EP0659523A1 - Apparatus for sandblasting surfaces, which are not directly accessible - Google Patents

Abstract

The device allows the shot-peening (sandblasting) of internal cavities which cannot be accessed by a direct pipe. It mainly comprises a shot-peening pipe (9) pointing in the direct shot-peening direction inside the cavities (11) to be shot-peened. This pipe (9) receives directly the shot and the highly compressed air (8) inside the rotor (10). The whole is introduced by means of a column (pillar) (6) mounted on a shot-peening machine (1) on the horizontal turntable (2) of which the component (10) is fastened. Application to the shot-peening of the internal surfaces of a turbojet engine rotor. <IMAGE>

Description

Field of the invention

The invention relates to the mechanical treatment by shot blasting of surfaces which are difficult to access, for example the internal cavities of a container or of an object with a relatively complex internal shape. 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 turns out to be necessary to make a shot peening on the internal surfaces of the rotor. Such surface treatment makes it possible to strengthen the mechanical and protective capacities of the surfaces in question.

Shot peening consists in projecting metal balls with a diameter of the order of 0.2 to 0.6 mm at very high speed. Such hammering provides the expected surface treatment.

The rotor of a turbojet engine has a large number of radial grooves inside, called stiffeners which form a large number of annular internal cavities which it is also necessary to blast. The difficulty in implementing this operation forced the manufacturers of turbomachinery to design such rotors in several parts, so as to be able to have access to the internal surfaces to be treated by shot blasting. This results in a lack of structural homogeneity of the rotor.

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

The shot blasting technique consists of projecting metal balls at very high speed using one or more sources of high pressure compressed air. The balls are thus conveyed in pipes leading to a terminal projection nozzle. It is easy to understand that the slightest change in direction along the flow path of the high-pressure propelled balls in the pipeline constitutes a significant loss of load and power. The performance of the shot blasting installation is therefore dependent on this type of pitfall. However, the internal cavities of a turbomachine rotor are not accessible by a straight pipe. In fact, they are not visible. They are only accessible through the central channel of the rotor on which each of these cavities opens. In other words, the internal cavities of a turbomachine rotor are practically not accessible to a 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 pipe (s) must therefore avoid sudden changes in direction. It is the same for the projection nozzle that may be required to provide with a deflection surface, called projection anvil, depending on the position and orientation of the surfaces to be treated.

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.
  Selon invention :
• 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'entraînement 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'entraînement 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 dispositif à baïonnette.

The main object of the invention is a shot blasting device by spraying shot under pressure from surfaces not accessible by a straight pipe and requiring a sudden change of direction for the shot flow, 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.
  According to invention:
• 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 the supply line at its entry, the abrupt change of direction of the flow of shot being ensured by this elbow before connecting with 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, fixing the shot-blasting pipe to the outlet propulsion means is obtained by a sleeve mounted rotating in a support of the propulsion means, rotation 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 having a vertical axis of rotation and fixed to the sleeve and a third high-pressure compressed air pipe opening tangentially with respect to the axis of rotation of the turbine, in look of the fins thereof to rotate the blasting pipe and the projection nozzle in the direction of rotation opposite to the direction of attachment of the device to bayonet.

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

The nozzle is temporarily fixed by screwing, so that it can be changed at will according to the orientation of the surfaces to be shot blasted.

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

In the context of the application of such a device to peening the internal cavities of an imposing and bulky part such as a turbojet rotor, the device according to the invention comprises a foot fixed on an axis of displacement integral with a shot blasting machine on the horizontal rotary plate from which the piece to be shot blasted is fixed so that the shot blasting pipe is horizontally introduced into an internal toric space of the turbomachine rotor to be shot blasted.

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'entraînement 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 rotational drive means in the device according to the invention.

Detailed description of an embodiment of the invention

FIG. 1 shows a rotor 10 of a turbojet engine mounted on the horizontal rotary plate 2 of a shot blasting machine 1. This rotor 10 is therefore driven in a rotational movement around a vertical axis 3 of the shot blasting machine in order to subject it to all the internal surfaces of the rotor 10 the shot blasting treatment. In fact, in this FIG. 1, there are radial ribs 12 which are positioned horizontally inside the rotor 10. They constitute stiffeners necessary for the mechanical strength of the rotor 10. They delimit interior cavities 11 whose walls are so to blast. It can be seen that these cavities 11 are inaccessible directly and that any element having to work inside them must form a bend in order to have access to them.

