US3284752A - Duplex variable electrical resistance device - Google Patents

Description

Nov. 8, 1966 o. BELLAR 3,284,752

DUPLEX VARIABLE ELECTRICAL RESISTANCE DEVICE Filed Oct. 24, 1965 2 Sheets-Sheet 1 JA/VEA/T'OP.

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Nov. 8, 1966 o. BELLAR DUPLEX VARIABLE ELECTRICAL RESISTANCE DEVICE Filed Oct. 24, 1965 2 Sheets-Sheet 2 United States Patent 3,284,752 DUPLEX VARIABLE ELECTRICAL RESISTANCE DEVICE Oscar Bellar, Alhambra, Calif., assignor to Terence Dalhy, Alhambra, Calif. Filed Oct. 24, 1965, Ser. No. 504,862 9 Claims. (Cl. 338-131) This invention relates to variable electrical resistance devices and more particularly to an improved form thereof operating on the principle of my copending application Serial No. 504,901, filed October 24, 1965.

The principal object of the invention is: to provide a duplex variable resistance device of the above character in which two separate resistance adjusting means are mounted for movement on a common base and are associated with separate conductor means comprising two resistance assemblies, also mounted on said common base, which assemblies may be connected in electrical circuits in different manners, e.g., to serve 'as two completely sepa rate variable resistance devices, in which one of said two devices may be interconnected to modify the output of the other of said devices, in which, for example, one of the devices may be used as a potentiometer device while the other may be used as a rheostat and/or in this latter combination, so that one of the devices may modify the output of the other device.

Another object of the invention is to provide a device of the above character which is capable of being made in miniature form or size for use with very small cur-rent potentials.

Still another object of the invention is to provide a device of the above character which is small in size, composed of parts which are few in number and simple in de- Sign, and which is effective for its intended purposes.

With the foregoing objects in view, together with such additional. objects and advantages as may subsequently appear, the invention resides in the parts and in the con st-ruetion, combination and arrangement of parts described, by w-ay of example, in the following specification of a presently preferred embodiment of the invention, reference being had to the accompanying drawings which form a part of said specification and in which drawings:

FIG. 1 is a side elevational view of a variable resistance device constituting a presently preferred embodiment of the invention,

'FIGS. 2 and 3 are, respectively, top plan and bottom plane views of the device shown in FIG. 1,

FIG. 4 is a transverse medial sectional view taken on the staggered line 44 of FIGS. 2 and 3,

FIG. 5 is a fragmentary bottom plan view of a portion of the device indicated by the arrowed line 55 of FIG. 4,

FIG. 6 is a transverse sectional plan view taken on the line 6-6 of FIG. 4,

FIG. 7 is a fragmentary sectional view taken on the line 77 of FIG. 6,

FIG. 8 is a perspective view of the internal brush component of the device,

FIG. 9 is a perspective view of one of the plurality of external brush components of the device, a portion of the actuating means therefor being included in the figure,

FIG. 10 is a circuit diagram of the fundamental circuitry of the device, and

FIG. 11 is a schematic view illustrating the arrangement of the wires or conductors of the inner and outer resistance assemblies of the device.

Referring to the drawings, the illustrated embodiment of the invention comprises a circular, thick, disc-like nonconductive base 1 having a first series of three terminals 2a, 2b and 20 extending therethrough parallel to the axial line of the base and disposed at equal radial distances 3,284,752 Patented Nov. 8, 1966 from said line and at equal distances from each other, and with a second series of terminals 3a, 3b and 3c arranged oppositely with respect to said first series of terminals but at lesser radial distances from the center of the base whereby (see FIG. 3) terminal 3a is diametrically opposite terminal 2a, etc. Exteriorly of said base, said terminals are shown as forming socket engaging pins but it will be appreciated that any mode of electrical connection may be substituted therefor.

The outer periphery of the base 1 is provided with a peripheral groove 4 in which a snap ring 5 is disposed; said ring normally extending outwardly of said groove and engaging a complementary groove 6 in the inner peripheral surface 7 of a cylindrical body member 8 which closely but freely rotatably fits the periphery of the base 1. An opening 5 from the under side of the base 1 affords access to the ends of the spring 5 for a suitable tool for collapsing the spring incident to installation or removal of the body member 8 therefrom, said ring serving to hold the body and base in assembly.

In the description of the illustrated embodiment of the invention and of the various component parts thereof the relationship thereof will be referred to as being above," below, etc. Since the device may be used in any particular position or attitude, it will be understood that such designation of relationship between parts is merely one of convenience having reference to the illustration thereof. Also, the wire components constituting the resistance assemblies of the device and of the brush components thereof are frequently of only a few thousandths of an inch in diameter wherefore, it will be understood that the showing thereof in the drawings is to be regarded as schematic in view of the fact that to show such elements in their true proportion to the rest of the device would cause the rest of the device to be shown in such a large scale as to be thoroughly impractical and, in any event, to add nothing to an understanding of the invention. In its smaller sizes, the embodiment shown in FIG. 1 for example, would seldom, if ever, exceed about /2 in diameter.

