US3399369A - Potentiometer having housing formed of electrically non-conductive material inculding integral hinge section and method of making the same - Google Patents

Description

GI- CULAKIS I 3,399,369 v I POTENTIOMETER HAVING HOUSING FORMED OF ELECTRICALLY I NON-'CONDUCTIVE MATERIAL INCLUDING INTEGRAL HINGE SECTION AND METHOD OF MAKING THE SAME Filed Aug 17 1966 Irroewr;

United States Patent 3,399,369 POTENTIOMETER HAVING HOUSING FORMED 0F ELECTRICALLY NON-CONDUCTIVE MA- TERIAL INCLUDING INTEGRAL HINGE SEC- TION AND METHOD OF MAKING THE SAME George Soulakis, Pasadena, Calif., assignor to Spectrol Electronics Corporation, City of Industry, Califl, a corporation of Delaware Filed'Aug. 17, 1966, Ser. No. 572,995 6 Claims. (Cl. 338-180) ABSTRACT OF THE DISCLOSURE Disclosed is a potentiometer having a resistance element, electrical contact, and lead screw for moving the contact along the resistance element all disposed within the cavity formed by an integral housing including a base member having side and end walls with a top hinged to one of the walls, the hinged top being held in place by heat forming opposed walls of the base.

This invention relates generally to variable resistors and more particularly to a potentiometer incorporating a unitary housing and which may cooperatively contain a lead screw for traversing a contact means over a resistance element.

: As a result of widespread developments in automatic control apparatus and other complex electrical systems, considerable demand exists for potentiometers to provide a variable voltage ratio. One common basic form of potentiometer employs a resistance element adapted to be connected across a source of electrical potential so that eachpoint along a contact path on the resistance element provides a different voltage. Various wiper arrangements have been proposed in the past to contact the resistance element at different points under control of a rotary shaft or other drive means. Of course, the mechanism for positioning the wiper must be supported for movement and such support is frequently attached and referenced to the housing of the potentiometer.

Over the years substantial progress has been made in reducing the cost and improving the structure of potentiometers. However, in general, the mechanism for supporting and driving the sliding contact has remained somewhat expensive to produce and assemble. In this regard, prior forms of lead screw potentiometers have usually required a delicate assembly operation in which the lead screw is carefully fitted or otherwise set within, the housing for relative motion and in proper alignment then the housing is fastened or adhesively sealed closed. Therefore, a need exists for an improved potentiometer structure, wherein delicate assembly operations may be somewhat avoidedand which potentiometer may be economically manufactured.

Accordingly, it is an object of the present invention to provide an improved variable resistance element.

It is another object of the present invention to provide a lead screw actuated trimmer potentiometer wherein a sliding contact is variously positioned by a lead screw which is rotatably supported in a housing that is of unitary construction and requires neither adhesives nor separate fasteners.

It is another object of the present invention to provide a lead screw actuated trimmer potentiometer including a unitary housing which may be formed as an' integral cast-.

ing and which provides bearing surfaces for the lead screw and facilitates simplified assembly of the potentiometer structure.

Another object of the present invention is to provide an improved lead screw potentiometer wherein a resistance Patented Aug. 27, 1968 Other and more specific objects and advantages of the present invention both as to its method of operation and to its organization will become apparent from a consideration of the following description taken in conjunction with the accompanying drawing which is presented by way of example only, and is not intended as a limitation upon the scope of the claims appended hereto and in which:

FIGURE 1 is a perspective view illustrating an assembled lead screw actuated potentiometer embodying a housing in accordance with the present invention, the top of which housing is also indicated in an open configuration in phantom;

FIGURE 2 is a perspective view illustrating the unitary housing of a potentiometer constructed in accordance with the present invention;

FIGURE 3 is a vertical sectional view taken along line 3-3 of FIGURE 1;

FIGURE 4 is a horizontal sectional view taken along line 44 of FIGURE 3;

FIGURE 5 is a horizontal sectional view taken along line 55 of FIGURE 3; and

FIGURE 6 is a vertical sectional view taken somewhat centrally through the structure of FIGURE 1.

A variable resistor or potentiometer constructed in accordance with the present invention may have a variety of geometric configurations, and may employ several different types of adjusting mechanisms; however, for purposes of clarity of illustration and ease of description, the present invention is described with respect to a lead screw actuated sliding contact potentiometer. The housing of the illustrative potentiometer is of generally parallelepiped configuration and is formed of an upper section which is afiixed by an integral hinge to a lower portion so as to fold into a closed position engaging the lead screw of the potentiometer so as to snap lock the structure in a closed assembled configuration in which the screw is rotatably supported.

