US2757316A

US2757316A - Means for brightening picture tubes

Info

Publication number: US2757316A
Authority: US
Inventors: Norman A Ackerman
Original assignee: PERMA POWER CO
Current assignee: PERMA POWER CO
Priority date: 1952-06-13
Filing date: 1952-06-13
Publication date: 1956-07-31
Anticipated expiration: 1973-07-31

Description

y 31, 1956 N. A. ACKERMAN 2,757,316

MEANS FOR BRIGHTENING PICTURE TUBES Filed June 13, 1952 2 Sheets-Shae: 1

7 USUAL PICTURE TUBE Bl- METAL "8 V. 60 CY.

INVENTORZ NORMAN A. ACKERMAN B ATTORNEYS:

July 31, 1956 A. ACKERMAN MEANS FOR BRIGHTENING PICTURE TUBES 2 Sheets-Sheet Filed Jun 13, 1952 Fl G. 3

66 H 6| E 5 H 64 TIME FIG. 7

INVENTOR ACKERMAN NORMAN A.

ATTORNEYS:

United States Patent 2,757,316 MEANS FOR BRIGHTENING PICTURE TUBES Norman A. Ackerman, Chicago, 11]., assignor to Perma- Power Company, Chicago, 11]., a corporation of Illinois Application June 13, 1952, Serial No. 293,302 Claims. (Cl. 315106) It has been proposed to remedy this situation by applying a substantially higher voltage to the picture tube filament over a period of from one to thirty minutes. This process is known as boiling out the filament. This results in a substantial increase in brightness for a comparatively short period of from two to three months after which the boiling out process is again necessary.

I have found that by increasing the voltage on the picture tube filament to a much lesser extent, and by maintaining such increased voltage on the filament continuously, whenever the tube is used, that the brightness of the tube will be maintained for a much longer period of time than when the brightness is increased by the boiling out method. 7

Furthermore, this boiling out is a service operation which requires special equipment; hence, it is a rather costly solution to the problem as it requires from four to six service calls a year in order to maintain the tube at the desired brightness.

It is an object of this invention to provide means for increasing the brightness of a tube, or for reactivating the same, which avoids the aforesaid difiiculties of the prior art boiling out method.

A further object is to provide such a device which is in the form of an attachment which, when incorporated into a television receiver, will prolong the life of the picture tube for as much as a year.

In connection with the application of the aforementioned principle to the commercial television receivers now on the market, applicant has found that it is not commercially practical to re-wire the receiver for the purpose of providing a separate power source for the picture tube filament.

The various tubes of the present day commercial television receiver are powered from a common source; a separate transformer is not provided for the picture tube. Therefore, in applying a higher voltage to the picture tube filament, it is not merely a question of substituting a different transformer for the picture tube filament; an additional transformer must be provided.

It is a further object of my invention to provide, in a commercial television receiver, a separate transformer for the picture tube filament, together with control means therefor which do not require a re-Wiring of the receiver.

The foregoing object is obtained by connecting the separate power source to the two filament prongs of the picture tube base. Then a relay is provided which is connected into the chassis filament circuit in such a manner that the latter serves as a control circuit for the independent picture tube filament circuit. Thus, it is not necessary to run separate leads from the separate 2 power source to the olf-on switch of the television receiver.

A further object is to provide a device of this type, which can be referred to as a reactivator, in the form of a separate unit which can be readily interposed into a standard filament circuit by means of the detachable connection provided by the picture tube base and its socket.

A still further object is to provide an independent power source for the picture tube filament of a commercial television set which is insulated from the cathode circuit, whereby a short circuit between the filament and cathode due to a sagging filament or the like can be remedied.

A still further object is to provide a reactivator which can be mounted on the television receiver, in an accessible location, and which is provided with means for successively increasing the voltage applied to the picture tube filament, so that the operator may apply a greater voltage to the picture tube filament from time to time, as conditions require, without the necessity of calling a serviceman.

A further object is to provide a reactivator suitable for both series connected and parallel connected filament circuits.

Other objects, features and advantages will become apparent as the description proceeds.

