US3208024A - Potentiometer construction - Google Patents

Description

Sept. 2l, 1965 H. B. ENos ETAL 3,208,024

POTENTIOMETER CONSTRUCTION K Filed Dec. 5, 1962 020262/ Q www u um N /Z f2 /5 Z4 25 Z6 INVENTOR 420m LFA/0S,

Olf/ M ATTORNEY United States Patent 3,208,024 POTENTIOMETER CONSTRUCTION Harold B. Enos, Whittier, and Byron L. Hartley, Monrovia, Calif., assignors to Edcliff Instruments, Incorporated, Monrovia, Calif., a corporation of California Filed Dec. 5, 1962, Ser. No. 242,442 19 Claims. (Cl. 338-162) The present invention relates to construction of potentiometers.

Features of the subject invention provide a novel and simplified construction for the entire mechanical portion of subminiature, rotary, trimming potentiometers, permitting the application of new and improved manufacturing methods to such constructions with the result being improved usefulness, greater functional reliability and reduced manufacturing costs. Other features of the present invention involve a construction wherein there is provided a high ratio driving means, improved contacting wiper means spring-loaded in a novel manner, with the driving means comprising also a slip clutch acting as such at the limits of travel of the wiper means.

It is therefore a general object of the present invention to provide an improved potentiometer construction embodying the above-indicated features.

A specific object of the present invention is to provide a construction which may be made small and inexpensively.

Another specific object of the present invention is to provide an improved potentiometer construction permitting the use of simple manufacturing methods in fabrication and assembly of the various parts.

Another specific object of the present invention is to provide a potentiometer construction incorporating novel high ratio driving means.

`Another specific object of the present invention is to provide a new potentiometer construction involving novel wiper means which are spring-loaded.

Another specific object of the present invention is to provide an improved potentiometer construction using a novel slip clutch construction.

The features of the present invention which are believed to be novel are set forth with particularly in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is an elevational view showing the top of a potentiometer embodying features of the present invention.

FIGURE 2 is a view in side elevation of the same.

FIGURE 3 is a sectional view taken generally along the line 3 3 of FIGURE l.

FIGURES 4, 5 and 6 are generally sectional views taken along corresponding lines 4-4, 5 5 and 6-6 in FIGURE 3.

FIGURE 7 shows a modified construction.

FIGURE 8 shows another modified construction.

FIGURE 9 is a sectional view taken generally along the line 9-9 of FIGURE 8; and

FIGURE 10 illustrates still another modified construction.

Referring to FIGURES 1-6, the housing for the potentiometer comprises two parts 10 and 11, the part 10 for convenience being referred to as the top part and the part 11 for convenience being referred to as the bottom part. The top part 10 has an internal peripheral shouldered portion 10A against which the upper edge of the lower part 11 abuts, and after assembly of the parts within the housing 10, 11, the same are sealed together by a sealant 12 which is disposed within a peripheral grooved Patented Sept. 21, 1965 ice portion 13 defined by an inner wall of part 10 and an undercut part of part 11.

The bottom part or base 11 is formed to provide a peripheral shelf portion 15 on which the circular resistance element 16 rests, the resistance element 16 comprising a plurality of turns of resistance wire wound on a circular insulating form 17 With the ends of the resistance element 16 being connected as, for example, by soldering to the two flexible insulated conductors 20 and 21 which extend through spaced sealed openings in the base member 11, these openings being sealed by the same sealant 12.

The base portion 11 is formed also with an internally shouldered hub portion 24 for receiving a circular metallic pin 25 having a conical end 25A, the base of the pin 25 having soldered thereto an insulated flexible lead 26 which, like the leads 20 and 21, extends through a sealed opening in the base member 11.

Thus hub portion 24, as shown in FIGURE 5, has a small protuberance 24A which acts as a stop member for a rotatable element 30 in the form of a spring disc having a portion 30A thereof stamped therefrom to provide the stamped finger 30A for engagement with the stop member 24A.

This element 30 has its central portion apertured and deformed to provide a bearing portion 30B seatable on the tapered pin end 25A.

