GB1246388A - Down-hole fluid percussion drill for earth boring - Google Patents

Abstract

1,246,388. Percussion motor. PAN AMERICAN PETROLEUM CORP. 17 Feb., 1969 [21 June, 1968], No. 8561/69. Heading B4C. [Also in Division E1] An earth boring down-hole percussive drill has a housing 10 containing a hammer piston 20 which is actuated to strike a reciprocable anvil 28 by motive fluid controlled by a valve assembly 54, 56, 58. The drill is rotated by a drill pipe through which the motive fluid (drilling mud) is supplied. The anvil, which cannot rotate relative to the housing 10 has a valve seat 78A with an eccentrically formed seat (101), Fig. 7 (not shown), to reduce wear, which co-operates with a valve head 58 slidably mounted above a shoulder 59 on a valve stem 54 terminating in a piston 56. The piston 56 is slidable in a valve guide tube 46 supported from the upper part of the housing to define an annular flow passage 55. An annular member 88 in the hammer piston bore has an aperture 91 (eccentrically bored to reduce wear), a seat 90 co-operating with the upper surface 58A of the valve head, and a seat 82 co-operating with an annulus 86 on the valve guide tube. Drilling fluid from the drill string passes into a cavity 45 below a choke 66 at relatively low pressure, and through ports 52 into the annular passage 55 at high pressure. As the drill is lowered into the bore-hole, the piston 56 is in the position shown in Fig. 6. Drilling fluid from the annular passage 55 enters the anvil cavity 34 through the ports 62 and the valve stem. On reaching the hole bottom, the anvil and valve stem are pushed up until the piston 56 clears the ports 62 whereupon fluid pressure P3 (Fig. 4) drives the piston upwardly into a cushioning cavity 37. As the piston comes to a halt the pressure P3 acts on the seat 82 to move the hammer piston downwards (Fig. 5, not shown), entraining the valve head 58 as it does so. The hammer piston delivers a blow to the anvil but the valve stem continues downwardly under its own momentum so that the valve head closes on the seat 78A, the valve stem shoulder 59 striking a stop 78B (Fig. 1A). The valve head is held against the seat 78A owing to differential surface area with the piston 56 while the hammer piston rises under pressure P3 until the seat 82 abuts the annulus 86 (Fig. 2, not shown), closing off the pressure P3 from the ring valve head. The valve stem is then thrown upwardly (Fig. 3, not shown), the piston 56 enters the cushioning cavity 37 (Fig. 4) and reciprocation continues as described. The lower face of the hammer piston has non-radial flutes (Fig. 14, not shown) to impart a rotary movement as it falls. The drill may be used for boring horizontally or upwardly directed holes.