US3193786A

US3193786A - Potentiometer

Info

Publication number: US3193786A
Application number: US282032A
Authority: US
Inventors: Sr Fred J Moore; Southwell Geofrey
Original assignee: International Resistance Co
Current assignee: International Resistance Co
Priority date: 1963-05-21
Filing date: 1963-05-21
Publication date: 1965-07-06
Anticipated expiration: 1982-07-06
Also published as: GB1058728A; DE1465720A1; DK111384B

Description

y 6, 1965 F. J. MOORE, sR., ETAL 3,193,786

POTENTIOMETER Filed y 21, 5 2 Sheets-Sheet 1 56Z B 52 INVENTORS FRED J. MOORE, 67?. Y GEOFFREY SOUTHWEZL ATTORNEY y 6, 1955 F. J. MOORE, sR., ETAL 3,193,786

POTENTIOMETER Filed y 21, 1963 2 Sheets-Sheet 2 INVENTORS /06 F950 .1. MOORE. 5R.

7 BY GEOFFREY SOUTHWELL //4 /09 52 Mw United States Patent 3,193,786 POTENTIQMETER Fred J. Moore, Sr., Largo, and Geoffrey Southwell, St. Petershurg, Fla., assignors to International Resistance Company, Philadelphia, Pa.

Filed May 21, 1963, Ser. No. 282,032 6 Claims. (Cl. 338-464) The present invention relates to a potentiometer, and more particularly to a miniature trimmer potentiometer.

A trimmer potentiometer is a variable resist-or the resistance value of which is not constantly changed, but which is set and maintained at :a desired resistance value until adjustment of the circuit is required. With the trend in the electronic industry toward miniaturization, it is desirable to have very small and compact trimmer potentiometers. Also, because of the use of such trimmer potentiometers in electronic circuits, it is desirable to be able to stack mount a plurality of the potentiometers in side-byside' and/or end-to-end relation with all of the 3,193,785 Patented July 6, 1965 walls of the base. Base 12 is provided with a cylindrical recess in its top surface, which recess has a cylindrical wall 16 and a bottom surface 18. The cylindrical wall 16 is interrupted by notches 20, 22, 24 and 26 extending through the baseat the midpoint of each side of the base. A square cavity 28 is provided in the bottom surface 18 wtih the corners of the cavity being at the midpoints of the sides of the base 12. A cylindrical hub 36 projects upwardly from the center of the bottom of the cavity 28, and a rib 32 extends radially from the hub 30 along the bottom of the cavity 23 to the notch 26. A projection 34 extends upwardly from the bottom of the notch 26 at the end of the rib 32. Rib 32 has a groove 36 in its upper surface. The groove 36 extends longitudinally along the rib 32, and opens into a groove 38 in the hub 30. The groove 38 extends radially across the hub 30 to the center of the hub. As shown in FIGURE 3, a hole 40 extends adjustment knobs being exposed for ease of adjusting the I resistance value setting of the potentiometers. In addition, the otentiometers are mounted sometimes with the adjustment knobs facing upwardly and sometimes with the adjusment knob facing forwardly. Therefore, it is desirable to have a potentiometer which can be easily mounted with the control knob facing in any desired direction.

It is an object of the present invention to provide a potentiometer which is compact and small in size.

It is another object of the present invention to provide a potentiometer which can be easily stack mounted in end-to-end and/ or side-by-side relation with other similar potentiometers.

It is still another object of the present invention to provide a miniature potentiometer which is effectively sealed against moisture.

It is a further object of the present invention to provide a miniature potentiometer having either a top or a side adjustment.

It is a still further object of the present invention to provide a miniature potentiometer having a high degree of reliability and accuracy, but being of economical construction.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

. FIGURE 1 is a perspective view of the potentiometer of the present invention.

FIGURE 2 is an exploded perspective view of the potentiometer of the present invention.

FIGURE 3 is a sectional view taken along line 33 of FIGURE 1.

