FR2978068A1 - INJECTION MOLDING DEVICE OF A TURBOMACHINE BLADE MODEL, AND METHOD OF MANUFACTURING THE DEVICE - Google Patents

Abstract

The device comprises a lower imprint block (18) and an upper imprint block (22) in which impressions are formed whose shape after superposition of the lower and upper imprint blocks coincides with a shape of a pattern of the blade to be molded, a lower flange (20), an upper flange (24), and a unit for fixing the lower and upper imprint blocks on the upper and lower flanges respectively. The flanges are moved with respect to each other in rotation around an articulation axis (16) between a molding position and a demolding position. The device comprises a lower imprint block (18) and an upper imprint block (22) in which impressions are formed whose shape after superposition of the lower and upper imprint blocks coincides with a shape of a pattern of the blade to be molded, a lower flange (20), an upper flange (24), and a unit for fixing the lower and upper imprint blocks on the upper and lower flanges respectively. The flanges are moved with respect to each other in rotation around an articulation axis (16) between a molding position in which the blocks are superimposed and a demolding position in which the blocks are mutually separated. The fixing unit comprises: a primary groove that is formed in the lower flange and in the upper and lower imprint blocks and extends along a direction parallel to the articulation axis; a first indexing wedge simultaneously located in the primary groove for positioning the upper and lower imprint blocks on the lower flange; a secondary groove that is formed in the flange and in the imprint blocks and extends along a direction perpendicular to the articulation axis; and a second indexing wedge simultaneously located in the secondary groove for positioning the upper and lower imprint blocks on the lower flange. The primary and secondary grooves comprise an orifice for receiving a fastening member. The first and second indexing wedges have a rectangular parallelepiped shape. Independent claims are included for: (1) a process for fabricating an imprint block for an injection molding device; and (2) a method for fabricating an injection molding device.

Description

TECHNICAL FIELD The present invention relates to the field of injection molding of blade wax models 10 of turbine engines for aircraft. It relates more particularly to an injection molding device of a turbomachine blade wax model, comprising at least one lower impression block and at least one upper impression block, in which are formed impressions whose shape after superposition of said The lower and upper impression blocks coincide with the shape of the blade model to be molded, as well as two flanges, respectively lower and upper, and means for fixing said fingerprint blocks respectively on said flanges, these flanges being displaceable relative to one another. the other rotating about an axis of articulation between a molding position in which said blocks are superimposed and a demolding position in which said blocks are mutually spaced apart. In molding devices of this type, the impression block must be positioned at a precise distance from the hinge axis. The invention also relates to a method of manufacturing such a device. BACKGROUND OF THE PRIOR ART In molding devices of known types, the fixing of an impression block on the associated sole is usually carried out by drilling holes. fastening in the sole then positioning the impression block on this sole by means of measuring and control tools such as comparators and wedges, and finally by drilling, in the impression block, fixing holes aligned with the holes of the sole. In general, some of the attachment holes of the soleplate are intended to each receive a fixing screw while others of these holes each receive a pin to facilitate the subsequent positioning of the impression block on the soleplate. The imprinted blocks are generally each formed of several block portions assembled to each other. In this case, it is generally the block portion incorporating the blade blade imprint, commonly called "blade block", which is positioned in the manner described above and in which the holes of the blade are drilled. fastening to the sole. However, the positioning mode of the impression blocks described above is tedious and complex to implement. SUMMARY OF THE INVENTION The object of the invention is in particular to provide a simple, economical and effective solution to this problem, making it possible to avoid at least in part the aforementioned drawbacks. The invention proposes for this purpose an injection molding device of a turbomachine blade wax model, comprising at least one lower impression block and at least one upper impression block, in which are formed impressions whose shape after superposition of said lower and upper impression blocks coincides with the shape of the blade template to be molded, as well as two flanges, respectively lower and upper, and means for fixing said imprinted blocks respectively on said flanges, these flanges being displaceable, one by relative to each other in rotation about an axis of articulation between a molding position in which said blocks are superimposed and a demolding position in which said blocks are mutually spaced apart. According to the invention, said means for fixing at least one of said impression blocks on the corresponding sole comprise a main groove formed in said soleplate and extending in a direction parallel to said articulation axis, as well as a main groove formed in said impression block, and at least one parallelepipedal indexing wedge which can be accommodated simultaneously in said grooves for positioning said impression block on said soleplate. The indexing wedge, also called bacon, is intended to be engaged in the main groove of the sole and is shaped so as to then project outward from the main groove beyond the sole surface. . The impression block can then be positioned on the soleplate by referencing the main groove of the impression block with the protruding portion of the indexing wedge, and then inserting this projection part of the indexing wedge into the main groove of the impression block. The flat faces of the indexing wedge make it particularly easy operation of positioning the impression block on the sole. This configuration with an indexing wedge independent of the sole and the impression block makes it possible to make this wedge in a material different from the material constituting this sole and this impression block. In particular, the wedge can be made of steel so that it can be ground for optimum dimensional accuracy, while the sole and the impression block can be made of aluminum for example. In addition, the spacing between the main groove of the soleplate and the aforementioned axis of articulation, measured on the surface of the soleplate, can be known precisely, so that the main groove of the impression block can serve as a reference for the machining of the whole of this imprint block. Indeed, by machining each portion of the cavity block relative to the main groove of this block, it can be obtained precise positioning of each portion of the cavity block relative to the aforementioned hinge axis.

