This disclosure describes methods and systems for remote control of stroke length and frequency of percussion apparatus, such as a rock hammer drill. At a high level, the hammer drill is allowed to stay at a default low stroke length and high frequency to avoid applying excessive cyclic stress to the housing of the hammer drill and can be controlled to operate at a long stroke length and low frequency when the hammer drill has engaged the target material. The long stroke length and low frequency during operation can be initiated when a sufficient forward feed pressure is provided. While the hammer drill is idling or retracting, the forward fee pressure is not sufficient for the long stroke length operation and thus the drill operates at the default state and at a safe stress level to avoid premature damage.

This disclosure describes methods and systems for remote control of stroke length and frequency of percussion apparatus, such as a rock hammer drill. At a high level, the hammer drill is allowed to stay at a default low stroke length and high frequency to avoid applying excessive cyclic stress to the housing of the hammer drill and can be controlled to operate at a long stroke length and low frequency when the hammer drill has engaged the target material. The long stroke length and low frequency during operation can be initiated when a sufficient forward feed pressure is provided. While the hammer drill is idling or retracting, the forward fee pressure is not sufficient for the long stroke length operation and thus the drill operates at the default state and at a safe stress level to avoid premature damage.

Provided is a hydraulic striking device in which a reverse operation circuit and a forward operation circuit can switch connection states to a high pressure circuit and a low pressure circuit by means of an operation switching valve. Further, the hydraulic striking device is configured to be selectable between a reverse operation mode or a forward operation mode by operating the operation switching valve. A high/low pressure switching portion is provided with a shortening portion for reducing the time required for high/low pressure switching operation in piston front and rear chambers in association with retraction of a valve to be shorter than the time required for high/low pressure switching operation in the piston front and rear chambers in association with advancement of the valve.

Provided is a hydraulic striking device in which a reverse operation circuit and a forward operation circuit can switch connection states to a high pressure circuit and a low pressure circuit by means of an operation switching valve. Further, the hydraulic striking device is configured to be selectable between a reverse operation mode or a forward operation mode by operating the operation switching valve. A high/low pressure switching portion is provided with a shortening portion for reducing the time required for high/low pressure switching operation in piston front and rear chambers in association with retraction of a valve to be shorter than the time required for high/low pressure switching operation in the piston front and rear chambers in association with advancement of the valve.

A hydraulic hammering device is capable of sufficiently transmitting blow energy to bedrock while further strengthening cushioning action and suppressing damage to equipment. The device includes a pushing piston disposed behind a transmission member and having a smaller propulsive force than that of a main body, a damping piston positioned behind the pushing piston to slide reciprocally forwards and backwards and having a greater propulsive force than that of the main body, a direction-restrictor in a high-pressure circuit between pushing and damping chambers, to which hydraulic fluid is supplied for providing the pistons with propulsive forces, and a fluid supply source. The direction-restrictor restricts an outflow from the chambers side to the fluid supply source side while allowing fluid inflow from the fluid supply source side to the chambers and the pushing chamber sides. A throttle in a drain circuit discharges leaked fluid from a sliding contact location to a tank.

A hydraulic hammering device is capable of sufficiently transmitting blow energy to bedrock while further strengthening cushioning action and suppressing damage to equipment. The device includes a pushing piston disposed behind a transmission member and having a smaller propulsive force than that of a main body, a damping piston positioned behind the pushing piston to slide reciprocally forwards and backwards and having a greater propulsive force than that of the main body, a direction-restrictor in a high-pressure circuit between pushing and damping chambers, to which hydraulic fluid is supplied for providing the pistons with propulsive forces, and a fluid supply source. The direction-restrictor restricts an outflow from the chambers side to the fluid supply source side while allowing fluid inflow from the fluid supply source side to the chambers and the pushing chamber sides. A throttle in a drain circuit discharges leaked fluid from a sliding contact location to a tank.

An impact-driven tool includes a cylinder and a piston slidably inserted into the cylinder and has a large-diameter portion. The cylinder includes: a chamber on one end side; a chamber on the other end side; a communication path that allows the chamber on one end side and the chamber on the other end side to communicate with each other; and a valve chamber that is continuous with one end side in the axial direction of the communication path, and a valve body for piston lifting control that is incorporated so as to be movable up and down and is provided in the valve chamber.

An impact-driven tool includes a cylinder and a piston slidably inserted into the cylinder and has a large-diameter portion. The cylinder includes: a chamber on one end side; a chamber on the other end side; a communication path that allows the chamber on one end side and the chamber on the other end side to communicate with each other; and a valve chamber that is continuous with one end side in the axial direction of the communication path, and a valve body for piston lifting control that is incorporated so as to be movable up and down and is provided in the valve chamber.

The present invention relates to a hydraulic percussion device and a construction apparatus having the same, the hydraulic percussion device comprising: a cylinder; a piston; a backward port connecting a front chamber of the cylinder to a hydraulic source; a forward port formed on a rear chamber of the cylinder; a forward/backward valve for controlling the forward and backward movement of the piston; a control line for moving the forward/backward valve to a forward-movement location; a long-stroke port formed between the forward port and the backward port; a short-stroke port formed between the backward port on the cylinder and the long-stroke port; a shift valve disposed between the short-stroke port and the control line; a proximity sensor for detecting a bottom dead point of the piston upon the stroke on an object; and a controller for determining a striking condition on the basis of the detected bottom dead point, and transmitting a control signal to the shift valve.

The rotary-percussive hydraulic perforator includes a body; a shank; a striking piston configured to strike the shank and provided with a braking surface; a braking chamber configured to hydraulically brake the striking piston; a stop piston configured to apply a pushing force on the shank and provided with a bearing surface configured to abut against a stop surface provided on the body, so as to limit the stroke of displacement of the stop piston towards the shank. The rotary-percussive hydraulic perforator is configured such that the bearing surface and the stop surface are axially spaced apart by a predetermined spacing distance simultaneously when (i) the shank bears on the stop piston and is in contact with the striking piston, and (ii) the braking surface is located at an inlet edge of the braking chamber.