Patent GB-1004844-A (GB)
Title: Sharpening means for chain saws
Inventor: OEHRLI JOHN WESLEY
IPC: B23D63/16
Filed: 1962-07-12
Abstract: 1,004,844. Sawing. McCULLOCH CORPORATION. July 12, 1962, No. 26907/62. Heading B5L. [Also in Division B3] A chain saw has an engine and frame portion 11, a bar 12, a saw chain 13 driven by the engine and travelling on the bar, and a sharpening mechanism 14 secured on the engine frame. The bar 12 is adjustably secured to the portion 11 by bolts 16 extending through slot 17 and is of the plain type having tongues 18 extending outwardly of the central portion forming longitudinal peripheral members straddled by the chain. A rotatable wheel 19 is bearing mounted on the nose end of the bar in alignment with the tongues 18 and on which the chain rides. The chain is driven by a sprocket assembly secured to a clutch drum 23. The sprocket assembly is bearing mounted on the engine shaft 24, and the clutch drum is driven by the shaft through a centrifugal clutch. The sprocket assembly has two sprocket wheels 25 with an interposed disc 29, the three parts being secured together by pins 30 and the assembly being secured to the inner wall of the clutch drum. The outer circumferential surfaces of the sprocket teeth 34 are concident with the circumferential surface of the disc 29. The saw chain has side links 40 and centre links 41 connected by pintles 42. The side links 40 have inwardly extending sprocket-engaging projections 43. On the inner surfaces of the side links 40, in horizontal alignment with the inner edges of the centre links 41, are extensions 45 disposed longitudinally outwardly of the pintles and of the projections 43. Each extension is limited longitudinally to provide clearance with the extension on the next link and contacts the outer circumferential surface of the first sprocket tooth as the chain moves from the lower tongue 18 to engage the sprocket, contact occurring before the extension reaches the vertical diameter through the sprocket assembly. The contact limits the vertical movement of the side and centre links on the sprockets, so providing constant positioning of the chain on the sprocket and proper positioning of the cutting elements for sharpening. To assist proper positioning of the chain radially on the sprocket assembly, each centre link 41 has extensions 45<SP>1</SP> for contacting the disc 29. Additionally, each centre link has a longitudinally arced, transverse inwardly facing surface 48 having the same radius as the disc 29. The projections 43 are not in driving contact with the sprocket teeth until just prior to the position where the chain leaves the sprocket assembly. Centre and side cutting elements 50, 51 extend vertically outwardly from selected centre and side links respectively. In cutting sequence, a pair of allochiral left and right-hand trough cutting centre cutters are normally followed by a pair of shorter allochiral left and right-hand side cutters on opposite sides of the chain to complete a cutting group of four cutting elements. Each centre cutter has a flat-sided shank 54 extending outwardly from the centre link and outwardly of the central plane a-a of the chain. The respective left and right-hand shanks are offset transversely outwardly and have at their upper ends transverse cutting edges 55 formed on a forward facing bevelled surface. The outer surfaces 56 of the centre cutting elements are curved and lie on arcs 57 of equal radii, the centres of which are on a line perpendicular to the plane a-a and midway between the axes of each pair of pintles 42 so that the vertical distance of the outer surfaces 56 and the cutting edges from the plane a-a is determined by the longitudinal distance from the line and the axes of the pintles. Forwardly of each centre cutter on its selected centre link and spaced therefrom is a depth gauge 60. The outer curved surfaces 61 of the depth gauges are on the same arcs 57 as the outer surfaces of the cutting elements, the depth gauges being shorter than the cutters because they are farther longitudinally outwardly from the centre point between the pintles 42. The side cutting elements, as they follow the centre cutting elements, extend sufficiently inwardly toward the vertical plane of the chain to overlap the cut made by the preceding centre cutters. The side cutters have curved outer surfaces 62 which lie on arcs 57 equivalent to those of the centre cutters, but the side cutters are shorter than the centre cutters because they are spaced a longer horizontal distance away from the centre point between the pintles on the side links. Spaced forwardly of the side cutters on the side links are depth gauges 66 having their outer surfaces 67 on the equivalent arcs 57. As the depth gauges 66 are spaced the greatest distance from the centre line between the corresponding pintles 42 relative to the cutting elements and the other depth gauges, they extend the shortest distance vertically outwardly from the plane a-a. If the radius of the sprocket assembly is smaller than that of the nose wheel 19 or nose of the bar, a clearance angle on the top of the teeth for boring operations is provided by the sharpening.