Protective casing for a blade root during a coating operation and associated method

Abstract

This protective housing (20) intended to house a root (6) of a blade (2) extending axially from an upstream face (16) to a downstream face (18) comprises a plurality of parts (22, 24) jointly forming an imprint (30) of a dimension greater than the root (6) of the blade (2), the assembled housing (20) comprising: - an upstream portion (32), - a downstream portion (34), and - an intermediate portion (36) extending from the upstream portion (32) to the downstream portion (34), of axial dimension equal to the axial dimension of the root (6) of the blade (2), and intended to house the root (6) of the blade (2) during the coating operation, the connection (38) of the parts (22, 24) being integrally formed in the intermediate portion (36) while remaining at a distance from the axial ends of the intermediate portion (36). Figure for abstract: Fig 2

Description

Title of the invention: Protective housing for a blade root during a coating operation and associated method Technical field

[0001] The technical field of the invention is blades, in particular aircraft turbomachine blades, and more specifically blade coating operations.

[0002] In particular, the present invention relates to a housing for protecting the root of a blade during the coating operation and a method for coating the blade. Prior art

[0003] A coating is generally applied to turbomachine blades in order to protect them from the hot environment of the turbomachine.

[0004] It is advantageous to cover certain surfaces of the blades during the coating operation in order to prevent the coating from being deposited on these surfaces.

[0005] It is known to form a protective cover around the root of the blade. When such a cover is in contact with the blade, it risks flaking the coating when it is removed.

[0006] When vapor spraying the coating, it can seep through connections in the cover and deposit on the blade root.

[0007] It is sometimes difficult to detect coating overflows during a visual inspection of the blade root. Statement of the invention

[0008] The present invention therefore aims to overcome all or part of the aforementioned drawbacks, and in particular to propose a protective casing which is simple to assemble and which facilitates visual inspection of any coating overflow onto the blade.

[0009] The present invention relates to a protective housing intended to house a root of a blade during a coating operation, the blade being provided with the root for mounting it in a cell of a rotor disk, the root extending axially from an upstream face to a downstream face, the housing comprising a plurality of parts configured to assemble and jointly form an imprint of the root of the blade of a dimension greater than the root of the blade, the assembled housing comprising:

[0010] - an upstream portion,

[0011] - a downstream portion, and

[0012] - an intermediate portion extending from the upstream portion to the downstream portion, axial dimension equal to the axial dimension of the blade root, and intended to accommodate the blade root during the coating operation.

[0013] The connection of the parts is integrally formed in the intermediate portion in remaining at a distance from the axial ends of the intermediate portion.

[0014] The upstream portion of the housing is intended to be located, after assembly of the housing around the blade root, on the side of the upstream face of the blade root, that is to say upstream of the blade root.

[0015] The downstream portion of the housing is intended to be located, after assembly of the housing around the blade root, on the side of the downstream face of the blade root, that is to say on the downstream side of the blade root.

[0016] The terms radial, axial and tangential are defined relative to the axis of a turbomachine on which the rotor disk is mounted. The axis of the turbomachine is also the same as the axis of rotation of the rotor disk.

[0017] The terms upstream and downstream are defined in relation to the direction of flow of the gases from the turbomachine.

[0018] The blade root consists of a bulb and a stilt. The bulb is capable of providing the mechanical connection between the blade and the rotor. The stilt extends from the bulb radially outwards, in particular to a radially internal platform of the blade interposed between the blade and the root. The blade root extends axially from the upstream face of the bulb to the downstream face of the bulb.

[0019] In a particular embodiment, the blade is a turbine or compressor blade.

[0020] The housing forms a screen to stop coating particles moving towards the blade root. Thus, the surface condition and mechanical characteristics of the blade root material are kept constant.

[0021] The blade root impression of a dimension greater than the blade root is capable of housing the blade root in the housing without the latter being in contact with the walls of the blade root impression. This prevents chipping of the blade coating when the housing is removed.

[0022] The connection of the parts formed integrally in the intermediate portion while remaining at a distance from the axial ends of the intermediate portion ensures that any overflow of the coating is not directed towards the upstream and downstream faces of the blade root. This makes a visual check of overflow on the blade root more reliable, the projecting edges of the blade root representing areas where the risk of error during the visual check of the overflow is high.

