US3537056A - Miniature variable resistance control - Google Patents

Description

Oct. 27,1970 7 J. o. VAN BENTHUYSEN ETAL 3 I MINIATURE VARIABLE RESISTANCE CONTROL" I Filed De c. 2e, 1967 I 5/ 12c. p-un n.- E

FIGURE-.6

FIGURE- 3 INVENTORS JOHN D. VAN BENTHUYSE JOHN ZDANYS JR.

United States Patent 3,537,056 MINIATURE VARIABLE RESISTANCE CONTROL John D. Van Benthuysen, Elkhart, Ind., and John Zdanys,

Jr., Edwardsburg, Mich., assignors to CTS Corporation, Elkhart, Ind., a corporation of Indiana Filed Dec. 26, 1967, Ser. No. 693,301 Int. Cl. H01c 5/00 US. Cl. 338162 15 Claims ABSTRACT OF THE DISCLOSURE A centrally disposed collector projecting above the central portion of a base makes electrical contact with a contactor wipingly engaging a resistance element su ported by the base. The contactor is constrained to rotate with a contactor driver, and resilient sealing means compressed against a bearing surface at one end of the control housing biases the contactor and contactor driver toward the collector. Movement of the body of the contactor and the contactor driver toward the base is limited by the collector and normal accumulations of foreign material within the housing do not cause binding of the control. Center terminal pull-out strength and stibility is improved by using a shouldered terminal pin for a collector with the shoulder thereof bearing against the surface of the base. End termination stability is improved by providing shoulders on the end terminal pins anchored in passageways in the base with a bonding material. The base may also be formed with a pair of tapered apertures with the end terminal pins wedged and deformed therein.

The present inveniton relates to variable resistance controls and, more particularly, to miniature variable resistance controls having a movable contactor.

For the past decade printed and modular circuit technologies have been developed and applied to produce miniaturized electronic devices and systems. With increasing acceptance of these devices and systems there has been a concomitant increase in the need for miniature controls, such as variable resistance controls. When attempts have been made, however, to reduce the size of variable resistance controls several problems have been encountered. One problem has been related to the desirability of maintaining an adequate mechanical resistance to changes in the setting of a control. This mechanical resistance to change is referred to as rotational torque in the Barden et al. Pat. No. 3,237,140 and is related to the minimum tangential force necessary to overcome static friction before moving a wiper along a resistance element in order to change the electrical resistance of the control. In some applications of miniaturized controls, when means have been provided to insure adequate rotational torque for preventing inadvertent changes in the setting of the control, such means have deteriorated with use and left deposits of foreign material on movable parts within the control. This foreign material has then caused binding of the movable parts within the control. It is desirable, therefore, to provide means for maintaining sufficient rotational torque that will not deteriorate appreciably with use and that are essentially unaffected by acculations of foreign material within the control.

In variable resistance controls, a movable contactor Wipingly engages a resistance element carried by a supporting base. In some controls, the contactor also engages the surface of a conductive film deposited over a center collector. The use of a conductive film is usually considered desirable and necessary because of size limitations inherent in miniaturized controls even though the use of such film increases the number of interfaces be- 3,537,056 Patented Oct. 27, 1970 tween conductive elements and correspondingly increases the number of potential failure areas within the control. It is desirable, therefore, to provide an electrical control that eliminates redundant conductive interfaces associated with the use of conductive films. It is also desirable to provide a collector-to-contactor interface characterized by good electrical current carrying properties. In miniaturized controls wherein a cover or housing is manufactured from conductive material, extreme care must be exercised to prevent accidental short circuiting between elements such as the contactor or resistance means and the cover. Thus it also would be desirable to provide meanse that reduce the likelihood of occurrence of such short circuiting. More particularly, it would be desirable to provide means that automatically provide proper spacing of the resistive means from the side walls of the control housing and maintain adequate dielectric strength between the resistive means and the control housing.

