A hydraulic hammering device that uses a scheme in which a front chamber is switched into communication with a low-pressure circuit when a piston advances, wherein occurrences of galling to the piston at a sliding contact portion with a front-chamber liner is reduced. The front chamber has the front-chamber liner fitted to an inner surface of a cylinder. A hydraulic chamber space communicating with the front chamber and filled with hydraulic oil is formed as a cushion chamber on the inner peripheral surface of a rear portion of the front-chamber liner. The cushion chamber has a second drain circuit (from first end face grooves to slits to second end face grooves, which is provided separately from a drain circuit that guides the hydraulic fluid passing through a liner bearing of the front-chamber liner to the low-pressure circuit.

Disclosed is a device including an exhaust valve, that operates on a pressurised working fluid. The device includes a working chamber, defined at least in part by a side wall, which working chamber can hold a workload to or toward a first end thereof, the working chamber to receive the working fluid to act on a rear surface of the workload to propel the workload to or towards a second end, opposite the first, of the working chamber. The device also includes a return chamber to receive fluid under pressure from a front surface of the workload, the pressure developed at least in part by the movement of the workload towards the second end. Present also is an exhaust valve fluidly connected to the return chamber, the exhaust valve normally biased closed preventing working fluid from exiting the working chamber, but on receipt of, and action by, the fluid under pressure from the return chamber, will open to allow the working fluid to exhaust the working chamber to a lower pressure location, the working fluid exhausting via the side wall of the working chamber through to the exhaust valve. Provided then is a device that will remove or reduce pressure building on the rear surface of the workload when moved from the second end to the first end.

Disclosed is a device including an exhaust valve, that operates on a pressurised working fluid. The device includes a working chamber, defined at least in part by a side wall, which working chamber can hold a workload to or toward a first end thereof, the working chamber to receive the working fluid to act on a rear surface of the workload to propel the workload to or towards a second end, opposite the first, of the working chamber. The device also includes a return chamber to receive fluid under pressure from a front surface of the workload, the pressure developed at least in part by the movement of the workload towards the second end. Present also is an exhaust valve fluidly connected to the return chamber, the exhaust valve normally biased closed preventing working fluid from exiting the working chamber, but on receipt of, and action by, the fluid under pressure from the return chamber, will open to allow the working fluid to exhaust the working chamber to a lower pressure location, the working fluid exhausting via the side wall of the working chamber through to the exhaust valve. Provided then is a device that will remove or reduce pressure building on the rear surface of the workload when moved from the second end to the first end.

A hydraulic system, rock drilling rig, and method for limiting output performance of a hydraulic drilling actuator temporarily under execution of a safety function feature of a hydraulic system is provided. The output performance is limited by limiting produced hydraulic fluid flow in a hydraulic circuit of the hydraulic drilling actuator, whereby a restricted magnitude of the fluid flow is produced at a hydraulic pump. This way a restricted operation mode is enabled and is controlled by a control unit.

A hydraulic system, rock drilling rig, and method for limiting output performance of a hydraulic drilling actuator temporarily under execution of a safety function feature of a hydraulic system is provided. The output performance is limited by limiting produced hydraulic fluid flow in a hydraulic circuit of the hydraulic drilling actuator, whereby a restricted magnitude of the fluid flow is produced at a hydraulic pump. This way a restricted operation mode is enabled and is controlled by a control unit.

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.

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.