GB1464018A - Rotary ground drilling rigs - Google Patents

Abstract

1464018 Boring earth &c LIND PILING Ltd 3 July 1975 [4 July 1974] 29717/74 Heading E1F A driving unit 8 for a rotary ground drilling rig, e.g. using a ground auger (not shown), includes a frame 19 which carries a rotary table 18 having a driving ring gear 17 and a number, eg four, of piston type hydraulic motors 14, 15 each of which drives a pinion 16 meshing with the ring gear 17 and some at least of which have remotely controllable devices for reducing the swept volume of the motors to zero. As described the driving unit has three motors 14 with remotely controllable devices for reducing their swept volume to zero and a single motor 15 whose swept volume can be reduced to a fraction of its maximum value. The motors 14, 15 are supplied with hydraulic fluid from a hydraulic power output, e.g. power pack 12, through a supply circuit including lines 23 connected to the motors 14, the lines 23 containing cut-off valves 21 and lines 24 connected to motor 15, the lines 24 being connected directly to the supply 12. In use, when drilling, all the motors 14, 15 are used to provide maximum torque and a low speed of rotation of the auger. To remove spoil from the auger after it has been raised from the hole, the swept volume of the motors 14 are reduced to zero and cut-off valves 21 are closed so that the entire output of the hydraulic supply passes through motor 15, thus rotating the auger at high speed (but at low torque). The speed of motor 15 can be further increased by reducing its swept volume. By closing valves 21 and reducing the swept volume of motors 14 to zero, the drag exerted by motors 14 is minimised, thus permitting the motor 15 to rapidly accelerate the auger to its maximum speed of rotation. The auger (not shown) is mounted on a kelly bar 3 which is driven by keys 20 in the rotary table 18 and which is suspended from a cable 4 passing over jib 2 on a mobile crane 1. The driving unit 8 is mounted on arm 10 pivoted to the crane at 9.