FR3019372A1 - ANODE FOR X-RAY EMISSION AND METHOD OF MANUFACTURE - Google Patents

Abstract

Rotating anode for X-ray emission, comprising a disk having an axial receiving passage and opposite faces surrounding this passage, and provided, on an annular zone of its surface, with a coating (6) capable of producing radii X under the effect of an incident beam of electrons, further comprising an intermediate mounting insert (7), fixed on the disk (2) and comprising at least one central portion (10) inserted into said axial receiving passage (3) of the disk and having an axial mounting bore (12) and at least one annular portion (13) bearing on one of said opposite radial faces (15) of the disk and having a radial mounting face (7b).

Description

The present invention relates to the field of X-ray emitting devices, used in particular for producing images, and more particularly used in medical imaging scanners, and concerns more precisely the field of rotary anodes equipping such devices, which are provided with coatings capable of producing X-rays under the effect of incident beams of electrons directed towards and bombarding their coatings locally. Rotary anodes commonly used in X-ray emitting devices, generally referred to as X-ray tubes, comprise disks generally made of a refractory material, for example a molybdenum-based alloy or pure molybdenum, which are provided on one side before tracks formed by coatings which may be in different refractory metals capable of producing X-rays, generally tungsten or a tungsten-rhenium alloy, sintered and / or brazed. The rotary anodes are mounted on shaft end portions driven in rotation, which are generally made of a refractory material, for example an alloy based on molybdenum, in particular titanium-zirconium-molybdenum (TZM) or molybdenum pure, between shoulders of the shafts and nuts, being brazed on these shoulders through the interposition of a braze material such as palladium-cobalt or palladium-nickel. Such assemblies are in particular described in US Pat. No. 4,736,400. Because of their weight, the speeds of rotation of such anodes are capped, generally at about 10,000 revolutions per minute. The temperature at the point of impact of the electrons can reach 2000 ° C, the temperature of the anodes, in their mass, is high and settles generally around 1300 ° C.

To increase the power of the X-radiation emitted, it is proposed to further increase the rotational speed of the anodes. For this, the weight of the anodes must be reduced. For this purpose, it is already known to produce, partially or totally, anodes made of a carbon-based material, for example graphite, carbon fiber compounds or carbon-carbon composites, which also allows dissipation. improved heat. However, such anodes have mounting difficulties on the ends of the shafts to support them and drive them in rotation.

US Patent 4,481,655 and US Patent 4,276,493 disclose anodes formed by graphite disks mounted directly on shaft end portions engaged through their axial passages between annular shoulders of the shafts and nuts. No. 6,088,426 discloses an anode formed by a graphite disk coated with a layer of a metal carbide on its opposite radial faces and on the wall of its axial passage. This disc is mounted directly on an end portion of a shaft engaged through its axial passage, between an annular shoulder of this shaft and a nut, and interposing a solder material between respectively on the one hand the radial faces of the disc and on the other hand the shoulder of the shaft and the nut. WO 2011/001354 discloses an anode formed by a graphite disc having an axial passage hexagonal section. When mounting the disk on a drive shaft, there is interposed between them a socket provided on one side with a peripheral shoulder. This sleeve has a hexagonal peripheral section coupled to the hexagonal section of the axial passage of the disc and has a cylindrical axial passage through which a portion of the drive shaft. The peripheral shoulder abuts on a face of the disk surrounding its hexagonal axial passage, via an adjusting washer and a washer made of a solder material. A nut is mounted on the end of the shaft, via a safety washer.

In order to improve heat dissipation, a graphite body can be soldered to one side of a molybdenum alloy body. These anodes are therefore heavier than anodes entirely made of graphite or carbon-carbon composite.

