US3028571A

US3028571A - Multiturn potentiometer

Info

Publication number: US3028571A
Application number: US59080A
Authority: US
Inventors: George J Mucher
Original assignee: Clarostat Manufacturing Co Inc
Current assignee: Clarostat Manufacturing Co Inc
Priority date: 1960-09-28
Filing date: 1960-09-28
Publication date: 1962-04-03
Anticipated expiration: 1979-04-03
Also published as: GB925496A

Description

April 3, 1962 G. J. MUCHER 3,028,571

MULTITURN POTENTIOMETER Filed Sept. 28, 1960 2 Sheets-Sheet l INVENTOR.

GEORGE J. MU CHER April 1952 G. J. MUCHER 3,028,571

MULTITURN POTENTIOMETER Filed Sept. 28, 1960 2 Sheets-Sheet 2 FIG. 3

l7' l8' l9 F I G. 4

INVENTOR.

GEORGE J. MUCHER United States Patent'Q 3,028,571 MULTITURN POTENTIOMETER George J. Mucher, Rochester, N.H., assignor to Clarostat lgflfglk Co., Inc, Dover, N.H., a corporation of New Filed Sept. 28, 1960, Ser. No. 59,080 Claims. or. 338-143 which moves along the longitudinal axis of the helix to traverse the various turns thereof in order to alter the value of the resistance. -The most common method ofmoving the contact arm 'is through use of a rotatable shaft mechanically connected with the contact arm so that rotation of the shaft will effect longitudinal movement of the contact arm. Such an assembly is utilized in equipment wherein high accuracies are sought and the movement of the contact arm must be accomplished in such a manner that little or no electrical error results from the mechanical construction of the device. The rotation of the shaft in assemblies of this type is usually accomplished by a servo motor and because of the accuracies involved it is theoretically desirable to have the extreme of rotation of the servo motor coincident with the extreme movement of the contact arm'in both directions. This, of course, is impossible in a practical physical embodiment and one of the main sources of difficulty in the utilization of multiturn potentiometers results from the requirement that if the movement of the shaft and the movement of the contact arm are not precisely synchronized, the potentiometer is in serious danger of being damaged. To this end various methods have been used and constructions made to effect a stopping of they contact arm at its extreme position without damaging the assembly even if the shaft is further rotated.

The invention herein disclosed has as its principal object the furnishing of a new multiturn potentiometer of such construction that it can resist a high degree of turning torque applied to its shaft without damaging the structure even though the contact arm has reached an extreme position.

Another object of this invention is to provide a multiturn potentiometer of rugged construction which suffers vary little backlash and which will not alter its electrical characteristics because of dirt forming in the track in which the contact carrier moves.

A further object of this invention is to provide a multiturn potentiometer whose movable parts are light in mass, one thatrequires low torque to move the contact arm, and one that exhibits superior vibration characteristics.

The invention disclosed herein is described in. terms of a potentiometer by way of example only and it should be understood that the inventive concept set forth herein can be applied by one reasonably skilled in the art to other variable parameter components whose value is altered by moving a contact arm by rotation of a shaft.

A multiturn potentiometer embodying the invention and the manner of using the same is described herein with references to the drawings in which:

FIG. 1 is an exploded top perspective view of a multiturn potentiometer constructed in accordance with the teachings of this invention with portions thereof broken away to disclose detailed views of portions thereof;

FIG. 2 is a segmentary view of a portion of the casing .and winding of the potentiometer shown in FIG. 1 as "ice viewed in the direction of the arrow designated with the numeral 2;

FIG. 3 is a partially sectional view taken along the line 3-3 in the direction of the arrows as indicated in PEG. 1. showing in cross-section the contact driver, contact carrier, and contact arm utilized in the potentiometer; and

FIG. 4- is a circuit diagram of one possible winding circuit arrangement. I

In FIG. 1 a molded cylindrical casing 10 is shown having a resistance Wire in the form of a helix 11 embedded in the internal surface thereof. The axis of the helix and the axis of the casing are identical. As seen also in FIG. 2, casing 10 is formed with a helical groove 12 on its internal surface so that each turn of resistance wire 11 is separated from adjacent turns by a portion of helical terial can be used for this purpose. In its preferred form, the external surface of casing 10 is formed with longitudinal slots 13 and through openings 14 in order to aid in assembling certain portions of the device and in order to aid in placing external casing 15 over casing 10 when the assembly has been completed.

