FR2480033A1 - ANODE DISC FOR AN ROTATING ANODE X-RAY TUBE AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

THE X-RAY TUBES Hitherto KNOWN IN WHICH A GRAPHITE BODY IS BRAZED TO A HEAVY METAL BODY HAD THE DISADVANTAGE THAT THE GRAPHITE BODY WAS DESTROYED BY THE THERMAL AND MECHANICAL STRESSES APPEARING IN OPERATION. FOLLOWING THE INVENTION, THE HEAVY METAL BODY 13 IS PROVIDED WITH A CIRCULAR FLANGE 22 SURROUNDING THE GRAPHITE BODY 10, A SOLDER LAYER BEING PRESENT BETWEEN THE INTERNAL FACE OF THE FLANGE AND THE OUTER FACE OF THE GRAPHITE BODY. IT TURNED OUT THAT THE GRAPHITE BODY IS THUS BETTER PROTECTED FROM DESTRUCTION. MOREOVER, THE BRAZING PROCESS IS SIMPLIFIED BY THE FACT THAT WHEN IT IS EXECUTED, THE HEAVY METAL BODY IS BELOW AND THE GRAPHITE BODY ABOVE. APPLICATION TO ROTATING ANODE X-RAY TUBES.

Description

"Anode disk for a rotating anode X-ray tube and method for

to make it

  The present invention relates to a disc of

  for a rotating anode X-ray tube which comprises

  in the assembled state of the X-ray tube, a metal body

  a rotationally symmetrical heavy weight connected to a drive shaft.

  and an annular graphite body which is connected to the heavy metal body via a layer

solder.

  Such anode disk is described in the application

  German Patent Publication No. 20 61 007.

  The graphite body then serves to increase the capacity

  of the anode disk and to increase the power emitted

  thermal sif. Since the drive shaft

  is also connected to the heavy metal body, the body in

  phite does not perform any support function. However,

  In practice, it should be noted that during the

  X-ray tube provided with such an anode disc.

  of fragments of the graphite body are sheared off the thus formed anode disk which becomes

therefore unusable.

  The present invention aims to achieve

  an anode disk of the type mentioned above in a manner

  to reduce the risk of the graphite body being completely or partially detached from the metal body

  heavy under the effect of thermal stresses.

  For this purpose, according to the invention, the heavy metal body has an annular flange turned towards the graphite body whose inner diameter is greater

  the outer diameter of the graphite body, this rectangular flange

  nular surrounding the outer edge of the graphite edge, and the solder layer is also present between

  the annular flange and the outer edge of the body in graph-

you. "

  Research has shown that such a disc of

  is better able to withstand the thermal stresses

  than the known anode disc of the type mentioned above. This can be explained as follows. In the known anode disk, the surfaces of the heavy metal body and the graphite body joined by brazing or thermal shrinkage are planar. During the junction, the two bodies have about the same temperature. After joining, the two bodies cool down, so

  the heavy metal body (in any case when

  a molybdenum base body with a tungsten layer), because of its higher coefficient of thermal expansion, contracts more strongly than

  graphite body. In the layers of the two neighboring bodies

  junction layers are therefore created which may result in the graphite body being

  or fragments of this body are detached by shearing.

  In the embodiment according to the invention

  of the anode disk, after joining, as the

  coldness progresses, compression stress

  increasing is exerted by the annular flange, by the in-

  of the connecting layer, on the outer edge of the

  graphite body. A graphite body can

  to withstand compressive stresses to a considerable extent, without breaking, but the same is not true for tensile stresses. These compressive stresses, which diminish during the operation of the tube irayons X by heating of the anode disk,

  prevent shearing of the anode disk.

  The heavy metal body to which, according to the

  vention, is attached the drive shaft, receives in function

  the forces transmitted by the drive shaft

  so that the graphite body is not stressed.

mechanically by them.

  The height of the rim of the heavy metal body need not be equal to the thickness of the graphite body. Since the shear stresses during cooling appear before

  everything in the area of the graphite body next to the

  braze, it is sufficient that only this area be

  the rim, the height of which must therefore not be

  only at a fraction of the thickness of the graphite body.

  The inner diameter of the annular flange may be approximately equal to or greater than a few tenths of a millimeter in the outside diameter of the outer edge of the annular flange.

  graphite body that surrounds it. The constraints of com-

  mechanical pressure is then transmitted to the body in

  phite via the junction layer.

  It is also not necessary that the wall

  the annular flange is parallel to the rotational axis

  anode disc. It may be appropriate for the inner edge to form an angle of 300 with the axis, because

  that the notch constraints are then lower.

  A particular advantage of the anode disc conforms

  The invention lies in the fact that the brazing operation can be performed in a particularly simple manner. In the case of the brazing process known hitherto (see, for example, German Patent Application Publication No. 20 61 007), the heavy metal body

  is above the body in grap-hte at the time of o-

  peration. If the solder layer becomes too hot

  of, the solder gushes in some places from the slot present between the two bodies and locally wets not only the graphite body, but, because of the molecular forces, also the upper face of the body in

  heavy metal. These solder remnants not only

  the melting temperature in the path zone of the furnace, but also reduce the yield of X-rays

  because of the generally relatively low order

the brazing material.

