X-ray tubes

Abstract

An X-ray tube comprises a generally cylindrical evacuated metal tube envelope having an anode rotatably mounted therein. [The interior of the tube envelope adjacent the anode is provided with ceramic insulation to prevent flashover.] The anode is rotated by an external variable speed DC drive motor magnetically coupled through the tube envelope wall to the rotating anode assembly. [The tube envelope wall includes ferrous segments which minimize the gap in the magnetic coupling while permitting a thick and strong tube envelope wall. A variable speed DC motor or a variable speed air motor may be employed to drive the anode. In preferred embodiments, the anode drive means is electromechanically clutched to the anode, whereby the drive means can be brought up to the desired anode speed and thereafter clutched to the anode, the drive means acting as a flywheel to bring the anode quickly up to speed. Electromagnets operating as clutches are also employed. Additionally, the anode drive means may be operated at high speeds suitable for radiography, and the electromagnetic clutch means may be intermittently operated to maintain the anode rotating during fluroroscopy. When a radiograph is required in the midst of fluoroscopy, the electromagnetic clutch is actuated to bring the anode up to its full speed. Alternate drive means include a DC stator external of the tube envelope acting on an internal rotor mounted to rotate with the anode. The X-ray tube further comprises a cathode rotatably mounted in the tube envelope and incorporating plurality of cathode filaments. Cathode rotation drive means are provided for rotating the cathode to select the desired filament. The cathode drive means is preferably magnetically coupled through the tube wall in order to rotate the cathode. Anode drive means also include]. The DC drive motor includes a DC stator external of the tube envelope operating on a rotor having encapsulated rare earth magnets [and an AC stator operating on a squirrel cage rotor through a laminated segmented tube wall]. A fan is provided for air cooling of the tube envelope.

Dependencies are inferred from the claim text.