Abstract: A force compensator for a top drive assembly includes a carrier block, a pair of top drive link assemblies, a mandrel, and a shock absorber assembly. The top drive link assemblies being positionable on either side of a power swivel and having a lower end connectable to the power swivel, an upper end connected to the carrier block, and being slidably positionable on a derrick of a drilling rig. The mandrel is slidably disposed through the carrier block and has an upper end connectable to a mover assembly of the drilling rig. The shock absorber assembly is interposed between the carrier block and a lower end of the mandrel in such a way that the shock absorber assembly is movable between an expanded condition and a compressed condition.

Abstract: A method for optimizing rock drilling, wherein the drilling is adjusted by means of one or more adjustable parameters such as the feed rate and the rotation rate. In the method, a set value (H.sub.s) of each adjustable parameter is deviated in accordance with a sinusoidal curve while integrating a change caused by the deviation in the penetration rate (x) and adding it to the set value (H.sub.s) so that the set value (H.sub.s) shifts closer to an optimum penetration rate (x.sub.opt).

Abstract: To rotate a pipe (17) to be urged into the ground, a rotary disk (20) clamped at said pipe (17) is pivotable on a table (19) which carries two groups of driving cylinders (40, 41). While the first group is operative to carry out the working stroke in order to turn the rotary disk (20) the return stroke is performed by the second group thus ensuring a continuous rotation of the rotary disk (20) or a standstill in one sense of rotation.

Abstract: A drive mechanism for a drill provides both rotational drive and axial feed for a drill of substantial diameter such as those used to drill holes for roof bolts in mine shafts. A plurality of sprockets carry two chains of drive links which interlock around the drill shaft with each drive link having depressions which mate with scroll-like projections on the drill shaft. For axial feed, the sprockets are driven from worm drives in separate housings on each side of the chains, the worm drives being driven from gears in a gearbox which are connected through a differential gearset to a hydraulic motor. A second hydraulic motor also drives through the differential gearset to rotate the drill shaft and the entire drive chain assembly. A large diameter face seal serves as the partition between the chain drive assembly and the gearbox.