Patent Publication Number: US-3968338-A

Title: Electrical switch control

Description:
The present invention relates to electrical controls, and more particularly, to an electrical switch used singly or in combination with a variable resistance control and to a plurality of such switches connected in tandem. 
     Prior art switches such as disclosed in U.S. Pat. Nos. 3,349,358 and 3,324,261 use a contact spring actuated by a cam and pivoted about a first contact member to open and close the electrical connection between the first contact member and a second contact member. In such switches the cam is connected through an actuator to a shaft turning in a bearing carried by a housing. As the cam engages and flexes the contact spring, the contact spring exerts spring pressure on the cam which pressure in turn is exerted on the shaft and against the bearing in the housing. A small diameter shaft rotating in a small diameter bearing causes a rather small bearing surface to withstand the spring pressure. Further increases in spring pressures by the cam moving in engagement with the contact spring are rather abruptly manifested at the bearing by the tight engagement of the shaft and bearing surface. This abrupt change in pressure or tight engagement is evidenced by abrupt switch action. It would therefore be desirable to provide a switch device evidencing less abrupt change in pressure and better switch feel as the cam engages the contact spring. 
     In the above mentioned U.S. Pat. No. 3,349,358 the cam is carried in close relationship to the rotating shaft resulting in more rapid angular turn per rotational travel of the cam with respect to the contact spring. Thus the alignment of the cam with respect to the cam follower of the contact spring is more critical for proper engagement of the cam with the cam follower, and to provide uniform spring pressure on the cam in both directions of cam movement. If the cam is positioned more radially outwardly from the rotating shaft as shown in the above mentioned U.S. Pat. No. 3,324,261, the angular rotation takes place over a greater range of cam travel; however, the further the cam is located from the center of the shaft, the greater the cam wobble or less stable is the cam movement with respect to the contact spring. It would therefore be desirable to provide a switch device wherein the cam is relatively free from wobble and yet there is a wide range of cam travel with respect to the contact spring. 
     In the above mentioned U.S. Pat. No. 3,349,358 the contact spring is biased between two separate contact members. The tolerance between two separate parts between which the contact spring is biased creates difficulty in providing a consistent contact pressure. This problem has been alleviated in the single-pole single-throw switch shown in above mentioned U.S. Pat. No. 3,324,261 by biasing the contact spring between a slot and a groove in the same contact member. However, in the above mentioned patent, the portion of the contact spring making electrical contact with each of the two contact members of the switch is the same portion of the contact spring mechanically engaged by the cam to pivot the contact spring into and out of engagement with the two contact members. Thus the same portion of the contact spring is both electrically and mechanically degradable and therefore decreases the life of the contact spring. It would therefore be desirable to provide a switch device in which the bias on the contact spring is essentially provided by a single contact member and wherein electrical and mechanical degradation of the contact spring is minimized. 
     Some switch applications often require a plurality of switch devices in tandem wherein each of the switch actuators of the switch devices rotates simultaneously. In such switch applications to prevent unnecessary malfunctions in the individual switch devices, it is often necesssary that the electrical contacts of each of the devices be electrically isolated in enclosed housings. It would therefore be desirable to fabricate a tandem switch control wherein a plurality of switch actuators are mechanically interconnected for simultaneous activation and wherein each of the actuators provides a cover plate for its respective housing. 
     Accordingly, it is an object of the present invention to provide a new and improved electrical control having the desirable features set forth above. 
     Still another object of the present invention is to provide a cam disposed near the periphery of a switch actuator for engaging a contact spring wherein the periphery of the actuator is rotatably supported in a housing. 
     Another object of the present invention resides in a new and improved contact spring minimizing electrical and mechanical degradation thereof and biased between points on a first contact means into engagement with a second contact means. 
     Still another object of the present invention is to provide a single-pole double-throw switch wherein a contact spring is biased between a post member and an abuttment member integral with a first contact and the ends of the contact spring are bent about the post member in stacked relationship. 
     Yet an additional object of the present invention is to provide a new and improved tandem switch control wherein first and second switch housing sections define cavities closed by interconnected switch actuators secured to an operating means for simultaneous rotation thereof. 
     Still a further object of the present invention resides in a tandem switch control wherein a first housing section defines a cavity and is provided with a peripheral annular bearing and the periphery of a switch actuator closing the cavity rotatably engages said bearing. 
     Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification. 
     Briefly, the present invention is concerned with a switch device used singly or in combination with a variable resistance control or another switch. Each switch housing section defines a cavity and is provided with an annular bearing rotatably supporting the periphery of a disk shaped switch actuator. The switch actuator closes the cavity and carries a cam near the periphery movable in an interference path with respect to a contact spring disposed in the housing. Each housing section carries a common contact means disposed intermediate first and second contact means and the contact spring defines a loop with the end portions thereof pivotally bent in stacked relationship about a post integral with the common contact means. The contact spring is biased between the post and an abuttment member integral with the common contact means into contact with the first and second contact means. Integral with each of the end portions of the contact spring is a U-shaped member. The cam engages the bight portion of the U-shaped member for moving the legs of the U-shaped member into and out of engagement with the first and second contact means. Extending from a first surface of the switch actuators are projecting lugs for interlocking with lug receiving notches carried by a second surface of the switch actuators. Rotation of a control shaft engaging the lug receiving notches of a switch actuator rotates each of the cams of interlocked switch actuators in an interference path with respective contact springs. 
