US2679596A - Television station selector - Google Patents

Description

A. W. FRANKLIN TELEVISION STATION SELECTOR May 25, 1954 5 Sheets-Sheet 1 Filed Aug. 21, 1948 INVENTOR ALBERT W. FRANKLIN Q ATT RNEYZLZ May 25, 954 A. w. FRANKLIN 2,679,596 TELEVISION STATION SELECTOR Filed Aug. 21, 1948 3 Sheets-Sheet 2 INVENTOR ALBERT W. FRANKLIN ATTO R N EYS -Y 25, 1954 A. w. FRANKLIN 2,679,596

TELEVISION STATION SELECTOR Filed Aug. 21, 1948 ssheets-sneet s Tici. S-

INVENTOR ALBERT W. FRANKLEN Patented May 25, 1954 UNITED STATES FATENT OFFICE TELEVISION STATION SELECTOR Albert W. Franklin, New York, N. Y.

Application August 21, 1948, Serial No. 45,473

3 Claims. 1

This invention relates to improvements in selector switches and associated circuits by means of which electrical apparatus and particularly short. wave high frequency apparatus such as television receivers may be tuned.

An object of this invention is to provide an improved form of switching means and associated circuits for selectively tuning a multichannel television receiver to any one of a number of desired predetermined channels.

A more specific object of the invention is to provide a station selector such as the above in the form of a push button mechanism.

Another object of the invention is to provide a station selector such as the above in the form of a rotary switch.

A more detailed object of the invention is to provide an improved novel form of high frequency transmission circuit for electrical apparatus such as a television receiver and manual means for selectively tuning that circuit to a plurality of different frequencies.

Still another object of the invention is to provide in a radio apparatus of this type a novel form of high frequency circuit simultaneously formed and attached to a supporting panel by stamping it from a metal sheet superposed on said panel.

A still more specific object of the invention is the provision of inductances associated with such a circuit and similarly made.

A broader object of the invention is the provision of high frequency transmission circuits for apparatus of this type in such form as to adapt them to mass reproduction while maintaining the necessary rigid electrical tolerances required.

A still more specific object of the invention is the provision of novel ground circuits for such transmission circuits and/or switching means for selectively connecting predetermined frequency points of said circuit to ground to complete it and thereby tune the equipment to a desired.

frequency channel.

Other and more detailed objects of the invention will be apparent from the following description of several embodiments thereof as illustrated in the attached drawings.

In the accompanying drawings- Figure 1 is a top plan view of one physical embodiment of the subject matter of this invention as employed in a push button actuated frequency selector;

Figure 2 is a bottom plan view of a portion of the mechanism of Figure 1;

Figure 3 is a cross sectional view taken on the line 3-3 of Figure 2;

Figure 4 is a cross sectional view taken on the line il of Figure 3;

Figure 5 is a side elevational view of the embodiment of the invention in a rotary switch;

Figure 6 is a view of the device from the plane 3-5 as indicated in Figure 5;

Figure I is a plan view from the plane 'i'--l as indicated in Figure 5;

Figure 8 is. a detailed cross sectional view showing the switch rotor and operating shaft;

Figure 9 is a plan view of the stator plate of the oscillator trimmer condenser; and

Figure 10 is a similar view of the rotor of the oscillator trimmer condenser.

The subject matter of this invention will be explained in connection with the control mech anism for a television receiver but those skilled in the art will recognize that much of the subject matter herein disclosed is applicable to other electrical circuits and particularly very high frequency circuits.

Continuing reference, for disclosure purposes, to television receivers, one of the chief components thereof is the station selector which should be of such construction as to permit reproduceability within the required close limits in the values of inductance, resistance and capacity. The present methods of constructing apparatus of this type are not adapted to uniformity in mass production methods because of the difficulty of maintaining these values within the close tolerances required.

Most commonly today, the apparatus is adapted for operation at the various television channel frequencies by the use, among other things, of wound inductances, each being tuned to the individual frequency of the associated channel. Those skilled in the art appreciate the extreme difiiculty of attaining the required inductive values with wire wound inductances. Much difficulty is encountered in maintaining the required close inductance tolerance in mass producing equipment of this type. Indeed, it is safe to say that it is almost impossible to maintain uniformity in production so that each set requires individual adjustment, greatly increasing the cost of production.