FIGURE 4 is a sectional view taken along line 4-4 of FIGURE 3.

FIGURE is a sectional view taken along line 5-1; of FIGURE 3.

FIGURE 6 is a sectional view similar to FIGURE 3 showing a modification of the potentiometer of the present invention.

Referring to the drawings, the potentiometer of the present invention is generally designated as 10. As shown in FIGURE 1, potentiometer is substantially cubical, and has no shaft protrusions. The potentiometer 10 can be made as small as on each side.

Referring to FIGURES 2 and 3, potentiometer 10 comprises a substantially rectangular base 12 molded of an electrically insulating plastic. At the bottom of the base 12, a square supporting flange 14 projects from the side through the base 12 from the bottom of the groove 36 at the outer end of the groove. As shown in FIGURE 2, a pair of holes 42a and 425 extends through the base 12 from the bottom of the cavity 28 at diagonally opposite corners of the cavity.

An electrical resistance element, generally designated as 44, is mounted on the base 12. Resistance element 44 comprises a core 46 of an electrical insulating material which is circular in transverse cross-section. A resistance wire 43 is helically wound around and along the core 46. Resistance element 44 is in the form of an annulus with the ends of the resistance element being spaced slightly I apart. As shown in FIGURE 3, the resistance element 4 4 is seated on the bottom surface 18 of the recess in the base 12, and around the cylindrical Wall 16. The ends of the resistance element 44 are seated on the top surface of the projection 34.

As shown in FIGURES 3 and 5, a pair of termination strips 50a and 5% are provided under the ends of the resistance element 44. Termination strips 50a and 5d!) are Of an electrically conductive metal, and are secured to the end portions of the resistance wire winding 48, such as by soldering, brazing or welding. The

termination strips

50a and 50b extend inwardly of the resistance element 44 across the cavity 28 on opposite sides of the hub 30. A pair of

terminal wires

52 and 54 extend through the

holes

42a and 42b in the base 12. The top end portions 52a and 54a of the terminal wires are bent to extend along the cavity 28, and beneath the termination strips 59a and 50b respectively (see FIGURE 5 The termination strips Slla and 5% are secured to the top and portions 52a and 54a of the terminal wires, such as by welding, brazing or soldering. Thus, the

terminal wires

52 and 54 are electrically connected to the ends of the resistance element 44 through the termination strips 50a and 5%.

A contact terminal wire 56 of an electrically conductive metal extends through the hole 40 in the base 12.

The upper portion of the contact terminal wire 56 is bent A contact member, generally designated as 58, is made from a flat sheet of resilient, electrically conductive metal and is rotatably supported on the top end portion 56b of the contact terminal wire 56. Contact member 58 comprises a' circular plate 60 having a central hole 62 therethrough. A resilient contact arm 64 extends radially from the plate 60, and has a U-shaped contact finger 66 at the end thereof. A resilient slip ring contact arm 68 extends I from the plate 68 diametrically opposite the contact arm 64. Slip ring contact arm 68 is provided with a hole 78 'therethrough, and a slip ring wiper contact 71 projecting downwardly from the edge of the hole 70 adjacent the free end of the contact arm 68 (see FIGURE 3). The contact plate 66 is seated on the top surface of hub 38 with the contact arm 68 being bent over the plate 68 so that hole '70 is over hole 62 in the plate 60. The top end portion 56b of the contact terminal wire 56 extends through the

holes

62 and 78 in the plate 60 and resilient slip ring contact arm 68 thus applying pressure to terminal contact wire 56b through slip ring wiper contact 71. Thus, the contact member 58 is rotatably supported on and electrically connected to the contact terminal wire 56. Contact arm 64 is of a length so that the contact finger 66 extends over the resistance element 44. When the resilient contact member 58 is held in position on hub 38, the contact arm 64 is bent so that pressure is applied to contact finger 66 to hold the contact finger in slidable engagement with the resistance element 44.

