Shot-blasting nozzle

Abstract

The invention relates to a shot-blasting nozzle (1), which comprises a conduit (11) for feeding media into the shot-blasting nozzle (1), the shot-blasting nozzle (1) comprising: - a hollow cylindrical body (2) extending around an axis (A) from a first end (21) towards a second end (22), the first end (21) being suitable for being in communication with the media feed conduit (11); - a nozzle insert (3) extending into the shot-blasting nozzle (1) such that a stream of media fed into the shot-blasting nozzle (1) from the first end (21) is split in contact with the nozzle insert (3), the nozzle insert (3) also extending so as to diffuse the stream of media in a direction forming a non-zero angle with the axis (A).

Description

[0001] DESCRIPTION

[0002] TITLE: Shot blasting nozzle

[0003] TECHNICAL FIELD

[0004] The present invention relates generally to the field of shot blasting benches, more specifically to devices for projecting a shot blasting flux.

[0005] The invention relates more specifically, but not exclusively, to a shot blasting nozzle particularly suitable for shot blasting a long tubular part, for example a turbine shaft.

[0006] STATE OF THE ART

[0007] Shot peening involves spraying a media to impact the surface of a part, modifying its surface finish and inducing compressive stresses to improve its fatigue life. Specifically, the aim is to break up machining marks that appear during the machining process and are potential crack initiation sites. Completely breaking up these machining marks extends the fatigue life of the part. The results of shot peening depend primarily on three parameters: the type of media, the coverage rate, and the Almen intensity.

[0008] The type of media is arbitrary; it can be glass, steel, or ceramic beads, or honed cut wire, or any type of solid or liquid particle chosen according to the hardness of the material of the part being shot-blasted, the condition of its surface, and the desired intensity. The media is projected through a nozzle that determines the shape and direction of the jet, which is a cone of variable size. The nozzle can be mounted on a six-axis robot, a boom, or a motorized table, which generally allow for adjustment of the position and orientation of the shot-blasting jet.

[0009] The coverage rate of a shot-blasted surface measures the extent of shot peening on a surface. Coverage is measured visually, and expressed as a percentage, by the percentage of indentations covering the shot-blasted surface. Coverage is considered complete, or 125%, when it corresponds to 1.25 times the time required for the entire treated surface to be covered by impacts. The human eye can perceive a maximum coverage of 98%, which is why a multiplier is applied to obtain a theoretical 125% coverage. The stresses introduced by shot peening initially increase very rapidly in intensity and depth with the coverage rate, up to coverage levels of approximately 90 to 100%. This progression then becomes asymptotic. When the coverage rate is less than 100%, a potential reduction in the mechanical strength and lifespan of the part is possible.This situation, known as under-coverage, is prohibited if complete coverage is required. Conversely, when the coverage rate exceeds 125%, the surface is considered over-covered. Over-coverage can lead to the generation of surface defects, such as surface folds, corner folds, bulges, cracks, notches, burrs, incrustations, roughness defects, or other non-compliant surface conditions, which are detrimental.

[0010] Shot peening intensity quantifies the energy transferred to the workpiece. Shot peening intensity is determined by measuring the deformations, known as Almen deflections, of a standardized Almen specimen, for example, following SAE J442 and SAE J443 recommendations. An Almen specimen is thus a parallelepiped block made of SAE 1070 steel, with dimensions of 76.2 millimeters (mm) wide by 18.9 mm long, and a thickness of 1.29 mm, 0.78 mm, or 2.38 mm. The specimen is fixed to a support, also called an Almen block, which is standardized and held in place by four screws.

[0011] A test to determine shot peening intensity involves successively shot peening at least four Almen specimens, doubling the peening time between each shot peening for each successive specimen. For example, if the first specimen is shot peened for 5 seconds, the second should be shot peened for 10 seconds, the third for 20 seconds, and finally the last specimen for 40 seconds. After each shot peening, the deformation of the Almen specimen is measured in millimeters and plotted against time on a graph to form a saturation curve. The saturation curve, by representing the Almen intensity as a function of time, shows that after a certain period, the intensity increases only marginally. Indeed, such a saturation curve exhibits a sharp inflection point near a point known as the "saturation point."Between the saturation point and twice the time between the origin and the saturation point, the Almen arrow increases by a maximum of 10% of its growth before the saturation point; that is, the saturation point is an inflection point from which the intensity tends towards a limiting value. The saturation point corresponds to the Almen intensity.

