Electronic Tuning Element Assembly

The present invention relates to a variable resistor and switch assembly constituting in combination an electronic tuning element assembly.

It is popular in the present art to employ in television receivers a system known as electronic or voltage responsive tuning, in which a variable capacitance diode or varactor is utilized for varying the resonant frequency of a tuning circuit. Tuning is accomplished by varying a tuning voltage applied to the varactor, generally by means of a potentiometer or variable resistor. A varactor resonant circuit is generally provided for each channel which is to be received by the television receiver, and channel selection is accomplished by push buttons or the like without the need for tuning once the varactor resonant circuits are preset.

Commercial broadcast television is generally divided into three bands, a low VHF band, a high VHF band and a UHF band. Each varactor resonant circuit must therefore comprise in addition to the variable tuning resistor a band selector switch to select the required one of the three bands. It is also desirable to provide the variable tuning resistor with an indicator to indicate the tuning frequency.

The present invention is an improvement to this type of tuning assembly as disclosed in U.S. Pat. Nos. 3,624,582 and 3,694,602 to Sadayoshi Iwasaki, Specifically the present invention provides, in addition to a variable tuning resistor assembly disclosed in the above patents, the combination therewith of a band switch and an improved indicator assembly. The above patents further teach the construction of an enabling switch for the variable tuning resistor and an AFC switch which are not the subject matter of the present invention.

It is therefore an important object of the present invention to provide an electronic tuning element assembly comprising, in combination, a variable tuning resistor, a band switch and an improved tuning indicator.

The above and other objects, features and advantages of the present invention will become clear from the following detailed description taken with the accompanying drawings, in which:

FIG. 1 is a perspective view of an electronic tuning element assembly embodying the present invention;

FIG. 2 is an exploded view of the tuning element assembly;

FIGS. 3a, 3b and 3c are schematic views of a rotary band switch constituting an integral part of the tuning element assembly;

FIGS. 4a, 4b, 4c and 4d show a tuning indicator constituting an integral part of the tuning element assembly;

FIG. 5 is a fragmentary longitudinal sectional view of a variable tuning resistor constituting an integral part of the tuning element assembly;

FIG. 6 is a sectional elevation of part of the switch shown in FIG. 3;

FIG. 7 is a schematic view of a knob of the switch shown in FIG. 3;

FIG. 8 is a side view of a fixed contact of the switch shown in FIG. 3;

FIG. 9 is a side view of a member of the body of the switch shown in FIG. 3;

FIG. 10 is a top view of part of a slider of the variable tuning resistor shown in FIG. 5; and

FIG. 11 is a view of another part of the slider shown in FIG. 5.

Referring to FIGS. 1 and 2, the tuning element assembly comprises a variable resistor section A, a tuning indicator section B, a rotary band switch section C and a control member section D. The variable resistor section A comprises a casing 1 which rotatably supports a shaft 2. The shaft 2 is threaded at 2a. The variable resistor section A has an insulating plate 3 which is fixed to the casing 1 by a base plate 4 which is provided with ears 4a. The casing 1 is formed at its top with a longitudinal slot 1a.

Referring also to FIG. 5, the variable resistor section A further comprises a contact member or slider 5 which is in ohmic engagement with a linear resistance element 3a formed on the insulating plate 3 and a connecting member 8 which is connected to the slider 5 and extends external of the casing 1 through the slot 1a. The slider 5 screwably engages with the threaded portion 2a of the shaft 2 so that rotation of the shaft 2 causes linear movement of the slider 5 left and right as viewed in FIG. 5. The ends of the resistance element 3a are connected to contacts 6a and 6b respectively. The slider 5 is in ohmic connection with a contact 7 through the shaft 2 which is in rotating sliding ohmic engagement with the contact 7. The contacts 6a and 6b are connected to a voltage source (not shown) and the contact 7 is the tuning voltage output for the varactor resonant circuit (not shown).