. 18, and a cable With reference now to the drawings in which like reference numerals designate like parts:

Fig. l is a view showing a preferred embodiment of my invention in conjunction with a standard picture tube and a standard base therefor;

Figure 2 is a circuit diagram of the parts shown in Fig. 1;

Fig. 3 is a further circuit diagram showing the relationship of the reactivator to a series connected filament circuit of a standard television receiver;

Fig. 4 is a circuit diagram similar to Fig. 3, but showing the reactivator in connection with a parallel connected filament circuit;

Fig. 5 is a circuit diagram illustrating a modified form of my invention;

Fig. 6 is a detailed sectional view showing the manner in which the tap switch is mounted in the transformer cover so that the same is readily accessible, and

Fig. 7 is a graph illustrating the nature and operation of my invention.

In Fig. l, the reference numeral 10 designates a picture tube of the type which is used in commercial television receiving sets, the picture tube having a standard typeof base 11. The usual commercial set is also provided with a socket 12 for the base 11, the socket being connected by a flexible cable 13 to a chassis 14.

The present invention provides a reactivator 15 which comprises three separate components: a socket 16 for the base 11, a base 17 for the socket 12 and a separate component referred to herein as unit 18. The latter includes a transformer 19 and a relay 20 as shown in Fig. 2, and these elements are enclosed by a cover 21 and a base 22. A cable 23 connects socket 16 with the unit 18; a cable 24 connects base 17 With the unit 25 connects the socket 16 with the base 17. It is understood that the bases 11 and 17 are provided with the usual prongs 26, and the

sockets

12 and 16 are provided with apertures 27, the prongs being received within the apertures and engaged by the resilient contacts which are not shown.

Another cable 28 extends from the unit 18 and is provided with a wall socket connector plug 29 so that the transformer 19 may be independently powered. Thus, the reactivator comprises, essentially, a separate unit 18 together with suitable means, such as the socket 1'6,

base 17 and connecting cables, for interposing the unit between the chassis filament cir'nit, and the picture tube filament. Of course, if desired, the socket and base 16 and 17 maybe combined into an integral unit, with the consequent elimination of cable 25; this also would permit forming the

conductors

23 and 24 into a single cable. However, the present arrangement is preferred for the purpose of illustration.

Fig. 2 is a Circuit diagram in which the picture tube 10, is conventionally represented as having a filament 30, a cathode 31 and the usual grid elements 32. The filament 30 is suitably connected to filament prongs 33 and '34; These, in turn, are adapted for electrical connection with the

conductors

35 and 36 which connect with 'theseconda'ry 37 of the transformer 19. The

conductors

35 and 36 comprise the cable 23. Conductor 36 is connected directly to the secondary winding 37, whereas conductor 35 is connected to a movable contact 38, the latter being designed to make contact with sneer a plur'ality of taps 39 which are provided on the $d d yi 'The'primary 40 is connected by suitable conductors to the cable 28 so that it may be independently enerjg'iied'fr'om the usual house lighting circuit. in the primary circuit is a relay switch 41 which includes a secondary contact 42, and a movable contact 43 which is carried on a bimetallic strip 44. The heater is'connected by'conductors 46'and 47, which comprise the cable 24, to prongs 48 and 49 .of the base 17. These prongs, intnrn, are adapted to be connected to conductors 50, 51 respectively, which form 'a part of the chassis filament circuit.

The remaining prongs 52 of base 11 are connected to the remaining prongs 53 of base 17 by three separate conductors which comprise the cable 25. The prongs 53 are connected into the chassis 14 by suitable conductors 54 which are contained in cable 13.

In Fig. 2, the various elements of the reactivator are boxed in and designated generally by the reference numeral 15; the elements outside of the box being standard elements found in any commercial television receiver.

Fig. 3 shows diagrammatically the relationship of the reactivator to a series connected chassis filament circuit. In this diagram, the reference numeral 6% designates the filament of the various tubes of a receiver, other than the picture tube filament, which is designated by the reference numeral 30. These filaments'60 are connected into a series circuit with each other and with a wall socket connector plug 61 by means of suitable conductors 62. The usual off-on switch '64 is interposed between the filament circuit and the source of power represented by the plug 61.

v Thereactivator 15, which includes the heater 45, is connected into this circuit as shown diagrammatically, the'heater'45 serving to avoid such a break in the

series circuit

60, 62 as would necessitate are-wiring of the set. Preferably,'the heater 45 is made so that it has the same resistance as the filament 3i), so as to avoid any change in the voltage applied to the filaments 60. Fig. 3 also illustrates the manner in which the closing of"the;'off-on switch 66 serves as a signal to energize theheater 45, whereby the reactivator 15 and the picture tube filament'30 are controlled by the single off-on switches.

