The invention relates to a method for lubricating the rotation mechanism of a drill shank in a rock drilling machine, the method comprising directing to the rotation mechanism of the drill shank at least part of the flow of the pressure fluid of a hydraulic circuit of a device of the rock drilling machine performing at least one function, for the purpose of lubricating the rotation mechanism of the drill shank.
The invention further relates to an arrangement for lubricating the rotation mechanism of the drill shank of a rock drilling machine, in which arrangement at least part of the flow of the pressure fluid of a hydraulic circuit of a device of the rock drilling machine performing at least one function is arranged to be directed to the rotation mechanism of the drill shank for the purpose of lubricating it.
Rock drilling rigs are used in rock drilling and excavating in underground mines, opencast mines and excavation sites. Known methods used in rock drilling and excavation are cutting, crushing and percussive methods. Percussive methods are most commonly used with hard rock. In the percussive method, the drilling tools, such as drill rods and the drill bit at the end thereof, of one or more rock drilling machines in a rock drilling rig are both rotated around their longitudinal axes and impact toward the rock being drilled. The breaking of the rock occurs mainly due to the impact. The purpose of the rotation is mainly to ensure that the studs or other working parts of the drill bit always impact a new point of rock. For striking, the rock drilling machine may comprise a hydraulic percussion device, the percussion piston of which causes stress pulses to the drill shank and further to the drilling tools of the rock drilling machine, which stress pulses travel in the form of a compression stress wave to the drilling tools at the extreme end of the drill bit and on to the rock, making the rock break. Instead of a hydraulic percussion device, the rock drilling machine may comprise a percussion device, in which means based on electromagnetism, for instance, cause a stress pulse to the drill shank without a mechanically moving percussion piston or other percussion member.
Typically, the lubrication of the rotation mechanism of the drill shank in a rock drilling machine, which can later also be called a drilling machine, is done with pressurized air, in which lubricating oil is added to compressed air. This lubricating air circulates inside the drilling machine, lubricates the necessary points, and is finally led out of the drilling machine. In some cases, the air may be circulated back to the rock drilling rig, and the lubricating oil is separated from the air and disposed of, or taken to be further processed for re-use. The lubricating oil that has circulated in the drilling machine is, thus, not returned to the drilling machine. In some solutions, the rotation mechanism of the drill shank may be lubricated by means of a separate circulation oil lubrication circuit, but the splines of the drill shank are still lubricated using pressurized air lubrication.
One problem with a pressurized air lubrication-based lubrication solution is that all lubricating oil cannot necessarily be recovered, but some of the lubricating oil remains in the air as micronic droplets. In addition, a pressurized air lubrication-based lubrication solution of a drill shank is not suitable for percussion devices where stress pulses are caused at a high frequency, for instance several hundreds or even thousands per second, in which case the pressurized air lubrication capacity is not enough to lubricate and cool the splines of the drill shank, for example, which leads to rapid wear of the splines of the drill shank and the rotation bushing or a corresponding member used in the rotation device.