Directional control valve for pneumatic cylinder

A directional control valve for a pneumatic cylinder having a cylinder housing, a piston dividing the cylinder housing into two chambers, and a rod connected to the piston, the directional control valve comprising:

• a control valve housing having:
• an ambient pressure chamber communicating with an atmosphere surrounding both the pneumatic cylinder and the directional control valve,
• a first pressure chamber communicating with an air supply,
• a second pressure chamber communicating with one of the chambers of the cylinder housing, and
• a first valve means for selectively allowing communication between the first pressure chamber and the second pressure chamber;
• a second valve means for selectively allowing communication between the second pressure chamber and the ambient pressure chamber;
• and
• a control means cavity defined in the control valve housing and having:
• a first pressure controlling piston movably mounted in the control means cavity, where a pressure receiving chamber is formed between the control valve housing and a first side of the first pressure controlling piston,
• a second pressure controlling piston movably mounted in the control means cavity opposite the first pressure controlling piston, where a pressure controlling chamber is formed between the control valve housing and a first side of the second pressure controlling piston,
• a first spring connected to the first pressure controlling piston and the second pressure controlling piston, and
• a linkage means secured to the first pressure controlling piston for selectively fully opening, partially opening, and closing each of the first valve means and the second valve means corresponding to a movement of the first pressure controlling piston;
• and
• an air supply/removal means having a third valve means for allowing the pressure receiving chamber to communicate selectively with the second pressure chamber, air supply and the atmosphere, and
• a fourth valve means for allowing the pressure controlling chamber to communicate selectively with the air supply, the atmosphere, in which the fourth valve means further communicates with the third valve means.