Additionally, equipment of this type is particularly vulnerable to changes in temperature, humidity, relative position of parts with respect to each other and other variable conditions dilicult to control. By means of the novel subject values are held within their close limits.

signing the transmission line allowance can be 3 matter herein disclosed, all of these difiiculties are easily overcome.

As illustrated in the drawings, the subject matter of this invention has been exemplified by application of two types of channel selectors, one employing push buttons and the other a rotary switch of the type generally employed at the present time in television receivers. In the push button type, as illustrated, three transmission lines (more may be used if necessary) are simultaneously formed and attached to an insulating panel by shearing or cutting them from a sheet of metal superposed on the support. These transmission lines may be attached by the clinching action resulting from stamping them from the metal sheet but when required additional attachment may be effected by using a suitable adhesive and if necessary a hot stamping die to enhance the adhesive action of the cement which is used. Many types of adhesives or cements are available for the purpose, including the thermoplastic and thermosetting types of adhesives, as those skilled in the art will understand. By stamping the transmission circuits from a metal sheet in the manner described, it is possible when a properly designed cutting die is employed, to insure exact uniformity and reproduceability of the circuits in quantity. An important advantage of such procedure is to insure that the exact desired form of circuit will be produced with the parts in the exactly desired relative position. Furthermore, by thus attaching them to the supporting panel these conditions are maintained throughout the useful life of the structure.

In order to attain the desired low inductance values required, the transmission line is provided with taps in the form of contacts, one for each of the frequency channels to which the transmission line is to be tunable. To further assure the desired low inductance values, the contacts which form the taps are made of relatively heavy metal With respect to the metal of the transmission line thereby assuring that the low inductance In demade for the inductance of the contacts so that the finished circuit can be tuned to the desired frequency with the required accuracy.

Further contributing to a low inductance circuit, a low inductance ground is provided and switch contacts are arranged to connect the various taps selectively to this ground by a very short connection.

It is desired to emphasize that in the case of a plurality of transmission lines it is necessary that they bear in each case the same relationship to each other in physical spacing so that intercircuit values such as intercircuit capacity coupling and electrostatic coupling will be the same. To accomplish this object, the plurality of circuits are stamped simultaneously from a single sheet of metal and simultaneously attached to the support so that the desired spatial relationship is assured with a properly designed coating die.

In the station selector illustrated, three transmission circuits are provided. One provides the oscillator circuit, another the converter circuit, and the third a radio frequency circuit. Additional radio frequency circuits may be added when required. In the push button and rotary types illustrated, the taps of each of these circuits corresponding, for example, to a particular television channel, may be directly connected to associated ground circuits simultaneously, so that by a single operation all of these circuits are simultaneously tuned to the same television channel.

The ground straps which may also be stamped to exact size are attached on the back of the channel and are so aligned with their associated transmission circuits attached to the front that they act as part of the tuned circuits, thereby giving a higher ratio of inductance to capacity to assure higher gain and amplification as is well understood in this art.

In order to provide lower inductance to ground, additional ground circuits can be stamped on the top of the panel in the same way as are the transmission circuits and connected to the ground straps at the back of the panel electrically and mechanically by means of rivets or eyelets which interconnect them.

In order to compensate for variation in vacuum tube capacitance used in such circuits, it is desirable to provide for small adjustment of the inductance of the associated transmission lines. This is accomplished by providing large flat head screws which are associated with the transmission line and adjustable with respect thereto to provide the necessary compensation.

The manner in which the above objects and functions are attained will first be described in connection with Figures 1 to l, inclusive, wherein a television push button selector switch including the associated transmission lines is illustrated. In the form shown it includes a chassis consisting of a base plate I having a large opening 2 therein and provided with integral upturned end Walls 3. A series of side walls l, 5 and B are attached to the base plate and between the end walls to provide a flat rectangular housing, a portion of the top of which is closed by means of two plates 5' and 8, of insulating material. These plates are respectively secured to the chassis by means of the screws 9 and it. The insulating plate sections i and 8 can be in a single piece, if desired, but in some cases stamping of the attached parts is facilitated by making it of two parts. Mounted on the plate 8 are the vacuum tube sockets l l, I2 and 13 which in the case illustrated are adapted to receive the oscillator, converter and high frequency tubes respectively used in such a device.

