US3323094A

US3323094A - Potentiometer terminal

Info

Publication number: US3323094A
Application number: US385847A
Authority: US
Inventors: Luca Paul V De; Harvey E Senft
Original assignee: Markite Corp
Current assignee: Markite Corp
Priority date: 1964-07-29
Filing date: 1964-07-29
Publication date: 1967-05-30
Anticipated expiration: 1984-05-30

Description

y 30, 1967 P. v. DE LUCA ETAL 3,323,094

POTENTIOMETER TERMINAL Filed July 29, 1964 F K3. 4B

INVENTORS PAULVDQ LUCA BY HARVEY 5. savrr MM Kw ATTORNEY United States Patent 3,323,094 POTENTIOMETER TERMINAL Paul V. De Luca, Jackson Heights, and Harvey E. Senft, White Plains, N.Y., assignors to Markite Corporation, New York, N.Y.

Filed July 29, 1964, Ser. No. 385,847 13 Claims. (Cl. 338162) In extremely small potentiometers, which are commonly used where weight and size are factors, the internal area available for the manipulation of assembly tools is quite limited. Accordingly, past methods of providing the aforementioned external-internal conductive paths have been awkward and tedious, representing a long standing problem in the industry.

There also exists particularly stringent requirements for ruggedness, accuracy and reliability for potentiometers which are incorporated in space vehicles, computers and other demanding applications. Adding to the problem is the fact that the components involved are both delicate and costly.

The terminals must withstand torsional and tensile loads during and after assembly and must retain electrical continuity over a wide range of temperatures. The difficulties inherent in assembling components of this nature make it imperative to improve the techniques whereever possible.

The present invention is directed towards this end by providing improved connecting means which may be employed in high precision potentiometers. By way of example, there will be disclosed hereinafter the employment of the terminal assembly, comprising the present invention, in a potentiometer. The terminal passes through the housing wall so that, in one embodiment, the internal end of the terminal which is split or bifurcated will be at right angles to and will straddle a comolded, electrically conductive stud in electrical connection with the resistive element of the potentiometer. Alternatively, the terminal may be formed without the bifurcating slot and the conductive stud would, in this case, be a wire secured to the resistive element of the potentiometer. In either embodiment the terminal is provided with a longitudinal bore and a transverse, annular groove axially displaced from the bored end of the terminal. One edge of the annular groove and the bored end of the stud define that portion of the terminal which subsequently experiences deformation. A flanged head is also provided which, in cooperation with one confronting edge of the annular groove, defines an axial terminal only slightly greater than the wall thickness through which it passes.

The terminal body is then crimped at a point between the annular groove and the bored end of the terminal. The body of the terminal is thereby made larger than the hole in the wall through which the terminal was originally inserted thus preventing longitudinal movement of the terminal. Solder is then melted to flow in and fill the remaining gap between the stud and the inside surface of the terminal bifurcation. In place of solder, electrical connection may be made by welding the terminal and stud after crimping. A suitable bonding agent, such as epoxy resin, may then be applied to the internal and external ends, respectively, of the terminal to further mechanically secure it to the potentiometer housing wall.

It is therefore an object of this invention to provide an improved terminal assembly suitable for a small precision electrical device.

It is another object to provide improved connection means between internal taps and external terminals of a potentiometer.

An additional object is to provide an improved terminal and terminal connecting means consistent in size with small potentiometers and yet adaptable to assembly by conventional techniques.

Still another object is to provide an improved terminal and terminal connection means of small size that are convenient to assemble at a low cost.

A further object is to provide a small but rugged potentiometer terminal that may be assembled by inexpensive techniques.

These and other features, objects and advantages of the invention will, in part, be pointed out with particularity and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawing, which forms an integral part thereof.

In the various figures of the drawing, like reference characters designate like parts.

In the drawing:

FIG. 1 is an end elevation of a rotary potentiometer assembly incorporating the present invention;

FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1;

FIG. 3A is an enlarged detail view of an external terminal embodying the concept of the present invention, the terminal being shown in relation to a potentiometer stud prior to crimping;

FIG. 3B is a transverse end elevation view taken along line 3B3B of FIG. 3A;

FIG. 4A is an enlarged view similar to FIG. 3A but subsequent to crimping and rotated degrees about the longitudinal terminal axis. The deformed portion of the assembled terminal, as well as a portion of the housing and the stud, are shown; and

' FIG. 4B is a transverse end elevation view taken along line 4B4B of FIG. 4A.