The body 8 extends above the upper face of the base 1 and the exterior surface thereof is preferably provided with a suitable surface for manual gripping such as the flutes 9 formed thereon. Alternatively, of course, a series of ribs might be employed or any other configuration that would be susceptible of economical-manufacture and provide a good surface for manual gripping without slippage. The said internal surface 7 of the body extends in parallel relation to the side or peripheral surface of the base 1 for the length of that peripheral surface and thence continues above the upper surface of the base 1 to combine with the upper surface of the base 1 to form a cavity portion 10 in which the variable resistance components, per se, are contained. From the top surface of the base 1 to the upper end of the cavity 10, the said internal surface 7 is interrupted by pairs of vertically extending rib members 11, 11 which combine to serve as the guiding and actuating means for a pair of external brush components 12, 12 to which further reference will hereinafter be made.

Mounted on the base 1 within the cavity 10 is the cylindrical resistance assembly support member 13 comprising a hollow cylindrical member of non-conductive ma terial having a reduced diameter rib portion 14 at one end thereof which engages a groove 15 in the upper surface of the base and in which groove it is secured by adhesive or any other suitable means. The outer diameter of the member 13 is preferably not greater than twice the radius of the distance from the center line of the disc 1 to the inner or adjacent sides of the outer terminals 2a, 2b and 2c and the inner diameter of the member 13 is preferably not less than twice the radius from the center line of the body 1 to the outermost face of the inner row of terminals 3a, 3b and 3c. The length of the member 13 may be any length that will accommodate the length of the resistance assemblies carried thereby as will presently appear.

The external surface of the member 13 carries the outer resistance assembly 16 comprising three wires leading one each from each of the terminals 2a, 2b and 2c laid side by side and in that side-by-side relation wound in a helix on the outer surface of the member 13 and secured thereon by any suitable means such as, for example, by suitable adhesive, the said wires having a non-conductive coating so as not to be electrically interconnected except by the brush means to be presently described.

Similarly, the internal resistance assembly 17 comprises a series of three wires leading from the terminals 3a, 3b and 3c laid side by side and wound similarly in a helix on the inner surface of the body 13 and adhered thereto by suitable adhesive. In actual practice, these wires would first be wound on a collapsible mandrel of appropriate diameter so that the resulting winding would fit closely on the inner diameter of the member 13, the resulting winding would be inserted on the inner surface of the member 13 with suitable adhesive and after the adhesive had set, the mandrel would be collapsed and removed from the winding thus adhered to the inner surface of the member 13. As with the wires comprising the outer resistance assembly 16, these wires would also 'be coated with nonconductive material so that they could be electrically interconnected only by brush means including the brush element or component 18 presently to be described in detail.

Beyond the upper end of the member 13, the body 8 is provided with an end wall 19 having a depending annular flange engaging the upper interior diameter of the resistance assembly supporting body 13, said engagement constituting a bearing means in addition to the bearing engagement with the body 1 having an axially disposed opening 20 extending therethrough in which the shank 21 of an operating knob 22 for the inner brush component 18 is mounted for free rotation, said knob being restrained against endwise movement in said axial opening 20 by a gasket 23 between the knob '22 and the outerupper surface of the end wall 19 and by a snap ring 24 engaging a peripheral groove 25 in the shank 21 at the inner side of the end wall 19. The shank 21 of the hand knob 22 carries a depending non-circular shank 26 which engages a complementary hole 27 in a sheet metal retainer 28 for the contact element 29 of the internal brush component 18 whereby rotation of the shank 26 by the knob 22 and consequent rotation of the brush component 18 will allow the brush component to move longitudinally of the shank in a manner and for a purpose presently to be described.

Each of the external brush assemblies 12 comprises an elongated base member 30 generally conforming to the curved surface 7 of the body 8 and extending between the opposed faces of one of the pairs of ribs 11, 11. At each end thereof, it is provided with a radially inwardly extending portion 31 and mounted on the members 31, 31 and secured thereby by caps 31', 31' adhered thereto and to the member 30 are small metal blocks 32, 32 which are united with the respective opposite ends of the series of spring wires 33 which, in effect, extend as the center portion of the chord of an are represented by the curvature of the member 30 and which wires, in a line radially of the axial line of the resistance assembly 16, normally are disposed at a lesser distance than said radial dimension wherefore, when brought into contact with the exterior of the outer resistance assembly, they are slightly outwardly bowed to produce a light but definite and continuous yielding engagement with the wires of the outer resistance assembly 16 as best indicated in FIG. 6. The wires 33 are uninsulated wires and the outer surfaces of the wires constituting the outer resistance assembly 16 have had the coating thereof removed so that the contact with the wires 33 will be an electrically conductive contact. Moreover, the wires 33 are preferably of approxiguiding ways formed by adjacent pairs of the ribs 11, 11. l

