US3729817A

US3729817A - Method of making rotatable element potentiometer

Info

Publication number: US3729817A
Application number: US00182997A
Authority: US
Inventors: Rouen J De; K Baldwin; H Martin
Original assignee: Bourns Inc
Current assignee: Bourns Inc
Priority date: 1971-09-30
Filing date: 1971-09-23
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01
Also published as: NL7206780A; FR2153227B3; DE2226317A1; GB1367839A; FR2153227A1

Abstract

A method of producing a potentiometer by advancing a long thin sheet of metal progressively through sets of die means at respective stations at which uniformly spaced registry holes are punched, other portions of material are punched out by each of successive die means to remove metal to commence formation of terminal means, an edge portion of the strip is thinned as by spanking to provide for formation of thin work-hardened resilient contact fingers, material removed or formed by additional die means and integral contact leaves and terminals formed, one or more contact members sheared to form at least one multi-finger contact member, the contact members and fingers bent to stand up from the strip, potentiometer housing bodies molded about portions of the strip to provide a body at each station of the strip, the upstanding contact members cupped to form respective sets of contacts, rotatable ceramic members which cermet resistive elements and slip-ring conductor sectors thereon inserted into respective housing bodies, covers applied to the bodies and ultrasonically sealed thereto, and the terminal means freed by shearing from the strip to separate individual potentiometers from the strip; and the product produced by the process.

Description

United States Patent 1191 Primary ExaminerCharles W. Lanham Assistant ExaminerV. A. DiPalma Attorney-Fritz 8. Peterson De Rouen et al. 1 May 1, 1973 METHOD OF MAKING ROTATABLE ELEMENT POTENTIOMETER [57] ABSTRACT [75] In en o s: Jo ph e o n g; ell- A method of producing a potentiometer by advancing neth B. Baldwin, Corona; Henry F. a long thin sheet of metal progressively through sets of Martin, Rialto, of Califdie means at respective stations at which uniformly [73] Assignee: Bourns, lnc., Riverside, Calif. registry holes are punched other Portions of material are punched out by each of successive die [22] Filed: sept' 1971 means to remove metal to commence formation of [21] Appl. No.: 182,997 terminal means, an edge portion of the strip is thinned as by spanking to provide for formation of thin work- I hardened resilient contact fingers, material removed [52] US. Cl. ..29/6l(2):9/2592/;1143239471162 or formed by additional die means and integral com 1 1- 1m Cl 1c 17/00 tact leaves and termmals formed, one or more contact [58] Field i976 i 0 613 412 members sheared at least multl'finger 29/414 3 538/164 contact member, the contact members and fingers bent to stand up from the strip, potentiometer housing [561' References Cited bodies molded about portions of the strip to provide a body at each station of the strip, the upstanding con- UNITED STATES PATENTS tact members cupped to form respective sets of con- 2173186 9 1939 Swartz eta] ..29/610 i i matable ceramic {neqberS which cermct 3:374:536 3/1968 Schroeder et al... .....29/610 x elFmems f s 3,391,426 7/1968 Hugill ..29/527.1 x thereon Inserted respectlve housmg bodles- 3,402,464 9/1968 Hatch ..29/610 covers applied to the bodies and ultrasonically sealed 3, 36,8 /19 K m /4l7X thereto, and the terminal means freed by shearing 3,597,837 8/1971 Mack ..29/6l0 from the strip to separate individual potentiometers from the strip; and the product produced by the process.

5 Claims, 13 Drawing Figures Patented May '1, 1973 2 Sheets-Sheet :1.

m Em Q WM v Nmi O N f YNK ww Patented May 1, 1973 2 Sheets-Sheet 2 Ll/I l l\ t METI IOD OF MAKING ROTATABLE ELEMENT POTENTIOMETER BRIEF SUMMARY OF THE INVENTION A unique single-turn potentiometer of exceptionally low cost is produced by a unique process in which a flat strip of metal is advanced in step-by-step uniform advances through a series of die stations at each of which a respective one of successive die operations are performed and at the end of which operations are performed and at the end of which operations a potentiometer'housing body has been molded about portions of the strip and three potentiometer contacts, each integral with a respective terminal member, have been integrated with the body with the terminals protruding from the exterior of the body and the contacts from the interior. The molded housing body at that stage remains secured to one edge portion of the strip by the three terminal members, which have yet to be severed from the strip. At a succeeding station, a rotor comprising an insulative substrate of disc-like configuration bearing on its lower or interior face a resistance element, a return conductor or collector and terminal connection conductor means, is inserted into the body with a housing cover member and the cover member sealed to the body to retain the rotor and seal the interior of the housing. The substantially completed potentiometers are thereafter severed one by one from the strip by shearing adjacent the ends of the terminals; and, if testing or inspection is desirable, such further optional operations are performed. Either prior to severance from the strip or concurrently therewith, the terminal members may be bent to provide an alternative terminal configuration in which the terminals are disposed at an angle to the direction in which they extend from the body.

