AU2011333514A1

AU2011333514A1 - Fanwheel attachment using expansion-tolerant conically tapered rings

Info

Publication number: AU2011333514A1
Application number: AU2011333514A
Authority: AU
Inventors: Guy Constant Ghislain Delaisse; Alain Francois-Emile Godichon; Dominique Georges Revillot
Original assignee: Flakt Solyvent Ventec SAS
Current assignee: Howden Solyvent Ventec SAS
Priority date: 2010-11-26
Filing date: 2011-11-25
Publication date: 2013-07-04
Anticipated expiration: 2031-11-25
Also published as: BR112013013093A2; FR2968046B1; KR101835594B1; CA2819004A1; CA2819004C; KR20140000292A; CL2013001462A1; WO2012069770A1; RU2013126295A; AU2011333514B2; RU2604407C2; FR2968046A1; BR112013013093A8

Abstract

The invention relates to a fan comprising at least one wheel (2) which is designed to collaborate with a fluid and which is attached to a shaft (3), itself able to rotate about an axis of rotation (Χ-Χ'), by clamping between a first supporting member (10) and a second supporting member (11) which are held by said shaft and forced axially toward one another, the first supporting member (10) having, where it meets the wheel, a first substantially conical bearing surface (12) which is substantially borne by a first generator cone (C12) of which the vertex (F12), known as the "first focal point" is directed toward the second supporting member and of which the vertex half angle (0.12) is greater than the grip angle corresponding to the coefficient of friction between said first bearing surface and the wheel. Industrial fans.