Miniature variable resistance controls are frequently provided with terminations adapted to be plugged into sockets in circuit boards. In these applications the terminations are mechanically gripped in the terminal board in order to provide good electrical connections. It Will be appreciated that during handling before and after assembly the components may be subjected to vibrations or shock loads that tend to loosen the terminations in the con trol. It will also be appreciated that for many applications where reliability requirements are high, it is necessary that the manufacturer of miniaturized controls thoroughly test a large number of controls in each production run. Since test fixtures with termination receiving sockets are normally used to make such tests, it is extremely important to anchor firmly each termination in the base of the control to prevent loosening of the terminations as they are removed from a test fixture. One approach taken in the past has been to use insertion molding techniques wherein the terminations are anchored in a thermosetting plastic base of an electrical control. The base material, upon hardening, firmly anchors the terminations in place. The insertion molding technique has I not been entirely satisfactory, however, because the presence of the termination on the base has caused handling problems during successive manufacturing operations since the terminations must be protected from being deformed or broken. Accordingly, it would be desirable to provide an arrangement facilitating the mechanized assembly of terminations to the base of a variable resistance control after manufacturing operations on the base have been substantially completed. It also would be desirable to provide terminations characterized by a high pull-out strength, i.e., terminations firmly anchored to the base so as to prevent accidental destruction of the terminations during testing or use. Accordingly, an object of the present invention is to provide a new and improved variable resistance control having the various desirable features set forth above. Another object of the present invention is to provide a variable resistance control particularly adapted for automated assembly techniques wherein the terminals are characterized by high pull-out strengths. A further object of the present invention is to provide a variable resistance control wherein the collector is in positive and direct electrical contact with the contactor. Still another object of the present invention is to provide a variable resistance control wherein means that are not subject to appreciable wear during use are provided for maintaining adequate rotational torque. A still further object of the present invention is to provide a control wherein the rotational torque is not adversely affected by accumulations of foreign material within the housing. Yet another object of the present invention is to provide means for insuring 3 adequate dielectric strength between a resistive film and other conductive portions of the control.

In accordance with one form of the invention, we have provided a variable resistance control comprising an insulating base or supporting member closing one end of a housing and having an arcuate resistance film disposed on the top surface thereof. A contactor wipingly engaging the resistance film is constrained to rotate with a driver within the housing. In a preferred form, the driver has means engageable from the exterior of the housing for altering the angular position of the driver and contactor. A resilient sealing member compressed between the driver and a bearing surface at the end of the housing remote from the base keeps foreign material out of the housing, provides sufiicient frictional resistance to maintain the rotational torque at a desirable level, and biases the driver and contactor toward the base. Collector means, in the form of a shouldered terminal pin supported on the central portion of the base, makes electrical contact with the contactor and limits the movement of the central portion of the contactor and the driver toward the base. The shouldered terminal pin provides a reaction surface for the contactor to insure a satisfactorily large contact force per unit area and provides a supporting arrangement essentially unaffected by deposits of foreign material within the housing.

The resistance film is supported adjacent beveled edges of the base with an air gap between the resistance element and housing of the control. With the beveled arrangement increased surface areas of the base also separate the resistance element from the housing. The ends of the resistance element terminate adjacent apertures in the base and terminations in the form of terminal pins anchored in the apertures are connected electrically to the ends of the arcuate resistance element. In order to improve the termination pull-out strength, the apertures may be tapered with the terminal pins wedged therein; the apertures may be made oversize and a solder slurry or conductive epoxy used to bond the terminal pins to the base; and/or the base may be slightly chamfered around the apertures to accommodate an accumulation of bonding material around the ends of the terminal pins. Shoulders are optionally provided as stabilizing means on the terminal pins and may be used to gauge or otherwise control the depth of terminal pin insertion.

The subject matter which we regard as our invention is set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof may be better understood by referring to the following description taken in connection with'the accompanying greatly enlarged drawings. FIG. 1 is an isometric view of a miniature variable resistance control embodying our invention; FIG. 2 is a sectional view of the variable resistance control of FIG. 1; FIG. 3 is an exploded view of the variable resistance control of FIG. 1; FIG. 4 is an enlarged plan view of a portion of a base, with parts removed and broken away, forming part of the electrical control of FIG. 1; FIG. 5 is a view taken on lines VV in FIG. 4; with parts shown in full; and FIG. 6 is a plan view of another embodiment of a contactor that may be used in the control of FIG. 1.