A cylindrical actuator knob, generally designated as 72, of an electrical insulating material is rotatably mounted on the base 12. A cylindrical flange '74 projects radially outwardly from the knob 72 adjacent to but spaced from the top end thereof. The knob 72 is provided with a cylindrical recess 76 in its bottom surface, a slot 78 extending diametrically across the bottom portion thereof beneath the flange 74, and a blind hole 86 in the center of the bottom of the slot 78. The recess 76 is of a diameter equal to the diameter of the hub 38 of the base 12. The slot 78 is of a width to receive the contact member 58. The hole 88 is of a diameter equal to the diameter of the contact terminal wire 56. An annular groove 82 is provided in the top surface of the flange 74 concentric with the top portion of the knob 72. A stop lug 84 projects radially outwardly from the periphery of the flange 74 (see FIGURES 2 and 4). Actuator knob 72 is provided with a slot 86 extending diametrically across the center portion of the top end thereof. A projection 88 in the form of an arrow head extends upwardly from the top end of the knob 72 at one end of the slot 86. (See FIGURES l and 2.) The actuator knob 72 is mounted on the base 12 with the hub 30 fitting within the recess 76 in the knob, the top end portion 56a of the contact terminal wire 56 fitting in the hole 80 in the knob, and the contact member 58 being within the slot 78 in the knob. Thus, the knob 72 is supported on the base 12 for rotation about the hub 30 and the top end portion 56b of the contact terminal wire 56. When the knob 72 is rotated, the side walls of the slot 78 engage the sides of the contact arm 64 to rotate the contact member 58.

A cover, generally designated as 90, of an electrical insulating material is mounted on the base 12, and encloses the knob 72, contact member 58 and resistance element 44. Cover 90 has a square flat top 92, and rectangular flat sides 94. The free ends of the sides 94 are seated on the flange 14 of the base 12, and are secured thereto, such as by a suitable cement. The top 92 of the cover 90 is provided with a central, circular hole 96 therethrough through which the top end portion of the knob 72 extends. On the inner surface of the top 92 of the cover 98 there is provided an annular projection 98 which is concentric with the hole 96. The projection 98 is semi-circular in transverse cross-section and is directly over the annular groove 82 in the flange I4 of the knob 72. A normally flat, annular sealing washer 100 is provided between the projection 98 and the groove 82 in the flange 74 of the knob. As shown in FIGURE 3, the projection 98 bends the sealing washer 100 into the groove 82 so as to provide a seal between the flange 74 and the top 92 of the cover. As shown in FIGURE 4, a stop lug 102 projects inwardly from the sides 94 of the cover across the path of travel of the stop lug 84 on the flange 74 of the knob 72. As shown in FIGURES 1 and 2, the top 92 of the cover 90 is provided on its outer surface with a plurality of raised indicating marks 164 uniformly spaced around the hole 96 in the top. The odd numbered indicating marks 184 are provided with an indicia number. One side 94 of the cover 98 is provided with a shallow groove 106 in its outer surface extending from the free edge thereof. Groove 106 is in alignment with a notch 188 in the edge of the flange 14 of the base 12. One purpose of the groove 106 and notch 108 is to permit ease of properly mounting the cover 96 on the base 12.

In the operation of the potentiometer 16 of the present invention, the resistance value thereof is varied by inserting a screw driver or similar instrument in the slot 86 in the top end of the actuator knob 72, and rotating the knob. Rotating the actuator knob 72 rotates the contact memher 58 so as to slide the contact finger 66 along the resistance element 44. Since the contact member 58 is electrically connected to the contact terminal wire 56, movement of the contact finger 66 along the resistance element 44 varies the electrical resistance between the contact terminal wire 56 and the