The rotor may alternatively be secured to a shaft, or may merely be provided with other means, such as a slot, to provide for its rotation by external means. The internal contact members, at least one of which preferably is sheared as noted to provide a plurality of resilient contacts, are so disposed in the housing body that as the rotor is placed in position in the body, the sets of contacts are each engaged and resiliently stressed by a respective one of the conductors or the resistive element. Also, the housing cover, which has a central aperture into which the shaft or other externally accessible actuating portion of the rotor extends, is of conformation such as to confine the rotor to rotation about an axis and to a position assuring proper interengagement between the contacts and the elements on the inner face of the rotor.

The cover and body sections of the potentiometer housing are provided with complementary interengaging formations which aid in proper juxtapositioning and hermetically sealing of those two parts together and for cooperative action in restricting rotation of the rotor to a desired extent of rotational movement. Since mechanical production of all of the terminals and internal contacts and their fixation in the housing body proceeds by machine operations substantially without manual operations, it is evident that a large proportion of the cost of assembly of the potentiometer is eliminated, and a great improvement in uniformity of the product is attained. Further, since the resistance element and. connections from the element and the return conductor are on the lower face of the rotor and are of cermet type, all manual operations relating to manufacture of the rotor and its element may be performed by automatic machinery, whereby to further decrease costs and to improve uniformity of the product.

The preceding brief summary of the invention indicates that it is a principal object of the invention to provide improvements in potentiometers and a method of manufacturing the same with a view toward reducing the costs of manufacturing and improve uniformity of the potentiometers.

Another object is to provide a potentiometer construction which eliminates much of the labor involved in assembly of the instrument, with concurrent reduction in cost and increase in uniformity of product.

Another object of the invention is to provide a potentiometer structure of simple construction adapted for automatic machine production.

An additional object of the invention is to provide a procedure for forming respective sets of potentiometer contacts with associated terminals as integral units of a single member of metal, forming potentiometer bodies about the member to provide a series of the latter with respective terminal sets and contact sets, whereby to reduce costs of manufacture and attain improvements in uniformity of the product.

Other objects and advantages of the invention are hereinafter made evident or set out in the following detailed description of a presently preferred embodiment, or in the appended claims. The preferred embodiment is illustrated in the accompanying drawings.

metal strip during a series of operational steps pe'rformed in accord with the procedure of the invention;

FIG. 2 is a lower face view of the potentiometer rotor structure used with the body assembly shown in FIGS. la-ld, at one stage of manufacture;

FIG. 2a is a view similar to FIG. 2 but at a subsequent stage of manufacture of the rotor;

FIG. 3 is a top face or plan view of the rotor structure shown in FIG. 2;

FIG. 4 is a side view of the rotor structure depicted in FIGS. 2 and 3;

FIGS is a view similar to FIG. 3 but showing a seal member installed;

FIG. 6 is a pictorial view of the exemplary potentiometer housing cover, to somewhat enlarged scale;

FIG. 7 is a bottom view of the cover shown in FIG. 6, to approximately the same scale;

FIG. 7a is a fragmentary sectional view, with the sectioning as indicated by directors 7a-7a in FIG. 7; and

FIG. 8 is a pictorial view ,of a completed exemplary potentiometer manufactured according to the process or method of the invention.