Referring now more particularly to the drawings, a variable resistance control embodying one form of the invention is generally identified by the reference numeral 10. As best shown in FIGS. 2 and 3, a centrally apertured closure wall 11 at one end of a housing 12 provides a bearing surface 13. A resilient member in the form of an O-ring 14 is compressively urged against the bearing surface 13 by the upper surface 16a of a contactor driver 16. The driver 16 is supported by a collector 17 bearing against the contactor 18. In order to increase the pull-out strength of the collector 17, a shoulder 17a formed thereon bears against the upper surface 19a of the base 19 closing the open end of the housing 12. Tabs 21 extending from the housing 12 and formed around notches 19b in the base 19 hold the housing 12, driver 16, contactor 18, collector 17 and base 19 in assembled relation. To connect the control 10 into an external electrical circuit, terminations 22 and 23 are electrically connected to the ends of an arcuate resistance element 24 suitably secured or bonded to the top surface 19a of the base 19 in a manner well known in the art and termination 17b is formed integrally with the collector 17. The upper surface 19a of the-base is chamfered around the edges thereof in order to provide means for positively spacing the resistance element 24 from the housing 12. With the illustrated arrangement, if the material used to form the resistance element covers the upper surface 19a of the base to the edges thereof, an air gap 20 (see FIG. 2) and beveled surface have sufficient dielectric strength to prevent shortcircuiting between the resistance element and housing.

The contactor 18 is provided with a resilient arm 18a having a wiper 18d for making resilient wiping contact with the arcuate resistance element 24. Extending through the apertured closure wall 11 of the housing 12 is a tool receiving actuating means 16a molded integrally with the driver 16 and rotatable externally of the housing. Although the actuating means 16e has been illustrated as projecting through the end wall 11, it will be appreciated that other suitable tool receiving means such as a socket or groove could be formed in the upper surface 16a of the driver 16 for rotatably adjusting the driver 16 within the housing 12. A boss 16 formed integrally with the driver 16 cooperates with a stop 12a formed in the wall of the housing 12 to limit angular rotation of the driver 16 relative to the housing 12.

Now having particular reference to FIG. 3, rotational interlock means are provided between the contactor 18 and driver 16 to provide for movement of the wiper 18d along the resistance element 21. In the preferred embodiment these means comprise apertures 18b, 18c provided in the contactor 18, and bosses 16b, 16c formed in the bottom surface 160. of the driver 16. Although the rotational interlock means have been illustrated as cooperating apertures and bosses, it will be understood that these means could be in other forms, such as interlocking serrations or grooves and notches on the surface of the driver and around the periphery of the contactor. In order to diminish electrical and mechanical noise during operation of the control a preferred form of the wiper 18d includes a carbon button 26 having the contacting surface 26a thereof slightly rounded to promote proper alignment with the resistance element upon initial assembly of the control. The buttom surface 16d of the driver 16 is relieved as at 16e to provide a clearance for either the shank of the carbon button 26 or the ends of wiping paddles when paddles are used in lieu of the carbon button as will hereinafter more fully be explained in connection with FIG. 6.

After the arcuate resistance film has been suitably secured or bonded to the surface 19a in a manner well known in the art, a pair of terminations such as terminal pins 22 and 23 are secured to the supporting member. As best shown in FIGS. 35 a noncircular tapered aperture 27 is formed in the supporting member 19 for each of the terminal pins 22 and 23. The round terminal pins 22, 23 are driven into the tapered apertures 27 from the bottom of the base 19 and when shoulders 22a, 23a are provided they abut the bottom surface of the base in the bearing areas 27a. In addition to providing a means for preventing over insertion of the pins 22, 23, the increased bearing surface of the shoulders aids in stabilizing the terminal pins in the base during tests. It should be understood, however, that the shoulders 22a, 23a may be dispensed with and automatic pin insertion equipment may be provided with suitable means for gauging the insertion depth of the terminal pins when the Stabilizing effect of the shoulders is considered neither necessary nor desirable.

It has been observed that as the round terminal pins 22, 23 are driven into the apertures 27, portions of the pins are deformed by flattening and at least partially conform to the internal configuration of the apertures. We have found that this results is achieved when the terminal pins are formed of a material softer than the base 19. With this arrangement the terminal pins are securely held in the base and are characterized by pull-out strengths in the range of twelve pounds when the terminal pins are made from 0.022 of an inch diameter, tin coated half hard zirconium copper wire; when the base is made from 0.081 of an inch thick high alumina; and when the end terminal apertures are square, have a taper of about two degrees, and a 0.017 of an inch square, dimension at the top surface of the base. After the terminations are secured to the base, a solder slurry 28 or non-shown conductive epoxy or other suitably conductive material is applied to the top surface of the base 19 to electrically connect each of the terminations to the arcuate resistance film 24 through the conductive films 24a, 24b. In many applications it is important to prevent the end terminations from projecting above the upper surface of the base. Accordingly, as best illustrated in FIGS. 4 and 5, the upper ends of terminal pins 22, 23 terminate just at or slightly below the upper surface of the base 19, and in order to improve the pull-out strength of the terminations, the epoxy or solder 28 may fill the space between the walls of the aperture and terminations. Of course, when permitted, the end terminal pins may extend above the top surface of the base and the solder 28 may then be used to form a fillet around the upper end of each end terminal pin or, alternatively, the upper surface of the base may be relieved around the apertures to permit the formation of a solder fillet around the upper end of the end terminal pins 22, 23. When provision is made for epoxy or solder fillets around the terminal pins adequate termination pull-out strength may be attained without making use of noncircular or tapered apertures and it will be expressly understood that fillet formation may be accomplished by making the apertures slightly oversized and flowing the solder or conductive epoxy into the apertures around the terminal pins.