Description

1 FANWHEEL ATTACHMENT USING EXPANSION-TOLERANT CONICALLY TAPERED RINGS TECHNICAL FIELD 5 The present invention relates to the general field of assembling a part that is of the wheel type onto a shaft or other member having an axis of rotation, and in particular to assemblies of this type that are designed to be exposed to high thermal operating stresses, and 10 more particularly to high temperatures and/or to high temperature gradients. The present invention relates more particularly to a device designed to drive a fluid in motion or to be driven by a fluid in motion, such as a fan, a pump, or a 15 turbine, said device including at least one wheel that is designed to co-operate with said fluid in order to drive it or to be driven by it, said wheel being fastened to a shaft, itself mounted to move in rotation about an axis of rotation, the wheel being fastened to the shaft by 20 being clamped between first and second thrust members that are retained by said shaft and that are urged axially towards each other. The present invention also relates to a method of assembling a wheel onto a shaft that is mounted to move 25 in rotation. PRIOR ART Various mechanical mounting solutions are well known to the person skilled in the art when it is necessary to 30 assemble a mechanical part, and more particularly a wheel onto a shaft in order to constrain the two parts to move together in rotation and/or in translation, and thus enable torque to be transmitted from the wheel to the shaft or vice versa. 35 Among the known solutions, there exist, in particular, force-fitting or hot interference fitting, making it possible to force a shaft into the hub of the 4352309_1 (GHMatters) P93775.AU 2 wheel with the diameter of the shaft being slightly greater than the diameter of the bore in said hub, the assembly thus being held tight by the stresses resulting from the deformation of the parts, and more particularly 5 their elastic radial deformation. Assemblies on spindles are also known in which the shaft has a slightly inclined support span so as to enable a conical hub of complementary shape to be fitted over it, and pressed endwise by a bolt or by a nut. 10 The very shallow conical taper of the elements enables the wheel to fit over the spindle substantially over the entire length of the hub, while preserving a thrust surface that extends over the entire bore of the hub and that makes it possible to subject said wheel to 15 essentially radial clamping stress, and the larger the holding force that compresses the wheel against the spindle the higher the essentially radial clamping stress. Although such assembly methods are generally 20 satisfactory, they suffer from certain drawbacks. Firstly, they systematically generate high stresses in the assembled parts. In particular, the centrifugal radial stresses that are exerted on the hub and the resulting tangential 25 stresses can, in certain situations, and in particular when excessive clamping is applied on assembly, cause fatigue, deformation, or indeed splitting apart by said hub cracking. In addition, such assemblies are particularly 30 sensitive to the consequences of thermal expansion phenomena that occur in uses in which said assemblies are subjected to high temperatures or to high temperature gradients. This applies in particular when the assembly is 35 incorporated into a device designed to be immersed in a fluid that is particularly hot, or that is subjected to large and/or rapid variations in temperature, e.g. gases 4352309_1 (GHMatters) P93775.AU 3 from a burner, from a blast furnace, or from an industrial furnace. Depending on whether the shaft tends to expand radially to a larger extent or, conversely, to a smaller 5 extent than the hub of the wheel, then either excessive clamping is observed, which can deform the hub plastically or even split it apart, or else relaxing of the clamping is observed, which can lead to the wheel slipping relative to the shaft, thereby preventing normal 10 transmission of the torque between the two elements. Axially, such differential expansion can cause warping by buckling of the shaft or of the hub of the wheel, such deformations causing imbalance resulting in vibration that adversely affects operation of the 15 assembly as a whole. SUMMARY OF THE INVENTION Objects assigned to the present invention are therefore to remedy the above-mentioned drawbacks and to 20 propose a novel device designed to drive a fluid in motion or to be driven by a fluid in motion, and in which the assembly of the wheel onto the shaft is particularly robust, reliable, and insensitive to phenomena of expansion of the parts, in particular when they operate 25 at high temperatures, or at high temperature gradients. Another object assigned to the invention is to propose a novel device of structure and of operation that are particularly stable and balanced. Another object assigned to the invention is to 30 propose a novel device that is resistant to wear and that offers excellent longevity. Another object assigned to the invention is to propose a novel device having behavior, in particular in the event of exposure to large temperature variations, 35 that is particularly predictable, controllable, and reversible. 4352309_1 (GHMatters) P93775.AU 4 Another object assigned to the invention is to propose a novel device that is of structure that is simple and reliable, and in which manufacture, assembly, and maintenance are particularly quick and easy, and as 5 inexpensive as possible. Another object assigned to the invention is to propose a novel device that is particularly strong and in which assembly remains functional, safe, and friendly to the parts, regardless of the operating conditions, both 10 under transient conditions and under steady-state conditions. Another object assigned to the invention is to propose a novel device in which assembly is reversible and the component parts are readily removable and 15 replaceable. Another object assigned to the invention is to propose a novel device that makes it possible to transmit high torque between the wheel and the shaft. Finally, an object of the present invention is to 20 propose a method of assembling a wheel on a shaft that guarantees that the wheel is secured to the shaft effectively and in manner that is friendly to the parts, while also not being affected by expansion phenomena. The objects assigned to the invention are achieved 25 by means of a device designed to drive a fluid in motion or to be driven by a fluid in motion, such as a fan, a pump, or a turbine, said device including at least one wheel that is designed