Patent GB-736050-A (GB)
Title: Improvements in or relating to polishing machines
Inventor: WHITEHEAD FREDERICK WILLIAM
IPC: B24B35/00
Filed: 1953-05-06
Abstract: 736,050. Polishing turbine blades. BRISTOL AEROPLANE CO., Ltd. May 3, 1954 [May 6, 1953], No. 12674/53. Class 60. The two side surfaces of a turbine or other blade 10 are polished by reciprocating it in its lengthwise direction while it is supported between two opposed stacks 44, 45 of pads, each pad being mounted in a holder 55 which is individually movable towards and away from the blade and is resiliently pressed against the blade. The blade 10, Fig. 2, is supported by a holder 18 so as to hang vertically above a verticallymovable and counterbalanced table 12 which comprises a fixed rear part 39, Fig. 3, carrying the stack 44 and a horizontallyslidable front part 40 carrying the stack 45 ; a pneumatic jack 41 moves the part 40 and stack 45 to and from operative position. The work holder 18, Fig. 2, is supported for combined vertical and transverse reciprocation by slides 21, 20 which are driven by a motor 26 through adjustable eccentrics (22, 23, Fig. 1, not shown) whereby the blade is moved in a rotary or wavy path between the stacks ; preferably the rate of vertical reciprocation is greater than that of transverse reciprocation. The holder 18 carries a horizontal pivot 18a for a chuck carrier 18b in which the chuck 19 is supported for pivotal movement about a vertical axis. Each of the pad holder stacks 44, 45 (whether on the fixed part 39 or slide 40) comprises a set of superposed L-shaped arms 49, Figs. 3 and 4, journalled at one end on a vertical shaft 47 and engaging at its other end in grooves 53 in a post 51. A pad holder 55 is mounted on the inner face of each arm by a vertical pivot pin 54 and consists of a block having a groove 56 to receive, with clearance, the arm and a rubber or felt pad 60 on the opposite face. Each pad and its associated pin 54 are retained in place by top and bottom plates 105, and the pad, more especially when of felt, may be additionally supported by an internal beam in the form of a stiff coil spring 61 seated at its ends in the holder; the pad may also be backed by a strip of sponge rubber. The pad holder is aligned with its arm 49 by coil springs 68 seated at the ends of the groove 56 and bearing against the arm. Each of the arms 49 on the side opposite to the pad is engaged by an adjustable spring- pressed plunger 67 mounted in a post 63. A felt strip 91 may be supported over the pads of each stack by pins 90 and a sheet 95 of emery cloth may be stretched over this strip by clamps 92. The operative faces of the pads of each stack are of such a shape and extent that they combine so as to conform in shape and extent to the whole of the corresponding side surface of the blade to be treated. The blade may be first oscillated in contact with the emery sheets 95 supported on the felt strips 91, and then immersed in a viscous mixture of oil and powdered abrasive prior to further oscillation in contact with the felt strips 91 ; a timer provides for automatically controlling the period of a cycle. When the pads 60 are of felt, they may be used to bear directly on the blade for the final polishing step.