US3870915A

US3870915A - X-ray tube

Info

Publication number: US3870915A
Application number: US444255A
Authority: US
Inventors: Eckart Kussel; Heinz-Gunther Haubold; Peter Wombacher
Original assignee: Kernforschungsanlage Juelich GmbH
Current assignee: Forschungszentrum Juelich GmbH
Priority date: 1973-02-21
Filing date: 1974-02-20
Publication date: 1975-03-11
Anticipated expiration: 1992-03-11
Also published as: DE2308508A1; GB1445791A; DE2308508B2; FR2218649B1; FR2218649A1; JPS5041487A

Abstract

An x-ray tube, in which a rotation-symmetric anode passed through by a cooling fluid and located in a first high vacuum chamber connectable to a vacuum pump is detachably connected to a rotatable hollow shaft having associated therewith cooling fluid supplying and discharging conduit means respectively and extending through the wall of and into the first high vacuum chamber while a second high vacuum chamber containing blocking fluid, e.g. oil, for purposes of sealing the area where the rotatable shaft penetrates the wall of and enters the first high vacuum chamber is provided between an outer chamber and a prevacuum chamber. More specifically, between the prevacuum chamber and the first high vacuum chamber there is provided the second high vacuum chamber which is separated from the prevacuum chamber by first sealing means and from the first high vacuum chamber by at least a wall surface portion of the rotatable anode and by the second sealing means having a wall close and parallel to the rotatable anode. The second high vacuum chamber extends over the first sealing means while that wall of the second high vacuum chamber means which is located opposite the first sealing means simultaneously forms a wall of a cooling passage passed through by a cooling fluid.

Description

[ Mar. 11, 1975 [57] ABSTRACT An x-ray tube, in which a rotation-symmetric anode passed through by a cooling fluid and located in a first high vacuum chamber connectable to a vacuum pump is detachably connected to a rotatable hollow shaft having associated therewith cooling fluid supplying and discharging conduit means respectively and extending through the wall of and into the first high vacuum chamber while a second high vacuum chamber containing blocking fluid, e.g. oil, for purposes of sealing the area where the rotatable shaft penetrates the wall of and enters the first high vacuum chamber is provided between an outer chamber and a prevacuum chamber. More specifically, between the prevacuum chamber and the first high vacuum chamber there is provided the second high vacuum chamber which is separated from the prevacuum chamber by first sealing means and from the first high vacuum chamber by at least a wall surface portion of the rotatable anode and by the second sealing means having a wall close and parallel to the rotatable anode. The second high vacuum chamber extends over the first sealing means while that wall of the second high vacuum chamber means which is located opposite the first sealing means simultaneously forms a wall of a cooling passage passed through by a cooling fluid.

4 Claims, 1 Drawing Figure 313/32, 313/60 HOlj 35/10 Field of 313/32, 60.

United States Patent Kussel et al.

[ X-RAY TUBE [75] Inventors: Eckart Kussel, Duren; Heinz-Gunther Haubold; Peter Wombacher, both of Julich, all of Germany [73] Assignee: Kernforschungsanlage Julich, Gesellschaft mit beschrankter Haftung, Julich, Germany [22] Filed: Feb. 20, 1974 [21] Appl. No.: 444,255

[30] Foreign Application Priority Data Feb. 21 1973 [51] Int.

[56] References Cited UNITED STATES PATENTS 2,488 20O 11/1949 Juhlin ct al.

Primary Examiner.lohn Kominski Assistant ExaminerDarwin R. Hostetter Attorney, Agent, or Firm-Walter Becker (co/my l/a/ 1 X-RAY TUBE The present invention relates to an x-ray tube, in which a rotation symmetric anode is detachably connected to a hollow shaft, said anode being passed through by a cooling substance and being arranged in a highly evacuated chamber which through a connection is connected to a vacuum pump. The hollow shaft extends through the housing of the vacuum tube and serves simultaneously as inlet means and return means for the cooling substance. The hollow shaft is rotatably journaled in two bearings, one of which is located in a pre-vacuum chamber. For purposes of sealing the penetraton of the housing by the hollow shaft, in other words, between the outer chamber and the pre-vacuum chamber there is provided a chamber which contains a blocking liquid such as oil, or the like.

