US3855565A - Variable resistance control with differentially resilient contacts - Google Patents

Variable resistance control with differentially resilient contacts Download PDF

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Publication number
US3855565A
US3855565A US00457182A US45718274A US3855565A US 3855565 A US3855565 A US 3855565A US 00457182 A US00457182 A US 00457182A US 45718274 A US45718274 A US 45718274A US 3855565 A US3855565 A US 3855565A
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United States
Prior art keywords
contact
resistance element
contactor
inner arm
arms
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00457182A
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English (en)
Inventor
J Robinson
Benthuysen J Van
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CTS Corp
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CTS Corp
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Publication date
Application filed by CTS Corp filed Critical CTS Corp
Priority to US00457182A priority Critical patent/US3855565A/en
Application granted granted Critical
Publication of US3855565A publication Critical patent/US3855565A/en
Priority to CA219,839A priority patent/CA1032625A/fr
Priority to GB10312/75A priority patent/GB1481922A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C1/00—Details
    • H01C1/12—Arrangements of current collectors

Definitions

  • Trimming a circuit requires the introduction of a resistance into the circuit until an optimum condition occurs. For example, if 42,000 i 100 ohms of a 100,000
  • variable resistance controls to monitor and/or graphically identify the characteristics thereof. For example, electrical noise occurs in the circuit while the contactor is being wiped across the resistance element and is normally identified as equivalent noise resistance" (ENR).
  • ELR equivalent noise resistance
  • ENR or dynamic contact resistance is measurable in ohms and as a percent of the total resistance by following standarized test procedures well known in the art. Again with the advent of solid state devices such as transistors and integrated circuits, which are extremely quiet in comparison with vacuum tubes, it has become increasingly important to reduce the ENR of variable resistance controls. Various theories are continually being propounded for decreasing the ENR of a variable resistance control.
  • the use of double contacts as exemplified in U.S. Pat. No. 2,178,283 for wipingly engaging an arcuate resistance element can be employed to decrease the ENR of a variable resistance control. According to the prior art, the contacts should be designed to exert the same amount of pressure on the arcuate resistance element to ensure smoother and more dependable operation of the control.
  • variable resistance control having various desirable features as those disclosed above.
  • Another object of the present invention is to provide a variable resistance control with a contactor having a pair of differentially resilient contacts wipably engaging the resistance element of a variable resistance control.
  • a further object of the present invention is to provide a variable resistance control with a contactor having arms with different spring rates for supporting the contacts.
  • Another object of the present invention is to provide a variable resistance control with an ENR lower than currently obtainable.
  • the present invention is concerned with a variable resistance control having a contactor with. differentially resilient contacts wipably engaging a resistance element and a collector for eliminating intermittency anddecreasing dynamic contact resistance
  • the contactor comprises a metal ring, a pair of outer arms integral with the metal ring and extending outwardly therefrom toward each other for supporting the differ" entially resilient outer contact wipably engaging the resistance element, an inner arm integral with the metal ring extending outwardly toward the outer contact and supporting the differentially resilient inner contact wipably engaging the resistance element, and a main contact on the ring wipably engaging the collector.
  • the metal ring comprises a pair of semicircular sections performed to define an obtuse angle therebetween.
  • FIG. 1 is an isometric view of an improved variable resistance control built in accord with the present invention
  • FIG. 2 is an enlarged sectional view taken along lines IIII of FIG. 1;
  • FIG. 3 is a graph depicting curves of the resistance gradient and ENR as a percent of the total resistance
  • the supporting bracket 11 comprises a metal stamping having a snap-in center terminal 12 extending downwardly from the center portion of the bracket for mounting the control to a panel or the like.
  • a collector ring 13 embossed from the center portion of the bracket extends inwardly thereof into an opening 21 of the base for aligning the base with the bracket 11.
  • Tabs 14 projecting forwardly of the bracket 11 engage notchess 22 in the base for preventing relative rotation therebetween.
  • An arcuate carbon resistance element 23 is secured to the base with a pair of end terminals 24.
