US2053587A - X-ray installation - Google Patents

Description

Sept. 8, 1936. A. VAN DEN BERG X-RAY INSTALLATION 1 Filed Jan. 25, 1953 Patented Sept. 8%, 1936 D STATES X-RAY INSTALLATION Aart van den Berg, Eindhcvcn, Netherlands, as-

signor, by mesne assignments, to N. V. Philips Gloeilampenfabrieken, Eindhcven, Netherlands,

a Dutch company Application January 25, 1933, Serial No. 653,501 In Germany February 8, 1932 7 Claims.

My invention relates to a novel circuit arrangement and controlling means for X-ray in stallations and more particularly for the taking of short-exposure X-ray pictures.

In taking X-ray pictures the results obtained are dependent in the main onthree factors, namely, the voltage applied to the X-ray tube, the current through the tube, and the time of exposure. It is well-known to vary the voltage applied to an X-ray tube and to adjust the voltage before the load is applied to the tube. Similarly it is known to provide a time-switch by means of which the loading of the tube takes place for a predetermined time interval, and adjust such switch to the required exposure time.

It is also known to vary the current passing through the X-ray tube, for instance, by inserting resistances in the heating circuit of the incandescible cathode, so as to accordingly vary 20 the electron emission of the cathode and thus obtain diiierent operating currents.

It is evident that the use of three separate and independent adjusting means is very cumbersome. Furthermore in order to obtain the most 25 suitable combination in each case specific selection has to be made, which renders it extremely difilcult if not impossible to reliably obtain high quality exposures.

Under practically any condition the best results in short-time exposure X-ray photography are obtained if the X-ray tube is loaded to sub stantially its maximum capacity, because the exposure time can then be kept as short as possible and the focal spot as small as possible, and this leads to pictures having the best definition. This is especially marked in the case of pictures made of moving objects.

In a copending application, of Albert Bou- -wers and Willem H. Boldingh, Ser. No. 653,538, filed January 25, 1933 there have been described certain arrangements and methods of operation whereby a variable load is applied to the'tube at a substantially constant voltage and with a decreasing current, and which permits an X-ray tube to be loaded to practically its full capacity.

Thereby the current is raised initially much in excess of that admissible for a continuous load and the current thereafter decreased in such a way that the anti-cathode temperature during the whole loading remains substantially constantv and preferably at a value which is substantially equal to its maximum permissible operating temperature.

My present invention has for its object to 9 make X-ray photographs of high quality with the shortest possible exposure time.

Another object of my invention is to dispense with the adjustment of three difierent and independent adjusting means and to facilitate the adjustrnent of the operating conditions.

Another object of my invention is to provide means that prevent overloading of the X-ray tube.

According to the present invention I provide an adjusting device for the terminal Voltage of the X-ray tube, an adjusting device for the loading time and two control devices for the current passing through the tube and interlock one of said control devices with the adjusting device for the voltage and the second control device with the adjusting device for the loading time, so that for given voltage applied to the tube, the current passing through the tube is larger for a shorter loading time than for a longer loading time, and for a given time of loading the current is larger for smaller operating voltages than for larger operating voltages.

The operating current may be varied for different voltage adjustments and for different loading times by varying the heating current of the incandescible cathode, for instance, by automatically inserting in the heating circuit resistances of the proper value.

My invention can be applied to X-ray installations in which the energy is constant during the exposure or shows periodical pulsations due to alternating current supply. It may be carried into effect with advantage in such a manner that the number of watts applied to the tube remains substantially constant irrespective of what the adjustment of the voltage may be. Thereby preferably the number of watts is so selected that the tube is loaded substantially to the limit of its load-carrying capacity. Under such conditions the exposure may be automatically obtained inthe shortest possible time .of exposure irrespective of the voltage applied to the tube, which voltage is to be selected in accordance with the conditions and special problems presented by the object to be photographed.

According to one particular feature of. my invention one of the control means for the heating current is constituted by a regulating resistance included in :the heating current circuit and the other is a. variable voltage supply for this circuit.

