EP0659523B1 - Apparatus for sandblasting surfaces, which are not directly accessible - Google Patents

Description

Field of the invention

The invention relates to treatment mechanical by blasting surfaces with difficulty accessible, for example internal cavities of a container or relatively shaped interior object complex. The invention applies more particularly to the final treatment of surfaces of the interior of a turbojet rotor.

Prior art and problem posed

In the context of manufacturing turbojet engines for aircraft, it is necessary to perform a shot peening on the inner surfaces of the rotor. Such treatment of surfaces helps strengthen mechanical capabilities and protection of the surfaces in question.

Shot blasting consists of projecting very high speed metal balls with a diameter of in the range of 0.2 to 0.6 mm. Such hammering allows to obtain the expected surface treatment.

The rotor of a turbojet engine has inside a large number of radial grooves, called stiffeners which form a large number of annular internal cavities that it is also necessary to blast. The difficulty of setting work of this operation forced the builders to turbomachines to design such rotors in several parts, so that you can have access to the surfaces internal to be treated by shot blasting. It follows a lack of structural homogeneity of the rotor.

The main object of the invention is to allow the construction of a turbomachine rotor by one piece while allowing the shot blasting of all internal surfaces to be treated by this process.

The shot blasting technique consists of project metal balls at very high speed by means of one or more compressed air sources at high pressure. The balls are thus transported in pipes leading to a terminal nozzle of projection. It is easy to understand that the slightest change of direction along the flow path high pressure propelled balls in the pipeline constitutes a significant pressure drop and power. The performance of the installation of shot peening is therefore dependent on this type of pitfall. However, the internal cavities of a turbomachine rotor do not are not accessible via a straight pipe. In indeed, they are not visible. They don't are accessible only through the central rotor channel on which each of these cavities opens. In others terms, the internal cavities of a turbomachine rotor are practically not accessible to shot blasting of sufficient power.

• un réservoir ou des moyens d'alimentation en grenaille ;
• des moyens de propulsion sous pression de cette grenaille, par exemple de l'air comprimé ;
• une ou plusieurs canalisations de grenaillage pour amener la grenaille sous pression vers une buse de projection ; et
• la buse de projection en question placée à l'extrémité de celle-ci.

On the other hand, an overpressure shot blasting installation includes among others:

• a tank or means for supplying shot;
• means for propelling this shot under pressure, for example compressed air;
• one or more shot blasting pipes for bringing the shot under pressure to a spray nozzle; and
• the projection nozzle in question placed at the end thereof.

The shot blasting line (s) should therefore avoid making changes brutal management. It is the same for the nozzle of projection that we may have to predict with a deflection surface, called projection anvil, depending on the position and orientation of the surfaces to treat.

Summary of the invention

• une canalisation d'alimentation en grenaille ;
• des moyens de propulsion sous haute pression d'air comprimé de la grenaille connectés à la sortie de la canalisation d'alimentation ;
• au moins une canalisation de grenaillage pour amener la grenaille sous pression près des surfaces à grenailler et connectées au moyen de propulsion ; et
• une buse de projection placée à l'extrémité de la canalisation de grenaillage.

The main object of the invention is a shot blasting device by projection of shot under pressure from surfaces not accessible by a straight pipe and requiring a sudden change of direction for the flow of shot, the device comprising:

• a supply line for pellets;
• means for propelling compressed air under high pressure of the shot connected to the outlet of the supply pipe;
• at least one shot-blasting pipe for bringing the shot under pressure near the surfaces to be shot-blasted and connected by means of propulsion; and
• a projection nozzle placed at the end of the shot blasting pipe.

• la canalisation de grenaillage est rectiligne ;
• les moyens de propulsion comprennent deux canalisations d'air comprimé à haute pression débouchant de part et d'autre d'un coude qui reçoit à son entrée la canalisation d'alimentation, le changement brutal de direction du flux de grenaille étant assuré par ce coude avant la connexion avec les Canalisations d'air comprimé, de sorte que l'énergie de propulsion n'est communiquée à la grenaille qu'à l'entrée de la canalisation rectiligne de grenaillage débouchant sur la buse de projection, la fixation de la canalisation de grenaillage à la sortie des moyens de propulsion est obtenue par un manchon monté tournant dans un support des moyens de propulsion, des moyens d'entraínement en rotation étant utilisés pour faire tourner le manchon autour d'un axe de rotation coaxial avec celui de la canalisation de grenaillage, ces moyens d'entraínement en rotation du manchon comprenant une turbine à ailettes d'axe vertical de rotation et fixée sur le manchon et une troisième canalisation d'air comprimé à haute pression débouchant tangentiellement par rapport à l'axe de rotation de la turbine, en regard des ailettes de celle-ci pour faire tourner la canalisation de grenaillage et la buse de projection dans le sens de rotation opposé au sens de fixation du manchon.