In FIG. 1 and FIG. 2, there is shown a compact, precision type rotary potentiometer 10 employing

radial terminals

12a, 12b, 12c and 12d. Shaft 14 is coaxial and concentric with

cylindrical housing portions

16 and 18 and is suitably journaled therein by means of

bearings

20 and 22, respectively. Servo flange 24, in combination with a dog type clamp C and screws S, represent a conventional means for mounting potentiometer 10 to panel P. A disc shaped, insulating base member 26 is sandwiched between and secured concentrically with

housing portions

16 and 18 by means of screws 28. As may be seen in FIG. 2, the heads of screws are contained in recesses formed in housing portion 16 and the shanks of the screws pass through clearance holes 30 formed in base member 26. The ends of screws 28 are engaged "in threaded apertures 32 formed in housing portion 18.

FIG. 1 also illustrates the shape and position of a comolded, conductive resistive track 34, which is coaxial and concentric with shaft 14. Conductive paths 36a and 36b, are aifixed to base member 26 and contact arcuate track 34 proximate the ends thereof. The short, remaining are 38 is filled with an insulator plastic to electrically isolate the track ends from each other and to permit continuous 360-degree rotation of the wiper contacts.

Brush block 40 is rigidly secured to shaft 14 by means of set screw 42. The bush block is comprised of an inner sleeve 44, an intermediate, insulating sleeve 46 and an outer, conductive sleeve 48. A wiper assembly comprising arm 50 and precious metal contact 52 is secured to the brush block for rotation therewith and is in sliding contact with track 34. Thus, rotation of shaft 14 will cause rotation of the brush block and the wiper assembly causing a variance in the output voltage of'the potentiometer corresponding to the angular displacement of the shaft as measured between one terminal and the Wiper. Additionally, there is integrally formed on the brush block a hub portion 54, concentric and rotatable with shaft 14 and in electrical contact with sleeve 48. A hairspring wiper 56, secured to a stud which will be fully described hereinafter, is located such that its spaced legs ride on rotating V-shaped outer surface of hub 54.

Studs 58a, 58b, 58c and 58d are molded into base member 26 and extend from the face thereof opposite track 34. Studs 58a and 58b are in electrical contact with conductive paths 36a and 36b and with terminals 12a and 12b, respectively. Studs 58c may be positioned in the insulator plastic between studs 58a and 58b in electrical contact with terminal 12c and stud 58d, by way of example, may be a center tap situated at the midpoint of the resistive trackin electrical contact with terminal 12d. In the embodiment illustrated, hairspring wiper 56 is soldered to stud 580.

As shown in FIG. 3A and FIG. 3B, terminal 12 is a multidiameter rod having one end portion 60 bifurcated by slot 62. Axial bore 64, which is of the same size as or is slightly larger in diameter than slot 62, extends inwardly from end 60 past a reduced diameter, thin walled portion 66 and terminates in the area of knurled body portion 68. In orderto simplify the manufacturing techniques, the terminal is further provided with an additional reduced diameter portion 70, adjacent body portion 68, as Well as an enlarged diameter 72 and a shank 74. Reduced diameter portion 70 is not essential; it is convenient to machine it that Way in order to avoid a fillet between the shank of the terminal and the flange.

Terminal 12 is secured into a suitably sized radial opening 25 in the annular, flange portion 26a of base member 26 which, in this embodiment, forms a part of the housing wall. Body portion 68 is knurled to provide a snug fit with radial opening 25 when the enlarged diameter 72 is seated on the outside surface of flange 2611. When using a relatively brittle phenolic plastic for the housing, the CD. of the knurling and the ID. of the radial opening are sized for a 0.001" to 0.003" clearance. Where a softer material forms the Wall it is practical to pressfit the terminal in place. Once installed in a straddling relationship about one of the studs, end portion 60 is crimped so that bore 64 is collapsed around the stud in the area of slot 62. At the same time and by means of the aforementioned crimping action, wall 66a of annular groove 66 is also distorted into a noncircular shape. The enlarged surface of wall 66a then abuts the inner face of flange 2611. It should be noted that the thin walled, annular groove 66 prevents the transmission of the crimping deformation from end portion 60 to body portion 68. Reduced diameter portion 66 is weak in comparison to the other sections.

