US3111640A

US3111640A - Variable resistance device

Info

Publication number: US3111640A
Application number: US202840A
Authority: US
Inventors: Edward W Dial
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-06-15
Filing date: 1962-06-15
Publication date: 1963-11-19
Anticipated expiration: 1980-11-19

Description

Nov. 19, 1963 E. W. DIAL VARIABLE RESISTANCE DEVICE Filed June 15, 1962 INVENTOR jdmrd l fl'dl BY WW ATTORNEYS United States Patent Ofi ice 3,111,649 Patented Nov. 19, 1963 3,111, 40 VAREAEBLE REHSTANCE DEVICE Edward W. Dial, 815 Bnclrroe Ave, Hampton, Va. Filed lune 15, 1962, Ser. No. 202,840 3 Claims. (Cl. 338-160) The present invention relates in general to variable resistance devices such as potentiometers, rheostats, volume controls and the like, and more particularly to variable resistance devices of the potentiometer type wherein the resistance element is readily removable to facilitate repair or replacement thereof.

l-leretofore, conventional variable resistance devices such, for example, as a volume control potentiometer have been conventionally constructed in such a way that the resistance element cannot be removed from the encasing cover without substantial destruction of the device. Consequently, when such a potentiometer control element becomes defective, it is usually necessary to unsolder the three conductor connections to the terminals, physically remove the entire control device, install a new, complete control device and resolder the three connections to the terminals. This procedure not only entails a lengthy work process and its attendant possibilities for mechanical error, but also involves considerable cost compared with repair procedures wherein only a portion of the control device would be replaced. By far the greatest majority of defects in potentiometer control devices requiring replacement of a control are caused by a defect appearing in the resistance element.

An object of the present invention, therefore, is the provision of a novel variable resistance control device wherein the resistance element is a separable component which can be readily removed and replaced with a minimum of time and efiort by unskilled personnel.

Another object of the present invention is the provision of a novel variable resistance control device of simplified construction wherein a resistance bearing member of substantially rectangular platform or panel type configuration is removably supported Within the cover in a manner facilitating simple removal of the resistance bearing panel and replacement thereof.

Other objects, advantages, and capabilities of the present invention will become apparent from the following detail description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.

In the drawing:

FEGURE l is a perspective view of a variable resistance potentiometer constructed in accordance with the present invention; I

FIGURE 2 is an exploded perspective view thereof with the components inverted relative to the position they assume in FIGURE 1;

FlGURE 3 is a vertical longitudinal section view taken along the line 33 of FlGURE l; and

FIGURE 4 is a vertical transverse section view taken along the line 4 4 of FIGURE 3.

Referring to the drawing, wherein like reference characters designate corresponding parts throughout the several figures, an exemplary form of a variable resistance potentiometer constructed in accordance with the present invention is indicated generally by the reference character ll) and comprises a casing 11 formed of a front wall member 12 and a cover 13 secured thereto. The front wall member E2 is here shown as a rigid, rectangular plate having parallel lateral edges 14, 15 and upper and lower edges l6, 11.7 at least the lateral edges l4, l and one of the edges 16, 17 having rectangular notches l3 spaced along the same. The cover 13 is a rectangular, box-like member having a rear Wall panel l9, and

lateral side walls

20, 21 and top and

bottom walls

22, 23 projecting forwardly from the rear panel 19 in perpendicular relation thereto. Ihe lateral side walls 2d, 21 and the bottom Wall 23 in the embodiment herein illustrated having integral locking tabs 24 projecting from the forward edges thereof to seat in the notches l8 and be bent about the front surface of the front wall member 12 to fix the cover 13 thereon. The cover 13 may be formed of sheet metal by cutting and bending a blank thereof or in any other desired manner.