[0012] Currently, shot blasting nozzles are generally cylindrical and include a straight internal channel of variable diameter, through which the media is sprayed at a speed between 1 and 340 m / s. However, these shot blasting nozzles are not suitable for efficiently blasting certain parts with complex geometries, such as shafts and other cylindrical parts, which must be blasted from the inside. The shape of the internal surfaces of these cylindrical parts necessitates blasting by rebound in hard-to-reach areas. By "rebound blasting," we mean that the media stream received by the inaccessible area has already impacted at least one area with a direct jet. It is then difficult to predict the trajectory of the media stream in such a case, and even more so to guarantee not only the Almen intensity but also its homogeneity across all internal surfaces.

[0013] Furthermore, the projection of media inside such parts causes significant vibrations, which can lead to a high risk of collision between the nozzle and the workpiece, potentially damaging both. Finally, when the media used is too abrasive, the lifespan of the nozzles is drastically reduced. For example, the projection of steel shot deforms threads, thin walls, and channels, disrupting the media flow. In some extreme cases, the nozzle is perforated and then shot-blasts unintended areas. Therefore, there is a need for a nozzle that addresses the aforementioned drawbacks.

[0014] DESCRIPTION OF THE INVENTION

[0015] One object of the invention is to remedy the aforementioned drawbacks by providing a shot blasting nozzle for a shot blasting system comprising a media introduction conduit into the shot blasting nozzle, the shot blasting nozzle comprising:

[0016] - a hollow cylindrical body extending around an axis from a first end to a second end, the first end being adapted to communicate with the media introduction conduit; and

[0017] - a nozzle extending into the shot blasting nozzle from the second end to the first end over part of the length of the cylindrical body around the axis, thus forming a passage in the cylindrical body around the nozzle, so that a flow of media introduced into the shot blasting nozzle from the first end is divided at the contact of the nozzle, the nozzle further extending to diffuse the flow of media in a direction forming a non-zero angle with the axis.

[0018] The shot blasting nozzle according to the invention is advantageously complemented by the following characteristics, taken individually or in one of their technically possible combinations:

[0019] - The nozzle includes:

[0020] • a fin extending radially from the axis to the interior of the cylindrical body and comprising an elongated profiled portion, the profiled portion being configured to divide a media flow originating from the first end of the cylindrical body parallel to the axis,

[0021] • a diffuser extending around the axis and comprising

[0022] • a first cylindrical end, contiguous to the fin, and • a second cylindrical end distal to the first end of the cylindrical body and projecting from the cylindrical body, the second cylindrical end having a diameter greater than the diameter of the first cylindrical end,

[0023] • the first and second cylindrical ends being connected by a hyperbolic profile surface in a plane containing the axis, so that a media flow from the fin is deflected along the hyperbolic profile;

[0024] • an anvil comprising a cylinder contiguous to the diffuser, the cylinder having a diameter greater than the diameter of the second cylindrical end of the diffuser and a chamfered edge proximal to the diffuser, the anvil being configured to send a media stream received from the diffuser in a direction forming a non-zero angle with the axis;

[0025] • so that a media flow received parallel to the axis by the first end of the cylindrical body is divided by the fin, deflected by the diffuser and sent by the anvil in a direction forming a non-zero angle with the axis;

[0026] - the nozzle includes an end piece, the end piece including a nut collinear with the axis, the anvil, the diffuser and the fin being traversed by a thread collinear with the axis so that the end piece, the anvil, the diffuser and the fin can be joined together by a threaded rod screwed into the thread and the nut, the end piece then being contiguous with the anvil;

[0027] - an inner lining conforming to the inside of the cylindrical body, the inner lining and the cylindrical body being traversed along an axis perpendicular to the axis by lugs configured to allow the attachment of the media introduction conduit;

[0028] - the cylindrical body includes, on an external surface, a thread configured to allow the attachment of the media introduction conduit, the media introduction conduit including a tapped hole;

[0029] - one of the inner lining, fin, diffuser and anvil comprises tungsten carbide;

[0030] - the nozzle comprises several fins, the fins being linked by a central part so as to extend radially from the axis to the inside of the cylindrical body, the fins being separated two by two by the same angle.

[0031] The invention also relates to a shot blasting method for a cylindrical part extending along an axis by means of such a nozzle, the shot blasting method comprising the following steps:

[0032] - insertion of the shot blasting nozzle inside the cylindrical part so that the axis of the shot blasting nozzle is parallel to a longitudinal axis of the cylindrical part;

[0033] - feeding the shot blasting nozzle with a media stream, the shot blasting nozzle then projecting the media stream onto an internal surface of the cylindrical part. The invention also relates to a turbomachine shaft obtained by the above process, as well as a shot blasting system comprising a shot blasting nozzle as described above.

