GB635775A - Improvements in or relating to grinding, milling or the like machines - Google Patents

Abstract

635,775. Grinding and polishing. BRISTOL AEROPLANE CO., Ltd., WHITEHEAD, F. W., and BEDFORD, W. H. March 18, 1947, No. 7501. [Class 60] [Also in Group XXII] A machine, for grinding or milling the convex surfaces of gas turbine or compressor blades of the " coincident-line " type described in Specification 625,771, has a work-holder 67, which presents the blade to the peripheral cutting face of the tool and is given an angular feed movement about an axis substantially parallel to the axis of rotation of the tool, and a pair of cams 43, which lie one on each side of the work-holder and act together to move it laterally to and from the tool and to incline it lengthwise to the tool cutting face. The tool head 26, Fig. 3, is mounted for lateral in-feed by a hand wheel 24, on slides 25 on the machine bed 21 and comprises a grinding wheel or milling cutter 29 which is of greater width than the length of the blade and is driven through a gearbox 27 from a motor 28. The blade 70, Fig. 4, is held by clamps 69 against a tapered channel-section block 66 secured to a removable work-holder 67 ; the walls of the block in the cutting area of the tool are machined away, first by rough machining and then by means of the tool 29 while the block is mounted in the holder 67. The work-holder has tongue- and-slot connections with shafts 36, Fig. 5, which are journalled in bearings 34 on a table 33 pivoted at 37 on a slide 32 capable of being reciprocated to and from the tool head under the control of cams 43, one on each shaft 36. Weights 57 on ropes 55 connected to pulleys 54 hold the cams in contact with rollers 44 on the machine bed. The work-holder may be rotated by a motor 60 or a hand wheel 62 through a drive comprising a gearbox 59, a telescoping shaft 58 having a splined sleeve 64, a worm 53 and worm wheel 52 and a dogclutch 46 operated by a lever 48. When the work-holder is moved angularly about its axis the slide 32 is reciprocated and, if the cams 43 are arranged so that their points of maximum lift are relatively angularly displaced, the table 33 will be oscillated on the pivot 37. The shape of the convex surface is generated by one angular movement of the work-holder but the movement may be repeated several times with lateral in-feed of the tool head. Subsequently, the concave surface of the blades is formed in another machine and the excess material at the tip of the blade is removed. The cutting face of the tool may be straight, curved or part curved and part straight, the coincident lines produced on the blades being formed correspondingly.