Abstract: The present invention relates to a rock drilling element for percussive drilling that is designed to reduce the stress usually developed on a thread joint when the shock wave transmits from a slender portion to a thicker part. The rock drilling element has an elongated body comprising a first portion and a second portion. The first portion has a female or male thread intended to be connected to a drill rod or a drill tube. The first portion has an outer diameter approximately equal to the major diameter of said thread. The second portion has a male or female thread intended to be connected to a drill bit or a guide tube. The second portion forms a guide portion for radial guiding in a hole being drilled. The length of the first portion is at least 500 mm, such that the thread joint is moved away from an unfavorable reflection area. Furthermore, the present invention relates to a drill string and a method of transferring impact energy in a drill string.

Abstract: The invention relates to a method for controlling rock drilling, and a rock drilling arrangement At least one feed channel (37) of a feed actuator (3, 33) is pro-vided with a restrictor (46), which causes a pressure drop if the penetration rate increases and, consequently, a flow through the restrictor increases. A pressure difference and an increase in the penetration rate can be detected by sensing the pressure before the restrictor and after the restrictor. When the feed rate increases, a hydraulic system is arranged to decrease a percussion pressure.

Abstract: The invention relates to a method for controlling at least two hydraulic actuators, to a monitoring valve and a rock drilling apparatus. The monitoring valve (10) is connected to the input channel of a first actuator through a sensing channel (9) and controls a load-sense circuit (6?) of a second actuator. The pressure of the load-sense circuit (6?) is set by a force of a spring element (12) and biased by a control element (42) of the monitoring valve with differential pressure sensing.

Abstract: The invention relates to a method for controlling at least two hydraulic actuators, to a monitoring valve and a rock drilling apparatus. The monitoring valve (10) is connected to the input channel of a first actuator through a sensing channel (9) and controls a load-sense circuit (6?) of a second actuator. The pressure of the load-sense circuit (6?) is set by a force of a spring element (12) and biased by a control element (42) of the monitoring valve with differential pressure sensing.