X-ray or gamma ray systems or devices – Source – Electron tube
Reexamination Certificate
1998-09-10
2001-08-14
Font, Frank G. (Department: 2877)
X-ray or gamma ray systems or devices
Source
Electron tube
C378S133000, C378S135000, C378S121000, C378S125000, C378S131000, C378S144000
Reexamination Certificate
active
06275567
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a rotary anode X-ray tube which includes a sleeve bearing which serves to journal the rotary-anode and includes an inner bearing segment and an outer bearing segment which is provided with a holder, intermediate pieces being provided between the holder and the inner bearing segment and correspondingly formed bearing surfaces on the inner bearing segment and in the intermediate pieces being arranged to take up radial and axial bearing forces. The invention also relates to a sleeve bearing which is suitable for use in a rotary-anode X-ray tube.
2. Description of Related Art
A rotary-anode X-ray tube and a sleeve bearing of this kind are known from DE-GM 87 05 478. Therein, the outer surfaces of the intermediate pieces are adapted to the tubular holder whereas their inner surfaces are adapted to the bearing surfaces on the inner bearing segment which have the form of a truncated cone. A bias force, applied to one of the intermediate pieces and produced by a spring, ensures that the bearing clearance remains constant also when the temperature of the sleeve bearing increases; however, the starting moment is thus also increased.
The bearing capacity of a sleeve bearing is dependent particularly on the distance between the bearing faces co-operating in the inner and the outer bearing segments. The bearing capacity of the sleeve bearing is greater as this distance is smaller. In practice this distance is of the order of magnitude of 10 &mgr;m. Such small distances, which should also remain constant across the bearing surfaces, can be achieved only by costly precision manufacture. In comparison with sleeve bearings which have bearing surfaces extending perpendicularly to the axis of rotation so as to take up the axial bearing forces and at least one cylindrical bearing surface for taking up the radial bearing forces, the known sleeve bearing offers the advantage that only two bearing surfaces (having the shape of a truncated cone) must be formed with the necessary precision on the inner bearing segment and in the intermediate pieces.
Moreover, however, the external surfaces of the intermediate pieces which are arranged in the tubular holder must also extend exactly concentrically with the conical bearing surfaces provided therein, because the bearing surfaces will otherwise be tilted. Finally, the outer diameter of the intermediate pieces must be very accurately adapted to the inner diameter of the tubular holder in order to ensure that on the one hand the intermediate pieces can slide in the tubular holder and that on the other hand no play remains between the facing surfaces of the intermediate pieces on the one side and the tubular holder on the other side.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a rotary-anode X-ray tube which includes a sleeve bearing that can be more readily manufactured. On the basis of a rotary-anode X-ray tube of the kind set forth, this object is achieved in that the facing surfaces of the intermediate pieces and the holder are formed in such a manner that the intermediate pieces within the holder are aligned with the bearing surfaces.
Because of the shaping of the facing surfaces of the holder and the intermediate pieces according to the invention it is achieved that the bearing surfaces in the intermediate pieces are aligned with the bearing surfaces on the inner bearing segment even when the external surfaces of the intermediate pieces which come into contact with the holder do not extend exactly concentrically with respect to the bearing surfaces provided therein. Thus, in a sleeve bearing of this kind it is only important that the bearing surfaces in the intermediate pieces on the one side and on the inner bearing segment on the other side correspond exactly.
The inner surfaces of the holder and the outer surfaces of the intermediate pieces which come into contact therewith must be formed so that the intermediate pieces can be tilted relative to the holder. The maximum tilt angle required is dependent on the precision of manufacture; however, it can be easily kept small, for example less than 1°. To this end, both of said surfaces may be shaped as a segment of sphere as in a spherical bearing. However, the manufacture is easier when said surfaces are formed in conformity with the claims
2
and
3
.
The bearing surfaces must be shaped so that they are capable of taking up radial forces on the one hand and axial bearing forces on the other hand, the axial bearing forces to be taken up by the two bearings being oppositely directed. The normals to the rotationally symmetrical bearing surfaces, therefore, may extend neither parallel with nor at right angles to the axis of rotation, at least not in a given region. A shape of the bearing surfaces that can be comparatively easily realized is disclosed in claim
4
.
Claim
5
describes an embodiment which facilitates the assembly of the sleeve bearing. In conformity with one embodiment, the adjustment of the two parts, and hence the adjustment of the bearing play, can be performed by screwing one part more or less far into the other part. The bearing play governing the operation of the sleeve bearing, therefore, is not imposed by high-precision manufacture, as in rotary-anode X-ray tubes with separate bearing surfaces for the axial and radial bearing forces, but by means of a simple adjusting operation.
Generally speaking, the friction between the intermediate pieces and the holder suffices to prevent rotation of the intermediate pieces relative to the holder during rotation of the sleeve bearing. However, if necessary, the possibility of such rotation can be completely precluded by means of the embodiment disclosed in claim
7
.
The claims
8
and
9
disclose possibilities for connecting the bearing segments to the envelope of the X-ray tube. The alternative disclosed in claim
8
offers the advantage that heat can be discharged from the bearing via an inner bore which extends inside the inner bearing segment in the direction of the axis of rotation.
REFERENCES:
patent: 4210371 (1980-07-01), Gerkeman et al.
patent: 8705478.7 (1988-09-01), None
Font Frank G.
Rodriguez Armando
U.S. Philips Corporation
Vodopia John F.
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