Patent GB-704104-A (GB)
Title: Improvements in sanding machines
IPC: B24B21/16
Filed: 1951-05-30
Abstract: 704,104. Abrasive belt machines. ABBEY, A. (Bouligny, Inc., R. H.). May 30, 1951, No. 12781/51. Class 60 A sanding machine comprises a frame structure, a driven pulley and an idler pulley disposed on said frame structure in spaced relation for carrying an endless sanding belt, and a pressure pad mounted intermediate the spaced pulleys for lowering or raising alternatively to apply the endless sanding belt to the work to be sanded or release it to run clear of the work, the pressure pad being mounted on a supporting arm carried by the frame structure for pivoting movement about a horizontal axis extending transversely between the working and return reaches of the endless sanding belt, and the supporting arm being formed with a pivoted joint adjacent the point of pivoted support on the frame structure, the axis of the pivoted joint being disposed at right angles to the horizontal pivot axis and being positioned vertically when the supporting arm is disposed to position the pressure pad at its farthest downward extent. General. The sanding machine comprises an endless sanding belt B passing around driven and idler pulleys D, I carried by the machine frame S, a feed table T, feed means F, a pressure pad P for applying the belt to the work, and guide means G for the work. The sanded work is received on a table 36. The frame S has an enclosed base portion 10, with an access door 12, providing storage space for tools and maintenance supplies ; the frame has a hood portion 14 with a fitting 16 for attachment to a suction recovery line to carry off dust produced during the sanding operation. Guide means. The guide members G, which are secured in place by clamping arms 18, are preferably of wood shaped to the desired form and comprise front and rear guide pieces 28, 30 forming a channel for the work W; a support piece 32 is arranged directly beneath the pressure pad P for providing a free path for the sanding belt so that it may run in contact with the full contour of the work ; the top surface of the frame is undercut at 34 to receive the support piece 32. Idler pulley. The idler pulley I is mounted by bearings 106 on a shaft 104 carried by a post 102 vertically adjustable in a bracket 114. The bracket 114 is secured to a bottom slide base 126 which is connected to a top slide base 134 by a pivot pin 132 aligned vertically with the axis of the pulley I at its middle crosssection. The slide bases 126, 134 are longitudinally adjustable on slide bars 128, 130 by a screw operated through gearing by a hand wheel 140. The pivotal adjustment of the slide base 126 relative to the slide base 134 is effected by a screw 156 operated by a knob 154. Driven pulley. The driven pulley D is mounted directly on the shaft of an electric motor 202 carried by a motor bracket 206 vertically adjustable on a mounting plate 208 secured to the machine frame S. The driven pulley D is disposed on the frame structure S at the end opposite to the end at which the work W is fed beneath the sanding belt B by the feed means F ; the driven pulley D is operated to drive the sanding belt B in a direction opposite to the direction in which the work W is fed for sanding. Slack i s thus induced in the sanding belt B between the pulley D and the pressure pad P which facilitates the application of the sanding belt B by the pressure pad P in conformance with the irregular contour of the work W. Auxiliary idler rolls. An auxiliary idler roll 224 is mounted near the driven pulley D, being carried by an arm 228 which is clamped in vertically adjusted position on a vertical shaft 230 which is rotationally adjusted by a knob 256 in a bracket secured to the mounting bracket 206 for the driven pulley D. The disposition of the idler roll 224 relative to the pulley D is such that the sanding belt B is subjected to a reverse bending as it is taken over the idler roll 224 on to the pulley D which maintains it flat even when a substantial amount of longitudinal creasing is present in the belt B. The auxiliary idler roll 224 also serves, by virtue of its pivotal adjustment, for correct tracking of the belt. An auxiliary idler roll 170 may be arranged near the idler pulley I, so mounted that it can be moved to an inoperative position clear of the sanding belt B when not needed. Pressure pad. The pressure pad P by which the sanding belt B is applied to the work W is disposed between the working and return reaches of the belt at the end of a supporting arm 300 carried by the frame S and pivoted about a transverse horizontal axis to allow the pad to be lowered or raised as desired ; when the supporting arm 300 is in raised position it is disposed substantially parallel to the line of travel of the reaches of the belt so that adequate clearance for adjustment of the pad is provided, the driven and idler pulleys being no larger than is necessary for carrying the belt to the best advantage. The horizontal