GB2178244A

GB2178244A - A variable capacitor incorporating a variable resistor

Info

Publication number: GB2178244A
Application number: GB08614629A
Authority: GB
Inventors: Yasufumi Ito
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1985-06-21
Filing date: 1986-06-16
Publication date: 1987-02-04
Also published as: KR870001217U; JPS624122U; GB8614629D0; KR890009402Y1; GB2178244B; JPH0427163Y2

Abstract

A variable capacitor incorporating a variable resistor comprises a slider support (5) equipped with sliders (5a and 5b), an element (4) having a resistor layer (4a and 4b) with which the sliders (5a and 5b) make sliding contact and a boxlike member (3) in which the element (4) is held. The variable capacitor (1) has a rotor shaft (1b) protruding from its front baseplate (1a), and the slider support (5) is mounted to the shaft (1b). The slider support (5) is disposed between the boxlike member (3) or the element (4) and the front baseplate (1a) of the capacitor (1). <IMAGE>

Description

SPECIFICATION Variable capacitor having variable reistor The present invention relates to a device in which a variable capacitor and a variable resistor are combined in one unit and which allows the capacitance of the capacitor and the resistance of the resistor to be varied by operation along a common axis.

Variable capacitors find main use as audio devices, such as radio receivers and cassette recorders with ratio receivers. As these audio devices are made in smaller sizes, the demand for higher packaging densities of components installed in products has become increasingly larger. This has led to a variable capacitor incorporating a variable resistor, which in turn has resulted in a structure where the slider support of a variable resistor is mounted on the rotor shaft of a variable capacitor, the variable resistor being mounted with a press fit to terminals protruding on the side of the protruding portion of the shaft.

Referring to Figs. 5 and 6, there is shown a conventional variable capacitor equipped with a variable resistor. The variable capacitor, indicated by numeral 1, is small in size, and uses film (not shown) as its dielectric substance.

The variable resistor, indicated by numeral 2, consists of a base 3, an element 4, and a slider support 5. A resistor layer 4a and an electric charge-collecting layer 4b are formed on the element 4. Sliders 5a and 5b which come into contact with the layers 4a and 4b, respectively, for inserting these layers into a closed electric circuit are formed on the support 5. A rotor shaft ib for rotating a rotor shaft (not shown) within the capacitor 1 and terminals 1c protrude from the upper side, as viewed in Fig. 5, of the front base plate 1a of the capacitor 1. The terminals 1 c act as poles for supporting a stator plate (not shown), and are electrically connected with the stator plate.

The variable resistor 2 shown in Fig. 5 has the base 3 which receives and holds the element 4. The base 3 has a receiving portion 3a into which the element 4 can be inserted, a hole 3b into which the rotor shaft 1b of the capacitor 1 can be loosely inserted, and terminal-receiving holes 3c through which the terminals ic can extend. The holes 3b and 3c are so arranged that their positions correspond to the positions of the rotor shaft 1 b and the terminals 1 c of the capacitor 1. The hole 3b into which the rotor shaft is inserted is formed at the centre of the base 3, or the centre of the receiving portion 3a. The four terminal-receiving holes 3c are formed at the fringe of the base 3. The holes 3c are so dimensioned that the terminals 1 c can be mounted into them with a press fit.After the terminals 1c have been mounted, they are retained at those positions by the frictional force developed between the terminals 1c and their holes 3c.

On the contact surface of the element 4, the resistor layer 4a is formed on the outer side, and the electric charge-collecting layer 4b is formed on the inner side. The element 4 has three terminals 4d attached thereto. The base of the element 4 which is on the inner side of the collecting layer 4b has a hole 4c into which the rotor shaft 1 b can be loosely inserted. The hole 4c is formed in a coaxial relation with the hole 3b in the base 3. The underside, as viewed in Fig. 5, of the slider support 5 has the sliders 5a and 5b. At the centre of this underside, another hole Sc into which the rotor shaft 1 b is inserted is formed.

The front end of the rotor shaft 1 b has a retaining portion 1d with which a dial (not shown) engages. The holes Sc are so shaped as to be capable of also engaging the retaining portion 1d. Therefore, the slider support 5 is able to rotate in step with the rotation of the dial that engages the rotor shaft 1 b of the capacitor 1.

As described above, in the conventional structure, the terminals 1 c which protrude from the variable capacitor 1 on the same side as the protruding portion of the rotor shaft 1b are fitted in the holes 3c in the base 3. The element 4 and the slider support 5 are mounted on the base 3. Thus, the variable resistor 2 and the variable capacitor 1 are combined in one unit. This conventional device has the following disadvantages. The contact surface of the element constituting the variable resistor is disposed on the opposite side of the base from the protruding portion of the rotor shaft of the variable capacitor, i.e., the contact surface faces outward and therefore when a soldering operation is performed, flux, soldering dust, ordinary dust, etc. adhere to the contact surfaces of the sliders which are formed on the slider support.Consequently, sliding motion is accompanied by noise, or a voltage skip takes place. If only a cover is added to prevent such an undesirable situation, then the number of components is increased, metal molds or other equipment for fabricating the cover is necessitated, and the structure becomes more expensive to manufacture. Accordingly, with the above-mentioned structure, it has not been possible to provide an inexpensive and reliable variable capacitor having a variable resistor.

According to the present invention there is provided a device comprising: a variable capacitor having a rotor shaft that protrudes from the front baseplate of the capacitor; a slider support mounted on the rotor shaft and having sliders; an element having a resistor layer with which the sliders of the slider support make sliding contact; and a boxlike member in which the element is held; the variable resistor being formed by the slider support, the element, and the boxlike member; the slider support being disposed between the boxlike member or the element and the front baseplate of the variable capacitor.