X-ray tubes are known in which for purposes of reducing the heat development, the anode is designed as a driven rotatably journaled body of rotation so that continuously other areas of the anode are exposed to the impacting electron beam. With a heretofore known x-ray tube with rotatable anode, one of the two bearings for the shaft on which the anode is arranged is pro vided within the highly evacuated tube chamber. This has the drawback that in view of the heating up of the lubricant employed for said one bearing, oil vapors develop. In order to prevent the thus effected reduction in the vacuum, it has been suggested with this type of x-ray tube to provide oil separators which are sealed relative to the highly evacuated chamber of the x-ray tube by gap seals. However, also such an arrangement could not bring about a sufficient improvement. In an endeavor to overcome the above mentioned drawbacks, it has been suggested with another electron tube having a rotatable anode to provide a special prevacuum chamber in which is arranged one of the two bearings of the shaft for the rotatable anode. Also, with this heretofore known x-ray tube no assurance could be realized that in view of the oil vapors escaping from the pre-vacuum chamber of the pre-pump .'connected thereto and in view of the oil vapors generated by the lubrication of the bearings, oil vapors would not pass into the highly evacuated tube chamber.

It is, therefore, an object of the present invention to provide an xray tube with a high output, in which it will be assured that no oil vapors can enter the highly evacuated tube chamber.

This object and other objects and advantages of the invention will appear more clearly from the following specification, in connection with the accompanying drawing, illustrating. a longitudinal section through an x-ray tube according to the invention while the protective mantle against radiation is removed.

The object underlying the present invention has been solved in conformity with the present invention by providing a chamber which is located between the prevacuum chamber and the highly evacuated chamber and which is separated from the pre-vacuum chamber by an oil seal, or the like, and from the highly evacuated chamber by a gap seal that is formed by the lateral surface or a portion of the lateral surface of the rotatable anode and a wall arranged at a slight distance parallel to the rotatable anode while extending over said oil seal, said chamber having a wall located opposite said oil seal and simultaneously forming a wall of a cooling passage passed through by a cooling substance.

In this way, oil vapors which might have entered into the highly evacuated chamber following the prevacuum chamber will surely be deposited on the cooled wall which is-located opposite the driving area or will be withdrawn in view of the connection of the highly evacuated chamber with the high vacuum pump for the high vacuum of the tube. A particularly advantageous embodiment of the x-ray tube according to the present invention consists in that on the outer surface of the rotatableanode there is provided an annular strip, or the like, which extends into the highly evacuated chamber and which extends over the seal separating the highly evacuated chamber from the pre-vacuum chamber. The said annular strip is equipped with a sharp-edged collar which points in the direction toward the cool surface of the highly evacuated chamber. This design serves to assure the oil separation also if a greater oil escape from the seal should occur.

In order to assure that for the generation of the high vacuum in the highly evacuated chamber of the x-ray tube and in the highly evacuated chamber only one high vacuum pump has to be employed, while on the other hand, it will be assured that also all vapors withdrawn from the highly evacuated chamber will not be able to enter the high vacuum chamber of the x-ray tube, it is expedient that the conduit leading from the highly evacuated chamber to the high vacuum pump leads into the pipe section which is provided on the x-ray tube and communicates with the high vacuum pump, a guiding plate being provided in the said pipe section which extends over the lead-in of the conduit. In this way, a completely oil-free vacuum will be safely .generated within the region of the electron beam.

7 It is furthermore advantageous that for forming a cooling water feed-in and cooling water return in the hollow shaft, there is provided a knock-out spindle known per se, which is journaled in a pivot bearing arranged in the rotatable anode.

Experience has shown that with an x-ray tube which has the features of the present invention and which was operated at a rotational speed of the rotatable anode of a maximum of 3,000 revolutions per minute while the diameter of the rotatable anode amounted to 25 centimeters, 21 complete oil-free tube vacuum of 10 Torr could be realized. Without output the measured tube vacuum amounted to 10 Torr.

Referring now to the drawing in detail, the electron beam emitted by the cathode 2 through a passage provided in the housing 1 impacts in a focal spot upon the mantle surface 3 of a rotation symmetric anode 7 which is journaled at one end on a hollow shaft 6 journaled in the bearings 4 and 5. For purposes of lubricating the bearing S, expediently, splash lubrication is provided.

