Arrangement for controlling the feed mechanism of a rock drill

An arrangement in the feed mechanism of a rock drill, said arrangement comprising a feed beam, a feed cylinder including a piston rod which is arranged to be stationary in the longitudinal direction of the feed beam and a cylinder sleeve which is mobile in the longitudinal direction of the feed beam, a feed mechanism arranged to be driven by the feed cylinder for providing feed and return motion of the rock drill, a control mechanism for controlling the feed mechanism of the rock drill, an indicator connected so that it moves in the same direction as the rock drill for indicating the position of the rock drill, and at least one sensing element which detects the indicator when the indicator reaches a predetermined position with respect to the sensing element and supplies to the control mechanism a control signal necessary for controlling the motions of the rock drill, wherein said at least one sensing element is mounted on the feed beam of the rock drill along the travel of the cylinder sleeve in such a manner that a sensing area of the sensing element extends inside the feed beam, and further wherein said indicator is secured to the cylinder sleeve inside the feed beam so as to move together with said cylinder sleeve, so that when the rock drill reaches a predetermined position with respect to the feed beam, the indicator secured to the cylinder sleeve causes the corresponding sensing element to supply a control signal to the control mechanism.