Automatic two-position four-way pulsating valve

Pulsating hydraulic valve apparatus for directing flow of hydraulic fluid in a manner to control operation of a hydraulic cylinder, comprising:

• a valve body having an elongated spool bore therein with a longitudinal axis that defines a longitudinal axis of the valve and having a first end and a second end, a pressure port extending transversely through said valve body into said spool bore, a first feed port and a second feed port, each of which extends transversely through said valve body into said spool bore at longitudinally short spaced distances on longitudinally opposite sides of said pressure port, a first drain port and a second drain port, each of which extends transversely through said valve body into said spool bore at longitudinally long spaced distances on longitudinally opposite sides of said pressure port, wherein said longitudinally long spaced distances are greater than said longitudinally short spaced distances, a first bypass port extending between and connecting said first end of said spool bore and said first drain port, a second bypass port extending between and connecting said second end of said spool bore and said second drain port, first plug means for closing said first end of said spool bore, and second plug means for closing said second end of said spool bore;
• an elongated shuttle spool having a first end and a second end positioned slideably in said spool bore and moveable longitudinally between a first position and a second position in said spool bore, said shuttle spool being longer than the distance between said first and second drain ports but shorter than said spool bore, said shuttle spool also having a diameter large enough to substantially fill said spool bore, but also having a first cavity and a second cavity, each of which first and second cavities is depressed into the peripheral surface of the shuttle spool a sufficient amount to allow fluid to flow in said first and second cavities between said spool and said valve body, said first cavity being long enough and positioned such that it spans and connects said pressure port and said first feed port when said spool is in said first position and such that it spans and connects said first feed port and said first drain port when said spool is in said second position, said second cavity being long enough and positioned such that it spans and connects said second feed port and said second drain port when said spool is in said first position and such that it connects said pressure port and said second feed port when said spool is in said second position, said spool also having a first control bore extending longitudinally therein from said first end of said spool and a second control bore extending longitudinally therein from said second end of said spool, a first shunt port extending from said first cavity to said second control bore, and a second shunt port extending from said second cavity to said first control bore;
• first control valve means positioned in said first control bore for blocking fluid flow through said first control bore to said first end of said spool bore to move said spool toward said first position and alternately for allowing fluid flow through said first control bore when said spool moves toward said second position;
• and
• second control valve means positioned in said second control bore for blocking fluid flow through said second control bore to said second end of said spool bore to move said spool toward said second position and alternately for allowing fluid flow through said second control bore when said spool moves toward said first position.