Hammer drill

US5111890A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Ulrich Ranger · Leinfelden, DE
• Karl Wanner · Echterdingen, DE
• Johann Kaltenecker · Echterdingen, DE
• Manfred Hellbach · Echterdingen, DE
• Gerhard Meixner · Echterdingen, DE

Key dates

• Filing date: Jan 29, 1991
• Grant date: May 12, 1992
• Expiry date: Jan 29, 2011

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B25D2250/035
• WIPO field: Machine tools
• WIPO sector: Mechanical engineering

Abstract

A power hammer drill includes a tool holder and an air cushion striking mechanism for driving a tool and including a striker, a reciprocating piston for displacing the striker, and an axially displaceable guide tube for guiding the piston. A device for holding the striker in a forward position thereof adjacent to the tool holder in an idling condition of the hammer drill is provided in the hammer drill. The device has a guide element fixed in the drill housing for guiding the guide tube. The guide tube has a control opening for venting the air cushion and which remains in open or closed condition dependent on axial position of the guide tube.