GB749997A - Process and apparatus for making turbine or compressor blades - Google Patents

Abstract

749,997. Making turbine and compressor blades. POWER JETS (RESEARCH & DEVELOPMENT), Ltd. July 13, 1953 [July 11, 1952; June 4, 1953], Nos. 17523/52 and 15405/53. Classes 83 (2) and 83 (4). [Also in Group XXVI] Turbine or compressor blades are made by upsetting on a strip 1 evenly spaced enlargements 2 for the blade roots, and then passing the blanks so formed, as a continuous length or as individual blade blanks, through bladeforming rolls. A length of circular section material is flattened by rolling to form the flat strip 1, Fig. 1. If the finished blades are tapered along their length, rotary swaging of the strip is carried out, preferably before flattening, to produce a strip having a succession of portions tapering from maximum to minimum width or diameter. The strip is then passed through an electrical upsetting machine, Figs. 1, 4, from which it passes through the rolls, Fig. 2. The rolls may finish the blade portion and root or they may be machined to final shape after rolling. As the blades leave the rolls they are parted off by a rotary slitting tool which travels with the moving strip. The blades are then twisted. Alternatively the blade blanks may be parted off from the strip before rolling or before the last stage of a multi-stage rolling operation especially when blade twist is to be imparted during rolling. The blades 4, Fig. 5, may have roots of fir-tree form 3a, of bulbous form 3b or of dove-tailed form 3d, Fig. 3 (not shown). In the latter case the dovetailed enlargement may form only part of the root and may fit into a dovetailed groove in a block which completes the root. Alternatively two blocks may be provided, one on each side of the enlargement. The blades are mounted in seatings 46a, 46b or 46c which are broached or milled in a stator or rotor ring 46. The bulbous root 3c has flats 3m, 3n which seat against corresponding flats in its seating 46c to prevent relative angular movement. The bulbous root 3b is secured in its seating by a key 47 which locates the root rigidly or with a slight clearance to allow a slight angular movement of blade in its seating. Upsetting.-The upsetting machine of Fig. 1, comprises a pair of vices 5, 6, having viceblocks 7, 8, respectively closable by hydraulic actuators 9, 10 respectively and connected across the secondary of a transformer 13. The strip which passes through cavities 7a, 8a in the vice blocks, is gripped thereby and the vice blocks are then moved together to upset the strip therebetween. Recesses such as 8b in the adjacent surfaces of the vice blocks form a radius where the upset merges with the strip. The upsetting may be formed as a step-by-step operation or preferably as a continuous operation. For performing the latter the vices are mounted on platforms 15, 16 respectively slidable along guides 17. Platform 15 is connected by rods 24 to small-throw cranks 22 on a crankshaft 20 driven continuously by gearing 21. Platform 16 is connected by rods 25 to largethrow cranks 23. The vices are thus moved in the same direction but due to the differences in throw of the cranks, are brought together and separated in alternate sequence. High-frequency induction heating may be used instead of resistance heating. Upsetting and rolling.-Instead of the machine of Fig. 1, the strip 1 may be upset by passing it through rolls 30, 31, Fig. 4, having recesses 30b, 31b which indent the strip across its width at spaced intervals, and shoulders 30a, 31a which form abutments for the strip whilst it is upset by a vice 33 moved along guides 36 by an hydraulic actuator 35. The strip is heated electrically by a high-frequency induction heater 39, or alternatively by resistance heating. In the latter case the rolls and the vice serve as the two electrodes. Circular section stock may be passed through these rolls and be flattened thereby besides being upset. Rolling. The strip 1 with the spaced upsets 2 is then passed through the blade-forming rolls 41, 42, Fig. 2, driven by gearing 43. These rolls have peripheral recesses 41a, 42a, which form the blade portion, and recesses 41b, 42b which form the root portion. The recesses may be tapered to produce blades with tapering chord and thickness and the recesses may also impart blade twist. These recesses may be provided by removable die inserts. The rolling may be performed cold or preferably hot, in which case the strip passes through a highfrequency induction heater 44. Alternatively resistance heating may be used. More than one pair of rolls may be used in which case the rolling is performed in stages and the strip may be reheated between adjacent rolls. Specifications 619,634, 648,783 and 660,282 also are referred to.