This element 30, las shown in FIGURE 3, has a second finger stamped therefrom, such finger 30C having its extremity bent to provide an area thereon contactable with the resistance element 16. This finger 30C may thus be considered to be the so-called wiper arm of the potentiometer.

This spring element 30, in the form of a disc, has its peripheral portion engageable with an internal peripheral protuberance 10B of the top member 10, such peripheral portion 10B extending, however, less than 360 degrees to allow placement of a driving-worm-type screw 35 which has its threaded portion engageable with the spaced apertured portions 30D in spring member 30 to provide a driving connection therebetween.

The worm screw 35 is rotatably mounted in the top part 10, there being provided a small bore 10E therein receiving the small shaft portion 35A :of worm screw 35 and an aligned large bore 10F receiving the larger shaft portion 35B. This worm screw element 35 is provided with an internal lug 35C which is engageable with a bifurcated end of a spindle 40 having a shouldered portion 40A, a grooved portion 40B and a kerf 40C for turning of the worm screw 35 by a screwdriver. This worm screw 35 is sealed by the O-ring 42 which is disposed between the shaft end 35B and the shouldered portion 40A and which is maintained in a stressed condition by the assembly pin 44 extending through the housing part 10 and the annular groove 40B.

The spring disc element 30, in this assembly, is thus maintained in a stressed condition to at all times maintain good electrical contact between itself and the tapered pin end 25A and also to maintain the resilient finger or wiper arm 30C in good electrical contact with the resistance element 16 and also to assure a resilient mechanical connection between the aperture disc portions 30D and thread on worm screw 35, the peripheral spacing of the apertured portions 30D corresponding to the pitch 0f the worm screw thread.

It will be seen that upon rotation of the spindle 40, the wiper arm of finger 30C may be rotated an angular distance slightly less than 360 degrees corresponding to the angular extent of resistance element 16 as a result 'of the driving connection between the worm screw 35 and the apertured portions 30D. This driving connection, however, is interrupted automatically when the tab 30A (FIGURE 5) of the element 30 engages the stop member 24A, this being so since the disc 30A is suiiiciently resilient to be pressed downwardly to disengage the apertured portions 30D from the worm screw thread upon further rotation of theworm screw 35. Thereafter, upon reverse rotation of the worm screw 35, there is automatic engagement of the apertured portions 30D and thread on the worm screw 35 to provide a driving connection.

In the modification shown in FIGURE 7, the top and bottom housing parts and 11 are constructed as previously described and in this instance the pin 125, corresponding to the pin 25 of FIGURE 3, has a rounded end on which is resiliently seated a different form of driven disc 130 corresponding to the disc 30 of FIGURE 3.

The disc 130 is made of spring stock and has a resilient finger or wiper arm 130C stamped therefrom, the finger 130C being resilient and contacting the resistance element 16. Instead of providing apertured portions such as the apertured portions 30D in FIGURE 5, in FIGURE 7 equally spaced peripheral protuberances for engagement with the worm screw 35 are provided, such protuberances 130D being formed, for example, by deforrning the disc member 130. Also, such disc member 130 has struck therefrom, by means of a stamping operation, three equally spaced circumferentially extending spring lingers 130E each having its ends curled slightly to provide contact area with an inner face of housing part 10 to thereby assure good electrical contact at all times between the pin 125 and resistance element 16. Also, as described in FIGURE 4, the disc 130 is sufficiently resilient to allow the protuberances 130D to be disengaged from the worm screw 35 at extreme positions of rotation of the wiper arm 130C.

In the modification shown in FIGURE 8, the base housing part 11 is constructed as in the previous figures, and the upper housing part 110, corresponding to the housing part 10 of the previous figures, is now provided with an inner boss 110A which serves as a gearing member for the modied driven disc member 230 which in this instance is of resilient insulating material having a blind bore 230F for receiving the boss 110A. The disc 230 is formed with equally spaced and circumferentially extending protuberances 230D engageable with the worm screw 35, the protuberances 230D being spaced commensurately with the pitch of the worm screw thread. In this case the resilient wiper arm 230C of metal is a separate element having an arcuate portion, as shown in FIG- URE 8, inserted within a circular :opening in the disc member 230 which receives the reduced end portion of pin 225 such that good electrical contact is established between the wiper arm 230C and the pin 225 when such pin 225 is inserted in such opening. The protuberance 230A on the disc member 230 serves as a stop member, performing the same function as the tab 30A in FIG- URE 5.