As best shown in FIGS. 2 and 5, the conductive films 24a, 24b are offset laterally from the path of the resistance element 24. With this arrangement it is possible, when desired, to actually insert the terminal pins 22, 23 so that end portions thereof project through the top surface 19a of base 19 without being in an interference path with the wiper of the contactor. It will be appreciated that when the terminal pins do project above the upper surface of the base, the ends of the pins may be deformed or solder fillet formation may be accomplished in any of the modes hereinabove described. Although any suitable material may be used for the conductive films 24a, 24b when solder is to be utilized as a connecting means, it is preferable that the film be a solderable material such as platinum-gold.

In the exemplification, the collector means comprises a collector pin 17 relatively loosely carried by the base 19. Since the shoulder 17a of the collector pin 17 bears against the upper surface 19a of the base 19, the collector termination 17b is also characterized by a satisfactory pull-out strength. As best shown in FIG. 2, the collector pin 17 pinches the contactor 18 between the driver 16 and the end of the collector pin limiting the movement of the contactor 18 toward the resistance element and also maintaining the resilient O-ring 14 in a slightly compressed state. Since the area of contact between the contactor 18 and collector pin 17 is relatively small, the force per unit area of the contact surface between the collector and contactor is relatively large and this in turn promotes a good electrical connection therebetween. Since the collector is centrally located within the control 10, the driver 16 is essentially balanced on the collector and spaced from the base 19. Accordingly, the base cannot abrade the driver while it is being rotated and produce small particles of foreign matter inside the control. In addition, since the driver is spaced from the base, any foreign particles inside the control will not wedge between the driver and base thereby to adversely affect the rotational torque of the control.

It will be appreciated that the compressible O-ring 14 frictionally couples the driver and housing to provide a desirable rotational torque and cooperates with the collector in interlocking the contactor 18 with the driver 16 to thus dispense with the necessity of bonding the driver and contactor together. In addition, the contactor 18 need be formed with only one springsection since the O-ring provides sufficient biasing force to maintain satisfactory contactor-to-collector contact. In FIG. 6 we have illustrated another embodiment of a contactor that may be used in the practice of our invention. The contactor 29 includes interlocking apertures 29b, 29c and is generally similar to the contactor 18 shown in FIG. 3. The resilient arm 29a, however, has a wiper section 29d including a pair of paddles or fingers 292 for wipingly engaging the resistance element. When a control was actually constructed embodying our invention, the base was formed of high alumina having a thickness after firing of about 0.090 of an inch and about 0.250 of an inch square. The apertures measured about 0.017 of an inch square on the top surface of the base and about 0.021 of an inch square at the bottom surface of the base. The apertures had a taper of about 2 for a depth of about 0.061 of an inch from the upper surface of the base and a taper of about /2" from the bottom surface of the base for a depth of about 0.029 of an inch. The bottom surface was relieved around the apertures to provide bearing surfaces 27a for the shoulders 22a and 23a. The O-ring was formed of 0.030 of an inch diameter silicone rubber with an inner diameter of about 0.125 of an inch, the end terminations and collector were formed from tin coated half hard 0.018 of an inch diameter zirconium copper wire, and the collector extended about 0.044 of an inch above the surface of the base.

In view of the foregoing, it will be appreciated that We have provided an improved miniature variable resistance control wherein the terminations thereof may be readily secured to the base in an automated manner while maintaining satisfactory pull-out characteristics. It will also be appreciated that we have provided a miniature control wherein the reactive force of supporting the driver and contactor is utilized to insure a good electrical connection between the contactor and collector. In addition, automated handling of the housing and control is facilitated by the non-circular cross sectional configuration of the housing. Although the contactor in the preferred embodiment is essentially planar in the central portion thereof, it will be appreciated that the contactor could have a projection, resilient or otherwise, extending toward and in engagement with a foreshortened collector.

