Valve assembly with low resistance pilot shifting

A valve arrangement for placing a supply of motive fluid in alternating communication with first and second motive fluid chambers, the valve arrangement comprising:

• a power valve including a supply chamber, a pilot chamber, and a shiftable member separating the supply chamber from the pilot chamber, the supply chamber adapted to constantly communicate with the supply of motive fluid, the shiftable member adapted to shift into a first position in response to the pilot chamber being pressurized with motive fluid and into a second position in response to the pilot chamber being at atmospheric pressure, the shiftable member placing the supply chamber in communication with the first motive fluid chamber in response to the shiftable member being in the first position, and placing the supply chamber in communication with the second motive fluid chamber in response to the shiftable member being in the second position;
• and
• a pilot valve actuable between an on condition in which the pilot valve places the pilot chamber in communication with the supply of motive fluid, and an off condition in which the pilot valve places the pilot chamber in communication with the atmosphere;
• wherein the pilot valve includes a passageway, a pilot actuator extending through the passageway and slidable within the passageway between first and second positions, and a sealing member carried by the pilot actuator and providing an impermeable seal between the pilot actuator and the passageway;
• wherein movement of the pilot actuator into the first position places the pilot valve into the on condition and movement of the pilot actuator into the second position places the pilot valve into the off condition;
• and
• wherein sliding movement of the pilot actuator within the passageway between the first and second positions is free from any resistance other than the seal between the pilot actuator and the passageway.