  • the contactor 40 constrained to rotate with the member wipably engages the collector ring l3 and the resistance element intermediate the ends thereof for providing an infinite number of resistance values between one of the end terminals 24 and the center terminal 12 electrically connected to the collector ring 13.
  • the contactor 40 made from metal comprises a body portion or circular ring 41 (see FIG. 5) having a pair ofpivots 42 extending outwardly from the circular ring for .pivotally supporting the contactor against the rotatable member 30 thereby permitting pivotal action of the contactor with respect to the resistance element 23 and the collector ring 13.
  • Each of the pivots 42 are provided with an upturned end 42a further constraining the contactor to move with the rotatable member 30.
  • the circular ring 41 of the contactor 40 is folded about a line 41a passing through the pivots 42. Such folding or performing divides the circular ring in half and forms a pair of semicircular sections 43, 44 having an obtuse angle 41b therebetween.
  • a pair of outer arms 45 integral with and extending tangentially outwardly from opposite ends of the semi-circular section 43 converge towrd each other and are integrally joined togeter (see FIG. 5) at their extremities 45a.
  • an inner arm 46 extends radially outwardly from the semicircular section 43 of the contactor 40 toward the junction or outer extremity 45a of the outer arms 45.
  • an outer contact 47 and an inner contact 48 are formed directly from the outer and inner arms, respectively, it is to be understood that the contacts 47, 48 can be fixedly secured to the extremities of the outer andinner arms.
  • the outer arms 45 define an acute angle 45b and the inner arm bisects the acute angle 45b with the outer contact 47 being spaced from the inner contact 48.
  • the length of each of the outer arms 45 is greater than the length of the inner arm 46 resulting in a different spring rate for the outer arm and the inner arm.
  • the difference in spring rates of the arms 45, 46 carrying respectively the inner and outer contacts 47, 48 produces a pair of differentially resilient contacts 47, 48 wipably engaging the resistance element 23'.
  • the difference in spring rate between the inner and outer amrs 45, 46 is increased since the outer arms 45 flex as leaf springs throughout their length while the inner arm 46, being shorter and stubbier,.flexes generally as a torsion spring because of the twisting affect of the portions 43a, 43b of the semicircular section 43 between the inner arm and the outer arms.
  • the inner contact 48 can be carried by more than one arm so long as the effective pres-- sure exerted by the inner contact 48 against the resistance element 23 is different than the pressure exerted by the outer contact 47.
  • a main contact 49 carried by the semicircular section 44 wipably engages the collector ring 13 and electrically connects the inner and outer contacts 47, 48 wipably engaging the resistance element 23 to the center terminal 12.
  • a large number of controls as exemplified and shown in FIG. 1 of the drawings are employed for trimming electronic circuits.
  • the controls are adjusted to make the equipment operable and then usually are not adjusted unless certain components are replaced in the circuit.
  • Such controls are designated as factory adjust controls while other controls adjusted periodically by the user are commonly referred to as user adjust controls.
  • the control 10 is employed for trimming electronic circuits, e.g., one of the circuits in a television set, it is imperative that a particular resistance value be obtainable from the control otherwise the circuit cannot be properly trimmed.
  • a control is intermittent when a particular resistance value cannot be obtained because the contactor 40 as best shown in FIG.
  • the nonconductive portion 23a of the resistance element 23 is usually a clump ofnonconductive binder or a small particle produced during the shearing operation of the laminated fiber forming the substrate 23b of the resistance element and bonded to the substrate with the binder.
  • Such laminated fiber particles 23a are frequently electrostatically attracted to the substrate and are very difficult to remove prior to application of the carbon resistance paint onto the substrate.
  • the resistance obtainable between one of the end terminals 24 of the control 10 and the center terminal 12 as the contactor is moved from one end of the resistance element to the other is graphically depicted in FIG. 3 of the drawings, and is commonly referred to as a resistance gradient wave 50.
  • the resistance gradient curve 50 of a control depicts the change in resistance obtained by measuring the resistance between the contact wipingly engaging the resistance element and one of the end terminalsas a function of rotation or movement of the contactor from one end of the resistance element to the other end thereof.
  • An ideal resistance gradient curve would be depicted as a straight line having a slope determined by the total resistance as a function of total rotation.