In one feature of the invention, the slider support is accommodated in a space that is formed by at least two of the elements, the boxlike member for the variable resistor, and the front baseplate of the variable capacitor.

Thus, novel parts such as a cover are not needed. When a soldering operation is carried out, there is no possibility that flux, soldering dust, ordinary dust, or the like adheres to the contact surfaces of the sliders rigidly attached to the slider support.

A variable capacitor incorporating a variable resistor will now be described by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 is an exploded perspective view of a variable capacitor which is equipped with a variable resistor and which constitutes a first example of the invention; Figure 2 is a cross-sectional view of main portions of the device shown in Fig. 1; Figure 3 is a cross-sectional view of main portions of a device constituting a second example of the invention; Figure 4 is a cross-sectional view of main portions of a device constituting a third example of the invention; Figure 5 is an exploded perspective view of a conventional structure; and Figure 6 is a cross-sectional view of main portions of the conventional structure shown in Fig. 5.

Referring to Figs. 1 and 2, there is shown a variable capacitor which is equipped with a variable resistor and which is manufactured in accordance with the invention. It is to be noted that like components are indicated by like reference numerals throughout all the figures, and they will not be described in detail below. The device shown in Figs. 1 and 2 comprises a small-sized variable capacitor 1 and a variable resistor 2. The resistor 2 is composed of a boxlike member 3, an element 4, and a slider support 5. A rotor shaft ib and terminals 1c protrude upwardly from the front base plate 1 a of the capacitor 1.

The variable resistor 2 consists of the three components. The boxlike member 3 has a concave receiving portion 3a into which the element 4 can be fitted, a hole 3b into which the rotor shaft 1 b of the capacitor 1 can be loosely inserted, holes 3c into which the terminals 1c can be fitted, and a fringe 3d for holding the element 4 at a certain height and for isolating the interior of the resistor 2 from the outside. The hole 3b into which the shaft is inserted is formed substantially at the centre of the receiving portion 3a. The four holes 3c are formed in the fringe 3d of the boxlike member 3. The holes 3c are so sized that the terminal 1c can be mounted into them with a press fit. Upon installation, the boxlike member 3 is held to the variable capacitor by the frictional force developed between the terminals ic and the holes 3c.

An outer resistor layer 4a and an inner electric charge-collecting layer 4b are formed on one outside of the element 4. The layers 4a and 4b have terminals 4d at their ends. A hole 4c into which the rotor shaft 1 b can be loosely inserted is formed on the inner side of the charge-collecting layer 4b in a coaxial relation with the hole 3b in the boxlike member 3. Sliders 5a and 5b which come into contact with the resistor layer 4a and the charge-collecting layer 4b, respectively, of the element 4 for inserting them into a closed electric circuit are rigidly fixed to the slider support 5. The support 5 is centrally provided with a hole Sc into which the rotor shaft 1 b is inserted.

The variable capacitor incorporating the variable resistor as mentioned above is assembled in the manner described below. First, on the side of the protruding portion of the rotor shaft Ib of the variable capacitor, the slider support 5 is mounted on the shaft 1 b while keeping the sliders 5a and 5b on the upper side. Then, the terminals 1c are forced into the holes 3c in the boxlike member 3 where the element is held such that the resistor layer 4a and the charge-collecting layer 4b face downward. Thus, the variable resistor 3 is firmly secured to the capacitor 1. By assembling the device in this way, the element 4 and the slider support 5 are accommodated in the sapce 6 that is surrounded by both the fringe 3d of the boxlike member 3 and the front baseplate 1 a of the capacitor 1.Hence, novel parts such as a cover are not required. Further, it is unlikely that when a soldering operation is effected, flux, soldering dust, ordinary dust, or the like adheres to the contact surfaces of the sliders 5a and 5b on the slider support 5.

Referring next to Fig. 3, there is shown another device according to the invention.

This device is similar to the device already described in connection with Figs. 1 and 2, except that the slider support 5 is disposed between the element 4 and a boxlike member 3'.

Referring to Fig. 4, there is shown a further device according to the invention. This device is similar to the device already described in connection with Figs. 1 and 2, except that the slider support 5 is disposed between the element 4 and the front baseplate 1a of the capacitor 1 having the fringe 1e integral with it.

As described thus far, the slider support constituting the variable resistor is accommodated in the space formed by the boxlike member or the element and also by the front baseplate of the variable capacitor. This dispenses with additional members such as a cover. In addition, when a soldering operation is performed, flux, soldering dust, ordinary dust, or the like does not adhere to the con tact surfaces of the sliders which are securely attached to the slider support. In this manner, the invention yields a variable capacitor having a variable resistor that is economical to manufacture and whose quality varies little from product to product.

Claims

1. A variable capacitor having a variable resistor, comprising: the variable capacitor having a rotor shaft that protrudes from the front baseplate of the capacitor; a slider support mounted on the rotor shaft of the variable capacitor and having sliders; an element having a resistor layer with which the sliders of the slider support make sliding contact; and a boxlike member in which the element is held; the variable capacitor being formed by the slider support, the element, and the boxlike member; the slider support being disposed between the boxlike member or the element and the front baseplate of the variable capacitor.

2. A variable capacitor having a variable resistor as set forth in Claim 1, wherein the front baseplate of the variable capacitor and the boxlike member of the variable resistor are formed integrally.

3. A variable capacitor having a variable resistor according to Claim 1, or to Claim 2 wherein the resistor layer on the element faces toward the front baseplate of the capacitor.

4. A variable capacitor incorporating a variable resistor substantially as hereinbefore described with reference to Figs. 1 to 4 of the accompanying drawings.