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AssigneeSandvik Intellectual Property AB
InventorsTimo Muuttonen, Pekka Salminen
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The invention relates to a method of opening joints of drilling components attached to a rock drill, and to a rock drill which enabling this. According to the idea of the invention, in striking compression stress, which proceeds towards a drill bit (10), is generated in the drilling equipment (5) by striking with a percussion piston. When the drilling components are struck off, the axial bearing included in the drilling machine does not substantially support the drilling equipment, but the compression stress generated by striking is reflected from the drill bit (10) as stress of the opposite sign and generates the desired tensile stress in the drilling equipment. After striking the threaded joints of the drilling components can be opened easier by rotating the rotating device in the opposite direction.
A method of opening joints between drilling components in a rock drill which is fed with respect to a feeding beam (3) during drilling and which comprises a frame (13a, 13b), a percussion device (6) arranged in the frame, the percussion device comprising a percussion piston (14) which moves in the longitudinal direction, a shank (15) which is arranged in the axial extension of the percussion piston, struck by the percussion piston and to which the necessary drilling components, such as drill rods (9a, 9b), a drill bit (10) and the like, are attached to form drilling equipment (5), and a rotating device (7) which by means of a rotating bushing (16) rotates the shank (15), the rock drill further comprising at least one axial piston (18a, 18b), which is positioned rearwardly of the shank and arranged to move in the axial direction by means of the pressure of a pressure medium fed onto its back surface during drilling, the axial piston acting on the shank by supporting it towards the front part of the drilling machine, the method comprising supporting at least part of the drilling equipment (5) against a supporting surface when threaded joints of the drilling components attached to the shank are opened and striking the drilling equipment with the percussion device (6), after which the shank is rotated by the rotating device (7) in a direction opposite to normal drilling to open the desired joints, characterized by reducing the pressure of the pressure medium that pushes the axial piston (18a, 18b) towards the front end of the drilling machine when drilling components are struck off so that the shank and the drilling components in its extension are substantially not supported by the axial piston in the axial direction when the drilling components are struck off, the compression stress caused in the drilling components by the stroke of the percussion piston being reflected at least partially from the front end of the drilling equipment, whereby said return pulse generates tensile stress in the drilling components and their joints.
A method according to any one of the preceding claims, characterized by generating substantially ambient pressure rearwardly of the axial pistons when the drilling components are struck off.
A rock drill which comprises a frame (13a, 13b), a percussion device (6) provided with a percussion piston (4) which moves in the longitudinal direction, a shank (15) which is arranged in the axial extension of the percussion piston, which is arranged to strike the rear end of the shank, and a rotating device (7) which is arranged to rotate the shank by a rotating bushing (16) arranged around the shank and drilling equipment (5) consisting of drilling components attached to the front end of the shank, the drilling machine comprising at least one axial piston (18a, 18b), which is arranged rearwardly of the shank, there being a pressure channel (22a, 22b) which extends rearwardly of the axial piston and allows feeding of a pressure medium rearwardly of the axial piston to move the axial piston in the axial direction, the axial piston being arranged to support the shank in the axial direction during drilling, characterized in that the rock drill comprises means for reducing the pressure of the pressure medium leading to the axial piston when drilling components are struck off by a percussion device so that the shank and the drilling equipment are substantially not supported by the axial piston in the axial direction when drilling components are struck off.
A rock drill according to any one of the preceding claims, characterized in that the rock drill is arranged to be controlled by means of a control system, which comprises means for bypassing the normal power control of the percussion device of the rock drill when the drilling machine is turned into the position for striking drilling components off, and thus the percussion device can strike at the necessary striking power regardless of the feed of the drilling machine when drilling components are struck off.
Dependencies are inferred from the claim text.