Here again, as in the previous ligures, the disc 230 is sufficiently resilient to automatically disestablish a driving connection between the protuberances 230D and the worm screw 35 when the wiper arm 230C is moved to either one of its two extreme positions of rotation.

FIGURE 10 is a modification of FIGURE 9 and in this case the wiper arm 330C, inserted within the disc member 330, extends completely around the pin 325 which in this instance may have its end either rounded or tapered as in the previous figures. The protuberance 330A serves as a stop member.

While the resistance element 16 is shown as comprising a plurality of turns of resistance wire, it will be appreciated by those skilled in the art that this resistance element may take other forms; for example, resistance element 16 may be in the form of a molded composition resistor of similar shape or, for example, resistance element 16 may be in the form of a resistive film coated upon a nonconductive base formed in a similar shape.

In each of the arrangements shown in the drawings, the worm screw 35 may be made of insulating material used iwith a spindle of insulating material; the worm screw 35 may be made of insulating material used with a spindle of conducting material; or the worm screw 35 may be made of conducting material used with a spindle of insulating material.

In the arrangement shown in FIGURE 8, using a disc 230 of insulating material, the worn screw 35 and spindle may be of conducting material separately or as one piece, and the top portion may be of conducting material.

In all arrangements shown, the worn screw and spindle, corresponding to worn screw 35 and spindle 40, may be in one piece of insulating material.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader `aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

We claim:

1. In a potentiometer construction, a generally resilient disc-shaped member having circumferentially extending and spaced means thereon for driving the same, a housing, a generally circular resistance element mounted ooaxially with said element within said housing, electrical contacting and conducting means carried on said member and contacting said element, means rotatably supporting said member in said housing, the last mentioned means including a conducting pin in said housing electrically contacting said electrical contacting and conductive means, means producing relative rotation between said element and member, said means comprising a worm screw rotatably mounted in said housing and having its thread engageable with said spaced means for driving said member, said worm screw and said pin being on opposite sides of said member with said resilient member being stressed between said worm screw and said pin to establish a driving connection between said member and said worm screw.

2. A construction as set forth in claim 1 in which said sbpaced means comprises apertured portions in said mem- 1 er.

3. A `construction as set forth in claim 1 in which said spaced means comprises protuberances on said member.

4. A construction as set forth in claim 1 including means for limiting the movement of said member, said member being suiiiciently resilient to move said spaced means out of driving engagement with said worm screw to disestablish the driving connection therebetween when the movement of said member is limited by said limiting means.

5. A construction as set forth in claim 4 in which said contacting and conducting means is a resilient linger integrally formed with said member.

6. A construction as `set forth in claim ll in which said member has integrally formed resilient iingers engaging said housing to press said member into engagement with said pin.

7. A construction as set forth in claim l in which said housing has a circumferentially extending protuberence engaging said member to press it into engagement with said pin.

8. A construction as set forth in claim 7 in which said member is of metal and engages said pin.

9. A construction las set forth in claim 7 in which said member is of insulating material, said contacting and conducting means being of metal and mounted on said member and contacting said pin.

10. A construction as set forth in claim 9 in which said contacting and conducting means is inserted in said in` sulating material and partially embraces said pin.

11. A construction as set forth in claim 9 in whichsaid contacting and conducting means is inserted in said insulating material and surrounds `said pin.

12. In a potentiometer construction, a two-piece, housing having a base part and a top part, salti base partgliaM- ing an inner annular shelf portion, a circular resistance element resting on said shelf portion, said base part having a hub portion coaxial with said shelf portion, a metal pin in and extending out of said hub portion, electrical leads connected respectively to said resistance element and said pin .and extending through sealed openings in said base part, a generally disc-shaped resilient member rotatably mounted on said pin and having circumferentially extending and spaced means thereon for driving the same, a worm screw rotatably mounted in said top part and having its thread engageable with said spaced means, said worm screw and said pin being on opposite sides of said member, said top part having a circumferentially extending protuberance engaging said member to urge the same toward said pin, said member being resilient and resiliently pressing said spaced means against said worm screw to establish a driving connection between the same, and electrical contact means contacting said pin and ycarried by said member for engaging said resistance element.

