GB2166905A

GB2166905A - Variable rotary capacitor

Info

Publication number: GB2166905A
Application number: GB08522919A
Authority: GB
Inventors: Yasufumi Ito
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1984-11-13
Filing date: 1985-09-17
Publication date: 1986-05-14
Also published as: GB8522919D0; KR860006690U; GB2166905B; JPS6186921U; KR890007222Y1; JPH0419790Y2

Abstract

A small-sized variable capacitor having insulating members (20) each of which substantially conforms to the contour of a free part (B) of each stator plate (1) and bears on the free part (B). One end of each insulating member (20) and stator plate (1) is held between poles (19a, 18a) mounted to the baseplates (18, 19) of the capacitor, whereby the stator plates (1) are prevented from vibrating. <IMAGE>

Description

SPECIFICATION Variable capacitors FIELD OF THE INVENTION The present invention relates to a small-sized variable capacitor and, more particularly, to a small-sized variable capacitor adapted for small-sized radio receivers, radio cassette recorders, and other similar devices.

BACKGROUND OF THE INVENTION A conventional small-sized variable capacitor is shown in Figs. 3 and 4. This capacitor includes stator plates 1 that are coated with dielectric 1 A. Washers 2 are disposed alternately with the stator plates 1. These plates 1 and washers 2 form one group 3 of stators.

Other groups 4, 5, 6 of stators have the same structure as the stator group 3. Rotor plates 7 are disposed alternately with the washers 8. A rotor shaft 9 is provided with a threaded portion 9A at its front end. The plates 7 extend through the shaft 9, and a nut 10 is meshed with the threaded portion 9A such that the plates 7 are firmly held. Rotor sections 11, 12, 13, 14 correspond to the stator groups 3, 4, 5, 6. A front baseplate 15 has poles 15a, 15b, and a bearing 15c. The poles 15a and 15b separately support the stator groups 3-6. The shaft 9 extends through the bearing 15c. A rear baseplate 16 has poles 1 6a and 1 6b corresponding to the front baseplate 15, as well as a hole 16c for the support of the shaft 9. The rotor shaft 9 and the stator groups 3-6 are held between the front baseplate 15 and the rear baseplate 16.

In assembling these components, the poles 16a and 16b are inserted from the side of the rear baseplate 16. Then, the stator groups 3-6 are inserted. Finally, metal terminals 17 are forced into the poles 15a and 15b of the front baseplate 15.

In the prior art device described above, the stator groups are cantilevered at each support portion A, and therefore it has the disadvantage that its free end B readily vibrates. More specifically, it is assumed that this small-sized variable capacitor is mounted in a radio receiver (not shown), for example, and that it is installed in a cabinet together with a loudspeaker. When the volume of the radio receiver is made large as often encountered with high-output radio receivers that have recently enjoyed wide acceptance, the vibration of the speaker is transmitted to the smallsized variable capacitor via the cabinet. Consequently, the free end B of each stator group resonates within the audible frequency range.

This sometimes causes a howl of the speaker, which is offensive to the ear.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small-sized variable capacitor which is free of the foregoing disadvantages with the prior art device, and which is especially adapted for small-sized radio receivers, radio cassette recorders, and other similar devices.

The above object is achieved in accordance with the teachings of the invention by a smallsized variable capacitor having a pair of baseplates disposed opposite to each other, a rotor shaft disposed between the baseplates so as to be rotatable, rotor plates firmly secured to the shaft and each made of a metal sheet, poles mounted to the baseplates, and stator plates each made of a metal sheet and coated with dielectric, the stator plates being opposite to, and slightly spaced from, the rotor plates, one end of each stator plate being fixed, the capacitor being characterized in that an insulating member is provided which substantially conforms to the contour of the free end of each of said stator plates and bears on the free end, and that one end of the insulating member is held between the poles mounted to the baseplates.

