US3450880A

US3450880A - Arrangement for the separate regulation of the tube currents for a plurality of x-ray tubes

Info

Publication number: US3450880A
Application number: US505316A
Authority: US
Inventors: Bruno Mook
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1964-12-03
Filing date: 1965-10-23
Publication date: 1969-06-17
Anticipated expiration: 1986-06-17
Also published as: DE1439482A1; GB1077569A; NL6514759A; FR1456305A

Description

June 17, 1969 oo 3,450,880

ARRANGEMENT FOR THE SEPARATE REGULATION OF THE TUBE CURRENTS FOR A PLURALITY OF XRAY TUBES Filed Oct. 23, 1965 Sheet J W3 s V I FIQE-JZ x1 I I 'qul M1 HT1 7 w ST1 B1 i v M W ST INVENTOR June 17, 1969 B. MOO 3,450,880

ARRANGEMENT FOR THE SEPARATE REGULATION OF 'THE TUBE CURRENTS FOR A PLURALITY OF X-RAY TUBES Filed Oct. 23, 1965 Sheet 3 of s X }-r i I Flg 3 ?1 I I on. l D w 5T1 l vPR' A XZ 2 HT 5T2 z FRZ LT HT T Q1 x1 c I l f 1 1 ST l 1 q R1 L I N V E NTO R flea/v0 MopK ATTORNEYS June 17, 1969 5 3,450,880

ARRANGEMENT FOR THE SE'P .MOO ARATE REGULATION OF THE TUBE CURRENTS FOR A PLURALITY OF X-RAY TUBES Filed Oct. 23, 1965 Sheet 3 of 3 IN VE NTOR 5ZUA/O Mack BY M ATTORNEYS United States Patent Int. Cl. nos 1/70 US. Cl. 250-94 8 Claims ABSTRACT OF THE DISCLOSURE An arrangement for the regulation of individual X-ray tubes which are fed from a single high-voltage source and which X-ray tubes have their anodes connected to ground potential. A setting member is connected with each of the X-ray tube circuits and responsive to the X-ray tube current to control a filament transformer also associated with each X-ray tube. A transducer is connected in series with the cathode of each of the X-ray tubes for sensing the current flow through the X-ray tube. Connected to each of the transducers is a regulating device which, in turn, is connected to the setting member for controlling the current flow through the X-ray tube in response to a value selected by the setting member.

A certain measured value has been necessary for an automatic regulation of the X-ray tube current, and dependent on the tube current, for an X-ray apparatus known in the past. The actual value of the regulating magnitude is tapped from a resistor situated on the ground side of the high-voltage circuit. This relatively simple method for obtaining the actual value of the regulating magnitude on the ground side of the high-voltage circuit is possible only in the operation of one X-ray tube. Since in general the X-ray tubes in question operate with grounded anodes and the anodes are cooled with water, a shunt circuit is provided for the cooling in parallel operation of several tubes, making it impossible to exactly obtain the tube current of the individual tube on the grounded anode side.

There is a possibility of circumventing this difficulty by arranging an equal number of secondary windings in the high-voltage generator for several X-ray tubes. The winding end not connected to high-voltage potential can then be connected to ground via a resistor. The resistor can serve as a measuring resistor for a current proportional voltage value. This solution requires, as already mentioned, a separate secondary winding on the highvoltage transformer for each of the tubes to be operated.

In order to avoid this expenditure and not have the main part of the regulating device for the tube currents connected to high-voltage potential, a system for the separate regulation of the tube currents of several X-ray tubes fed from a high-voltage generator is constructed according to the invention in such a way that only one well insulated part of the measuring sensors and of the setting members of the regulating devices for the tube currents are placed on high-voltage potential, and all the other members of the regulating devices are placed at ground potential.