  • the contact resistance When the control is designed in a circuit as a user adjust control, it-is necessary that the contact resistance be kept to a minimum. Contact resistance is of little importance when the control 10 is used as a trimmer since any resistance in or between the contact and the resistance element of the control becomes a part of the total resistance in the circuit. However, in certain applications where the control is frequently adjusted by the user, it is preferable that the contact resistance commonly referred to as equivalent noise resistance (ENR) be kept to a minimum and/or as uniform as possible. As shown in FIG. 3, the ENR curve 52 of a control with a single contact is greater than the ENR curve 53 of a double contact such as when the inner and outer contacts of the presentinvention wipably engage the resistance element.
  • ENR equivalent noise resistance
  • ENR is essentially a measurement of the contact resistance as the contact wipingly moves across the resistance element. During such dynamic conditions, the contact resistance becomes substantial, e.g., the ENRcu'rve can become as high as 10 percent. Generally an ENR curve for a single contact control is considered satisfactory if below three percent. The average ENR curve for controls employing the contactor 40 is less than 1% percent and slightly higher for prior art double paddle contactors. An increase in contact resistance from a static to a dynamic condition results from the movement and bouncing of the contacts across the resistance element.
  • the spring rate of the inner contact 48 will be different from the spring rate of the outer contact 47.
  • This difference in spring rate between the two springs effectively alters the bounce or frequency of thetwo contacts wipingly engaging the resistance element and apparently results in a slightly lower ENR than would otherwise be obtained.
  • the current density or gradient through a mid section of the resistance element 23 from the inner edge to the outer edge thereof generally follows an exponential curve such as shown in FIG. 6 of the drawings, the high current density being at the inner edge of the element 23. It has been found that by making the pressure of the inner contact 48 at least several percent greater than the 'pressure of the outer contact 47 against the element a slightly improved ENR curve is obtainable.
  • variable resistance control of claim 1 wherein the inner contact exerts a greater pressure against the resistance element than the outer contact.
  • a variable resistance control having a resistance element, a collector in spaced relationship to the resistance element, anelectrically conductive contactor engaging the resistance element and the collector, means for moving the contactor intermediate the ends; of the resistance element, said contactor comprising a body portion, a pair of outer arms extending outwardly from opposite sides of the body portion and converging toward each other, an outer contact carried by the arms and wipably engaging the resistance element, an inner arm integral with the body portion and extending outwardly therefrom toward the outer contact, the end of said inner arm being spaced from the outer contact, an inner contact disposed on the distal end of the inner arm in spaced relationship to the outer contact and wipably engaging the resistance element, and a main contact carried by the body portion and wipably engaging the collector.
  • variable resistance control of claim 3 wherein the body portion of the contactor is a metal ring defined by a pair of semicircular sections, each of the semicircular sections of the ring being preformed and defining an obtuse angle therebetween.
  • variable resistance control of claim 4 wherein the outer and inner arms are integral with one of the semicircular sections of the metal ring, and the main contact is integral with the other of the semicircular sections of the metal ring.
  • variable resistance control of claim 3 wherein the outer arms define an acute angle and the innerarm bisects the acute angle.
  • variable resistance control of claim 3 wherein the length of each of the outer arms is greater than the length of the inner arm resulting in a different spring rate for the inner arm and the outer arms.
  • variable resistance control of claim 4 wherein the outer arms extend tangentially outwardly from the one of the semicircular sections and the inner arm extends radially outwardly from the one of the semicircular sections.
  • variable resistance control of claim 3 wherein the inner contact exerts a greater pressure against the resistance element than the outer contact.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Adjustable Resistors (AREA)
US00457182A 1974-04-02 1974-04-02 Variable resistance control with differentially resilient contacts Expired - Lifetime US3855565A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US00457182A US3855565A (en) 1974-04-02 1974-04-02 Variable resistance control with differentially resilient contacts
CA219,839A CA1032625A (fr) 1974-04-02 1975-02-11 Resistance variable a contacts d'elasticite differente
GB10312/75A GB1481922A (en) 1974-04-02 1975-03-12 Variable resistance control

