US3868621A

US3868621A - Variable resistor device

Info

Publication number: US3868621A
Application number: US402008A
Authority: US
Inventors: Nobuo Kitamura; Miroshi Fukagawa
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1972-10-04
Filing date: 1973-10-01
Publication date: 1975-02-25
Anticipated expiration: 1992-02-25
Also published as: JPS5241562Y2; FR2202345B1; JPS4982233U; FR2202345A1; CA994881A; ES419316A1; DE2349540A1; GB1424914A; BR7307695D0; NL7313685A; IT995591B

Abstract

A variable resistor device comprising a housing formed by walls, one of which is provided with a resistive material on its inner surface, a rotatable screw shaft mounted in the housing for elongating along the resistive material on the inner surface of the wall and a movable contact having a portion for coming in contact with the resistive material and a portion for engaging with the screw thread of the screw shaft to be shifted in contact with the resistive material by the rotation of the screw shaft, whereby the variable resistance is obtained between one end of the resistive material and the screw shaft.

Description

United States Patent- [1 1 Kitamura et al.

[451 Feb. 25, 1975 VARIABLE RESISTOR DEVICE [75] Inventors: Nobuo Kitamura, Sagamihara;

Miroshi Fukagawa, Tokonama, both of Japan [30] Foreign Application Priority Data 3,665,364 5/1972 Maurice 338/180 3,732,520 5/1973 VanBenthuysen et al.. 338/180 3,742,421 6/1973 Rooijen 338/180 Primary Examiner-Bruce A. Reynolds Attorney, Agent, or Firm-Lewis H. Eslinger; Alvin Sinderbrand 57 ABSTRACT A variable resistor device comprising a housing formed by walls, one of which is provided with a resistive material on its inner surface, a rotatable screw shaft mounted in the housing for elongating along the resistive material on the inner surface of the wall and a movable contact having a portion for coming in contact with the resistive material and a portion for engaging with the screw thread of the screw shaft to be shifted in contact with the resistive material by the rotation of the screw shaft, whereby the variable resistance is obtained between one end of the resistive material and the screw shaft.

3 Claims, 11 Drawing Figures PATENTEUFEBZSISYS ya+a VARIABLE RESISTOR DEVICE BACKGROUND OF THE INVENTION l Field of the Invention This invention relates generally to mechanical variable. resistor devices, and more particularly to a variable resistor unit having an improved sliding mechanism for changing the resistance value and suitable for being used as avoltage supplying device in voltage controlled tuners of, for example, a television receiver.

2. Description of the Prior Art There are, inrough classification, two types of tuners for a signal receiver, such as a television reciever,- whichis adapted to receive selectively a plurality of signals transmitted with-different carrier frequencies, respectively. One of the two types is a mechanically selecting tuner in which a plurality of resonance circuits have resonahtfrequencies corresponding to the signals to'be selectively received, respectively, are provided and these resonance circuits are selected by movable mechanical contacts to receive a selected one of the transmitted signals. The other of the two types is a voltage controlled tuner in which a resonance circuit having a voltage controlled variable reactance element is provided to receive a selected one of the transmitted signals by changing its resonant frequency which can be varied by changing a voltage supplied to the voltage controlled variable reactance element.

In general, compared with the former, the latter has an advantage that the movable mechanical contacts which are apt to cause troubles are eliminated. In the voltage controlled tuner, a plurality of variable resistor units are used for producing control voltages to be selectively supplied to the voltage controlled variable reactance element to set the resonance circuit to have a resonant frequency corresponding to the selected one of the transmitted signal. In this case, the variable resistor unit, is required to be able to vary its voltage value continuouslyv in a predetermined range in order to produce several control voltages, each value of which is determined in response to the carrier frequency of the selected signal to be received, although each of the variable resistorunit's, is arranged to produce one of the severalcontrol voltages inactu al use. In order to' comply with this requirement, a sliding mechanism for varying the resistance value is usually provided.

Various variable resistor units have been previously proposed for such a use, however, they need a number of parts and are complicated in construction.

OBJECT OF THE INVENTION An object of this invention is toprovide an improved variable resistor device having a simple mechanism for varying the resistance value therein.

Another object of this invention is to provide a compact variable resistor device which contains threin an improved slidable contact for varying the resistance value.

Further, another object of this invention is to provide a compact variable resistor unit suitable for being utilized as a control voltage supplying device for a variable reactance element in a voltage controlled tuner.

