GB574521A - Improvements in or relating to portable surface grinding or polishing machines - Google Patents

Abstract

574,521. Grinding and polishing. CHAMPAYNE, R. J. Nov. 10, 1943, No. 18683. [Class 60] A portable surface grinding- or polishing- machine comprises a rubbing-device mounted on a flexible skirt and driven by a self-contained electric or fluid-pressure motor, or from an external source so as to perform a gyratory movement without rotation. The machine comprises a hollow housing 4 having a handle 7 and enclosing a motor 5 and supporting a rubbing-device 6, the housing 4 being of resilient material, for example, synthetic rubber, and having a thick top 10 and thinner depending skirt 11. The lower end of the skirt is closed by a plate 13 riveted at 14 to a flanged disc 15 fitting the skirt and held by a ring 17 tightened around the flange; within the skirt is mounted a compressed air motor comprising an annular casing 18 with end plates 19, 20, and having therein a cylindrical rotor 23 of diameter less than the chamber within the casing. The rotor is keyed to a shaft 25 and runs in ball bearings 26 supported in the plates 19, 20, and in the rotor are radial slots 31 supporting vanes 32; air is admitted at a port 30 and is exhausted by a port 34, and a tapered slot 33 in the casing wall ensures initial starting of the motor. On the shaft 25 is an eccentric pin 36 which engages a ball bearing 37 mounted in a stamping 39 on the plate 13 ; rotation of the shaft 25, therefore, causes the plate 13 to move in a circular path, it being held against rotation by the skirt 11. Thrust of the rubbing-device due to pressure on the work is taken by balls 40 in a cage 41 located within the disc 15, the balls engaging a ring 42 in the disc and a plate 29 secured on the end plate 20. The handle 7 is hollow and is secured to the casing 18 by means of a valve casing 46 and a hollow screw 53, which serves also as an inlet for air led to a connector 56 on the handle; in the casing 46 are the inlet and outlet ports 47, 30, and a valve 49 normally held closed by a spring 52, but controllable by a lever 9 pivoted at 57 and engaging the valve stem 51. The rubbing- device 6 comprises a rubber plate 60 with flanges 61, 62 adapted to be fitted on the plate 13, the abrasive paper &c. 65 being held by wires 67 fastened to the plate 60 by a rivet 70, and having their ends 71 in engagement with tubes 72, which, when in operative position, lie in grooves 73 in the plate 60 to clamp the ends of the paper 65; a layer of sponge rubber 66 may be provided on the plate 60. In a modification, the skirt is closed at its lower end by a rubber plate forming the support for the rubbing-device, the top of the skirt, within which the motor is located, being closed by a metal cap ; thrust is taken up by the use of thrust ball bearings.