Patent GB-657954-A (GB)
Title: Improvements in or relating to hand grinding and/or polishing apparatus
IPC: B24B23/02
Filed: 1949-03-31
Abstract: 657,954. Grinding and polishing. PATCHETT G. W. and STERLING ENGINEERING CO., Ltd. March 31, 1949, No. 8786. [Class 60] A hand polishing and/or grinding apparatus comprises a casing, an. electric motor mounted within said casing, a spindleadapted to. be driven by said motor-extending through said casing at one' end thereof at right angles to and offset from the longitudinal axis of said casing and said motor, means on the end of said spindle for detachably securing thereto a head for the attachment of a polishing or grinding disc or pad, a fixed handle on said casing and a secondary handle pivotally mounted on said casing, and means for connecting said motor to an electrical supply and for connecting and disconnecting said supply at will. The casing is in three parts, viz. a rear part 1 housing an electric motor 4, a central part 2 enclosing a cooling fan 5 for the motor 4 and a front part 3 housing the gears imparting drive to a spindle 6 extending through the first part 3. The parts of the casing are secured together by bolts 7; a handle 8 is secured to the casing parts 3, 1 by bolts 9, 10. The rear end of the handle has two rearwardly extending legs 11 which, in conjunction with the rear upper portion 12 of the handle, constitute a threepoint stand for the apparatus when not in use. The forward part of the handle is shaped so as to provide a thumb rest 13 on either side thereof. A thumb switch 14 is mounted in the upper part of an opening 15 extending through the front portion of the handle, the lower part of the opening 15 communicating with a further opening 16 in the centre part 2 of the casing, so providing access to the interior of the casing for the passage of leads 17 from the switch to a cable 18 for connection to the power supply. The rear casing part 1 and the rear part of the handle 8 have coincident entry openings 19, 20 for the cable which is secured by a rubber plug 21 retained by a plate 22. The end wall of casing part 1 carries a ball bearing 23 supporting the rear end of the driving shaft 24 the front end of which is supported by a ball bearing 25 carried by a dividing wall 2a integral with the casing part 2; a sealing washer 26 is retained by an annular plate 27, thus preventing lubricant for the spindle 6 from penetrating to the motor 4. The shaft 24 carries a worm 28 which drives a worm wheel mounted on the spindle 6 which is journalled at either end in bearings arranged in the casing part 3. The protruding end of the spindle 6 carries a boss 30 formed with internal dog clutch members adapted to be detachably engaged by corresponding dog clutch, members on a boss 31 to which is secured a disc 32, the boss 31 and disc 32 forming a head to which may be attached a polishing, grinding or buffing pad 37. The end of the spindle 6 is formed with recesses adapted to co-operate with a spring clip mounted within the boss 31, whereby the parts can be engaged and disengaged by rotation of one relative to the other. The disc 32 is formed with arcuate slots 36 so as to import flexibility; the grinding, polishing or buffing pad 37 is secured to a circular piece of fabric 38 (of greater diameter than the disc 32) having a peripheral hem and draw string 39. When pressure is applied to the pad 37 during operation, the material of the pad protrudes through the slots 36 to provide secure driving engagement between the pad and disc 32. An auxiliary handle 33 is mounted on the front part 3 of the casing so as to pivot therefrom at right. angles to the vertical axis of the spindle 6; the handle 33 pivots about an axially perforate post 35 containing a sliding spring-loaded plunger 35a, and the handle is normally locked against rotation by balls engaging between it and recesses in the post 35. Depression of plunger 35a frees the handle for rotation. The motor circuit includes a suppressor unit 43 held in the casing part 1 by a spring clip 44. The casing parts 2, 1 have slots 40. 41 for inlet and exhaust of air for cooling the motor 4 under the action of the fan 5; the slots are preferably internally covered with wire gauze 42 to prevent the entry of foreign matter 'to the motor 4.