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 changes and 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 true spirit and scope of the present invention.

1. A variable resistance control comprising a hollow housing having a bearing surface at one end and an opening at the other end, a driver disposed in the housing, said driver disposed with the upper surface thereof in confronting relationship to the bearing surface of the housing, a supporting member closing the opening at said other end of the housing, a resistance element disposed on the upper surface of the supporting member, a contactor disposed between the bottom surface of the driver and the supporting member, the contactor being drivingly engaged by the driver and in resilient Wiping contact with the resistance element, means for connecting the control to an external electrical circuit including a rigid collector supported by the supporting member and projecting toward the contactor and driver, said collector pinching the contactor between the collector and the bottom surface of the driver, and resilient means compressed between the bearing surface of the housing and the driver thereby urging the driver toward the supporting member, the collector limiting the movement of the driver and a portion of the contactor toward the supporting member.

2. A variable resistance control comprising a generally square housing having a centrally apertured closure wall at one end and an opening at the other end, a supporting member closing the opening at said other end of the housing, a resistance element disposed on the supporting member, a collector supported by the supporting member, means for securing the supporting member to the housing, a substantially round molded driver, means for cooperating with a tool formed on one side of the driver, a contactor drivingly interlocked with the other side of the driver and having a wiper contacting the resistance element, resilient means surrounding the means for cooperating with a tool, said resilent means being compressed between the apertured closure wall and the driver thereby biasing the driver toward the collector whereby a portion of the contactor interlocked with said other side of the driver bears against the collector, said contactor having a pair of apertures formed therein and said driver having a pair of bosses formed on said other side cooperating with the apertures in the contactor, said driver having a recessed area formed therein to provide a clearance area for the wiper, the pair of bosses in the driver interfitting with the apertures in the contactor to provide a driving interlock between the contactor and the driver, termination means projecting from the bottom of the supporting member, the supporting member having a pair of spaced apertures, said termination means held in the spaced apertures, and electrically conductive means bonded to said termination means and in electrical contact with the resistance element.

3. The control of claim 2 wherein the driver includes a boss formed thereon and the housing further comprises an inwardly projecting stop, the boss and stop cooperating to limit rotational movement of the driver relative to the housing, and the collector has a shouldered portion bearing against the supporting member.

4. In a variable resistance control, the combination of a housing open at one end, said housing having an apertured bearing surface provided at the other end, a base closing said one end of the housing, a resistance film having two end portions supported by the base, a pair of terminations in electrical contact with the resistance film and supported by the base, contactor means for making sliding contact with the resistance film, driver means drivingly engaging the contactor means for moving the contactor means relative to the resistance film, the driver means having means in centrally spaced relationship to the apertured bearing surface for cooperating with an adjusting means, a rigid collector pin positioned between the end portions of the resistance film projecting toward the contactor means and providing a pivot area for the contactor means, said collector pin pinching said contactor means against said driver means, and means resiliently urging the contactor means into electrical engagement with the pivot area of the collector pin, said base being provided with a pair of apertures extending through the base adjacent the end portions of the resistance film, said pair of terminations being anchored in the apertures.

5. The variable resistance unit of claim 4 wherein the contactor means comprises a uniplanar body portion centrally disposed in the housing and a single spring arm, and the means resiliently urging the contactor means comprises an O-ring compressed between the apertured bearing surface and driver means.

6. The variable resistance unit of claim 4 wherein conductive means bond the pair of terminations to the base and the apertures decrease in cross-sectional area from the bottom surface of the base to the top surface of the base.

'7. A variable resistance control comprising a hollow housing having a centrally apertured closure wall at one end thereof and an opening at the other end thereof, a driver disposed in the housing with a downwardly facing surface, a base closing the opening at said other end of the housing, a resistance element disposed on the base and having at least one end electrically connected with a termination whereby the control can be connected with an external electrical circuit, a contactor drivingly engaged by the driver, the contactor having a first portion disposed in the central portion of the housing and a second portion disposed for wipingly engaging the resistance element, and a rigid collector pin supported by a central portion of the base, the collector pin having one end projecting toward the first portion of the contactor and pinching the first portion of the contactor between the end of the collector pin and the downwardly facing surface of the driver thereby limiting movement of the first portion of the contactor toward the base.

