DE3533957A1 - Process of machining mainly turbine rotor blades, means and machine for applying the method - Google Patents

Abstract

The subject matter of the invention is in particular the technical area of electromechanical machining processes. The process is characterised in that the rotor (R) of the turbine is partly immersed in a dielectric fluid (FD); at least one means (8) for generating and controlling the electric current is attached above the fluid; this means is connected to one or more electrodes (5, 13 or 14) which are produced exactly according to the shape of the blade surface to be machined or according to sections of this shape; these electrodes are immersed in the fluid, in the course of which they are positioned opposite the blade surface to be machined; then electric current is passed into the electrode(s) in order to produce sparks via the dielectric fluid, by means of which sparks the blade surface is precision-machined by spark erosion. The invention can be applied to all types of turbine rotors. <IMAGE>

Description

The front Liegende 'invention "be'tri fi t a processing method that is applied in particular for the turbine impeller blades and the means and the machine for the application of the method.

The subject of the invention is in particular the technical area to be assigned to the electromechanical machining process.

The turbine runners of mainly petrol turbines must be off machining work coming from the foundry, especially in Area of the impeller blades on the inner surfaces or pressure surfaces on the one hand and on the outer surfaces or suction surfaces, on the other hand, in order to adapt them to the hydraulic profile that is required depending on the properties of the system.

Since there is only a limited number of turbine runners on the French market is produced, the processing is carried out by hand using portable grinding disks by specialists after shaping templates, which are carried out according to the Acceptance of the impeller.

To do this, the impeller must be attached to a clamping device, to be accessible from all sides; the grinding is carried out shovel by shovel, which takes a lot of time, since between two successive ones Shoveling is limited space and the use of tightly dimensioned grinding wheels makes necessary; In addition, the operator proceeds with movements that are not very extensive, which means that the work output is only very mediocre. It is estimated that it takes about a year to work a turbine runner to be processed with twenty pairs of blades.

moreover, the worker must do this long and difficult work Equip with protective clothing, which is very uncomfortable.

The precision of the work is largely dependent on the skill of the Worker dependent, and the shapes of the blades are never exactly the same, this applies in particular to the blade pairs, which are therefore not symmetrical and affect the hydraulic work performance.

The method according to the invention remedies these disadvantages and brings numerous advantages, namely in that it is very economical Way enables high precision hydraulic shovel profiles to be made, whereby the shapes are exactly repeated on all blades, whereby a perfect symmetry of the blade pair shapes is achieved, as well as a Profi L, which comes very close to the theoretical profile; this results in a very good working performance of the turbine.

In addition, the method and the machine enable a considerable improvement of working conditions in that the unpleasant work of professional Grinder is converted into an operation, the grinder only has to carry out the necessary steps regularly in order to get from moving from one shovel to another, giving him time to do other work to execute. Also worth mentioning is the considerably shorter processing time compared to grinding, which therefore has many advantages (reduction in Manufacturing costs, shorter manufacturing times, etc ...). So will for example a turbine runner with twenty pairs of blades with the machine according to the invention processed in about a month.

The inventive method is characterized in that the impeller partially immersed in a dielectric liquid; above this Liquid is at least one device for generating and controlling electrical Current attached, which is connected to an electrode that was made exactly to the shape of the blade surface to be machined and which is immersed in the liquid; the electrode is opposite to the one machined blade surface and the electric current is in passed the electrode so that sparks generated across the dielectric fluid which are used to machine the blade surface by electrical discharge machining.

The machine for applying the method is characterized by that, starting from a solid, amply sized main frame, it is a container includes, which is filled with dielectric fluid and with ductile and is equipped with self-centering means for freely rotating attachment of the turbine runner to be machined; at least one head for generation and control electric power is attached to the frame so that it is adjustable; he is Equipped with an electrode that exactly follows the profile of the pressure or suction surface the blade is formed and sparks through the insulating dielectric Liquid generated to precisely machine the blades using electrical discharge machining.

These properties as well as numerous others proceed from the following Description.

