Patent GB-1009401-A (GB)
Title: Improvements in percussive tools
Inventor: ELLIOTT KENNETH MALCOLM
IPC: B25D9/12
Filed: 1960-10-19
Abstract: 1,009,401. Percussive tools. JOHN LYNN & CO. Ltd. Jan. 16, 1962 [Oct. 19, 1960], No. 35859/60. Heading B4C. In a hydraulic percussive tool comprising hammers 102, 103 reciprocable to strike an anvil 106, the hammers are connected to pistons 120, 121 located in cylinders 118, 119 having on corresponding sides of the pistons spaces connected by duct 123 to form a closed chamber filled with liquid so that as one piston is forced in one direction the other piston is forced in the other direction, and hydraulic control means are provided whereby the spaces on the opposite corresponding sides of the pistons are alternately connectable respectively with supply and exhaust ducts for the liquid. The liquid supply is connected to a socket 95 leading by bores 94, 93, 97, 100 to a passage 105, and the liquid exhaust is connected to a socket 95 leading by bdre 92 and bores not shown to a passage 104; but the tool will operate with the supply and exhaust connections interchanged. The Figures show the piston 121 at the middle of its stroke, a valve 179 being positioned so that the chamber 127 surrounding the piston rod 115 is connected to the passage 105 and the supply, and the chamber surrounding the piston rod 114 is connected to the passage 104 and the exhaust. When a control valve 125 is set as shown liquid from an enlargement 156 in the supply bores displaces a ball 150 in duct 149 to pass through ducts 151, 152 and annular ducts 142, 141, 154 to spaces 155 surrounding plungers 98, 99 controlling the bores 92, 93. Liquid from the spaces 155 passes into the bores of the plungers so that the bores 92, 93 are sealed by hydraulic pressure acting on the plungers. When the valve 125 is depressed liquid passes from the bores of the plungers to the spaces 155 and from thence through ducts 154, 141, 140, 139, 145 to duct 146 where a ball 148 is moved to permit the liquid to flow through the enlargement 156 surrounding the plunger 98 to exhaust. Liquid in the enlargement 156 surrounding the plunger 98 is prevented from entering the duct 146 by ball 147. With the plunger 99 raised from its seat the piston 121 is urged to the left to drive the piston 120 so that the hammer 102 strikes the anvil, liquid from the chamber surrounding the piston rod 114 being exhausted through a port 183 of the housing 175 of the valve 179 to the passage 104 and in so doing lifts the plunger 98 from its seat. As the piston 120 reaches the end of its stroke a reduction 196 on the piston rod 114 coacts with a bush 128 to connect grooves 170, 171 through ports 172, 173. Ports 172 in the bushes 128, 129 are connected, and bores in a cap 188, bore 187 in the valve 179, and ports 173 are connected with the passage 104 so that liquid in bore 187 is free to flow to exhaust. The pistons 185, 186 of the valve 179 are so dimensioned that on connection of the grooves 170, 171 the valve moves to the other end of the housing 175 to connect passage 105 with the chamber surrounding piston rod 114 by way of bore 182, whilst the chamber 127 is connected to passage 104 by way of a port 183 to drive the piston 120 to the left so that the piston 121 causes the hammer 103 to strike the anvil. When the piston 121 reaches the end of its stroke the reduction 196 in the piston-rod 115 connects the grooves 170, 171 of the bush 129 so that liquid from the passage 105 passes through the grooves, ports 172, 173, drilling 161, drillings in the cap 188 to the bore 187 of the valve 179 to displace it to the position shown. The closed chamber is provided with means to keep the quantity of liquid constant so that the pistons work in unison. When the pistons of the valve 179 simultaneously close both passages to the chambers surrounding the pistons, air filled flexible bags 199 connected to air chambers 205 prevent shock being transferred to the source of supply. A tool having pistons semi-circular in cross-section, and without the valve 175 is described.