    
    
     For a better understanding of the present invention, reference may be had to the accompanying drawings, wherein the same reference numerals have been applied to like parts and wherein: 
     FIG. 1 is an isometric view of a tandem electrical switch in combination with the variable resistance control, built in accord with the present invention; 
     FIG. 2 is a partial sectional view taken along lines II--II of the electrical component shown in FIG. 1; 
     FIG. 3 is an exploded isometric view of the tandem electrical switch and a portion of the variable resistance control shown in FIG. 1; 
     FIGS. 4 and 5 show one of the switches of the tandem electrical switch of the electrical component of FIG. 1 in first and second stable positions. 
    
    
     Referring now more particularly to the drawings, an electrical component embodying one form of the invention is generally identified by the reference numeral 10. As shown in FIG. 1, the electrical component comprises a variable resistance control 11 and switches 12 and 12a comprising switch housing sections 13 and 13a molded of suitable plastic material. It should be understood that either of the switches 12 and 12a could be used singly or in tandem with any suitable electrical control and the switches are shown in combination with the variable resistance control for illustrative purposes only, the variable resistance control forming no part of the present invention. A control means 14 of brass or other suitable material includes a control shaft 16 supported by the front insulating base or plate 18 fixedly secured against the housing 11a of the variable resistance control 11. One of the means for mounting the electrical component 10 to a not shown mounting panel comprises a ground plate 22 provided with an externally threaded bushing 24 rotatably supporting the control shaft 16. After the threaded bushing 24 is inserted through a mounting panel, a lock washer and nut are used to lock the component into place on the panel. A coupling plate 36 suitably secured to the housing 11a is provided with integral coupling straps 40 for securing the switch housing sections 13 and 13a to the variable resistance control 11. Each of the housing sections 13 and 13a defines a cavity 44 and 44a and is provided with diametrical channels 46 and 46a for receiving the coupling straps 40. The coupling straps 40 each have end portions 48 suitably deformed to secure the housing sections 11a, 13 and 13a together. Housing section 13 being an intermediate section is provided with an aperture 45 to be hereinafter described. 
     In accordance with the present invention, each of the cavities 44 and 44a is closed by a disk shaped actuator 50 and 50a respectively molded of a suitable dielectric material and each of the actuators comprising a pair of spaced parallel surfaces 51 and 51a and 52 and 52a. Since the switch actuators are identical only portions of each switch actuator will be described in detail. As best seen in FIG. 3, carried integrally on the parallel surface 51, is a wedge shaped cam 54 disposed near the periphery of the switch actuator and a tubular portion 56 extends from the center of the switch actuator 50 terminating in a pair of lugs 58. Each of the surfaces 52 and 52a is provided with a center notch 59a and protrusions 60a extending from the surface 52a providing lug receiving notches 62a. The lugs 58 on the tubular portion 56 extend into the aperture 45 in the housing section 13 and engage the lug receiving notches 62a to secure the switch actuator 50a to the switch actuator 50. A projection 65 disposed at the end of the shaft 16 as seen in FIG. 3 engages the not shown lug receiving notches and center notch in surface 52 to secure the switch actuator 50 to the shaft 16. Rotation of the shaft 16 therefore rotates switch actuators 50 and 50a and their respective cams simultaneously within cavities 44 and 44a. In order to insure that the switch actuators 50 and 50a are properly positioned, one of the lugs is larger than the other thereby insuring entry into the lug receiving notches in only one position. It should be understood that the projection 65 at the end of the shaft 16 and the lugs on one surface of the switch actuators interfit the lug receiving notches on the other surface of the switch actuators so that individual switches can be interchanged and stacked still enabling simultaneous actuation of the switch actuators by rotation of the shaft 16. 
     Since each of the switches 12 and 12a are identical, only switch 12 will be described in detail. Housing section 13 comprises a back wall 66 with a rim 68 depending therefrom. The rim 68 terminates in an annular ledge 64 and an adjacent wall or ridge 64a normal to the ledge 64 forms an annular bearing. In accord with the present invention, the periphery of the disk shaped actuator 50 is rotatably supported by the annular bearing carried by the housing section 13. Specifically, as seen in FIGS. 2 and 3 the annular ledge 64 is disposed about the periphery of the housing section 13 and supports switch actuator 50 seated thereon with the periphery 53 of switch actuator 50 disposed adjacent wall 64a. First and second terminals 70 and 72 and common terminal 74 extend through suitable slots in the rim 68 with portions of terminals 70, 72 and 74 embedded in slots below the surface of the back wall 66. Integral with terminal 70 is a contact member 70a projecting above wall 66 within cavity 44 and integral with terminal 72 is a contact member 72a disposed opposite contact member 70a within cavity 44. The relationship of contact member 72a with respect to contact member 70a is illustrated in FIGS. 4 and 5 to be described hereinafter. As seen in FIGS. 2 and 3 a contact member or post 75 and an abuttment member 76 are integrally connected to terminal 74 and also project above wall 66. Portions of the housing sections 13 are heat swaged against the terminals 70, 72 and 74 in the slots to secure the terminals to the housing. As seen in FIGS. 2 and 3 a contact spring 82 is compressed between post 75 and abuttment member 76. The compression of contact spring 82 between post 75 and abuttment member 76 biases the contact spring 82 into contact with either contact member 70a or 72a as seen in FIGS. 4 and 5. The contact spring is preferably in the shape of a loop as seen in FIGS. 2 and 3 with two ends 83 and 83a pivotally secured in stacked relationship to the post 75. Integral with each of the ends 83 and 83a is a U-shaped portion 84 having a bight or cam follower segment 85 and legs 86 and 87. 
