Control of hydraulically powered equipment

A hydraulically powered hammer with adjustable delay hydraulic switching 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 hydraulic 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 switched positions of said valve spool;
• said valve including feedback means to hold the spool in each switched position until an actuation force is applied thereto;
• valve actuation means comprising pilot fluid supply means for initiating a flow of pilot fluid from said cylinder to said valve upon the passage of said ram past a predetemined location along said path;
• said valve further including fluid accumulation means connected to receive said flow of pilot fluid through a pilot pressure line, said accumulation means including at least one fluid accumulation chamber located at one end of said valve spool, a piston in said chamber for movement in the direction of said spool and spool contact means extending from said piston toward said one end of said spool for applying an actuating force to said spool in response to the accumulation of a predetermined volume of fluid in said accumulation chamber, said contact means having a length such that a finite gap exists between said contact means and said spool when said piston is furthest away from said spool and the spool is in its extreme position toward said piston and means for adjusting the duration between said initiation of pilot fluid flow and said accumulation of a predetermined volume of fluid.