Trigger valves for pressurized fluid operated devices

An actuation trigger for a device, comprising:

• 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 openable under controlled action to allow the charge into the working chamber;
• and
• a trigger valve to selectively supply the high pressure working fluid from the high pressure source to the dose chamber and to control opening and closing of the dose valve, whether directly or indirectly,
• wherein, when the dose valve is open from the dose chamber to the working chamber, there is no supply from the high pressure source to the dose chamber via the trigger valve.

A device, comprising:

• 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 the high pressure working fluid directly or indirectly from the high pressure source;
• and
• a trigger valve to selectively supply the high pressure working fluid to the trigger chamber, or to release the 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, the hammer 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,
• wherein 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.

A method of actuating a device, comprising:

• charging a dose chamber with a charge of high pressure working fluid;
• charging a driven chamber on a first side of a hammer with the high pressure working fluid;
• charging a trigger chamber on a second side of the hammer with the high pressure working fluid, the first side and second side separated by a piston operatively connected to the hammer such that the hammer is held in a force imbalance in a first position;
• releasing the high pressure working fluid from the trigger chamber to drive the hammer to or towards a second position;
• and
• actuating a dose valve by the hammer impacting thereon when in or towards the second position to unseat the dose valve from a sealing position, wherein the dose valve seals the dose chamber from a working chamber to an unsealed position such that the charge enters the working chamber to do work therein.