However, by no means restrictive definition of the subject the attached drawings serve the invention:

Fig. 1 is a schematic longitudinal section showing a manufacturing example represents the machine according to the invention.

FIG. 2 is a top view according to FIG. 1

3 is a sectional drawing in side view along line 3-3 of FIG Fig. 1.

FIG. 4 is a sectional side view taken along line 4-4 of FIG Fig. 1.

Figures 5, 6 and 7 are sectional drawings of the blades and the electrode, each the processing of the printing areas, the limited processing of the suction surfaces and the complete processing of the suction surfaces.

FIGS. 8 to 11 are schematic representations of various design variants the machine according to the invention.

In order to present the subject matter of the invention more concretely, the following now follows Description in non-limiting design options based on the drawings are shown.

The machine comprises a main frame (1), which by means of columns (1a) a generously sized container (2) to accommodate Pelton runners (R) different diameters are used.

For this purpose, the container is equipped with means on the upper part of its walls, which are shown schematically in the drawings under the designation (3) are and include a self-centering organ and a diametrically expandable organ, which consists, for example, of a chuck with wedges, which be pushed by a nut on the axis of rotation and act against spacers, depending on the impeller diameters, in particular the diameters of their Hubs, are interchangeable.

In the container (2) flows in a steady or pulsating manner in a closed manner Circuit, starting from a container (4) and a pump (5), a dielectric Liquid (FD) that covers the wheel by, for example, more than half and over which sparks develop, which are generated by an electrode (6) which has been manufactured precisely to the desired profile around the to correspond to the hydraulic characteristics of the system, or by means of several electrodes, each of which work on a specific area of the shovel.

The electrode is attached to the end of an offset arm (7) which is connected to a head (S) for generating and controlling the electrical current is; the head is carried by a carriage (9) which itself slides on the frame is mounted.

A manufacturing option is shown in FIGS. 1 to 4 merely as an example shown for the assembly of the head (8).

It can be seen from the fact that the head has a socket at its rear (8a) is provided, which cooperates slidingly with a cross member (9a) of the carriage, at the ends of which angle brackets (9b) are attached, which are used to accommodate a device made of rollers or roller bearings, which with respect to running rails be guided on the frame.

For example, and according to FIG. 4, the angle brackets are front and rear provided with blocks <9c) on which freely rotating roller bearings (9d) in inclined Arrangement are mounted and run on rods (10) on the frame or on the side are attached to the container. The angle brackets (9b) carry a fork in the middle (9e) which engages over the rods (10) and at its free ends carries rolling bearings (9f) which rotate freely and which are in contact with the lower part of the rods.

The carriage (9) is longitudinally guided by any known means, for example by a cylinder (11) connected to an element of the frame or another fixed part and its rod as a fork (11a) is formed so that they are connected to one arm of the sleeve (8a) can. Thus, the electrode (6) can be inserted between two pairs of blades or be pulled out while waiting.

The impeller (R) comprises, in a known manner, a certain number of pairs of blades (R-j), the blades of each pair are separated by a central ridge (R £) separated from each other, which is used outside to divide the water jet, which is injected at one or more points on the impeller circumference, into equal parts share.

In the example shown, each Blade uses an electrode "which has the shape of the blade interior and is moved transversely in order to process the other blade of the pair (Fig. 5). For this purpose, in addition to the longitudinal movements of the head, transverse movements must be possible, which can be achieved by any means, for example by a cylinder (12) which is firmly connected to the frame and its rod for example connected to the cylinder (11) which is slidably mounted on the frame is (Fig. 2). Likewise, only a single electrode (6) can be used at the same time Machining the pressure surfaces of an impeller blade pair can be used (Fig. 6).

Of course, the suction surfaces can be machined in the same way every shovel to be carried out.

For example, as shown in FIG. 6, an electrode (13) can be installed

that is the shape of the area (R3) between the blades where the water jet is to be divided, or one can use an electrode (14) the shape of the entire suction surface of a blade can be used (Fig. 7), which is turned over in order to process the other suction surface of the pair of blades (or a symmetrical electrode (14) is used).