Attached to the insulating panel 1 are the three transmission lines I9, 20 and 2| integral with which and formed simultaneously therewith by stamping are the spiral inductances l4, l5 and I6, respectively, and as shown, the rectangular extensions 22, I22 and 222. The configuration of these three transmission lines is determined by the electrical characteristics and spatial conditions permissible. These transmission lines are provided with taps or lateral extensions upon which are superposed the relatively heavy metal contacts 59 2c and 2 l respectively, which are secured to the panel I and mechanically and electrically engaged with the side extensions of the transmision lines by means of rivets or eyelets i9 28*, and Zl The inductances it, it; and It are adjustable by means of large. flat metal head screws of which two are illustrated at H and i8. These screws threadedly engage at apertures at the center of the spiral inductances and can be longitudinally adjusted by turning. The transmission line 22 terminates at an eyelet 23 which extends through the panel l7 and is electrically in contact with the ground strip 33 as illustrated in Figure 2. A pair of metal ground plates 23 and 25 are attached to the panels 7 and 8 by means of eyelets or rivets. In the case of the ground plate 25, its attaching eyelets 2e also electrically and mechanically engage the ground strip 23, see Figure 2. In the case of the ground strip 23, the eyelets 34 electrically and mechanically engage the ground strip and the eyelets 35' electrically and mechanically engage the ground strip 35. Those terminals of the sockets ll, [2 and I3 which require grounding are provided with ground tabs li i2 12 it i3 and 13 which may be for example soldered to the ground strips 23 and 25, as illustrated.

The push button levers are illustrated at 2'! to 21, inclusive. The rotary manual 26 is provided to adjust the oscillator circuit trimmer condenser and in this form of device there are no features of novelty disclosed in connection therewith and so no further reference thereto will be made. It

will also be understood that there is additional equipment within the chassis associated with the manual .25 and the tube sockets II, I2 and I3 but they are not illustrated and no further reference thereto is deemed necessary.

The manuals fil to 21 consist of metal bars with finger buttons on the exposed ends which bars are mounted for longitudinal sliding movement in the chassis housing as will be clear from Figures 2 and 3. Each thereof corresponds to a frequency channel to which the equipment is tunable. is clear from Figure 4, each of the contacts 55 Titl and 2 l consists of right angle metal pieces, the short arm of which, as is clear from Figure l, overlies a lateral extension integral with the portions [9, 2t and ii of the transmission circuit while the longer extension. projects through a rectangular opening in the panel 7 so as to provide three rows of contacts as will be clear from the drawings extending parallel to the ground strips 33, E4 and 35, respectively, but spaced a short distance therefrom. These ground strips are provided with upturned taps 33 34 and 35 which are aligned with the contacts [9 23 and Zi respectively, as is clear from Figures 2 and 3.

Although not part of this invention, the interconnecting mechanism between the push button rods having been illustrated, it will be described. As shown in Figure 3, each rod is provided with a cam shaped notched projection 28, attached to cooperate with a latching bar 3| which is pivotally mounted on a pair of brackets 30, see Figure 1, attached to the bottom wall of the chassis. The free edge of the latch bar 3! is held down by means of a tension spring 32 anchored to the bottom wall 3| as shown and each of the push button bars has a compression spring 29 mounted on it so as to lie between the side wall 6 and the lateral projection 23. When a button is pushed toward the chassis, the notched camming projection 23 rides under the latch bar 3! and spring 29 is compressed. Spring 32 resists the clockwise movement of the latch bar 3 l Figure 3, under the action of the camming projection 28 so that as soon as the notch thereof comes under the edge of the latch bar, spring 32 will pull it down into the notch, holding the push button bar in actuated position. When any other push button bar of the group is later pushed inwardly its carnming projection 28 will raise the latch bar against the resistance of spring 32 so that spring 29 of the previously actuated push button bar may return it to normal position while the latch bar latches in actuated position the other push button bar. Thus, as is Well 6 understood in this art, upon actuation of any push button a previously actuated button will be released to be returned to normal position so that the circuits can be tuned to only one frequency channel at a time.

