US 3322993 A
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May 30, 1967 M. VINOPAL 3,322,993
YGETTER BODY MOUNTED ON LOW THERMAL CONDUCTIVITY SUPPORTS Filed May 19, 1964 IN VEN TOR.
United States Patent 3,322,993 GETTER BODY MOUNTED 0N LOW THERMAL CONDUCTIVITY SUPPORTS Miroslav Vinopal, Prague, Czechoslovakia, assignor to Chirana Praha, narodni podnick, Prague, Czechoslovakia, a corporation of Czechoslovakia Filed May 19, 1964, Ser. No. 368,674 Claims priority, application Czechoslovakia, May 23, 1963, 2,967/ 63 3 Claims. (Cl. 313-174) This invention relates to high vacuum tubes, primarily X-ray tubes, and more particularly to gettering means used in said tubes.
In X-ray tubes which have been evacuated to a high degree and sealed by melting olf the evacuating conduit, gases absorbed in materials within the tube are released, particularly during the operation of the tube and are removed continuously during said operation of the X-ray tube by ion absorbing means. The materials upon which quick ions generated in the electron beam of the X-ray tube impinge are inefiective getters and the absorption of the gas molecules is mostly not permanent. In the course of the life time of the X-ray tube, the desorption is frequently not in equilibrium with the absorption, so that the vacuum deteriorates. It is therefore necessary to use getter, which has to be heated to a relatively high temperature; such heating required an additional electric circuit in the X-ray device. It is an object of this invention to obviate such an additional electric circuit.
In accordance with this invention this is achieved by locating the getter within the cathode body of the X-ray tube in the neighbourhood of the hot cathode without heat-conductiviely connecting it to the cathode or its body so that the getter is heated exclusively by heat radiation from the cathode to a temperature of at least 600 C. in order to transmit to the getter the maximum of heat by heat radiation.
An embodiment of the invention is illustrated in the accompanying drawing wherein FIG. 1 shows a cross section of the X-ray tube in a plane perpendicular to the heating filament and, FIG. 2 a cross section in a plane containing the heating filament.
A getter 3 composed of titanium sheets is placed within the cathode body 1 of an X-ray tube close to the hot cathode 2 to be heated by its radiated heat.
The getter 3 is suspended on a tungsten Wire 4, which extends in a supporting body 5 and is relatively thin, in order to at least practically prevent any heat transmission to the cathode body 1. The supporting body 5 of the getter 3 is inserted into a lateral opening of the cathode body 1.
The getter 3 composed of a number of titanium sheets is protected by a tubular screening body 6 of a metal having less afiinity to oxygen than titanium in order to prevent atoms released by quick ions to reduce oxides of the glass of the X-ray tube. An advantage of my new construction is the small heat transfer between the getter 3 and the cathode body 1 and consequently the mainice tenance of the possibly highest temperature, say at least 600 C., of the getter 3 exclusively by heat radiated by hot cathode 2.
Quick ions generated in the electron beam of the X-ray tube impinge upon the getter of this design, and pass around the hot tungsten cathode 2. These ions cause the evaporation of material upon which they impinge. It is not desirable that the chemically very aggressive evaporated getter atoms attack for instance glass and it is therefore suitable to protect the place where the quick ions impinge by some material With smaller chemical afiinity to oxygen than titanium, for instance by molybdenum.
The heat conductivity of the getter supports 4, 5 should be chosen so, that the temperature of the getter in the course of operation of the X-ray tube is maintained at or above about 600 C. to make the getter etfective even for absorption of nitrogen.
While a specific embodiment of my invention has been shown and described to illustrate the application of the principles of my invention, it will be understood that the same may be otherwise embodied without departing from such principles.
In the appended claims which define my invention the reference characters are included to facilitate the reading of the claims with reference to the specification and drawing and they are not to be consideerd as limiting the scope of the claims.
1. In a high-vacuum tube particularly an X-ray tube the improvement comprising in combination a cathode body 1) including a directly heated cathode (2); a getter body (3) inside the tube close to but heat-conductively detached from the cathode (2) to be heated therefrom exclusively by radiated heat; and a support (4, 5) for the getter body at least practically heat-conductively separating the getter body from the cathode body (1) and thus saving the getter body from loss of heat received by radiation and maintaining its temperature at least at about 600 C.
2. A high-vacuum tube according to claim 1 wherein said support comprises a stretched wire (4) of low heat conductivity holding the getter body in suspended position.
3. A high-vacuum tube according to claim 1 comprising a screening body (6) of a material of lower afiinity to oxygen than titanium, said screening body shielding the getter body (3) to prevent atoms released by quick ions from reducing oxides contained in portions of the tube.
References Cited UNITED STATES PATENTS 2,523,016 9/1950 Hamuas 313-180 2,900,549 8/1959 Doolittle 313174 X 2,948,607 8/1960 Wagener 313-174 JAMES W. LAWRENCE, Primary Examiner. S. A. SCHNEEBERGER, Assistant Examiner.