Portable handheld work apparatus

摘要

The invention is directed to a portable handheld work apparatus including a motor-driven chain saw, cutoff machine and the like. The work apparatus includes a housing and an internal combustion engine mounted in the housing for driving a work tool. The housing defines a space from which said engine draws combustion air and a fan wheel is disposed in the housing for generating a cooling-air flow which leaves the fan wheel in a direction tangential to the periphery of the fan wheel for cooling the engine. The housing has a U-shaped channel for conducting the cooling-air flow. The U-shaped channel is disposed so as to face toward the fan wheel with the base wall thereof being disposed at a predetermined spacing from the periphery of the fan wheel. The U-shaped channel has a pass-through formed in the base wall at a pregiven spacing downstream from the fan wheel for passing a portion of the cooling-air flow to the space as combustion air for the engine. The pass-through defines a plane and a center axis perpendicular to the plane. The U-shaped channel is configured to impart a predetermined direction of flow to the cooling-air flow at the region of the pass-through and the center axis and the predetermined direction of flow conjointly define an angle beta having a value in a range of approximately 70 DEG to 180 DEG .