Referring to the drawings generally, it may be noted that the procedure according to the invention involves advancing of a strip of metal in measured steps while at each ofa plurality of work stations or locations the strip in punched in various ways, portions work-hardened,

portions deformed and some removed, housing bodies molded on the strip, bending operations performed, other parts assembled into and on the body, and completed devices severed, the strip in the meantime serving as a vehicle for the components and concurrently to provide material for sets of contact-and-terminal members. FIGS. la, lb, and 1c shown a thin flat metal strip 20 which is advanced through a plurality of die-sets in step-by-step increments or unitlengths. In the interest of conservation of space in the drawings the die-set stations will be considered to be one unit-length of strip apart, center-to-center, whereas in actual practice the die-sets will generally be variously spaced along the strip 20. The result of operations at a particular dieset station will only be portrayed as the difference between the portrayal at that station and that at the immediately preceding station; and the stations are denoted by a respective station designation shown adjacent the strip in the drawing, e.g., S2 for the second station. As a preliminary operation, a portion 26 adjacent one edge of the strip is thinned, as by milling or grinding, as indicated at the right in FIG. 1a. The strip, which is of annealed material, may be so supplied by the supplier. The thinned portion 26 is provided for the formation of relatively thin contact fingers. Referring further to FIG. la, it is noted that at the first die-set station, S1, the die means operates to punch a pair of guide or registry holes 22, 22a, and to remove a rectangular portion of material at 24. At the next (second) die-station, S2, which as previously noted may be spaced by a desirable distance mx from the first station (wherein m is a whole number and x is the center-tocenter distance between successive holes 22), additional punching is performed, as indicated at 25.

At the third station S3, a perforation 28 is made, and at station S4 a perforation 30 is made. At station S5 a large portion of the thinned portion of the strip is removed, leaving a window or perforation 32 and a very narrow edge portion 32a which is readily deformable. As indicated, the strip is of annealed alloy, hence is relatively soft and easily punched, but is capable of work hardening. At station S6, trimming operations occur, to assure precise edges at desired locations, and the remainder of window 32 is produced. At stations S6, S7, S8 and S9 the remaining finger-like portions of the thin portion 26 of the strip, denoted 34 in station S6, are work-hardened by swaging or hammering, with some lateral expansion of the portions as indicated. The finger-like portions are to be formed into resilient contact members and hence they must be workhardened as noted to impart resilience to the material.

At a selected one of stations S7, S8 and S9 (FIGS. 1a and lb), or at a separate station between two of those stations, an elongate aperture 36 (here first shown at S7 in the interest of conservation of drawing space) is produced; and a second of such elongate apertures, 37, is subsequently produced as shown at S8. Concurrently, or at other intermediate die-set stations, trimming operations, such as trimming of the margins of apertures 24 and as indicated at 57-88, are performed. Similarly, at stations S8Sl0, the edges of material of portions 34 are trimmed and edge portion 32a is removed. Thus at station S10 there are presented clearly trimmed apertures 24-25, 36-37, and 28-30. At station 811 a slitting or shearing operation is performed, producing a pair of slits 38-39 between apertures 28 and 30, thus producing a middle contact finger 40a of a set of three such fingers disposed for engagement with a resistance element. At station S12 aperture 28 is transformed, by removal of material at both ends, into a stepped slot opening into aperture 24, to leave outstanding a contact member 42 connected to the strip by a base portion 42b. At station S13 a similar operation removes material at both ends of aperture 30, leaving a central three-limbed contact member 40 comprising three fingers 40a, 40b and 400, and further leaving a third contact member 44.

At station S14 the three contact members are trimmed at their outer ends, and at station S15 (FIG. 10), the ends of the members are cupped or dimpled to provide curved points or contacts at the extremities of the respective fingers 40a, 40b and 400 and at the extremities of members 42 and 44. At station $16 the outer ends of the three contact members 40, 42 and 44 are sharply bent at right angles to the general plane of the strip, so that they extend upwardly away from their respective bases. At a subsequent station, here denoted S17, strip material encircling aperture 22a is removed; and at the next station strip material at the other side of the group of fingers is removed. Thus, as shown at station S18 there is left outstanding from the base of the strip an array of three legs 46, 48 and 50 each integral with a respective contact member 42, 40 and 44 and all interconnected by bridges 52 and 54 and by the remainder of the base of strip 20.

The legs 46, 48 and 50 are dimensioned and spaced to form respective potentiometer terminal members. The bridges 52 and 54 serve to precisely hold in proper spatial relationship the three contact members 40, 42 and 44 for the next step of the sequence of operations. At station S19 a potentiometer housing body 56 is molded about the base portions of the contact members, leaving the upstanding contact ends thereof protruding upwardly from the floor 56f of a circular cavity 560 formed in the body. At station S20 the up-, standing portions of the contact members are bent over in a direction away from the remaining base of strip 20 and into angular relationship with the floor of the cavity.

