US2836667A - Electric switch - Google Patents

Description

y 27, 1958 w. A. BARDEN ET AL 2,836,667

ELECTRIC SWITCH 2 Sheets-Sheet 1 Filed Oct. 29. 1956 Wayne A.E7arden DunaZd A.P'LEI :2

May 27, 1958 W. A. BARDEN EI'AL ELECTRIC SWITCH 2 Sheets-Sheet 2 Filed Oct. 29, 1956 WayneA 170125227 .Barde n .Fze'rce United States Patent ELECTRIC SWITCH Wayne A. Bar-den, Elkhart, and Donald A. Pierce, South Bend, Ind, assignors to Chicago Telephone Supply Corporation, Ellrhart, Ind., a corporation of Indiana Application October 29, 1956, Serial No. 618,747

13 Claims. (Cl. 200-46) This invention relates to electric switches of the type used in radio and television apparatus and generally mounted on the back of a variable resistor to be actuated by the rotatable control shaft of the resistor. More specifically, the invention concerns switches of the socalled pitman type like that of Patent No. 2,660,634, issued November 24, 1953. Small over all size and reduced cost are objectives always sought in controls for radio and television apparatus, and especially in switches designed for use in combination with variable resistors. Accordingly, the chief purpose of this invention is to provide a switch of the character described, in which these objectives are attained to an unprecedented extent.

To illustrate how completely the present invention meets the demand for reduction in size, the entire mechanism of the switch, although it is of the two pole single throw type and has four stationary contacts and terminals and two movable bridging contacts, is contained within a housing only three-quarters of an inch in diameter and one-quarter of an inch in depth or thickness. Hence, when this switch is mounted in tandem upon the back of a variable resistor, the housing of which has a like diameter, the entire combination control, namely, switch and resistor, occupies a space not much greater than five-eighths of an inch long by three-quarters of an inch in diameter. Controls of this small size are aptly characterized as miniaturized.

it is self evident that in a unit as small as this the problem of providing adequate electric clearance between the ditferent switch terminals and the switch parts, and of obtaining good contact between the movable and stationary contacts, and at the same time assuring adequate separation between the contacts when the switch is open, presents a problem of considerable magnitude especially where the switch is of the double pole single throw type.

This invention solves this problem through the provision of a novel molded switch housing or body and a novel manner of assembling the contacts and terminals, and the movable contactor mechanism in this housing.

Another feature of this invention is the ease with which its various parts are assembled.

Still another feature of this invention is the fact that when the switch is mounted upon the back of a variable resistor, the rear Wall of the resistor not only serves as one of the Walls of the switch housing but in addition coac'ts with the specially formed switch body to hold the movable parts of the switch in proper assembled relation.

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 drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view in longitudinal section through an electric switch embodying this invention, and illustrating the same mounted upon the back of a variable resistor;

Figure 2 is a cross sectional view through Figure 1 on the plane of the line 22, said view being essentially a front view of the switch and illustrating the switch in its closed condition;

Figure 3 is a view similar to Figure 2 but showing the switch in its open condition;

Figure 4 is an exploded perspective view of the various 9 parts of the switch;

Figure 5 is a perspective view of the rear end of a variable resistor housing of the type adapted to have the switch of thisinvention mounted thereon; and

Figure 6 is a detail cross sectional view through Figure 4 on the plane of the line 66.

Referring now to the accompanying drawings, in which like numerals indicate like parts throughout the several views, the numeral 5 designates generally the switch of this invention, shown mounted upon the back of a variable resistor 6, so as to be operable by the rotatable control shaft 7 of the resistor.

The variable resistor 6 may be of any conventional construction since it forms no part of this invention except to the extent that the rear wall 8 of its stamped metal cover serves to close the front of the switch housing 9 and actually holds the movable elements of the switch in proper assembled relation within the switch housing, as will be hereinafter more fully described.

