Automatically-reversing piston-and-cylinder unit

An automatically-reversing, fluid-actuated piston-and-cylinder unit, which comprises:

• (a) a cylinder comprises:
• (1) first and second ends;
• (2) a bore extending longitudinally between said first and second ends;
• (3) first and second sections associated with said first and second ends respectively;
• (4) a first cylinder plug closing said first cylinder end;
• and
• (5) a second cylinder plug having a bore and closing said second cylinder end;
• (b) a piston/valve assembly including:
• (1) a piston subassembly having a piston rod with first and second ends and a piston mounted on said first end, said piston being reciprocably received in said cylinder first section and having first and second sides;
• (2) a spool valve subassembly having a spool valve member with first and second ends and a longitudinally extending bore slidably receiving said piston rod, said spool valve member second end extending through said second cylinder plug bore, said spool valve member having a first position communicating pressurized fluid from said cylinder second section to said piston first side and a second position communicating pressurized fluid from said cylinder second section to said piston second side;
• (c) said piston dividing said cylinder first section into a first piston fluid chamber associated with said first piston side and a second piston fluid chamber associated with said second piston side;
• (d) said spool valve member having a plurality of lands dividing said cylinder second section into first and second return fluid chambers, a supply fluid chamber and an equilibrium fluid chamber;
• (e) said spool valve member in its first position communicating fluid from said supply fluid chamber to said first piston fluid chamber and from said second piston fluid chamber to said second return fluid chamber;
• (f) said spool valve member in its second position communicating fluid from said supply fluid chamber to said second piston fluid chamber and from said first piston fluid chamber to said first return fluid chamber;
• (g) first and second valve actuating subassemblies associated with said piston rod first and second ends respectively, each said valve actuating subassembly including a respective valve actuating spring and being adapted to selectively engage a respective spool valve member end for shifting said spool valve member between its first and second positions;
• (h) said cylinder, piston subassembly and spool valve subassembly being generally coaxial;
• (i) said fluid chambers being generally annular and generally coaxial with said cylinder, said piston subassembly and said spool valve subassembly;
• (j) a first fluid interconnect line fluidically interconnecting said cylinder second section and said piston first side with said spool valve member in its first position;
• (k) a second fluid interconnect line fluidically interconnecting said cylinder second section and said piston second side with said spool valve member in its second position;
• (l) a third fluid interconnect line fluidically interconnecting said second piston fluid chamber and said equilibrium chamber;
• (m) a fluid inlet port fluidically communicating with said supply fluid chamber;
• (n) a first fluid outlet port fluidically communicating with said first return fluid chamber;
• (o) a second outlet port fluidically communicating with said return fluid chamber;
• (p) said fluid interconnect lines being located exteriorally of said cylinder;
• and
• (q) said inlet and outlet ports being adapted for connection to a fluid pump whereby a fluidically closed system is provided.