In rock drilling and rock bolting, one often uses a rock drilling rig where one or more drilling machines are carried by respective movable arms, or booms. The booms are usually flexibly attached to a carrier, such as a vehicle, via one or more joints. Furthermore, the drilling machine is usually flexibly attached to the end of the boom away from the carrier via one or more additional joints.
However, the drilling machine is usually not attached directly to the boom, instead being normally attached to the boom in movable manner by a feed unit consisting of a feeder holder, which carries a feed beam arranged movably relative to the feeder holder, and furthermore the drilling machine is usually displaceable relative to the feed beam to achieve great freedom of adjustment during drilling thanks to the telescopic action, without the carrier having to move around.
Depending on the type of drilling, such as tunneling or ore mining, different types of rock drilling rigs are used. For example, when driving a tunnel, one often uses large machines with a plurality of booms, so as to drill a plurality of holes at the same time, or nearly so, and to reach across a large portion or the entire, usually relatively broad cross sectional surface that the tunnel requires from a single supporting position.
In ore mining, on the other hand, it is often desirable for economic reasons to mine the ore in such a way that only the ore body is mined, thereby reducing as much as possible the amount of excess rock that needs to be handled. This means that, when mining small ore bodies and/or when only a small portion of the ore body contains the desired ore, the mining can occur at very low gallery heights, with corresponding requirements for the rock drilling rig.
Thus, different situations make different demands on the feed unit, and therefore feed units occur in many different designs. Regarding the feed beam, this often consists of a steel beam or U-shaped aluminium beam, where the drilling machine is mounted on a carriage which then runs along the feed beam, for example, carried by round rods (guideways), or mounted by slide bearings. The movement of the drilling machine (carriage) along the feed beam is usually driven for example by a hydraulic motor or hydraulic cylinder, which drives the carriage directly or via for example a wire or chain. Correspondingly, a hydraulic cylinder is also often used to move the feed beam along the feeder holder.
The feed beam can also be designed with telescopic function, e.g., by having two beams running telescoping one in the other, where one of which (the displaceable) being provided with the carriage bearing the drilling machine.
For feed units in general, and particularly feed units designed for drilling in galleries with low height, it is desirable to not only provide the desired function, but also fulfil the current design constraints at the same time, e.g., as regards the size of the rock drilling rig. But it can be difficult to create a feed unit that simultaneously fulfils both functional requirements and design requirements in a desired manner, especially for rock drilling rigs designed for very narrow galleries. Therefore, there is a need for an improved feed unit.