A supporting arrangement for a feed device for a drilling machine of a rock drilling unit (2) comprising a feed device (3) for a drilling machine (4), a cradle (5) supporting the feed device longitudinally displaceably and a supporting device (10) which is extendable in parallel with the feed device for supporting the feed device against a tunnel wall. The supporting device is supported by the cradle so that it remains stationary with respect to the cradle when the feed device is displaced.
An arrangement in a rock drilling apparatus comprising supports (5) directed toward the rear part of the feed, the supports being moveable by means of support cylinders (6) to support the feed during the drilling operation. The arrangement comprises a pressure detector (9), which is arranged to detect the pressure of the pressure fluid in the support cylinders (6) and to make the control unit supply more pressure fluid to the support cylinders (6) when the pressure drops below a pre-set threshold value.