By means of the system according to the invention, the shunt circuits existing through the water cooling of the grounded anodes become inconsequential for the measuring of the individual tube currents, because the actual value of the regulating magnitude is taken on the high-voltage side which is connected to the cathodes of the X-ray tubes. Nevertheless, insulation difficulties are avoided, because a separation is made between highvoltage potential and ground potential in the measuring sensor, so that the greater portion of the regulating circuit is connected to ground potential.

A heating transformer can be used for heating the cathode of the X-ray tube, as a setting member for the regulating device. The primary voltage is delivered from the regulating device. The cathode heating is operated with the voltage from the secondary winding. In the case of X-ray tubes with a Wehnelt cylinder or a control grid, these electrodes can serve as setting members for regulation of the tube current.

In general, it is expedient to arrange grounded potential screens between the high-voltage conducting and the ground side parts of the regulating magnitude.

In different examples of operation of the invention, various measuring sensors are used. Thus, a transducer whose direct current winding is in the high-voltage circuit of the individual X-ray tube can serve as a measuring sensor. The direct current winding is highly insulated with respect to the core of the transducer which is connected to ground potential.

In another example of the operation of the invention, a magnetic field dependent resistor which is arranged in the air gap of a magnet yoke whose field winding lies in the X-ray tube circuit can serve as a measuring sensor. The field windings are highly insulated with respect to the magnet yoke, which is connected to ground potential.

In another example of the operation of the invention, a high-voltage divider is arranged on the high-voltage side. One member of this divider is formed by a resistor controlled by the X-ray tube current. It is possible to tap a control voltage for the regulation of the X-ray tube cathode heating on the low-voltage side of the divider. The resistor in the high-voltage divider circuit can be a high vacuum diode heated by the X-ray tube current and controlled by the tube current. Another solution is to provide a grid-controlled high vacuum tube whose cathodeanode interval serves as a controlled resistor. One control grid of this tube is connected to a measuring resistor in the X-ray tube circuit. A transistor can be used in place of the grid-controlled tube. The emitter collector interval serves as a resistor dependent on the X-ray tube current.

The invention is explained in detail with the aid of five figures which represent examples of the operation. In the figures, like structural parts are provided with the same reference characters.

FIGURE 1 is a schematic wiring diagram of an X-ray circuit according to the present invention;

FIGURE 2 is a schematic wiring diagram showing an alternate form of the X-ray circuit of FIGURE 1;

FIGURE 3 is a schematic wiring diagram showing an alternate form of the X-ray circuit of FIGURE 1;

FIGURE 4 is a schematic wiring diagram showing still another alternate form of the X-ray circuit of FIGURE 1; and

FIGURE 5 is a schematic wiring diagram showing yet another form of the X-ray circuit of FIGURE 1.

In FIG. 1, a high-voltage transformer is designated with T which is connected to a rectifier bridge G1, A capacitor C is provided as a filter. The plus pole of the high voltage bridge is grounded. The minus pole of the bridge is connected via windings W W and W of transducers TK to TK with the cathodes of three X-ray tubes X to X The anodes of the X-ray tubes are connected to ground potential. Control windings of the transducers TK to TK are connected to regulators R to R The outputs of regulators R to R via setting members ST to ST regulate the primary current in the primary windings of heating transformers HT t-o HT for the heating 3 of the cathodes of the X-ray tubes. The number of X-ray tubes to be operated in parallel in this manner is dependent only on the power of the high-voltage generator.

In FIG. 2, magnet yokes M and M whose exciter winding or field winding is traversed by X-ray tube current on the high-voltage side, take the place of the transducers. The iron of the yoke, as well as the core of the transducers, is grounded in the operation according to FIG. 1. Field dependent resistors FW and FW which are components of a bridge circuit B or B respectively, are arranged in the air gap of the magnet yokes. The output voltages of the bridges control via setting members 5T and 8T (again in accordance with the operation as shown in FIG. 1) the primary current of heating transformers HT, and HT which supply the heating power for the cathode heating of the X-ray tubes. The secondary windings of the heating transformers are connected to high-voltage potential and are highly insulated against the cores of the heating transformers connected to ground potential.

