US2594564A - Revolving anode roentgen ray tube - Google Patents

Description

April 1952 H KEHRLI 2,594,564

REVOLVING ANODE ROENTGEN RAY TUBE Filed June 6, 1950 11y VENT'OQ HANS IZEHRL m G J W A TTORAIE Y5 Patented Apr. 29, 1952 UNITED STATES PATENT OFFICE REVOLVING ANODE ROENTGEN RAY TUBE Hans Kehrli, Zurich, Switzerland Application June 6, 1950, Serial No. 166,429 In Switzerland December 16, 1948 This invention relates to Rbntgen or X-ray tubes.

In Rt'mtgen-ray tubes it is known to provide a revolving anode to reduce overheating of the anode material by the cathode rays, which strike the anode material. The X-rays from the anode are, in the use of a direct current, of steady uninterrupted radiation and in the use of alternating current of pulsating radiation according to the frequency employed.

In certain cases, as for example with apparatus for stereoscopic views of the bodies penetrated by Rijntgen rays, an intermittent or pulsating radiation is required from two sources of X-rays which are alternately radiated upon the body which is to be investigated. In this case, by the use of alternating current, the available frequency is exploited producing however no satisfactory result, several reasons being responsible for this behaviour. One main reason.

is that at the sequence of the'various images in time intervals of one hundredth of one second, the sequently produced images due to the afterglow of the screen appear at times simultaneously in that one image since the after-glow is still visible when the other image is about to appear.

It is known to apply two separate X-ray tubes side by side in conjunction with separately driven apertured plates, which are disposed outside of the tubes. This, however, is inherently disadvantageous in that, firstly, the distance to the anode cannot be made as small as might be desirable, and secondly, in that it is difficult to synchronize the forthcoming of the X-rays with the rotation of the apertured plate. Similar difficulties are involved with revolving anode X-ray tubes provided with two anodes, and also by tubes with two stationary anodes. In this case, the disposition of the anode plates in front of the tubes causes considerable difficulties, because radiation is disadvantageously influenced thereby.

The present invention is concerned with a revolving anode X-ray tube which is characterized by a revolving apertured plate disposed in the inner space of the tube in which the frequency of radiation from the anode is determined by the rotational speed of the apertured plate.

The appended drawing shows the subject matter of this invention in the way of an example. In the drawing is:

Fig. 1 a schematic illustration in longitudinal section of the invention,

Fig. 2 shows the apertured disc in front view.

Fig. 3 is the diagram of connections for the X-ray' tube.

' 4 Claims. (Cl. 313--56) In the bulb l which is of glass or any other suitable material, there are fastened, by means of brackets 2, a cylindrical piece 3 and sleeve supports 4 and 5 for the shaft bearing 6 of the revolving anode H. The brackets 2 may be secured to the bulb in any suitable manner, e. g. they may be cast to the bulb. The shaft 6 of the revolving anode may be journalled in ball bearings disposed in the sleeves 4 and 5.

At the end of the shaft 6 in the enlarged portion of the bulb I, the revolving anode I1 is fitted, the anode consisting of a disc, the edge of which is as well known formed in such manner that the striking cathode rays are reflected in the desired direction. In the plane of the disc diametrically opposed, there are placed two cathodes 1 and 8.

An apertured disc 9 of circular form is also fastened upon the shaft 6 of the revolving anode, the disc comprising a concave annular outer portion 9a. The apertured disc 9 has a cut-out sector l0 through which at rotation of the apertured disc an X-ray beam is emitted.

The revolving anode ll including the shaft 6 and the apertured plate 9 are driven by a synchronous motor H disposed in the inner space of the tube.