An elongated operating shaft 25 extends through an aperture in the front wall member 12 and is journaled for rotation therein by a suitable bearing or the like, such for example as an externally threaded bearing tube 26 through which the shaft 25 extends which is connected to or integrally formed with the front wall member 12, the shaft 25 having an external end portion upon which a suitable operating knob may be provided and an inner end portion 27 adapted to lie Within the chamber 28 formed by the casing 11 having a key 29 on the end thereof. A wiper member 36 in the form of a circular disc, for example of insulating material, has a non-circular aperture 31 to fit over the shaft key 29 and produce rotation of the wiper member 3%} with the shaft 25 and a peripheral contact ring 32 of conductive material having a contact projection 32a at a selected point thereon projecting rearwardly of the plane of the ring 32. The ring 32 is continuously engaged by the center terminal 34 of three terminal members 33, 34 and 35 electrically insulated from and mounted on the front wall member 12 adjacent the top edge 16 thereof and projecting externally of the casing 11. The wiper member 3% may also include a stop tab 35 which projects radially from the periphery thereof to engage a fixed stop stud or pin 37 on the front wall member 12 projecting into the path of the stop tab 36 to limit rotation of the wiper.

The lateral side walls 2" 21 of the cover 13 are provided with inwardly opening, parallel and transversely aligned groove or channel-shaped formations 38 in this example, formed by inwardly bent elongated beads 39 or rib-forming indentations in the

side walls

20, 21, defining rectilinear slideways within the casing 11 aligned with a laterally elongated access opening 49 in the bottom wall 23 immediately adjacent the rear wall panel 19 to receive a resistance insert 41. The resistance insert 41 is in the form of a rigid card or panel 42 of rectangular configuration formed for example of insulating material, having parallel lateral edges 43 spaced apart substantially in conformity to the lateral internal dimensions of the casing ll to be received in and guided by the channelshaped formations 33. The panel 42 carries an electrical resistance element 44 of suitable resistance material thereon which follows a substantially arcuate path concentric with a point on the panel to be aligned with the axis of the shaft 25 when the insert 41 is fully seated in the chamber 28 of the casing 11, and having portions which extend into electrical contact with the terminal members 33, 35 in bridging relation to the latter. In the embodiment illustrated, the resistance element 44 assumes the general configuration of the Greek letter omega with the feet adjoining the arc of the letter forming extensions to contact the terminal members 33, 35. A slot 45 opens through the top edge of the panel 42 to accommodate the end portion of the key 29 on the shaft 25 projecting rearwardly of the wiper member during sliding movement of the panel 42 relative to the casing, the slot 45 having a circular enlargement at :me center of the arcuate portion of the resistance element when the resistance insert is fully inserted into the casing.

The top wall 22 of the cover 13 forms a limit stop for the top edge of the insert 41, and the rear wall 1% of the cover 13 has one ormorebendable tabs 46 at the edge thereof boundingthe access opening 4 9 to be bent perpendicular to the plane of the rear wall 19 across the access opening 40 when the resistance insert 41 is seated in the casing 11 and retain the insert 41 therein. An arcuate recess as indicated at 4-7 may be provided in the lower edge portion of the rear cover wall 19 between the tabs 46 to facilitate insertion and withdrawal of the resistance insert relative to the slideway therefor.

In the operation of the device, the wiper member 3i is assembled on the key end of the shaft 25 in the usual manner, and the cover 13 is assembled on the front wall member 12 by fitting the same on the front wall member with the locking tabs 24 seated in the rectangular notches 13 and then bending the locking tabs 2d inwardly to lap the front surface of the front wali member. The resistance insert 41 is then introduced into the chamber 28 of the casing 11 by insertion through the access opening 49 and sliding the same upwardly along the slideway provided by the channel formations 38 in the

side walls

19, 21 of the cover, as the top edge of the panel 42 abuts the top 22 of the cover. Thereafter, the tabs 46 are bent for- Wardiy across the access opening ii) against the bottom edge of the panel 42 of the resistance insert 41. When the resistance insert is fully inserted into the casing, the extensions or feet of the resistance element 44- achieve a condition of physical and electrical contact with the terminal members 33, 35 in series relation between these terminal members, and the contact projection 32a of the contact ring 32 on the wiper member 3% is in contact with the arcuate portion of the resistance element 44. When it becomes desirable to remove the resistance element for repair or replacement, this can be readily accomplished by bending the tabs 46 downwardly into substantially co-planar relation with the rear wall 19 of the cover 13, and sliding the panel 42 on which the resistance element 4-4 is carried out of the slideway provided by the panel formations 38, and a new resistance insert may then be inserted and the tabs 46 bent forwardly again to support the same within the cover.