Similarly, the respective main grooves of the impression block and the soleplate may serve as a reference for various operations relating to the impression block during the use of the device, for example to precisely position a core within the cavity. the footprint delimited by the imprint block. In a preferred embodiment of the invention, the main groove of the sole has a flank located at a distance from the aforementioned axis of articulation equal to 50% of the height of the blade model for which the device is designed. . The term "height of the blade model" is to be understood with reference to a blade according to this model mounted in a turbomachine, and corresponds to the radial distance separating the top of the blade from the axis of the turbomachine. In the preferred embodiment of the invention, the fixing means of the impression block on the corresponding sole further comprise a secondary groove formed in the soleplate and extending in a direction perpendicular to said axis of articulation, as well as a secondary groove formed in the impression block, and at least one parallelepipedal indexing wedge that can be simultaneously accommodated in said grooves for positioning the impression block on the soleplate. In this case, the main grooves and their associated indexing shim can be designed to ensure only the positioning of the impression block in a direction perpendicular to the aforementioned hinge axis 6, referred to as the longitudinal direction of the sole, the positioning of this block in the direction of the hinge axis, referred to as the transverse direction of the soleplate, can then be provided by the aforementioned secondary grooves and their associated indexing wedge. The fact that each groove ensures the positioning of the imprint block in one direction increases the dimensional tolerance of the grooves and the indexing wedges in the other direction. In addition, it is not necessary that the indexing wedge is precisely positioned along this other direction, so that the groove may be longer than the indexing wedge in this other direction. In the preferred embodiment of the invention, the cavity block comprises at least one receiving orifice of a fastener of this block on the sole, such as a screw. Furthermore, each of said grooves advantageously comprises at least one receiving orifice of a fixing member of said associated indexing wedge, such as a screw.

In the preferred embodiment of the invention, said wedges are substantially in the shape of a rectangular parallelepiped. In general, the main and secondary grooves are preferably elongated. The invention also relates to a method for manufacturing a cavity block for a device of the type described above, comprising successively the machining of a main groove of said impression block, then the machining of said impression of said impression block by reference to said main groove. The main groove forms a physical reference that is particularly easy to handle in machining tools, and also has the advantage of allowing the reception of an indexing wedge to allow easy positioning of the impression block on a corresponding sole as explained above. The invention also relates to a method of manufacturing a device of the type described above, comprising the manufacture of at least one impression block by means of the method of claim 6 as well as the machining of a main groove in a corresponding sole of said device.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of nonlimiting example and with reference to the appended drawings in which: FIG. 1 is a schematic perspective view of an injection molding device of a turbomachine blade wax model according to a preferred embodiment of the invention; 8

