US3763387A

US3763387A - X-ray tube with rotary anode

Info

Publication number: US3763387A
Application number: US00096527A
Authority: US
Inventors: K Silbermann
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1970-02-28
Filing date: 1970-12-09
Publication date: 1973-10-02
Anticipated expiration: 1990-10-02
Also published as: DE2009538C3; DE2009538B2; SE358992B; GB1294625A; DE2009538A1; FR2078933A5

Abstract

An X-ray tube with a rotary anode the path of the focal spot of which is subdivided by separating adjoining surfaces. The invention is particularly characterized in that the separating adjoining surfaces extend not only through the path of the focal spot but also through the anode body.

Description

Silbermann Oct. 2, 1973 1 X-RAY TUBE WITH ROTARY ANODE [75] Inventor: Karl Silbermann, Erlangen,

Germany [73] Assignee: Siemens Aktiengesellschaft,

Erlangen, Germany [22] Filed: Dec. 9, 1970 [21] Appl. No.: 96,527

[30] Foreign Application Priority Data Feb. 28, 1970 Germany P 26 09 538.9

1521 vs. c1. 313/60, 313/330 3,229,089 1/1966 Sasao 313/60 X Primary ExaminerR0y Lake Assistant ExaminerLawrence J. Dahl Attorney-Richards & Geier [57] ABSTRACT An X-ray tube with a rotary anode the path of the focal spot of which is subdivided by separating adjoining sur- 5H on 35/04 faces. The invention is particularly characterized in [58] Field of Search 313/60, 330, 58 that the Separating adjoining surfaces extend n I through the path of the focal spot but also through the [56] References Cited anode body- UNITED STATES PATENTS 2,482,053 9/1949 Zunick 313/58 X 5 Claims, 2 Drawing Figures f l' 1 1 5 16 8 I 1 1; 14 a 1 13 1 L 11 1O 9 l X-RAY TUBE WIT-H ROTARY ANODE DESCRIPTION OF THE INVENTION This invention relates to an X-ray tube with a rotary anode the path of the focal spot of which is subdivided by separating joints. The entire anode consists of a material which does not melt easily and has the shape of a plate, a pot, a ring or the like, from which heat created during the production of rays is radiated.

ln X-ray tubes with rotary anodes the anode is heated by electrons which are braked in the path .of the focal spot. This results in mechanical tensions between the colder parts of the anode and the focal spot path which can cause tears. Due to the action of the centrifugal force this can cause the breaking up of .the anode and thus the destruction of the X-ray tube. Tensions are caused by the fact that in most cases the loading takes place so quickly that the speed of passage of heat to the other parts of the anode does not always suffice to maintain the tensions below dangerous stresses. The danger of tearing is particularly great in anodes made of tungsten and molybdenum since in these substances zones which are colder than 200C have a substantially greater brittleness than those which are warmer. Consequently, at the present time, when using the generally available plates the load must be so adjusted that the heating extends over a time period sufficient for the outflow of heat, thereby avoiding dangerous tensions. However, the resulting extension of the time of illumination is undesirable since it makes impossible instantaneous photographing. For the usual diameter of l.cm. the required time period is about -40 see.

In known X-ray tubes with rotary anodes, wherein the focal point path has separating joints, these joints are constituted by bordering parts of wound bands, or tubes placed one over the other, or pieces of wire inserted brushlike into the focal spot path. However, in those cases as well the actual anode consists of a plate extending from its center to the periphery. Thus even this known interruption of the focal spot path used to prevent granulations does not avoid the possibility of cracks resulting in the breaking of the anode plate.

It was hoped that a remedy would be found by the use of rotary anodes which are also known and wherein the focal spot path lies upon the outer surface of a ring. It was expected that the loading capacity would be in- I creased due to the short path of heat flow. On the other hand tensions produced relatively to the axis of rotation would be padded by spoke-like elastically form changing holders. However, a ring has only a small outer surface as compared to known anode plates and also has only small contacting surfaces with the holding means which extend to the axis. Thus it has also smaller heat conductivity and particularly smaller heat transmission than anodes having the usual plate shape, so that tensions occur in the ring shape as well.

An object of the present invention is to avoid these drawbacks of prior art constructions.

Other objects of the present invention will become apparent in the course of the following specification.

In the accomplishment of the objectives of the present invention it was found desirable to provide separating adjoining surfaces which in addition to the focal spot path also extend through the body of the anode. According to this construction the ring-shaped part of the anode which is heated during ray formation and expands to a considerable extent, is broken up into smaller parts which can be shifted relatively to each other. Then an expansion relatively to the remaining colder material cannot produce detrimental tensions any more. The best subdivision of plates having, for example, a diameter of mm. and a thickness of 4 to 6 mm., consisting of tungsten or some other substance which melts with diffuculty, is to be considered as consisting of three or four parts, since then there are only a few separating adjoining surfaces and nevertheless there are no great expansions and relative shiftings.