Each of the push button bars as, for example, bar 21 is provided with three substantially U- shaped contacts a, Z) and c, which are made of thin spring metal and are generally U-shaped. They are slipped over the bar El so that it nests in the bases thereof and they are attached thereto by means of eyelets or rivets, as shown. The extending arms of these contacts are slotted to provide two pairs of cooperating spring fingers which are transversely curved as shown in Figure 4. These contacts are attached to the bars such as the bar 21 in such a relative position that when the bar is unactuated, that is in the position shown in the drawings, these contacts will engage the tabs 33*, 34 and 35 respectively, as shown in Figure 3, and when they are in actuated position these contacts will interconnect these same tab with the terminals it, 241 and 2H, respectively. The result is that the three transmission circuits in the output circuits of the tubes in the sockets ii, ill and i3 will be active up to the taps corresponding to the particular push button rod which has been actuated. By way of example, if push button rod Zl has been actuated, the transmission circuits i9, 29 and 2! will be active up to the first tap-cit terminal of each of these circuits which will be respectively grounded by the contacts a, b and c to the ground strips 33, 3 5 and 35. Similarly, the actuation of any one of these push button rods will return the previously actuated rod to inactive position and complete the transmission circuits up to the tap-off points corresponding to the terminals Mi 29 and 2 i associated with the particular actuated rod. The grounding of each of the transmission circuits takes place simultaneously by the single actuation of a particular button as will now be apparent. Thus, in the case described the oscillator, converter and high or radio frequency circuits will be completed to ground.

The same principles as previously illustrated have been incorporated in the rotary switch of Figures 5 to 10, inclusive. One suitable form of rotary switch is shown in Figure 5 which includes a cage or support comp-rising the insulating plates ll, 42, 43 and 41! secured together in spaced parallel relation by a suitable number of longitudinal traps e9. Journalled in suitable bearings in this structure is a longitudinally extending and centrally placed shaft 55 preferably of noncircular cross section to the end of which is secured an operating knob Attached to the shaft 45 adjacent the knob is a C-washer 49 located on the shaft and against which a second operating knob or wheel ll rests. The knob ll is connected to a sleeve M which is rotatably mounted on the shaft 45 and has secured at its far end a rotor plate of insulating material which has secured on one face thereof a metal plate or foil Eli which is attached thereto in any suitable manner as by stamping and cementing, as previously explained with respect to the transmission circuits. Attached to the end plate ll are standards 53 which in turn support an insulated stator 52 to which in turn are secured a pair of metal plates or foils 52 attached in the same way for example. Interposed between the stator '52 and the sleeve 48 is a dished spring washer 5B which holds the parts 41, 48 and SI against the spacing washer 49 to hold the rotor a desired distance from the stator 52. The elements 5! and 52 provide a trimmer condenser which is to be connected in the output circuit of the oscillator to provide the necessary fine frequency adjustment for that circuit in an inexpensive form and convenient location with re spect to the main tuning knob 46.

Figures 6 and 7 show the opposite sides of the wafer 42 which is generally similar in construction to the wafers 43 and 44 representing the three transmission circuits illustrated for the rotary type of switch. As illustrated in Figure 6, the transmission circuit includes an integral stamped spiral inductance 54, an arcuate conductor 55, a spiral inductance 56, a U-shaped inductance 51 and the spiral inductances 58, 60 and 6|. As illustrated, the inductances 56, 51, 58 and 66 are not integral with each other and the arcuate conductor 55 although they might be so as to be stamped simultaneously. In the case illustrated, the outer end of inductance 56 is connected to the strip 55 by means of a connector 56 on the back of the panel and its inner end is connected on the back of the panel to one terminal of the inductance 57 by mean of the connector 56 The center of inductance 58 is connected on the back of the panel to the outer terminal of inductance 60 by means of a connector 56. The center of inductance 66 is connected on the back of the panel to the outer terminal of inductance 6! and its inner end terminal in turn is connected on the back of the panel by means of a connector 56 to one of the contacts 66. The connectors 56 to 56 may be stamped onto the back of the panel similarly to the previous description for such forming and attaching operations and be connected through to the corresponding parts on the front of the panel by means of rivets or eyelets a shown. A series of taps arranged concentrically and mechanically, and electrically connected to the arcuate strip 55 by eyelets 66 are shown at 6B. These taps are in the form of pairs of spring contact fingers between which a radial tab 68*- on the metal ring 68 may pass. The spiral inductance may be adjusted as before by means of fiat headed screws as in the case of screw 62 illustrated for inductance 64.