The invention will be more fully explained by reference to the accompanying drawing inwhich:

Figure 1 is a circuit diagram of an X-ray installation according to my invention,

Fig. 2 is a perspective view showing the interlocking parts of a time-switch and of a voltage regulator for the heating transformer.

In the arrangement shown in Fig. 1 an X-ray tube I is provided with an incandescible cathode 2 and an anode 3. 5 represents the alternating current network to which conductors 6 and I are connected through a switch 8. For heating the cathode there is provided a low voltage transformer 9; the secondary winding of which is connected across the cathode, whereas one end of the primary winding is connected to the conductor I and its other end is connected to one end of a variable resistance III. 7

The operating voltage for the X-ray tube is supplied by a high voltage transformer II, the secondary winding of which is connected across the cathode 2 and the anode 3, whereas one end of the primary winding is connected to the conductor I and its other end is connected through a time switch I2 of any suitable design to a contact I3 which will be referred to hereinafter.

The time switch is provided for adjusting the load period. For the adjustment of the operating voltage and the operating current of the tube, control means are provided which in the preferred embodiment of the invention shown and described herein permit the simultaneous and corresponding adjustment of the primary voltage of the rotatable control cylinders A and A provided on a common shaft and shown developed schematically in the drawing. If desired, the two control cylinders A and A may form a single cylinder.

The upper cylinder A controls the voltage of the transformer II by connecting the primary winding of the transformer with selected taps of an auto-transformer I4.

' The auto-transformer I4 is provided with a plurality of taps I6, I'II, I8, I9, and 2I, and is connected with its end I5 to the conductor I and thus to one end of the primary winding of transformer I I and is connected with a tap I8 to the conductor 6. The taps I6 to 2I of the autotransfo-rmer are connected to corresponding stationary contacts 22 to 2'! which cooperate with individual contacts 28 to 33 of the cylinder A.

The contacts 28 to 33 are so staggered on the cylinder A, that in the various active positions thereof, marked I to VI, one of the contacts 28 to 33 engages its corresponding contacts 22 to Aligned with the stationary contacts 22 to 21 is an additional stationary contact I3 which is connected through the time switch I2 to the free end of the primary winding of transformer II. The contact I3 cooperates with a contact strip 34, of the cylinder A which strip engages the contact I3 in all active positions of the cylinder A. The contacts 28 to 33 are electrically connected with the contact strip 34.

It will thus appear that depending on the position of the control cylinder A, a smaller or larger voltage will be applied to the primary winding of high-voltage transformer II. For instance, to apply the lowest operating voltage, the cylinder A is brought in the position I, whereby when switch 8 and the time switch I2 are closed the voltage on the primary winding of transformer I I is obtained as follows:

Through closure of switch 8 a primary voltage is applied to the auto-transformer I4 between I5 winding is and I8, and a secondary voltage corresponding to its portion I5 to I6 is applied to the primary winding of transformer II. The primary winding of transformer I I is thereby connected with one end directly to terminal I5 and with its other end to the transformer tap I6, via contacts 22 and 28, strip 34, contact I3 and time switch I2.

The control cylinder A which is rotated simultaneously with the control cylinder A is provided for the control of the operating current of the X-ray tube by means of varying the heating current of the cathode and may be similar in construction to cylinder A; being provided with a contact strip 35 and staggered contacts 36 to 4| electrically connected thereto.

The strip 35 cooperates with a stationary contact 42 connected to the conductor 33 and the contacts 36 to 4| cooperate with stationary contacts 44 to 49 connected in their turn to taps 50 to of the resistor I0.

As it will be noted, by bringing the control cylinder A into its different positions, a. varying amount of resistance will be inserted in series with the primary winding of the heating transformer 9. The amount of resistance thus inserted, however, depends on the operating voltage applied to the tube, whereby the lower the operating voltage the less will be the resistance and thus the larger will be the heating current of the cathode, its electron emission and the operating current of the X-ray tube.

