in Figure 2, thus effecting bridging of the contactsv with a snap action. Opening of the switch is accomplished by rotation of the operating shaft in the opposite direction (counterclockwise) causing the driving lug 14 to engage and ride up the inclined surface 58 of the cam and thus effect rapid opening of the switch during a relatively short angle of rotation of the operat+ ing shaft.

It will be understood, of course, that the cam is bent from the forward end portion of a flange 60 extending rearwardly from the upper end portion of the stem 45 and projecting forwardly through a hole 61 in the back wall 7 of the housing 8 of the variable resistor, so that the cam 56 is positioned fiatwise adjacent to and behind the lever 11 on the operating shaft.

From the foregoing description taken together with:

sired flexing characteristics, through the particular design of the U-shaped contactor, without increasing its overall dimensions; and that the extra metal in the neighborhood of the contact portions on the contactor arms results in an additional safety factor for heat dissipation.

What we claim as our invention is:

1. A substantially U-shaped bridging contactor for an electric switch: characterized by the fact that the major portion of the U-shaped contactor, including its bight and the opposite arms extending therefrom, lies in a single plane, said arms being edgewise flexible toward and from one another; and further characterized by the fact that flanges struck up from the remote edges of the arms provide contact portions on the arms near their outer ends having surfaces substantially normal to said plane and extending lengthwise of the arms for engagement with stationary contacts to be bridged.

2. A substantially U-shaped bridging contactor for an electric switch: characterized by the fact that the major portion of the contactor, including its bight and the spaced arms extendihg therefrom, lies in a single plane, said arms being edgewise flexible toward and from one another; and further characterized by the provision of means on the arms providing contact portions thereon near the outer ends of the arms and having surfaces substantially normal to said plane and extending lengthwise of the arms for engagement with stationary contacts to be bridged.

3. The contactor set forth in claim 2 wherein the intermediate portion of the bight is curved edgewise inwardly into the space between the arms to give the same a greater eflective length and spring range.

4. The bridging contactor set forth in claim 2 further characterized by the provision of flanges struck up from said arms at locations intermediate said contact portions on the arms and the bight of the contactor, said flanges providing driving lugs by which switch opening and closing motion may be imparted to the contactor.

5. The contactor set forth in claim 4 wherein the flanges which provide the driving lugs are struck up from the remote edges of the arms and have continuations of reduced height extending along said remote edges of the arms to their outer ends and providing said contact portions on the arms.

6. The contactor set forth in claim 5 further characterized by the fact that the bight of the contactor is curved edgewise inwardly into the space between the arms to give the latter a greater effective length and spring range.

7. The contactor set forth in claim 6 wherein said arms converge toward their outer ends.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,911,811 Coote May 30, 1933 2,177,284 Schellenger Oct. 24, 1939

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