  According to another particularity of the invention, in order to carry out the brazing operation of an anode disc, the graphite body is placed on the heavy metal body

  by inserting a solder disk between them and we proceed

  from then to soldering. During brazing, the body in

  phite is thus above the heavy metal disc.

  The annular flange of the heavy metal disc which, at the time of brazing, is underneath, prevents

  any casting of the solder. Under the influence of

  the solder rises simply in the gap formed between the inner face of the annular flange and the edge

  outside and fills this gap.

  This advantage, however, is obtained only if the solder can not flow in another way, for example by the center of the heavy metal disc. According to another feature of this method of manufacturing a

  anode disc according to the invention, provision is made for

  use as a heavy metal body a bowl-shaped body without a central bore and braze it to the body

  graphite, then, after the soldering operation,

  a central bore in the heavy metal body and, where appropriate, in the graphite body. Since the heavy metal body thus forms a bowl during brazing, the solder layer can not flow out. Only then is the heavy metal body provided with the central bore needed to receive the drive shaft. The graphite body can be

  provided in advance with a bore in which the shaft of

  Trace is engaged when mounting the rotating anode X-ray casing. This bore can, however, also be formed at the same time as the bore of the heavy metal body. According to another particularity of the invention,

  it is expected that the heavy metal body will have a

  central ridge that extends into the graphite body

  nular and whose outer diameter is only slightly

  less than the inside diameter of the annular graphite body. The central trunnion provided in the heavy metal body, on the one hand, and the outer rim, on the other

  on the other hand, form an annular cup which also prevents

  the flow of the solder layer outside.

  The trunnion serves at the same time to center the body in gra-

phite. M0033

  The invention will be described hereinafter in greater detail.

  tail with reference to the accompanying drawings, in which: - Figure 1 illustrates a rotating anode X-ray tube, and

  FIGS. 2, 3 and 4 are views in section

  cross-section of various forms of

  anode according to the invention.

  In Figure 1, 1 designates the glass bulb

  of a rotating-anode X-ray tube

  1 end, a cathode assembly 3 and at its other end, anode assembly 4. The cathode assembly comprises a shielding element 5 to which is fixed the cathode head 6 in which is or are arranged the

  heating filaments, not shown in detail. The tendencies

  are provided by conductors 15, 16 and 17 which have the high voltage potential of the

cathode side.

  The anode assembly 7 comprises a rotor on the arm

  8 of which is attached an anode disc 9.

  The anode disk 9 comprises a heavy metal body 13 which is connected to the drive shaft 8. For this purpose,

  the upper end of the drive shaft is file-

  and receives the nut 11 which, when tightened,

  the heavy metal body 13 against the lower abutment 12 attached to the drive shaft. The anode disk, which is shown in section, further comprises a graphite body 10 which is brazed to the lower face of the body. heavy metal 13. The graphite body 10 is not in direct contact with the drive shaft 8 or with the stop 12. The high voltage on the anode side is provided by

  via the connecting pipe 18.

  Figure 2 illustrates one embodiment of

  - Viable to the anode disc, but not shown to scale. The heavy metal body 13 is made of a body

  molybdenum base which is provided with a layer of tungsten

  or at least one of the tungsten alloy in the zone of the path of the hearth 19. It may, for example, have a

  outer diameter of 120 mm and a thickness of 9 mm.

  The heavy metal body has on its underside a flat surface perpendicular to the axis of rotation or

  symmetry which is limited externally by an

  nular 22 and internally by a trunnion 23 of the heavy metal body 13. If we turn the heavy metal body of 1800 around a horizontal axis, we thus obtain on the upper side then an annular bowl whose bottom is formed by the surface 20 and whose side walls

  formed on the outside by the rim 22 and in the

by the trunnion 23.

  The outer edge has already been effective in the context of the invention for a height of only 1.5 mm. The annular rebor.d can however also be higher than 1.5 mm. The central trunnion 23, which is centered with respect to the axis of rotation 21 and in which

  a bore 24 is provided to receive the drive shaft.

  8 (Figure 1), must have the same height as the

annular flange 22.

  A rotationally symmetrical graphite body 10 is connected, via a solder layer 26, by its planar end face 25 to the surface 20 of the heavy metal body and by its parallel inner and outer peripheral faces. to the axis of rotation 21, respectively

  to the trunnion 23 and the annular flange 22. The body in.

  graphite can then be made of a graphite with very fine grain developed by compression and annealing, for example the quality 5890 of the firm Deutsche Carbone AG, which

  has a specific gravity of 1.85 g / cm 2, a resistance

  this at flexural fracture of 65 N / mm 2 and a coefficient of thermal expansion (at 1000C) of 4.2 x 10 6 / K. The outer diameter of the graphite body 10 is smaller than the inside diameter of the annular flange 22, for example 1.2 mm, so that between the annular flange 22 and the graphite body 10, there remains a solder layer of 0, 6 mm thick. The inside diameter of the graphite body 10 is greater than the outside diameter of the journal 23, but to a small extent, for example at most 0.2 mm, so that, in the state not yet brazed, the graphite body rests on the trunnion 23

  with a weak lateral play and is centered by this trunnion.

