Patent GB-709893-A (GB)
Title: Improvements in or relating to fluid-pressure operated drive mechanisms for percussion tools
IPC: E21B4/14
Filed: 1952-10-28
Abstract: 709,893. Engine valve gear. LICENCIA TALALMANYOKAT ERTEKESITO VALLALAT. Oct. 28, 1952 [Nov. 3, 1951; Feb. 19,1952; Oct. 16, 1952], No. 27098/52. Class 122(2) [Also in Groups XXI, XXIII and XXIX]  In a fluid pressure operated drive mechanism for percussion tools provided with a high pressure chamber 59 adapted to be connected to a source of fluid under pressure and with a low pressure chamber 64 adapted to be connected to the atmosphere and comprising a guide means 31 situated between the high and low pressure chambers, and a slide member 32 formed as a control means slidable between two extreme positions relative to a piston 30, 38, 39 formed as a tool holder situated between the slide member 32 and the guide means 31 and slidable between two extreme position: relative to the latter, twc work chambers 45, 46 enclosed by the guide means and the piston are each connected by ducts 67, 78. 71, 80, 73, 82 in the guide means 31 alter nately to the high and low pressure chambers in accordance with the rela tive positions of the guide means, the piston, and the slide member. The piston and slide member enclose two control members 51, 52 of volumes variable in accordance with the relative positions of the piston and slide member, each control chamber in its position of greatest volume communicating directly with one of the work chambers 45, 46. The piston has shoulders 42, 43, 44 enclosing the work chambers and forming ante-chambers 47, 48 which are in constant communication with the control chambers 51, 52 and communicate alternately with the high and low pressure chambers 59 and 64 respectively in accordance with the relative positions of the piston and guide means. In Fig. 1 the tool holder 54 is in its bottom position; fluid in the control chamber 51 and ante-chamber 47 is flowing in direction of arrows 98 and 99 to exhaust and the fluid in work chamber 45 is also being exhausted in the direction of arrows 97 and 99; pressure fluid in chamber 59 flows in direction of arrow 91 into ante-chamber 48 and control chamber 52, where it causes the slide member. to occupy its bottom position as in Fig. 1, and also into work chamber 46 where it urges the piston upwards in direction of the arrow 96. As the piston moves upwards the change in the relative positions of the ducts first results in equal pressures obtaining in the control chambers 51 and 52 so that the slide member 32 is in a balanced condition, and finally pressure exists in the chamber 51 and is exhausted from the chamber 52, the slide member 32 then moving downwards allowing fluid to flow into work chamber 45 and out of work chamber 46. and the piston is urged downwards until the slide member 32 becomes balanced again and ultimately the piston and the slide member reach the position shown in Fig. 1 when the operation is repeated. In another embodiment the guide means 31 is formed by a hollow rod protruding into the piston and the slide member 32 is formed by a sleeve encircling the piston. In a further embodiment, each control chamber 51, 52 is sub-divided into a control chamber of constant volume and'a control chamber of variable volume, necessitating the provision of additional ducts. In all embodiments the guide means, piston and slide member are formed by cylindrical bodies coaxially arranged in a casing 33. When steam is used as the actuating fluid modifications are embodied so that the steam delivers energy on expansion.