     For the purpose of shifting the contact spring 82 slideably into and out of engagement with the contacts 70a and 72a, the cam 54 is provided with cam surfaces 55 and 57 movable in an interference path with the cam follower segment 85 of the contact spring 82. Assuming the switch is in the position as shown in FIG. 4, i.e., the contact spring 82 in engagement with the contact 72a, rotation of the cam 54 in a clockwise direction causes the surface 55 of the cam to engage the cam follower segment 85 and continued clockwise rotation of the cam 54 forces the cam follower segment upwardly toward post 75 causing the contact spring to compress and thereby store energy. The energy stored in contact spring 82 engaging the cam 54 is transmitted radially outwardly through the cam 54 to the switch actuator 50 engaging the wall 64a at periphery 53. Due to the relatively large diameters of the wall 64a and the switch actuator 50, the energy stored in spring 82 is distributed over a relatively large surface area of engagement between the periphery 53 and the wall 64a. 
     The upward movement of the cam follower segment 85 moves the cam follower segment away from contact with the abuttment member 76 as seen by the dotted lines in FIG. 4, the post 75 maintaining the electrical contact between the terminals 74 and 72. Although abuttment member 76 is an integral portion of terminal 74, the abuttment member 76 need not be electrically conductive and could be a suitable insulating material. As seen by the dotted lines in FIG. 4, as the cam 54 continues to rotate in the clockwise direction, the apex of the cam joining the surfaces 55 and 57 eventually engages the apex of the cam follower segment 85 of the contact spring 82 further storing energy in the contact spring 82. As the apex of the cam passes the apex of the cam follower segment 85, the cam surface 57 engages the cam follower segment 85 and the slant of the surface 57 away from contact 72a allows the release of the stored energy in the contact spring 82 snapping the leg 87 into engagement with contact member 70a as seen in FIG. 5 as the ends 83 and 83a pivot about the post or pivot means 75. As seen in FIG. 5, with the leg 87 in contact with contact member 70a, the leg 86 has been disengaged from the contact member 72a and the cam follower segment 85 is again in engagement with abuttment member 76. Up until the moment that the leg 86 is snapped out of engagement with contact 72a, the leg 86 is in contact with contact member 72a and the contact spring is in electrical contact with terminal 74 through post 75 due to the pivotal engagement of the ends 83 and 83a with post 75. It should be noted that electrical connection between the common terminal 74 and the terminals 70 and 72 is made through legs 86 and 87 and ends 83 and 83a of the contact spring whereas the mechanical engagement of the cam surfaces 55 and 57 with the contact spring 82 is through cam follower segment 85. This minimizes the electrical and mechanical degradation of the contact spring at points along the contact spring and further enhances the life of the contact spring 82. Since a portion of the terminal 74 is embedded within the housing section 13 below the surface 66, the contact spring 82 is free to slide along the surface 66 between contacts 70a and 72a. 
     In accord with the present invention, as seen in FIGS. 2 and 3, the cam 54 is disposed near the periphery of switch actuator 50 and therefore there is a relatively long length of rotational travel of the cam 54 with respect to the cam follower segment 85. Since the cam is disposed near the periphery of the switch actuator 50 and the switch actuator is supported by the ledge 64 and wall 64a disposed at the periphery of the housing section 13, the rotational movement of the cam 54 is relatively stable. To shift the spring contact 82 out of engagement with contact 70a and into engagement with contact 72a, the cam 54 is moved in a counterclockwise direction, the cam surface 57 initially engaging cam follower segment 85 and compressing the contact spring 82. The compression of the contact spring 82 by cam 54 disengages the cam follower 85 from abuttment member 76. Continued rotation in the counterclockwise direction of the cam beyond the engagement of the apex of the cam with the apex of the cam follower moves the cam surface 55 into engagement with cam follower portion 85 releasing the energy stored in the contact spring and snapping the leg 86 into contact with contact member 72a. 
     While there has been illustrated and described what is at present considered to be a preferred embodiment of the present invention, it will be appreciated that numerous modifications are likely to occur to those skilled in the art and it is intended in the appended claims to cover all those changes and modifications which fall within the scope and true spirit of the present invention.