Patent GB-526979-A (GB)
Title: Improvements in or relating to drilling machines
IPC: E21B3/00
Filed: 1939-03-30
Abstract: 526,979. Drilling-machines. HOFFAR, H. S. March 30, 1939, No. 9988. [Class 83 (iii)] In a rotary drilling machine for mining, the drill rod is fed by a piston movable in a fluid pressure cylinder, the piston containing a fluid pressure motor for rotating the drill and the arrangement being such that the piston transmits the axial feed pressure directly to the drill rod without transmitting it through the motor. The machine comprises a cylinder 1 containing a piston consisting of a barrel 2 and end flanges 20, 20a whereof the former carries a cup breather 28. The piston slides on rods 16 which prevent its rotation and carry end stops for limiting the motion of the piston. Pockets 22, Fig.. 3, on the outside-of the barrel 2 receive rotary spacers 4 geared to a central wheel 34 on the rotor 3 so that blades 31 on the rotor may enter recesses 43 in the spacers during rotation. Fluid, preferably air, is admitted to the motor by a flexible pipe 5 and proceeds through a passage 23 in the end plate 20 to an annular space within a stationary sleeve 24 from whence it passes through ports 25 to radial passages 32 in the rotor, which rotates clockwise in Fig. 3. Exhaust takes place through ports 26 in the barrel 2 to the outer space between the flanges 20, 20a and then passes to atmosphere through a flexible pipe 5 leading to the end of the cylinder 1 or merely discharges into the cylinder. The drill rod 9 is carried by a chuck outside the cylinder 1 on a tube 13 which rotates with the rotor 3 and receives axial feed movement direct from the piston 2 when hydraulic fluid or air is admitted to the left-hand end of the cylinder by a pipe 8, Fig. 4. This axial thrust is transmitted to a collar 75 on the tube 13, in the feeding direction, by pins 7, Fig. 2, engaging a journal and thrust bearing 73 attached to the flange 20a of the piston, and in the withdrawing direction by a flanged collar 72 attached to the flange 20a. The pins 7 pass freely through holes in a ring 71 attached to the centre tube 35 of the rotor to transmit rotation to the tube 13. The tube 13 telescopes over a stationary tube 12 attached to the cylinder end 10, packing being provided at 29. In use, the drill may be fed to the work by air pressure, the rate of feed being limited by hydraulic fluid on the other side of the piston passing through a variable throttle valve, by arranging the valves 86, 89, 65 as shown in Fig. 4. Air is supplied by a compressor 85 through valve 86 and pipe 8 to the cylinder 1 to feed the drill, and fluid is displaced from the end 11 of the cylinder to a closed reservoir 6 through the throttle valve 65, air escaping from the reservoir through pipe 67 and valve 89. To return the drill, the valves 86, 89 and 65 are turned to connect the pipe 8 to the exhaust 84 and the compressor to the pipe 80 so that the air will enter the right-hand end of the cylinder 1. To advance the drill by air pressure without impedance by the hydraulic fluid, the valve 65 is turned to disconnect the cylinder 1 from the reservoir 6 and the valve 89 connects the pipe 80 to the exhaust 84 so that the compressor 85 may supply air to the pipe 8. In order to fill out the right-hand end of the cylinder with hydraulic fluid preparatory to a drilling feed the valve 86 is turned to connect the pipe 8 to the exhaust 84 and the compressor to the pipe 67 whereby air will be supplied to the reservoir 6 to deliver the fluid through the valve 65. The reservoir 6 is separate from the cylinder 1 and may be located at a situation remote therefrom.