The arrangement of the electrodes around the impeller can depend on their number and their mode of action can be designed differently. For example :

- A single electrode holding head (8) for processing the suction surface and the printing surface with exchangeable electrodes (Fig. 1);

- two electrode holding heads, for the respective processing of the printing resp. the suction surfaces with corresponding electrodes; here are these heads either opposite on the frame (Fig. S) or on the same side of the wheel;

- three electrode holding heads, one of which is used to process the suction surface and two for processing the printing surface (Fig. 9);

- four pairs of opposing electrode holding heads, two for the pressure surface, two for the suction surface (Fig. 10).

Scanning electrodes (16) (thus electrodes with point effect) can also be used. be used; in this case the impeller can be mounted on a vertical axis (Fig. 11).

The electrodes can be used in any desired manner, in particular by copying be made on a copier.

The impeller (R) can be turned by hand by a pair of blades to move on to the other; an angle circuit is used here, for example by means of an adjustable rod (15) which is inserted between two pairs of blades (Fig. 2); The impeller can also be connected to a step control or a similar controller can be connected.

In the following, the method according to the invention for processing will now be used described, this with reference to FIGS. 1 to 7.

The turbine wheel to be processed is in or in the means (3) for self-centering freely rotating assembly positioned; the stretchers are adjusted depending on the diameter of the turbine hub, then the pump (5) is switched on to ensure the steady or pulsating flow of the dielectric To enable liquid (FD), which is located in the container (2) in which the impeller is partially submerged.

The electrode (6, 13

or 14) was made according to the shape characteristics of this surface on a copier manufactured and mounted on the end of an offset arm (7) which is connected to the Head (8) for generating and controlling electrical current is firmly connected; the unit carried by the carriage (9) is by means of a cylinder (11) or a similar device pushed so that the electrode exactly opposite the the surface to be machined is positioned; before that the transverse adjustment was made if necessary the electrode position by means of the cylinder C12) or a similar one Device made.

If the rotary motion of the turbine impeller is not controlled by a suitable transmission system switched, the impeller is in the desired position held, for example by the adjustable rod (15), which is inserted between two pairs of blades, then the current is passed into the electrode, which removes the necessary material through electrical discharge machining.

After finishing the processing of the blade, the slide (9) is again moved backwards to put the electrode on hold, then the head / electrode unit shifted transversely when the other blade is working or the wheel is cleared and turned to the next pair of blades to bring it into the machining position, or the electrode is changed.

The procedure is the same for all blades; If the machine has only one electrode holding head, then the electrode (s) which have processed the pressure surfaces are exchanged so that the electrode (13, £ 14) can be attached for processing the suction surfaces; then proceed in the same way as described above, changing the settings.

The advantages are clear from the description to underline is still :

- The repeatability of the shapes on all blades with a profile that comes very close to the required theoretical Profi I, this with perfect Symmetry between the pairs of blades and excellent precision.

- The ability to manufacture the electrodes prior to manufacture of the impeller; this allows in connection with the extensive shortening the processing time, the production times are shortened.

- The significant improvement in working conditions and the simplification the work, whereby the full-time skilled workers through Hi Ifs-

0._

Forces without special training can be replaced, the latter in parallel can carry out other work for this work between the individual operations.

- The horizontal work of several electrodes on the blades for the production of the pressure and suction surfaces enables the very precise display these fluctuations and the control of the depth feeds.

Besides, it is due to the size of the container and the mechanism To control the electrode trolleys, it is possible to have slides on both sides of the impeller that carry electrode blocks, depending on how the assembly devices from the previous descriptions are arranged. Thus can machined the pressure surfaces of a blade or a pair of blades at the same time and on the opposite side of the impellers the suction surfaces of a blade or a pair of blades; thus the working time is shortened considerably.

The invention is in no way restricted to the methods of application nor on the design options for the various parts that are specifically described here; on the contrary, it includes all variants a.

