Patent GB-896170-A (GB)
Title: Method of and apparatus for imparting a smooth finish to flat surfaces of fibrous non-metallic material
IPC: B24B21/00
Filed: 1958-10-16
Abstract: 896,170. Finishing wood &c. PENDERGAST, R. F. Oct. 16, 1958 [Oct. 21, 1957], No. 33103/58. Class 60. A method of imparting a smooth finish to a flat surface of a workpiece of fibrous non- metallic material, e.g. wood, comprises moving an endless abrasive belt through a working path having an arcuate portion and a flat portion tangent to and spaced from the arcuate path portion; moving a workpiece, having a flat surface to be finished, in a path parallel to the flat portion of the working path of the abrasive belt; imparting working pressure to the belt against the workpiece surface at the arcuate path portion to cause the belt to have a relatively small arc in working contact with the workpiece surface, whereby to effect an initial relatively deep rough cut on the workpiece surface; imparting working pressure to the belt against its workpiece surface at the flat path portion to cause the belt to have a relatively large flat area in working contact with the workpiece surface, whereby to effect a relatively fine finishing operation on the workpiece surface; and directing the belt away from the workpiece surface at the opposite ends of the working path. A panel-like workpiece X of wood or similar material is supported by rolls 6, 7 journalled at their ends in side walls 2, 3 of the machine frame. A secondary frame 8 is mounted within the machine frame by a shaft 9 supported at one end by the side wall 3 and at its other end by a bearing portion 10 of a bracket 11. The bracket 11 is disposed within an opening 12 in the side wall 2 and is pivoted at 13, 13 to the side wall for swinging movement into and out of the plane of the side wall. A shaft 15 supported in bearings 16 on a secondary frame 8 and also supported at one end by a bearing portion 14 of the bracket 11 carries a contact roll comprising a cylindrical drum 18 with a grooved cover 19, e.g. of rubber. An idler roll 21 is mounted on a shaft 22 journalled in spaced bearing brackets 23 at the opposite end of the frame 8. A pair of arms 24 extending upwardly from the frame 8 support a platen 25 provided with a pad 26, e.g. of rubber, and a covering 27 preferably impregnated or coated with material having a low coefficient of friction, e.g. graphite. A wide endless abrasive belt 28 is entrained over the contact roll, idler roll and platen. The shaft 15 of the contact roll is driven, through multiple belts 31, by an electric motor 30. A pair of beams 35, 35 are pivotally mounted on a shaft 36 mounted in brackets 37 secured to the side walls 2, 3. Movement of the beams towards the machine frame is limited by adjustable screws 38. A feed roller 40 is mounted on a shaft 41 journalled in bearings secured to the beams and rotated by belts 45. Rollers 46, 47 are journalled on shafts mounted at their ends in blocks adjustable, by screws 54, 55, on the beams 35. Fibrous particles of material cut from the workpiece and adhering to the working surface of the belt 28 are removed therefrom by a rotated brush 56 or by an air jet. The belt 28 travels at 4,000-5,500 ft./min. and the workpiece at 30-100 ft./min. If the belt 28 travels in the same direction as the workpiece, fibrous particles removed from the work at the coarse grinding zone fill the spaces between the abrasive particles so that only the tips of the latter are effective at the finish grinding zone, and a burnishing action is also effected.