In any case, adjusting and maintaining the rotating anode on the rotor axis of the X-ray tubes requires the anode to be connected to the rotating part (rotor) of the X-ray tube. often, the rotor is made of a molybdenum-based alloy, such as TZM (Titanium-Zirconium-Molybdenum). TZM is the most used material but other molybdenum alloys can be substituted for it. The axis can also be made of pure molybdenum (unalloyed). For light anodes, this requires the attachment of the graphite or composite part of the anode to the molybdenum alloy axis of the rotor. The object of the present invention is to improve the characteristics of rotary X-ray emission anodes, to improve their manufacturing processes and to improve their mounting on rotating shafts of X-ray tubes. A rotary anode is proposed. for X-ray emission, comprising a disk which has an axial receiving passage and opposite faces surrounding this passage and which is provided, on an annular zone of its surface, with a coating capable of producing X-rays under the effect of an incident beam of electrons. This anode further comprises an intermediate mounting insert, fixed on the disc and comprising at least one central portion inserted into said axial passage for receiving the disc and having an axial mounting bore and at least one annular portion bearing on one end. said opposite radial faces of the disc and having a radial mounting face. Said intermediate insert insert may comprise an insert element comprising said central portion and said annular portion. Said intermediate insert insert may comprise two insert elements, one of these two insert elements comprising said central portion and said annular portion and the other insert element comprising an annular portion bearing on the other of said radial faces of the disc. Said other insert element may comprise a central portion inserted in said axial disk receiving passage and having an axial mounting bore. Said intermediate mounting insert can be attached to the disk by soldering. Said intermediate mounting insert can be fixed to the disk by tie rods.

Said tie rods can extend in the axial passage of the disc. Said tie rods can cross the disc. The disc may be formed at least in part by a carbon-based material such as graphite or a carbon / carbon composite. Said intermediate mounting insert may be attached to the disk by a solder and may consist of an alloy predominantly molybdenum. Said intermediate mounting insert may be fixed by a solder of an alloy predominantly of palladium. There is also provided a method for manufacturing a rotary anode for X-ray emission, which comprises: producing a disk having an axial receiving passage and opposite faces surrounding this passage and provided, on an annular zone, with a coating capable of producing X-rays under the effect of an incident beam of electrons, mounting and fixing on the disk an intermediate mounting insert comprising at least one central portion inserted in said axial passage of the disk and having a axial mounting bore and at least one annular portion bearing on one of said opposite radial faces of the disk. The annular portion of the intermediate fitting insert can be attached to the disk by a brazing operation.

The method may comprise the realization, before mounting of the intermediate insert, of a cylindrical machining operation of the annular coating. The method may comprise the production, after assembly and fixing of the intermediate insert, of a machining operation of the axial bore concentrically mounting said coating and a machining operation of the face of said portion. annular radially to the axis of said coating. It is also proposed a machine which comprises a rotary shaft on which is mounted an anode as defined above. Rotating X-ray emission anodes according to the present invention will now be described by way of nonlimiting examples, illustrated in the drawings in which: FIG. 1 represents an axial section of a rotary anode; - Figure 2 shows an axial section of a mounting of the rotary anode of Figure 1 on a rotating shaft; - Figure 3 shows an axial section of another rotary anode; - Figure 4 shows an axial section of another rotary anode; - Figure 5 shows an axial section of another rotary anode; - Figure 6 shows an axial section of another rotary anode; - Figure 7 shows an axial section of a mounting of the rotary anode of Figure 6 on a rotating shaft; and - Figure 8 shows an axial section of another rotary anode. In Figure 1 is illustrated a rotary anode 1 for the emission of X-rays. This anode 1 comprises a substrate formed by a disk 2, for example graphite or carbon-carbon composite. The disk 2 could also comprise an annular portion of molybdenum-titanium-zirconium alloy (TZM) The disk 2 has an axial receiving passage 3 and has a front face or front 4 and a rear face 5, substantially radial. The disk 2 is provided, on a slightly frustoconical peripheral zone of its front face 4, with a target coating 6 which comprises at least one material capable of producing X-rays under the effect of an incident beam of electrons, by example of tungsten or an alloy comprising mainly tungsten, for example tungsten-rhenium.

The target coating 6 can be made at the same time as the disc 2 or can be attached to a disk previously manufactured for example by chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods, and can include one or more layers of materials.