It is of course to be understood that the variable resistor 6 includes an arcuate resistance element 10 mounted upon a suitable base 11 concentrically with the control shaft 7, to be transversed by a rotatable contactor 12 which is drivingly connected to the control shaft by means of a stop plate 13, rigidly secured to the rear end of the shaft. The stop plate 13 is a metal stamping and has alug 14 extended rearwardly to coact with a fixed stop 15 in the side of the resistor cover and define the limits of rotation of the contactor.

A second lug 16 also extended rearwardly from the stop plate 13 coacts with a cam 17 which forms part of the switch actuator designated generally by the numeral 18 to open the switch during the last few degrees of rotation of the contactor as it approaches one limit of its permitted rotation. This manner of actuating the switch is similar to that employed in the aforesaid Letters Patent No. 2,660,634, and since the actuator 18 is constrained to rectilinear motion, these switches have become known as pitman type switches.

It is to be observed that the cam 17 on the switch actuator is inside the cover or housing of the variable resistor, and that it enters the same through an opening 19 in the back wall 8 of the cover. Part of the metal removed to provide the opening 19 forms a pair of diametrically opposite tangs 20 which extend straight back from the cylindrical side wall of the variable resistor housing to embrace the housing or body 21 of the switch and be folded over the rear thereof to secure the switch to the resistor. The housing or body 21 of the switch is molded of suitable insulating material and preferably has a pair of diametrically opposite notches 22 in its sides to receive the tangs 20 to assure proper orientation between the switch and the resistor.

The housing or body 21 is cup-shaped and has a sub stantially cylindrical cavity 23 opening to its front, the cavity being defined by a rear wall 24 and a substantially cylindrical side wall 25 extending rforwardly from the rear wall around the peripheral edge thereof. A rib 26 formed integrally with the rear wall 24 extends forwardly therefrom diametrically across the cavity 23, and at one end of this rib the housing has a lateral projection or boss 27.

The front surface 28 of the rib 26 lies in a single plane spaced forwardly of and substantially parallel to therear wall 24, and extending longitudinally down the center of the rib and bisecting the same is a groove 29. For the major length thereof the groove 29 is of uniform depth with its bottom coplanar with the inner face of the rear wall 24, but at the end of the groove adjacent to the boss or enlargement 27 the depth thereof is considerably less so that a shoulder 30 is formed at that end of the groove. Both ends of the groove open to the exterior of the housing side Wall.

From a point adjacent to and slightly inward of the shoulder 30 and to a point near the center of the housing the groove 29 is widened to provide a pocket 31 in which a coiled spring 32 is received. This spring is confined between the inner end 33 of the pocket 31 and an arm 34 on the switch actuator which is slidably received in the groove 29, to bias the switch to its closed position.

As will be readily seen tfrom Figures 4 and 6, the rib 26 substantially divides the interior of the cavity 23 into two compartments. In each of these there is a pair of spaced stationary contacts 35 and a movable bridging contactor 36 All of the stationary contacts 35 are substantially alike, and each comprises a resilient switch blade 37, a terminal end portion 38, and a medial mounting portion 39. The mounting portion 39 projects laterally beyond the adjacent edge of the contact and passes through a slot'40 in the rear wall 24 to be staked over as at 41 and anchor the combined contact and terminal with its terminal end portion 38 extending through a slot 42 in the end wall of the enlargement or boss 27, and its resilient switch blade 37 spaced slightly forwardly and hence free of the rear wall 24. Thus each pair of switch blades will flex freely as its contactor 36 moves therebetween, and to facilitate entry of the movable contactors between the pairs of switch blades, the outer extremities of the blades are flared as at 43.

