US1894051A - Control systems for hot cathode vacuum tubes - Google Patents

Description

Jan. 10, 1933.

A. MUTSCHELLER CONTROL SYSTEMS FOR HOT CATHODE VACUUM TUBES Filed April l0. 1926 TETE-JRE: .1 7;

2 Sheets-Sheet 1 lNVENTOR ATTORNEY Janf 10, 1933 A. MuTscHELLER 1,894,051

CONTROL SYSTEMS FOR HOT CATHODE VACUUM TUBES Filed April l0. 1926 2 Sheets-Sheet 2 :F.TTRE; E 4

ATTORNEY 'rss ARTHUR MUTSCHELLEE, F NEW YORK, Iii. Y., ASSGNOR TO VAPPLEB ELECTRIC COMPANY, ENC., A CORPORATIN GF NEW YORK CONTR-OL SYSTEMS FOR EGT CATHDE 'VACUUM TUBES Application led April 10,

My invention relates to control systems for hot cathode vacuum tubes; that is, to systems in which there are one or more valve tubes and one or more X-ray tubes, all provided with electrically heated cathodes, and in which the discharges through the tubes are controlled quantitatively by manual regulation of the circuit or circuits used for heating the cathodes. n

More particularly stated, my invention comprehends a system. well adapted for the production of X-rays capable of use in other relations, and in which two or more separate circuits, used for heating filaments or other electrodes employed as cathodes to be heated, are together controllable practically as a single unit for the purpose of quantitatively regulating the currents through the respective tubes.

ln Xray systems used in the prior art it has been found advantageous, in using an X-ray tube energized by a high tension transformer and having a heated cathode, to employ an auto-transformer connected with the line and energized thereby at the line voltage, and to provide the auto-transformer with taps from which alternating currents of any required voltage may be fed directly to the primary of the high tension transformer. lt f has also been found advantageous to place upon the core of the auto-transformer ank additional winding, separate from the other winding or windings thereof, and to use this additional winding to heat the cathode, usually a lament, of the X-ray tube. This arrangement resulted in an excellent stabilizing eect upon the voltage impressed upon the X-ray tube, and also enabled the operator to vary at will and practically independent of the current user for heating the filament, the voltage of the main discharge. 'This system is disclosed in my Patent No. 1,481,876, and is often used in connection with an equipment which includes a hot cathode valve tube in either the primary circuitor the secondary circuit, and also includes an X-ray tube located in the secondary circuit and provided with a cathode lament and circuit for heating the same.

I have made the discovery that in using LSE LEX

CFI

1926, Serial No. 161,012.

my system as just noted it is practicable to control, practically as a single unit, any or all of the circuits used for heating the cathodes, and that when the heating circuits are thus controlledas a unit the efficiency of the system is improved, the speed of operation is increased, the chances for a breakdown are diminished, and many other advantages are obtained.

have made the further discovery that in 6oA order to thus unify the control of a number of heating circuits for the purpose here contemplated, the circuits may be interconnected either directly or indirectly, as hereinafter ,more particularly described.

Reference is made to the accompanying drawings forming a part of this specifica-tion, and in which like reference characters indicate lilre parts throughout the several iigures.

Figure l is a diagram showing a form of 7o my invention in which two circuits, used for heating two cathode filaments, are interconnected and thus controllable practically as a unit.

Figure 2 is a diagram of another form of 75 my invention, in which a circuit for heating one filament is in series with the primary of a heating transformer the secondary of which is in series with another filament.

Figure 3 is a diagram of a third form, in which two separate filament heating circuits are controllable by a single switch common to both circuits.

A pair of power leads are shown at 4, 5, and are used for energizing an autotransformer 6, with which they are connected by wires 7, 8, 9, and sliding contact switch l0. The auto-transformer is provided with a variable contact switch ll. rlhe switches 10 and 11 are used, either individually or in co-relation as required, for controlling the output voltage of the auto-transformer- A high tension transformer appears at and here employed as the main transformer. It is energized by secondary currents e5 from the auto-transformer 6. For this purpose it is connected with the switch l1 by a wire i3, and also with the wires 8 and 9 by a wire let. A switch 12L is employed for opening and closing a circuit through the main 100 transformer, without disturbing the variable contact switch 11. The main transformer is provided with a primary winding 12b and two secondary windings 15 and 16.

5 A vacuum valve tube appears at 17, and is provided with a valve anode 18 and a cathode 19, the latter having the form of a filament adapted to be heated.

An X-ray tube is shown at 20, and is provided as usual with an anode 21 serving as a target, and with a cathode 22 in the form of a filament adapted to be heated.

