| 摘要 |
1,272,018. Automatic control of stress. TEXAS INSTRUMENTS Inc. June 19, 1969 [July 11, 1968], No.31035/69. Heading G3R. Apparatus for controlling the stress in a heated semi-conductor filament 20 comprises two chucks 22, 24, the position of one of which is controlled by means responsive to the variation of stress in the filament. The chucks are mounted on water cooled electrodes 26, 44 by which heating current is passed through the filament and which are supported by bellows 38, 52, flexible diaphrams or roll seats within a gas tight quartz tube 10. The filament 20 is a substrate for the growing of a silicon or germanium crystal by deposition from a vapour. Stress occurs in the filament when thermal expansion causes it to push down the lower electrode and is determined by measuring the displacement of this electrode. In Fig. 1 this is effected electrically by a differential transformer 60 with movable core 68, or by a strain gauge bridge, the signal from which operates a servomotor 74, to raise the upper chuck until the lower chuck, and hence the stress, are restored to their original condition. In Fig. 2 (not shown) the servomotor 74 is replaced by a pneumatic valve which controls an air supply to bellows 52. |