13. A construction as set forth in claim 12 in which said worm screw has shaft portions on opposite ends thereof joumalled for rotation in said top part, a spindle having a screwdriver kerf and a grooved portion and means thereon for driving said worm screw, an O-ring squeezed between said worm screw and said spindle, and a pin in said top part and extending through said grooved portion maintaining said O-ring squeezed between said worm screw and said spindle.

14. A construction as set forth in claim 12 in which said member has integrally formed resilient fingers pressed against said top part.

1S. A construction as set forth in claim 12 in which said top part has an internal boss extending into the circular apertured portion of said member.

16. A construction as set forth in claim 12 in which said member is of a metal and said contact means comprises an integrally formed finger thereof.

17. A construction .as set forth in claim 12 in which said member is of insulating material and said contact means is inserted therein.

18. A construction as set forth in claim 12 including means for limiting movement of said member in one position thereof, and said member being suiiciently resilient to permit disestab'lishment of the driving connection between said worm screw and member at said position.

19. In a potentiometer construction, a resistance element, a one piece driven rotatable means contacting said element, worm screw means for normally driving said driven means, said one piece driven means being inherently resilient and being resiliently pressed by its inherent resiliency against said worm screw means to establish a driving connection between said worm screw means and rotatable means, said resilient means being suiciently resilient to disestablish said driving connection upon the transmission of more than a predetermined force between said Worm screw means and rotatable means, a two-part housing having two parts, said resistance element, one-piece rotatable means, worm screw means all being within said two-part housing, an electrical contacting and conducting pin having one of its ends seated in one of said housing parts and rotatably supporting said one-piece rotatable means at the other one of its ends, the other of -said housing parts contacting said one-piece rotatable means to stress and press said rotatable means in electrical contact with said pin to establish an electrical connection between said pin and said resistance element through said one-piece rotatable means, said one-piece rotatable means being of electrically conducting material, and said worm screw means being rotatably mounted in said other housing part.

References Cited by the Examiner UNITED STATES PATENTS 2,880,293 3/59 Blanco 338-175 X 2,887,554 5/59 Smith et al 338-164 X 2,952,825 9/60 Bourns 338-175 X 3,054,077 9/62 Mellor 338--175 3,059,200 10/62 Bamford 338-180 3,099,810 7/ 63 Habereder 338-162 3,105,217 9/63 Ferrell et al 338-174 0 RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

Claims (1)

1. IN A POTENTIOMETER CONSTRUCTION, A GENERALLY RESILIENT DISC-SHAPED MEMBER HAVING CIRCUMFERENTIALLY EXTENDING AND SPACED MEANS THEREON FOR DRIVING THE SAME, A HOUSING, A GENERALLY CIRCULAR RESISTANCE ELEMENT MOUNTED COAXIALLY WITH SAID ELEMENT WITHIN SAID HOUSING, ELECTRICAL CONTACTING AND CONDUCTING MEANS CARRIED ON SAID MEMBER AND CONTACTING SAID ELEMENT, MEANS ROTATABLY SUPPORTING SAID MEMBER IN SAID HOUSING, THE LAST MENTIONED MEANS INCLUDING A CONDUCTING PIN IN SAID HOUSING ELECTRICALLY CONTACTING SAID ELECTRICAL CONTACTING AND CONDUCTIVE MEANS, MEANS PRODUCING RELATIVE ROTATION BETWEEN SAID ELEMENT AND MEMBER, SAID MEANS COMPRISING A WORN SCREW ROTATABLY MOUNTED IN SAID HOUSING AND HAVING ITS THREAD ENGAGEABLE WITH SAID SPACED MEANS FOR DRIVING SAID MEMBER, SAID WORN SCREW AND SAID PIN BEING ON OPPOSITE SIDES OF SAID MEMBER WITH SAID RESILIENT MEMBER BEING STRESSED BETWEEN SAID WORN SCREW AND SAID PIN TO ESTABLISH A DRIVING CONNECTION BETWEEN SAID MEMBER AND SAID WORN SCREW.

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