By the rotational speed of the apertured plate 9 and the number of cut-out sectors It, the frequency of the X-ray radiation from the anode I! is determined. The size of one or several cut-out sectors In in the apertured disc 9 determines the period of radiation. In the case of the embodiment shown, the rotational speed of the revolving anode and apertured disc is 1500 revolutions per minute, the apertured disc therefore executes in one twenty-fifth of one second a full revolution, and at the frequency of fifty cycles of the alternating current each anode produces in each one twenty-fifth of one second one X-ray beam.

Each source of X-ray radiation produces therefore images upon the screen in intervals of one twenty-fifth of one second, whereby the images of both sources follow each other in time intervals of one fiftieth of one second. The duration of radiation is thereby one hundredth of one second.

Hence, the time sequence of the images following each other is independent of the frequency of the net current and the images are more suitably conditioned to be readily viewed by the reproducing devices, and are notably more adequately adapted for illustration tov the peculiar qualities of the human eyes.

The described time sequence has proven to be particularly suitable in regard to the reproduction of stereoscopic images and in regard to the suppression of after-glow upon the screen. It is understood that by regulation ofthe rotational speed of the revolving anode and apertured disc the time sequence of the images may be changed within certain limits. Instead of the two cathodes, as provided for the present embodiment, a single cathode may be used also. By the use of the X-ray tube with only one cathode for the reproduction of stereoscopic images of bodies penetrated by X-rays, a second X-ray tube must be employed. This second tube must have the same characteristics as the one already described. Such an arrangement permits changing the distance between the two sources of X-ray radiation which is useful in certain modes of X-ray application. The possibility of variations in the time sequence of the images and their duration does not suffer by the use of two X-ray tubes.

The revolving anode X-ray tube may be connected without; any difliculty with the customary transformers (Fig. 3). The corresponding poles of the cathodes are connected in parallel to the high tension winding M of the filament transformer l3 and the revolving anode 6 is connected with the high tension winding 15 of the high tension transformer I 6.

I claim:

1. In a Rontgen or X-ray tube having two cathodes and a revolvable anode coacting with the cathodes and reflecting the rays in the desired direction; a disc rotatably disposed in the inner space of the tube. in a plane perpendicular to the path of the reflected rays, the disc having one aperture coacting with the reflected rays, the speed of the disc being synchronized with the speed of the anode and determining the intervals of the pulses of the rays issuing from the anode.

2. A Rontgen or X-ray tube comprising a transparent bulb, the bulb having a neck at one end and an enlarged portion at the opposite end, a cathode disposed through opposite sides of the enlarged portion of the bulb, the inner ends of the cathodes being spaced apart in diametrically opposed relationship in a plane substantially perpendicular to the center line of the bulb, an anode disposed in the bulb intermediate the spaced inner ends of the cathodes, the anode reflecting the rays in the desired direction, a, shaft for the anode rotatably disposed in the bulb along the center line thereof, the shaft extending from the neck through the anode and protruding therefrom on the side of the enlarged portion of the bulb, means for keying the anode to the shaft, a motor disposed in the neck of the bulb and in operable engagement with the shaft, a disc keyed to the protruding end of the shaft, the disc having at least one aperture in the path of the refiected rays and coacting therewith, and alternating current means for electrically energizing the anode and cathodes to the emission point of the anode.

3. A Rontgen or X-ray tube according to claim 2 in which the aperture in the disc is synchronized with the number of cycles per second of the alternating current and the speed of the motor per second to permit the passage of a ray at intervals greater than one-fiftieth of one second.

4. A Rontgen or Xeray tube according to claim 2 in which the. aperture in the disc is synchronized with the number of cycles per second of the alternating current and the speed of the motor per second to permit the passage of a ray at time intervals of substantially one twenty-fifth of one second.

HANS KEHRLI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,643,453 Holst Sept. 27, 1927 2,009,498 Kerr J uly 30, 1935 2,327,586 Atlee Aug. 24, 1943 2,350,642 Schwarzer June 6, 1944 FOREIGN PATENTS Number Country Date 315,061 Germany Oct. 23, 1919 594,434 Germany Apr. 10, 1934

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