The result of the crimping is best illustrated in FIG. 4A and FIG. 4B wherein it will be seen that in addition to being closed around the conductive stud, end portion 60 and particularly the portion thereof proximate groove 66 has assumed a somewhat oval shape. That is, after crimping, end portion 60 and wall 66a have a major diameter D and a minor diameter d. The major diameter is larger than the hole in the wall of the potentiometer housing and the terminal is captured between Wall 66a of annular groove 66 and flange 72. It should be noted that FIG. 4A is rotated 90 degrees about the longitudinal axis of the terminal with respect to FIG. 3A.

In a preferred embodiment, an epoxy resin is applied to the inside surface of flange 26a in the vicinity of the terminal. By capillary action, the epoxy flows through the channels formed by the knurling of the body portion 68 and out between enlarged diameter 72 and the housing Wall to form a bead thereabout. The use of epoxy helps to prevent both withdrawal of terminal 12 through flange 26a and twisting of the terminal.

Referring once again to FIG. 3A, it will 'be seen that there is a gap or pocket 76 between the end of slot 62 and the stud which, for example, is shown as 58a. Gap 76 accommodates the solder so that a highly reliable electrical contact may be made. Thus a large glob of solder put over the whole assembly is not needed and is, in fact, undesirable since an excess of solder is likely to drop back into the potentiometer when an electrical lead from a utilization device is soldered to shank portion 74 of terminal 12. Alternatively, the internal end of the terminal may be spot welded to the conductive stud.

By way of example, studs such as 580 are approximately 0.30 inch diameter and the terminal slot 62, between

legs

60a and 60b of bifurcated end 60, is approximately 0.035 inch wide. Crimping bore 64 may range from 0.030 inch diameter to 0.040 inch diameter while gap 76, between the end of the slot and the stud, may range from 0.005 inch to 0.015 inch. Terminals 12 may be readily fabricated from /2 hard brass.

In an alternative form of construction, the bifurcating slot is omitted but all other features of the terminal remain the same including the use of an epoxy resin. That is, the axially bored end of the terminal comprises a crimping portion followed by an annular groove and a knurled length. Once again the combined axial length L of the groove and the knurling is only slightly greater than the wall thickness W of the potentiometer housing. In this embodiment, the stud conductively secured to the resistive element of the potentiometer is in the form of a wire which is inserted into the axial bore of the terminal prior to crimping. The wire may then be either soldered or spot welded into the terminal. As in the previous embodiment, crimping of the forward, axially bored end of the terminal causes the forward Wall of the annular groove to be enlarged. The terminal is thereby captured in the potentiometer Wall between the distorted end Wall of the annular groove and the underside of the flange.

From the foregoing description, it will be seen that connection of the internal elements of a potentiometer to external terminals has been greatly simplified without any sacrifice in accuracy or reliability. The points of soldering are fully exposed and accessible so that the small and delicate components are in no danger of damage. The soldering or welding may be done to the periphery of the base member on the side opposite that of the resistive track. The terminal itself is a relatively inexpensive part to fabricate. The method of assembly requires no special skills over and above those'of the average assembler. Knowing the angular position of each stud, it is a simple procedure to index the flange portion of the base member to accurately align the radial holes required for the terminals.

A feature of the present invention is that the terminal may be positioned in the potentiometer wall With the crimped portion either inside or outside the housing and the head beyond the flange can take any convenient shape. Furthermore, the improved terminal permits the use of simple pliers as the crimping tool, it being another feature that a single tool closes the axial bore of the terminal about the conductive stud and also distorts the terminal so that it cannot be pulled out. The improved terminal of the present invention has particular utility in a small, compact potentiometer wherein conventional flaring tools cannot be used in the limited space so as to flare over the end of a conventional hollow terminal.

There has been disclosed heretofore the best embodiments of the present invention contemplated and it is to be understood that various changes and modifications may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. A one-piece electrical terminal adapted for insertion into an aperture wall, said terminal comprising:

(A) a first deformable tubular section having means to receive an electrically conductive member therein;

(B) a second substantially nondeformable tubular section having a small outer diameter than that of said first section, said second section extending axially from said first section and being characterized by a wall thickness less than that of said first section;

(C) a third section of greater cross sectional dimension than that of said second section and extending axially from said second section to define a juncture therebetween; and

(D) an enlarged flange portion formed proximate said third section, said flange portion being disposed in a plane transverse said second and third sections,

(E) said third section and said second section of said terminal being disposed Within the wall aperture in the assembled condition.