terminal wires

52 and 54, which are electrically connected to the ends of the resistance element. The stop lugs 84 and 162 are arranged so that when the contact finger 66 is at the ends of the resistance element 44, the stop lug 84 engages the stop lug 102 to prevent further rotation of the actuator knob 72. Thus, the contact finger 66 is prevented from being moved across the space between the ends of theresistance element 44, and is limited to being moved only along the length of the resistance element. The arrow head projection 88 on the top surface of the actuator knob 72 is positioned directly over the contact arm 64, and the zero and 10 indicating marks 104 are located directly over the ends of the resistance element 44. Thus, the arrow head projection 88 and indicating marks 104 provide an indication of the position of the contact finger 66 along the resistance element 44. Since the potentiometer It) is in the shape of a cube, and all of the terminal wires project from the base of the potentiometer, a plurality of the potentiometers 10 can be mounted in side-by-side relation on a mounting panel or printed circuit board. Thus, a plurality of the potentiometers of the present invention can be mounted together in a minimum amount of space, yet with the actuating knobs of the potentiometers exposed to permit ease of adjustment of the potentiometers.

The potentiometer 16 of the present invention is constructed so that when it is mounted on a printed circuit board or similar mounting panel, it is adjustable from the top. However, it is often desirable to mount the potentiometer so that it is adjustable from the side. FIGURE 6 .shows the potentiometer 10 of the present invention modified so that it is adjustable from the side when mounted on a printed circuit panel or the like. To so modify the potentiometer 10, a L-shaped plate, generally designated as 118, is mounted on the potentiometer 10, such as by a suitable cement. Plate 110 has a rectangular base leg 112 which extends across the base 12 of the potentiometer, and a rectangular side leg 114 which extends across the sides 94 of the potentiometer which has the groove 186 therein. The base plate 112 is provided on its inner surface with a groove 116 which extends from the hole 40 in the base 12 to a groove 118 in the inner surface of the side leg 114 which is in alignment with the groove 106 in the side of the potentiometer.

A hole 126 extends through the side leg 114 at the end of the groove 118. The contact terminal wire 56 is bent to extend along the

grooves

116 and 118, and through the hole 120 to project from the side of the potentiometer 10. The base leg 112 of the plate 110 is also provided on its inner surface with a pair of grooves and holes, not shown, through which the

terminal wires

52 and 54 extend so that the

terminal wires

52 and 54 also project from the side of the potentiometer 19. Thus, when the potentiometer 10 modified with the plate 110 is mounted on a printed circuit board or the like, the actuator knob 72 is side adjustable.

Thus, there is provided by the present invention a trimmer potentiometer which is compact and small in size, and which can be easily stack mounted in side-by-slde relation with other similar potentiometers. Also, the potentiometer of the present invention can be easily modified for either side or top adjustment when mounted on a printed circuit board or the like. Although the potentiometer of the present invention has a high degree of reliability and accuracy, it is of economical construction since it is made up of a minimum number of parts. In addition, the potentiometer of the presentinvention is effectively sealed against moisture.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and accordingly, reference should be made to the appended claims, rather than to the foreging specification as indicating the scope of the invention.

' We claim:

1. A potentiometer comprising a base, an annular re sistance element mounted on a surface of said base with the ends of the resistance element being spaced apart, a pair of terminal wires extending through said base, each of said terminal wires being electrically connected to a separate end of said resistance element, a contact terminal wire extending through said base and projecting beyond said surface of the base at the center of the resistance element, a contact member of an electrically conducting metal rotatably mounted directly on and contacting the projecting portion of the contact terminal wire and so as to be electrically connected thereto, said contact member having a contact arm slidably engaging the resistance element, an actuator knob mounted and supported on said surface of the base and rotatable about the projecting portion of the contact terminal wire, said actuator knob drivingly engaging said contact member so that rotation of said knob rotates the contact member, and a cover mounted on said base and encompassing the resistance element, contact member and actuator knob, said cover having an opening therethrough through which the actuator knob extends.