As is evident, at station S20 all of the contact members are firmly embedded, at their bases, in the material of the housing body; and hence are firmly held in proper position for engagement of their respective contact points by conductive or resistive elements on a rotor presently to be described. Further, each of the contact members is integral with a respective one of the legs 46, 48 and 50, which are designed to become potentiometer terminals. At a subsequently reached station, not shown but disposed between stations S20 and S21, the interconnecting bridges 52 and 54 are punched or sheared out, leaving terminal members 46t, 481 and 50t supporting the housing body from the lower edge portion of strip 20 as shown at station S21; At station S21 a rotor 60, which is depicted in detail in FIGS. 2a-5, is inserted into a housing cover (depicted in FIGS. 6 and 7), and the housing cover is disposed on the housing body and ultrasonic energy applied to seal the cover in place. As will be evident, each of the latter operations or procedural steps may be performed at respective different stations, and the manufacture and assembly of the rotor may be effected offline in a ceramics process known in the trade, the two sets of operations occurring in procedures and sequences depending upon the arrangements of apparatus. Following sealing of the cover to the housing base, the potentiometer assembly is severed from the strip by severance of the three terminal members 46!, 48t and 50t between the body and the strip. As is evident, extreme uniformity of the product is attained because of the precision with which the components are formed, held in exact juxtaposition and so maintained during all of the forming, molding, and assembling operations. Also, since a minimum number of manual manipulations or assembling operations is in volved, costs are grossly reduced while concurrently all of the defects and troubles associated with manual operations are avoided. Thus a much more uniform and superior potentiometer is produced at lower cost.

In FIG. 2 there is depicted a rotor 60 of insulati've material such as fired alumina, on the lower face of which is fired or otherwise formed an outer conductive element 60a and an electrically separate inner conductive element 60b. These conductive elements are positioned to engage contact points of members 42 and 44, respectively, and are functionally arranged to serve as rotor-borne slip-ring type terminations for the rotorcarried resistance element of the potentiometer. The upper or outer face of, the rotor 60 is depicted in FIG. 3. It is of special form, including an upstanding circular formation 60f adapted to closely fit in and be guided by a central circular aperture 70a (FIG. 6) formed in the housing cover 70. The upstanding circular formation may be extended into a shaft formation or may be short as illustrated, and forms an externally accessible means for rotating the rotor. The upper face of the rotor also comprises a flat circular seat 60s (FIG. 3) on which an O-ring seal 62 (FIG. 5) is seated. The O-ring bears against the inner surface of cover 70, encircling the aperture 70a and thus serving to seal the interior of the housing against ingress of foreign material. The circular seat 60s'is extended radially outwardly to provide a stop member 60t (FIGS. 4 and 5) which is disposed to engage a complementary fixed stop abutment 70s (FIG. 7) formed on the inner wall of cover 70. Thus rotation of the rotor is restricted to somewhat less than 360, as dictated by the angular dimensions of the devices 60t and 70s.

As indicated in FIG. 7a, the rotor is adapted to be held with the base of the circular formation 60f confined in the circular aperture 70a of the cover with a step 60p (FIG. 3) of the upper face of the rotor bearing against the interior surface 70m (FIG. 7) of the cover, by upward pressure of shelf means 56s of housing body 56 against the lower face of the rotor. That upward force or pressure further slightly deforms the O-ring seal 62 to insure good sealing of the housing against ingress of foreign material. As the cover 70 is pressed into place on housing base 56, the contacts of members 40, 42 and 44 are brought into contacting engagement with elements 60r. 60a 60b, respectively.