Other objects and features of the invention will become more readily apparent from the ensuing specification and claims when taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinal cross section of a small-sized variable capacitor according to the present invention; Figure 2 is an exploded perspective view of a stator plate and an insulating member that are main components of the capacitor shown in Fig. 1; Figure 3 is a longitudinal cross section of a conventional small-sized variable capacitor; Figure 4 is a fragmentary, exploded perspective view of the capacitor shown in Fig. 3; Figures 5 and 6 are perspective views of other examples of said insulating member.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figs. 1 and 2, there is shown a small-sized variable capacitor embodying the concept of the present invention. It is to be noted that like parts are denoted by like reference numerals throughout all the figures. The capacitor shown in Figs. 1 and 2 have stator groups 3, 4, 5, 6, rotor plates 7, washers 8, rotor shaft 9, and nut 10 which are similar in structure and arrangement to their corresponding components of the aforementioned prior art device and so these components will not be described in detail below. Poles 18a and 1 8b for separately supporting the stator groups 3-6 and a bearing 18c through which the rotor shaft 9 extends are mounted to a front baseplate 18.A rear baseplate 19 has poles 1 9a and 1 9b corresponding to the front baseplate 18, and is also provided with a hole 19c for the support of the shaft 9. Besides the poles 18a, 18b, 19a, 19b, two other poles (not shown) are mounted. An insulating member 20 substantially conforms to the contour of the free end B of each stator plate 1 already mentioned and bears on the free end.

One end of the insulating member 20 is held between the front baseplate 18 and the rear baseplate 19 in the same way as the rotor shaft 9 and the stator groups 3-6. These components are assembled in the same fashion as in the aforementioned prior art device.

That is, the poles 19a and 19b are inserted from the side of the rear baseplate 19, placing the insulating member 20 in such a way that one of the poles is inserted into a support hole 20a formed in one end of the insulating member 20, the stator groups 3-6 are in inserted, and finally the metal terminals 17 are urged into the poles 1 8a and 1 8b of the front baseplate 18. In this example, the pole 1 9a of the rear baseplate 19 is made shorter than the pole 16a of the rear baseplate 16 (Fig. 3) of the prior art device by a length equal to the thickness of the insulating member 20 so that the insulating member can be sandwiched.

The insulating member 20 and the dielectric extending out from the outer periphery of each stator plate 1 are welded together by applying heat. Thus, in substance, all the welded stator plates bear on the insulating member 20, in addition to the stator plates 1 that are in abutment with the insulating member 20.

Figs. 5 and 6 are fragmentary perspective views of other examples of the invention.

These examples are similar to the above example except for the shape of the insulating member 20.

As thus far described, the present invention provides a small-sized variable capacitor having a pair af baseplates disposed opposite to each other, a rotor shaft disposed between the baseplates so as to be rotatable, rotor plates firmly secured to the shaft and each made of a metal sheet, poles mounted to the baseplates, and stator plates each made of a metal sheet and coated with dielectric, the stator plates being opposite to, and slightly spaced from, the rotor plates, one end of each stator plate being fixed, the capacitor being characterized in that an insulating member is provided which substantially conforms to the contour of the free end of each of said stator plates and bears on the free end, and that one end of the insulating member is held between the poles mounted to the baseplates.

Thus, even if vibration of a loudspeaker installed in a radio receiver is transmitted to the small-sized variable capacitor via the cabinet, the free end of each stator plate in the aforementioned prior art device will not resonate.

This prevents howl of the speaker. Hence, a small-sized variable capacitor is provided which is much superior in performance to the prior art device.

Claims

1. In a variable capacitor having a pair of baseplates disposed opposite to each other, a rotor shaft disposed between the baseplates so as to be rotatable, rotor plates firmly secured to the shaft and each made of a metal sheet, poles mounted to the baseplates, and stator plates each made of a metal sheet and coated with dielectric, the stator being opposite to, and slightly spaced from, the rotor plates, one end of each stator plate being fixed, the improvement wherein an insulating member is provided which substantially conforms to the contour of the free end of each of said plates and bears on the free end, and wherein one end of the insulating member is held between the poles mounted to the baseplates.

2. In a variable capacitor as set forth in claim 1, the further improvement wherein the length of one of the baseplates is so determined that one end of the insulating member can be held between the baseplates.

3. In a variable capacitor as set forth in claim 1, the further improvement wherein the insulating member and the dielectric on the stator plates are welded together.

4. A variable capacitor substantially as hereinbefore described, with reference to Figs.

1, 2, 5 and 6 of the accompanying drawings.