GB768030A - Improvements in reciprocating cutting mechanisms - Google Patents

Abstract

768,030. Hedge cutters. MARPLES & SON, Ltd., R. M. April 19, 1955 [Feb. 3, 1954], No. 3233/54. Classes 6(2) and 6(3). [Also in Group XXIII] A saw for cutting hedges, timber and other natural growths comprises a blade 31 reciprocated relative to a fixed frame 24 carrying a ramp 25 which guides the material to be cut on to and across the blade when longitudinal thrust is applied to the saw ; for the severance of light growths, knife teeth 33 are formed in the blade 31 on the opposite edge from the sawteeth 32 to co-operate with comb fingers 34 formed in the frame 24. Pointed tips 35 are riveted to the fingers 34 and the saw portion may be detachable from the blade 31. The flanks 38 of the knife teeth are sharpened on alternate sides to a keen edge cutting with a slicing action, and the crests of the teeth have small flat lands, the corners of which cut similarly to sawing. The blade 31 may be guided either by transverse guide screws 40 extending through slots 39 or by bearing surfaces supported in the frame and co-operating with the top and bottom edges of the blade. The sharpening chamfer on the teeth tends to spring them out of line so that the groove cut is slightly wider than the blade and gives the effect of set on the teeth. Under certain conditions the teeth may become burred or bent sideways and, to prevent damage to the frame 24, the walls are locally widened in the region of the teeth, in order to give adequate side clearance. Where there is a high proportion of medium-size stems 45 in the material being cut, every third tooth 44 may be reduced in height as shown in Fig. 8 so as to cut a small groove in a medium-size stem before the stem is more deeply grooved or completely severed by adjacent higher teeth. The crests of teeth 46 may be slightly cupped to assist in severing thicker stems 47. Where the saw is driven by a compressed air motor, the oily exhaust air may pass along the bottom portion 49 of the frame to prevent the ingress of grit, to assist positive ejection of sawdust through holes 37 and to lubricate the knife and saw. The saw may alternatively be driven by electric, internal combustion or other means and may be portable or mounted on a tractor or trailer.