To precisely position the housing cover 70 and its entrained rotor relative to the housing base 56 as the cover assembly is applied to the base, the latter is provided with a set of unsymmetri'cally disposed grooves 56p and 56q (FIG. lc, station 20), and cover 70 is formed with a complementary set of projections 70p and q (FIGS. 6, 7 and 8) which snugly seat in respective ones of the grooves. Preferably the ends of the projections are beveled or rounded whereby to aid in proper placement and registry of the cover and base as the cover is brought into position on the base. The cover is further provided with a sharp circular ridge 70r (FIG. 7) (which bears against a flat surface 56m (FIG. 1c station 21) when the housing members are brought together. While the two housing members are thus in contact and held together with clamping forces, .ultrasonic energy is applied to the cover around but exteriorly of the central aperture 70a, whereby the ridge 70r and adjacent contacted portions of the body are heated and the two members are fusion-united. In addition to the energy concentrating ridge 70r, the cover preferably also is provided with other such sharp ridge formations as indicated at 70w, 70x, 70y and 70z (FIG. 7). While not essential to the invention, provision of the additional ridge formations ensures excellent structural union of the housing cover and body members as the ultrasonic energy is applied. An important result is attained by virtue of of the employment of ultrasonic vibrations to generate the heat necessary to fusionunite the housing members, in combination with the particular structural relationship between the housing body, rotor, and housing cover. Referring to FIG. 7a, when the housing body 56 is supported as on a table or platform and an ultrasonically vibrated tool face is applied with force to the upper surface of cover 70 around, but notupon, portion 60f of the rotor,the sharp ridge formations 70r, 70x, etc., are subjected to extreme internal stress and become hot and melt, as do those portions of body 56 which the ridge portions contact. As fusion occurs, the cover 70 is forced downwardly to an extent approximately equal to the height of the ridges. Thus an annular portion 70z of the inner ceiling surface of cover 70, adjacent aperture 70a, is lowered into forceful contact with shelf 60p of the rotor; and under'the stress of the ultrasonic vibrations that annular ceiling surface becomes plastic and isbrought into exact conformity with the surface of the noted shelf. At the same time, the lower surface of the rotor is very firmly seated on the shelf 56s of body 56. Thus all differences due to allowable dimensional tolerances are eliminated, and precise fitting of the rotor in the housing is attained. The melted or plastic annular portion of the cover does not adhere to the rotor.

If desired, the terminal members 46t, 48! and SIM may be bent downwardly at right angles to their dispositions as shown in FIG. 8, whereby the potentiometer may be plugged into a circuit board or the like and disposed for operation from above, rather than from the side. Such bending can precede, or follow, severance of the potentiometer from the strip 20.

As will be evident, if it be desired that the contact members and terminals be gold-plated, the strip may be passed through a plating bath between selected stations. Alternatively, plating may be effected as the assembly moves away from the station at which bridges 52 and 54 are removed from between the terminals, or the entire strip may be plated prior to use. It is evident that the order in which certain steps of the described procedure are performed may be inverted or otherwise altered, without significantly changing the results accomplished. Also, it is evident that certain of the procedural steps may be combined into a single step.

Having thus described the presently preferred exemplary embodiment of potentiometer and method of producing the same, we claim:

1. A process for producing potentiometers, said process comprising:

moving a thin strip of electrically conductive material intermittently through each of a plurality of stations at which respective apparatuses are disposed; within a first group of said stations, producing perforations at determined distances apart along the strip to provide for accurate registration of the strip relative to apparatuses and to define unit lengths of the strip each such unit length being allocated to a respective potentiometer, and within the group of stations successively removing more material from between the first and second edges of the strip by punching perforations in the strip; within a second group of stations, spanking a portion of each unit length of material adjacent the first edge of the strip, to work-harden and impart resilience to those portions; further removing material from the spanked portions of the strip to produce therefrom a plurality of contact fingers each integral with the remainder of the strip; removing material from the strip adjacent the second edge thereof to produce a plurality of terminal members each integral with the strip and each integral with a respective one of the contact fingers; removing material from the strip adjacent the second edge thereof to produce a plurality of terminal members each integral with the strip and each integral with a respective one of the contact fingers; molding a housing body member about portions of the contact fingers and terminal members in respective unit lengths of the strip while leaving resilient contact portions of the contact fingers and end portions of the terminal members protruding from the body member and integral with the strip;

producing rotors with conductive and resistive members thereon, and producing housing cover members;

assembling a rotor and a cover member to respective body members; and

severing the potentiometers from the strip by shearing the terminal members adjacent the second edge of the strip.

2. A process according to claim 1, including the steps of dimpling the ends of the contact fingers and bending the fingers away from the plane of the strip prior to molding the housing body about portions of the fingers.

3. A process according to claim 1, including the steps of shearing at least one of the contact fingers to produce a multi-contact finger.

4. A process according to claim 1, including the steps of forming energy-concentrating ridge means on a sealing surface of one of the housing body and cover members, and applying pressure and ultrasonic vibratory energy to the cover member to seal the cover to the body member.

