X-ray device

Claim 1

An X-ray device, comprising in combination, an X-ray tube of the rotating anode type having a rotatable stem and an anode plate mounted upon said rotatable stem, at least two electronemitting cathodes spaced from said anode plate, and at least two concentric annular target tracks of different obtuse face angles formed on said anode plate, each of said target tracks being associated to one of said cathodes, a manually operated switch for selecting one of said cathodes to be activated, an X-ray screen for fluoroscopy mounted at a radial distance from the anode in a plane parallel to the axis of revolution of said rotating anode and being adjusted to X-rays emitted from the target tracks in a radial direction rectangular to said axis of revolution, two pairs of adjustable collimator plates mounted between the target tracks and said X-ray screen parallel to said X-ray screen and an automatic switching device comprising at least one changeover switch for said cathodes, actuated by said pair of collimator plates adjustable in a direction parallel to the axis of revolution, said automatic switching device switching on said cathode being associated to the target track having the bigger face angle when the selected adjustment of said pair of collimator plates exceeds a predetermined opening of the radiation beam larger than twice the angle of the surface of said target track having the smaller face angle with a plane normal to the axis of revolution, said switching device switching out said cathode being associated to the target track having the smaller face angle even when it has been manually selected, and wherein said predetermined opening of the radiation beam is effected when the planes of the X-ray emitting areas of the respective target tracks touch the edges of the collimator plates and the opposed edges of the usual film sizes being fixed in the plane of said Xray screen.