Patent GB-722415-A (GB)
Title: Improved drive means for rotary cutting tools
IPC: B24B27/06
Filed: 1951-06-18
Abstract: 722,415. Grinding; sawing. BALLINGER, L. J. H. June 10, 1952 [June 18, 1951]. No. 14408/51.. Classes 60 and 145. Drive means for rotary cutting tools, such as circumferentially cutting abrasive discs or circular saws comprise a hollow drive spindle mounted for rotation and in end-to-end driving connection with a sleeve on which the cutting tool is mounted, a coupling between the spindle and the sleeve for permitting transverse movement of the sleeve relative to the spindle, a shaft situated concentrically in the spindle and provided with an eccentric extension journally supporting the sleeve, and means for driving the spindle and shaft at different speeds, the speed difference between the spindle and the shaft being relatively small. A cutting disc 13, Fig. 1, is secured by plate 14 and nut 15 to a flanged sleeve 16 driven through an Oldham coupling 18, 19, 20 by a hollow spindle 10 rotated by a belt 12; the spindle 10 is journaled in an arm 27 adapted to move the cutting head in the conventional fe.ed and return motion relative to a work piece. The sleeve 16 rotates on an eccentric portion 25 of a shaft 24 within the hollow spindle 10; the shaft 24 is rotated by a belt 22. The spindle 10 and shaft 24 rotate in the same direction but at slightly different speeds, so that the centres of successive cutting areas on the circumference of the disc are one to two degrees apart. This is stated to ensure concentric wear of the disc and a resting and complete cooling of that part of the disc circumference which has contacted the work piece at any particular interval. The planetary motion of the disc provides for the curved path cut by the disc circumference in the work-piece to be of a less acute curvature than the radius of the disc and ensures that a coolant is close to the centre of the cutting area. In a modification, Fig. 3, pulley 34 driven by belt 32 is formed with gear wheels 35, 36 driving respectively gear wheel 37 on hollow spindle 10 and gear wheel 38 on shaft 24. A circular saw 40 is secured by plate 14, nut 15 and pin 39 to a flanged sleeve 16. The sleeve 16 is mounted on an eccentric bush 41 secured on the eccentric portion 25 of the shaft 24, serrations 42 on one end face of the bush engaging corresponding serrations on a flange 43 splined for axial movement on an extension 44 of the eccentric 25; a nut 45 tightens the flange 43 against the serrated end of the bush 41, the other end of the bush abutting the extension 26 of the shaft 24. The bush 41 and eccentric 25 have the same eccentricity, so that the total eccentricity imparted to the sleeve 16 can be varied from zero to a maximum. For adjustment, after the nut 25 is slacked and the serrations disengaged, the shaft 24 is held at a square extension 46 by means of a spanner and the bush rotated by a tommy bar engaging radial holes 47 of the bush. To locate the position of zero eccentricity, axial holes 48, 49 are provided in the bush 41 and flange 43 in which a pin may be inserted. The bush 41 is set for concentric motion when the saw is to be sharpened. The cutting head assembly shown in Fig. 3 may be embodied in a cut-off machine comprising a bed 50, Fig. 6, having a pillar 51 to which the arm 27 is pivotally attached, an electric motor 52 being mounted on the remote end of the arm 27 for actuating the belt drive 32. The work piece 54 is held by a vice 53.