US 2939015 A
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F. REINIGER May 31, 1960 X-RAY TUBE Filed April 12, 1957 INVENTOR FRIEDRICH REINIGER AGENT United States Patent X-RAY TUBE Friedrich Reiniger, Hamburg, Germany, assignor to North American Philips Company, Inc., Irvington-on- Hudson, NY.
Filed Apr. 12, 1957, Ser. No. 652,413
Claims priority, application Germany May 8, 1956 Claims. (Cl. 250-90) X-ray tubes are frequently disposed in a closed envelope made wholly or substantially of metal. When the tube is made operative, the envelope acquires earth potential and must be perfectly insulated with respect to the tube. For this purpose the space between the Wall of the tube and the envelope is filled with oil.
In rotary-anode tubes the envelope also contains the stator, which serves to drive the rotary anode and which is likewise contained in the space filled with oil.
It may happen that the oil-filling does not provide suflicient insulation and in time electric discharge occurring in the envelope deteriorates the tube. This is attributable to small air bubbles remaining in the envelope. Thus, when filling the envelope, it is necessary to proceed very carefully in order to avoid the inclusion of air. A rotary-anode tube causes greater difiiculty in this respect than ordinary X-ray tubes, since the surface of the stator is usually not perfectly smooth, resulting in small-air-chambers which are not filled with oil even if the air is expelled by heating and evacuation of the envelope.
The object of the invention is to obviate said disadvantage. According to the invention, the stator of the rotaryanode tube is cast in cast resin before being introduced into the envelope. For this purpose use may be made of the material known under the name Araldite. A very suitable method is to add to the cast material about 50% by volume of quartz, so that stress due to contraction which may occur in the object after casting is substantially avoided. Furthermore, it is thus achieved that the power of dissipating heat from the enclosed winding is increased with respect to ordinary cast resin.
In order that the invention may be readily carried into effect, it will now be described more fully, by way of example, with reference to the accompanying drawing, showing one embodiment of a rotary-anode X-ray tube with stator provided with an envelope to which the in vention is applied.
An envelope 1, substantially cylindrical in shape, carries at each extremity a declaration cap 1*, respectively 1 The Wall of the envelope has a window 2 from which the X-rays emanate which are produced in an X-ray tube 5. The latter comprises a cathode 3 and a rotatably arranged anode 4. The high tension is sup- 2,939,015 Patented May 31, 1960 plied via cables which are connected to the envelope in known manner by means of plug sockets 6. The stator which, upon energisation, provides the electric field driving the anode 4 is disposed between the wall of the X-ray tube and the envelope. A stator core 7 and its winding 8 are cast in cast resin 9 which preferably contains about 50% by volume of quartz. The surface of the cast workpiece may be perfectly smooth, so that. the air is expelled throughout when the envelope is filled with oil. The figure also shows a convenient method of securing the stator; For this purpose, the wall 13 of insulating material, which closes the anode end of the envelope 1, is provided with an annular upright edge 10. The edge 10 extends in the envelope and its extremity carries the stator. The Wall 13 with its upright edge 10 and the stator may be united to form one casting. The wall 13 also supports the X-ray tube 5 by means of a supporting cap 11 which for this purpose is cast in the wall. Lead-through devices 12 for the supply wires of the stator Winding 8 are likewise provided in the Wall 13.
What is claimed is:
1. An X-ray tube comprising an oil-filled envelope, a motor stator completely disposed in the oil-filled envelope for cooperating with and driving a rotary anode, and a smooth-surfaced insulating member completely surrounding and enclosing the stator to minimize the possibility of air bubbles remaining in the envelope after it is filled with the oil.
2. In an X-ray tube of the type comprising a rotary anode, a motor stator for driving the anode, and an oilfilled envelope surrounding and enveloping the stator, the improvement comprising completely embedding the stator in a casting resin so as to provide a smooth exterior and minimize the possibility of entrapping air when the envelope is filled with the oil.
3. The X-ray tube as claimed in claim 2, wherein the casting resin contains about 50% by volume of quartz.
4. An X-ray tube comprising a rotary anode, a motor stator for driving the anode, an oil-filled envelope enclosing the stator, and a cast resin member having a lower portion completely enclosing the stator and an upper portion constituted of an annular upright edge secured to the envelope and thus serving to support the stator.
5. A tube as claimed in claim 4 wherein the upper portion of the cast resin member includes a wall member secured to and supporting the anode portion of the tube.
References Cited in the file of this patent UNITED STATES PATENTS 1,662,891 Mutscheller Mar. 20, 1928 1,933,005 Bouwers Oct. 31, 1933 2,118,457 Bouwers May 24, 1938 2,121,630 Gross et al June 21, 1938 2,216,888 Machlett Oct. 8, 1940 2,222,729 Ver Planck et a1. Nov. 26, 1940 2,307,612 Westendorp Jan. 5, 1943 2,601,042 Marks June 17, 1952