GB2174545A - Variable condenser structure - Google Patents

Abstract

A variable condenser has its capacity varied by varying the facing areas of mating rotor and stator plates when the rotor plates are turned relative to the stator plates (1) through a rotor shaft (9). A supporting member (18) made of a resilient material is snap fitted and fixed between two adjacent posts (15a) of paired base plates (15) after assemblage of the structure such that its portion (18a) is urged into contact with the free edges of the stator plates (1) so that it can prevent any vibration of the stator plates (1). <IMAGE>

Description

SPECIFICATION Variable condenser structure The present invention relates to a variable condenser and, more particularly, to a variable condenser which has its capacity varied with the variation of the opposing areas of stator plates covered with dielectricfilms and rotor plates made rotatable.

The condenser of this kind is used in a small sized radio receiver, a radio cassette tape recorder for example.

It is, an object of the present invention to provide an improved variable condenser which is enabled to prevent the howling phenomena all over the capacity range reliably by a simple construction.

In order to achieve this object, the present invention is characterized in that a supporting member made of an elastic material is fitted and fixed between two adjacent posts, after the variable condenser has been assembled, such that its portion is held in elastic contact with the side portions of stator plates so that it can prevent the vibrations of the stator plates.

Variable condensor embodying the invention will now be described, by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic top plan view showing the essential portion of the variable condenser according to one embodiment of the present invention; Figure 2 is a perspective view showing the exterior of the supporting member of Figure 1; Figure 3 is an explanatory view showing the mounted state of that supporting member; Figure 4 is a sectional view showing one example of the variable condenser of the prior art; Figure 5 is a top plan view showing the relationships among the stator plates, washers and rotor plates which are mounted in that variable condenser; and Figure 6 is a section taken along line A-A of Figure 5.

Before entering into detailed description of the present invention, cursory review will be made on one example of the variable condenser of the prior art with reference to Figures 4 to 6.

Figure 4 is a sectional view showing the variable condenser of that kind of the prior art; Figure 5 is a top plan view showing the relationships among rotor plates, washers and stator plates of the variable condenser; and Figure 6 is a section taken along line A-A of Figure 5. In these Figures, reference numeral 1 indicates stator plates, and numeral 2 indicates washers which are arranged alternately of the stator plates 1. These plates are laminated in plurality to form one stator group 3 together. Each of the aforementioned stator plates 1 is a composite which has a generally sector-shaped metal foil 1 a covered with a dielectric film 1 b of polyethylene or the like. Moreover, numerals 4, 5 and 6 indicate other stator groups which have structures similar to that of the aforementioned stator group 3.

Indicated at numeral 7 are generally sector-shaped rotor plates which are arranged alternately of washers 8 and which are fitted in a rotor shaft 9 having a threaded portion 9a at its leading end.

Those rotors and washers 7 and 8 are fixed on the rotor shaft 9 by fastening a nut 10 on the aforemen tionedthreaded portion 9a. Numerals 11,12,13 and 14 indicate rotor sections which correspond to the aforementioned stator groups 3, 4, 5 and 6, respectively.

Indicated at numeral 15 is a front base plate which is constructed of: posts 15a supporting the respective stator groups 3,4,5 and 6 separately of one another; and a bearing portion 15b bearing the aforementioned rotor shaft 9 therein. Indicated at numeral 16 is a rear base plate which is constructed of: posts 1 6a corresponding to the front base plate 15; and a hole 16a bearing the rotor shaft 9.

This rotor shaft 9 is held between those front and rear base plates 15 and 16 such that it is held rotatably between the bearing the bearing portion 15b and hole 16b of the two base plates 15 and 16.

On the other hand, the aforementioned respective stator groups 3,4,5 and 6 are clamped by the respective posts 15a and 16a ofthetwo base plates 15 and 16 and are fixed thereto by press-fitting metallic terminals 17 in the posts 16a, the stator groups 3,4,5 and 6 and the posts 15a in the order recited.

Here, in case the small sized variable condenser thus constructed is built in a radio receiver having a relatively large-sized speaker built therein, the vibrations of the speaker having a high output will possibly induce the vibrations of the free ends of the stator plates 1 to invite the howling (i.e, abnormal oscillations). In the above-specified structure of the prior art, therefore, a semi-circular notch 1 c formed at the leading end of the dielectric film 1 b, a semi-circular mounting base 7a formed at the fixed end of the rotor plate 7, and the aforementioned washer 8 are set to have substantially equal radii of curvature so that the vibrations at the freed end of the stator plate 1 may be prevented by having said notch 1 c and the circumference of the washer 8 abutting against each other.

With this construction, in case the rotor plate 7 and the stator plate 1 are opposed to each other over a wide area, the stator plate 1 has its free end entering into the clearance between the facing rotor plates 7 so that its vibrations can be prevented by the rotor plates 7. In case, however, the rotor plates 7 are turned out of the stator plate 1 so as to reduce the capacitor, as shown in Figure 5, they fail to sufficiently regulate the stator plate 1. As a result, the free end of the stator plate 1 vibrates in the axial directions of the rotor shaft 9 to cause a defect that the aforementioned howling is invited.