In the examples of the operation according to FIG. 3, the input voltage for the regulators R and R is tapped at resistors P and P respectively. These resistors ar a component of a high voltage divider circuit, having vacuum diodes D and D connected to high voltage. The cathodes of the vacuum diodes D and D are heated by the X-ray tube currents. The internal resistance of the diodes is thus dependent upon the X-ray tube current. Therefore, the input voltage for the regulator, which is tapped at the resistors P and P becomes dependent upon the X-ray tube current.

In a futher example of the operation according to FIG. 4, the vacuum diodes are replaced by grid-controlled vacuum tubes R6 and R6 The control voltage of these tubes is tapped at resistors Q and Q respectively, which carry the X-ray tube currents. A special heating transformer HT provides the heating power for the tuges R6 and R62- In an example of the operation execution according to FIG. 5 the grid-controlled high vacuum tubes are replaced by transistors Tr and Tr as components of high voltage divider circuits. The emitter-collector regions of the transistors serve as resistors dependent on X-ray tube current in the voltage dividers. The control voltage for the transistors is regulated by means of resistors Q and Q connected in the X-ray tube current circuit. In the examples of the operation according to FIGS. 2 to 5, more than two X-ray tubes can be operated in parallel on a highvoltage generator.

The regulators R R and R may be of any suitable design to produce a control voltage which is maintained in accordance with the setting members 5T ST and ST;; respectively. One such regulating device is shown in the patent to W. E. Splain 3,325,645 and is designated MA stabilizer. Additionally, the setting members ST ST and 8T are used to select the desired amount of current flow through each of the associated X-ray tubes X X and X respectively. One such setting member which can be used in accordance with the principles of this invention is shown in the patent to C. W. Clapp et al. 2,810,838. Accordingly, neither the regulating members R R and R nor the setting devices 8T ST and 8T in themselves form a part of this invention.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desire to have protected by Letters Patent.

I claim:

1. An arrangement for the separate regulation of a plurality of X-ray tubes which are operatedfrom a single high-voltage source, comprising: a high-voltage source; a plurality of X-ray tubes each having their anode connected to ground potential and their cathode connected to said high-voltage source, each of said X-ray tubes having a heater filament; a plurality of filament transformers, each filament transformer having its secondary winding connected to the heater filament of its associated X-ray tube, and further having a primary winding; a control circuit connected to each of said X-ray tubes to control the amount of heating current applied to the associated heating filament, each of said control circuits including, electromagnetic sensing means including an electromagnetic transducer having a winding which is insulated from ground potential and connected in series with the cathode circuit of the associated X-ray tube operative to sense the actual amount of direct current passing through said winding and thus through the X-ray tube, a setting member for selecting a desired amount of current to pass through the associated X-ray tube, regulator means connected between said sensing means and said setting member to compare the actual amount of current passing through the associated X-ray tube with that of the desired amount of current thereby producing a control voltage, and circuit means connecting the primary winding of said filament transformer with said regulator means, whereby, said control voltage will control the amount of heating current applied to the heater filament of the associated X-ray tube.

2. An arrangement for the separate regulation of a plurality of X-ray tubes which are operated from a single high-voltage source, comprising: a high-voltage source; a plurality of X-ray tubes each having their anode connected to ground potential and their cathode connected to said high-voltage source, each of said X-ray tubes having a heater filament; a plurality of filament transformers, each filament transformer having its secondary winding connected to the heater filament of its associated X-ray tube, and further having a primary winding; a control circuit connected to each of said X-ray tubes to control the amount of heating current applied to the associated heating filament, each of said control circuits including, sensing means connected in series with the associated X- ray tube for sensing the actual amount of direct current passing through the X-ray tube, a setting member for selecting a desired amount of current to pass through the associated X-ray tube, regulator means connected between said sensing means and said setting member to compare the actual amount of current passing through the associated X-ray tube with that of the desired amount of current thereby producing a control voltage, circuit means connecting the primary winding of said filament transformer with said regular means, whereby, said control voltage will control the amount of heating current applied to the heater filament of the associated X-ray tube, said sensing means being formed by a field winding of a magnetic yoke and further including a magnetic field dependent resistor responsive to the magnetic field produced by said magnetic yoke, said magnetic field dependent resistor being connected to said regulator means.