The front face 28 of the rib 26, as noted hereinbefore, lies in a single plane substantially parallel to and forwardly of the rear wall 24. It is also slightly forward of the adjacent edges of the resilient switch blades. Hence, the surface 28 is admirably adapted to provide a track or guideway fora contactor carrier 44. This carrier is stamped from a fiat piece of insulating material and is of a size and shape to fit within the cavity 23 and allow edgewise motion of the carrier lengthwise across the front surface 28 of the rib, an amount necessary to bring both contactors 36, which are fixed thereto, into switch closing bridging engagement with their respective pairs of stationary switch blades, and to carry the contactors 36 far enough from the ends of the switch blades to assure adequate electrical clearance when the switch is in its open position shown in Figure 3.

Switch opening and closing motion is imparted to the carrier 44 by the actuator 18 and to this end the actuator has a driving connection with the carrier. This driving connection is provided by the engagement of the laterally projecting arm 34 on the actuator and a similar though wider arm 45 in notches 46 and 47 formed in opposite edges of the contactor carrier. These notches are so disposed that a line bisecting both notches also bisects the center-to-center distance between the movable contactors 36 and is normal to a line connecting their centers.

Attention is directed to the fact that the edge of the carrier in which the notch 47 is located is arcuate to permit the carrier to approach very closely to the adjacent side wall 25, and that the notch 46 is formed in a tongue 48 which projects from the adjacent edge of the carrier and is adapted to enter a. recess 49 in the enlargement or boss 27. In this manner, maximum travel for the contactor carrier is provided within a minimum space.

The arms 34 and on the actuator 18 are spaced apart a distance to snugly embrace the portion of the contactor carrier lying between the bottoms of the notches 46 and 47, and since the arms 34 and 45 are considerably longer than the thickness of the carrier they project beyond the rear face of the carrier which is slidably seated upon the rib 26 to extend into the groove 29. This engagement of the arms 34 and 45 in the groove 29 guides the actuator 18 and the contactor carrier and constrains these connected elements to rectilinear motion. This guidance is especially provided by the reception of the wider arm 45 in the groove 29, not only because of the increased width of the arm 45 but also because for the major portion of its width the arm 45 is at times received in the groove 29.

Since, as explained hereinbefore, the arm 34 has one end of the spring 32 hearing thereon, the connected actuator and contactor carrier are biased to the switch closed position shown in Figure 2. This switch closed position of the parts may be determined by the extent to which the spring 32 drives the contactors 36 between their respective pairs of stationary contacts or switch blades, but in any event is positively defined by the engagement of the narrow arm 34 with the shoulder 30 at the adjacent end of the deep portion of the groove 29.

The end portion 50 of the actuator which extends beyond the arm 34 is, of course, slidably received in the adjacent shallower end 29' of the groove.

The width of the actuator 18, that is, the distance between its front edge 51 and the rear edge 52 of its arms 34 and 45, is substantially equal to the full depth of the groove 29. Hence, the front edge 51 of the actuator is substantially coplanar with the front edge of the housing side wall 9. Therefore, when the switch is mounted on the back of the variable resistor, as shown in Figure l, the actuator 18 is held down in the groove 29 by the rear wall 8 of the resistor housing. In other words, the resistor housing wall 8 not only coacts with the rear and side walls of the switch housing to complete an enclosure for the switch instrumentalities, but also serves to hold the movable switch parts in position.

In this connection, it should be noted however, that the assembly of the movable switch parts into the switch housing is easily and simply elfected, and that barring rough treatment these movable switch parts will remain in place even though the switch is not yet assembled with the resistor.

The manner in which the lug 16 which rotates with the contactor of the variable resistor coacts with the cam 17 of the switch actuator to open the switch and hold it open forms no part of the present invention and in fact is substantially like the aforesaid Letters Patent No. 2,660,634. Description thereof is probably unnecessary, but it may be helpful to point out that the cam and the rest of the actuator 18 is one stamped and formed unit, and that the apex of the cam is so disposed with respect to the orbit of the lug 16 that during the final few degrees of rotation of the control shaft to bring the contactor of the resistor to the end of its travel at which maximum resistance is in the circuit, the lug 16 snaps over the apex of the cam and thus pro vides a desirable snap action for the switch both during opening and closure.

