US3546511A - Cooling system for a rotating anode of an x-ray tube - Google Patents

Description

Dec. 8, 1970 YOSHIHIRO SHIMULA COOLING SYSTEM FOR A ROTATING ANODE OF AN X-RAY TUBE Filed July 31, 19s? nun? OOOO FIG. 3

FIG. 4

United States Patent 3,546,511 COOLING SYSTEM FOR A ROTATING ANODE OF AN X-RAY TUBE Yoshihiro Shirnula, Tokyo, Japan, assignor to Rigaku Denki Company Limited, Tokyo, Japan Filed July 31, 1967, Ser. No. 657,225 Int. Cl. F28d 11/02; H01j 1/44 US. Cl. 313-32 9 Claims ABSTRACT OF THE DISCLOSURE A cooling system in which a cylindrical hollow stationary member is positioned within a cylinder rotary anode, a conduit for a cooling fluid being connected to the stationary member to cause discharge of cooling fluid through openings in the periphery of the stationary member, in the form of jets, towards the inner peripheral surface of the anode, the periphery of the stationary member having successive inclined surfaces forming a serrated outer surface for the stationary member in which the apeXes thereof are in close proximity with the inner surface of the anode.

BRIEF SUMMARY OF THE INVENTION This invention relates to a cooling system of an X- ray tube of the type provided with a cylindrical rotary anode.

The peripheral surface of such a cylindrical rotary anode of an X-ray tube is heated by electronic impulses. In order to cool such a heated anode with water, it is known to place a cylindrical stationary partition within the cylindrical anode in spaced relation relative to the inner peripheral surface of the anode and to circulate water through the space defined by the outer peripheral surface of the partition and the inner peripheral surface of the cylindrical anode.

The anode rotates at a high speed of the order of several hundred revolutions per minute. Thus, the cooling water flowing in contact with the inner surfaces of the anode tends to be rotated with the rotation of the anode. The water also will be pressed against the inner surface of the anode by centrifugal force and consequently the tendency of the water to rotate with the anode will be increased due to the increased friction between the water and the anode surface.

In this manner, a layer of water will be formed which will adhere to the anode surface and rotate therewith. This layer of water will be substantially static instead of moving in the direction of water flow. In other words, the

portion of cooling water which is in contact with the inner surface of the anode does not flow, and only the remainder of the water which is not in contact with the anode surface flows and is circulated. In a conventional cooling system of this kind, it has been found that the static water layer interferes with the cooling of the anode.

It is an object of this invention to prevent water from adhering with the inner surface of the anode whereby to avoid the formation of a Water layer which rotates with the anode.

Another object of this invention is to provide an improved system for cooling a rotary anode which is capable of injecting cold water directly against the portion where the temperature rise is greatest in the rotary anode to accomplish effective and efiicient cooling.

A further object of this invention is to provide an improved system for cooling a rotary anode, in which a layer of cooling water on the inner surface of the anode is formed with portions having various thicknesses so as to utilize the cooling action due to evaporation effectively.

In accordance with the invention, the stationary parti- 3,546,51 l Patented Dec. 8, 1970 tion within the anode has a periphery formed by a succession of inclined surfaces which define a serrated surface, the apexes of which extend towards the surface of the anticathode into close proximity therewith, thereby serving to disturb the formation of a static water layer on the inner surface of the anode.

In further accordance with the: invention the partition is provided with a plurality of holes opening in the inclined surfaces for ejecting the water in the form of jet streams towards the inner surface of the anode.

BRIEF SUMMARY OF THE DRAWING FIG. 1 is a longitudinal sectional view of a portion of an X-ray tube with an embodiment of a cooling system therefor according to the invention;

FIG. 2 is a sectional view taken along line 11-11 of FIG. 1;

FIG. 3 is an enlarged sectional view of a portion of FIG. 2; and

FIG. 4 is a view of a development of a portion of the peripheral surface of a cooling water injecting partition.

DETAILED DESCRIPTION In the illustrated embodiment, a rotary cylindrical shaft 3 is supported by a pair of bearings 2, secured to a casing 1 and an air-tight relation is maintained between the bearings by means of a Wilson seal 4. Mounted on the shaft 3 within the casing is a hollow cylindrical rotary anode 5, while a pulley 6 is mounted on the shaft outside the casing. A hollow cylindrical stationary partition 7 is coaxially disposed within the anode and is connected to a water conduit 8 mounted in the shaft 3.

The cylindrical partition 7 is provided with a plurality of cooling water conduits 9 extending through the partition end walls for the flow of water as will be described more fully later. The outer peripheral surface of the partition is formed with successive inclined surfaces 10 to produce a serrated surface as seen in FIGS. 2 and 3. A plurality of cooling water injection holes 11 extend through the peripheral wall of the partition and open in surfaces 10.

The peripheral wall of the anode is relatively thin and the apexes of the oblique surfaces 10 lie closely adjacent the inner surface of the anode without interferring with the rotation of the anode. A short cylinder 12 formed coaxially with the water conduit 8 is fitted within the shaft portion of the pulley 6 with a Wilson seal 13 between the cylinder 12 and the pulley 6. A drain pipe 14 is connected to the end face of the cylinder 12 to complete a flow path for the cooling water from a supply line 15 to a drain line 16 through the partition 7 and within the anode as will be described more fully subsequently.

A cathode 17 is situated in the casing 1 in facing relation with the periphery of the anode 5. An X-ray outlet window 18 is provided in the side wall of casing 1 and the casing 1 is connected to an air pump (not shown) through a conduit to evacuate the casing.