3. An arrangement for the separate regulation of a plurality of X-ray tubes according to claim 2 wherein said magnetic yoke is connected to ground potential.

4. An arrangement for the separate regulation of a plurality of X-ray tubes which are operated from a single high-voltage source, comprising: a high-voltage source; a plurality of X-ray tubes each having their anode connected to ground potential and their cathode connected to said high-voltage source, each of said X-ray tubes having a heater filament; a plurality of filament transformers, each filament transformer having its secondary winding connected to the heater filament of its associated X-ray tube, and further having a primary winding; a control circuit connected to each of said X-ray tubes to control the amount of heating current applied to the associated heating filament, each of said control circuits including, sensing means connected in series with the associated X-ray tube for sensing the actual amount of direct current passing through the X-ray tube, a setting member for selecting a desired amount of current to pass through the associated X-ray tube, regulator means connected between said sensing means and said setting member to compare the actual amount of current passing through the associated X-ray tube with that of the desired amount of current thereby producing a control voltage, circuit means connecting the primary winding of said filament transformer with said regulator means, whereby, said control voltage will control the amount of heating current applied to the heater filament of the associated X-ray tube, said sensing means including the filament of an electron tube connected in series with the direct current of the associated X-ray tube, the conduction of said electron tube being proportional to the current passing through said X-ray tube, and a voltage divider connected in series with said electron tube, the output of said voltage divider being connected to said regulator means.

5. An arrangement for controlling the separate regulation of a plurality of X-ray tubes according to claim 4 wherein said electron tube is a diode.

6. An arrangement for the separate regulation of a plurality of X-ray tubes which are operated from a single high-voltage source, comprising: a high-voltage source; a plurality of X-ray tubes each having their anode connected to ground potential and their cathode connected to said high-voltage source, each of said X-ray tubes having a heater filament; a plurality of filament transformers, each filament transformer having its secondary winding connected to the heater filament of its associated X-ray tube, and further having a primary winding; a control circuit connected to each of said X-ray tubes to control the amount of heating current applied to the associated heating filament, each of said control circuits including, sensing means connected in series with the associated X-ray tube for sensing the actual amount of direct current passing through the X-ray tube, a setting member for selecting a desired amount of current to pass through the associated X-ray tube, regulator means connected between said sensing means and said setting member to compare the actual amount of current passing through the associated X-ray tube with that of the desired amount of current thereby roducing a control voltage, circuit means connecting the primary winding of said filament transformer with said regulator means, whereby, said control voltage will control the amount of heating current applied to the heater filament of the associated X-ray tube, said sensing means including a resistor connected in series with the current passing through the associated X-ray tube, and a variable conduction device connected to said resistor, and a voltage divider network connected to said variable conduction device, said voltage divider network having the output thereof connected to said regulator means.

7. An arrangement for the separate regulation of a plurality of X-ray tubes according to claim 6 wherein said variable conduction device is an electron tube.

8. An arrangement for the separate regulatiOn of a plurality of X-ray tubes according to claim 6 wherein said variable conduction device is a transistor.

References Cited UNITED STATES PATENTS 2,810,838 10/1957 Clapp et a1. 250-103 2,838,681 6/1958 Graves et a1. 250 94 2,864,958 12/ 1958 Morrison 25094 3,325,645 6/1967 Splain 25O103 RALPH G. NILSON, Primary Examiner. A. L. BIRCH, Assistant Examiner.

US. Cl. X.R.