External casing 15 is shown in FIG. 1 and in the final assembly the casing 10 lies within casing 15 and concentric therewith. Openings 14 are used to aid in the assembly and to allow leads to be brought from within casing .10 to

posts

16, 17, 18 and 19 of terminal block 20 which is rigidly fastened to the external surface of casing 15. Openings21 in

casing

10 and 22 in casing 15 are utilized to maintain the two casings rigidly together in the final assembly steps. I

One end of casing 15 is closed and a bearing member 23 is embedded in the internal surface thereof and designed to receive corresponding bearing member 23 which is fashioned at one end of shaft 24 which is the axis of the driver member indicated generally by the numeral 25 in the figures. As shown in the figures, the combination of bearing

members

23 and 23 form a sleeve bearing supporting one end of shaft 24 which is preferably steel but which could be formed from any suitable material. Although a sleeve bearing assembly is illustrated in the figures, other types of bearings can be utilized.

Circular cover 26 is formed with a portion 27 of external diameter so that it can be received within casing or housing 15 and maintained therein by utilization of openings 21, 22and 23. The cover 26 is formed also from any suitablematerial which is a non-conducting material. 'In the preferred form, control housing 15 and cover 26 are molded from diallyl phthalate. The cover or liner 10 as set forth above is also molded from a non-conducting material. In its preferred form the material of which liner 10 is molded is epoxy resin, however, any suitable material can be used for this purpose.

Body 29 which is-originally attached to shaft 24 contains longitudinal slot 33 extending throughout its length. Longitudinal slot 33 is formed to receive metallic U- channel 3 which in turn forms the track for sliding stop 35. Channel 34 is U-shaped in cross-section forming a substantially rectangular track in which sliding stop 35 is maintained against rotational movement but free to move longitudinally.

Light weight disk 36 with a section removed from the central portion thereof corresponding generally to the outline of driver member 25 so that it can receive the same therein, is utilized as a contact carrier. As seen best in FIG. 3 contact carrier 36 is formed to receive the cross-sectional configuration of driver body 29 and to receive radial projecting portion'iitl thereof within cutout section 37 of carrier member 36. Carrier member 36 is disk-like and has a depth substantially equal to the width of helically grooved channel 12 of the liner Carrier member 36 is formed of a light weight material, preferably a plastic, which is non-conducting. An edge thereof at section 36 is received within slot 35' of moving stop 35. The moving stop is preferably metallic and the slot 35 formed therein is preferably of sufiicient width that section 36' of the carrier member 36 is maintained therein relatively snugly. Resilient contact arm 38 is fastened at one end 39 by means of bracket 40 and eyelets {i-l to contact carrier 36 and electrical lead 42 is electrically in contact with contact member 38.

Contact 38 is designed to engage coil 11 when sector 3'6 of contact carrier 36 is engaged in slot 35' of moving stop 35 and groove 12 of liner it). Further, contact 33 is positioned on contact carrier 36 so that the resiliency of arm 38 will yieldingly urge sector 36 Within groove 12. In order to accomplish this, the point whereat contact 38 will engage resistance wirelll is displaced from sector 36? which is to be urged'thereby'within groove 12.

With such configuration when the driver member 25 i isdisposed with its ends supported in the appropriate bearings, rotation of shaft 24 will result in the transmission of a rotational force to contact carrier 36 through the radially projecting portion 30 of driver 25. This force of the disk in the groove in the proper place giving maxi:

mum drive force. The helical groove in which the .contact carrier 36 travels is displaced from the coil 11 itself and as a result the formation of dust or dirt of any kind within the groove 12 cannot affect the electrical characteristics of the device. Additionally, the concentricity of the major components of the device results in a highly.

accurate assembly.

Thus, among others, the several objects in the invention as specifically aforenoted, are achieved. Obviously, numerous changes in construction and rearrangement of parts might be resorted to without departing from the spirit of the invention as defined by the claims.

i claim:

1. A multi-turn potentiometer including in combination a cylindrical hollow casing, a helical groove formed on the inner surface of said casing, a resistance wire consisting of a plurality of continuous turns in the form of a helix disposed in the cylindrical plane of said casing with turns thereof separated by portions of said helical groove,

a driver member rotatably supported within said casing with its axis of rotation concentric with the axis of said groove and said wire, a longitudinal slot formed in said driver member, a contact carrier, a portion of said contact carrier having the Width of said groove and disposed therein, a second portion of said contact carrier disposed within said slot, means preventing relative rotational will tend to turn contact carrier 36 and move it with groove 12 serving as a track therefor so that contact 38 will traverse wire 11 and such traverse can be accomplished throughout the length of wire 11.

Fixed stops 43 and 4-4 are provided at either end of channel 34 in the completed assembly. These stops are preferably metallic and have surfaces facing channel 34 so that at either of the extreme positions of contact carrier 36 movable stop member 35 will abut stop 43 or 44 to prevent further movement of the contact carrier 36 longitudinally. Stop 43 is rigidly fastened by any suitable means to the bottom of housing 15 in the general vicinity of bearing 23. Stop 44 is rigidly fastened to cover 26 by'any suitable manner in the vicinity of bearing member 28.

