GB957204A - Improvements in percussion tools - Google Patents

Abstract

957,204. Percussive tools. ATLAS COPCO A.B. Jan. 3, 1961 [Jan. 5, 1960], No. 224/61. Heading B4C. In a tool comprising a housing 1, and a hammer piston 7 reciprocable in the housing under the action of pressure fluid, a member such as a cap 18 carrying handles 19 is connected to the rest of the tool by vibration isolating pneumatic means. Depression of a trigger 54 reduces pressure in a chamber 57 so that air from a hose 30 passing the valve 42 is admitted to passages 33, 35. Air from the passage 35 passing through a pressure reducing valve 37 and a chamber 40 enters a space 9 to raise the piston. Air from the space 8 above the piston passes through a passage 63 to move a distribution valve 27 downwardly to admit air from the passage 33 to the space 8 to drive the piston downwardly on to the anvil block 11 which strikes the steel 12. The steel is held by a retainer (Fig. 2, not shown). When the piston opens a passage 66 the valve 27 is shifted upwardly to shut-off the air supply to the space 8 and opens a passage 34 to vent it to atmosphere. The cap carries pistons 23 running in bores 24 of the housing, the bores below the pistons 23 being connected to larger chambers 72 which are connected to each other. The bores above the pistons 23 are vented through passages 80. As soon as the tool is connected to an air supply, air passes through a hose 76 and restriction 78 to a chamber 72. A low pressure is built up in the bores and chambers since air may leak out through adjustable openings 79 when these are not blocked by the pistons 23. The openings 79 are larger than the restriction 78. The pressure within the bores and chambers does not vary greatly since the volume swept by the pistons due to movement of the cap is small compared with the total volume, little air is admitted through the restriction during periods the openings 79 are blocked, and little air escapes when the openings are clear. The hammer piston may be reciprocated by steam or hydraulically, and the pistons 23 may be replaced by a single piston so that the handles may be rotated relative to the housing. In the modification shown in Fig. 5, the cap has guides (not shown) sliding in the housing and the rods 24 of the pistons 23 have rubber tops 84<SP>1</SP> which engage the interior of the cap. If the tool is lifted from the work with the trigger 54 depressed, openings 92 in a tube 90 sliding in a bore 91 are closed to operate the distribution valve to stop the tool.