2. A potentiometer in accordance with claim 1 in which the contact member comprises a contact plate having a hole therethrough, the contact arm extends from an edge of the contact plate, and a second arm extends from an edge of the contact plate and is bent back over the contact plate, said second arm having a hole therethrough over the hole in the contact plate, and the projecting portion of the contact terminal wire extends through the 6 holes in the contact plate and second arm so that the contact member is rotatable around the contact terminal wire. 7

3. A potentiometer in accordance with claim 2 in which the base has a cylindrical hub projecting from its said surface at the center of the resistance element, the projecting portion of the contact terminal wire extends from the center of the hub, and the actuator knob has a cylindrical recess in its bottom surface which receives the hub and a blind hole therein which receives the projecting portion of the contact terminal wire so that the knob is rotatably supported on the hub and the contact terminal wire.

4. A potentiometer in accordance with claim 3 in which the actuator knob has a slot extending transversely thereacross at the bottom end thereof, the contact member fits in said slot with the contact arm projecting beyond the knob, the side walls of said slot engaging the contact member so that rotation of said knob rotates the contact member.

5. A potentiometer in accordance with claim 1 in which the actuator knob has an annular flange juxtaposed to the inner surface of the top of the cover, and sealing means is provided between said flange and the cover.

6. A potentiometer in accordance with claim 5 in which the actuator knob flange has an annular groove in its surface which faces the top of the cover, the top of the cover has an annular projection directly over the groove in the flange, and a sealing ring is compressed between said projection and the groove.

References (lited by the Examiner UNITED STATES PATENTS 1,465,872 8/23 Schoenung 1 338 2,406,503 8/46 Miller 338-164 2,765,384 10/56 Arisman 338-197 2,839,642 6/58 Dickinson et a1 338174 X 2,884,506 4/59 Graustein 338 -175 X 3,096,499 7/63 Hudson et a1 338--174 X 3,105,949 10/63 Zarillo 338174 FOREIGN PATENTS 250,766 4/26 Great Britain. 684,067 12/52 Great Britain.

63,137 3/55 France.

RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

Claims

1. A POTENTIOMETER COMPRISING A BASE, AN ANNULAR RESISTANCE ELEMENT MOUNTED ON A SURFACE OF SAID BASE WITH THE ENDS OF THE RESISTANCE ELEMENT BEING SPACED APART, A PAIR OF TERMINAL WIRES EXTENDING THROUGH SAID BASE, EACH OF SAID TERMINAL WIRES BEING ELECTRICALLY CONNECTED TO A SEPARATE END OF SAID RESISTANCE ELEMENT, A CONTACT TERMINAL WIRE EXTENDING THROUGH SAID BASE AND PROJECTING BEYOND SAID SURFACE OF THE BASE AT THE CENTER OF THE RESISTANCE ELEMENT, A CONTACT MEMBER OF AN ELECTRICALLY CONDUCTING METAL ROTATABLY MOUNTED DIRECTLY ON AND CONTACTING THE PROJECTING PORTION OF THE CONTACT TERMINAL WIRE AND SO AS TO BE ELECTRICALLY CONNECTED THERETO, SAID CONTACT MEMBER HAVING A CONTACT ARM SLIDABLY ENGAGING THE RESISTANCE ELEMENT, AN ACTUATOR KNOB MOUNTED AND SUPPORTED ON SAID SURFACE OF THE BASE AND ROTATABLE ABOUT THE PROJECTING PORTION OF THE CONTACT TERMINAL WIRE, SAID ACTUATOR KNOB DRIVINGLY ENGAGING SAID CONTACT MEMBER SO THAT ROTATION OF SAID KNOB ROTATES THE CONTACT MEMBER, AND A COVER MOUNTED ON SAID BASE AND ENCOMPASSING THE RESISTANCE ELEMENT, CONTACT MEMBER AND ACTUATOR KNOB, SAID COVER HAVING AN OPENING THERETHROUGH THROUGH WHICH THE ACTUATOR KNOB EXTENDS.