Control of hydraulically powered equipment

A hydraulically powered hammer with adjustable delay hydraulic switching, said hammer comprising a ram, means guiding said ram for reciprocal movement along a given path and against an anvil, hydraulic piston and cylinder means connected to move said ram, a hydaulic switching valve connected to control operation of said piston and cylinder means and including a housing, a valve spool mounted for reciprocal movement along a bore within said housing, said housing being formed with passageways for a fluid which follows different paths for different positions of said valve spool, a pilot pressure line extending from a position on said hammer to an end of said valve spool to accumulate flows of pressure fluid when said ram reaches predetermined positions for supplying pressurized hydraulic fluid to produce movement of said valve spool, said valve including feedback means to hold same in each switched position until an actuation force is applied to said valve, fluid accumulation means comprising a chamber connected to said pilot pressure line to receive said flow of fluid, and means including a piston moveable in said fluid accumulation chamber between a first position defining an initial minimum chamber volume and a second position defining a final maximum chamber volume and responsive to the accumulation of a predetermined volume of fluid in said accumulation means for applying an actuating force to said valve, means for adjusting the duration between initiation of said fluid flow and said accumulation of a predetermined volume of fluid, and means biasing said last mentioned piston toward said first position.