US2014532A

US2014532A - Television system

Info

Publication number: US2014532A
Application number: US628341A
Authority: US
Inventors: Winfield R Koch
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1932-08-11
Filing date: 1932-08-11
Publication date: 1935-09-17
Anticipated expiration: 1952-09-17
Also published as: GB412435A

Description

W. El KOCH TELEVISION SYSTEM Filed Aug. ll, 1932 atented Sept.. l?, i935 l* A T E j? *Si OFQE TELEVISIION SYSTEM ci Delaware Application August 11, 1932, Serial No. 628,341

8 Claims.

My invention relates to improvements in television systems, and more particularly to receiving systems embodying a cathode ray tube.

The cathode ray tube is now recognized as superseding the mechanical scanning disk for television reception. During the long period of development of the cathode ray tube receiver, many problems and diinculties arose, any one of which, if remaining unsolved, would have prevented the use of the cathode ray tube for television reception. While cathode ray tube receivers have now been constructed and operated successfully, the work of refinement still progresses, and has been likewise attended with problems of no small consequence.

For example, in one form of cathode ray tube receiver, the chassis comprises a metallic base plate through which the tube extends. The various tubes comprising the high-frequency ampliiiers are mounted on the base plate, about the cathode ray tube. For the purpose of minimizing regeneration in the high-frequency amplier circuits, it is important that one end of the lament of each tube be grounded to the base plate. When this is done, however, and the desired cycle house current is used for supplying heating current to the tube filaments or catho-de heaters, serious difficulties arise due to chassis currents which then occur. These currents tend to pass through the base plate along paths about the axis of the cathode ray tube. One diiculty resides in the fact that the chassis currents cause voltages to be induced in the amplifier circuits mounted on the chassis, causing interference with the proper functioning of the amplifiers for both the picture and sound signals. Another diiiiculty resides in the fact that the iiuX developed by the chassis currents -distorts the cathode ray, or, in other words, interferes with the scanning pattern. These difculties, heretofore, have been so serious that it was found necessary to revert to direct current for heating the filaments of the amplifier tubes.

With the foregoing in mind, it is one of the obj ects of my invention to provide improved television receiving apparatus, embodying a highfrequency amplier, wherein the amplifier tubes are mounted on a metallic base plate, wherein one end of each tube filament or cathode heater is grounded to the plate, wherein a standard alternating current supply source is used for heating the tube laments, and which avoids the various diliculties encountered heretofore and referred to above.

Another object is to provide improved television receiving apparatus of the character referred to wherein the tubes comprising the intermediate-frequency ampliner are mounted on the base plate with the other ampler tubes, and wherein the filaments of the former are grounded to the base plate and supplied with alternating current, without incurring the dis advantages referred to.

Other objects and advantages will hereinafter appear.

In accordance with my invention, one end of the lament of each amplifier tube is grounded to the base member. The tubes are connected in pairs to an alternating current supply source in the sense that in each pair, the current supplied to the respective filaments is substantially one hundred and eighty degrees out of phase.

My invention resides in the system and method of operation of the character hereinafter described and claimed.

For the purpose of illustrating my invention, an embodiment thereof is shown in the drawing, wherein Figure 1 is a perspective view, partly diagrammatic, of a cathode ray tube television receiver constructed and operating in accordance with my invention; and

Fig. 2 is a fragmentary perspective view, illustrating some of the details of construction in Fig. 1. 30

The receiving apparatus comprises the usual metallic base plate il) through which a cathode ray tube l2 extends, the latter being supported, with its axis perpendicular to the Iplate il), by a frusto-conical supporting shield Hl. The tube I2 is provided With a suitable electron gun it for developing a ray of electrons and directing same at the iluorescent screen iB at the large end of the tube. Electromagnets 2B and 22, for deflecting the ray horizontally and vertically, respectively, are disposed as shown in Fig. 2, supported from the plate Ill.