8. A variable resistance control comprising a housing open at one end, a base closing said one end of the housing, means securing the base to the housing, a resistance element having two end portions supported by the upper surface of the base, a pair of terminations for electrically connecting the end portions of the resistance element to an external electrical circuit, a contactor having a first portion centrally positioned within the housing and a wiper portion resiliently engaging the resistance element, a driver for moving the wiper portion of the contactor along the resistance element, a collector comprising a rigid shouldered pin in electrical contact with and pinching the first portion of the contactor between the end of the pin and the driver, said shouldered pin limiting movement of the first portion of the contactor and the driver toward the base, the shoulder of the pin bearing against the upper surface of the base, and chamfered edges formed around the top surface of the base providing an air gap between the resistance element and the housing whereby the dielectric characteristic of the path between the resistance element and the housing is improved.

9. A variable resistance control comprising a hollow housing having a centrally apertured closure wall at one end and an opening at the other end, a driver disposed in the housing and comprising a tool receiving means centrally disposed relative to the centrally apertured closure wall, a base closing the opening at said other end of the housing and having a centrally located aperture therethrough, a rigid collector supported in the centrally lo cated aperture and projecting from the base toward the driver, at least two terminations supported by the base whereby the control can be connected with an external electrical circuit, a resistance element disposed on the upper surface of the base and having at least one of the ends thereof electrically connected with one of the terminations, a contactor overlying the resistance element and drivingly engaged with the driver, the contactor having a first portion thereof positioned centrally within the housing and supported by the collector whereby movement of the first portion of the contactor away from the driver is limited by the collector pinching the contactor between the collector and the driver, the contactor having a second portion disposed for wipingly engaging the resistance element, and means resiliently urging the second portion of the contactor into resilient engagement with the resistance element.

10. A variable resistance control comprising a hollow housing, a base secured to the housing at a first end thereof, a resistance element supported within the housing adjacent the base, a contactor resiliently engaging the resistance element, a driver retained in the housing between the contactor and a second end of the housing, and collector means comprising a rigid pin supported by the base, a first end of the pin extending through the base outwardly from the control for connection to an external electrical circuit, and a second end of the pin cooperating with the driver and pinching a portion of the contactor between the second end of the pin and the driver thereby making an electrical connection between the contactor and pin, said second end of the pin rigidly supporting said driver and contactor against relative movement toward the base.

11. A variable resistance control comprising a hollow housing, a base secured to the housing at a first end thereof, a resistance element supported within the housing adjacent the base, a contactor resiliently engaging the resistance element, a driver retained in the housing between the contactor and a second end of the housing, resilient means biasing the driver toward the first end of the housing, and collector means supported by and extending through the base cooperating with the resilient means and holding the contactor in interlocked relationship with the driver, said collector means having a portion extending out of the control for connection to an external electrical circuit, said collector means rigidly supporting said driver and said contactor against movement toward the base, said base having at least three chamfered edges on the top surface providing an air gap between the resistance element and the housing.

12. A variable resistance control comprising a hollow housing, a base secured to one end of the housing and having at least two apertures passing therethrough, said base having a first surface and a second surface with said apertures extending from the first surface to the second surface, each of said apertures having noncircular cross sectional configurations, a resistance element supported within the housing, a contactor having a first portion for wipingly engaging the resistance element, a driver constrained to move with the contactor for moving said first portion of the contactor relative to the resistance element, collector means disposed in the housing and extending therefrom for connection to an electrical circuit externally of the control, a pair of terminations having end portions, the terminations each comprising a pin having a deformed portion anchored in one of said apertures, and conductive means secured to the base and the end portions, said conductive means electrically connecting the terminations and the resistance element.

13. The control of claim 12 wherein said at least two apertures are tapered and have substantially square cross sectional configurations, and the terminations each comprise generally round pins.

14. The control of claim 12 wherein the terminations comprise pins having a shoulder thereon, the shoulder of each pin bearing against the base to prevent overinsertion of the pins in the apertures.

15. The control of claim 12 wherein said at least two apertures have substantially square cross sectional configurations, and the terminations comprise generally round pins.

References Cited UNITED STATES PATENTS 3,124,778 3/1964 Youngbeck 338- 3,266,004 8/1966 Fox et a1 338-174 3,406,367 10/1968 Maguire 338-184 3,416,119 12/1968 Van Benthuysen et al.

338-174 3,237,140 2/1966 Barden et al. 338-164 3,387,247 6/1968 Mishler 338-162 FOREIGN PATENTS 866,428 11/1957 Great Britain.

LARAMIE E. ASKIN, Primary Examiner A. T. GRIMLEY, Assistant Examiner US. Cl. X.R.

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