to co-operate with said fluid in order to drive it or to be driven by it, said wheel being 30 fastened to a shaft, itself mounted to move in rotation about an axis of rotation (X-X'), the wheel being fastened to the shaft by being clamped between first and second thrust members that are retained by said shaft and that are urged axially towards each other, said device 35 being characterized in that the first thrust member has, against the wheel, a first thrust surface that is substantially conical and that is substantially carried 4352309_1 (GHMatters) P93775.AU 5 by a first generator cone having its vertex or "first focus" pointing towards the second thrust member with the half-angle at its vertex being greater than the angle of adhesion corresponding to the coefficient of friction 5 between said first thrust surface and the wheel. The objects assigned to the invention are also achieved by means of a method of assembling a wheel designed to co-operate with a fluid to drive said fluid or to be driven by it onto a shaft that is mounted to 10 move in rotation about an axis of rotation (X-X'), said method being characterized in that it includes a clamping step during which the wheel is held stationary on the shaft by clamping said wheel between first and second thrust members that are urged axially one against the 15 other, the first thrust member having, against the wheel, a substantially conical first thrust surface that is substantially carried by a first generator cone having its vertex or "first focus" pointing towards the second thrust member with the half-angle at its vertex being 20 greater than or equal to the angle of adhesion corresponding to the coefficient of friction between said first thrust surface and the wheel. BRIEF DESCRIPTION OF THE DRAWINGS 25 Other objects, characteristics and advantages of the invention appear in more detail on reading the following description, and from the accompanying drawings, given merely by way of non-limiting illustration, and in which: - Figure 1 is a partially cutaway fragmentary 30 perspective view showing a variant embodiment of a device of the invention of the fan type; - Figure 2 is a side diagram showing the principle of dimensioning the conical taper of the thrust member of the invention; 35 - Figure 3 is a fragmentary view in axial section showing the device of Figure 1; 4352309_1 (GHMatters) P93775.AU 6 Figure 4 is a diagram showing the operating principle enabling the assembly of the invention to accommodate expansion and to go from a contracted configuration to an expanded configuration; 5 - Figures 5 to 9 are axial section views showing a plurality of possible configurations for thrust members in devices of the invention; - Figure 10 is a diagram showing the effects of modifying the focuses of the thrust members, when the 10 coefficient of linear expansion of the shaft is less than that of the wheel; - Figures 11 and 12 are fragmentary views in longitudinal section showing the interference and separation phenomena corresponding to the effects 15 explained in the diagram of Figure 10. - Figure 13 is a partially cutaway fragmentary perspective view showing an example of a device of the invention being assembled; - Figure 14 is a diagram in a fragmentary side view, 20 showing the wedging phenomenon of a coupling key; - Figure 15 is an axial section view showing a variant embodiment of a device of the invention including two stepped bi-conically tapering thrust members, having focuses that coincide; and 25 - Figure 16 is a geometrical diagram showing the principle of the effect on the assembly of a difference between the real expansion focus and the focus of the thrust member in question, when, for example, the increase in temperature is substantially uniform between 30 the shaft and the wheel while the coefficient of linear expansion of the shaft is greater than the coefficient of linear expansion of the wheel. BEST MANNER OF IMPLEMENTING THE INVENTION 35 The present invention relates to a device 1, of the rotary machine type, including at least one wheel 2 fastened to a shaft 3, said shaft being itself mounted to 4352309_1 (GHMatters) P93775.AU 7 move in rotation, e.g. on bearings (not shown), about an axis of rotation (X-X'), said device 1 requiring coupling between said wheel 2 and said shaft 3 that is sufficiently stable and strong to enable at least 5 transmission of drive torque between these two elements about said axis of rotation (X-X'). More particularly, said device 1 is designed to be exposed to a fluid, and preferably immersed therein, so that it can either drive said fluid in motion, the wheel 10 2 being driven by the shaft 3 so as to generate a fluid stream V, it then being possible for said device 1 to constitute a fan, a circulator, an extractor, a pump, etc., or be driven by said fluid in motion, the wheel 2 collecting the energy from the fluid stream V to drive 15 the shaft 3 in rotation, it then being possible for the device 1 to constitute, for example, a generator of the turbine type that is propelled by wind, water, or marine currents, etc. Naturally, the device 1 may be arranged to generate 20 or to collect a fluid stream V that may either be substantially linear and preferably substantially parallel to the axis of rotation (X-X'), so as to approach the wheel head-on, as in the variants shown in the figures, or so as to approach the device in a manner 25 substantially transverse to the axis (X-X') and preferably substantially tangential to the wheel. Naturally, the wheel 2 is designed to co-operate with said fluid in order to drive it or to be driven by it, said wheel 2 preferably having, for this purpose, a 30 plurality of blades 4 connected to a central hub 5, said hub being provided with a bore 6 enabling it to be engaged over the shaft 3. In order to guarantee the mechanical cohesion between the shaft 3 and the wheel 2, said wheel 2 is 35 fastened to said shaft 3 by being clamped between first and second thrust members 10, 11, said first and second thrust members 10, 11 being retained by the shaft 3, the 4352309_1 (GHMatters) P93775.AU 8 thrust members advantageously having the axis of rotation (XX') passing through them and being urged axially towards each other. The wheel 2 is thus advantageously maintained by 5 clamping, by being compressed between said first and second thrust members 10, 11, which members preferably come to exert their action in contact, preferably exclusively, with the edge faces of the hub 5 on either side thereof. 