GB1195869A - Improvements in Machines for Sharpening the Blades of Lawn Mowers. - Google Patents

Abstract

1,195,869. Sharpening lawn mower blades. J. W. HARTLEY. 14 Oct., 1968 [14 Oct., 1967], No. 46952/67. Heading B3D. A machine for grinding the blades of lawn mowers of the type having a cylindrical cutter drum with a plurality of non-radial blades comprises :- (i) a main frame for supporting a traversing rotary grinding wheel; (ii) a sub-frame for supporting the cutting cylinder carrying the cutting blades; (iii) means for adjusting the position of the sub-frame vertically and transversely of the main frame; (iv) means for rotating the cylinder for trueing up the blades ; and (v) means for rotating the cylinder by hand during backing-off so that the grinding wheel traverses the whole length of each blade in turn to apply a bevel or taper on the trailing edge of each blade. A machine for grinding the blades a on a cutting cylinder A of a lawn mower A<SP>1</SP> has a frame A<SP>2</SP> on which a sub-frame b is adjustable both vertically, by a handle b<SP>4</SP> and gearing b<SP>1</SP>, and transversely, by a handle b<SP>41</SP> and a screw b<SP>42</SP>. Bars B, B<SP>1</SP> have their ends located in slots b<SP>13</SP> in the sub-frame, and are secured together by slotted arms and U-bolts. A lawn mower has the gear case, bottom knife plate, front roller and chain sprocket on the cutting cylinder removed and the mower is inverted and mounted with the rear roller resting on the bar B<SP>1</SP>. Brackets B<SP>2</SP> are clamped by U-bolts b<SP>10</SP> to the bar B and the mower is secured by bolts b<SP>2</SP> passing through slots b<SP>3</SP> in the brackets B<SP>2</SP> and through the holes for the front roller of the mower. The driving spindle of the cutting cylinder is aligned with a head stock C and coupled thereto by a coupling c<SP>2</SP>. The main frame A<SP>2</SP> supports a screw b<SP>5</SP> driven by a belt 6<SP>11</SP> and engaging a split nut b<SP>6</SP> on a bracket b<SP>7</SP> supporting a carriage b<SP>8</SP> travelling on rails b<SP>9</SP> on the frame A<SP>2</SP>. A grinding wheel C<SP>1</SP> mounted in the bracket b<SP>7</SP> is driven by a motor c<SP>1</SP>. The grinding wheel C<SP>1</SP> is positioned to engage a blade a on the cylinder A and the headstock rotates the cylinder, e.g. at 16 r.p.m. The grinding wheel C<SP>1</SP> is traversed and grinds each blade to render all the blades truly cylindrical. The sub-frame is then raised and moved transversely. During backing off of each blade to reduce the width of the cutting edge the cylinder A is rotated by hand, e.g. by trimming one end c<SP>3</SP> of the coupling c<SP>2</SP>, to maintain the trailing edge of each blade in turn in contact with the grinding wheel as it traverses. The cylinder may be removed from the mower and mounted in V-bearings affixed to the bars.