Electrical rotary potentiometer

• US 5,952,912 A
• Filed: 05/14/1998
• Issued: 09/14/1999
• Est. Priority Date: 05/16/1997
• Status: Expired due to Fees

• Current Assignee: Preh-Werke GmbH & Company KG
• Original Assignee: Preh-Werke GmbH & Company KG
• Inventors: Bauer, Karl-Heinz, Moret, Reinhold, Brueggemann, Ulrich
• Primary Examiner(s): Donovan, Lincoln
• Assistant Examiner(s): LEE, KYUNG S
• Application Number:
  US09/078,322
• Time in Patent Office: 488 Days
• Field of Search: 338/162, 338/157, 338/161, 338/160
• US Class Current: 338/162
• CPC Class Codes: H01C 10/14 adjustable by auxiliary driving means
• CPC Class Codes: H01C 10/28 the contact rocking or rolling along resistive element or taps

Abstract

Rotary potentiometers known in the art having sensitive adjustment of the control knob require a stepdown gearing and have differing moments of friction that vary between devices. By contrast, in a rotary potentiometer of this invention a control knob (3) is mounted on at least three balls (6) that move, guided by a cage disk (7), in a housing groove (8) formed by a radial wall (9) and an axial wall (10), against which the balls (6) are urged by a load pressure of a conical bearing surface (11 or 12) of the control knob (3). The radial and axial wall bearing surfaces have contact and resistive strips (13, 14) that are short circuited by the balls (6). The control knob (3) has a stop lug (15) which contacts housing lugs (16) to limit a manipulation adjustment angle (4) and which, during operational adjustment, contacts at least one of two stop lugs (17) of the cage disk (7), which are positioned at an angle that corresponds approximately to one-half the manipulation adjustment angle (4) and the resistor tap angle (5). This design results in reduced cost and functional improvement.

Claims

1. An electrical rotary potentiometer having:

a housing;

a rotary control knob mounted in the housing and rotatable relative to the housing, a manipulation adjustment angle of which is larger than a resistor tap angle of the electrical rotary potentiometer;

at least three balls on which the control knob is supported for movement in a housing groove formed by a radial wall and an axial wall toward which the balls are urged by load pressure of a conical bearing surface of one of the housing and control knob;

a cage disk for guiding movement of the balls;

wherein the radial and axial wall bearing surfaces have contact segments and resistive strips that are short circuited by the balls, and wherein the control knob has at least one knob stop lug for contacting housing lugs to limit the manipulation adjustment angle and for, during operational adjustment, contacting at least one of two disk stop lugs of the cage disk, said disk stop lugs being positioned at an angle that corresponds approximately to one-half of the manipulation adjustment angle and a resistor tap angle.

2. An electrical rotary potentiometer as in claim 1, wherein the load pressure of the conical bearing surface is created by at least one spring mounted between the housing and the control knob.

3. An electrical rotary potentiometer as in claim 2, wherein one of the resistive strips and contact segments extend out from the housing via terminal lugs 26.

4. An electrical rotary potentiometer as in claim 3, wherein the resistive strip comprises a foil set in the housing, each end section of which has a conducting layer.

5. An electrical rotary potentiometer as in claim 2, wherein the control knob has an indexing means comprising indication notches on one of the housing and the control knob, with spring arms of the spring positioned between the housing and the control knob engaging therein.