Power-operated percussive tools

Claim 1

A POWER-OPERATED PERCUSSIVE TOOL COMPRISING A CASING, A TELESCOPICALLY-ENGAGED, RELATIVELY RECIPROCATABLE CYLINDRICAL DRIVER AND STRIKER WITHIN SAID CASING AND FORMING AN AIR CHAMBER THEREBETWEEN, MEANS IN SAID STRIKER FOR MOMENTARY VENTING SAID AIR CHAMBER TO ALLOW AIR TRAPPED THEREIN TO ADJUST TO A SUBSTANTIALLY CONSTANT WORKING LEVEL DURING NORMAL OPERATION OF THE TOOL AND ALSO EFFECTIVELY TO IMMOBILIZE THE STRIKER WHEN THIS MOVES APPRECIABLY BEYOND ITS NORMAL BLOW-STRIKING POSITION, AN ELECTRIC MOTOR MOUNTED ON ONE END OF SAID CASING, TOOL ROTATING MECHANISM SUPPORTED ON THE OTHER END OF SAID CASING, DRIVE MEANS ON SAID CASING DRIVEN BY SAID MOTOR FOR EFFECTING RELATIVE RECIPOCATORY MOVEMENT BETWEEN SAID DRIVER AND STRIKER AND A TOOL ROTATION DRIVE SHAFT EXTENDING PARALLEL TO THE LONGITUDINAL DRIVER-STRIKER AXIS.