" ig. 4 shows diagrammatically the relationship of the Interposed tivator to a parallel connected chassis filament cir- 4 former being designed to deliver 6.3 volts 'to. all of the filaments. Since the heater 45 has the same resistance as the filament 30, no additional load is imposed upon the power transformer 66.

Fig. 5 shows a modified form of the invention which is adapted for use only with a parallel connected chassis filament circuit. Inthis embodiment of the invention, the reactivator 15 includes a transformer 19 having a primary 67 and a secondary 63. The primary is connected to the conductors 65, and thus forms apart of the filament circuit. "The secondary '68 is connected to the picture tube filament 3i), and may of course, include the tap switch 38-419, if desired, so as to proa uniform voltage of vide for a series of successive voltage increments, just as shown in connection with Fig.2. Thus, in this embodiment of the invention, the picture tube filament is powered directly from the filament circuit, the increase in voltage being provided by a step-up transformer 19. Thus, there is no relay in this embodiment of the itivfen-. tion, since the picture tube an independent source of power. 7 Y

The Fig. 5 embodiment of the invention represents perhaps the simplest and least costly embodiment, but, since it is adapted for use only on a parallel filament circuit type of television receiver, it is not as acceptable from a commercial viewpoint as is the principal embodiment shown in Figs. 2-4, which is of universal application.

As indicated previously, television receivers are of two types, those having th'etparallel connected filament circuit,and those having a series connected circuit. The advantag'eof the latter is that the power transformer 66 can be eliminated; therefore, a substantial proportion of receivers now on the market are of the latter type. It is, of course, possible to adapt the Fig. 5 embodiment of the invention to aseries connected filament circuit type of receiver'by including in thefilarnent circuit a suitable resistance network without departing from the scope of my invention.

The Fig. 5 embodiment, in appearance, and when the tap switch is included, will be identical to the arrangement shown in Fig. l, includingthe three separate components, socket 16, the base 17, and the unit 18.

One feature of the present invention is the fact that the voltage on the picture tube filament may be successively increased over successive intervals to bring the tube back to its original brightness. These intervals may be as long as'six months or a year, depending upon the ex.- tent' to'which the tube is used. This result is obtained by the provision of the taps 39 which are designed to provide a series of increments in the tube voltage, each increment representing about a 7% increase. As shown in Fig. 2, four'such taps are provided,.representing voltages ores, 6.8, 7.25 and 7.8, thus providing three suc cessive increments. i

A related feature is the fact thata rotary type of tap switch is used, in which the rotary contact 38'is mounted on a stem 70 which projects through the cover 21 as.

screwed 'to the inside wall of the cabinet, or mountedexternallyat the back. Thus, for example, at six month intervals, as the tube grows dim, all the owner of the set needs to do is to rotate the stem another notch sons to apply an increased voltage to the picture tube filament. Once the reactivator is installed, the tube may be'rnaintainedat a satisfactory degree of brightness for a period of more than a year since the application of successive voltage increments does not require a service call.

Fig. 6 shows the manner in which the tap switch may ben ounted 'on'the cover. .For zinstance, 'aftype ofita'p filament is not energized 'by'. v

switch is used in which the rotatable stem' 70 is journaled in a threaded sleeve 75, a lower portion of the sleeve being provided with a flange portion 76 which engages the underside of cover 21. A pair of jam nuts 77 secure the sleeve in a portion of an aperture formed in the cover 21. A split ring 78 serves to maintain the relative positions of the stem 70 and the sleeve 75.

The lower end of the stem 70 is journaled in an insulating plate 78 which is supported from flange 76 by suitable means not shown. A plurality of stationary contacts 74 are mounted in the insulating plate 78, only one of these contacts being shown. These contacts 74 are provided with terminal portions 39 to which the taps 39 may be suitably connected. Also mounted on the plate is a stationary segment 79 of substantial length having a terminal 35 to which the conductor 35 is connected.