Parts which in the usual anode plates or anode rings have the shape of sectors and consist of difficultlymelting substances of high order, such as tungsten, molybdenum, alloys of tungsten and rhenium etc., can be held together by clamps, or a ring consisting of similar or the same material as the parts of the anode. Then during heating the clamping has properties similar to the subdivided anode and thus the holding together of the parts is assured. By way of example, the clamping ring can be inserted or soldered at the lower side of the anode in a ring-shaped groove extending concentrically to the central axle. Besides the above-mentioned metals a compound material consisting of layers can be also used for the anode. This material may consist of a difficultly melting carrier, for example, graphite, and a difficultly melting metal, such as tungsten and its alloys, which is sprayed or soldered etc. as a layer.

The side edges of the parts of the anode which engage each other in the separating adjoining surfaces are preferably cut relatively to each other, so that, for example, they overlap each other, so that no slits are formed which extend through the thickness of the anode plate and which would permit passage for the electrons of the cathode. It is of importance that the separating adjoining surfaces should extend at least partly in a direction different from that of the electrons coming from the cathode. The separating adjoining surfaces can also deviate from a straight line in the radial direction. They can have, for example, the shape of teeth, etc. Parts of anode, particularly at their lower sides, can be provided for additional stabilization with radially extending strengthening members, such as ribs, etc.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing by way of example only, a preferred embodiment of the inventive idea.

In the drawing:

FIG. 1 is a perspective view of an X-ray tube constructed in accordance with the principles of the present invention.

FIG. 2 is a perspective view of an anode plate on an enlarged scale, one of the sectors having been removed. I

FIG. 1 shows the glass bulb 1 of the X-ray tube 2. The glass bulb l is cylindrical and at its two ends are located opposite each other in a manner known per se the cathode combination 3 and the anode combination 4. The cathode combination 3 includes the holder 5 with the screen 6 in which is located the glow cathode. The glow cathode is covered and therefore not shown in the drawing. The anode combination 4'consists of a rotor 7 and an anode plate 8 having in the illustrated example a diameter of 100 mm. and a thickness of 6 mm. The anode plate 8 is composed of sectors, 9, l0, 1 l and 12. Focal spotpaths l3 and 14 are located upon the sectors in a manner known per se in connection with anode plates. The plate 8 is fixed upon an axle by a screw 16.

To produce the rays the necessary operational and heating voltages are supplied to the X-ray tube through the anode joint 17 as well as the conduits l8, l9 and 20. The sectors 9 to 12 of the anode plate 8 can shift relatively to each other due to the heating which is then produced and which causes their expansion relatively to each other, thereby avoiding tears. Step-

like overlaps

21 and 22 are located, as shown, at the edges of the plate 8; they prevent the electrons proceeding from the cathode from passing through the separating adjoining surfaces of the anode plate 8. The connection of the sectors 9 to 12 takes place from the bottom by means of a plate 24 consisting of the difficultly meltable metal molybdenum and mounted upon a flange 23 of the axle 15.

Furthermore, the sides surfaces of the

sectors

9 and 11 shown in FIG. 2 indicate that the focal spot paths l3 and 14 of the anode 8 are located upon a layer 25 of a rhenium-tungsten alloy which is l.5 mm. thick and which is carried by a plate 26 consisting of molybdenum. A firm connection takes place by an annular shoulder 27 located upon the edge of the plate 24 and engaging an annular groove 28 provided upon the under surfaces of the sectors 9 to 12. To provide this firm connection the sectors 9 to 12 are pressed by the screw 16 against the plate 24 which lies upon the flange 23 of the axle 15. Due to this arrangement the annular shoulder 27 firmly engages the groove 28 and together with the plate 24 constitutes a hook connecting the sectors 9 to 12 with the axle 15.

Ribs 29 are located upon the underside of sectors 9 to 12 at uniform distances from each other. At their outer edges the ribs are axially 5 mm. high and their height diminishes gradually to zero at the edge of the plate 24. Each of the sectors 9 to 12 has four ribs 29 which serve to strengthen the structure. The ribs have a base which is 2.5 mm. wide and they have a narrow end surface with rounded edges.

I claim:

1. An X-ray tube having a rotary anode and a focal spot path upon said anode having an outer surface consisting of the same material throughout the focal spot path, said anode and said focal spot path consisting of sectors separated by adjoining surfaces extending through the anode from the center of the anode to its outer edges.

2. An X-ray tube in accordance with claim 1, having a plate-like or ring-shaped anode plate, wherein said separating adjoining surfaces extend radially to divide the anode plate into a plurality of sectors, said sectors having an annular groove upon their bottom surface, and a ring engaging said groove for holding said sectors together.

3. An X-ray tube in accordance with claim 1, having a cathode and wherein said separating adjoining surfaces extend at least partly in a direction different from that of electrons emanating from the cathode.

4. An X-ray tube in accordance with claim 3, wherein said separating adjoining surfaces have step-like overlaps.

5. An X-ray tube in accordance with claim 2, wherein said sectors have strengthening members.

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