As shown in FIG. 10, the slider 5 is formed with ears 5a which ohmically mesh with the threaded portion 2a of the shaft 2 for driving the slider 5. Projections 5b are formed on the slider 5 which also engage with the shaft 2 to provide a guiding function. Notches 5c are cut in the sides of the slider 5 in which fit legs 8a of the connecting member 8 (see FIG. 11). In this manner, the connecting member 8 is connected to the slider 5 for integral linear movement therewith.

The indicator section B comprises, as shown in FIG. 4, a guide member 10 which has legs 10d and a step 10e for detachable connection to the casing 1 and the switch section C, a perpendicular portion 10f which is oriented perpendicular to the shaft 2 and a parallel portion 10g extending parallel to the shaft 2 from the perpendicular portion 10f. A flexible polyester ribbon 9 is connected at one end to the connecting member 8 by means of a hole 9b through which the connecting member 8 extends. Linear movement of the slider 5 causes the end of the ribbon 9 to move therewith parallel to the shaft 2.

The ribbon 9 is guided by the portions 10f and 10g of the guide member 10 in directions perpendicular and parallel to the shaft 2 as shown in FIG. 4b. The guide member 10 is formed with a horizontal window 10a through which the ribbon 9 is visible.

The ribbon 9 is formed with a marking such as a slot 9a which obliquely extends along the length of the ribbon 9. As the ribbon 9 is moved as shown by an arrow in FIG. 4b, the part of the slot 9a visible through the window 10a moves from one side of the window 10a toward the other. This provides an indication of the position of the slider 5 and thereby the tuning voltage and frequency.

The guide member 10 is further provided with curved guide plates 10c and a guide bar 10b to guide the ribbon 9. It will be noticed that the direction of the ribbon 9 is reversed by 180.degree. by the guide member 10 resulting in a compact configuration. Although not shown, graduations may be provided on the perpendicular portion 10f along the window 10a to provide a quantitative indication of the position of the slider 5.

The switch section C includes, as viewed in FIG. 3, a terminal support plate formed of an electrically insulating material and having a central aperture 11a through which the shaft 2 coaxially extends. Three recesses are provided in the terminal support plate 11 below the opening 11a so as to receive corresponding fixed terminals 12a, 12b and 12c therein, each of the recesses having the same configuration as that of the corresponding terminal and a depth equal to the thickness of the terminal. The terminals 12a, 12b and 12c are fixedly held in place in the corresponding recesses through engagement with corresponding projections which are all designated as 11b and are integral with the support plate 11.

The switch section C also includes a common terminal 13 which has a contact portion 13a formed with three rectangular apertures 13b and is fixedly received in a recess in the terminal support plate 11 through projections 11b, the recess having the same configuration as that of the common terminal 13. A central bend 13d of the common terminal 13 (see FIG. 8) extends to the rear of the terminal support plate 11 (see FIGS. 3 and 9) via a notch 11f defined between two projections 11e provided at one laterial edge of the terminal support plate 11, the bend 13d being contiguous with an external terminal portion 13c.

A switch housing 14 has an end wall 14a and side walls 14c. The end wall 14a is formed at the center thereof with an aperture 14b through which the shaft 2 coaxially extends while four inwardly projecting retainers 14d are provided at the upper and lower corners of the side walls 14c. The terminal support plate 11 is fixed to the housing 14 with shoulders 11d thereof retained by the corresponding retainers 14d mentioned above. Further designated by the reference numeral 14e is a bottom wall of the housing 14.

As viewed in FIG. 6, a movable member 15 is rotatably mounted in the housing 14 by a cylinder 15c thereof slidable in the aperture 14b of the housing 14. The movable member 15 is provided with another cylinder 15b which is rotatably slidable in the central aperture 11a of the terminal support plate 11. The cylinders 15b and 15c are commonly hollow so that the shaft 2 extends through a bore 15f thereof. A substantially rectangular member 15a is integrally provided to the movable member 15 so as to support an elongated movable contact wound thereround and consisting of a metal wire as will be described below. The aforementioned cylinders 15b and 15c project in opposite directions from the center of the member 15a in alignment with each other.