The movable contact 38 is in the is mounted on an arm 38 form of a rivet which of insulating material which is suitably keyed to the stem 70. Thus, as the stem is rotated, the movable contact 38 closes the circuit between one or the other of the several stationary contacts 74 and the common segment 79. As indicated above, the tap switch is mounted in a portion of the cover 21 so that the stem 70 is accessible when the unit 18 is secured to the cabinet of a receiver by means of the foot portions 71.

Although the

transformers

19, 19 may be of any desired type, certain additional advantages Will accrue where it is an insulated transformer, as contrasted with an autotransform-er. These arise from the fact that the secondary 37 and hence the filament 30, will be insulated from the tube chassis. When an insulated transformer is used, it is considered desirable to include a tap which applies the normal voltage of 6.3. Thus, in the case of a defective tube, where the faulty operation can be traced to a short circuit between the filament 30 and the oathode 31, due to sagging of the filament, this defect is remedied by the installation of the reactivator, since contact between these two elements, where the filament is thus insulated from the cathode, will not affect the tube operation. In such instances, it is desirable to operate the picture tube on its normal filament voltage until such time as a diminution of brightnes renders an increase of voltage desirable.

The brightening or reactivation provided by this invention is shown by the graph of Fig. 7, the abscissa representing time, and the ordinate representing brightness as measured by a light meter.

Fig. 4 shows three

curves

80, 81 shows the life curve of the filament in a new tube. Curve 81 shows the life curve of a filament which has been reactivated according to the present invention, and curve 82 shows the life curve of a filament which has been subjected to the boiling out process. The horizontal line 83 represents an arbitrary point below which the tube can be considered to be too dim for satisfactory operation.

In the boiling out process the cathode is heated intensely for a period of from one to three minutes, and then it is glowed for a substantially longer period at a comparatively high activation temperature. The heating is accomplished by applying an increased voltage to the filament; the initially applied voltage being twice the normal filament voltage. This boiling out process reforms the molecular thorium layer on the cathode. As shown by the curve 82 the increased brightness provided by this process falls off at a fairly rapid rate.

According to the present invention, by applying a slightly increased voltage to the filament, the temperature of the cathode is elevated somewhat, but to a much smaller extent than in the case of the boiling out process. By maintaining this increased voltage on the filament continuously, the kinetic energy of the electrons in the cathode is increasedso that they may escape more easily, thereby increasing the brightness. As a result and 82. Curve 80 'dim, the next voltage of this somewhat higher heat, there is believed to be some reformation of the molecular thorium layer, but not nearly so much as in the boiling out process. The over-all result of the method of this invention is a much more gradual falling off of tube brightness than that which obtains in the boiling out process, as illustrated in Fig. 7.

Furthermore, in the boiling out process, it has been found that tube failure occurs in a substantial portion of the tubes so treated, due to the greatly increased voltages involved, whereas no such tube failure has occurred in the practice of the present invention. Also, in the boiling out process, increased brightness does not always occur, with the result that the boiling out must be repeated, whereas the method of the present invention is not characterized by such lack of certainty.

As indicated above, the taps of the transformer 19 provide for successive voltage increments of about 7% or 8% each. I have found that there can be substantial variation one way or the other; in any event the increase is of an entirely different order than the voltage increase provided by the prior art boiling out process.

For instance, I have found that good results may be obtained with a voltage increase as low as 2 /2% and as high as 40%, the substantially 7% increase referred to herein being selected as representative of an increase which is large enough to produce satisfactory results, and which is small enough to permit the use of the same as one of several successive increments.

In some instances, however, when the tube is quite dim, the tap switch is initially moved to the 7.25 volt tap. Then, after a substantial period of use, if it again becomes increment is added. Similarly, it may be found desirable, at times to move the tap switch directly from the 6.8 volt tap to the 7.8 volt tap, this representing the second voltage increase applied to the filament. Thus, it will be seen that it is not necessary to limit the successively applied increments to a 7% voltage increase; under some circumstances a substantially 14% increment is desirable. However, I have found that when the reactivator is initially installed, it has never been found necessary to apply initially the highest obtainable voltage, namely, the 7.8 volt tap, to the filament, since equally satisfactory results have been obtained by the use of a lower voltage tap. Thus, the embodiments illustrated have been found to be useful in obtaining at least two successive voltage increments in any situation, and in the majority of situations it provides three voltage increments. Of course, it will be understood that additional voltage taps can be provided if desired so that four or five or more successive voltage increments may be obtained.