A small transformer 23 is used to supply current for heating the cathode 19 of the valve tube 17. The secondary winding of the transformer is shown at 24, and by wires 25 and 26 is connected with the cathode 19. A wire 27 connects the cathode 19 with the secondary winding 15 of the main transformer, anda wire 28'extendsfrom the secondary winding 16 rof the main transformer to the anode 18'of the valve tube. A wire 29 is connected with the secondary winding 16 and with the cathode 22, and from the secw 2londary winding 15 and a wire 30 extends t0 the anode 21 of the X-ray tube.

A wire 31 is connected with the wire 29 and with the cathode 22. Wires 32 and 33 are connected with the wire 31. The wire 32 39leads to the primary 23" of the transformer 23, and from this primary av wire 34 leads to a rheostat`35. The auto-transformer 6 is provided with two secondaries 37 and 38,

Vwhich are independent of all other windings. 39?'The winding 37 is connected with the wire 36. The windings 37 and 38 are connected together and also connected with a wire 39. This wire leads to a variable switch 40, to which the wire 33 also leads.

A wire 41 leads from the secondary 38 to a rheostat 42, and from the latter a wire 43 leads to a ground connection 44. A wire 45 leads from the ground connection 44 and wire 43 to the cathode 22 of the X-ray tube 20.

The main transformer 12 is energized by currents from the auto-transformer 6. The vacuum valve tube 17 and the X-ray tube 2O are energized from the secondary circuit of the main transformer.

The heating of the cathode 19 is accomplished by secondary currents from the transformer 23, which is energized by currents from the secondary 37, and the cathode 22 is heated directly by currents from the second- 55"ary 38. Hence the two secondaries 37 and 38 supply all the current used for heating the two cathodes.

The rheostat controls the transformer 23, and hence in a general way regulates the' U9 volume of current supplied to the cathode 19.

The rheostat 42 regulates directly the supply 0f current to the cathode 22. However, the

rheostats 35 and 42 are not adjusted very often. They are set right` at the start, in

05 order to properly apportion the relative amount of current supplied to the respective cathodes 19 and 22, or in other words, to balance the heating currents relatively to each other, and this done, the rheostats 35 and 42 usually require no further attention, at least F until some substantial change is made in the wiring.

The switch 40 acts somewhat differently. It not only controls the transformer 23 and thus indirectly controls the heating current supplied to the cathode 19, but it also controls directly t-he current for heating the cathode 22. In other words the switch 40 is Common to both secondaries 37 and 38, and also to both cathodes 19 and 22. Hence if the two rheostats 35 and 42 are properly adjusted at the start, the switch 40 alone is adequate to take care of any and all changes required thereafter from time to time in the current supplied to the cathodes 19 and 22. This means, of course, that the number of milliamperes passing through the X-ray tube and used for the production .of X-rays can be varied within wide limits by merely actuating the single switch 40.

The circuit used for heating the cathode 19 may be traced as follows: Secondary windings 37 and 38 considered as in parallel with each other, wire 39, switch 40 to wire 33, whence the circuit divides; one branch being continued as wire 32, primary 23a wire 34, rheostat 35 and wire 36, back to secondaries 37 and 38; the other branch being continued from wire 33 to wire 31, cathode 22, and

thence back by wires 45 and 43 (grounded at 44), rheostat 42 and wire 41 to secondary windings 38 and 37.

In the form of my invention shown in Figure 2, the auto-transformer 6 is provided with a secondary winding 46, and a wire 47 extends from this winding to the cathode 19 of the valve tube 17. A wire 48, which is provided with a ground connection 49, leads from the cathode 19 to a variable switch 50, and from this switch a wire 51 leads to the primary winding 23n of the transformer 23. A wire 52 leads from the primary winding 23a to the secondary winding 46 of the autot-ransformer 6. A wire 53 is connected with the cathode 22 of the X-ray tube 20 to the secondary winding 24 of the transformer 23. A wire 54 leads from the cathode 22 to a variable switch 55, and from the latter a wire 56 leads to the secondary winding 24.

The cathode 19 of the valve tube 17 is heated directly by currents induced in the secondary winding 46, and these same currents euergize the primary winding 23EL of the transformer 23.

A circuit through the parts just mentioned may be traced as follows: secondary winding 46, wire 47. cathode 19, wire 48 with its ground connection 49 to switch 50, wire 51, primary winding 23n of transformer 23, and

wire 52 back to secondary winding 46. A circuit through the cathode 22 may be traced as follows: secondary winding 2-1, wire 53, cathode 22, wire 54, switch 55 and wire 56, back to secondary winding 24C.

