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:
Jan. 15, 1985
Filed:
Oct. 22, 1981
Klaus Gunther, Stuttgart, DE;
Friedrich Hornung, Stuttgart, DE;
Kurt Paule, Stuttgart, DE;
Fritz Schadlich, Leinfelden-Echterdingen, DE;
Robert Bosch GmbH, Stuttgart, DE;
Abstract
To permit operation of the power tool only if both hands of an operator are engaged, the tool is formed with a handle portion which has a sensing surface thereon, electrically coupled to a current flow sensing circuit, preferably including an opto-coupler or a field-effect transistor (FET) circuit which permits firing of a triac, thyristor, or the like only if current flows over the sensing surface by area contact therewith. The sensing surface is energized, preferably, from a resistive or capacitative voltage divider; the capacitative voltage divider has the advantage that the triac firing circuit can cause the triac to fire during null or zero crossings of ac supplied power. If a locking-type switch is used, two handles or touch-areas are needed; if a spring-loaded switch is provided, it can function as one safety element, and a touch-area sensing surface as the other.