Referring now to the drawing and more particularly to FIGURE 1 thereof, an illustrative potentiometer of the lead screw actuated type is shown to include a housing 10 containing a lead screw, the slotted adjustment head 12 of which extends out one end of the housing 10. Also extending from the housing 10 are downward contact terminals 14, 16 and 18 passing from the bottom. The terminals 14 and 18 provide connections to the ends of a resistance element while the terminal 16 provides a connection to a sliding contact which is variously positioned by the lead screw head 12.

The detailed structure of the housing 10 is considered below; however, it is to be noted that as shown in FIG- URE 2, the housing includes a body 20 connected to a cover 22 by a hinge 24-, all of which are one integral unit of a single substantially-homogeneous material having yieldably deformable characteristics. Specifically, for example, the material may comprise various plastics as injection-molded styrene. Furthermore in this regard, the housing 10 is formed to receive the internal mechanism in a rotatably supporting relationship, to accomplish the dual functions of preserving the unit closed and providing a reference for rotary motion.

Considering the internal mechanism of the illustrative embodiment in greater detail, reference will now be made to FIGURES 3, 4, 5 and 6 which are various sectional views taken through the structure of FIGURE 1. As shown in FIGURE 3, the lead screw head 12 is integral with a lead screw 26, the two elements being joined by a shaft 28 of reduced diameter which matingly receives annular extensions or ridges defined in the housing to provide bearing support as well as locked closure.

The lead screw 26 is journalled into the housing 10 and terminates in a journal section 30 (remote the head 12) which is also matingly received within the housing 10 for rotary motion. Thus, the entire lead screw structure is supported effectively for rotary motion to variously position an electrical contact element 32 having shaft-engagement ridges 34 extending upwardly to be received by the threaded section 36 of the lead screw. The contact element 32 includes a substantially flat plate 38 (FIG- URES 4 and 6) from which the contact fingers 40, 42 and 44 are stamped, and which further includes perpendicular upwardly extending sides 46 and 48 to slidingly contact the interior sides of the housing 10.

The contact fingers 40, 42 and 44 are in flexed engagement with a resistance element 50 (FIGURE 3) comprising a substrate body 52 (FIGURE 6) having a resistive element surface 54 and a collector surface 56 deposited thereon. The resistive element surface 54 is terminated by end sections 58 (FIGURE 5) of low resistance conductive medium. The substrate body 52 may comprise a block of ceramic material while the resistive element surface 50 may comprise variously formed resistive strips, for example a bonded metal composition finally deposited on the substrate element. The collector surface 56 and the end surfaces 58 may comprise a highly conductive metal composition deposited upon the substrate element.

The lead screw threaded section 36 (FIGURE 6) drives the contact element 32 to place the contact finger 44 at various positions on the resistive surface 54. Electrical contact is then established from the contact finger 44 through the contact element 50 to the parallel fingers 40 and 42 then through the conductive surface 56 (FIG- URE 5) to a lug 60 of the terminal 16 (FIGURE 6). Similar lugs 62 and 64 (FIGURE 5) electrically engage the end sections 58 for providing electrical contact to accomplish application of a potential along the surface 54. Thus, as the lead screw head 12 is turned, the threaded section 36 of the lead screw 26 is revolved to linearly displace the contact element 32 (FIGURE 3) providing a selected contact position of the contact finger 44 on the resistive surface 54 (FIGURE 5). As described, connection from the surface 54 to the collector surface 56 is provided by the bridging contact element 32 (FIGURE 4). From the collector surface 56, connection to the terminal 16 is provided through the terminal lug 60 (FIGURE 5). It is therefore apparent, that as the lead screw is variously adjusted, the contact element 32 is variously positioned to accomplish the conventional variable resistor or potentiometer function.

Returning now to a consideration of the housing 10 in greater detail the body 20 (FIGURE 2) along with the cover 22 and the hinge 24 may be molded or otherwise formed as a single unit with the hinge disposed along generally parallel adjacent surfaces of the housing body and cover. The interior of the body 20 includes a number of mounting recesses and shoulders for matingly engaging the internal mechanism. Specifically, a traverse central slot 76 is formed substantially at the center of the body 20, which slot extends across the bottom 72 and perpendicularly in the rear sidewall. The slot 76 recives the collector terminal 16 (FIGURE 6). Specifically the lugs 56 and the traverse section 74 are mated in the slot 76. Similar slots 70 are provided at each end of the housing across the bottom and opposite wall, to receive the terminals 62 and 64.

Inside the housing 10 (FIGURE 2) immediately above the slots 70 and 76, is a substantially rectangular space for holding the resistance element 50. Above that space the body 20 enlarges to provide guide surfaces on either side of the body for slidably receiving the side extensions 46 and 48 (FIGURE 6) of the contact element 32. At the ends of the surfaces 80 (FIGURE 2) semi-annular extensions 82 and 84 are formed to provide journal surfaces. That is, the extension 82 provides a bearing surface into which the journal 30 (FIGURE 3) of the lead screw is fitted While the extension 84 is lockingly received in the lead screw by engagement with the recess shaft 28.