2. The terminal according to claim 1 wherein said third section is knurled.

3. The terminal according to claim 1 wherein the axial dimension between the juncture of said first and second sections and said transverse 1y greater than the thickness of the apertured wall.

4. The terminal according to claim 1 wherein said first section is longitudinally slotted in a diametric plane to define a pair of spaced legs, the slot being open at one end and closed at the other end.

5. The terminal according to claim 4 wherein the diameter of the axial bore is at least as large as the width of the axially extending slot.

6. A potentiometer comprising:

(A) a housing having an apertured Wall;

(B) a support member mounted within said housing;

(C) a resistance element carried by said support member;

(D) a shaft rotatably journaled in said housing;

(E) takeoff means secured to said shaft for rotation therewith, said takeoif means being arranged to slide on said resistance element;

(F) stud means carried by said support member, said stud means being in electrical connection with said resistance elements; and

(G) one-piece terminal means disposed in the aperture of said housing Wall, said terminal means comprising:

(I) a noncircular, first tubular section having flange portion is slightmeans to r e' 'd t d 5.0

cc ive sa1 s u means 1n electrical RICHARD M. WOOD, Primary Examiner connection therein; (II) a second tubular section having its outer dimensions less than those of said first section, said second section extending axially from said first section and being charcterized by a Wall thickness less than that of said first section;

(III) a third section of greater cross sectional dimension than that of said second section and extending axially from said second section to to define a juncture therebetween; and

(IV) an enlarged flange portion formed proximate said third section, said flange portion being disposed on one side of said housing wall in a plane transverse said second and third section,

(a) the major dimension of the noncircular, first tubular section being greater than the aperture in said housing wall,

(b) said third section and said second section of said terminal being disposed in the wall aperture of said housing in the assembled condition.

7. The combination in accordance with claim 6 wherein said noncircular first tubular section of said terminal is disposed within said housing.

8. The combination in accordance with claim 6 wherein said third section is knurled.

9. The combination in accordance with claim 6 wherein the axial dimension between the junction of said first and second sections and said transverse flange portion is slightly greater than the thickness of the apertured Wall.

10. The combination in accordance with claim 6 wherein said first section is longitudinally slotted in a diametric plane to define a pair of spaced legs, the slot being open at one end and closed at the other end.

11. The combination of claim 8 wherein a cement is disposed in the space between said knurl and the inside surface of the Wall aperture.

12. The combination in accordance with claim 11 wherein said cement is an epoxy resin.

13. The combination of claim 10 wherein the diameter of the axial bore is at least as large as the width of the axially extending slot.

References Cited UNITED STATES PATENTS 1,449,727 3/ 1923 Bowman.

2,464,405 3/ 1949 Knauf.

2,904,767 9/1959 Vacha 338l62 X. 2,909,758 10/1959 Modrey 33922O 2,962,691 11/1960 Mande et al 339-276 X 3,093,435 6/1963 Johnson 339-276 J. G. SMITH, Assistant Examiner.

Claims

1. A ONE-PIECE ELECTRICAL TERMINAL ADAPTED FOR INSERTION INTO AN APERTURE WALL, SAID TERMINAL COMPRISING: (A) A FIRST DEFORMABLE TUBULAR SECTION HAVING MEANS TO RECEIVE AN ELECTRICALLY CONDUCTIVE MEMBER THEREIN; (B) A SECOND SUBSTANTIALLY NONDEFORMABLE TUBULAR SECTION HAVING A SMALL OUTER DIAMETER THAN THAT OF SAID FIRST SECTION, SAID SECOND SECTION EXTENDING AXIALLY FROM SAID FIRST AND SECTION AND BEING CHARACTERIZED BY A WALL THICKNESS LESS THAN THAT OF SAID FIRST SECTION; (C) A THIRD SECTION OF GREATER CROSS SECTIONAL DIMENSION THAN THAT OF SAID SECOND SECTION AND EXTENDING AXIALLY FROM SAID SECOND SECTION TO DEFINE A JUNCTURE THEREBETWEEN; AND (D) AN ENLARGED FLANGE PORTION FORMED PROXIMATE SAID THIRD SECTION, SAID FLANGE PORTION BEING DISPOSED IN A PLANE TRANSVERSE SAID SECOND AND THIRD SECTIONS, (E) SAID THIRD SECTION AND SAID SECOND SECTION OF SAID TERMINAL BEING DISPOSED WITHIN THE WALL APERTURE IN THE ASSEMBLED CONDITION.