Trigger valves for pressurized fluid operated devices

Abstract

An actuation trigger for a device, comprising or including, A dose chamber to hold a charge of high pressure working fluid, received from a high pressure source, A dose valve, biased closed to seal the dose chamber off from a working chamber, and hold the charge in the dose chamber, A hammer operated by a piston with a driven chamber on a first side of the piston, and a trigger chamber on a second side of the piston, sealed from the first side, the driven chamber receiving high pressure working fluid directly or indirectly from the high pressure source, A trigger valve to selectively supply high pressure working fluid to the trigger chamber, or to release high pressure working fluid from the trigger chamber, Such that when the hammer has high pressure working fluid in both the driven chamber and the trigger chamber it is held by a force imbalance in a first position, and when the high pressure working fluid is released from the trigger chamber, the hammer is driven to, or towards a second position towards the trigger chamber, The hammer, when driven to, or towards the second position strikes the dose valve, unseating the dose valve to unseal the dose chamber and the working chamber thus allowing the charge to enter the working chamber to do work therein.