For instance, when the cylinders A and A are brought in the position II, and thus the operating voltage is slightly in excess of the minimum operating voltage which can be applied to the X-ray tube, a comparatively small resistance corresponding to the portions 50 to 5I of the resistor I3 is inserted in the circuit of the primary winding of transformer 9. The circuit of this as follows. From conductor I through primary winding of transformer 9, resistor. tap 50, through part or" resistor I0, resistor tap 5|, stationary contact 45, movable contact 31, contact strip 35, stationary contact 42, through conductor 43 to the control arm of a regulator 55, the contacts of which are connected with taps of an-autotransformer 51. The portion between one end 58 of the winding of this autotransformer and the tap 59 thereof is connected across the conductors 6 and I.

The end 58 of the winding is connected to conductor I and one end of the primary winding of the heating transformer 9.

The time-switch I2 and the regulator 53 are mechanically interlocked in such a manner that 1 the voltage supplied to the, primary winding of the transformer 9 by the autotransformer 51 becomes smaller when the time switch is adjusted to give a longerloading time, and becomes larger when the time switch is adjusted to give a shorter time. I

The interlocking of the time-switch I2 with the regulator 53 can be achieved in various ways, one form being illustrated in Fig. 2. The shaft 69 of the arm of regulator 53 carries a disc 6& and is normally biased by means of a spring BI in that 4 responding position. Thereby the shaft 63 carries with it by means of the extension 64 and the pin 62, the disc Gil, and thus also the regulator arm 56 which is then locked in the selected position by means of the cam 66 which engages the then opposing notch 65. 7

During the exposure the shaft 63 is gradually returned by the action of the clockwork of the time-switch to its initial position. However, the regulator 55 is retained in its position by the action of the cam 66 engaging the recess 65 and remains in this position until at the. end of the exposure when the extension 64 reaches the cam 66 and lifts it out of engagement with the recess 65. This now permits the spring iii to return the arm of the regulator 55 to its initial position. Thus the regulator is again in its normal position and may assume for the next loading any desired position determined by the next time adjustment.

It should be noted that preferably the notches of the disc 66 and the contacts of the regulator 55 correspond to that of the time switch. If by an inaccurate manipulation the pin 54 should carry the disc 60 slightly beyond a position in which the arm 56 properly contacts with the corresponding conductor, the spring 6! moves the arm of the regulator 56 counterclockwise. until the cam 56 engages the nearest notch 65, the hand knob of the time-switch being at the same time brought back by the driving spring of that switch to the corresponding position.

As appears, two adjustments are provided for the heating current, one. depending on the operating voltage, this being automatically adjusted by the interlocking of the controllers A and A with the taps of the auto-transformer is and the taps of the resistor l0 respectively, the second depending on the loading time of the tube, this being automatically adjusted by the interlocking of the time-switch l2 and regulator 56. Thus the operating current through the tube is reduced both when the operating voltage is increased, as well as when the exposure time is increased.

The adjustment is preferably such that for any operating voltage and exposure time the amount of energy supplied to the tube is such that at the end of the loading period the maximum admissible anode temperature is obtained. This permits the tube to be utilized to its maximum extent.

In that way the admissible loading is greatly increased for short-time exposures and for low voltages. For instance, for a given tube of a voltage of 80 kilovolts a current of 15 milliamperes may be applied for an exposure time of 2 seconds. At the same voltage the current may be 25 milliamperes for an exposure time of 1 second, 45 milliamps for .2 second and 65 milliamperes for .1 second. If the voltage is only 60 kilovolts the currents for the corresponding times can be 20, 33, 60 and 85 milliamperes respectively. I

While I have described a specific example of an X-ray installation embodying my invention, it should be well understood that'my invention is not limited to this example, and modifications may suggest themselves within the scope of my invention. Therefore I desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I now claim as new and desire tosecure by Letters Patent is:

