US 3849273 A
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United States Patent [1 1 [111 3,849,273
Johnson [451 Nov; 19, 1974  METHOD OF AND APPARATUS FOR 3,352,770 11/1967 Crawford et al 204/l29.5 X Y RADIUSSING AN ED 0 EDGES OF A 3,442,784 5/1969 Wieck 204/ 129.46 X 3,459,645 8/1969 Wilson et a1 204/286 X METALLIC AEROFOIL BLADE 3,551,316 12/1970 Gale 204/206  Inventor: Graham Frederick Johnson, 12 3,654,122 4/1972 Williams 204/297 R Forge Rd Redditch, England 3,696,013 10/1972 Tafapolsky 204/l29.55
 Filed: Jan. 4, 1973 Primary Examiner-F. C. Edmundson  Appl' Attorney, Agent, or Firm-Marshall and Yeasting  U. S. Cl. 204/l29.6, 204/l29.5, 204/224 M, 204/DIG. 12  1111. c: B23p 1/00, B23p 1/04  ABSTRACT  Fleld of Search 204/l29.46, 129.6, 129.55, A method of a apparatus for radiussing the g or 204/129'1 224 M edges of a metallic aerofoil blade by electrolytic machining wherein the electrolyte is flowed towards the  References cued edge to be machined from a hollow electrode.
UNITED STATES PATENTS 3,235,475 2/1966 Williams 204/222 X i 7 Claims, 11 Drawing Figures METHOD OF AND APPARATUS FOR RADIUSSING AN EDGE OR EDGES OF A METALLIC AEROFOIL BLADE BACKGROUND OF THE INVENTION This invention relates to the manufacture of metallic aerofoil blades and is concerned with radiussing the edges.
An object of the invention is to provide an improved method of radiussing an edge or edges of a metallic aerofoil blade and also apparatus for using in performing the method.
SUMMARY OF THE INVENTION In accordance with the invention we provide a method of manufacturing a metallic aerofoil blade including radiussing a longitudinal edge of the blade by electrolytically machining the same with said edge located in spaced relation to the working surface of an electrode and by flowing electrolyte from said working surface towards said edge during machining.
The invention also comprehends apparatus for carrying out the method comprising an electrode having a passageway formed therein and having an opening at a working surface of the electrode, means for mounting the electrode and a blade to be electrolytically machined with the edge of the blade to be radiussed oppowards a plurality of inlet ports 30, see FIG. 5, formed in the electrode, which comprises two parts which fit one above the other to define said passageway 18. The
site said passageway opening and in spaced relation to said working surface and a source of electrolyte con.- nected to said passageway to flow electrolyte therethrough and through said opening.
Further, the invention includes blades made by the method and/or in the apparatus according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic elevation of an apparatus in accordance with the invention;
FIG. 2 is a perspective view of an electrode thereof and an aerofoil blade mounted on the apparatus;
FIG. 3 is an exploded view of the electrode of FIG. 2, the electrode comprising upper and lower parts;
FIGS. 4 to 6 are sectional elevations of FIG. 2 taken on the lines 4 4, 5 5, and 6 6 respectively;
FIG. 7 is a fragmentary plan view of the electrode and blade shown in FIG. 2, the upper part of the electrode being removed;
FIGS. 8 to 10 are fragmentary vertical sectional views illustrating flow of electrolyte during electrolytic machining; and
FIG. 11 is a perspective view of a modified form of apparatus in accordance with the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus (FIG. 1) comprises an electrode which has a planar working surface 10 and is cathodic when electric current is connected thereto and to a clamp 12, which supports a blade 13 to be machined, in spaced relation to the working surface 10. The electrode has a slit 14 in the working surface 10 thereof and is arranged relative to the blade so that an imaginary surface medial of the longitudinal walls defining the slit intersects the blade substantially medially thereof at all positions along the length of the blade.
The slit 14 forms part of a passageway 18, the walls of which diverge in a direction away from the slit 14 totwo electrode parts are sealed in the vicinity of the ports 30 by means of a sealing strip 31.
Electrochemical machining, or electrolytic machining, is carried out by making the blade anodic, and flowing electrolyte from a tank 20 through the passageway 18, via ports 30, so that the electrolyte discharges from the slit 14 in the direction of said medial surface. The flow of the electrolyte may be by gravity flow, or by pumping, or possibly the flow may be gas-pressure urged (by fan 24). As the electrolyte discharges from the slit 14 it washes around the blade and then flows to a second container 22, FIG. 1.
The electrolyte both in nature, temperature and pressure (e.g., head), and the current applied, may be conventional and selected to suit the material of the blade.
The electrolytic machining effected removes metal from the corners, i.e., square or relatively so edges left by the previous operations, and radiuses the same, and the removal is proportional to the distance between such edge and the nearest cathode point. In practice it is found readily possible to produce a radiussed curve along the blade edge, of constantly varying radius to suit requirements, by appropriate positioning between the blade and slit [4. As metal is removed, the distance changes, and the flow pattern of the electrolyte also changes. FIG. 8 shows flow around a cropped blade edge whilst FIGS. 9 and 10 show subsequent stages during machining.
With small blades, it has been found possible to produce ideal shaping, with complete repeatability; the
factor which controls amount of metal removed is time (when all other parameters are held) and for thousandth parts of an inch or fractions thereof, microseconds of machining are or may be involved.
It will be appreciated that the current connections to cathode and anode may be timer controlled by conventional circuits (not shown) and that it is unnecessary tointerrupt electrolyte flow at the termination of machining, although in the apparatus described the upper container may empty, being refilled whilst the blade is removed and a fresh blade inserted.
If desired a number of blades may be machined simultaneously, using separate slits for each; the slitted electrodes may be readily'removable for replacement, since each electrode will be appropriate for a particular blade shape and size only.
Where the blades are integral with end blocks as illustrated it is possible to use slitted electrodes which have a planar face adjacent the blade per se and a stepped portion 25, FIG. 7, extending adjacent to the sweep of blade into the end block-so as to machine such radius at the same time.
FIG. 11 shows a modification in which electrolyte is supplied via flexible'pipe 38, to hollow electrode 32 which is displaceable along and about a guide rod 34 which also acts to supply electric current to the electrode 32, the latter being varied in inclination by a follower 36 (of insulating material) to maintain the slit formed in the electrode 32 in alignment with the edge of the blade to be radiussed during displacement of the electrode 32 along the guide rod.
1. A method of radiussing a longitudinal edge of a metallic aerofoil blade, comprising the steps of:
placing, in spaced relationship with the longitudinal edge of the metallic aerofoil blade, the working face of an electrode, said working face;
a. having a slit, extending parallel and directly pposite to said edge, for discharge of electrolyte against said edge, and
b. being so configured that no constraint is placed by said working face upon the flow of electrolyte leaving said slit,
passing a stream of electrolyte through said slit, against said edge, and thence around both sides of said aerofoil blade,
and applying an electric current to the electrode and blade in such a manner that the electrode is cathodic and the blade is anodic,
thereby performing electrolytic machining by free flow of said stream of electrolyte to produce a curve of constantly varying radius around the edge of the blade. 7 2. A method according to claim 1 wherein the stream of electrolyte leaving the slit flows toward the blade substantially in the medial plane of the blade.
3. A method according to claim 1 wherein the width of the slit is less than the thickness of the blade in the vicinity of said longitudinal edge.
4. A method according to claim 1 wherein said working face of the electrode is planar.
5. A method according to claim I wherein said slit is coextensive with the length of the blade and is shaped ing face of the electrode is planar. l l