SUMMARY OF THE INVENTION A variable resistor device of this invention belongs to sliding variable resistors which provides a variable resistance value in response to the position of a sliding contact therein. In this invention, a housing formed by a plurality of walls is provided and a resistive material is provided, for example, by coating on the inside surface of one of the walls. In the housing, a rotatable screw shaft is mounted and a contact which is slidable on the resistive material is engaged with the rotatable screw shaft to be moved in contact with the resistive material by the rotation of the screw shaft. This slidable contact is formed by a resilient conductive material, for

example, a bent metal plate and provided with an engaging portion directly engaging with the screw thread of the rotatable screw shaft, so that the sliding mechanism is simple in construction and assembly, and the wholeof the variable resistor device can be constructed BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of details of one embodiment of variable resistor devices according to the present invention;

FIG. 2 is a plane view of the variable resistor device shown in FIG. I;

FIG. 3 is a sectional view taken along the line IIIIII in FIG. 2;

FIG. 4 is a sectional view taken along the line lVIV in FIG. 2;

FIG. 5 is a side view seen to the line VV in FIG. 2;

FIGS. 6 8 are partial views of the variable resistor device shown in FIG. 1;

FIG. 9 is a sectional view taken along the line IX-IX in FIG. 7;

FIG. 10 is a sectional view taken along the line X-X in FIG. 7; i

FIG. 11 is-an enlarged: sectional view of that shown in FIG. 10 used for explanation of one of featured portions of variable resistor devices according to the present invention. I 7

DESCRIPTION OF THE PREFERRED EMBODIMENT cording to this inventionconsists of an elongated housing box 2 the upper surface of which is opened, a rotatable'screw shaft 3 with screw threads which is located in the elongated housing box 2 along its longitudinal direction, a lid board or resistor board 6 which closes the opening 4 of the housing box 2 and has a resistive material coated on its inside surface to form a resistor portion 5 (refer to FIG. 6), and a movable contact 7 which is inserted between the rotatable screw shaft 3 and the resistor portions.

As shown in FIGS. 2 to 6, the rotatable screw shaft 3 is assembled in the housing box 2 to pass therethrough along its longitudinal direction and is rotatably supported at its both end portions by bores 8 formed in the side end walls of the housing box 2. A gear 9 is formed integrally with the rotatable screw shaft 3 at its one end portion while a resilient plate 10 is insertedto the rotatable screw shaft 3 at its other end portion to thereby prevent the rotatable screw shaft 3 from coming out from the housing box 2. A pair of connecting

terminals

11 and 12 are led out through the resistor board 6 from the both ends of the resistive material 5 on the resistor board 6 to the outside surface thereof. Five cutouts 13 of substantially trapezoid configuration are formed on the resistor board 6 at its peripheral portion,'while five projections 14 of corresponding trapezoid configuration are formed on the upper edge of the housing box 2 at predetermined positions, respectively.

-The five trapezoid cutouts 13 formed in the resistor board 6 receive the five corresponding trapezoid projections 14 formed on the upper edge of the housing box 2, respectively, to close the upper opening 4 of the housing box 2 and thus to form a housing as a whole. A connectingterminal 21 is provided such that its one end is electrically connected to the rotatable screw shaft 3 at one end thereof in the housing box 2 and the other end of the connecting terminal 21 is projected outwardly beyond the resistor. board 6.

As shown in FIGS. 7 to 10, themovable contact 7 consistsof a resilient conductive plate which is bent. At the topof the bent portion of the movable contact 7, it isembossed to form a pair of left and right contact points 15. One end 16 of the movable contact 7 is bent downwardly with an inclination in accordance with the thread angle of a screw thread 20 formed on the rotatable screw shaft 3, and has formed a cutout 17 of substantially delta shape at'its approximately center position. The delta shape cutout 17 engages with the screw thread 20 of therotatable screw shaft 3.'The movable contact 7 has formed integrally therewith, at its other end 18, a pair of guiding portions 19 which extend outwardly therefrom along the rotatable screw shaft 3.

The thus formed movable contact 7 is located betweenthe rotatable screw shaft 3 and the resistor portion 5 against its resiliency. Thus, the pair of contact points of the movable contact 7 engage with the resistor portion 5, the cutout 17 formed in one end 17 of the movable contact-7 engages with the screw thread of therotatable screw'shaft 3 on its upper side, and the pair of guiding portions 19 formed on one end 18 of the movable contact 7 are supported by therotatable screw shaft 3 by abutment therebetween.

when the variableresistor device 1 constructed as above is employed as a voltage controlled tuner, a plurality of-the variable resistor devices 1 the number of which is,-selected in accordance with that of required channels are arranged. around the channel selecting shaft of a tuner which is intermittently moved ,with a constant pitch in'a turret-like manner. When the knob of the tuner for selecting the channel is operated to rotate the channel selection shaft ofthe tuner sequentially, three connecting

terminals

11, 12 and 21 of the selected variable'resistor device are sequentially connected to a spring contact provided in the tuner proper to apply to, for example, a variable capacitor diode, which forms a receiving resonance circuit, a control voltage to enable the variable capacitor diode to have such a capacity as can receive a desired channel signal.