[0023] Advantageously, the connection is integrally formed between a first axial coordinate corresponding to a position located at 20% of the axial dimension of the intermediate portion and a second axial coordinate corresponding to a position located at 80% of the axial dimension of the intermediate portion. Alternatively, the first axial coordinate may correspond to a position located at 40% of the axial dimension of the intermediate portion and the second axial coordinate may correspond to a position located at 60% of the axial dimension of the intermediate portion. This further spatially distances the risk of coating overflow from the upstream and downstream faces of the blade root.

[0024] Advantageously, the housing comprises a first part provided with an imprint of a first part of the blade root, and a second part provided with an imprint of a second part of the blade root, the first and second parts being configured to assemble so that the imprints of the first and second parts of the blade root together form the imprint of the blade root.

[0025] By using only two parts to form the footprint of the blade root, the structure of the housing is simplified. The first part is able to be assembled with the second part around the blade root by being guided axially from upstream to downstream of the blade root. The second part is able to be assembled with the first part around the blade root by being guided axially from downstream to upstream of the blade root.

[0026] In this case, the imprint of the first part of the foot of the blade comprises an imprint of a first part of the bulb and an imprint of a first part of Péchasse. Similarly, the imprint of the second part of the foot of the blade comprises an imprint of a second part of the bulb and an imprint of a second part of Péchasse.

[0027] Preferably, the first and second parts are assembled by interlocking.

[0028] According to a particular design, the first part comprises first and second sealing portions, the first sealing portion being offset towards the outside of the housing relative to the second sealing portion, the second part comprising an intermediate sealing portion inserted between the first and second sealing portions when the first and second parts fit together.

[0029] The first and second sealing portions of the first part, and the intermediate sealing portion of the second part further reduce the intrusion of coating particles by together forming a labyrinth-type seal.

[0030] Advantageously, the connection of the parts forms grooves on the outer surface of the housing, the grooves being included in a plane. Preferably, this plane is orthogonal to the axial direction.

[0031] Thus, any coating overflows are located close to this plane, making visual control of the overflow more reliable.

[0032] The housing may include a first rim extending outwardly from the outer edges of the blade root footprint.

[0033] Thus, the risk of coating overflow is reduced.

[0034] Optionally, the first rim may extend radially outwardly from the radially outer edges of the blade root footprint.

[0035] The housing may include a second rim extending inwardly of the housing from an outer edge of the first rim.

[0036] Thus, the risk of coating overflow is further reduced.

[0037] Optionally, the second rim may extend tangentially toward the inside of the housing from a radially outer edge of the first rim.

[0038] The present invention also relates to a method of coating a blade provided with a root for mounting it in a cell of a rotor disk, the root extending axially from an upstream face to a downstream face, the method comprising the following steps:

[0039] - a step of assembling a plurality of parts around the foot of the blade for form a protective casing, the parts jointly forming an imprint of the blade root of a dimension greater than the blade root, a connection of the parts being integrally formed axially between the upstream and downstream faces of the blade root; and

[0040] - a step of spraying a coating onto the blade.

[0041] Advantageously, the blade root is housed in the blade root imprint so that the blade remains at a distance from the walls of the housing.

[0042] The method may comprise, after the projection of the coating, a step of checking the absence of an overflow of the coating on the axial faces of the root of the blade.

[0043] The axial faces of the blade root are the faces of the blade root extending axially from the upstream face to the downstream face of the blade root. Brief description of the drawings

[0044] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0045] [Fig-1] schematically illustrates a blade;

[0046] [Fig.2] schematically illustrates the foot of the blade of [Fig.l] housed in a housing according to a first exemplary embodiment of the invention;

[0047] [Fig.3] schematically illustrates the connection of the housing of [Fig.2];

[0048] [Fig.4] schematically illustrates the connection of a box according to a second exemplary embodiment of the invention;

[0049] [Fig.5] schematically illustrates the foot of the blade of [Fig.l] housed in a housing according to a third exemplary embodiment of the invention;

[0050] [Fig.6] schematically illustrates the foot of the blade of [Fig.l] housed in a housing according to a fourth exemplary embodiment of the invention; and

[0051] [Fig.7] schematically illustrates a method of coating a blade according to a exemplary embodiment of the invention. Detailed description

[0052] [Fig.l] represents a blade 2, here of an aircraft turbomachine, and more precisely a low pressure turbine blade.