5. A process according to claim 4, including forming complementary upward] facing and downwardly facmg bearing surfaces on t e rotor and the housing body and housing cover members, and during application of pressure and vibratory energy, forcing the downwardly facing bearing surface on the rotor into firm bearing engagement with the upwardly facing bearing surface on the body member while forcing the downwardly facing bearing surface of the cover member into close conformity and engagement with the upwardly facing bearing surface on the rotor and creating heat and softening the bearing surface of the cover member whereby under applied pressure dimensional disparities are compensated and both pairs of said bearing surfaces are made to remain in close bearing contact.

UNITED STATES PATENT OFFICE CERTIFICATE CORRECTIUN Patent .No. 3, 729, 817 I Dated May 1', 1973 Inventoflg) Joseph R. DeRouen, Kenneth Br Baldwin, Henry F. Martin It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, Line 10, formed and at the end of which operations are per-" should bedeleted entirely. (duplicate) Column 6, Line 7 "(which"' should read 'whioh [remove parentheses] Column 6, Line 22'," Y'ivrirtu e of-of the .s'hould mad -virtue of the-.

Column -7, Line '18, "between the first" should read -between first-.

Column 7, Lines 32 thru 35, "removing material from the stripadjacent the second edge thereof to produce a plurality of terminal members each integral with the v strip and each integral with a respective one v f th tagt f ingers" should be deleted entirely C Signed and sealedthis 24th day of December 1974.

(SEAL) Attest:

MCCOY M- GIBSON JR. v 'c. MARSHALL DANN Attesting Officer Commissioner of Patents F0? powso (0459) y I. v v v I USCOMM-DC 6037B-P69 LS. GOVERNMENT PRINTING OFFDCE: I959 O-366-33 UNITED STATES PATENT ()FFIGE CERTIFICATE OF CQBEQTWN 3,729,817 Dated May 1, 1973 Patent No.

lnventofls) Joseph R. DeRouen, Kenneth B. Baldwin, Henry F. Martin a It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, Line 10, "formed and at the end of which operations are per-" Should be deleted entirely. (duplicate) Column 6, Line 7 "(which" should read -which-- [remove parentheses] Column 6, Line 22,- "virtue of of the" should read virtue of the.

Column 7, Line 18, "between the first" should read -between first.

Column 7, Lines 32 thru 35, "removing material from the stripadjacent the second edge thereof to produce a plurality of terminal members each integral with the strip and each integral with a respective one of the Contact fingers" should be deleted entirely Q Signed and sealed this 24th day of December 1974.

(SEAL) Attest:

icCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC ORM PO-1050 (10-69) x I n ulsfeovsnnnzur mmmm om

Claims

1. A process for producing potentiometers, said process comprising: moving a thin strip of electrically conductive material intermittently through each of a plurality of stations at which respective apparatuses are disposed; within a first group of said stations, producing perforations at determined distances apart along the strip to provide for accurate registration of the strip relative to apparatuses and to define unit lengths of the strip each such unit length being allocated to a respective potentiometer, and within the group of stations successively removing more material from between the first and second edges of the strip by punching perforations in the strip; within a second group of stations, spanking a portion of each unit length of material adjacent the first edge of the strip, to work-harden and impart resilience to those portions; further removing material from the spanked portions of the strip to produce therefrom a plurality of contact fingers each integral with the remaInder of the strip; removing material from the strip adjacent the second edge thereof to produce a plurality of terminal members each integral with the strip and each integral with a respective one of the contact fingers; removing material from the strip adjacent the second edge thereof to produce a plurality of terminal members each integral with the strip and each integral with a respective one of the contact fingers; molding a housing body member about portions of the contact fingers and terminal members in respective unit lengths of the strip while leaving resilient contact portions of the contact fingers and end portions of the terminal members protruding from the body member and integral with the strip; producing rotors with conductive and resistive members thereon, and producing housing cover members; assembling a rotor and a cover member to respective body members; and severing the potentiometers from the strip by shearing the terminal members adjacent the second edge of the strip.

5. A process according to claim 4, including forming complementary upwardly facing and downwardly facing bearing surfaces on the rotor and the housing body and housing cover members, and during application of pressure and vibratory energy, forcing the downwardly facing bearing surface on the rotor into firm bearing engagement with the upwardly facing bearing surface on the body member while forcing the downwardly facing bearing surface of the cover member into close conformity and engagement with the upwardly facing bearing surface on the rotor and creating heat and softening the bearing surface of the cover member whereby under applied pressure dimensional disparities are compensated and both pairs of said bearing surfaces are made to remain in close bearing contact.