To this end, the shot blasting device according to the invention is equipped with a foot 4 supporting a horizontal bracket 5. This foot 4 is fixed on a displacement axis 4A of the shot blasting machine 1. It makes it possible to install the shot blasting system coaxial with 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 bracket 5 and inside which are inserted supply pipes for the shot blasting device. A first shot supply line 7 is shown, as well as one of the compressed air supply pipes 8.

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

With reference to FIG. 2, which is a half-section of the rotor 10 of FIG. 1, different shot projection nozzles are used. In fact, taking into account the fact that each cavity 11 has a particular internal shape and made up of numerous surfaces, it proves essential to use different projection nozzles. In the upper cavity 11, a first nozzle 20 is used to project shot into the corners 13 distant from the axis 3. This first nozzle 20 has an anvil 20A equipped with an inclined surface for deflecting 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 peening pipe 9 to treat the close corners of the axis 3 of the cavity 11. For this, an anvil 21A, different from the first 20A , is used. Indeed, it has a convex surface allowing the shot to be pushed back towards the corners 14 by means of at least one inclined pipe 20B in the direction of these corners 14 close to the axis 3. It is specified that the efficiency of such an anvil is lower than that of the previous one, taking into account the fact of the sharp accentuated change of direction of the flow of shot, consuming moreover a great energy.

In the third cavity 11, a third projection nozzle 22 has been shown with two lateral pipes 22B for projecting shot perpendicular to the lateral 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 projection nozzle 22, symbolized by mixed lines, shows diagrammatically the use of shot-blasting pipes 9 of different lengths to allow shot projection onto the entire lateral internal surface 15 of the cavities 11.

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

With reference to FIG. 3, the means for propelling the shot consist of a device which propels it in a direction oriented coaxially to that of the interior of the shot blasting pipe 9.

Indeed, the shot is brought by a supply pipe 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 relative to Figure 3. It consequently undergoes a change of direction which is situated in an elbow 24 inside a body 25.

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

Therefore, the compressed air projects the shot descending from the supply pipe 7 through the elbow 24, in the direction of the shot blasting pipe 9, and this at high speed. In this way, the energy communicated by the gas under high pressure is entirely communicated to the shot, once it has passed the change of direction constituted mainly by the elbow 24 of the body 25. This energy is therefore communicated completely to the shot entering the shot blasting pipe 9 terminated by the spray nozzle.

The arrival of the propulsion compressed air at the outlet of the elbow 24 is also explained by means of FIG. 4 showing in cross section these organs. Two high pressure compressed air supply lines 8 have been shown. Their path is parallel to column 6 of Figure 3. They meet inside the support 25 at the outlet of the elbow 24. The shot is therefore taken both from below and on each side by l propulsion energy of compressed air at high pressure. It is thus sent to the internal pipe 26 of the sleeve 27, then to the shot blasting pipe 9.

The shot blasting pipe 9 is fixed to the body 25 by means of a sleeve 27. This fixing is preferably carried out by a bayonet system shown diagrammatically by two pins 28 fixed in this sleeve 27 and projecting into a groove 29 of the pipe 9. In other words, fixing the shot blasting pipe 9 requires the introduction of two grooves 29 each around a stud 28 and the rotation of the shot blasting pipe 9 around its vertical axis until the assembly is brought into abutment in a final fixing position.

Thus, the shot blasting pipe 9 is assembled and disassembled quickly and easily. This allows a quick change of shot blasting pipes 9 to use 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 spray nozzles, therefore several shot blasting pipes.

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

The rotational drive of the entire sleeve 27-shot blasting pipe 9-spray nozzle can be done by means of a third additional compressed pipe 31. The outlet end 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 shot blasting pipe 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. The first two compressed air lines 8 are also shown, by way of indication, bringing the propelling power to the shot.