Above the extensions 82 and 84, the body 20 again enlarges as defined by sidewalls 86 and 88 between which the cover 22 is matably received. Considering the cover 22, an elongate semi-cylindrical trough 90 extends from the hinge 24 substantially the full length of the cover 22, to receive the lead screw in journalled relationship so as to support the lead screw for rotary motion. The trough 90 is terminated at a semi-annular ridge 92 which is lockingly received in the lead screw at the shaft 28 in opposed relationship with the semiannular extension 84.

In the manufacture of the complete unit, as indicated above, the housing 10 may be molded or otherwise formed as a unitary body. The internal components may be variously formed individually employing techniques of the prior art. Specifically, the lugs 14, 16 and 18 may 'be stamped of metal or otherwise formed, along with the wiper element 32 which may be formed of berylium copper. The resistance elements 50 carrying the resistive surface and the collector surface may be formed in accordance with well-known techniques of ceramics and deposited metal surfaces. The lead screw may be molded of nylon and glass filled for extensive use with little wear.

In assembling the structure, the cont-act terminals 14, 16 and 18 are simply dropped into position within the housing 10 and a portion of the housing is heat formed to hold the pins in place. Thereafter, the resistive element 50 is placed in position and looked therein as by heat-formed locking mechanisms such as tabs 94 (FIG- URE 3) as well known in the prior art. Thereafter the contact element 32 is placed in position between the sides of the housing 10 in sliding engagement with the surfaces 80. The lead screw 26 is then set within the housing and the shaft 28 of the lead screw element is snapped into fastening engagement with the semi-annular extension 84 to seat the lead screw 26 within the body 20. The cover 22 is next folded over the internal mechanism and the annular ridge 92 is snapped into fastening mating engagement with the shaft 28. Finally, the upper edges 95, 96 of the side walls of the housing body are heat formed as shown in FIGURE 3 to effect final closure of the housing and to firmly hold the cover 22 in position for supporting the lead screw over its entire length. Thus, the assembly is completed without the use of any adhesives, auxiliary fasteners or closures to provide an effectively enclosed mechanism with simple operating characteristics capable of prolonged periods of maintenance free use.

An important feature of the present invention resides in the simplicity of assembly which may be accomplished with considerable economy and yet produce an effective variable resistor or potentiometer. There has thus been disclosed an exemplary potentiometer which is simple and inexpensive to manufacture and assemble and which is rugged in construction. Although the structure has been disclosed and described in some detail, such as is not intended as a limitation upon the scope of the present invention as defined in the appended claims:

What is claimed is:

1. A variable resistor comprising:

(A) a resistance element;

(B) at least one electrical contact;

(C) means for traversing said electrical contact over said resistance element; and

(D) a unitary integral housing of electrically non-conductive yieldably deformable material, including:

(1) a first section having a pair of parallel side wall portions and a pair of parallel end wall portions,

(2) a second section, matable with said first section to define a space for said resistance element, said electrical contact and said means for traversing,

(3) said housing further including a hinge section connecting said first section and said second section along generally parallel adjacent surfaces, said hinge forming a continuous surface of one of said wall portions and further forming a planar surface when said first and second sections are mated.

2. A variable resistor according to claim 1 in which said first section of said housing is the top thereof and defines a trough like depression extending along substantially the entire length thereof and said traversing means is a lead screw journalled in said housing and supported along the length of the threaded portion thereof by said trough like depression.

3. A variable resistor according to claim 2 wherein said means for traversing includes an electrically non-conduc tive threaded lead screw of molded plastic material ex tending substantially perpendicular to said parallel surfaces of said first and second housing sections to which said hinge is connected.

4. A variable resistor according to claim 2 wherein said lead screw further includes first fastening means and said first and second sections of said housing include second and third fastening means for engagement with said first fastening means to lock said housing closed.

5. A variable resistor according to claim 2 wherein said housing comprises injection molded plastic material and wherein the upper edges of said second section are heat formed to engage said first section for closing said housing.

6. A variable resistor according to claim 4 wherein said lead screw includes journal means adjacent each end thereof and wherein said housing defines bearing means adjacent each end thereof for matingly receiving said journal means, said journal means at one end of said lead screw including said first fastening means and said bearing means at one end of said housing including said second and third fastening means.

References Cited UNITED STATES PATENTS 2,935,715 5/1960 Bourns et al. 338

2,954,537 9/1960 Scott et al. 338180 X 3,106,602 10/1963 Hartz 174-66 X FOREIGN PATENTS 1,121,451 8/1956 France.

ROBERT K. SCHAEFER, Primary Examiner.

H. HOHAUSER, Assistant Examiner.

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