a solenoid valve in a manner previously explained in such case conduit 617 would act as the return path for hydraulic fluid exiting the cylinder when the conventional solenoid valve reversed the fluid flow from that shown in fig6 by pressurizing conduit 617 the hydraulic cylinder 613 would be in the retract mode with a conventional hydraulic cylinder not provided with limit valves as is cylinder 613 it is very undesirable for the piston with the hydraulic cylinder to remain forcefully pressed at one end or the other of the cylinder under the full pressure of the hydraulic system for a sustained length of time as noted in the foregoing description of fig1 a through fig5 it is usually desirable to prevent such sustained bottoming out of the hydraulic cylinder piston by providing limit switches or other means to cause reversal of pressure on the cylinder piston when it reaches the end of it 39 s travel with the hydraulic cylinder 613 this problem is dealt with in a different manner by providing limit valves rather than limit switches piston 619 is formed with a valve seat 621 and a valve seat 623 a chamber 625 connecting valve seats 621 and 623 contains a ball 627 which tends to seat against the valve seat 623 when conduit 615 is pressurized and which tends to seat against valve seat 621 when conduit 617 is pressurized accordingly when piston 619 is not at an extreme position the opening through valve seats 621 and 623 is effectively closed by ball 627 being seated in one of the two seats and piston 619 operates as if the limit valve represented by ball 627 and valve.