  To join the heavy metal body to the graphite body 10, the body is first positioned

  heavy metal downwards (relative to the position

  is shown in Figure 2, and is returned from 180

  around a horizontal axis), so that the annular bowl

  which is formed by the surface 20 and the annular flange 22 as well as by the trunnion 23, is on

  its upper face. In this annular bowl,

  a zirconium solder disc with a thickness of

  0.3 mm, whose inside diameter is greater than the diameter

  the inner body of graphite and whose outer diameter is smaller than the outer diameter of the graphite body, for example each 4 mm. We place

  the graphite body 10 on this solder disk. We heat

  then this assembly in a vacuum chamber, for example

  by high frequency heating. A eutectic melt is formed at a temperature of about 1.5000C as described in the published German patent application,

  second publication No. 21 15 896, and this

  the junction of the heavy metal body with the graphite body. When heating at high frequency (at 550 kHz), the solder rises first in the seal formed between the outer periphery of the graphite body 10 and the

  ring flange 22, because the outer zone, especially

  Particularly in the case of high-frequency heating, the annular flange is more heated than the zones farther inwards. After a certain time, however, the solder also rises in the joint formed between the trunnion 23 and the body. graphite 10, after which the supply of energy is interrupted and the molten solder solidifies so that its surface in the joint between the graphite body 10 and the annular flange 22

forms a meniscus 27.

  During this brazing operation, the solder can hardly flow outside, so that the disadvantages and the introduction of impurities in

  the heavy metal body related to this flow are wide-

  deleted. If the heating here is interrupted a bit too late, this is not as troublesome as in

  known soldering processes; however; a contribution of

  too prolonged energy can affect the sustainability of the

  junction because carbides can then be formed.

  The anode disk shown in FIG. 3, corresponding parts of which are designated by the

  the same reference figures as in Figure 2,

  of the anode disk shown in FIG.

  the fact that the heavy metal body, the upper surface of which

  re is bent in a known manner (angle of inclination with respect to the horizontal from 5 to about 200), has everywhere, except in the region of the annular rim 22 and the trunnion

  23, a uniform thickness, so that the-side 20 'turn-

  born towards the graphite 10 body is no longer flat like this

  it of the anode disc shown in Figure 2, but is also bent or inclined outwards. The surface

  delimiting the graphite body 10 shown in FIG.

  above on the drawing must then be shaped correspondingly. The journal 23 must in this case be higher than the annular flange, but its end face is then also, with the lower end face

  of the annular rim 22, in a plane approximately

  The brazing is carried out in the same manner as that described with reference to FIG.

figure 2.

  Figure 4 illustrates an anode disk in

  an intermediate stage of its manufacturing process.

  The heavy metal body then has a continuous flat bottom face 20 ", bounded by the annular edge 22,

  and has neither bore nor journal at its center.

  In the annular bowl formed by the annular rim 22 and the surface 20 ", which, during the brazing operation, is open upwards, a solder disk is placed,

  preferably zirconium, as well as the graphite body

  the cylindrical 10 which can, if necessary, be provided with a central bore. After brazing, a bore 24 ', indicated by broken lines, is formed in the

  heavy metal body 13 and serves to couple the disk of

  node to the drive shaft. When the body in

  phite 10 does not already include such a central bore, this

  bore also crosses it. In case the bore bores

  pouring the graphite body 10 does not have a larger diameter

  In the assembled state of the tube also the graphite body 10 passes through the heavy metal body 13, but the latter is then only subjected to compression forces which 'he

can support without more.

Claims (5)

  1. Anode disk for an X-ray tube to   rotating anode which includes, in the assembled state of the tu-   X-ray bee, a heavy metal body with rotational symmetry   (13) connected to a drive shaft (8) and a graphite body (10) which is connected to the heavy metal body, characterized in that the heavy metal body has   an annular flange (22) facing the graphite body   te (10) whose outer diameter is greater than the diameter   external meter of the graphite body (10), this   nular (22) surrounding the outer edge of the body in   phite. Anode disk according to Claim 1, characterized in that the heavy metal body (13) and the graphite body (10) are connected to one another by means of   a solder layer (26) which also extends between the   edge (22) and the outer edge of the body in phite (10).   3. Anode disk according to claim   1, characterized in that the heavy metal body (13)   a central trunnion (23) extending in the annular graphite body (10) and having an outside diameter only slightly smaller than the inside diameter of the annular graphite body.   Anode disc according to Claim 1 or 2, characterized in that the heavy metal body (13) contains molybdenum which is provided on its side opposite the joining layer (26) with a layer of tungsten or a tungsten alloy.   5. Anode disk according to claim   2, characterized in that the solder layer is substantially made of zirconium.