1. An X-ray installation for making shorttime exposures comprising an X-ray tube having an anode and an incandescible cathode, a hightension step-up transformer having a primary winding and a secondary winding, a high-tension circuit including said secondary winding and said tube and a low-tension circuit comprising. said primary winding and a switch operated by a timeadjusting device to adjust the loading time of the tube, means including a regulating transformer forming part of said low-tension circuit and a voltage selector cooperating therewith for adjusting the voltage applied to said step-up transformer, means for supplying energizing current to the cathode including two separate devices for regulating the energizing current, one of said devices being interconnected with the time-adjusting device whereby less current is supplied according as the adjusted time is longer, the other regulating device being interconnected with the said voltage selector whereby less current is supplied according as higher voltages are applied to the step-up transformer.

2. An X-ray installation comprising an X-ray tube having an anode and an incandescible cathode, means for selecting the amount of the operating voltage applied between said anode and cathode, means for adjusting the loading time of the tube, a source of energizing current for said cathode, means for regulating the voltage of said source, said voltage regulating means being interconnected with said means for adjusting the loading time of the tube, a variable resistance connected in series with said source and means to vary said resistance interconnected with the means for selecting the voltage applied between the anode and cathode of the X-ray tube.

3. An X-ray installation comprising an X-ray tube having an anode and a cathode, a hightension transformer and a heating transformer, means for selecting the input voltage applied to said high-tension transformer, means for controlling the time of energiz-ation of said hightension transformer, two separate devices for regulating the power supplied to said heating current transformer, one of said devices being interconnected with the voltage selecting means, and being operated thereby, the other of said devices being interconnected with the time controlling means and being operated thereby, said means and devices providing for a regulation of the current through the X-ray tube whereby for a given loading time of the tube, the current through the tube increases with decreasing voltages, and for a given voltage the current increases with decreasing loading time of the tube, and independently of the operating voltage and. of the time of loading, the tube is loaded to substantially its maximum load capacity.

4. An X-ray installation comprising an X-ray tube having an anode and an incandescible cathodef'a high-tension supply device for said X-ray tube, a low-tension input circuit for said supply device including a control device to control the input voltage of said supply device and a second control device to control the loading time of the X-ray tube, a high-tension output circuit for said supply device including said X-ray tube, a heating circuit for said cathode including said cathode, a variable resistance and a voltageregulating device interlocked with one of said control devices, and means to vary said resistance, said means being interlocked with the other of said control devices.

5. An X-ray installation comprising an X-ray tube having an anode and an incandescible oathode, a high-tension supply device for supplying the operating voltage to said X-ray tube, a heating current supply device for said cathode, means to select the operating voltage of the tube, means to adjust the time during which the selected operating voltage is applied to the tube, two separate regulating devices connected to said vheating current supply device for regulating the current intensity through the 'X-ray tube, one device being interconnected with the voltage-selecting means and the other device being interconnected with the time-adjusting means, whereby for a given selected operating voltage the current through the X-ray tube increases with decreasing time of application of the operating voltage and for a given time of application of the operating voltage the current through the tube decreases with increasing operating voltage, said means and regulating devices providing for loading said tube to the limit of its load-carrying capacity, irrespective of the select values of the operating voltage and of the exposure time.

6. An X-r-ay installation comprising an X- ray tube having an anode and an incandescible cathode, a, device for energizing said cathode, a

second device for supplying high operating voltage to said X-ray tube, means to vary the amount of said operating voltage, means to vary the loading time of the tube, and two devices to vary the discharge current through said tube, each of said two devices being interconnected with and operated in conjunction with one of said means.

'7. An X-ray installation comprising an X-ray tube having an anode and a cathode, means for supplying high operating voltage tosaid tube including a, device for adjusting the amount of the operating voltage and a second device for adjusting the time the operating volt-age is applied to the tube, and means for varying the discharge current of the X-ray tube, said two devices being so interconnected with said latter means that for any adjustment of the devices the X-ray tube will be loaded substantially to its full capacity.

AART VAN DEN BERG.

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