[0053] The blade 2 comprises a blade 4, a root 6 capable of being mounted in a cell of a rotor disk of the turbomachine, a radially internal platform 8 interposed between the blade 4 and the root 6, and a heel 10 which comprises a radially external platform and wipers. The root 6 of the blade 2 comprises a bulb 12 capable of ensuring the mechanical connection between the blade 2 and the rotor, and a stilt 14 extending between the bulb 12 and the radially internal platform 8.

[0054] The root 6 of the blade 2 comprises an upstream face 16 and a downstream face 18, the root 6 extending axially from the upstream face 16 to the downstream face 18.

[0055] The terms radial, axial and tangential are defined relative to the axis of the turbomachine.

[0056] [Fig. 2] shows the root 6 of the blade 2 housed in a protective housing 20. The housing 20 is capable of protecting the root 6 of the blade 2 from a sprayed coating, for example from a vapor-phase sprayed coating such as aluminum, during a coating operation. The housing 20 comprises a plurality of parts, and here first and second parts 22, 24, assembled together.

[0057] The first part 22 is provided with an imprint 26 of a first part of the foot 6 of the blade 2.

[0058] The imprint 26 of the first part of the root 6 of the blade 2 comprises an imprint of a first part of the Péchasse 14 and of a first part of the bulb 12. The imprint 26 of the first part of the root 6 of the blade 2 is here of a dimension greater than the dimension of the upstream half of the root 6 of the blade 2.

[0059] The imprint 26 of the first part of the root 6 of the blade 2 forms in the first part 22 a cavity open radially towards the outside and axially towards the downstream.

[0060] The second part 24 is provided with an imprint 28 of a second part of the foot 6 of the blade 2.

[0061] The imprint 28 of the second part of the root 6 of the blade 2 comprises an imprint of a second part of Péchasse 14 and of a second part of the bulb 12. The imprint 28 of the second part of the root 6 of the blade 2 is of a dimension greater than the dimension of the downstream half of the root 6 of the blade 2.

[0062] The imprint 28 of the second part of the root 6 of the blade 2 forms in the second part 24 a cavity open radially towards the outside and axially towards the upstream.

[0063] When assembling the first and second parts 22, 24, the impressions 26, 28 of the first and second parts of the root 6 of the blade 2 join to form together a footprint 30 of foot 6 of dawn 2.

[0064] The imprint 30 of the root 6 of the blade 2 is of a dimension greater than the root 6 of the blade 2 so that a clearance remains between the root 6 of the blade 2 and the walls of the housing 20 forming the imprint 30 of the root 6 of the blade 2.

[0065] The assembled housing 20 comprises an upstream portion 32, a downstream portion 34, and an intermediate portion 36 extending from the upstream portion 32 to the downstream portion 34.

[0066] The intermediate portion 36 is formed by a part of the first part 22 and by a part of the second part 24. The upstream portion 32 is formed by the complementary part of the part of the first part 22. The downstream portion 34 is formed by the complementary part of the part of the second part 24.

[0067] The intermediate portion 36 has an axial dimension equal to the axial dimension of the root 6 of the blade 2, taken as the distance from the upstream face 16 to the downstream face 18 of the root 6 of the blade 2. The intermediate portion 36 houses the root 6 of the blade 2, and here extends axially from a first plane containing the upstream face 16 of the root 6 of the blade 2 to a second plane containing the downstream face 18 of the root 6 of the blade 2. The upstream portion 32 extends upstream of the intermediate portion 36. The downstream portion 34 extends downstream of the intermediate portion 36.

[0068] The first and second parts 22, 24 are assembled so that the connection 38 of the parts 22, 24 is integrally formed in the intermediate portion 36 while remaining at a distance from the axial ends of the intermediate portion 36. The connection 38 is therefore integrally formed between the first plane containing the upstream face 16 of the root of the blade 2 and the second plane containing the downstream face 18 of the root of the blade 2, and more particularly between a first axial coordinate corresponding to a position located at 40% of the axial dimension of the intermediate portion 36 and a second axial coordinate corresponding to a position located at 60% of the axial dimension of the intermediate portion 36. The connection 38 thus formed reduces the risk of deposit overflow at the edges of the root of the blade 2, any overflow then taking place approximately in the axial middle of the axial faces of the root 6 of the blade 2.