In this case, if afine adjusting knob is rotated, a fine adjustment driving gear which is rotated in ganged relation with the fine adjusting knob meshes with the gear 9'attached to the rotatable screw shaft 3 of the variable resistor device 1 which corresponds to the received channel and is connected to the resonance circuit formed by the variable capacitor diode through three connecting

terminals

11, 12 and 21 and spring contact. Thus, the gear 9 is rotated, the. movable contact 7 is moved, and the contact points 15 slide on the resistor portion 5, so that the resistance value of the variable resistor device 1 is fine-adjusted to provide a predetermined control voltage for the variable capacitor diode for the received channel between the connecting

terminals

11 and 21 or 12 and 21. ln other words, when the rotatable screw shaft 3 is rotated and adjusted by the gear 9, the movable contact 7, which engages at its end 16 with the screw thread 20 of the rotatable screw shaft 3, is adjusted to slide on the resistor portion 5 in accordance with the rotation of the rotatable screw shaft 3. In response to the, adjustment of the movable contact 7, the contact position of the contact points 15 is adjusted relative to the resistor portion 5 to achieve the fine adjustment of the resistance value between the connecting terminals 11 and 2] or between the connecting

terminals

12 and 21.

The other end 18 of the movable contact 7 contacts with the upper surface of the rotatable screw shaft 3 through the pair of guiding portions 19. in other words, the guiding portions 19 do not engage with the screw thread 20 of the rotatable screw shaft 3 but only contact with the upper surface of the rotatable screw shaft 3 in a manner of gripping the latter. Accordingly, the deviation of the movable contact 7 from the rotatable screw shaft 3-to the left and right directions is prevented by both the guiding portions 19. That is, the two guiding portions 19 act to prevent the movable contact 7 from coming off the rotatable screw shaft 3 and to guide the former along the latter smoothly during the adjustment of the movable contact 7.

In this case, as shown in FIG. 11, the movable contact 7, the rotatable screw shaft 3 and the resistor board 6 have the following dynamical construction. That is to say, both the contact points 15 are symmetrically arranged at distances of a and a, which are approximately equal with each other, with respect to the center axis Y-Y which passes through the center of the rotatable screw shaft 3 and is perpendicular to the resistor board 6, so that the movable contact 7 is set at a stable position on the rotatable screw shaft 3 by forces F and F exerted on the contact points 15 causedby the resiliency (spring force) of the movable contact 7 itself and the guiding portions 19. As a result, the movable contact 7 can, slide'between the resistor portion Sand the rotatable screw shaft'3 without meandering to provide a stable control voltage, if there is no eccentricity in the rotatable screw shaft 3. In practice, a distance b between the center axis of the rotatable screw shaft 3 and the resistor board 6 is selected as small aspossible soas to make the contact points 15 stable as possible with respect to the resistor portion 5.

As described above, with this invention the movable contact is formed of the conductive plate with resiliency, which is bent, and at least one end of the movable contact is made to engage with the rotatable screw shaft to move the movable contact by the vrotatable screw shaftin contact ,with the resistor portion, so that with resistive material on the inner surface thereof,

said one wall further being provided with at least one electrical terminal connected to said resistive material;

a screw shaft longitudinally mounted in said housing and rotatably supported by said end walls, said screw shaft having threads and being made of conductive material;

a second electrical terminal disposed at one end of said screw shaft and in electrical contact therewith,

1 said second electrical terminal extending externally of said housing; and

a movable contact element positioned on said screw shaft and bidirectionally advanced along said screw shaft in accordance with the rotation thereof, said contact element being formed of a resilient conductive plate bent between end portions thereof to thereby form a contact portion which is resiliently urged into physical contact with said resistive material, one end of said movable contact element being bent into engagement with said screw shaft at an inclination in accordance with the thread angle of said screw threads and being formed of a V-shaped cutout, and the other end of said movable contact element having a pair of guiding portions formed integrally therewith which extend outwardly along said screw shaft so as to not engage with the screw threads but to be supported by said screw shaft by abutment therebetween. 2. A variable resistor device in accordance with claim 1 wherein said contact portion of said movable contact element is embossed to form a plurality of contact points which are in physical contact with said resistive material.

3. A variable resistor device in accordance with claim 1 wherein one end of said screw shaft is provided with a gear to receive a driving gear in meshing engagement therewith to thereby rotate said screw shaft.

Claims

1. A variable resistor device, comprising: a housing formed of walls including end walls, one of said walls being detachable and being provided with resistive material on the inner surface thereof, said one wall further being provided with at least one electrical terminal connected to said resistive material; a screw shaft longitudinally mounted in said housing and rotatably supported by said end walls, said screw shaft having threads and being made of conductive material; a second electrical terminal disposed at one end of said screw shaft and in electrical contact therewith, said second electrical terminal extending externally of said housing; and a movable contact element positioned on said screw shaft and bidirectionally advanced along said screw shaft in accordance with the rotation thereof, Said contact element being formed of a resilient conductive plate bent between end portions thereof to thereby form a contact portion which is resiliently urged into physical contact with said resistive material, one end of said movable contact element being bent into engagement with said screw shaft at an inclination in accordance with the thread angle of said screw threads and being formed of a Vshaped cutout, and the other end of said movable contact element having a pair of guiding portions formed integrally therewith which extend outwardly along said screw shaft so as to not engage with the screw threads but to be supported by said screw shaft by abutment therebetween.

2. A variable resistor device in accordance with claim 1 wherein said contact portion of said movable contact element is embossed to form a plurality of contact points which are in physical contact with said resistive material.