The outlet end 31A of the third compressed air line 31 is offset relative to the axis of symmetry of the system and at the same time relative to the axis of rotation 33 of the turbine. It is noted that this is also the axis of rotation of the shot blasting pipe 9 and of the sleeve 27 of FIG. 3. It should also be noted that the direction of rotation of the turbine is opposite to the direction of mounting of the pipe of shot peening 9 in the sleeve 27. This prevents unexpected disassembly of the peening pipes 9 and ensures that they are kept in this position.

Also shown in FIG. 5 is the column 6 used to hold the supply lines 8, 31.

Returning to FIG. 3, a pressure screw 34 can be used to act by screwing on the speed of rotation of the turbine. Indeed, it can be caused to rub against a radial surface 35 of the turbine. It is thus possible to block the rotation of the sleeve 27, for the purpose of mounting or dismounting a blasting pipe. It is also possible to use this adjusting screw 34 to vary the speed of rotation of the turbine.

The installation necessary for the application of such a system preferably requires the use of an additional air supply to blow the shot which accumulates inside the cavities to treat. It is reported that it is also possible to vacuum it to carry out this evacuation.

The treatment by shot blasting of all the interior surfaces of a turbojet rotor made in one piece is thus possible thanks to the use of a shot blasting machine with a horizontal rotary plate and of the device according to the invention. In addition, a large number of changes in shot blasting pipes 9 of different lengths and the use of different spray nozzles are necessary for the machining of a single rotor. However, the time saved for carrying out this work, the quality of surface treatment obtained and the homogeneous mechanical structure of the rotor manufactured in one piece, constitute considerable advantages compared to the previous methods of manufacturing such rotors of turbojets.

Claims (6)

Shot blasting device by projection of pressure shot, surfaces not accessible by a straight pipe and requiring a sudden change of direction for the shot flow, comprising: - a supply line for pellets (7); - means for propelling compressed air under high pressure (8), fixed at the outlet of the supply pipe (7); - a shot blasting pipe (9) for bringing the shot blast under pressure to surfaces (13, 14, 15, 16) to be shot blasted, fixed to the propulsion means; and - a projection nozzle (20, 21, 22) placed at the end of the blasting pipe (9),
characterized in that: - the shot blasting pipe (9) is straight; - The propulsion means comprise two first high pressure compressed air pipes (8) opening on each side of an elbow (24), at the outlet thereof, the latter receiving at its inlet the supply pipe in shot (7), the sudden change of direction for the flow of shot taking place in the elbow (24) before connection to the high pressure compressed air supply lines (8), so that the propelling energy is communicated to the shot only at the entrance to the rectilinear shot-blasting pipe (9) leading directly to the projection nozzle (20, 21, 22), - the fixing of the blasting pipe (9) at the outlet of the propulsion means is obtained by a sleeve (27) mounted rotating in a support (25) of the propulsion means, of the rotation drive means (31, 32 ) being used to rotate the sleeve (27) about an axis of rotation (33) coaxial with that of the shot-blasting pipe (9), these means for driving the sleeve (27) in rotation comprising a fin turbine (32) with a vertical axis of rotation (33) and fixed on the sleeve (27) and a third high-pressure compressed air line (31) opening tangentially with respect to the axis of rotation of the turbine, opposite fins (32) thereof for rotating the blasting pipe (9) and the projection nozzle (20, 21, 22) in the direction of rotation opposite to the direction of attachment of the bayonet device. System according to claim 1, characterized in that the fixing of the blasting pipe (9) at the outlet of the propulsion means is obtained on a sleeve (27) by a bayonet fixing device (28, 29), lockable and unlockable, to allow rapid disassembly of this shot blasting pipe (9). Device according to claim 1, characterized in that the projection nozzle (20, 21, 22) is temporarily fixed by screwing on the blasting pipe (9) so that it can be changed easily and at will. Device according to claim 1, characterized in that a pressure screw (34) is used to slow down or block the rotation of the fin turbine (32). Device according to claim 1, characterized in that the supply line for shot (7), the first two and the third high pressure compressed air pipes (8, 31) are kept substantially parallel to the propulsion means by means of a rigid column (6). Device according to claim 5, characterized in that it comprises a foot (4) fixed on a displacement axis (4A) of a shot blasting machine (1) with a horizontal rotary plate (2) supporting a turbojet rotor (10) with shot blasting, so that the shot blasting pipe (9) lies horizontally and can be introduced into an internal toric cavity (11) of the rotor (10).

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