The switch 55 is used merely to so adjust the circuit just traced as to apportion the current through the cathode 22 relatively to the current through the cathode 19. This done, practically once for all, the switch 50 alone is used for regulating, from time to time as required, the currents used for heating both cathodes 22 and 19. When the operator moves the variable switch 50 in one direction of its travel, both cathodes 22 and 19 are rendered hotter; and when the switch 50 is shifted in the opposite direction, the two cathodes are rendered less hot.

1n the form shown in Figure 3 there are some differences as to detail.

A wire 57 is connected with the secondary winding 46, and leads therefrom to the cathode 22 of the X-ray tube. From this cathode a wire 58 leads to a variable switch 59, and thence a wire 60 leads to a double switch 61. From this switch a wire 62 leads back to the secondary winding 46.

A wire 68 leads from the switch 61 to the primary winding 23EL of the transformer 23, and from the switch 61 another wire 64 extends to the lead 5. The wire 58 is provided with a ground connection 65. From the lead 4 a wire 66 extends to the primary winding 28a of the transformer 23. From the secondary winding 24 of this transformer a wire 67 leads to the cathode 19, and from the latter a wire 68 leads back to the secondary winding 24 of the transformer 23.

The sole use of the switch 59 is in adjusting or apport-ioning the current for heating the cathode 22, relatively to the current for heating the cathode 19; and this adjustment, once made, is permanent.

The double switch 61, however, is used for controlling, practically as a single unit, all of the circuits employed for heating the two cathodes 19 and 22.

The circuit for energizing tie primary of the transformer 23 may be traced as follows: lead 5, wire 64;, right hand portion of double switch 61, wire 63, primary winding 23a of transformer 23, and wire 66 to lead 4. The secondary circuit of the transformer .3 may be traced as follows: secondary winding 2e, wire 67, cathode 19, and wire 68 back to secondary winding 2i.

rlhe circuit for heating the cathode 22 of the X-ray tube 20 can be traced as follows: secondary winding 46 of the auto-transformer, wire 57, cathode 22, wire 58 with its ground connection 65, switch 59, wire 60, left hand portion of double switch 61, and wire 62 back to secondary winding 4G.

lt will be noted that in operating the double switch 61 the operator controls both cathodes 19 and 22. If at the start the switch 59 is properly adjusted, the control of the'double switch 61 over both cathodes is perfect and may be maintained for an indefinite period of time.

lt will also be noted that by means of my system a single regulator is used to control two vacuum tubes, the filament of one being maintained at Zero or ground potential and the filament of the other being subject to the highest potentials attainable in the system during operation.

lt is well lrnown to the artthat an X-ray tube operates at what is known as the saturation point or Zone while a vacuum tube, commonly utilized for rectification purposes, opcrates below this saturation point. Owing to this difference in operating characteristics, when it is desired to alter the discharge current flowing through the X-ray tube the ratio of heating current supplied to the cathode of the X-ray tube must of necessity be greater than that supplied to the vacuum or rectier tube. By the novel arrangement of my control system the heating current supplied to the cathode of both discharge devices is simultaneously varied and the current supplied to the X-ray tube is readily varied to a greater extent than that supplied to the other discharge device. rl`his maintains the correct ratio of heating currents between the two discharge devices over the entire operating range and compensates for the diiference in operating characteristics between the two discharge devices.

I do not limit myself to the precise mechanism shown, as variations may be made therein without departing from my invention, the scope of which is commensurate with my claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is as follows:

1. ln a control system for X-ray tubes, the combination with a plurality of thermionic discharge devices provided with cathodes to be heated, one of said discharge devices being an X-ray tube, of a main transformer for supplying energy to the electrodes of said devices, an auto-transformer connected to a suitable source of electrical energy provided with a plurality of windings for energizing said main transformer and for supplying heating current to the cathode of one of said devices, a heating transformer for supplying heating currents to the cathode of the other of said devices, a ground connection for one of said cathodes and means for varying the currents for heating the cathode of the X-ray tube to agreater extent than the currents for heating the cathode of any other discharge device.

2. In a control system for X-ray tubes, the combination with a plurality of thermionic discharge devices provided with cathodes to be heated, one of said discharge devices being an X-ray tube, of a inain transformer for supplying energy to the electrodes of said devices, an auto-transformer connected to a suitable source of electrical energy for energizing said inain transformer, an auxiliary Winding carried by said auto-transformer for supplying heating current to the cathode of one of said discharge devices, a low tension transformer having its primary Winding connected to said auxiliary winding for supplying heating current to the cathode of the other of said discharge devices, a ground connection for the cathode of one of said devices, and regulating means for simultaneously varying the current supplied by the auxiliary winding of said auto-transformer and said lov.'v tension transformer to the cathodes of said discharge devices.

Signed at Long Island city, in the county of Queens and State of New York, this 23th day of April, 1926.

ARTHUR MUTSGHELLER.

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