Patent GB-872547-A (GB)
Title: Rotary cutting device
IPC: B24B5/40
Filed: 1958-03-24
Abstract: 872,547. Internal pipe cutters. JOY MANUFACTURING CO. March 24, 1958 [April 1, 1957], No. 9307/58. Class 83 (4). [Also in Group XXIII] A rotary cutting device for internally cutting through a pipe wall comprises a rotatable hollow body member receivable within said pipe wall and provided with a piston chamber, a piston means movable within said body member and having a piston head in said chamber, said piston chamber having a communication with the interior of the body member for receiving pressure fluid supplied to said interior to effect longitudinal movement of said piston means, a cutter member carried by said piston means and movable longitudinally therewith, said cutter member being disposed within a circumferential opening of the hollow body member for rotation therewith, and means effecting outward sliding movement of said cutter member into cutting engagement with the pipe wall upon longitudinal movement of said piston means. The device comprises a hollow body member 24 having at the top end 34 internal threads for connection to a rotatable drilling string 21. An intermediate portion of member 24 has three longitudinally extending circumferentially spaced openings 26. The member 24 has at the bottom end a cylinder 25 defined by a cylindrical wall 42 into the lower end of which is threaded a shoe 44 having an axial throughbore 46 at the upper end of which is a conical valve seat 47. A piston 28 movable longitudinally within the body member 24 comprises an elongated hollow piston stem 50 received at its top end in a passageway 53 in the body member 24 and having at its bottom end a piston head 54 located in the cylinder 25, packing 56 being retained in a recess in the piston head by a flange 57. The bore of the stem 50 communicates with a valve chamber 65 in the piston head 54 containing a valve 66 which comprises a hollow skirt 69, provided with longitudinally and circumferentially-spaced ports 70, integral with an axially ported head 67 having a conical outer face to co-operate with the valve seat 47. Above the head 54 the piston has wall sections 60 received in the openings 26 in the body member 24, so that the piston and body member rotate together. Each section 60 has a longitudinal passageway 63 providing restricted communication between the cylinder 25 and the opening 26. The piston is biased downwardly by a coil spring 74. The piston carries cutters 29 disposed within the openings, the cutters being located on the piston between the top face 72 of each wall section 60 and lugs 73 projecting from the stem 50. Each cutter 29 includes a base portion 80 provided on opposite sides with inclined guide ribs 81 which slide in inclined guide grooves 78 provided in the body member 24. The outer face of each base portion 80 has flanges 84, 85 providing reinforcement for cutting segments 86, 86 formed of tungsten carbide particles in a silver matrix and having a bottom outwardly directed cutting lip 88. Upward movement of the cutter is limited by circumferentially spaced pressure fingers 31 secured to the body member 24. Operation.-Initially, the downwardly biased piston 28 is in lowermost position in the body member 24, the cutters 29 being seated on top of the wall sections 60 of the piston and being in retracted position. The bottom face of the piston head is in close proximity to the top face of shoe 44 and the valve 66 is seated on the seat 47 substantially closing the throughbore 46. When drilling fluid is introduced into the pipe string 21, it passes through ports 70 and moves the piston 28 upwardly relative to the body 24. The cutters 29 carried by the piston are thus moved radially outwards, so that the cutting lips contact the internal surface of the casing wall 20 and start to form a cut therein. As soon as a cut is formed in the casing wall, downward pressure applied to the body member 24 through the drilling string 21 positively forces the cutters radially outwards. The drilling fluid is afforded limited circulation through passageways 63 into, behind and around the cutters 29 to wash away cuttings. As cutting of the casing wall continues, the piston head moves upwardly relative to the piston chamber and the cutters are urged radially outwards; at a predetermined point in the upward path of movement of the piston which substantially coincides with or occurs just after penetration of the casing wall, a lip 57a on piston flange 57 engages shoulder 69a on the skirt of the valve member and lifts the valve member from its seat at 47. The resultant drop in pressure is detected at the surface to inform the operator that the cutters have penetrated the casing. Due to downward movement of the body 24 the piston head continues to move upwardly relative to the body 24 until the cutters reach extended position. The base portion 80 of each cutter is now in contact with the bottom face of the pressure finger 31 and is no longer seated on the top face of piston wall section 60. Thus downward pressure applied to the drilling string is transmitted directly to the cutters to cut an opening of desired length in the casing wall.