It is obvious that an electromagnet relay may be substituted for the thermal relay herein shown and described, the thermal relay being preferred from a cost standpoint.

Although only preferred embodiments of my invention have been shown and described herein, it is obvious that various modifications and changes may be made therein without departing from the spirit of the invention as pointed out in the appended claims.

I claim:

1. The combination of a television receiver, which includes a picture tube having an indirectly heated cathode and a heater filament therefor, a filament circuit ineluding power supply means for applying a normal voltage to said heater filament, and reactivator means, including a transformer, interposed between said filament circuit and said heater filament for applying an increased voltage to said heater filament, said transformer providing a voltage of from 2 /2% to 40% greater than the voltage supplied by said filament circuit.

2. The combination claimed in claim 1 in which the primary of said transformer is energized by said filament circuit.

' said replaceable unit may '3. A' reactivator for the picture *tube of a receiver having'an indirectly heated cathode, a heater filament therefor, and a filament circuit for applying a normal-voltage to said heater filament, said reactivator comprising atransformer having an output circuit designed to provide a voltage from two and one-half per cent to forty per cent greater than said normal voltage, and means for detachably connecting said output circuit to said heater filament. d

'4. A reactivator as claimed in claim 3 including a base, a cover cooperating therewith, said transformer being disposed within said base and cover, and having a plurality of taps, and a tap switch disposed within said base and cover and having arrotatable stem, said stem projecting through said cover so as to be accessible from the outside of said separate unit. a

' 5; A reactivator for the picture tube of a television receiver having a filament circuit and cathode and grid circuits for said picture tube, said picture tube having an indirectly heated cathode and a heater filament therefor, said reactivator comprising a replaceable unit including a transformer having an output circuit designed to provide a voltage from two and one-half to forty per cent greater than the voltage normally provided by said filament circuit, means for detachably connecting said output circuit to the heater filament of said picture tube, conductor means extending from said replaceable unit, second connecting means for detachably connecting said conductor means to said filament circuit whereby the operation of be controlled by said filament circuit, and additional conductor means extending from said first to said second connecting means to accommodate said cathode and grid circuits.

6. In a television rece ver, the combination of a power source, a plurality of tube filaments and a relay connected thereto, a relay switch actuated by said relay, a picture tube having an indirectly heated cathode and a heater filament therefor, and a transformer having a primary and secondary windings, the heater filament of said picture tube being energized from the secondary of said transformer, and said relay switch being connected in series circuit with the primary of said transformer whereby energization of said power source will cause the primary circuit of said transformer to be energized, thereby energizing the heater filament of said picture tube.

7. In a television receiver, the combination of a power source, a plurality of tube filaments and a heater connected thereto, a bimetallic switch actuated by said heater, a picture tube having an indirectly heated cathode and a heater filament therefor, and a transformer having a primary and secondary windings, the heater filament of said picture tube being energized from the secondary of said transformer, and said bimetallic switch being connected in series circuit with the primary of said transformer whereby energization of said power source will cause the primary circuit of said transformer to be energized,

thereby energizing tube.

