Patent GB-858334-A (GB)
Title: Method and machine for the surface treatment of workpieces of wood or other material
IPC: B24B35/00
Filed: 1957-05-03
Abstract: 858,334. Grinding. SCHUSTER, R. May 3, 1957 [May 9, 1956], No. 14227/57. Class 60. A method of working, e.g. finishing, the surface of a workpiece of wood or other material, e.g. a profiled workpiece, in which the work is carried out on a portion of the workpiece at a time by means of a reciprocating tool pressed against the portion of the workpiece being worked, comprises moving the workpiece to bring an unworked portion of it into the working position by temporarily releasing the workpiece so that it is advanced together with the reciprocating tool by the force of friction. A finishing block 8 acts on a profiled wood strip 7 supported by a bed constituted by rollers 5, 6. The finishing block 8 is fixed to a carrier 9 supported by a slide 20 reciprocated in a dovetail groove 10 in the frame 1 by an electric motor 11 through continuously variable gear 12, worm gearing 13, crank disc 15, connecting rod 16 and lever 17 pivoted at 18 and connected to the slide 20 at 19. The finishing block 8 is of moulded resin or cork, a sheet of abrasive paper or cloth being secured to it, e.g. by clips ; the carrier 9 may have mounted thereon a roll 45 of abrasive cloth or paper from which it can be unwound and clamped to the block 8 or to the carrier 9. The latter is universally mounted by a ball and socket mounting 46 on a lever 51, the finishing block 8 being pressed on to the work, through a link 49, by a spring 47. The finishing block 8 may have, superimposed on its reciprocation (60/min.), a short stroke (2 mm.) high frequency (3000/min.) reciprocation, e.g. by an electric motor on the carrier 9. The block 8 has suction bores therethrough, some of which register with holes in the abrasive sheet to remove wood dust and others of which serve to hold the abrasive sheet against the block. The rollers 5, 6 are bevelled at their facing ends 22 and have transversely ribbed coverings of resilient material, e.g. rubber, The rollers are carried by angle bars 29 secured by screws 30 in adjusted position on bars 26 secured by screws 28 in adjusted position in semi-circular guide slots 25 in the end walls 23, 24 of a slide 4' vertically adjustable on the machine frame 1 by a screw 2 and handwheel 3. Gears 31 fixed to the rollers mesh with intermediate gears 32 and two electromagnetic clutches 33 are provided on the shafts of two of the gears 32 so that when the clutches are energized rotation of the rollers is prevented. A switch roller 34, driven by a chain 43 from the output shaft of the worm gearing 13, has insulating material 36, and is contacted by a fixed contact 37 and a contact 38 movable axially of the roller 34 by a handlever 39. The contacts 37, 38 are in the circuits of the electromagnetic clutches 33 whereby dnring each rotation of the roller 34 the electromagnetic clutches 33 are deenergized, freeing the rollers 5, 6 for rotation so that the workpiece is carried along by the finishing block to a new position in which it is arrested when the clutches are again energized. The duration of de-energization, and therefore of travel of the workpiece, is proportional to the movement of the handlever 39. A gear 54, driven through chain 53 from the switch roller spindle, can be brought into mesh with one of the intermediate gears 32 so as to feed the workpiece continuously, e.g. during coating of the workpiece. Alternatively, the workpiece may be restrained against movement with the tool by a clamping jaw engaging its upper surface or by a pair of clamping jaws engaging its sides. In a modification Fig. 10, the workpiece is supported by elastic endless bands 64, e.g. of rubber, each passing over end rollers 61, 62 and supporting rollers 60. The band 64 has longitudinal and transverse grooves on its operative face and a guide rib on its other face engaging guide grooves in the rollers 60, 61, 62. The roller 61 has a resilient coating 68 and has associated therewith an electromagnetic clutch 65 to hold the belt, and therefore, the workpiece, stationary.