The front face 4 and the rear face 5 of the disc 2 have, at the bottom of the recess, respectively opposite radial surfaces 4a and 5a surrounding the axial receiving passage 3. The disc 2 is equipped, so as to form a unit, an intermediate insert 7 which, according to an exemplary embodiment, comprises two insert elements 8 and 9. The insert element 8 comprises a central cylindrical part or sleeve 10 inserted, for example by a tight fit, in the axial receiving passage 3 of the disk 2 and a radial annular portion 11 in the form of a washer which bears above the radial surface 4a of the end face 4 of the disk 2. The central portion 10 of the insert element 8 has an axial mounting bore 12. Thus, the intermediate insert 7 has a front face 7a extending radially. The insert member 9 comprises a washer-shaped radial annular portion 13 which is in contact with the radial surface 5a of the rear face 5 of the disc 2 and whose inner annular portion is inserted into a peripheral fitting recess. 10a arranged in the rear end of the central portion 10 of the insert member 8. Thus, the intermediate insert 7 has a rear face 7b extending radially. The intermediate insert 7 may consist of an alloy mainly of molybdenum, in particular a titanium-zirconium-molybdenum alloy (TZM). The intermediate insert 7 is firmly fixed to the disk 2 by means of a solder 14 formed between the annular portion 11 of the insert element 8 and the front radial surface 4a of the disk 2 and on the other hand a solder 15 formed between the annular portion 13 of the insert member 9 and the rear radial surface 5a of the disc 2. The material for making the solders 14 and 15 may be palladium or a palladium-cobalt alloy or palladium-nickel, optionally associated with an underlayer of a carbide metal on the side of the disk 2 to increase the adhesion with the disk 2. The rotary anode 1 can be manufactured in the following manner. A disc 2 is produced with the annular coating 6. Optionally, a frustoconical machining operation of the coating 6 is carried out.

The insert elements 8 and 9 are manufactured. The insert elements 8 and 9 are mounted respectively on each of the front and rear faces 4 and 5 of the disc 2, by inserting the solder materials 14. and 15. The brazing operations 14 and 15 are carried out in an oven.

The disc 2 thus obtained is thus equipped with the intermediate insert 7. Next, an axial cylindrical machining operation is carried out on the axial mounting bore 12 of the intermediate insert 7 mounted concentrically to the axis of the annular coating. 6 and a radial surface machining operation is performed on the faces 7a and 7b of the intermediate insert 7 mounted radially to the axis of the annular coating 6. According to an alternative embodiment, it is possible to machine only the radial surface 7b intermediate insert 7.

In Figure 2 is illustrated a mounting 16 in which the rotary anode 1 is directly mounted on a rotating cylindrical drive shaft 17 of a machine (not shown). The rotary shaft 17 has an end portion 18 engaged, by a tight fit, through the mounting bore 12 of the intermediate insert 7 and has a radial peripheral shoulder 19 in contact with the rear face 7b of the intermediate insert 7, via a solder 20. The threaded end of the end portion 18 of the rotary shaft 17 is provided with a retaining nut 21 pressed against the front face 7a of the intermediate insert 7. Optionally, the retaining nut 21 can be fixed to the end of the shaft 17 by welding points 22. It follows from the above that the rotary anode 1 is mounted firmly on the shaft rotary 17 through the intermediate insert 7, previously fixed to the disk 2, without risk of damaging the material constituting the disc 2. In addition, the mounting bore 12 and the radial bearing surface 7b of the intermediate insert 7, previously machined and coupled to the rotary shaft 17, allow to ensure a rotation of the coating surface 6 concentrically to the rotary shaft 17 and without sail. According to an alternative embodiment illustrated in FIG. 3, the intermediate insert 7 can be fixed on the disk 2 by means of complementary axial tie-rods 23 which extend through through-holes 24 arranged parallel to the axis of the disk 2, between the opposed radial surfaces 4a and 5a, and the ends of which are engaged in and are welded to the annular portions 11 and 13 of the insert elements 8 and 9, for example by beam welding. electrons. For example, three tie rods 23 arranged at 120 ° can be provided. The tie rods 23 also constitute shear-abutting abutments against the pivoting of the intermediate insert 7 with respect to the disc 2. The tie rods 23 may consist of an alloy mainly of molybdenum, in particular of a titanium-zirconium alloy. Molybdenum (TZM), like the other elements constituting the intermediate insert 7. For the manufacture of the anode provided with the insert 7 of FIG. 3, it is possible to proceed as follows. A disc 2 is provided with the coating 6 and provided with through holes 24. The deposit 6 is machined. The insert 10 is provided with the holes 25 and the washer 13 is provided with the holes 26. The insert element 10 is assembled. , the washer 13 and tie rods 23 as described above, by inserting the solder materials. The solder is made. The ends of the tie rods 23 are welded to the insert element 10 and to the washer 13, for example by electron beams. Finally, the intermediate insert 7 is machined as previously described. According to an alternative embodiment illustrated in FIG. 4, as in the example of FIG. 3, complementary axial tie-rods 27 extend through through-holes 28 formed parallel to the axis of the disk 2, between the opposite radial surfaces. 4a and 5a. This time, one end of the rods 27 is screwed into a hole 30 of the annular portion 11 of the insert member 8, while the other end of the tie rods 27 passes through a hole 29 of the annular portion 13 of the insert element 9 and is provided with an outer retaining nut 31 resting on this annular part 13. For the manufacture of the anode provided with the insert 7 of FIG. a manner equivalent to that described with reference to Figure 3, the assembly of tie rods 27 including the establishment of nuts 31, the latter being subsequently welded by an electron beam. To adopt the arrangement of the assembly 16 described above with reference to Figure 2, the retaining nuts 31 must be sufficiently spaced apart so that the shoulder 19 of the rotary shaft 17 can bear against the rear face 7b of the According to an alternative embodiment illustrated in FIG. 5, the intermediate insert 7 comprises two opposite insert elements 32 and 33 that are symmetrical with respect to a median radial plane.

