GB1304166A - - Google Patents

Abstract

1304166 Percussive tools AMSTED INDUSTRIES Inc 12 Feb 1971 4564/71 Heading B4C A percussive tool comprises a tool bit 15 movable between limits in a housing 11, a hammer 25, a ram 45 including a roller 53 for engaging the lower surface of an arm 26 secured to the hammer and rollers 52, 54 for engaging cam surfaces 30 on the housing, and a spring 35 against which the hammer is pushed by the ram and which, when the roller 53 is removed from engagement with the lower surface of the arm by the action of cam surfaces 30, imparts energy to the hammer to drive the latter on an impact stroke. The tool is so arranged that a slight movement of the tool bit into the housing is initially required in order that the hammer may be moved to a position such that the ram 45 can pivot under bias of spring 65 to the position of Fig. 1. Such movement of the ram will also effect via linkage 75 movement of spool valve 60 to one position so as to cause extension of the ram. The linkage 75 will also cause, when the ram is pivoted to the hammer release position, movement of the spool valve to its other position so as to cause retraction of the ram. The spring 35 may comprise a coil spring or a pair of pneumatic springs, as shown. A buffer 71 is engaged by a projection 70 on the hammer before the toolbitreaches its lowerlimit position. A buffer 73, against which the rollers 52-54 may be fired, is also provided.