According to the invention, in such a device

• the shot blasting pipe is straight;
• the propulsion means comprise two pipes of compressed air at high pressure emerging on either side of an elbow which receives at its inlet the supply line, the abrupt change of direction of the flow of shot being ensured by this elbow before connection with the compressed air lines, so that the propelling energy is communicated to the shot only at the entrance to the straight shot-blasting pipe leading to the projection nozzle, the fixing of the pipe shot peening at the outlet of the propulsion means is obtained by a sleeve mounted rotating in a support of the propulsion means, rotational drive means being used to rotate the sleeve around an axis of rotation coaxial with that of the shot blasting pipe, these means for driving the sleeve in rotation comprising a turbine with fins with a vertical axis of rotation and fixed to the sleeve and a third ca nalisation of compressed air at high pressure opening tangentially with respect to the axis of rotation of the turbine, opposite the fins thereof to rotate the blasting pipe and the spray nozzle in the direction of rotation opposite to the direction sleeve fixing.

In order to facilitate the mounting of the device, the fixing of the shot blasting pipe at the outlet of means of propulsion is obtained on the sleeve by a lockable bayonet mount and unlockable, to allow rapid disassembly of this pipeline.

The nozzle is temporarily fixed by screwing, to can be changed at will depending on the orientation surfaces to be shot blasted.

The device can advantageously be supplemented by a pressure screw to slow down or block rotation of the turbine. Preferably, the first two and the third compressed air line are kept substantially parallel until the means propulsion by means of at least one rigid column.

In the context of the application of such device for blasting the internal cavities of a large and bulky piece such as a rotor turbojet engine, the device according to the invention comprises a foot fixed on a displacement axis integral with a shot blasting machine on the horizontal turntable which the workpiece is fixed so that the shot blasting pipe is located horizontally introduced into an internal toric space of the rotor shot blasting machine.

List of Figures

• figure 1, en coupe frontale, le dispositif selon l'invention installé sur une grenailleuse pour le grenaillage d'un rotor de turboréacteur ;
• figure 2, en coupe, l'utilisation de plusieurs buses différentes avec le dispositif selon l'invention dont l'application est représentée à la figure 1 ;
• figure 3, en coupe, les moyens de propulsion du dispositif selon l'invention ;
• figure 4, en coupe partielle latérale, un détail des moyens de propulsion du dispositif selon l'invention ; et
• figure 5, en vue de dessus, les moyens d'entraínement en rotation dans le dispositif selon l'invention.

The invention and its various technical characteristics will be better understood on reading the following description, appended to a few figures representing respectively:

• Figure 1, in front section, the device according to the invention installed on a shot blasting machine for the blasting of a turbojet rotor;
• Figure 2, in section, the use of several different nozzles with the device according to the invention whose application is shown in Figure 1;
• Figure 3, in section, the propulsion means of the device according to the invention;
• Figure 4, in partial side section, a detail of the propulsion means of the device according to the invention; and
• Figure 5, in top view, the rotary drive means in the device according to the invention.

Detailed description of a realization of the invention

Figure 1 shows a rotor 10 of turbojet engine mounted on the horizontal turntable 2 a shot blasting machine 1. This rotor 10 is therefore driven by a rotational movement around a vertical axis 3 of the shot blasting machine in order to subject all internal surfaces of rotor 10 the treatment of shot blasting. Indeed, one distinguishes, on this figure 1, radial ribs 12 being positioned horizontally inside the rotor 10. They constitute stiffeners necessary for holding rotor mechanics 10. They define cavities interior 11 whose walls are therefore shot blasting. It can be seen that these cavities 11 are inaccessible directly and that any element in front working inside these must form a elbow to be able to access it.

To this end, the shot blasting device is equipped with a foot 4 supporting a horizontal bracket 5. This leg 4 is fixed on an axis of displacement 4A of the shot blasting machine 1. It allows to install the blasting system coaxially to the vertical axis 3 of the shot blasting machine 1.

The system according to the invention has been symbolized by a vertical column 6, fixed to the gallows 5 and inside which are introduced supply lines for the shot blasting. A first supply line in shot 7 is shown, as well as one of compressed air supply lines 8.

The operational part of the shot blasting according to the invention is symbolized by the lower end of column 6 supporting a blasting line 9 directed inwards of a cavity 11. It is understood that a rotation of the plate horizontal 2 carrying the rotor 10 relative to this shot blasting line 9 around the vertical axis 3 makes it possible to project inside a cavity 11 the shot blasting on 360 ° and thus treat such 11 complete annular cavity, one movement additional rotation of the pipeline from shot peening 9 around its horizontal axis being deputy, as detailed below.

