GB773101A - Improvements relating to the manufacture of compressor or turbine blades - Google Patents

Abstract

773,101. Making turbine and compressor blades. GENERAL MOTORS CORPORATION. May 13, 1955, No. 13874/55. Classes 83 (2) and 83 (4). A twisted turbine or compressor blade is made by cold rolling a flat strip blank to form the airfoil portion, cold upsetting the blank to form the root, and twisting the airfoil portion by cold deformation. The blade is made by shearing a blank 1, Fig. 2, having curved ends 3, 13 from stainless steel strip; annealing, deburring by tumbling, and coating the blanks with zinc phosphate lubricant; cold rolling each blank between gap rolls, preferably in two or more stages with annealing between stages, to form the airfoil portion with thickened edges 5, 7, Fig. 4, the blank being tapered in both length and thickness if desired during the rolling; trimming the tip and trimming the edges 5, 7, to the desired width, Fig. (not shown); upsetting the root end 3 of the blank in two stages, Fig. 6; trimming off the flash and grinding the root to shape, Fig. 7 (not shown); thinning the edges 5, 7 by cold coining, Fig. 22 (not shown), or rolling, Fig. 26 (not shown), preferably in two stages; trimming the edges of the blank to the correct thickness, Fig. 24 (not shown); twisting the blank by coining in dies or by torsion, Fig. 11 (not shown); finishing the blade to final shape, Fig. 13, by broaching the root ends 47, 49, grinding the root edges 9, 11, cutting the blade to length, grinding the edges 5, 7, to their correct radius and, if desired, polishing the blade. The polishing is unnecessary if polished coining dies are used. The finished blade may taper in thickness and width from root to tip. Upsetting. The blank is held in a die 35, Fig. 21, and its root end 3 is upset cold in two blows by a punch 37. Rolling. The blank 38 is rolled to airfoil shape in two stages between segmental rolls 30, 32, Fig. 27, secured to gears 46, 48 meshing with a rack 42 on a push-bar 28. The rolling apparatus is mounted on a press-table 24 with the press ram 26 engaging the bar 28. The root end of the blank is engaged in a work-holder 36 carried by a piston 34A biased upwardly by hydraulic pressure. Upon descent of the ram 26, the piston 34A and hence the blank 38 is moved downwardly positively by a latch 70, Fig. 29 (not shown), mounted on bar 28 and initially engaging the piston; during this time the rolls 30, 32 are rotated by the rack 42 but have not yet engaged the blank. At a predetermined and adjustable point in the stroke the latch is released and the blank is biased upwardly by hydraulic pressure on piston 34A until the upper end of the root engages the corners 92, 94 of the rolls, whereby the latter bite into the blank at the correct position. The latch mechanism is reset automatically upon the return stroke of the work-holder 36. Stepped surfaces 44 on the bar 28 co-operate with steps 50, 52 on the rolls 30, 32 to assist the rack 42 in rotating the rolls. To prevent the blank skewing during rolling, one or more ribs 45, 47, Fig. 35, may be formed on the blade portion during the first rolling operation. The ribs may be of triangular or semi-circular section and may be formed on either or both sides of the blank. The ribs are trimmed off after rolling. Twisting. The blade root 52 is gripped in a work-holder 48<SP>1</SP>, Fig. 40, which may be provided with hydraulically- or mechanicallyoperated jaws mounted on an hydraulicallyoperated ram 46<SP>1</SP>, and is drawn thereby through segmental rolls 30<SP>1</SP>, 32<SP>1</SP> driven through rack-andpinion gearing 40<SP>1</SP>, 42<SP>1</SP> by the ram. The latter is rotated during its movement by a pin 56 engaging a cam slot 58 in a fixed sleeve 60. The rolls are mounted on transverse sliders 26<SP>1</SP>, 28<SP>1</SP>, Fig. 36 (not shown), whereby they may be moved transversely towards or away from each other by hydraulic motors 66 through linkage 64. The movements of the ram and the rolls are controlled in sequence by micro-switches and an electrical control circuit, Fig. 41 (not shown), is given. In a simplified construction of twisting apparatus, Fig. 25 (not shown), the rolls are geared together and are driven by a single rack and the blank is rotated by a cam surface on the rotatable ram engaging a stationary follower.