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00457182A US3855565A (en) 1974-04-02 1974-04-02 Variable resistance control with differentially resilient contacts

Publications (1)

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US3855565A true US3855565A (en) 1974-12-17

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US (1) US3855565A (fr)
CA (1) CA1032625A (fr)
GB (1) GB1481922A (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3965454A (en) * 1974-09-12 1976-06-22 P. R. Mallory & Co., Inc. Means lowering contact resistance in variable resistance control
US4095209A (en) * 1976-04-29 1978-06-13 Cts Corporation Electrical resistor and method of making same
US4112250A (en) * 1977-05-26 1978-09-05 Allen-Bradley Company Terminal for electrical component and method of making same
US4168568A (en) * 1976-04-29 1979-09-25 Cts Corporation Electrical resistor and method of making same
US4205296A (en) * 1978-10-10 1980-05-27 Allen-Bradley Company Rheostat trimmer
US4210896A (en) * 1978-04-24 1980-07-01 Cts Corporation Variable resistance control and method of making the same
DE3816446A1 (de) * 1987-05-15 1988-11-24 Murata Manufacturing Co Regelwiderstand zur oberflaechenmontage

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2826785C2 (de) * 1978-06-19 1984-02-09 Novotechnik Kg Offterdinger Gmbh & Co, 7302 Ostfildern Durchdrehbares Drehpotentiometer

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2093252A (en) * 1934-12-10 1937-09-14 Chicago Telephone Supply Co Electrical contacting device
US2177291A (en) * 1939-02-02 1939-10-24 Chicago Telephone Supply Co Variable resistance device
US2632830A (en) * 1950-12-27 1953-03-24 Mallory & Co Inc P R Indexed control
US3576514A (en) * 1969-01-02 1971-04-27 Bourns Inc Potentiometer with embedded reversely bent contact wires

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2093252A (en) * 1934-12-10 1937-09-14 Chicago Telephone Supply Co Electrical contacting device
US2177291A (en) * 1939-02-02 1939-10-24 Chicago Telephone Supply Co Variable resistance device
US2632830A (en) * 1950-12-27 1953-03-24 Mallory & Co Inc P R Indexed control
US3576514A (en) * 1969-01-02 1971-04-27 Bourns Inc Potentiometer with embedded reversely bent contact wires

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3965454A (en) * 1974-09-12 1976-06-22 P. R. Mallory & Co., Inc. Means lowering contact resistance in variable resistance control
US4095209A (en) * 1976-04-29 1978-06-13 Cts Corporation Electrical resistor and method of making same
US4168568A (en) * 1976-04-29 1979-09-25 Cts Corporation Electrical resistor and method of making same
US4112250A (en) * 1977-05-26 1978-09-05 Allen-Bradley Company Terminal for electrical component and method of making same
US4210896A (en) * 1978-04-24 1980-07-01 Cts Corporation Variable resistance control and method of making the same
US4205296A (en) * 1978-10-10 1980-05-27 Allen-Bradley Company Rheostat trimmer
DE3816446A1 (de) * 1987-05-15 1988-11-24 Murata Manufacturing Co Regelwiderstand zur oberflaechenmontage

Also Published As

Publication number Publication date
CA1032625A (fr) 1978-06-06
GB1481922A (en) 1977-08-03

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