The present invention will be described in the following in connection with one embodiment thereof with reference to the accompanying drawing.

Figure lisa schematic top plan view showing an essential portion of the variable condenser according to the embodiment of the present invention.

Reference numeral 18 indicates a supporting member, and the parts corresponding to those of Figures 4to 6 are indicated at the same reference characters.

As shown in Figure 1, the supporting member 18 is made of a synthetic resin material and is fitted and fixed between the two adjacent posts 15a of the front base plate 15 such that a projection 1 8a formed integrally with said supporting member 18 is urged into contact with the side portions of the stator plates 1. As shown in perspective view in Figure 2, this supporting member 18 has arcuate portions 18b and 18c at its two ends and is formed integrally with the aforementioned projection 18a, which is located in the vicinity of one arcuate portion 18b, and a stepped-down portion 18d which is located in the vicinity of the other arcuate portion 18c.The peripheries of those arcuate portion 18b and 18c are made to have curvatures substantially equal to that ofthe posts 15a (or 16a), and one arcuate portion 18b and a portion of the projection 18a near the former merged into each other to define one circumference. The aforementioned projection 1 8a is hollowed at its centre to have a frame shape so as to have a sufficient elastic deformation and has a thickness set larger than the height of the corresponding stator group 3.

Next,the method of mounting the supporting member 18 thus constructed will be described with reference to Figure 3.

First of all, the assembly of all the variable condenser components other than the supporting member 18 is completed, and then one arcuate portion 1 8c of the supporting member 18 is fitted on one post 15a, as shown in Figure 3, whereas the vicinity of the other arcuate portion 18b is depressed in the direction of arrow. Then, the sufficiently elastic projection 18a is forced toward the stator plates 1 while being deformed in abutment against the circumference of that post 15a until it is allowed to restore its original shape (i.e., the shape in which the projection 18a merges into the arcuate portion 18b to have the curved periphery shared with the post 15 a) by its own elastic force. As a result, the arcuate portion 1 8b is fitted on the other post 15a.When the supporting member 18 is thus fitted and fixed between the two posts 15a, as shown in Figure 1, the stepped-down portion 18d comes into contact with the lower face of the lowermost stator plate 1 until the projection 18a is held in elastic contact with the respective side portions of the stator plates 1. As a result, the individual stator plates 1 are supported near their free ends by the supporting member 18 through the projection 18a so that they can be prevented from any vibration in case the rotor shaft 9 is turned not only in the direction to increase the capacity but also in the direction to bring the rotor plates out of the stator plates.

Since the supporting member 18 is formed with the projection 18a merging into one arcuate portion 18b in accordance with this embodiment, it can be snapped into the space between the two posts 15a by making use of the righting moment of said projection 1 8a thereby to simplify its mounting work.

Incidentally, the foregoing embodiment has been described as to the case in which the stator group 3 is elastically supported by the supporting member 18. If necessary, however, a similar supporting member can be used with another stator group to prevent the vibrations of the same.

Moreover, the projection 18a held in elastic contact with the side portions of the stator plates 1 should not have its shape limited to that of the aforementioned embodiment but can be replaced by a tongue-shaped member, for example As has been described hereinbefore, according to the present invention, the stator plates can be prevented from any vibration by the elastic force of the supporting member which is fitted between the two adjacent posts. As a result, the howling phenomena all over the capacity range can be prevented by the remarkably simple structure to provide the variable condenser which is freed from the aforementioned defect of the prior art to have an excellent function.

Claims (7)

1. Variable condenser structure comprising: a pair of base plates each having an equal number of posts and opposed to each other through said posts; a rotor shaft borne rotatably between said base plates; a plurality of rotor plates fitted in and supported by said rotor shaft at a predetermined spacing inbetween; and a plurality of stator plates each having its one end fixed on corresponding one of said posts so that the opposing areas of said rotor plates and said stator plates can be varied when said rotor plates are turned relative to said stator plates through said rotor shaft, wherein the improvement comprises a supporting member made of an elastic material and having its two ends arcuated and sized to be snapped between and fitted on adjacent two of said posts such that its portion is held in elastic contact with the outer sides of said stator plates.

2. A variable condenser structure according to Claim 1, wherein each of said stator plates is covered with a dielectric film.

3. A variable condenser structure according to Claim 1, or to Claim 2 wherein the portion of said supporting member is hollowed at its centre to have a frame shape and projects integrally from a vicinity of one of said arcuated ends thereof to have its free end supporting he outer sides of said stator plates elastically.

4. Avariable condenser structure according to any one of Claims 1 to 3, wherein said stator plates are grouped to form a plurality of stator groups so that said supporting member may contact with the outer sides of the stator plates of one of said stator groups.

5. A variable condenser structure according to claim 4, wherein said supporting member contacts with the outer sides of the stator plates of the remaining one or ones of said stator groups.

6. A variable condenser structure according to any preceeding Claim, wherein the portion of said supporting member is formed into a tongue having its free end supporting the outer sides of said stator plates elastically.

7. A variable condensor structure substantially as hereinbefore described, with reference to Figures 1 to 3 of the accompanying drawings.