From the foregoing description taken in connection with the accompanying drawings it will be readily apparent to those skilled in this art that this invention provides a switch of extremely simple and inexpensive construction and that it enables miniaturizing the switch without danger of sacrificing adequate electrical clearance between the various circuit carrying portions of the switch, and without sacrificing good performance.

What is claimed as our invention is:

1. An electric switch of the character described comprising: a body of insulating material having a cavity opening to its front and defined by a back wall and a side wall of substantially uniform height projecting forwardly from the back wall; a rib integral with the back wall and projecting into the cavity, said rib dividing the cavity into two compartments one at each side of the rib, the front of the rib lying in a plane substantially parallel to the rear wall but rearwardly of the front edge of the side wall and providing a guideway; a pair of stationary switch contacts in each of said compartmcnts of the cavity; a movable contactor carrier slidably seated on the guideway provided by the front of the rib and slidable lengthwise therealong, said carrier having no part thereof forwardly of the front edge of the side wall; movable contactors on said carrier, one

inside each of said compartments, said contactors being insulated from one another and movable by the carrier into positions at which each bridges one pair of stationary contacts; and means for sliding the contactor carrier along the rib.

2. The switch of claim 1 further characterized by the provision of a pocket in the back wall of the body of insulating material in open communication with the groove in the rib; a spring in said pocket; and a part on the actuator entering the pocket and operatively connected with the spring, so that the spring yieldingly urges the actuator and the contactor carrier to a predetermined position.

3. The switch of claim 2 further characterized by the fact that the pocket is a widened portion of the groove; and by the fact that the contactor carrier covers the pocket and thus coacts with the walls of the pocket to provide an enclosure for the spring.

4. The switch of claim 1 wherein the means for sliding the contactor carrier along the rib comprises an actuator overlying the contactor carrier and having spaced apart arms embracing a portion of the carrier to thereby drivingly connect the actuator with the carrier; and a spring connected between one of said arms of the actuator and a portion of the rear wall to bias the actuator and consequently the contactor carrier in one direction.

5. The switch of claim 4 further characterized by the fact that the contactor carrier is constrained to rectilinear motion along the rib by a part on the actuator projecting rearwardly beyond the carrier and slidably received in a longitudinal groove extending lengthwise of the rib.

6. An electric switch of the character described comprising: a body of insulating material having a cavity opening to its front and defined by a rear Wall and a side wall extending up from the edge of the rear wall, the side wall being of substantially uniform height so that its edge lies in substantially a common plane parallel to the rear wall; a rib formed integrally with the rear wall and bisecting the cavity, the front of the rib lying in a plane between that of the front edge of the side wall and the rear wall, so that the front of the rib provides a guide surface parallel to the rear wall and inwardly of the front edge of the side wall, said rib having a longitudinally extending groove which opens to the front of the rib; a contactor carrier slidably seated upon said guide surface provided by the front of the rib, said contactor carrier having a thickness less than the difference in height of the side wall and rib so that the contactor carrier lies within the cavity; an actuator for the contactor carrier overlying the front thereof; means drivingly connecting the actuator with the carrier, said means including spaced arms on the actuator projecting rearwardly through and beyond the carrier and into the groove in the rib, so that said means for drivingly connecting the actuator with the carrier also guides said parts for rectilinear motion along the rib; and cooperating stationary and movable contacts respectively carried by the rear wall of the housing and said contactor carrier at opposite sides of the rib.

7. An electric switch comprising: a shallow cup-shaped housing formed of insulating material and adapted to be mounted upon the back of a small variable resistor with the back wall of the resistor extending across the open front of said housing; a pair of stationary switch contact members anchored to the rear wall of the housing in spaced apart opposing relationship and with portions thereof forming resilient switch blades adapted to be resiliently flexed across the rear wall towards and from one another, each of said contact members having a terminal portion extended therefrom through a wall of the housing; a movable contactor of a size to move between and spread apart the free ends of said switch blades, to thereby electrically bridge the stationary contact members; a movable contactor carrier within the housing and to which said movable contactor is secured; and means guiding the carrier for rectilinear motion across the stationary contact members in a direction to carry the movable contactor to and from its bridging position, said guiding means including an actuating member having driving connection with the carrier and overlying the same to be interposed between the carrier and the rear wall of a resistor upon which the switch is mounted.

