Patent GB-823986-A (GB)
Title: Surface treating machine
IPC: B24B23/04
Filed: 1956-11-06
Abstract: 823,986. Portable sanders. SUNBEAM CORPORATION. Nov. 6, 1956 [March 7, 1956], No. 33885/56. Class 60. A surface treating machine e.g. for sanding, grinding, polishing or buffing, comprises a base plate 11 resiliently supported from a base member 12 in which is journalled a motor shaft 42 drivingly connected with a member 59 rotatable about a stub shaft 63 supported by the base member 12, the member 59 having an eccentric portion 61 received, with an interposed needle bearing 21, in a housing 19 secured to the base plate 11, whereby the latter is given a circular translatory movement. The rectangular base plate 11 of relatively heavy sheet metal has secured, e.g. adhesively, to its lower face a pad 18 of resilient material, e.g. pressed felt or rubber, to back the sandpaper 17, the ends of which are clamped against flanges 11 a, 11b at the ends of the plate 11 by bights 25a of resilient locking arms 25 mounted in trunnion supports lie and actuated by extensions 25d retained in clamping position by hooked tabs 11d, 11e on the plate 11. The base member 12 is a die casting, e.g. of aluminium, and the base plate 11 is supported therefrom by resilient columns 13, e.g. of rubber ; the upper end of each column has secured thereto adhesively or by moulding a bolt 13a engaging an insert 31 press-fitted into the base member 12, and the lower end of each column has similarly secured thereto a bolt 13b, the base plate 11 being secured thereto by a nut 28. The motor housing 14 is a die casting, e.g. of aluminium, and is secured to the base member 12 by fastening means 37. The corners of the lower end of the housing 14 rest on spacer projections 34 on the base member 12, thus providing air passageways 35 between the housing 14 and member 12 as well as between the spacers 34 ; each spacer 34 has a pair of projections 34a for locating the housing 14. The housing 14 mounts an electric motor having an armature shaft 42 journalled in a bearing 43 on the housing 14 and in a bearing 44 on the base member 12. The motor is cooled by a fan 46 on its shaft, air flowing through inlets 49 in the upper end of the housing 14 and out through the passageways 35. The top of the base member 12 immediately below the motor housing may have openings for the flow of motor cooling air so as to blow sanding dust away from the motor housing 14. The housing has an oil passageway 51 for lubrication of the bearing 43. The bearing 44 is lubricated by an oil wick 53 in a recess 52 in the base member 12 ; a combined bearing and oil wick retainer 54 is secured to base member 12 by screws 55. The lower end of the motor shaft 42 carries a toothed pulley 57 driving, through toothed belt 58, a combined toothed pulley. 59a and counterweight 59b to which is secured by means 60 a sleeve 61 having an eccentric bore 62 receiving a stub shaft 63 secured to the base member 12 by a nut 73 ; needle bearings 64, 65 are provided, lubricated through ducts 70a, 70b. The sleeve 61 is received within a sleeve 19 secured, e.g. by welding, to the base plate 11. A needle bearing 21 is provided, lubricated by an oil wick 22. The motor housing 14 has an integral extension 14b which together with a member 16a secured thereto at 74 forms a handle 16. A switch 76 with an actuating knob 81 has a mounting plate 77 received in grooves in the handle portions 14b, 16a. A knob 86 is detachably secured to the motor housing 14. A bracket 92 secured to the base member 12 by one of the fastening means 37 holds a damping pad 91 against a vertical wall of the base member 12 to minimise vibration ; alternatively, the vertical walls of the base member 12 may be lined with pressed felt.