On-off valves for high pressure fluids

An on-off valve operable between an open position and a closed position, the on-off valve comprising:

• a valve body having a valve cavity, an inlet and an outlet, in the open position said inlet communicating with said outlet;
• a bushing mounted with respect to said valve body and dividing said valve cavity into a first chamber and a second chamber, said bushing having a bore;
• a valve poppet slidably mounted within said valve cavity, said valve poppet positioned within said bore and having a first end portion positioned within said first chamber and a second end portion positioned within said second chamber, said second end portion sealably closing said outlet in the closed position, said valve poppet having a passage extending from said first end portion to said second end portion;
• a first bias element urging said valve poppet into said first chamber;
• an actuating pin slidably mounted with respect to said valve body, in the closed position said actuating pin sealing said passage at said first end portion of said valve poppet;
• and
• an actuator mounted with respect to said valve body, said actuator operating said actuating pin between the open position and the closed position.