GB854363A - Improvements in x-ray tubes with rotating anodes - Google Patents

Abstract

854,363. X-ray tubes. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Feb. 20, 1957 [Feb. 20, 1956(2); April 25, 1956 ; Dec. 21, 1956], Nos. 5172/56, 5173/56, 12761/56 and 38939/56. Class 39(1). In an X-ray tube in which a cathode and rotating anode are housed in a hollow column, the fluid-cooled anode rotates on an axis transverse to that of the column, and the wall of the column adjacent the cathode has a fluid-cooled lining, both fluid flow-paths being in parallel. As shown the envelope casing 1 is of rectangular section, and is exhausted from the lower end. Electrons from the cathode 15 impinge on the opposed surface of the anode drum 6, the X-rays issuing through four circumferentially spaced windows 20. Scattered electrons are absorbed by a hollow copper block 13, of double-shell construction so that it can be water-cooled, and which also acts as a focusing element. The water passing through the jacket 17 is drawn off in parallel from the water supply for the rotary anode. The block 13 and the whole anode assembly are mounted on a carrier plate 12, which is secured by bolts 36 and a tongue-and-groove joint 37, 38 to the main casing 1. Thus the block 13 and anode assembly can readily be removed bodily for servicing and cleaning, by detaching the plate 12 on which they are mounted, Fig. 1. A resilient member 35 recessed into the main casing forms a seal with the plate 12. The main casing carries the riser and return pipes 31, 32 for the cooling water. These pipes detachably connect into union blocks 29, 30 on plate 12 from which pipes 47, 48 convey the water to and from the anode rotor. The cup-shaped rotor 53, 54 is carried on a hollow shaft 48 integral with a driven pulley 9. Within the rotor is a cup-shaped baffle 51. The water enters through a tube 56 coaxially within shaft 48, circulates within the rotor over one side of the baffle and then over the other side, as shown by the arrows, and then returns through shaft 48 into a compartment 62 to which an outflow pipe is connected. The compartment 62 is sealed to a stepped return tube 63 which fits tightly into the shaft 48 by means of a synthetic resin bush 66. A hole 67 allows water to seep through to lubricate the bush. The shaft 48 fits into a sleeve 72 of high-grade hardened steel, which is very accurately lapped to an optical finish, and rotates in ball-bearings 10. Round the sleeve fits a pair of sealing rings 76, 77, preferably made of a synthetic rubber having low abrasive content and low coefficient of friction, such as hydrocarbon or chlorocarbon rubbers loaded with molybdenum disulphide, or fluorocarbon rubbers. The sealing rings are separated by a spacer 79, in which a gap 80 admits oil from a duct 81 leading to an oil reservoir 82. The anode is rotated by a pulley 9 over which passes a belt 7 from a motor. A spring-loaded carbon earthing brush 71 bears against pulley 9. Ion gauges 88, 89 are provided for measuring the vacuum, and may use the rotor itself as anode. In a modified construction, Figs. 10-12 (not shown), the main casing, instead of being rectangular, is of drum-like configuration, concentric with the rotor. The rotor and waterinjector assembly can be removed by detaching the plate 12. In this form the block 13 is not removed bodily with the plate 12, as in the firstdescribed construction. Provision may be made for coating the anode rotor with various metals in situ by evaporation techniques. Such metals are Mg, Al, Ti, Ge, V, Mn, Zn, Pb and Bi.