Concrete breaker construction and valve mechanism

Claim 1

A fluid operated breaker particularly adapted to be employed for imparting repetitive blows to a tool to drive the tool into engagement with a surface comprising: a. a breaker housing including inlet means and outlet means, said housing having a multiplicity of bores formed therein and means for mounting a tool member at one end thereof; b. a piston supported in a first bore for movement therewithin alternately in a power stroke terminating with said piston adjacent said one end of said housing for imparting a blow to the associated tool and a return stroke terminating with said piston spaced from said one end of said housing, said piston having a stepped construction formed by a plurality of lands and grooves formed along the length of said piston providing a multiplicity generally radially extending shoulders, said shoulders providing a first force area facing towards said one end of said housing and a second force area facing oppositely from said one end with said second force area being larger than said first force area all said shoulders providing said force areas being spaced from the ends of said piston, and said housing and piston being cooperatively configured and dimensioned to preclude fluid communication through said first bore between said shoulders comprising said force areas and the ends of said piston whereby the high pressure fluid acting on said shoulders of said piston effects movement in both power and return strokes. c. switching means including a reversing valve spool having a stepped construction supported in a second bore for movement therewithin alternately between a first position and a second position operable to produce variation in the flow of fluid to said first bore and said second force effective area to cause said piston to alternately switch between movement in said power stroke and movement in said return stroke thereof; d. fluid circuit means fluidically interconnecting said inlet means, said outlet means and said multiplicity of bores operable to provide alternate fluid flow paths therebetween, said fluid circuit means being operable when said reversing valve spool is in said first position thereof to establish a first flow path for high pressure fluid from said inlet means to said first bore to cause high pressure fluid to be applied against said first force area of said piston and a second flow path for high pressure fluid from said first bore to and from said second bore to cause high pressure fluid to be applied against said second force area of said piston with the resultant force produced by the high pressure fluid acting on said first and second force areas of said piston causing said piston to accelerate in said power stroke thereof, said second flow path for high pressure fluid being cut off by said first force area of said piston as said piston moves in said power stroke thereof to cause the discontinuance of the flow of high pressure fluid against said second force area and thereby to terminate the force being provided by the high pressure fluid against said piston causing said piston to move in said power stroke thereof before said piston imparts a blow to the tool, said fluid circuit means in said second position of said reversing valve spool providing a first flow path for low pressure fluid from said first bore to said second bore to provide an exhaust path for low pressure fluid therebetween and a second flow path for low pressure fluid from said second bore to said outlet means to provide an exhaust path for low pressure fluid therebetween; e. accumlator means in a third bore in said breaker housing fluidically interconnected by said fluid circuit means with said first bore and operable as a storage means for storing energy therein during said return stroke of said pistOn and for releasing the energy stored therein during said power stroke of said piston to increase the force with which said piston imparts a blow to the tool; and f. variable restrictor means in one of said flow paths for low pressure fluid operable to vary the pressure in said low pressure fluid paths and thereby the pressure in the fluid circuit to said accumulator means to vary the energy stored therein during the return stroke of said piston.