Referring to Figure 2, which is a half-section of the rotor 10 of FIG. 1, different shot projection nozzles are used. In effect, taking into account the fact that each cavity 11 has a particular internal shape and made up of many surfaces, it is essential to use nozzles different projection. In the upper cavity 11, a first nozzle 20 is used to project the shot in the corners 13 distant from the axis 3. This first nozzle 20 has an anvil 20A equipped an inclined surface to deflect the shot of shot, in cooperation with an inclined pipe 20B of this same nozzle 20.

Similarly, in the second cavity 11, a second anvil 21 has been shown mounted on the shot blasting line 9 for treating corners close to the axis 3 of the cavity 11. For this, a anvil 21A, different from the first 20A, is used. Indeed, it has a convex surface allowing to push the shot towards the corners 14 by means of at least one inclined pipe 20B in direction of these corners 14 close to the axis 3. We specifies that the performance of such an anvil is lower than the previous one, given the fact of the sharp change in direction of the flow of shot, consuming a lot of energy.

In the third cavity 11, a third projection nozzle 22 has been shown with two side pipes 22B for projecting shot perpendicular to the side surfaces 15 of this cavity 11. It also uses an anvil 22A cooperating with the two lateral pipes 22B.

The extreme position of this third nozzle projection 22, symbolized by mixed lines, schematizes the use of pipelines shot peening 9 of different lengths to allow the projection of shot over the entire internal surface side 15 of the cavities 11.

The lower cavity 11 is shown with a 9A shot blasting pipe terminated by a nozzle-shaped part 9B allowing projection without deviation of the flow of shot. It allows the treatment of the extreme surface 16 of the cavity 11.

The projection nozzles 20, 21, 22 are temporarily mounted by screwing around the shot blasting pipe 9. This fixing can be protected by a sleeve 23.

Referring to Figure 3, the means of shot propulsion consist of a device which propels it in one direction oriented coaxially to that of the interior of the shot blasting line 9.

Indeed, the shot is brought by a supply line 7 shown vertical and coaxial with the vertical axis 3 of the plate 2 of the shot blasting machine 1 of figure 1. It must then be projected horizontally from Figure 3. It therefore undergoes a change of direction which is located in a bend 24 inside a body 25.

One of the two supply lines in compressed air 8, intended for propelling the shot, is shown on the right of the figure. It is brought parallel to the pipeline feed with shot 7, but ends with a 8A elbow opening at the elbow 24 of the body 25, in the extension of the internal pipe 26 placed at the outlet of the elbow 24.

As a result, the compressed air projects the shot descending from the supply line 7 by elbow 24, in the direction of the pipe shot blasting 9, and this at high speed. Of this way, the energy communicated by the gas under high pressure is entirely with shot, once it crossed the change of direction constituted mainly through the elbow 24 of the body 25. This energy is therefore fully communicated to the shot entering the shot-blasting line 9 terminated by the projection nozzle.

The arrival of propelled compressed air at the exit from the elbow 24 is also explained by Figure 4 showing in cross section these bodies. Two compressed air supply lines 8 high pressure were represented. Their journey is parallel to column 6 of Figure 3. They are join inside the support 25 at the out of the elbow 24. The shot is therefore taken at the times from below and on each side by the energy of propulsion of compressed air at high pressure. She is thus sent in the internal pipe 26 of the sleeve 27, then in the blasting pipe 9.

The shot blasting line 9 is fixed on the body 25 by means of a sleeve 27. This fixing is preferably carried out by a bayonet system diagrammed by two nipples 28 fixed in this sleeve 27 and protruding in a groove 29 of line 9. In other words, the fixing the shot blasting pipe 9 requires the introduction of two grooves 29 each around a nipple 28 and the rotation of the pipe of shot peening 9 around its vertical axis until set in abutment of the assembly in a final position of fixation.

Thus, the shot blasting line 9 is assembled and disassembled quickly and easily. This allows a quick change of shot blasting lines 9 for using shot blasting pipes of different lengths. Indeed, as illustrated in FIG. 2, the cavities 11 are relatively wide radially and require several radial positions of the projection nozzles, therefore several shot blasting pipes.

As shown in Figure 3, the sleeve 27 is rotatably mounted on the support 25 by means of roller bearings 30. As a result, this pipe shot peening 9 is thus rotatably mounted. In as a result, all projection nozzles can eject the shot in all directions around of the horizontal axis 33 of the pipeline of shot blasting 9.

The rotational drive of the entire sleeve 27-shot blasting line 9-nozzle projection can be done by means of a third additional compressed pipe 31. The end output 31A of the latter is then positioned opposite the fins 32 of a turbine secured to the sleeve 27.