Figure 2 is a schematic perspective view of a lower part of the device of Figure 1; Figures 3 and 3bis are schematic perspective views of a sole of the lower part of the device of Figure 1; FIG. 4 is a schematic perspective view of an impression block portion, of the "pale block" type, of the lower part of the device of FIG. 1, showing the underside of this impression block portion; FIG. 5 is a schematic perspective view of the imprinted block portion of FIG. 4, showing the underside of this imprinted block portion, and illustrating the co-operation thereof with indexing wedges of this device. In all of these figures, identical references may designate identical or similar elements. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 represents a device 10 for the injection molding of a model of a turbomachine blade wax, for example for a helicopter, this device comprising two parts, lower 12 and upper 14 respectively, pivoting relative to each other about an axis of articulation 16. The lower portion 12 comprises a lower cavity block 18 and a lower sole 20 forming a support for this impression block 18. In a similar way, the upper portion 14 has an upper cavity block 22 and an upper flange 9 24 forming a support for the impression block 22. The flanges 20 and 24 are generally rectangular, flat and elongated. The lower sole 20 further comprises two lateral lugs 26 jointly forming a mounting yoke for the hinge axis 16, while the upper sole 24 has two lugs 28 for mounting on the aforementioned axis 16. The lower flanges 20 and upper 24 are furthermore equipped with handles 30, and with a device 32 for locking the device in its molding position shown in FIG. 1. The lower flange 20 also carries a release lever 34 whose function will appear more clearly in the following. As shown in Figure 2, the lower cavity block 18 is formed of several block portions assembled to each other. Starting from the lugs 26 and moving towards the opposite end of the device 10, a first block portion 36 is thus encountered, integrating an injection channel 38, a second block portion 40 incorporating a portion 42 of the imprint 43 intended to form the foot of the blade, referred to as "foot block" in the following, a third block portion 44 integrating the portion 46 of the imprint intended to form the blade of the blade, called "pale block" in following, then a fourth portion of block 48 commonly called "grain selector block".

This device 10 furthermore incorporates a molded vane model ejection system comprising a lamella-shaped ejector support 50 (FIGS. 3 and 3a) extending in a middle longitudinal groove 52 of the lower sole 20. and provided with a hinge lug 53 to the above-mentioned axis 16 (FIGS. 1 and 2), as well as two ejectors 54 and 56 (FIGS. 2 and 3a) extending upwards from the support 50. This system comprises also the demolding lever 34 above. When the lever 34 is actuated at the end of molding of a wax blade model, the support 50 pivots around the hinge axis 16 and thus causes the ejectors 54 and 56 to move upwards in accordance with a trajectory in an arc around the axis 16, so that these ejectors 54, 56 come push the molded wax blade model upwards, thus facilitating its demolding. As can be seen in FIGS. 3 and 3bis, the lower sole 20 further comprises two receiving housings 58 for the ears 26, as well as two grooves 60 and 62 of rectangular section and of elongate shape, one of which extends in parallel. to the median groove 52 above and constitutes a secondary groove in the terminology of the present invention, and the other 62 extends parallel to the hinge axis 16, and therefore perpendicular to the central groove 52, and constitutes a main groove in the terminology of the invention. The main groove 62 of the lower flange 20 has a flank 63 located at a distance d from the aforementioned hinge axis, measured on the upper surface of the flange 20. The projection 11 of the hinge pin on this surface of the sole 20 is symbolized by the line 16 '. In the embodiment described, the distance d is equal to 50% of the height of the blade model for which the device is designed. The aforementioned grooves 60 and 62 are intended for the positioning of the blade block 44 on the bottom flange 20. For this purpose, the device comprises indexing wedges 64 and 66 in the shape of a rectangular parallelepiped shaped so as to be housed substantially without transverse clearance in the grooves 60 and 62, and having a projecting upper part out of these grooves beyond the surface of the lower flange 20, this upper part being intended to engage in a corresponding groove formed in the blade block 44, as will become clearer in the following. By "transverse play", it is of course understood a game in the direction of smaller extent of the groove.

More specifically, the device comprises a single shim 64 disposed in the secondary groove 60, and two shims 66 arranged in the main groove 62 on either side of the secondary grooves 60 and median 52.

