Patent ID: 9339924
Filing Date: 2016-05-17
CPC Classification: B25D

Claim Text:
1. A hammer drill comprising: a housing; a tool holder mounted on the housing which is capable of holding a cutting tool; a motor mounted within the housing; and a hammer mechanism comprising; a piston reciprocatingly driven along a longitudinal axis by the motor when the motor is actuated; a ram reciprocatingly driven on the longitudinal axis by the reciprocating piston via an air spring; a beat piece supported in an axially slideable manner on the longitudinal axis within a beat piece support structure which, during the normal operation of the hammer mechanism, is repetitively struck by the ram and which transfers the impacts to a cutting tool when held by the tool holder; wherein the beat piece comprises a first impact surface and the beat piece support structure comprises a second impact surface, the first and second impact surfaces coming into contact with each other when the beat piece axially slides to its furthest position away from the ram; wherein the first impact surface is circular in cross-section in a first plane which extends perpendicularly from the longitudinal axis; such circular cross-section having a first center, and the second impact surface is circular in cross-section in a second plane which extends perpendicularly from the longitudinal axis, such circular cross-section having a second center, wherein the first and second centers are not on a same axis, and at least one of the first and second centers not being on the longitudinal axis.