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:
Sep. 05, 1995
Filed:
Aug. 03, 1994
Andreas Stihl, Waiblingen, DE;
Abstract
The invention is directed to an ignition circuit for an internal combustion engine in a portable handheld work apparatus wherein a work tool is driven via a clutch. The ignition circuit includes an ignition time point control which connects a spark plug via a switch to a voltage source in order to trigger an ignition spark. The spark plug is mounted in the combustion chamber of the engine. This connection takes place in dependence upon the crankshaft angle and the rpm of the engine. In order to prevent damage to the clutch because of a blocked work tool, a test value counter driven via a rpm gate circuit is provided. The test value counter increments its value in the pregiven rpm window of the gate circuit with each rotation of the crankshaft and the content of the test value counter is compared to a pregiven limit value by a comparator. The output of the comparator activates a rpm-reducing protective circuit and the output of the comparator indicates reaching or exceeding the limit value.