FI41198B

1,028,648. Sawing. A. STIHL. Aug. 4, 1964 [July 30, 1963; Dec. 7, 1963; Feb. 18, 1964], No. 31121/64. Heading B5L. A chain saw comprises a guide rail 12, having groove means 18 extending along its edges, a saw chain 13 extending along the groove means and around the end of the rail, a sprocket wheel 23 over which the chain passes at the said end of the rail and having a central aperture, a disc 24 fixed to the rail and disposed within the aperture, and anti-friction bearing elements 28 between the periphery of the disc and the wall of the aperture for rotatably supporting the sprocket on the rail. The guide rail is adjustably mounted by bolts 14, Fig. 1 (not shown), on the crankcase 11 of an internal combustion engine driving a sprocket for the saw chain. The upper and lower edges of the guide rail are formed with the groove means 18 and the end of the rail is formed with a slit 21 for the disc 24 and sprocket 23. The sprocket is slightly less in thickness than the disc which is of substantially the same thickness as the slit and is secured to the rail by rivets 27. The outer wall of the disc and inner wall of the sprocket are formed with hardened V-shaped or concave grooves for the bearing elements 28 which are in the form of balls, a transverse bore 32 is formed partly in both the disc and sprocket for the insertion of the balls into the grooves. In another embodiment, the saw chain consists of left and right-hand cutter links 121, 122, Fig. 7 (not shown), arranged adjacent side links 120, centre links 115, and connector links 118, 119, the centre links having projections for running in the groove in the guide rail and for engaging recesses between the teeth 131 of the sprocket. The ends of the teeth 131 have pointed sections 140 which engage the centre links in the spaces between the side and cutter links and between the connector links; the sections 140 are chamfered at 141 to facilitate the engagement of the teeth with the saw chain.