The transmitted picture and sound signals are intercepted and supplied to the receiving apparatus by connections 26.

4V* The amplier for the sound signals and the high-frequency-response amplifier for the picture signals comprise the tubes 28, 3D, 32, St, 36, and other tubes which are covered by shielding cans 38 and 4D. as having filaments, it is to be understood that they may be of the equi-potential type having cathode heaters, and the term filament when used hereinafter is to be understood as meaning either cathode heaters or filaments.

Though these tubes are shown 50 The amplier tubes are mounted on the base plate and are grouped, as shown, about the cathode ray tube l2. For the purpose of minimizing regeneration in the high-frequency ampliiier, one end of the filament of each tube is grounded to the plate lil. That is, one end of Vthe filaments of the

tubes

28, 30, 32 and 3d are grounded to the plate l0, at the points 42, 44, i6 and 38, respectively, in close proximity to the respective tubes. One end of the laments of the other tubes is grounded in the same manner to the plate I9.

The laments of the amplifier tubes are supplied with heating current from a power transformer 5i! connected to an alternating current supply source 52. The secondary of the transformer is provided with a mid-tap connection 54 which is grounded, as indicated, to the plate it.

The two connections 56 and 53, from the ends of the transformer secondary, therefore provide for the supply of alternating current to the other ends of the tube filaments, the current in one of these connections being one hundred and eighty degrees out of phase with the current in the other.

The amplifier tubes are connected in pairs. That is, considering the pair of tubes 3Q and 3, the ungrounded end of the filament of tube 32 is connected to the supply connection 5S, whereas the ungrounded end of the filament of tube 34 is connected to the supply connection 56, as shown. In like manner, considering the pair of tubes 28 and Si), the ungrounded end of the filament of tube 28 is connected to the supply connection 58, whereas the ungrounded end of the lament of tube 3G is connected to the supply connection 56. Similarly, the other tubes disposed about the cathode ray tube l2 are connected in pairs in the sense that the current supplied to the respective filaments of each pair is substantially one hundred and eighty degrees out of phase. The amplifier tubes having their filaments connected to the supply connection 56 may be considered as one group, and the amplier tubes having their filaments connected to the supply connection 58 may be considered as another group. The tubes, therefore, can be considered as being connected in group fashion in the sense that the current supplied to the filaments of the respective groups is substantially out of phase, and, in the disclosed embodiment of my invention is one hundred and eighty degrees out of phase.

By reason of the connections just described, the chassis current which tends to develop from the amplifier tube of any one pair is balanced by or compensated for by the chassis current which tends to develop from the other amplifier tube of this pair. For example, considering the pair of tubes 32 and 34, at any instant the direction of current flow from the point 46 will be opposite to that from point 48, and the amount of current flow from these two points, at this instant, will be substantially the same. The same action takes place at any instant with respect to the other pairs of tubes, such as the

tubes

28 and 30. In this way, current flow in a direction clockwise about the base plate lil is substantially balanced by or compensated for by current flow in a counterclockwise direction about the base plate. Any chassis current which might be present is only the unbalanced current in the connection 5d. This is practically negligible, and does not interfere with the proper functioning of the receiving apparatus.

From the foregoing it will be seen that I have provided improved television apparatus wherein one end of the filament of each amplifier tube is grounded to the base plate, and wherein the lilaments are supplied with alternating current for 5 heating, all without permitting large alternating currents to develop in the chassis to induce undesirable voltages in the amplifier circuits and to also interfere with the desired deflection of the cathode ray. l

While but one embodiment of my invention has been disclosed, it will be understood that various changes might be made without departing from the spirit of my invention or the scope of the claims. l

I claim as my invention:

1. In a television system, means for intercepting and receiving transmitted picture signals a base member of electrically-conductive material, means for reproducing the picture comprising a cathode ray tube associated with said member and provided with screen structure at one end and with means at its other end for developing a cathode ray and directing the same at said screen structure, means for defiecting the ray to cause the same to scan said screen structure, means forl amplifying the received picture signals and comprising a plurality of electron tubes mounted on said base member and each provided with a filament, and an alternating-current supply source for said filaments, one end of each filament being grounded to said base member, the other ends of said filaments being connected to said supply source, said tubes being connected in pairs in the sense that the current supply to the respective filaments of each pair is substantially one hundred and eighty degrees out of phase.

