Patent GB-1460404-A (GB)
Title: Percussive device for driving holes in soil
IPC: E21B4/14
Filed: 1975-02-28
Abstract: 1460404 Boring earth &c INST GOR DELA SIBIR OTDEL-AKAD NAUK SSSR 28 Feb 1975 8401/75 Heading E1F In a self propelled pneumatic percussive burrowing device of the type including a housing 1 with a pointed front end and a reciprocating hammer piston 2, the hammer piston 2 can be rotated and has its centre of gravity offset from the longitudinal axis 0-0 of the housing, the point 10 at which the hammer piston 2 strikes the housing 1 being in axial alignment with the centre of gravity of the hammer piston 2. The centre of gravity of the hammer piston 2 is offset by providing an eccentric groove e (Fig. 1) in the piston 2 or by providing an eccentric mass 13 (Fig. 4) of greater density than the remainder of the piston 2. The device can be used for driving straight or curved holes. With the hammer piston 2 continuously rotating the device drives a straight hole and with the piston not rotating the device drives a curved hole, the hole curving away from the axis 0-0 on the side opposite to the impact point 10. The hammer piston 2 is reciprocated by compressed air fed through line 3 to a tube 5 which engages a cavity b in the piston 2, the piston 2 being provided with passages d which alternately connect the front working chamber a to the compressed air in cavity b and to exhaust. In a first embodiment (Fig. 1) the tube 5 can be rotated by motor 6, this rotation being transmitted to the piston 2 by splines on the tube 5.  In a second embodiment (Fig. 4) the tube is fixed and the piston 2a is rotated by a drive shaft 11 having splines 9 which engage a bush 12 fixed in the piston 2a. The device may be reversed by opening a passage in the tube. In a third embodiment (Fig. 7) the tube 5a has a passage g and a rotatable shutter 16 is provided between the piston 2b and tube 5a, the shutter 16 being rotated by friction. When the piston 2b is rotated anti-clockwise (Fig. 7) the shutter closes the passage g as shown and the device moves forwardly and when the piston 2b is rotated clockwise the passage g is opened and the device moves rearwardly. In a fourth embodiment (Fig. 8) the shutter 16a is movable axially to open and close the opening h in the tube 5b, the shutter being moved axially by projections 18 on the shutter engaging a thread 19 on the drive shaft 11a. In a fifth embodiment (Fig. 10) the piston 2a is rotated by a pneumatic motor 7 and the tube 5 is provided with the reversing arrangement shown in Fig. 7. The motor 7 is controlled by a rotary valve 21 which when rotated causes the motor 7 to rotate clockwise, anticlockwise and stop in sequence. The valve 21 is operated remotely from the surface by switching the air supply on and off using control 31. Each time the air supply is switched a spring loaded piston 23 is reciprocated. The piston 23 has a peripheral cam groove s engaged by pin 24 which causes the piston 23 to be rotated each time it is reciprocated, the rotary motion being transmitted to the valve 21 by splined shaft 22. The rotary position of the piston can also be indicated by a disc 29 fixed to the drive shaft 11, the disc 29 having a notch t which sends a pulse of compressed air through passage k to detector 26 each time the disc 29 is rotated.