8. A picture tube reactivator comprising a reactivator socket having first contact means for the filament prongs of a picture tube and having second contact means for the cathode and grid prongs of a picture tube, said picture tube having an indirectly heated cathode and a heater filament therefor, a reactivator base having filament circuit prongs and having cathode and grid circuit prongs, said base being adapted for cooperation with the usual picture tube socket so that the prongs of said reactivator base maybe connected into the chassis circuits of a television receiver, a transformer having prithe heater filament of said picture mary and secondary windings, a pair of conductors extending from said first contact means tosaid transformer secondary, whereby when said socket is applied to a picture tube, the secondary circuit of said transformer will include the heater filament of said picture tube, a plug connector, conductor means extending between said plug television connector and the primary winding of said transformer to form ,a primary circuitwhich may be energized from a house lighting circuit, independently of the usual power supply means ofa television receiver, a relay including a circuit closing means. in said primaryicircuit, actuating means for said circuit closing means, and a control cir cuit including said actuating means and the said filament circuit prongs of said base whereby said actuating means may be energized by the filament circuit of said television receiver, and conductor means extending between said reactivator socket and said base and connecting said sec ond contact means with the cathode and grid circuit prongs of said base whereby thecathode and grid of said picture tube may circuits of the television receiver when said reactivator socket is applied to said picture tube, and when said base is connected with said usual picture tube socket of a television receiver.

9. A picture tube reactivator comprising a reactivator socket having first contact means for the filament prongs of a picture tube and having second contact means for the cathode and grid prongs of a picture tube, said tube having an indirectly heated cathode and a heater filament therefor, a base having filament circuit prongs and having cathode and grid circuit prongs, said base being adapted for cooperation with the usual picture tube socket so that the prongs of said base may be connected into the chassis circuits of a television receiver, a transformer having primary and secondary windings, a pair of conductors extending from said first contact means to said transformer secondary, whereby when said socket is applied to a picture tube, the secondary circuit of said transformer will include the heater filament of said picture tube, a plug connector, conductor means extending between said plug connector and the primary winding of said transformer to form a primary circuit which may be energized from a house lighting circuit, independently of the usual power supply means of a television receiver, a relay including a bimetallic circuit closing means in said primary circuit, a heater for said bimetallic circuit closing means, and a heater circuit for said heater, said heater circuit including said heater and the said filament circuit prongs of said base whereby said heater may be energized by the filament circuit of said television receiver, and conductor means extending between said reactivator socket and said base and connecting said second contact means with the cathode and grid circuit prongs of said basewhereby the cathode and grid of said picture tube may be energized by the cathode and grid circuits of the television receiver when said reactivator socket is applied to said picture tube, and when said base is connected with said usual picture tube socket of a television receiver. I

10. The combination of a television receiver which includes a picture tube having an indirectly heated cathode and a heater filament therefor, a filament circuit including power supply means for applying a normal voltage to said heater filament, and reactivator means interposed between said heater filament circuit and said filament for applying an increased voltage to said heater filament, said reactivator means including a transformer having a primary which is energized by a power source other than said power supply means, and also including relay means energized by said filament circuit and controlling the operation of said transformer, said increased voltage being from two 7 and one-half per cent to forty per cent greater than said normal voltage.

References Cited in the file of this patent UNITED STATES PATENTS (Other references onv following page) be energized by the cathode and grid 9 UNITED STATES PATENTS 2,053,587 Van Den Berg Sept. 8, 1936 2,055,921 Baker Sept. 29, 1936 2,082,036 Stogoflf June 1, 1937 2,254,214 Gage Sept. 2, 1941 5 2,281,572 Gage May 5, 1942 2,413,707 Helliar Jan. 7, 1947 2,635,213 Bruene Apr. 14, 1953 FOREIGN PATENTS 10 618,041 Germany Aug. 31, 1935 OTHER REFERENCES Levy, Irving E.: Efiect of Impurity Migrations on Thermionic Emission from Oxide-Coated Cathodes, Proc. of I.R.E., vol. 41, pp. 365-368, March 1953.

Terman, F.: Radio Engineering, sec. 5-3, p. 155, Mc- Graw-Hill Book Company, Inc., New York, 1947.

Applied Electronics: Members of the Stafi of the Department of Electrical Engineering, Massachusetts Institute of Technology, p. 931, John Wiley and Sons, New York, 1943.

Kock, D. 6.: Increasing Tube Reliability in Industrial Circuits, Publication No. ST-65l, Tube Department, Radio Corporation of America, Harrison, New Jersey, 1952.

Reich, H. 1.: Theory and Application of Electron Tubes, p. 28, McGraw-Hill Book Company, Inc., New York, 1944.

Bounds, A. M., and Briggs, T. H.: Nickel Alloys for Oxide-Coated Cathodes, Proceedings of the I.R.E., vol. 39, 788799, 1951.