Patent GB-713052-A (GB)
Title: Improvements in or relating to fluid actuated impact tools
IPC: E21B4/14
Filed: 1952-07-10
Abstract: 713,052. Percussive drills. BASSINGER, R. July 10, 1952 [July 25, 1951], No. 17405/52. Class 124 [Also in Group XXI] The fluid-operated percussive unit of a percussive drill comprises a hammer 13, 13a, 13b, 13c, 73d, 15 and 21 telescopically connected with an anvil 12 to which the bit 35 is secured, the portions 15, 21 of the hammer telescoping within a fluid-supply conduit 16a, 16b, 16c. Slidingly supported in the portion 13c of the hammer is a spring-biased valve unit 54, and on a valve seat formed on the stem 36 of the anvil is a ball 53. The tool is lowered into the bore, with the anvil shoulder 41 resting on the shoulder 40 of the hammer and the valve unit 54 abutting the shoulder 63 of the hammer, so that fluid can flow downwards through the bore of the hammer past the now separated valve elements 54, 53 and through the bore of the anvil stem to the bit. On the bit contacting the bottom of the bore the hammer slides downwards about the anvil stem 36 until it rests on the shoulder 37 of the anvil. This movement is of sufficient magnitude to bring the valve unit 54 to within the vicinity of the ball 53, and the pressure differential set up on the unit 54, due to the constriction therein, results in the unit seating on the ball 53 to cut off the fluid flow through the hammer. A pressure differential is now set up in the hammer, since the cross sectional area thereof adjacent the unit 54 is greater than that of the stem 21, and so the hammer moves upwards about the stem 36 of the anvil. The valve unit 54 remains seated on the ball 53, despite the increasing tension of the spring 58, until it is engaged by shoulder 63 of the hammer and raised from the ball 53. As soon as fluid can flow between the valve unit 54 and ball 53 the unit 54 is withdrawn upwards clear of the ball to ensure an unrestricted passage to the flow of fluid through the hammer which checks the continued upward movement of the hammer, due to its acquired momentum and then urges it downwards to strike the anvil and to permit the recommencement of the cycle. The upper movement of the hammer is in excess of the length of the telescopic joints between the hammer and the anvil so that said anvil and bit are raised clear of the bore bottom towards the end of the upward movement of the hammer. A similar valve unit is arranged in the fluid conduit and at the end of the stem 21, and the dimensions of the tool can be so proportioned that, towards the end of the upward movement, the valve unit 71 and ball 70 engage to shut off flow of fluid from the conduit and to stop, during the initial upward movement of the parts 71, 70, over travel of the hammer and then to urge it downwards against the anvil. The parts 71 and 70 towards the end of the down stroke are separated in a similar manner to the parts 53, 54 as described. The length of the telescoping connection between the conduit and hammer is longer than the distance through which the anvil must telescope to seat ball 53 with element 54, so that the lower valve assembly may operate without operation of the upper valve assembly by merely suspending the conduit sufficiently above the hammer so that the ball 70 will not seat with element 71.