Electrically the circuit of the potentiometer shown and described herein is diagrammatically illustrated'in FIG. 4. In FIG. 4 the various points of interest are given numbers corresponding to the numbers given the posts. on terminal board 20 in FIG. '1. In FIG. 4, however, in order to avoid error, the corresponding numbers are set forth as prime numbers and as tap points on resistance 11' which is a diagrammaticindication of the resistance of wire 11. Physically, post 16 is electrically connected to collector arm 45 shown in FIG. l which is designed to engage collector 46 which is electrically connected with .arm 38. For this purpose wire 42 is utilized and cutout portion 4'7 of body 29 Post 17 is connected electrically to one end of wire 11 and post19 is connected to the remaining end. Post 18 is an optional terminal which can be utilized if desired.

With such a device many advantages result. The device is low in backlash and there is very little relative rotational motion between the various parts. The metal inmovement of said contact carrier and said driver member, a contact arm rigidly supported by said contact carrier and in engagement with one turn of said cell, and conducting means forming an electrical circuit with said contact arm and said coil.

.2. A multiturn potentiometer in accordance with claim 1 in which the contact carrier is a lightweight electrically non-conductive disc section and the contact arm is a resilient electrical conductor rigidly fastened at one end to a surface of the contact carrier so that it engages the coil adjacent the portion of the helical groove in which the contact carrier is disposed.

3. A multiturn potentiometer in accordance with claim 1 in which the casing is formed with one surface at each end against which the contact carrier can abut upon reaching the extremity of travel in that direction.

7 4. A multiturn potentiometer in accordance with claim 2 in which the portion of the contact carrier within the helical groove is displaced from the contact arm whereby it is yieldingly urged thereby within saidhelical groove.

5-. A 'multiturn potentiometer in accordance with claim 4 in which the contact carrier is formed with a radial .slot and the driver member is formed with a radialpro- .jection disposed within said radial slot in substantiallya glove fit by which turning moments applied to the driver member can be imparted to the contact carrier.

6. A multiturn potentiometer including in combination a cylindrical hollow casing, a helical groove formed on the inner surface of said casing, a resistance wire con tact carrier having a portion within said recess and a portion in said helical groove, means preventing relative rotational movement of said contact carrier and said driver member, a contact arm rigidly supported by said contact carrier and in engagement with said coil, and conducting means forming an electrical circuit with said contact arm; and said coil. I, V V

7. A multiturn potentiometer in accordance with claim 6 in which the casing is formed with one surface at each end against which the sliding stop can abut upon reaching the extremity of travel in that direction.

8. In a mnltiturn potentiometer a cylindrical hollow casing, a resistance wire consisting of a plurality of continuous turns in the form of a helix concentric with said casing, a helical groove formed in said casing throughout its efiective length, a driver member rotatably supported within said casing and said wire with its axis of rotation concentric with the axis of said casing, a contact member mounted on said driver member so that it is longitudinally movable relative thereto and maintained against rotational movement relative thereto and a portion of said contact member disposed within said helical groove whereby rotation of said driver member can cause said contact member to move longitudinally and traverse the turns of said resistance wire, said contact member being formed with an irregular slot therein and said driver member is formed to be received in said slot, and a longitudinal groove is formed in said driver member and said contact member is formed with a section thereof to be movably disposed in said longitudinal groove. I

9. In a multiturn potentiometer, a cylindrical hollow casing, a resistance wire consisting of a plurality of continuous turns in the form of a helix concentric with said casing, a helical groove formed in said casing throughout its efiective length and separating each turn of said resistance wire from adjacent turns, a driver member rotatably supported with its axis of rotation concentric with the axis of said casing, a contact member mounted on said driver member so that it is longitudinally movable relative thereto and maintained against rotational movement relative thereto, a longitudinal groove formed in said driver member, a section of said contact member movably disposed in said longitudinal groove, and a portion of said contact member disposed within said helical groove whereby rotation of said driver member can cause said contact member to move longitudinally and traverse the turns of said resistance wire.

10. In a multiturn potentiometer, a cylindrical hollow casing, a resistance wire consisting of a plurality of continuous turns in the form of a helix concentric with said casing, a helical groove formed in said casing throughout its effective length and separating each turn of said resistauce wire from adjacent turns, a driver member rotatably supported with its axis of rotation concentric with the axis of said casing, a contact member, an irregular slot formed in said contact member, said driver memher being formed to be received in said irregular slot so that said contact member is longitudinally movable relative thereto and maintained against rotational movement relative thereto and a portion of said contact member disposed within said helical groove whereby rotation of said driver member can cause said contact member to move longitudinally and traverse the turns of said resistance wire.

References Cited in the file of this patent 2,813,956 Sorber Nov. 19, 1957 Beckman Nov. 30, 1948