While but one preferred example of the present invention has been particularly shown and described, it is apparent that various modifications may be made therein within the spirit and scope of the invention, and it is desired, therefore, that only such limitations be placed on the invention as are imposed by the prior art and set forth in the appended claims.

What is claimed is: i

l. A variable resistance potentiometer or the like comprising a casing having front and rear walls, lateral side walls and top and bottom walls defining an enclosed chamber therebetween, an operating shaft journaled in said front wall for rotation about its axis having an inner end portion disposed within said chamber, a wiper member supported on said inner end portion of said shaft for rotation therewith having an electrical contact portion projecting rearwardly therefrom eccentrically disposed relative to the axis of said shaft, said casing side walls including means defining a pair of laterally spaced parallel guide channels providing a slideway along a plane perpendicular to the axis of said shaft adjacent the inner end thereof, a resistance insert disposed within the chamber of said casing movable relative to said shaft and wiper member for sliding insertion and withdrawal from the casing independently of said shaft and wiper member along a plane paralleling said front wall, said insert having a support panel of substantially rectangular configuration providing parallel spaced lateral edges slidably supported in said guide channels and an electrical resistance element carried on said panel along an arcuate path concentric with the axis of said shaft to be engaged by said contact projection on said wiper member, said guide channels being located to dispose said resistance element in sliding electrical and physical contact with said Wiper member when said panel occupies a selected position along said plane, stop means providing an abutment for engaging an edge of said'pa'nel are selected location along said plane to :locate said resistance element in selected alignment with said Wiper member and the axis of said shaft, said casing having an access opening therein conforming substantially to the cross sectional configuration of said resistance insert panel and aligned with said slideway for accommodating passage of said resistance insert therethrough, and said casing including bendable tab means extending from a portion of the casing bounding said access opening and bendable across portions of said access opening to intercept withdrawal movement of said panel along said slideway and hold said panel in position within said casing.

2. A potentiometer or the like comprising a casing including a rigid front wall member of generally rectangular, planar configuration having parallel lateral edges, a cover mounted on said front wall member of generally box-like configuration having a rear wall disposed paraliel to and spaced rearwardly from said front wall member and integral top, bottom and side walls projecting forwardly from said rear wall and secured at their front edges to said front wall member defining an enclosed chamber therebetween, an operating shaft journaled in said front wall member for rotation about an axis perpendicular to said front wall member having an inner end portion lying within said chamber, a wiper contact member coupled to the inner end portion of said shaft for rotation therewith, a generally rectangular removable resistance-bearing panel forming a resistance insert in said chamber movable relative to said shaft and wiper contact member for insertion and withdrawal movement from the cover independently of the shaft and wiper member along a plane paralleling said front wall member and intercepting the inner end portion of said shaft, said panel having parallel rectilinear lateral edges and a resistance element fixed on the surface of said panel facing said front wall extending along an arcuate path substantially concentric with the axis of said shaft, means on said lateral side walls of said cover defining rectilinear parallel guide channels opening inwardly of the chamber to slidably receive said lateral edges of said resistance insert panel in said plane and supoprt said panel in parallelism with said front wall member, said casing including stop means providing an abutment for engaging an edge of said panel transverse to said lateral edges to locate said panel in selected alignment with the axis of said shaft, said panel having an opening therein accommodating rotation of the inner end portion of said shaft therein when said panel occupies the selected alignment location and opening through the last-mentioned edge of said panel to permit passage of the shaft therethrough upon insertion and withdrawal movement of said panel along said plane, one of said top and bottom walls of said cover having an access opening therein aligned with the plane of said resistance-bearing panel and conforming substantially to the cross section thereof to accommodate insertion and removal of said resistance-bearing panel therethrough, and bendable tab members extending integrally from a portion of said cover bounding said access opening across said access opening to close the same against withdrawal of said panel from said chamber.