[0034] DESCRIPTION OF THE FIGURES

[0035] Other features, purposes and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0036] Figure 1 is an overview of a shot blasting nozzle according to one embodiment of the invention;

[0037] Figure 2 is a detailed side view of a fin of the shot blasting nozzle of Figure 1;

[0038] Figure 3 is a cross-sectional view of the fins of the shot blasting nozzle of Figure 1;

[0039] Figure 4 is a detail view of a diffuser of the shot blasting nozzle of Figure 1;

[0040] Figure 5 is a detail view of an anvil of the shot blasting nozzle of Figure 1;

[0041] Figure 6 is a detailed view of a tip of the shot blasting nozzle shown in Figure 1; and

[0042] Figure 7 is a diagram showing the steps of a shot blasting process according to the invention.

[0043] Across all figures, similar elements bear identical references.

[0044] DETAILED DESCRIPTION OF THE INVENTION

[0045] With reference to Figure 1, the shot blasting nozzle 1 proposed in this presentation is designed to be integrated into a shot blasting system, for example a manually or automatically operated pole, a robot or any other equipment including a media introduction conduit 11 capable of supplying the shot blasting nozzle 1 with the media to be projected onto a part to be shot blasted.

[0046] The shot blasting nozzle 1 comprises a hollow cylindrical body 2 extending around an axis A from a first end 21 to a second end 22. The first end 21 is adapted to communicate with the media feed duct 11, and the media flows from this first end 21 to the second end 22. In the following description, the terms upstream and downstream will be used with reference to this flow direction. An inner lining 23 can fit inside the cylindrical body 2, the inner lining 23 and the cylindrical body 2 being secured together and to the media feed duct 11 by lugs 24 passing through them along an axis perpendicular to the axis A. Alternatively, the cylindrical body 2 comprises, on an outer surface, a thread configured to allow attachment of the media feed duct 11, the media feed duct 11 itself comprising a threaded hole on its inner surface.The inner lining 23 provides internal protection to the cylindrical body 2, resisting abrasion from the shot blasting media. It therefore prevents premature wear of the cylindrical body 2 and its threads, if present. The inner lining 23 thus comprises a material resistant to abrasion from the media, for example, a metallic carbide such as tungsten carbide, while the cylindrical body 2 may be made of steel.

[0047] The shot blasting nozzle 1 includes a nozzle 3, which extends within the cylindrical body 2 from the second end 22 to the first end 21 around the axis A. The nozzle 3 may not be entirely contained within the cylindrical body 2. Within the latter, the nozzle 3 has a diameter smaller than that of the cylindrical body 2 and therefore forms an annular passage collinear with the axis A. Thus, the media flow introduced parallel to the axis A into the shot blasting nozzle 1, from the first end 21, is divided at the contact with the nozzle 3, the nozzle 3 further extending to diffuse the media flow in a direction forming a non-zero angle α with the axis A downstream, at the second end 22. Preferably, the angle α with the axis A is chosen to be between 70° and 110°, and even more preferably 90°. so that the media is dispersed perpendicular to the shot blasting nozzle 1.

[0048] The nozzle 3 includes, for dividing the media flow, at least one fin 4, illustrated in Figure 2, which extends radially from the axis A to the interior of the cylindrical body 2, where it is fixed. The fin 4 includes a profiled portion 41 elongated along the axis A, the profiled portion 41 being configured to divide, direct, channel, and orient the media jet originating from the first end 21 of the cylindrical body 2. Preferably, there are several fins 4, for example, three fins 4, each comprising a central portion 42 and a profiled portion 41, as illustrated in Figure 3. The central portions 42 are configured to connect around the axis A, so that the profiled portions 41 extend in a star shape, i.e., an angle of the same value separates each profiled portion. In other words, the fins 4 are separated in pairs by the same angle. Put another way, the fins 4 are arranged equidistantly.However, too many fins can impede media flow and cause undesirable pressure variations and turbulence. Advantageously, the fins are made of metal carbide, for example tungsten carbide, or any other material that can withstand abrasion from the media.

[0049] Downstream of the fin 4, the nozzle 3 includes a diffuser 5, illustrated in Figure 4. The diffuser 5 extends around the axis A and includes a first cylindrical end 51, contiguous to the fin 4, and a second cylindrical end 52, distal to the first end 21 of the cylindrical body 2 and of the fin 4. In other words, the first cylindrical end 51 is upstream and the second cylindrical end 52 is downstream.