pivot axis for the supporting arm 300 is formed by a tubular pivot shaft 302 carried in a mounting bracket 304 vertically adjustable on the frame structure S. The shaft 302 is adjustable axially by means of a screw 320 operated by a knob 326. The supporting arm 300 is raised and lowered, to shift the pressure pad between operating and in active positions, by a cam 348. on a shaft 342 operated by a handle 346. The supporting arm 300 is in two parts 306, 308 connected by a pivot pin 310 ; the first part 306 has a hub 312 fixed to the pivot shaft 302 and a yoke for receiving the pin 310, the upper portion.of the yoke part extending as a covering apron over the second part 308 ; the latter carries a mounting bracket 314 for the pressure pad P. The apron portion of the part 305 carries adjusting screws 316 bearing oppositely on springs 318 disposed at each side of the second part 308 for maintaining it normally balanced at a centrally aligned position while allowing it to shift laterally. The pivot 310 is positioned substantially vertically when the supporting arm 300 is lowered to position the pressure pad at its furthest downward extent, viz. directly on the frame structure S with no work disposed beneath the sanding belt. Accordingly, when work W is fed beneath the sanding belt the supporting arm 300 will be positioned above its furthest downward extent and the pivot 310 is inclined backwardly from the vertical so that any lateral movement of its supporting arm will cause the pad to be applied with greater force against the belt which, together with the gravity force on the pad sets up a movement about the pivot 310 tending to return the supporting arm to normal position. In order to regulate the pressure with which the sanding belt is applied by the pressure pad, weights 358 are adjustably mounted on guideways 356 on the hub portion 312 of the part 306 ; the guideways are extended rearwardly to form counterweight balance arms 360 for supporting a counterweight when necessary. The pressure pad holder 366 is pivoted at 368 to the mounting bracket 314, and forwardly, rearwardly and laterally extending arms of the holder carry spring-pressed plungers 372 ; the holder 366 has a depending flange 374 at the end of its rear arm portion fitted with a semi-circular bracket 376, and depending flanges 378, formed with inwardly extending bottom edges 380 to form an undercut longitudinal slot, arranged substantially centrally of the holder. A mounting plate 382 which carries the pad P directly is formed with two upstanding ball-pointed studs 384, 386 fitting in the longitudinal slot formed by the flanges 378 and disposed in the semi-circular bracket 376 respectively. The mounting plate 382 is thus free to float in all directions while fully restrained in longitudinal alignment. Feed means. The work is fed beneath the sanding belt by bottom feed roll 400 and an overhead pressure wheel 402. The roll 400 is carried on a shaft 404 journalled on the frame structure S and driven by an electric motor 406 through belt or chain drive 408, gear box 412 and belt or chain drive 410. The pressure wheel 402 is axially adjustable on a stub shaft 418 journalled in a bearing 420 vertically adjustable in a housing 416 by a screw 426 operated by handwheel 428. The stub shaft 418 is driven through bevel gears 430, 432 the latter slidably keyed on a vertical shaft 434 driven through bevel gears 436, 438 by the roll shaft 404. Speed variation is effected by vertical adjustment of the motor 406 by handwheel 442. Feed table. A supply of the work to be sanded is maintained at the feed means F by a feed table T comprising a housing frame 500 secured'on the frame S and carrying a conveyer belt 502 on pulleys 504, 506. The rear pulley 506 is adjustable towards and away from the front pulley 504 for tensioning the belt 502. The front pulley 504 is driven through a belt or chain drive from the gear box 412 which drives the feed roller 400. Front and rear guide members 526, 528 are provided for channeling the work on the convever belt to the feed means. The rear guide 528 consists of an upstanding guide flange of substantial height extending. substantially the entire length of the feed table and carried on the frame 500 by pivoted arms 530 which allow it to be spaced over the conveyer belt 502 as desired. The front guide 526 consists of an upstanding flange of comparable height but of relatively short extent, pivoted at 532 on the housing frame 500 for angular disposition adjacent the forward end of the rear guide 528 so as to direct the work against.the rear guide as it is advanced forwardly on the belt 502. Beyond the forward end of the rear guide 528 is provided a gate member 534 consisting of a vertically disposed plate arranged for sliding adjustment . in a slide clamp 536 so that its lower edge may be adjusted above the level of the conveyer belt in accordance with the thickness of the work being handled for allowing only one piece of work at a time to pass on to the feed means F.