Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1992-09-29
1994-05-24
Valentine, Donald R.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204225, 204284, B23H 300, B23H 304, B23H 726
Patent
active
053145984
DESCRIPTION:
BRIEF SUMMARY
This invention concerns improvements in or relating to electrochemical machining, and in particular relates firstly to an improved method of using an electrochemical machining operation to shape an edge of an electrically conductive component, and secondly to provide precision broaching of metal and alloy components. A specific embodiment of the invention contemplates shaping said edge so as to provide a radius thereon.
The principles and general techniques of electrochemical machining are well known and are described in, for example, U.S. Pat. No. 3,723,268 (assigned to Production Engineering Research Association of Great Britain), to which the reader is referred.
Generally, the present invention provides in a first aspect a method of shaping an edge of an anodic workpiece in an electrochemical machining operation by controlling the intensity of the electrical field in the electrolyte adjacent said edge, in a second aspect an electrochemical broaching apparatus for making a channel in a workpiece, and in a third aspect a method of supplying electrolyte to a electrochemical machining tool in a broaching operation.
According to a first aspect of the present invention there is provided a method of electrochemically machining a workpiece made of electrically conductive material so as to provide a radius on an edge of the workpiece, the method comprising, (a) providing a cathodic tool comprising a cathode section sandwiched between two anode sections and separated therefrom by insulation, (b) locating the tool adjacent to but separate from the workpiece so that the cathode section is positioned centrally over the edge of the workpiece to be radiused and the anode sections lie facing opposite sides of the edge, (c) causing electrolyte to flow between the tool and the workpiece, (d) applying a cathodic voltage to the cathode section, (e) applying preselected anodic voltages simultaneously to the workpiece and the anode sections so that electrical field null points between the cathodic tool and the workpiece lie either side of the edge to be radiused, and (f) varying the electrical field between the tool and the workpiece so as to cause the null points in the electrical field to move with respect to each other and said edge of the workpiece to ensure an overall energy distribution across said edge, thereby to create the radius required.
According to a second aspect of the present invention there is provided an electrochemical broaching apparatus comprising an electrolyte bath, a first end wall of which is provided by a workpiece of electrically conductive material to be broached, an elongate broaching tool, an elongate horizontally disposed support member adapted to carry underneath it the broaching tool, the workpiece providing the anode of an electrochemical broaching operation and the broaching tool providing the cathode of the electrochemical broaching operation, wherein the support member is arranged to be supported by a second end wall of the bath opposed to the first end wall and to be moved in its elongate direction over the bath and over the workpiece, and the broaching tool is of a wedge shape, the narrow end of which is near the first end wall at the start of the broaching operation and the remainder of which is immersed in the electrolyte bath.
According to a third aspect of the present invention there is provided for use in an electrochemical machining operation a broaching tool for making an aperture in an anodic workpiece, the tool being provided with at least one cathodic portion and characterised in that at least two portions of the tool are provided with mutually independent means for supplying electrolyte to the tool.
The invention will now be described by way of example with reference to the accompanying diagrammatic non-scale drawings in which,
FIG. 1 is a perspective view of a dovetail slot in a rotor disc of a gas turbine engine. Such a slot is used for locating engine compressor and turbine blades in the disc.
FIGS. 2, 3 and 4 are respectively left-hand, middle, and right-hand segments in
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Patent Abstracts of Japan, vol. 6, No. 232 (M-172)[1110], Nov. 18, 1982; & JP, A, 57132949 (Tokyo Shibaura Denki K.K.) Aug. 17, 1982.
Cannon Alan J.
Dunlop Roger N.
Glew Derek A.
Staines Alan D.
Rolls Royce plc
Valentine Donald R.
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