SPEED CHANGING DEVICE FOR TOOLS HAVING A GEAR ASSEMBLY WITH A VARIABLE GEAR RATIO

摘要

SPEED-CHANGING DEVICE FOR TOOLS HAVING A GEAR ASSEMBLY WITH A VARIABLE GEAR RATIO The invention is directed to a speed-changing device for a tool having a gear-box housing and a gear assembly arranged in the housing. The gear assembly has a gear cluster which is movable between at least two positions for changing the gear ratio of the gear assembly. The speed-changing device includes an annular guide member adapted to snap into an opening in the gear-box housing for firmly holding the device in the housing. A cylindrical member is rotatably mounted in the annular guide member and defines a longitudinal axis of rotation. A head piece is securely mounted on the cylindrical member and has an elongated projection extending therefrom eccentric to this axis. The elongated projection engages the gear cluster to move the same from one position to another in response to a manual actuation of the cylindrical member. The cylindrical member is configured to contact the guide member to conjointly define therewith a sealing interface. A resilient member is interposed between the head piece and the guide member for resiliently loading the cylindrical member with respect to the guide member thereby causing the cylindrical member to press against the guide member at the sealing interface whereby an effective seal between the members is established to prevent lubricating liquid from flowing out between the members from the gear-box housing.