8. An electric switch comprising: a base of insulating material; a rib integral with said base and extending across the front face thereof, said rib having a longitudinally extending groove therein opening to its front; a boss integral with the base and with one end of the rib, said boss projecting to opposite sides of the rib, and having a pair of slots therethrough at each side of the rib, parallel to the rib and opening to the front of the boss; an elongated stationary contact seated in each of said slots with a free end portion thereof projecting from the boss and over the base to provide a yieldable blade so that a pair of said blades is located at each side of the rib; a contactor carrier slidably seated upon the front of the rib and overlying said yieldable blades to hold the stationary contacts in their respective slots; a contactor on the carrier at each side of the rib positioned to have bridging engagement with the pair of blades at said side of the rib; an actuator for the carrier; a driving connection between the actuator and the carrier; and guide means on the actuator slidably received in said groove in the rib to constrain the actuator, carrier and contactors to rectilinear motion.

9. The electric switch of claim 8, wherein the driving connection between the actuator and the contactor carrier and also the guide means comprises spaced apart arms on the actuator projecting laterally therefrom in the same direction and embracing a portion of the carrier with the end portions of said arms extending beyond the rear of the carrier and slidably received in the groove.

10. The electric switch of claim 9 further characterized by the fact that the rib has a pocket therein provided by a widened portion of the groove; and a spring in said pocket confined between one of the arms on the actuator and the opposite end of the pocket to bias the actuator, carrier and contactors in one direction.

11. As an article of manufacture, a housing and body for an electric switch comprising a unitary molding of insulating material having a shallow cup-shaped formation with a substantially fiat end wall and a substantially cylindrical side wall; a rib integral with the back wall substantially bisecting the interior of the housing and dividing it into two compartments, one at each side of the rib; the rib having a longitudinal groove extending down its middle and opening to its front, said groove being widened for part of its length to provide a spring receiving pocket; a plurality of slots through a part of the side wall, all of said slots being parallel to the groove; and the end wall having an opening therethrough in line with each of said slots.

12. The switch housing and body of claim 11, further characterized by the fact that the portion thereof at which the slotted part of the side wall is located, has an outwardly projecting boss thereon which places the slotted part of the side wall radially farther from the center of the housing than the rest of the side wall.

13. A switch comprising: a body of insulating material having a cavity opening to its front and defined by a rear wall and a side wall projecting forwardly from the edge of the rear Wall; a rib integral with the rear and side walls bisecting the cavity, said rib having a longitudinally extending slot opening to its front edge; the side Wall having a pair of adjacent slots therethrough parallel to the rib at each side thereof and opening to the front edge of the side wall; an elongated stationary contact and terminal member received in each of said slots With a free end portion thereof in the cavity to provide a yieldable blade and its opposite end. outside the cavity to provide a terminal; a contactor carrier of insulating material slidably seated upon the front edge of the rib and projecting to opposite sides thereof to overly the yieldable blades; a bridging contactor on the carrier at each 8 side of the rib positioned to havebridging engagement with the pair'of blades at said side of the rib upon switch closing motion of the carrier; and means to constrain the contactor carrier to rectilinear motion along the rib comprising a part connected with the carrier and slidably received in said slot in the rib.

References Cited in the file of this patent UNITED STATES PATENTS 1,340,788 OHara May 18, 1920 2,174,410 Badeaux Sept. 26, 1939 2,484,734 Rahmel Oct. 11, 1949 FOREIGN PATENTS 133,030 Switzerland July 16, 1929 141,155 Switzerland Sept. 16, 1930

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