Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2003-09-12
2004-09-28
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
C219S069150, C219S069200
Reexamination Certificate
active
06797912
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a disk-shaped or annular stator component or rotor component with a plurality of blades arranged one after another in a path extending around the component for guiding a gas flow. In other words, such a component can be used in both static applications (stators) and dynamic applications (rotors). This component is commonly referred to as a “blisk” (bladed disk) or a “bling” (bladed ring). The invention also relates to a device for manufacturing such a stator component or rotor component.
In the following description, the stator component or rotor component is intended to be arranged in a turbopump in a space application. Turbopump means a unit which comprises (includes, but is not limited to) at least a turbine and a pump part driven by the latter. The invention is not to be regarded as being limited to this application, however, but can also be used in a gas turbine. Other areas of application are also possible, such as in engines for vehicles, aircraft, power plant equipment for vessels and power stations for electricity production.
The stator component or rotor component is often designed with an annular cover outside, in the radial direction, and in contact with the blades. This cover outside the blades is arranged for the purpose of counteracting leakage from a pressure side to a suction side of the blades concerned. Such leakage is associated with efficiency losses.
2. Background
There are a number of different known ways of manufacturing such a stator component or rotor component. According to a previously known manufacturing technique, each of the blades is manufactured individually. The blades are subsequently secured with a mutual spacing in a groove on the periphery of a circular disk so that they project in the radial direction from the latter. Each of the blades is often manufactured with a cover part in such a way that an essentially continuous cover is formed after the blades have been mounted on the circular disk.
It is also known to use spark erosion in the manufacture of the stator component or rotor component. In this case, each blade is produced separately by spark-eroding a disk-shaped or annular workpiece intended to form the component. Four spark-erosion stages (and four different spark-erosion electrodes) are required for manufacturing each of the blades. During spark erosion, half the blade is machined from a first side of the workpiece via a first and a second spark-machining operation on the pressure side and, respectively, the suction side of the blade. When all the blades have been machined from the first side of the workpiece, it is turned, and the remaining part of each of the blades is machined from the second side of the workpiece via a third and a fourth spark-machining operation.
SUMMARY OF INVENTION
One object of the invention is to provide a method for manufacturing a disk-shaped or annular stator component or rotor component which is time-efficient and cost-effective. The invention also aims to achieve a manufacturing method which creates possibilities for a component with great strength and improved efficiency.
This object is achieved by virtue of the fact that at least a portion of each of a plurality of channels in a first set of channels is spark-eroded simultaneously out of a disk-shaped or annular workpiece intended for forming the component, which channels are intended to delimit the blades in the circumferential direction of the workpiece.
On the whole, the manufacturing method is non-sensitive to the material to be machined. The stator component or rotor component is manufactured from a single piece of material, which creates possibilities for great strength, especially in combination with a material which tolerates great temperature transients, such as what is known as a superalloy. In order for it to be possible to machine a plurality of channels simultaneously, a plurality of spark-erosion electrodes are in engagement with the workpiece, simultaneously.
In such spark-machining, material is removed from the surface of the workpiece under the action of a power density which arises when short electrical discharges take place between a spark-erosion electrode and the workpiece. Here, the spark-erosion electrode has the shape of a negative replica of the intended shape of the channel.
According to a preferred embodiment of the invention, after spark erosion of the portion of the first set of channels, the workpiece is rotated through a distance in its circumferential direction, and then at least a portion of each of a plurality of channels in a second set of channels is spark-eroded. The spark-erosion electrodes intended for the spark erosion are therefore arranged at a spacing in the circumferential direction of the workpiece which is greater than the intended spacing between the channels. In other words, machining of a plurality of channels takes place simultaneously, after which the spark-erosion means is indexed and a new set of channels can be machined out of the workpiece.
According to a development, the workpiece is turned after all the channels have been spark-eroded from a first side of the same, and the remaining portion of the channels is then spark-eroded in the same way from its second side. In this way, relatively complex blade shapes can also be produced.
According to another preferred embodiment, the channels are spark-eroded at a spacing from the edge of the workpiece in the radial direction so that a cover is formed outside the blades in the radial direction and in contact therewith. In other words, the cover is formed by the material of the workpiece remaining outside the blades in the radial direction. In this way, a continuous cover is formed which creates possibilities for a component with great efficiency.
According to another preferred embodiment of the invention, in a first operation, a plurality of spark-erosion electrodes are machined, with a mutual spacing along a curved path, from at least one basic element arranged on a means intended for the spark erosion, and, in a second operation, the channels are spark-eroded from the workpiece by means of the spark-erosion electrodes. The machining in the first operation preferably comprises milling. The method for manufacturing the component therefore comprises two stages, namely firstly manufacturing the tool itself which is to be used for spark erosion and subsequently spark-eroding the workpiece by means of the spark-erosion tool manufactured in this way.
According to a development of the preceding embodiment, the attachment of the spark-erosion means has such a shape that it can be used on the one hand in a machine tool for the manufacture of the spark-erosion electrodes and on the other hand in a spark-erosion machine for the manufacture of the channels by spark erosion. In this way, the method can be implemented by means of conventional machines for milling and spark erosion.
According to another development of the preceding embodiment, a plurality of the basic elements are arranged on the spark-erosion means in a path extending around the means before machining, and at least one of the spark-erosion electrodes is machined from each of them in the first operation. By using a plurality of such basic elements, only one of these has to be replaced if one of the spark-erosion electrodes should for any reason become defective during milling thereof or during movement and mounting of the spark-erosion means in the spark-erosion machine.
Another object of the invention is to produce a device which creates possibilities for time-efficient and cost-effective manufacture of a disk-shaped or annular stator component or rotor component. This object is achieved by a device according to claim
12
. Further advantageous embodiments of the invention emerge from the following claims and the description.
REFERENCES:
patent: 4888863 (1989-12-01), Cox et al.
patent: 5014421 (1991-05-01), Swarden et al.
patent: 5188514 (1993-02-01), Inserra et al.
patent: 5922222 (19
Derehag Bengt
Petersson Alf
Evans Geoffrey S.
Novak Druce LLP
Volvo Aero Corporation
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