The rotatable anode 7 is journaled in such a way that it extends into a highly evacuated chamber 9 which, through a connection 8, communicates with a high vacuum pump VP. Of the two bearings of the hollow shaft 6, the bearing 4 which is expediently designed as a fixed bearing is arranged outside the housing 1. The bearing 5 which is designed as an antifriction bearing is mounted in a pre-vacuum chamber 11 which communicates through a conduit with a vacuum pump, not illustrated in the drawing. The pre-vacuum chamber 11 follows achamber 13 which communicates with a container or tank 12 containing an oil or another blocking liquid. The chamber 13 is sealed by oil seals l4, l5 relative to the chamber located outside of the space surrounded by the housing 1 and also relative to the prevacuum chamber 11. Instead thereof, it is, of course, also possible to provide other suitable seals. As will be evident from the drawing, the pre-vacuum chamber 11 is followed by a highly evacuated chamber 16. Both chambers are separated from each other by an oil seal 17. The high vacuum chamber 16 communicates with a pipe line 18 through a nonillustrated high vacuum pump, said pipe line 18 leading into the connection 8. In order to prevent oil vapors passing from the pipe line l8 into the connection 8 from entering the highly evacuate'd chamber 9 of the x-ray tube, a guiding plate 19 is provided within the connection 8 and extends over the inlet of the pipe line 18. That wall of the highly evacuated chamber 16 which is located opposite the oil seal 17 simultaneously forms a wall of a cooling passage 20 which is passed through by a cooling liquid. The highly evacuated chamber 16 is separated from the highly evacuated chamber 9 of the x-ray tube by a gap seal 21 which is known per se, and composed of the lateral surface of the anode 7 and a side wall of the cooling passage 20. Oil vapors which form within the high vacuum chamber 16 are safely deposited on the common wall of the cooling passage 20 and the high vacuum chamber 16. In order to assure this even under extreme conditions, that lateral surface of the anode 7 which faces toward the highly evacuated chamber is provided with an annular strip 22 with a sharp-edged collar 23 pointing in the direction of the cooled wall of the high vacuum chamber 11. The strip 22 is so arranged that it extends over the area to be sealed by the oil seals 17 The hollow shaft is driven by the drive 24. In the hollow shaft 6 there is provided a knock-out spindle 25 which is so arranged that together with the hollow shaft 6 it forms the cool water supply 26 and the cool water return 27 for cooling the rotatable anode 27. In order to assure that the knock-out spindle will during the rotary movement of the hollow shaft 6 retain its position without changes, a pivot bearing 28 is arranged on the anode for journaling the knock-out spindle.

It is, of course, to be understood that the present invention is, by no means, limited to the specific showing in the drawing, but also comprises any modifications within the scope of the appended claims.

What we claim is:

1. An x-ray tube which includes: housing means defining first high vacuum chamber means and having a connecting section connectable to a vacuum pump, hollow shaft means extending through said housing means and into said first high vacuum chamber means, means drivingly connected to said shaft means for rotating the same, bearing means rotatably supporting said shaft means, a rotation symmetric anode located in said first high vacuum chamber means and detachably connected to said hollow shaft means for rotation therewith, said hollow shaft means having associated therewith conduit means leading to and from said anode and being connectable to a supply of cooling fluid and a discharge for respectively conveying cooling fluid to and from said anode, said bearing means including a first bearing and a second bearing closer to said anode than said first bearing, a prevacuum chamber surrounding a portion of said hollow shaft means and having said second bearing at least partially arranged therein, second high vacuum chamber means arranged between said prevacuum chamber and said first high vacuum chamber means, first sealing means, and second sealing means, said second high vacuum chamber means being separated from said prevacuum chamber by said first sealing means and being separated from said first high vacuum chamber means by at least a portion of the surface of said rotatable anode and by a wall of said second sealing means which wall is close to and substantially parallel to said anode surface, said second high vacuum chamber means extending partly over said first sealing means, and that wall of said second high vacuum chamber means which is located opposite said first sealing means simultaneously forming a wall of a cooling passage adapted to be connected to a supply of cooling fluid to be passed therethrough.

2. An x-ray tube according to claim 1, which includes annular strip means arranged on that side surface of said rotatable anode which faces toward said second high vacuum chamber means, said strip means extending into said second high vacuum chamber means and extending over said second sealing means which separates said second high vacuum chamber means from said prevacuum chamber, said strip means being provided with a sharp-edged collar pointing toward the cooled surface of said second high vacuum chamber means.

3. An x-ray tube according to claim 1, which includes a conduit leading from said second high vacuum chamber means to said connecting section, and guiding plate means extending over that area of said connecting section where said conduit leads into said connecting section.

4. An x-ray tube according to claim 1, which includes a knock-out spindle arranged in said hollow shaft means and forming therewith said conduit means leading to and from said anode for respectively conveying cooling fluid to and from said anode, and pivot bearing means arranged in said rotatable anode and supporting said knock-out spindle.