The contact element 29 of the internal brush assembly 18 comprises a helical spring which, as best shown in FIGS. 6 and 8 is deformed by inwardly curving the spring at three portions thereof as indicated at 34 leaving contact surfaces or portions 35 which normally are of slightly greater radial dimension than the least radial dimension of the internal resistance assembly 17. The supporting and driving member 28 comprises a sheet of metal having three laterally extending arm portions 36 which extend from beneath the member 29 loosely eX- teriorly of the inwardly curved portions 34 and thence overlap said portions with inturned lips 37. Thus, the radial inward compression of the contact portions 35 upon engagement with the inner resistance assembly 17 will be accommodated by slight inward bowing of the portions 34, the resilience of which assures continuous yielding contact with the internal surface of the internal resistance assembly 17. The wires 33 are preferably of approximately the same diameter wires as constitute the resistance assembly with which they are in contact so that they will engage the grooves formed by adjacent wires with the result that rotation of the brush element will cause it to engage the said grooves as though said grooves constituted a helical thread and to be moved axially of said resistance assembly in the direction and to the extent determined by the rotation of the brush element.

As previously mentioned, this device is capable of a wide variety of uses. Assuming for example, that the wires of the outer resistance assembly associated with terminals 2a and 212' are connected in a series circuit, the movement of the brush element 12 across the resistance assembly will vary the resistance dependent on the number of turns of the resistance assembly between the brush component and the terminal. Thus far assuming that the terminal 2c is not connected in any circuit, the outer resistance assembly and brush will act as a simple rheostat.

Next assuming that the terminal 2c and the wire of the resistance assembly associated therewith is connected to some other portion of a circuit, the outer resistance assembly and its associated brush means as adjusted by rotation of the body 8 operates as a potentiometer varying the current supplied to terminal 2c.

What has been said with respect to two possible uses of the outer resistance assembly is equally true of the inner resistance assembly and its adjustable brush component 18. Any two of the three wires may serve as a simple rheostat device while with the third wire connected to another portion of an electrical circuit the device operates as a separate potentiometer.

The device is not limited to be used as two separate rheostats or two separate Potentiometers. For example, assuming that terminal 20 is connected to terminal 3a, the wires of the internal resistance assembly 3a and 3b can act as a rheostat further varying the output of the potentiometer formed by the outer resistance assembly and its brush or the inner resistance assembly and the brush associated therewith can be used as a second potenticmeter in cascade or series relation to a potentiometer formed by the outer resistance assembly and its brush.

It will be appreciated that these various uses do not involve any change in structure of the device and while certain possible uses of which the device is thus capable without change, have been thus described it is not to be inferred therefrom that such are the only uses. Moreover, while the resistance elements illustrated comprise three wires laid side by side and wound helically in that condition, it is not to be inferred therefrom that such windings are necessarily limited to the precise number and that either or both resistance assemblies may comprise any number of wires greater than one and that the windings do not have to be each of the same number nor do they have to be wound in the same direction. Moreover, while the contact portions of the brush components are here shown as comprising parallel wires yieldingly engaging the grooves between adjacent ones of the convolutions comprising the resistance assemblies, the brush components need not be limited to being formed from parallel wires and may be any metal contact means that will effect the electrical shorting between adjacent convolutions which is essential to the operation of the device. The choice of wires for this particular use is primarily one of convenience. With the foregoing observations in mind, it will be appreciated that the invention is not to be deemed to be limited to the precise details of construction and usage thus disclosed by way of example and that the invention includes as well all such changes and modifications in the parts and in the construction, combination and arrangement of parts as shall come within the purview of the appended claims.

I claim:

1. In a duplex, variable electrical resistance device, a base including a resistance assembly support, first and second resistance assemblies carried by said support each comprising a plurality of elongated electrical conductors arranged in side by side relation and electrically insulated from each other throughout their lengths, and a pair of separate, manually operable means carried by said base, one of said manually operable means being associated with said first resistance assembly and the other with aid second resistance assembly, each of said manually operable means including a resilient brush component electrically interconnecting the conductors of the one of said assemblies with which it is associated at infinitely variable points in the length thereof, one of said manually operable means additionally serving as the support for the other of said manually operable means, means interconnecting said manually operable means effective to permitt movement of either of said manually operable means to effect variation of the associated resistance assembly while maintaining the then existing position of the other of said manually operable means with respect to the resistance assembly with which said other manually operable means is associated, and a plurality of terminals disposed on an exterior surface of said base connected one each to each of said conductors and affording separate connection of the conductors comprising said resistance assemblies into an electrical system, one of said manually operable means serving in cooperation with said base to enclose said support and the resistance assemblies carried by said support.