The insert elements 32 and 33 comprise cylindrical central portions or sockets 34 and 35 inserted, by a tight fit, into the axial receiving passage 3 of the disc 2 and the radial annular portions 36 and 37 in the form of washers which are support above the radial surfaces 4a and 5a of the front and rear faces 4 and 5 of the disk 2. Thus, the intermediate insert 7 has, as previously, a radial front face 7a and a radial rear face 7b. The central portions 34 and 35 are arranged axially at a distance from one another and have axial mounting bores 34a and 35a equivalent to the axial mounting bore 12 of the example described with reference to FIG. an alternative embodiment, the central portions 34 and 35 could be supported on one another. Equivalently to the example described with reference to FIG. 1, a fixing solder 38 is formed between the annular portion 36 of the insert member 32 and the front radial surface 4a of the disc 2 and on the other hand a solder 39 is formed between the annular portion 37 of the insert member 33 and the rear radial surface 5a of the disc 2. The installation and the subsequent machining of the insert members 32 and 33 can be performed in a manner equivalent to which has been previously described with reference to FIG. 1. The mounting of the disk 2 equipped with the insert elements 32 and 33 can be made equivalent to what has been described previously with reference to FIG. 2.

According to alternative embodiments, the insert elements 32 and 33 could be connected by rods equivalent to the rods 23 and 27 described with reference to FIGS. 3 and 4. According to an alternative embodiment illustrated in FIG. 6, the elements of FIG. insert 32 and 33 are connected by complementary axial tie rods 40 extending through through holes 41 and 42 formed in the central portions 34 and 35 of the insert elements 32 and 33 and formed parallel to the axis of the disc 2. Three axial tie rods 40 arranged at 120 ° can be provided.

One of the ends of the axial tie rods 40 can be screwed into the hole 42 of the central portion 35 of the insert element 33, while its other end extends forward and is provided with a nut of holding 43 bearing against the radial face of the central portion 34 of the insert member 32. The mounting of the tie rods 40 can be made as described above with reference to Figure 4. As illustrated in Figure 7, the anode 1 equipped with the insert 7 composed of the insert elements 32 and 33 and the tie rods 40 is mounted directly on the rotary cylindrical shaft 17 in a manner equivalent to that described with reference to FIG. , a hollow washer 44 is interposed between the retaining nut 21 and the end face 7a of the insert member 32, the recess 45 of which is adapted to remotely receive the retaining nuts 43. According to an alternative embodiment illustrated in Figure 8, an intermedia insert 46 comprises an insert element 47, for example equivalent to the insert element 32 described previously with reference to FIG. 5 and mounted in the same manner, and an annular insert element 50 in the form of a washer replacing the insert member 33 previously described with reference to Figure 5 and mounted in the same manner. The insert element 47 and the washer 50, which can be axially distant from each other or in abutment with one another, have axial mounting bores 47a and 50a equivalent to the axial passages 34a and 50a. 35a inserts elements 32 and 33 described above with reference to Figure 5. complementary axial tie rods 48 passing through the disk 2 and equivalent to the tie rods 27 of the example described with reference to Figure 4 are provided. In the same way, retaining nuts 49 screwed on the tie rods 48, equivalent to the nuts 31, bear directly on the radial rear surface 7b of the insert element 50 of the intermediate insert 46.