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Claims (1)

PATENT CLAIMS _Λ —1- Machine for applying an electrical discharge machining process of turbine runners, the machine comprising a container connected to a dielectric liquid is filled, as well as a head for generation and control electric current, which is attached to the machine frame, and an electrode carrier, which is worked exactly according to the profile of the pressure surface of the blades; the turbine wheel is attached to the container; between the There is a device for carrying out the impeller and the electrodes of back and forth movements to the successive machining of the blades to ensure; the machine is characterized by the fact that the Turbine impeller (R) freely rotating vertically in a fixed position is attached to the machine frame, this on a horizontal axis, which is equipped with expandable and self-centering devices (3), which in the The inside of the tank is fixed and interchangeable, so that it fits to all turbine wheel hubs adjust. The machine comprises at least one unit consisting of heads (8) for generating and controlling electrical current from at least a carriage C9) is carried on at least one side of the frame is moved rolling with respect to the impeller and the frame, the heads are with a means of any kind for controlling longitudinal and transverse movements, such as for example cylinders CT-1-12) or similar organs connected; the heads can- «; here horizontally one after the other or at the same time the pressure surfaces of the blades | or process pairs of blades, this also in the impeller opposite ~ * Position on the suction surfaces of the blades or pairs of blades this same Impeller. - 2 - Machine according to claim 1, characterized in that the stretchable and self-centering means (3) are of the chuck type with wedges that are driven by a Nut are pushed on the axis of rotation and act against spacers that depending on the diameter of the running wheels, especially their hubs, with each other are interchangeable. - 3 - Machine according to claim 1, characterized in that the units consist from one or more heads (8) for generating and controlling electrical Stroms are carried by at least one carriage (9), each carriage consists of a traverse C9a) on which the head can slide and an angle bracket (9b) at the ends, which are used to accommodate a device made of rollers or roller bearings are used around rods (10) or rails that are attached to the frame or are firmly connected to the container, grab. - ^ ~ k machine According to claim 3, characterized in that the angle supports (9b) are provided with blocks (9c) at the front and rear, on which freely rotating roller bearings (9d) are inclined so that they can run on the rods (10) ; in the middle, the angle brackets are provided with a fork part (9e) which grips over the rods and whose free ends accommodate rolling bearings (9f) that are in contact with the lower part of the rods (10). -5- machine according to claim 1, characterized in that it has a single Head (8) for generating and controlling electrical current, which with Interchangeable electrodes are fitted to either the pressure surfaces to process the blades or the suction surfaces partially or entirely., -6- Machine according to claim 1 characterized in that it has several heads (8) for generating and controlling electrical power, wherein one or more Heads with electrodes for processing the printing surfaces, and one or more Heads are provided with electrodes for processing the suction surfaces. -7- machine according to claim 1, characterized in that the electrode (6) is accurate made according to the shapes of the pressure or suction surfaces of a single blade is, the processing of the other blade of the blade pair by transverse movements the head or heads for generating and controlling electrical power takes place. -8- machine according to claim 1, characterized in that a single Electrode (6) is made exactly according to the shapes of the undersides of a pair of blades. -9- Machine according to claim 1, characterized in that a single electrode (13) is made exactly according to the shapes of the central area (R3) of the suction surfaces of a pair of blades. -10- machine according to claim 1, characterized in that an electrode (14) is made exactly according to the shapes of the suction surface of a blade, the processing of the other blade of the blade pair by transverse movements of the or the heads for generating and controlling electric power and reversing the electrode or its support arm takes place. -11- Machine according to claim 1, characterized in that the turbine runner (R) after machining each pair of paddle wheels by hand and rotating in the desired position in relation to the electrode (s) by any means Kind to the circuit is held, for example by a controllable Rod (15) which is inserted between two pairs of blades. -12- Machine according to claim 1, characterized in that the turbine runner (R) freely rotating on a vertical axis via stretchable and self-centering Means is mounted, while the electrode (s) (16) for processing scanning electrodes, That means. Electrodes with a point effect, are.