Patent GB-666035-A (GB)
Title: Improvements in or relating to rotary tools for grinding, sanding and polishing
IPC: B24D13/14
Filed: 1949-08-17
Abstract: 666,035. Flexible rotary rods. WATSON, R. D. Aug. 17, 1949 [Aug. 24, 1948; Dec. 8, 1948], Nos. 21405/49 and 21406/49. Class 60. A.portable rotary rod for grinding, sanding or polishing comprises a shaft with a threaded end to carry a backing plate for a brush member or resilient pad, a flanged sleeve passed through a central opening in an abrasive or polishing disc, and screw means for securing the sleeve to the spindle whereby the disc frictionally engages the brush member or pad with adjustable pressure. Four embodiments of the invention are described. In the first, the driving shaft 12, Fig. 2, which rotates at a speed between 1,300 and 5,500 r.p.m., is in screw threaded engagement with a hub 14 extended to form a backing plate 16 to which is secured a centrally apertured disc 18 of webbing, duck, vulcanized rubber or the like. A pile 22 of wool yarn or the like is secured to this disc by a layer of latex 20 and stitching 24 to form a pad which bears on the back of a flexible disc 36 of abrasive material, such as sandpaper or emery cloth. The disc 36 is also apertured to fit over a bush 32 which is rotatably mounted on a barrel nut 30 in engagement with the end of the driving shaft 12. The extent of engagement between the nut and the shaft is determined by the setting of a set screw 34 inside the barrel nut 30. This setting controls the pressure of the pad on the back of the abrasive disc. When the driving shaft is rotated, centrifugal force flattens the pad and the disc diminishing to some extent the frictional engagement between them. The application of excessive pressure between the tool and work causes the disc 36 and bush 32 to stop; thus preventing rupture of the abrasive disc. The set screw 34 is set in accordance with the roughness of the latter. In the second embodiment, a pad 46, Fig. 6, of soft rubber, felt or the like is loosely mounted between the flange 52 of a bush 50 and the flange 44 of a hub 40 in screw threaded engagement with the driving shaft. The abrasive disc 56 is placed between the flange 52 and the pad 46. Excessive pressure between rod and work first stops the disc 56 and after that the pad 46. In the third embodiment, the bush 50 is dispensed with and the nut 48 provided with a wider flange to hold the abrasive disc. The fourth embodiment employs a hub 100, Fig. 10, freely mounted on the driving shaft 102 and cemented to a resilient pad 106 against which the abrasive disc 112 is clamped by a flanged nut 108 in screw threaded engagement with the driving shaft. A spring washer 114 is interposed between the hub 100 and a washer 116 which is composed of a porous metal impregnated with lubricant and held in place by a split ring 118. The inner end of the nut 108 is reduced to pass through the split ring and engage the washer 116 so that the hub 100 and the nut are in frictional driving engagement through the medium of the spring. When excessive pressure is applied to the tool, this friction drive slips and the abrasive disc and the pad 106 cease to rotate. The pressure exerted by the spring is determined by the setting of a set screw 110. The Specification as open to inspection under Sect. 91 comprises also an embodiment in which a spring 82, Fig. 10 (Cancelled), holds a plate 74 and a nut 78 in engagement to form a spring- loaded clutch. The plate 74 is secured to the end of the driving shaft 70 by a bolt 72 while the nut 78, which is freely mounted on a bushing 76, is in screw-threaded engagement with a flanged hub 80. The latter is cemented to a resilient pad 86 to which the abrasive disc 90 is clamped by a screw 88. When excessive pressure is applied to the tool, the spring 82 is compressed and the nut 78 is lifted out of engagement with the plate 74 so that the hub 80 and its associated parts cease to rotate. The pressure exerted by the spring is adjusted by varying the extent of engagement of the nut 78 with the hub 80. A lock nut 92 is provided. This subject-matter does not appear in the Specification as accepted.