The anode 1 equipped with the insert 46 composed of the insert elements 47 and 50 and the tie rods 48 can be directly mounted on a rotary cylindrical shaft 17 in a manner equivalent to that described above with reference to FIGS. The end 18 of the rotary shaft 17 is fitted into the axial bores 47a and 50a of the insert elements 47 and 50, the shoulder 19 coming over the washer 50 and the nut 21 coming from above. of the insert element 47. It follows from the foregoing that the anode 1 comprising a disk 2 equipped with any one of the inserts described, constitutes a unit able to be mounted directly on a rotating drive shaft. a machine, for example an imaging machine including medical. The present invention is not limited to the examples described above. Alternative embodiments are possible without departing from the scope of the invention.

Claims (16)

REVENDICATIONS1. Rotating anode for X-ray emission, comprising a disk having an axial receiving passage and opposite faces surrounding this passage, and provided, on an annular zone of its surface, with a coating (6) capable of producing radii X under the effect of an incident beam of electrons, further comprising an intermediate fitting insert (7), fixed on the disc (2) and comprising at least one central portion (10) inserted into said axial receiving passage (3) of the disk and having an axial mounting bore (12) and at least one annular portion (13) bearing on one of said opposite radial faces (5a) of the disk and having a radial mounting face (7b). Anode according to claim 1, wherein said intermediate mounting insert comprises an insert member comprising said central portion and said annular portion. Anode according to claim 1, wherein said intermediate mounting insert comprises two insert members, one of which two insert members (8; 32,33; 47) including said central portion and said annular portion and the other insert member (9; 50) comprising an annular portion resting on the other of said radial faces of the disc. Anode according to claim 3, wherein said further insert member (33) comprises a central portion inserted into said axial disc receiving passage and having an axial mounting bore. Anode according to any of the preceding claims, wherein said intermediate mounting insert is attached to the disk by soldering. 6. Anode according to any one of the preceding claims, wherein said intermediate mounting insert is attached to the disk by tie rods. Anode according to claim 6, wherein said tie rods extend into the axial passage of the disc. Anode according to claim 6, wherein said link rods pass through the disk. Anode according to any one of the preceding claims, wherein the disk is at least partly made of a carbon-based material such as graphite or a carbon / carbon composite. 10. Anode according to any one of the preceding claims, wherein said intermediate fitting insert is attached to the disc by a solder and is made of an alloy predominantly molybdenum. 11. Anode according to any one of the preceding claims, wherein said intermediate fitting insert is fixed by a braze alloy alloy predominantly palladium. 12. A method of manufacturing a rotary anode for X-ray emission, comprising: producing a disk (2) having an axial receiving passage (3) and opposite faces (4a, 5a) surrounding this passage and provided, on an annular zone, a coating (6) capable of producing X-rays under the effect of an incident beam of electrons, mounting and fixing on the disk an intermediate fitting insert (7) comprising at least a part central unit (10) inserted in said axial passage of the disk and having an axial mounting bore (12) and at least one annular portion (11) bearing on one of said opposite radial faces (4a) of the disk. The method of claim 12, wherein the annular portion of the intermediate insert is attached to the disk by a solder operation. 14. Method according to one of claims 12 and 13, comprising: perform, before mounting the intermediate insert, a cylindrical machining operation of the annular coating. 15. Method according to one of claims 12 to 14, comprising: performing, after mounting and fixing the intermediate insert, a machining operation of the axial bore concentrically mounting said coating and a machining operation of the face of said annular portion radially to the axis of said coating. 16. Machine comprising a rotary shaft (17) on which is mounted an anode according to any one of claims 1 to 11.