Start safety circuit arrangement in a work apparatus having an internal combustion engine

摘要

A start safety circuit arrangement is incorporated into a work apparatus having an internal combustion engine. Combustion air and fuel are supplied to the combustion chamber by a control unit for the engine operation. The fuel/air mixture in the combustion chamber is ignited by an ignition plug. An operating mode selector has a start position for enriching the fuel/air mixture. A safety brake device in an operating mode brakes the work tool. A start position sensor is arranged on the operating mode selector and a brake position sensor is associated with the safety brake device. The status signal of the brake position sensor and the status signal of the start position sensor are combined to cause the control unit to disable the engine operation if the operating mode selector is in start position (III) and the safety brake device is in its standby mode (B).

主权项

1. A start safety circuit arrangement in a work apparatus, the work apparatus including an internal combustion engine having a cylinder defining a combustion chamber and having a spark plug in said combustion chamber; said internal combustion engine further having an ignition module connected to said spark plug; a control unit configured for the operation of said engine by controlling a supply of combustion air and fuel to said combustion chamber to form an air/fuel mixture and igniting said air/fuel mixture via said spark plug connected to said ignition module; an operating mode selector having several positions and being configured for bringing said engine into operation; said several positions including an off position (I), an operating position (II) and a start position (III) for enriching said air/fuel mixture; a short circuit switch connected to said ignition module; said operating mode selector being configured to actuate said short circuit switch in said off position (I) to short circuit said ignition module and to open said short circuit switch in said operating position (II) to make said ignition module active; a work tool operatively connected to said engine; a brake unit operatively connected to said work tool; and, a safety brake device configured to brake said work tool via said brake unit in an operating state of said work tool and configured to enable said work tool in an operationally-ready state (B) when said brake unit is released; and, said start safety circuit arrangement comprising:
an operation sensor assigned to said safety brake device and configured for emitting a first status signal as to the operating state of said safety brake device; a position sensor arranged on said operating mode selector and configured for emitting a second status signal; and, a circuit for combining said first and second status signals so as to cause said control unit to disable said operation of said engine when said operating mode selector is in said start position (III) and said safety braking device is in said operationally ready state (B) with said brake unit released.