[0069] As illustrated more visibly in [Fig.3], the first and second parts 22, 24 fit together.

[0070] The second part 24 comprises a shoulder 40. The first part 22 comprises a first sealing portion 42 capable of coming into radial abutment against an axially extending face of the shoulder 40 and of coming into axial abutment against a radially extending face of the shoulder 40. The first sealing portion 42 thus forms a barrier against a flow of coating particles directed towards the blade 2 during a coating operation.

[0071] The first part 22 further comprises a female end piece 44 offset towards the inside of the housing 20 relative to the first sealing portion 42 and offset axially upstream relative to the first sealing portion 42. The second part 24 comprises at its upstream end a male end piece 46 capable of fitting into the female end piece 44 of the first part 22.

[0072] When the housing 20 is assembled, the connection 38 of the housing 20 is formed by the first sealing portion 42 and the female end piece 44 of the first part 22 and by the shoulder 40 and the male end piece 46 of the second part 24.

[0073] With reference to [Fig. 2], the connection 38 of the first and second parts 22, 24 forms grooves 48 on the outer surface of the housing 20. The grooves 48 are included in the same plane which here passes through the axial middle of the root 6 of the blade 2.

[0074] In the example illustrated in Figures 2 and 3, the imprint 30 of the root 6 of the blade 2 is such that its radially outer edges are located radially between the radially outer and inner surfaces of the radially inner platform 8 when the root 6 of the blade 2 is housed in the housing 20.

[0075] The second embodiment illustrated in [Fig. 4] in which the elements identical to those of the preceding figures bear the same references, differs from the first embodiment illustrated in Figures 2 and 3 in that the first part 22 comprises the first sealing portion 42 and a second sealing portion 50 offset towards the inside of the housing 20 relative to the first sealing portion 42. The second part 24 here comprises an intermediate sealing portion 52 capable of being inserted between the first and second sealing portions 42, 50 of the first part.

[0076] When the housing 20 is assembled, the connection 38 of the housing 20 is here formed by the first and second sealing portions 42, 50 of the first part 22 and by the intermediate sealing portion 52 of the second part 24 which together form a labyrinth-type seal.

[0077] The third embodiment illustrated in [Fig. 5] in which the elements identical to those of the preceding figures bear the same references, differs from the first embodiment illustrated in Figures 2 and 3 in that the housing 20 comprises a first rim 54 extending radially outwards from the radially outer edges of the imprint 30 of the root 6 of the blade 2. More precisely, the first part 22 comprises a first part of the first rim 54, the second part 24 comprising a second part of the first rim 54.

[0078] The first rim 54 of the housing 20 is such that its radially outer edge is offset radially outwards relative to the radially outer surface of the radially inner platform 8 when the root 6 of the blade 2 is housed in the housing 20. Thus, the risk of coating overflowing onto the root 6 of the blade 2 is further reduced.

[0079] The fourth embodiment illustrated in [Fig.6] in which the elements identical to those of the preceding figures bear the same references, differs from the third embodiment illustrated in [Fig.5] in that the housing 20 comprises a second rim 56 extending tangentially towards the inside of the housing from the radially outer edge of the first rim 54. More precisely, the first part 22 comprises a first part of the second rim 56 extending tangentially towards the inside of the first part 22 a radially outer edge of the first part of the first rim 54, the second part 24 comprising a second part of the second rim 56 extending tangentially towards the inside of the second part 24 a radially outer edge of the second part of the first rim 54.

[0080] [Fig.7] schematically represents a method of coating a blade 2.

[0081] We begin with a step 58 of assembling the plurality of parts, and here the first and second parts 22, 24, around the root 6 of the blade 2 to form the protective housing 20. The first part 22 is positioned upstream of the root 6 of the blade 2 and the second part 24 downstream of the root 6 of the blade 2. Then, the first part 22 is guided axially downstream so that an upstream part, here the upstream half, of the root 6 of the blade 2 is housed in the imprint 26 of the first part of the root 6 of the blade 2. Before, after, or at the same time as the first part 22 is guided, the second part 24 is guided axially upstream so that a downstream part, here the downstream half, of the root 6 of the blade 2 is housed in the imprint 28 of the second part of the root 6 of the blade 2.The parts 22, 24 are fitted together so that the connection 38 is integrally formed axially between the upstream and downstream faces 16, 18 of the root 6 of the blade 2, and more precisely so that the connection 38 is integrally formed between the first and second axial coordinates.

