Paving breaker

Abstract

A paving breaker for the construction industry of the type having a vibrating moil point or tool steel impacted by a pneumatically reciprocated piston including a double walled cylinder slidably receiving the piston designed so that the space between the inner and outer walls of the cylinder forms a passageway for delivery of piston return air to the lower cylinder chamber and the space also forms an accumulator for air compressed by the piston during the lower part of its power stroke. In one embodiment an outer cylinder sleeve is mounted on an elastomeric member surrounding an inner cylinder sleeve, and is free to reciprocate a limited distance in the housing to partly balance the reaction forces of the piston. This double walled cylinder is surrounded by rectangular polyurethane covers that form an air exhaust space around the cylinder so that exhaust air assists in cooling the cylinder. Air is ported to the opposite ends of the cylinder by a self guiding valve member that has easily machined expansion grooves on opposite sides of a metering land and an annular guide stem that is slidably mounted in a bore in a lower valve block member mounted at the top or backhead of the paving breaker adjacent the cylinder, and this valve guide stem forms a conduit for air to the rear side of the piston.