The ring 68 is attached to an insulating rotor 61 which is mounted on the shaft 45 for rotation therewith. On the opposite side of the rotor 67 is another metallic ring 69. Rings 68 and 69 are attached to the insulating rotor in any suitable manner as, for example, by the inwardly radially projecting tabs 69b and 691) shown in each case. The rings 68 and 69 are electrically connected together in any suitable manner, as for example by means of a drop of solder (not shown), which would cross-connect an adjacent pair of tabs 68 and 69. Attached to the back of the panels are several spring clips 70 which engage the ring 69 and make permanent contact therewith. These contacts in turn are connected to a ground plate ll attached to the back of the panel as shown in Figure 7.

As will be apparent in view of all the foregoing it will be seen that as the knob 46 is rotated rotor 67, with its attached rings 68 and 69, will turn with it. As these rings are electrically connected whenever the tab of ring 68 engages one of the contacts 60 it will be seen that the transmission circuit including the parts 54, 55, 55, 57, 58, 66 and 6| will be tapped oil to the ground plate H so that in the case illustrated the switch is adapted to a twelve channel or frequency television receiver, for example. As the rotor moves in a clockwise direction, Figure 6, from the position shown, around a complete circle any one of the twelve taps may be engaged to tune the circuit to any one of the twelve frequencies. The construction for the wafers 42 and 44 is the same as that of wafer 43, so that all three transmission circuits are simultaneously tuned to the same frequency.

As in the case of the push button type all of the metal parts with the exception of the contact 66 may be stamped onto the wafers on one or both sides by a cutting die of predetermined design so that great uniformity of reproduction can be effected between the electrical tolerance limits required for very high frequency circuits. Thus, uniformity and low cost is attained in a practical manner.

In view of the above description it will be apparent to those skilled in the art that the subject matter of this invention is capable of considerable variation and I do not therefore desire to be limited to the illustrative embodiments herein disclosed but only as required by the claims granted me.

What is claimed is:

l. A television station selector unit comprising a chassis having an insulating support mounted thereon, a set of three inductive substantially planar circuit conductors attached to one side of said insulating support, a set of three substantially planar conductors to be grounded attached to the other side of said insulating support and electrically associated respectively with said circuit conductors to provide conductor pairs, said conductor pairs providing oscillator, converter and high frequency transmission circuits, a plurality of taps for each of said circuit conductors and means for simultaneously selectively connecting said taps of each circuit conductor to the associated ground conductor respectively.

2. In the combination of claim 1, each of said conductor pairs having contacts aligned respectively in pairs and said means simultaneously interconnecting the corresponding ground and circuit conductor contacts of each of said three circuits.

3. In the combination of claim 1, each of said circuit conductors including a multi-turn planar inductance, said selecting means adjusting the inductance thereof.

References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date 1,395,390 Clement Nov. 1, 1921 2,062,253 Walker et al -1 Nov. 24, 1936 2,092,069 Hollmann Sept. 7, 1937 2,183,723 Paschke Dec. 19, 1939 2,414,280 Thomas Jan. 14, 1947 2,423,152 Mitchell July 1, 1947 2,474,988 Sarbrove July 5, 1949 2,497,747 Valdettaro Feb. 14, 1950 FOREIGN PATENTS Number Country Date 103,948 Australia May 26, 1938 OTHER REFERENCES Electronics for September 1948, pages 76-79. Television Front Ends by Sobel.

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