GB1438317A - Rotary-anode x-ray tubes - Google Patents

Abstract

1438317 Magnetic bearings SIEMENS AG 19 Dec 1973 [21 Dec 1972] 58964/73 Heading F2A [Also in Divisions G3 H2 and H1] A rotary anode X-ray tube is supported mechanically by only bearing 24, additional anode support being provided by magnetic bearing means in a radial direction, the mechanical bearing serving also to conduct current by way of the anode. The magnetic bearing means may additionally give axial support. The bearing in Fig. 1 includes a stack of aligned annular e.m. coils 9 to 15 with a second stack of coils 36 to 42 producing opposed fields, rotor 27 having two hollow cylindrical parts and magnetically conductive annular yoke members 28 to 35. Shaft 25 is axially supported by the mechanical end bearing 24 which with the tensioned disc 7<SP>1</SP> electrically contacts connecting socket 7. Cylinder 71 carries further yoke members 43 to 50 while the drive part 51 on rotor 71 is surrounded by stator winding 52. Electrically connected cylinder 72 protects members 43 to 50 from high anode potentials. Eccentricity is detected by capacitance measurements between probe 60 and cylinder 72 using device 55 which also controls the current to the coils so that rotor 27 is subjected to forces which counteract the eccentricity only for long enough to prevent the rotor hunting about its central position. Shaft 25 length is such that the axial supports is at 103, the intersection between the shaft axis and a perpendicular from target surface 102. To facilitate assembly, the inner cylinder of the rotary part, with its annular members, may be split. Fig. 3 (not shown) includes drive part (51<SP>1</SP>) between anode plate and coil stacks and is preferable for high loads. External stack (80) should be at anode potential in view of the narrower gap between members (81), (82) and 83 to 85) the latter penetrating the envelope. Fig. 4 (not shown) includes mid-way drive part (51<SP>11</SP>). Gap (87<SP>1</SP>) corresponds to gap (87) of Fig. 3. Members (83<SP>1</SP>-85<SP>1</SP>) and (97, 98) are retained by lining (100) rather than penetrating the envelope as in Fig. 3. Ball bearing (104) provides the mechanical support against the flat or concave shaft end. Reference is made to permanent magnets and to e.m. coils fixed to the rotary shaft and employing slip-rings or induction coils.