2. A duplex, variable electrical resistance device as claimed in claim 1 in which said resistance assembly support comprises a hollow cylindrical suppont, said support being mounted on said base and having one of said resistance assemblies mounted on the external cylindrical surface thereof and the other of said resistance assemblies mounted on the internal cylindrical surface thereof.

3. A duplex, variable electrical resistance device as claimed in claim 2 in which the one of said manually operable means associated with the one of said resistance assemblies which is mounted on the exterior of said support serves additionally in cooperation with said base to enclose said support and the resistance assemblies carried thereby.

4. A duplex, variable electrical resistance device as claimed in claim 1 in which each of said resistance assemblies comprises a helix, and in which the associated manually operable means includes a brush component rotatable about the axis of generation of the helix and which is movable as an incident to said rotation in a direction parallel to said axis.

5. A duplex, variable electrical resistance device as claimed in claim 2 in which said resistance assembly disposed on the inner cylindrical support serves additionally as the supporting means for the brush component which is in electrically conductive engagement therewith, in which said brush component is operatively connected to the one of said manually operable means which is supported by the other of said manually operable means, and in which devices operated by the manually operable means which is supported by the other manually operable means are connected to and effect movement of said brush component relative to the said resistance assembly on the inner surface of said support.

6. A duplex, variable electrical resistance device as claimed in claim 2 in which the one of said manually operable means associated with the resistance assembly mounted on the outer surface of said support is mounted for rotation on said base and includes a component which cooperates with said base to form a housing for said support and the resistance assemblies carried thereby and which, additionally, is operatively connected to the brush component which is supported by and electrically interconnects the conductors constituting said resistance assembly disposed on the outer surface of said cylindrical support while permitting movement of said brush component in directions parallel to the axis of said rotative movement.

7. A duplex, variable electrical resistance device as claimed in claim 3 in which the one of said manually operable means associated with the one of said resistance assemblies mounted on the inner cylindrical surface of said support is mounted for free rotation on the manually operable means associated with the resistance assembly mounted on the external cylindrical surface of said support and which manually operable means cooperates with said base to enclose the cylindrical support and the resistance assemblies carried thereby.

8. A duplex, variable electrical resistance device as claimed in claim 3 in which the manually operable means associated with the resistance assembly mounted on the outer surface of said support is detachably mounted for free rotation on said base to afford access to the interior of said device.

9. A duplex, variable electrical resistance device as claimed in claim 3 in which said manually operable means which encloses said support and resistance assemblies is provided with bearing engagement on the periphery of said base and on said support at a point axially remote from said base.

References Cited by the Examiner UNITED STATES PATENTS 1,490,334 4/1924 Lindberg 338126 2,065,805 12/1936 Harrison 338126 X 2,122,370 6/1938 Harrison et al 338126 2,277,883 3/1942 Rich 338-131 X 2,548,591 4/1951 Crowley 338126 2,724,034 11/1955 Altieri 338126 FOREIGN PATENTS 658,067 3/ 1938 Germany.

ANTHONY BARTIS, Primary Examiner.

Claims (1)

1. IN A DUPLEX, VARIABLE ELECTRICAL RESISTANCE DEVICE, A BASE INCLUDING A RESISTANCE ASSEMBLY SUPPORT, FIRST AND SECOND RESISTANCE ASSEMBLIES CARRIED BY SAID SUPPORT EACH COMPRISING A PLURALITY OF ELONGATED ELECTRICAL CONDUCTORS ARRANGED IN SIDE BY SIDE RELATION AND ELECTRICALLY INSULATED FROM EACH OTHER THROUGHOUT THEIR LENGTHS, AND A PAIR OF SEPARATE, MANUALLY OPERABLE MEANS CARRIED BY SAID BASE, ONE OF SAID MANUALLY OPERABLE MEANS BEING ASSOCIATED WITH SAID FIRST RESISTANCE ASSEMBLY AND THE OTHER WITH SAID SECOND RESISTANCE ASSEMBLY, EACH OF SAID MANUALLY OPERABLE MEANS INCLUDING A RESILIENT BRUSH COMPONENT ELECTRICALLY INTERCONNECTING THE CONDUCTORS OF THE ONE OF SAID ASSEMBLIES WITH WHICH IT IS ASSOCIATED AT INFINITELY VARIABLE POINTS IN THE LENGTH THEREOF,ONE OF SAID MANUALLY OPERABLE MEANS ADDITIONALLY SERVING AS THE SUPPORT FOR THE OTHER OF SAID MANUALLY OPERABLE MEANS, MEANS INTERCONNECTING SAID MANUALLY OPERABLE MEANS EFFECTIVE TO PER-

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