The pulley 6 is connected to a prime mover such as an electric motor to cause the anode 5 to be rotated in the direction as shown by arrow (p) while cooling water is fed to the interior of the cylindrical partition 7 from the water supply line 15 through the water conduit 8 as shown by arrows (q). The cooling water passes in the form of jets from the interior of the partition through the injection holes 11 toward the inner surface of the anode 5 as indicated by arrows (r) and flows along the inner surface of the anode. A portion of the cooling water then flows directly into the hollow shaft 3 pass ing through the space between the anode and the left end face of the partition in FIG. 1 as shown by arrows (s), while the remainder of the cooling water passes in the space between the anode and the right end face of the partition in FIG. 1, as shown by arrows (t), and

flows into the shaft 3 through the cooling water conduits 9. The drain Water then passes through pipe 14 into the cylinder 12 and is finally discharged through the drain line 16 as indicated by arrow (u).

At the same time, the electrons projected from the cathode 17 to the peripheral surface of the anode 5, cause X-rays to be emitted from the anode surface which pass through the window 18.

As set forth above, in the improved cooling system of the present invention, cooling water received in the cylindrical partition 7 having a large capacity is injected through the small injection holes 11 directly against the inner surface of the anode which are the portions heated by the electron ray impulses. By the jet action, the water in the cylindrical partition is maintained at a desirably low temperature for cooling purposes. Moreover, since the cold water directly discharges against the inner surface of the anode and the water flows in axial direction along the anode surface at a high speed, effective cooling of the high temperature portions thereof is obtained. Furthermore, the serrated peripheral surface of thepartition defines a space between the apexes (x) of the teeth and the inner surface of the anode 5 which is relatively small so that as the anode 5 is rotated in the direction as shown by arrow (p), cooling water which adheres to the inner surface of the anode and which tends to rotate therewith is scraped by the apexes (x). Thus the cooling efliciency at the inner surface of the anode is further improved due to the continuous direct contact of the anode inner surface with the injected cold water passing through the holes 11. It should be noted that the distance (y) between the inner surface of the anode and each of the oblique surfaces of the serrated periphery of the cylindrical partition 7 varies depending upon the position of the oblique surface relative to the anode surface. In other words, since the amount of water contacting the various portions of the anode inner surface varies, the quantity of heat required to evaporate the water also varies depending upon the position. Thus, when the quantity of electron rays is, for example, large, a large amount of cooling water is readily evaporated in portions with greater distances (y) and the anode is effectively cooled by the heat-exchange effect in the evaporation. On the contrary, when the quantity of electron rays is small, the evaporation is effected in portions with small distances (y). Thus the evaporation heat is always absorbed from the anode independent of the quantity of electron rays so that it may be efliciently cooled.

What is claimed is:

1. Apparatus for cooling a hollow rotary member, said apparatus comprising a hollow stationary member mounted within the rotary member, the stationary and rotary members having annular peripheral surfaces encircling the axis of rotation of the rotary member and facing one another, means for circulating a cooling fluid radially between the peripheral facing surfaces of the stationary and rotary members, and means fixedly mounted on the peripheral surface of said stationary member facing the rotating member for disturbing the formation of a static layer of cooling fluid on the surface of the rotating member, the latter means including spaced projections fixed on the surface of the stationary member extending towards the surface of the rotary member into close proximity therewith, said means for circulating a cooling fluid comprising means for supplying cooling fluid to the stationary member, said stationary member having a plurality of holes facing the peripheral surface of the rotary member for the discharge of jets of fluid towards the rotary member, and means for recovering the fluid from the rotary member.

2. Apparatus as claimed in claim 1 wherein the peripheral surface of said stationary member has successive inclined surfaces with apexes which constitute said projections.

3. Apparatus as claimed in claim 2. wherein said holes extend through the stationary member and open at the inclined surfaces.

4. Apparatus as claimed in claim 3 wherein said holes extend perpendicular to the surface of the rotary member.

5. Apparatus as claimed in claim 4 wherein said rotary member is a cylindrical anode of an X-ray tube which is subjected to electron bombardment resulting in heating of the rotary member, said stationary member being cylindrical and coaxially disposed within the rotary member and having end walls defining radial spaces with the anode, said cooling fluid flowing from the space between the peripheral surfaces of the stationary member and the anode axially in opposite directions towards said radial spaces.

6. Apparatus as claimed in claim 5 wherein said means for circulating a cooling fluid includes a drain line, said stationary member being provided with openings establishing communication between said radial spaces to enable the fluid therein to combine and flow to the drain line.

7. Apparatus as claimed in claim 5 wherein said peripheral surface of the stationary member includes radial surfaces joining said inclined surfaces.

8. Apparatus as claimed in claim 5 wherein said holes extend in a plurality of circumferential rings arranged axially along the stationary member.

9. Apparatus as claimed in claim 8 wherein said holes are equally spaced circumferentially in the stationary member, and a plurality of holes open externally in each inclined surface.

References Cited UNITED STATES PATENTS 2,277,430 3/ 1942 Findlay 313-32 2,488,200 11/1949 Juhlin 313--60 2,617,057 11/1952 Reiniger 31332 2,715,194 8/1955 Combee 31332 FOREIGN PATENTS 1,086,815 8/1960 Germany 313-55 613,662 5/1935 Germany --91 JAMES W. LAWRENCE, Primary Examiner E. R. LA ROCHE, Assistant Examiner US. Cl. X.R.

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