[0082] Advantageously, it is ensured that the root 6 of the blade 2 is housed in the imprint 30 of the root 6 of the blade 2 formed jointly by the parts 22, 24 so that the blade 2 remains at a distance from the walls of the housing 20, that is to say so as not to be in contact with the housing 20.

[0083] Then a step 60 of spraying a coating onto the blade 2 is carried out.

[0084] The parts 22, 24 of the housing 20 are then disassembled by guiding the first part 22 axially upstream and the second part 24 axially downstream.

[0085] Finally, a step 62 is preferably carried out to check, in particular visually, that there is no overflow of the coating onto the axial faces of the root 6 of the blade 2.

Claims

Claims

1. Protective housing (20) intended to house a root (6) of a blade (2) during a coating operation, the blade (2) being provided with the root (6) for mounting it in a cell of a rotor disk, the root (6) extending axially from an upstream face (16) to a downstream face (18), the housing (20) comprising a plurality of parts (22, 24) configured to assemble and jointly form an imprint (30) of the root (6) of the blade (2) of a dimension greater than the root (6) of the blade (2), the assembled housing (20) comprising: - an upstream portion (32), - a downstream portion (34), and - an intermediate portion (36) extending from the upstream portion (32) to the downstream portion (34), of axial dimension equal to the axial dimension of the root (6) of the blade (2), and intended to house the foot (6) of the blade (2) during the coating operation, characterized in that the connection (38) of the parts (22,24) is integrally formed in the intermediate portion (36) while remaining at a distance from the axial ends of the intermediate portion (36).,

2. Housing (20) according to claim 1, comprising a first part (22) provided with an imprint (26) of a first part of the root (6) of the blade (2), and a second part (24) provided with an imprint (28) of a second part of the root (6) of the blade (2), the first and second parts (22, 24) being configured to assemble so that the imprints (26, 28) of the first and second parts of the root (6) of the blade (2) together form the imprint (30) of the root (6) of the blade (2).

3. A housing (20) according to claim 2, wherein the first and second parts (22, 24) fit together by snap-fitting.

4. A housing (20) according to claim 3, wherein the first part (22) comprises first and second sealing portions (42, 50), the first sealing portion (42) being offset outwardly of the housing (20) relative to the second sealing portion (50), the second part (24) comprising an intermediate sealing portion (52) inserting between the first and second sealing portions (42, 50) when the first and second parts (22, 24) fit together.

5. Housing (20) according to any one of claims 1 to 4, wherein the connection (38) of the parts (22, 24) forms grooves (48) on the outer surface of the housing (20), the grooves (48) being included in a plane.

6. A housing (20) according to any one of claims 1 to 5, comprising a first flange (54) extending outwardly from the outer edges of the footprint (30) of the root (6) of the blade (2).

7. A housing (20) according to claim 6, comprising a second flange (56) extending inwardly of the housing from an outer edge of the first flange (54).

8. Method for coating a blade (2) provided with a root (6) for mounting it in a cell of a rotor disk, the root (6) extending axially from an upstream face (16) to a downstream face (18), characterized in that it comprises the following steps: - a step of assembling (58) a plurality of parts (22, 24) around the root (6) of the blade (2) to form a protective housing (20), the parts (22, 24) jointly forming an imprint (30) of the root (6) of the blade (2) of a dimension greater than the root (6) of the blade (2), a connection (38) of the parts (22, 24) being integrally formed axially between the upstream and downstream faces (16, 18) of the root (6) of the blade (2); and - a step of spraying (60) a coating onto the blade (2).

9. Method according to claim 8, in which the root (6) of the blade (2) is housed in the imprint (30) of the root (6) of the blade (2) so that the blade (2) remains at a distance from the walls of the housing (20).

10. Method according to claim 8 or 9 comprising, after the projection of the coating, a step of checking (62) the absence of an overflow of the coating on the axial faces of the root (6) of the blade (2).

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