Each of the indexing shims 66 is arranged opposite a corresponding end of the main groove 62, possibly at a distance from this end. As can be seen in FIGS. 4 and 5, the blade unit 44 has two grooves 68 and 70 similar respectively to the grooves 60 and 62 and 12 respectively forming a secondary groove and a main groove, as well as a recess 72 allowing the passage of the support of ejectors 50 during its displacement following the actuation of the release lever 34. The blade unit 44 has a curved face 78 intended to delimit a portion of the cavity corresponding to the platform of the blade, this face coinciding in particularly with the aerodynamic outer surface of this platform, that is to say the surface intended to define a primary stream of turbomachine. FIG. 5 illustrates the indexing wedges 64 and 66 engaged in the corresponding grooves 68 and 70 of the blade block 44. This device allows easy positioning of the blade block 44 on the lower soleplate 20. In fact, after having inserted the wedges 64 and 66 in the corresponding grooves 60 and 62 of the lower sole 20, it is sufficient to bring the blade block 44 above these wedges 64, 66 and to engage the latter in the grooves 68 and 70 of the blade block by pushing this last in the direction of the sole 20, to obtain a correct positioning of the blade block on the sole 20.

The main groove 62 of the soleplate makes it possible in particular to ensure the positioning of the blade block 44 in the longitudinal direction of the lower soleplate 20, while the secondary groove 60 of the soleplate makes it possible to ensure the positioning of the blade block in the direction transverse lower sole 20. When the blade block 44 is in place on the lower sole 20, the fixing of this block 44 on this sole 20 can be operated, for example by means of screws passing through the sole 20 and engaged in orifices 80 of the blade block 44 (FIGS. 4 and 5). The shims 64 and 66 are advantageously fastened to the bottom flange 20, before any positioning operation of the blade block 44, by means of screws (not visible in the figures) passing through the orifices of the sole opening into the grooves 68 and 70. This fixing the shims on the sole is of course optional, and is essentially to facilitate the handling of the device during the positioning of the blade block 44 on the lower sole 20. Good accuracy in the positioning of the blade block 44 relative to the lower sole 20 is particularly sought after because the curved face 78 of the blade block 44 must be positioned at a precise distance from the hinge axis 16, this distance being equal to the radius of curvature of the curved face 78. use of a ejection-type ejection system as described above, wherein the rotation of the ejectors around the hinge axis soles 20 and 24 allow the ejectors to slide along the curved face 78 of the blade block without the risk of damaging it. As explained above, the blade block 44 can be made in a particularly simple manner, by first machining the main groove 70 of 14

this block, then using this groove as a reference for machining the entire block, including the footprint delimited by this block.

Claims (6)

REVENDICATIONS1. A device (10) for injection molding a turbomachine blade wax pattern, comprising at least one lower cavity block (18) and at least one upper cavity block (22), in which fingerprints are formed whose shape after superposition of said lower and upper impression blocks coincides with the shape of the blade template to be molded, and two flanges, respectively lower (20) and upper (24), and means for fixing said fingerprint blocks (18, 22) respectively on said flanges (20, 24), these flanges being movable relative to each other in rotation about an axis of articulation (16) between a molding position in which said blocks are superposed and a position of demolding in which said blocks are mutually spaced, characterized in that said means for fixing at least one (18, 44) of said imprinted blocks on the corresponding sole (20) comprise a main groove (6 2) formed in said soleplate (20) and extending in a direction parallel to said articulation axis (16), as well as a main groove (70) formed in said cavity block (18, 44), and at least one indexing wedge (66) parallelepipedally accommodable simultaneously in said grooves (62, 70) for positioning said impression block (18, 44) on said sole (20). 2. Device according to claim 1, characterized in that said fixing means of said cavity block (18, 44) on said corresponding sole (20) further comprises a secondary groove (60) formed in said sole and extending in a direction perpendicular to said hinge axis (16), and a secondary groove (68) formed in said cavity block (18, 44), and at least one parallelepipedal indexing wedge (64) that can be accommodated simultaneously in said grooves (60 , 68) for positioning said impression block on said sole. 3. Device according to claim 1 or 2, characterized in that each of said grooves comprises at least one receiving orifice of a fixing member of said associated indexing wedge. 4. Device according to any one of the preceding claims, characterized in that said wedges (64, 66) are substantially in the shape of a rectangular parallelepiped. 5. A method of manufacturing a cavity block for a device according to any one of claims 1 to 4, characterized in that it comprises successively the machining of a main groove of said impression block, then the machining of said imprint of said block imprinted by reference to said main groove. 6. A method of manufacturing a device according to any one of claims 1 to 4, characterized in that it comprises the manufacture of at least one imprinted block by means of the method of claim 5 and the machining of a main groove in a corresponding sole of said device.