[0050] The second cylindrical end 52 protrudes from the cylindrical body 2 and has a diameter greater than the diameter of the first cylindrical end 51. The first and second cylindrical ends 51 and 52 are connected by a hyperbolic profile surface 53 in a plane containing the axis A. By "hyperbolic profile," we mean that the surface connecting the cylindrical ends 51 and 52 is a surface of revolution about the axis A, and that the curve generating this surface is a parameterized hyperbolic curve. The hyperbolic profile 53 is chosen so that a media flow from the fin 4 is deflected. The direction of the deflection therefore depends on the hyperbolic profile 53, which can have a steeper or shallower slope depending on the desired angle of deflection for the media flow.

[0051] Advantageously, the diffuser 5 is made of metallic carbide, for example tungsten carbide or any other material which can withstand the abrasion exerted by the media.

[0052] Referring to Figure 5, the nozzle 3 includes an anvil 6. The anvil 6 comprises a cylinder 60 collinear with axis A and contiguous with the diffuser 5, i.e., it is located downstream of it. The cylinder 60 has a diameter greater than the diameter of the second cylindrical end 52 of the diffuser s and a chamfered edge 61 proximal to the diffuser s. The dimensions of the chamfer 61, in particular its angle with respect to axis A, are adapted according to the part to be shot-peened in order to adjust the orientation of the jet. Thus, the media flow deflected by the diffuser 5 impacts at least partially the anvil 6, thereby generating rebounds. The anvil 6 therefore redirects part of the jet flow in the opposite direction to the media projection jet. The media stream is then projected in a direction incident to axis A, for example around a substantially perpendicular direction, which makes it possible to reach any interior area of ​​a room.In other words, in the plane of figures 1 to 6, there is an angle between the axis around which the media is projected and axis A. Anvil 6 is also made of metal carbide, for example tungsten carbide or any other material that can withstand the abrasion exerted by the media.

[0053] Nozzle 3 receives the media flow upstream, parallel to axis A, through the first end 21 of the cylindrical body 2. It is divided by the fin 4 before being deflected by the diffuser 5 and sent through the anvil 6 in a direction incident to axis A, for example, a perpendicular direction. Thus, the media flow is modified from axial to circular, being projected 360° around the shot blasting nozzle 1.

[0054] With reference to Figure 6, the nozzle 3 can also advantageously include an end piece 7 downstream of the anvil, the end piece comprising a nut 71 collinear with axis A. This end piece, which can have an aerodynamic shape, or any other shape adapted to absorb an impact, is particularly useful for securing the elements of the nozzle 3. Thus, the anvil 6, the diffuser 5, and the fin 4 can be traversed by a threaded hole 72 collinear with axis A, a threaded hole receiving a threaded rod so that the end piece 7, the anvil 6, the diffuser 5, and the fin 4 are connected by a threaded rod screwed into the threaded hole 72 and the nut 71. The nozzle 3 is then easy to assemble and disassemble while being sufficiently robust in use. Furthermore, the threaded rod maintains the collinearity of the elements, thus preserving the homogeneity of the media flow projected over 360°. Of course, any other alternative assembly method is possible, such as glue or welding.

[0055] Referring to Figure 7, the described shot blasting nozzle 1 enables a particularly efficient shot blasting process S for the interior of a cylindrical part, since the nozzle 3 allows access to all internal geometries of the cylindrical part. The cylindrical part could be, for example, a turbine shaft. The process includes an insertion step (step S1) of the shot blasting nozzle 1 into the cylindrical part such that the axis A of the shot blasting nozzle 1 is parallel to a longitudinal axis of the part. A feeding step (step S2) of the shot blasting nozzle 1 with a media stream via the media introduction conduit 11 is then initiated, the shot blasting nozzle 1 then projecting the media stream onto an internal surface of the cylindrical part. During this step, the shot blasting nozzle 1 can be moved to project the media stream to various locations within the cylindrical part.When the predetermined Almen intensity is reached, the feeding of media to the shot blasting nozzle 1 ceases, i.e. shot blasting is stopped, and the nozzle is withdrawn.

[0056] This process S is particularly effective in the production of turbomachine shafts, whose internal geometries were difficult to access with prior art shot blasting nozzles, but of course, any type of hollow part can also benefit from it. The shot blasting nozzle 1 according to the invention provides vibrational stability of the blasting system and a much more regular shot-blasting pattern on the surface of the cylindrical part, thus ensuring uniform coverage and therefore a conforming surface finish. The materials chosen allow for uninterrupted operation for several years, and the simplicity of assembly makes maintenance easy.

