Rotation unit, rock drilling unit and method for rock drilling

A rock drilling unit comprising:

• a rotation unit being without a percussion device, the rotation unit including a main shaft, connection members for attaching drilling equipment to the main shaft, at least one rotating motor for generating rotation and torque, and transmission members for transmitting torque from the rotating motor to the main shaft, wherein the main shaft includes a tubular outer shaft and an inner shaft arranged inside the outer shaft, an outer surface of the outer shaft being provided with axial support surfaces for transmitting axial forces, and the inner shaft being provided with first transmission members at a rear end for receiving torque from the rotating motor, a front end of the inner shaft including second transmission members for transmitting the torque to the drilling equipment;
• a feed beam movably supporting the rotation unit in a drilling direction and a return direction;
• a feed device for generating feed forces;
• and
• wherein the drilling equipment includes at least one drilling tube, a first end of the drilling equipment being connected to the rotation unit for transmitting feed forces and torque to the drilling equipment, wherein a free end of the drilling equipment includes a drill bit for breaking rock.

A method for drilling rock, comprising the steps of:

• drilling rock with a rock drilling unit, the rock drilling unit including a feed beam, a feed device, drilling equipment and at least one rotation unit, the rotation unit being without a percussion device and including a main shaft, connection members for attaching the drilling equipment to the main shaft, at least one rotating motor for generating rotation and torque, and transmission members for transmitting torque from the rotating motor to the main shaft, wherein the main shaft includes a tubular outer shaft and an inner shaft arranged inside the outer shaft, an outer surface of the outer shaft being provided with axial support surfaces for transmitting axial forces, and the inner shaft being provided with first transmission members at a rear end for receiving torque from the rotating motor, a front end of the inner shaft including second transmission members for transmitting the torque to the drilling equipment;
• rotating the main shaft of the rotation unit around its longitudinal axis and transmitting torque to the drilling equipment connected to the main shaft, the outermost end of which drilling equipment including a drill bit for breaking rock;
• feeding the rotation unit axially by the feed device supported by the feed beam, in a drilling direction and a return direction;
• transmitting torque purely through the inner shaft of the main shaft;
• and
• transmitting axial forces purely through the outer shaft of the main shaft.