Patent GB-855500-A (GB)
Title: Improvements in grinding apparatus
IPC: B24B3/42
Filed: 1957-06-05
Abstract: 855,500. Grinding. ALLSOPP, A. E. May 29, 1958 [June 5, 1957], No. 17866/57. Class 60. A grinding machine for the blades of the cutter unit of a lawn mower of the kind in which a rotatable cylindrical multi-blade cutter unit co-operates with a fixed, straightedged shear blade situated underneath the machine comprises guide and support means for attachment to the mower frame to provide a guide path parallel to the axis of rotation of the cutter unit, a grinding head supported for movement along the guide path and including a grindstone or the equivalent stop means for contacting each blade of the cutter unit in turn to locate the blade in a grinding position relative to the grinding head as the head is moved along the guide path and means for adjusting the stone into contact with the cutting edges of the unit. A grinding unit, Figs. 1, 3 and 4, comprises end plates 14, 15 between which extend parallel spaced members 10, 11, 12. The central member 10 is tubular and has mounted thereon the boss 19 of a beam 18. One arm 18a of the beam is adjustable in length and is formed at its free end with spaced flanges 20 between which is pivotally mounted a block 21 containing a shaft carrying a grinding wheel 24 and driven by a portable electric drill motor 25. A lead screw within the tube 10 is operated by a hand wheel 30 and engages a nut within the tube, the nut having a pin engaging a slot in the tube, so that on rotation of the handwheel the nut travels along the tube ; a removable pin 32 passes through a circumferentially extending slot in the boss 19 into a socket in the nut, so that the beam can rock about the tube 10 but is constrained to move along the tube with the nut. The rear arm of the beam is provided, near its free end, with an adjusting screw 28 having a rounded end bearing on the plane underface of the bar 12. The member 11 is of angle section having in its base 11a a series of slots. To re-grind the rotary cutter unit. 38 of a mower, the mower is supported in inverted position in a stand 35, the straight-edged shear blade is unscrewed from the sole plate 36 of the mower, and the grinding unit is secured to the sole plate by screws 37 passing through the slots in the base 11a of the part 11. The grinding head is adjusted about the pivot 39 to give suitable clearance on the blades, a gauge 40 being employed. The grinding head is traversed to and fro along each blade of the cutter unit, the blade being held by hand pressure on one of the other blades up to the edge 34a of a guide finger 34 vertically adjustable on the block 21. The grinding head is permanently or adjustably set at a small angle e.g. 2 degrees to the vertical as viewed in the direction of the arrow in Fig. 4 to ensure that only one side of the wheel contacts the blade. In cases where it is necessary or more convenient to remove the fixed blade and sole plate as a unit, accessories as shown in Figs. 5 and 6 are used for attaching the grinding unit to the mower frame. To re-grind the fixed, straight edged blade, the grinding unit is attached to a work table 45, Figs. 2 and 3, having a substantially vertical slotted face 46 to which the blade 47 may be secured. In a modification, the spindle of a cutter 65, Fig. 7 separated from, the rest of the mower is held in V-blocks 64 carried by slotted uprights 62 mounted on slotted arms 61 carried by a transverse bar 60 secured to the frame of the stand. When a fixed blade is to be ground it is carried by the uprights 62. The device may be used to grind garden shears and hoe blades.