3. The combination recited in claim 2 wherein said resistance element has an omega configuration providing an arcuate portion to be engaged by said wiper contact member and extension portions to be connected in electrical communication with an external circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,841,660 Tabet July 1, 1958 2,871,324 Budd Jan. 27, 1959 2,917,721 Kelver et al. Dec. 15, 1959 3,015,000 Tabet Dec. 26, 1961 3,069,598 Bailey et al. Dec. 18, 1962

Claims

1. A VARIABLE RESISTANCE POTENTIOMETER OR THE LIKE COMPRISING A CASING HAVING FRONT AND REAR WALLS, LATERAL SIDE WALLS AND TOP AND BOTTOM WALLS DEFINING AN ENCLOSED CHAMBER THEREBETWEEN, AN OPERATING SHAFT JOURNALLED IN SAID FRONT WALL FOR ROTATION ABOUT ITS AXIS HAVING AN INNER END PORTION DISPOSED WITHIN SAID CHAMBER, A WIPER MEMBER SUPPORTED ON SAID INNER END PORTION OF SAID SHAFT FOR ROTATION THEREWITH HAVING AN ELECTRICAL CONTACT PORTION PROJECTING REARWARDLY THEREFROM ECCENTRICALLY DISPOSED RELATIVE TO THE AXIS OF SAID SHAFT, SAID CASING SIDE WALLS INCLUDING MEANS DEFINING A PAIR OF LATERALLY SPACED PARALLEL GUIDE CHANNELS PROVIDING A SLIDEWAY ALONG A PLANE PERPENDICULAR TO THE AXIS OF SAID SHAFT ADJACENT THE INNER END THEREOF, A RESISTANCE INSERT DISPOSED WITHIN THE CHAMBER OF SAID CASING MOVABLE RELATIVE TO SAID SHAFT AND WIPER MEMBER FOR SLIDING INSERTION AND WITHDRAWAL FROM THE CASING INDEPENDENTLY OF SAID SHAFT AND WIPER MEMBER ALONG A PLANE PARALLELING SAID FRONT WALL, SAID INSERT HAVING A SUPPORT PANEL OF SUBSTANTIALLY RECTANGULAR CONFIGURATION PROVIDING PARALLEL SPACED LATERAL EDGES SLIDABLY SUPPORTED IN SAID GUIDE CHANNELS AND AN ELECTRICAL RESISTANCE ELEMENT CARRIED ON SAID PANEL ALONG AN ARCUATE PATH CONCENTRIC WITH THE AXIS OF SAID SHAFT TO BE ENGAGED BY SAID CONTACT PROJECTION ON SAID WIPER MEMBER, SAID GUIDE CHANNELS BEING LOCATED TO DISPOSE SAID RESISTANCE ELEMENT IN SLIDING ELECTRICAL AND PHYSICAL CONTACT WITH SAID WIPER MEMBER WHEN SAID PANEL OCCUPIES A SELECTED POSITION ALONG SAID PLANE, STOP MEANS PROVIDING AN ABUTMENT FOR ENGAGING AN EDGE OF SAID PANEL AT A SELECTED LOCATION ALONG SAID PLANE TO LOCATE SAID RESISTANCE ELEMENT IN SELECTED ALIGNMENT WITH SAID WIPER MEMBER AND THE AXIS OF SAID SHAFT, SAID CASING HAVING AN ACCESS OPENING THEREIN CONFORMING SUBSTANTIALLY TO THE CROSS SECTIONAL CONFIGURATION OF SAID RESISTANCE INSERT PANEL AND ALIGNED WITH SAID SLIDEWAY FOR ACCOMMODATING PASSAGE OF SAID RESISTANCE INSERT THERETHROUGH, AND SAID CASING INCLUDING BENDABLE TAB MEANS EXTENDING FROM A PORTION OF THE CASING BOUNDING SAID ACCESS OPENING AND BENDABLE ACROSS PORTIONS OF SAID ACCESS OPENING TO INTERCEPT WITHDRAWAL MOVEMENT OF SAID PANEL ALONG SAID SLIDEWAY AND HOLD SAID PANEL IN POSITION WITHIN SAID CASING.