Figure 5 makes it easier to explain these means for rotating the pipe of shot peening 9. Indeed, we find in this figure 5 the fins 32 of the turbine and the end 31A of the third compressed air line 31. We have also shown, for information only, the two first compressed air lines 8 bringing the shot propelling power.

The output end 31A of the third compressed air line 31 is offset from to the axis of symmetry of the system and at the same time by relative to the axis of rotation 33 of the turbine. We notice that this is also the axis of rotation of the shot blasting line 9 and sleeve 27 of the figure 3. It should also be noted that the meaning of turbine rotation is opposite to the mounting direction of the shot-blasting pipe 9 in the sleeve 27. This avoids unexpected dismantling of the shot blasting lines 9 and ensuring their stay in this position.

In Figure 5 has also been shown column 6 used to maintain the pipes 8, 31.

Returning to Figure 3, a screw pressure 34 can be used to act by screwing on the speed of rotation of the turbine. Indeed, this can be caused to rub against a surface radial 35 of the turbine. It is thus possible to block the rotation of the sleeve 27, in order to proceed with the assembly or disassembly of a pipeline shot blasting. It is also possible to use this adjusting screw 34 to vary the speed of turbine rotation.

Installation required for the application of such a system preferably requires the use an additional air supply to blow the shot which accumulates inside the cavities treat. It is reported that it is also possible to vacuum it to proceed with this evacuation.

The shot blasting treatment of all inner surfaces of a turbojet rotor made in one piece is thus possible thanks to the use of a rotary table blaster horizontal and of the device according to the invention. In in addition, a large number of pipe changes shot peening 9 of different lengths and the use of different projection nozzles are necessary for machining a single rotor. However, the time saved to perform this work, the quality of surface treatment obtained and the structure homogeneous mechanical rotor made in one piece, constitute considerable advantages by compared to previous methods of making such turbojet rotors.

Claims (6)

1. An apparatus for pressure shotblasting surfaces which are not directly accessible and require the shot flow to undergo an abrupt change of direction, comprising:

   a shot feed duct (7);

   high pressure compressed air propulsion means (8) secured to the exit of the shot feed duct (7);

   a shotblasting duct (9) to carry pressurised shot to surfaces (13, 14, 15, 16) to be shotblasted, said duct being secured to the propulsion means, and

   a blasting nozzle (20 ,21, 22) disposed at the end of the blasting duct (9);
   characterised in that

   the blasting duct (9) is straight;

   the propulsion means comprise first and second high pressure compressed air lines (8) opening into either side of a bend (24) at the exit thereof, the bend receiving at its entry the shot feed duct (7), the abrupt change of shot flow direction occurring in the bend (24) before the connection to the high pressure air feed lines (8) so that the propulsive energy is imparted to the shot only at the entry of the straight blasting duct (9) which opens directly into the blasting nozzle (20, 21, 22), and

   the blasting duct (9) is secured to the exit of the propulsion means by a sleeve (27) rotatably mounted in a support (25) of the propulsion means, rotation-producing means 31, 32) being used to rotate the sleeve (27) around a rotational axis (33) coaxial to the rotational axis of the blasting duct (9), the rotation-producing means comprising a turbine which has blades (32), has the axis (33) as its axis of rotation and is secured to the sleeve (27), and a third high pressure compressed air line (31) opening tangentially to the turbine rotational axis opposite the turbine blades (32) to rotate the blasting duct (9) and the blasting nozzle (20, 21,22) in a direction opposite to the direction of securing of the sleeve.
2. An apparatus according to claim 1, characterised in that the blasting duct (9) is connected to the exit of the propulsion means on the sleeve (27) by way of a bayonet connection (28, 29) which can be locked and unlocked to facilitate rapid release of the blasting duct (9).
3. An apparatus according to claim 1, characterised in that the blasting nozzle (20, 21, 22) is screwed to the blasting duct (9) releasably to facilitate rapid as-required changing.
4. An apparatus according to claim 1, characterised in that a pressure screw (34) is used to slow down or stop the turbine..
5. An apparatus according to claim 1, characterised in that the shot feed duct (7) and the first, second and third high pressure compressed air lines (8, 31) are maintained substantially parallel to one another as far as the propulsion means by means of a rigid column (6).
6. An apparatus according to claim 5, characterised in that it comprises a foot (4) secured to a shaft (4A) for moving a shotblasting device (1) having a horizontal rotating plate (2) carrying a turbojet engine rotor (10) to be shotblasted to ensure that the blasting duct (9) is disposed horizontally and can be introduced into an internal toroidal cavity (11) of the rotor (10).

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