The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 15, 1977
Filed:
Mar. 31, 1975
Geoffrey William Green, Malvern, EN;
Donald Thomas Hurle, Welland, EN;
Gordon Charles Joyce, Malvern, EN;
National Research Development Corporation, London, EN;
Abstract
The Czochralski growth of a crystal may be automatically controlled to provide uniform crystal cross-sectional area by weighing the crucible containing the melt from which the crystal is grown and deriving a weight signal which is compared with its expected value to produce a feedback loop control signal to control the melt heater power. However a magnetic field will be associated with the melt heater current and the interaction of this field on the crucible can produce a levitation force which is recorded erroneously as part of the weight signal. This unwanted force can make the closed-loop control unstable. The error component in the weight signal is cancelled in the invention by deriving an equal and opposite component by monitoring the current supplied to the melt heater and adding the derived component to the weight signal in the feedback loop.