2. Cathode ray tube apparatus comprising a base member of electrically-conductive material, a high-frequency-response amplifier for amplifying received picture signals and comprising a plurality of electron tubes mounted on said member and each provided with a lament, a cathode ray tube having a neck portion extending through an opening in said member, and an alternating current supply source for said filaments, one end of each lament being grounded to said member, the other ends of said filaments being connected to said supply source, said tubes being connected in group fashion in the sense that the current supply to the respective laments of each group is substantially out of phase.

3. Cathode ray tube apparatus comprising a base member of electrically-conductive material, a plurality of electron tubes mounted on said member and each provided with a lament, said tubes comprising a high-frequency-response amplifier for amplifying received picture signals, a cathode ray tube having a neck portion extending through an opening in said member, and two connections for the supply respectively of alternating currents substantially one hundred and eighty degrees out of phase, one end of each of said iilaments being grounded to said member, the other ends of certain of said laments being connected to one of said supply connections, the other ends of the remaining filaments being connected to the other of said supply connections.

4. In a television receiving system, means for intercepting and receiving transmitted picture and sound signals, a base member of electricallyconductive material, a cathode ray tube extending through said member and supported with its axis substantially perpendicular thereto, said 7.5

tube provided with screen structure at one end and With means at its other end for developing a cathode ray and directing the same at said screen structure, means for deecting the ray to cause the same to scan said screen structure, means for amplifying the received picture and sound signals and comprising a plurality of electron tubes mounted on said base member and grouped about said cathode ray tube, one end of the filaments of at least the greater number of said electron tubes being grounded to said base member, and two connections for the supply respectively of alternating currents substantially one hundred and eighty degrees out of phase, the ungrounded ends of certain of said filaments being connected to one of said supply connections, the ungrounded ends of the other of said filaments being connected to the other of said supply connections.

5. In cathode ray apparatus, a metallic baseplate having an opening therethrough, a cathode ray tube having a neck portion extending through said opening, amplifying apparatus including a plurality of space current devices each having a filament, the said devices being grouped in pairs in proximity to the neck of the cathode ray tube, a connection from one terminal of each filament to the base-plate, a power transformer having a. mid-tapped secondary Winding, a connection from the mid tap to the base-plate, and connections leading from the remaining terminals of each pair of space current device laments, respectively, to opposite terminals of the secondary winding whereby, when the filaments of each pair of space current devices are energized from the transformer the currents in the base plate are so neutralized as to prevent interference With the operation of the cathode ray tube.

6. The invention set forth in claim 5, additionally characterized in that the base plate is 5 provided with a plurality of openings into which the space current devices, respectively, extend.

7. The invention set forth in claim 5, addi tionally characterized in that the mid-tap on the transformer secondary is provided with a con- 10 nection to ground.

8. In a television receiving system, means for intercepting and receiving transmitted picture and sound signals, a base member of electricallyconductive material, a cathode ray tube assol5 ciated with said member. said tube provided with screenustructure at one end and with means at its other end for developing a cathode ray and directing the same at said screen structure, means for deilecting the ray to cause the same 20 to scan said screen structure, means for amplifying the received picture and sound signals and comprising a plurality of electron tubes mounted on said base member, one end of the laments of at least the greater number of said electron 25 tubes being grounded to said base member, and two connections for the supply respectively of alternating currents substantially one hundred and eighty degrees out of phase, the ungrounded ends of certain of said filaments being connected to one of said supply connections, the ungrounded ends of the other of said filaments being connected to the other of said supply connections.

WINFIELD R. KOCH. 35