Claims

DEMANDS 1. Shot blasting nozzle (1) of a shot blasting system comprising a media introduction conduit (11) into the shot blasting nozzle (1), the shot blasting nozzle (1) comprising: - a hollow cylindrical body (2) extending around an axis (A) from a first end (21) to a second end (22), the first end (21) being adapted to be in communication with the media introduction conduit (11); - a nozzle (3) extending into the shot blasting nozzle (1) from the second end (22) to the first end (21) over a portion of the length of the cylindrical body (2) around the axis (A), thus forming a passage in the cylindrical body (2) around the nozzle (3), so that a media flow introduced into the shot blasting nozzle (1) from the first end (21) is divided at the contact with the nozzle (3), the nozzle (3) being configured to diffuse the media flow in a direction forming a non-zero angle with the axis (A), the nozzle comprising: - a profiled part (41) configured to divide the media flow from the first end (21) of the cylindrical body parallel to the axis (A), - a diffuser (5) extending around the axis (A) and comprising: - a first cylindrical end (51), contiguous to the fin (4), and - a second cylindrical end (52) distal to the first end (21) of the cylindrical body (2) and projecting from the cylindrical body (2), the second cylindrical end (52) having a diameter greater than a diameter of the first cylindrical end (51), the diffuser being configured to deflect the media flow from the profiled portion (41); and - an anvil (6) comprising a cylinder (60) contiguous to the diffuser (5), the cylinder (60) having a diameter greater than the diameter of the second cylindrical end (52) of the diffuser (5), the anvil (6) being configured to send the media stream received from the diffuser (5) in a direction forming a non-zero angle with the axis (A).

2. Shot blasting nozzle (1) according to claim 1, wherein the anvil (6) is configured to send the media stream received from the diffuser (5) in a direction incident to the axis (A).

3. Shot blasting nozzle (1) according to any one of claims 1 and 2, wherein the nozzle (3) comprises a fin (4) extending radially from the axis (A) to the inside of the cylindrical body (2) and comprising the profiled part (41).

4. Shot blasting nozzle (1) according to claim 3, wherein the nozzle (3) comprises several fins (4), the fins (4) being linked by a central portion so as to extend radially from the axis (A) to the inside of the cylindrical body (2), the fins (4) being separated two by two by the same angle.

5. Shot blasting nozzle (1) according to any one of claims 1 to 4, wherein the first and second cylindrical ends (51, 52) of the diffuser (5) are connected by a hyperbolic profile surface (53) in a plane containing the axis (A), so that the media flow from the fin (4) is deflected along the hyperbolic profile (53).

6. Shot blasting nozzle (1) according to any one of claims 1 to 5, wherein the anvil (6) further comprises a chamfered edge (61) proximal to the diffuser (5), the anvil (6) being configured to send the media stream received from the diffuser (5) in a direction forming a non-zero angle with the axis (A).

7. Shot blasting nozzle (1) according to any one of claims 1 to 6, wherein the nozzle (3) comprises a tip (7), the tip comprising a nut (71) collinear with the axis (A), the anvil (6), the diffuser (5) and the profiled part (41) being traversed by a thread (72) collinear with the axis (A) so that the tip (7), the anvil (6), the diffuser (5) and the profiled part (41) can be joined together by a threaded rod screwed into the thread (72) and the nut (71), the tip (7) then being contiguous with the anvil (6).

8. Shot blasting nozzle (1) according to any one of claims 1 to 7, further comprising an inner lining (23) conforming to the inside of the cylindrical body (2), the inner lining (23) and the cylindrical body (2) being traversed along an axis perpendicular to the axis (A) by lugs (24) configured to allow the attachment of the media introduction conduit (11).

9. Shot blasting nozzle (1) according to any one of claims 1 to 8, wherein the cylindrical body (2) comprises, on an external surface, a thread configured to allow the attachment of the media introduction conduit (11), the media introduction conduit (11) comprising a tapped hole.

10. Shot blasting nozzle (1) according to any one of claims 1 to 9, wherein one of the inner lining (23), the profiled part (41), the diffuser (5) and the anvil (6) comprises tungsten carbide.

11. A shot blasting method for a cylindrical part extending along an axis (X) by means of a shot blasting nozzle (1) according to any one of claims 1 to 10, the shot blasting method comprising the following steps: - insertion (S1) of the shot blasting nozzle (1) inside the cylindrical part so that the axis (A) of the shot blasting nozzle (1) is parallel to a longitudinal axis of the cylindrical part; - feeding (S2) of the shot blasting nozzle (1) by a media stream, the shot blasting nozzle (1) then projecting the media stream onto an internal surface of the cylindrical part.

12. Turbomachine shaft obtained by the process of claim 10.

13. Shot blasting system comprising a shot blasting nozzle (1) according to any one of claims 1 to 12.

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