Reference numerals 15d and 15e designate a band indicator of the movable member 15 and projections retaining the contact 16 to the movable member 15, respectively.

The movable contact 16 thus fixed to the member 15 which in turn is rotatably mounted in the housing 14 is so shaped as to include an angular top or first contact 16a and a curved bottom or second contact 16b where opposite ends of the contact 16 overlap. With this arrangement, the first contact 16a moves along an arcuate path in contact with the contact portion 13a of the common terminal 13 when a control member or knob 17 (described below) is rotated whereas the second contact 16b engages with one of the contacts 12a, 12b or 12c to connect the common terminal 13 to the desired contact 12a, 12b or 12c.

The rectangular apertures 13b formed in the common terminal 13 releasably retain the first contact 16a to provide a detent function.

The control member section D will hereinafter be explained in detail with FIGS. 2 and 7. Reference numeral 17 designates the electrically insulated control knob associated with the switch section C and which has the outer periphery thereof knurled throughout its length. The knob 17 includes an extension 17a having an annular cross-section and a bottom wall 17b which is formed with an opening 17c for passing the shaft 2 therethrough and a pair of sectorial openings 17d for retainably receiving extensions 15c' of the cylinder 15c of the movable member 15 which have a conjugate cross-section. The sectorial openings 17d diametrically oppose each other and are contiguous with the opening 17c. Cutouts 15c" of the cylinder 15c, on the other hand, abut against corresponding peripheral portions 17e adjacent to the openings 17d and, therefore, serve as a stopper. The shaft 2 is freely rotatable while the movable member 15 is moved only when the knob 17 is rotated.

A knob 18 is provided to hold a knurled external end 2b of the shaft 2 in strong retaining engagement with inner periphery of a hollow cylinder 18a. The knob 18 when manipulated for rotation linearly moves the slider 5 and thereby the ribbon 9, and the knob 17 is rotated to control the switch section C in the manner described hereinabove.

The movable member 15 included in the switch section C has its indicator 15d rotatably disposed between the support plate 11 and the housing 14. The indicator 15d is movable in an arcuate path defined above and along curved tops of the plate 11 and the housing 14.

As has thus far been described, according to the present invention, the variable resistor section A and the indicator section B operable by the resistor section A are controlled by the knob 18 and the switch section C by the knob 17. The integral assembly of the sections A and C and the arrangement of the two different knobs 17 and 18 at a common location readily facilitate the band selection and tuning of the television receiver. Also, the television set can be made compact in size with a minimum space required for installation.

Various other advantages of the present tuning element assembly are embodied in the switch section C. The terminals 12a, 12b, 12c and 13 which would conventionally be secured by caulking or the like are, according to the invention, fixed in recesses of the terminal support plate 11 having configurations corresponding to the terminals with the aid of the projections 11b. The projections 11b engaging with the terminals 12a, 12b and 12c correspond in position to the roots of the soldering portions of the terminals, thus preventing flexation. The second contact 16b of the movable contact 16 remains in sliding contact with the flat surfaces of the terminals 12a, 12b and 12c while the first contact 16a slidingly moves on the flat contact portion 13a of the common terminal 13 which is formed with the rectangular apertures 13b. These apertures 13b provide a detent function as described above. Thus, various independent functions are integrated into the switch section C which has a simple construction and can be easily manipulated. Also, the knob 18 serves to detachably retain the sections A, B, C and D together thereby facilitating easy manufacturing, assembly and servicing.

It should be noted that while there has been herein shown and described a preferred embodiment of the present invention, such has been done for purposes of illustration only, and that various changes and modifications may be made within the scope of the appended claims. For example, the knob 17 provided to the switch section C may omitted if the indicator 15d is elongated to a substantial length to serve as a switching lever.