10 Naturally, the assembly of the invention may be adapted depending on the level of torque to be transmitted between the wheel 2 and the shaft 3, regardless of whether said torque results from steady state rotary drive or from inertia phenomena related to 15 the masses of and to the speeds of rotation of the parts (in particular of the wheel 2) during acceleration or braking stages. Thus, although it is predictable that the maximum torsional moment that tends to cause the wheel to pivot 20 about the shaft will be low, e.g. when the device is a lightweight device rotating at moderate speed and not exposed to sudden accelerations or stops, it is not impossible that the wheel 2 will be blocked by losing its degree of freedom to rotate about the shaft 3 merely as a 25 result of the opposing axial clamping from the thrust members 10, 11, by friction under stress between the wheel 2 and each of said thrust members 10, 11. Optionally, the geometrical shape of the thrust members 10, 11, the choice of the component materials of 30 the parts, and the intensity of the axial clamping force exerted by them on the wheel 2 are adapted accordingly. However, in particularly preferred manner, the axial clamping between the thrust members is aimed mainly, or indeed almost exclusively, at keeping the axes of the 35 wheel 2 and of the shaft 3 substantially in coincidence, the assembly that results merely from clamping by urging the thrust members 10, 11 axially towards each other 4352309_1 (GHMatters) P93775.AU 9 being designed to withstand the lateral forces, of the dynamic imbalance type, that might cause the wheel 2 and/or the shaft 3 to move radially, while the device may also include auxiliary coupling means 40, e.g. comprising 5 one or more keys, as described in detail below, said coupling means 40 being designed to reinforce the assembly and to transmit torque, optionally very high torque, e.g. approximately in the range 1000 (one thousand) newton meters (N.m) to 10,000 (ten thousand) 10 N.m, from the shaft 3 to the wheel 2 (or vice versa). Naturally, it is possible to secure the wheel 2 to the shaft 3 while removing substantially any degree of freedom between these elements, in particular by preventing any relative movement in rotation about the 15 axis (X-X'), and also, preferably by preventing any relative movement in translation of the wheel as a whole along said axis. The first and second thrust members 10, 11 may naturally be retained on the shaft 3, advantageously in 20 separate manner, by any suitable means designed to prevent, or at least to limit them moving apart relative to each other, and therefore to prevent or at least to limit loosening of the wheel, said thrust members being, for example, formed by separate removable elements 25 mounted on the shaft, such as threaded rings. However, preferably, at least one of the thrust members, and, by convention below, the second thrust member 11 is formed integrally with the shaft 3, and, for example, is machined or forged to form a shoulder that 30 may be straight (collar) or inclined (frustoconical). Advantageously, the continuity of the material guarantees the strength and permanence of the thrust procured by said thrust member 11, while removing any risk of play. It also procures a reference abutment that 35 simplifies mounting the wheel on the shaft and that optionally guarantees that assembly is reproducible. 4352309_1 (GHMatters) P93775.AU 10 In accordance with an important characteristic of the invention, the first thrust member 10 has, against the wheel, a substantially conical first thrust surface 12 that is substantially carried by a first generator 5 cone C 12 having its vertex F 12 or "first focus" pointing towards the second thrust member 11, and having the half angle at its vertex a 12 greater than or equal to the angle of adhesion P12/2 corresponding to the coefficient of friction between the first thrust surface 12 and the 10 wheel 2. Advantageously, such a conical taper makes it possible substantially to maintain the clamping force of the first thrust member 10 against the wheel 2, and more particularly the axial load component of said clamping 15 force, while also, in the event of dimensional variation of the wheel 2 relative to the shaft 3 and/or relative to the first thrust member 10, e.g. under the effect of thermal expansion, allowing the wheel to slide along the first thrust surface 10, at the contact interface created 20 and maintained by the axial load between said wheel 2 and said first thrust member 10. In other words, the first generator cone C 12 is more open than the adhesion cone associated with the pair {first thrust surface 12; wheel 2}, as shown in Figure 2, 25 so as to enable the assembly to accommodate any dimensional variations in these parts. The term "angle of adhesion", generally referenced p in Figure 2, designates the angle of inclination, relative to the normal to the thrust surface 12, of the 30 reaction R of the support that, due to the existence of friction, opposes any relative movement of the wheel 2 by sliding on said thrust surface. The coefficient of friction corresponds to the tangent of said angle of adhesion p, i.e. to the ratio of 35 the tangential component T to the normal component N of the reaction R of the support. 4352309_1 (GHMatters) P93775.AU 11 It can readily be understood that, in order to avoid the parts jamming by chocking or seizing, i.e. in order to allow the wheel to slide relative to the first thrust member 10 (or conversely, to allow the thrust member, 5 carried by the shaft, to slide relative to the wheel), e.g. under the effect of radial shrinkage FR of the hub 5, or, conversely, of radial expansion of the shaft and of the first thrust member 10, it is necessary for the angle of inclination of the thrust surface 12 relative to the 10 axis of rotation (XX'), i.e. the half-angle at the vertex (referenced a in Figure 2) of the corresponding generator cone, to be sufficiently large, and in particular greater than or indeed much greater than said angle of adhesion p. 15 In addition, in analogous manner, the half-angle at the vertex a is advantageously less than or equal to the angle complementary to said angle of adhesion , i.e. less than or equal to -- p. 2 This configuration makes it possible to guarantee 20 the possibility of relative sliding movement of the wheel on the thrust surface 12 to accommodate axial stresses, e.g. if the hub 5 expands, thereby exerting on the shaft 3, via the thrust members 10, 11, a traction force or, conversely, if the shaft contracts, thereby compressing 25 the hub 5. Thus, the half-angle at the vertex a, a 12 of the generator cone lies substantially within the range [aMIN, aAX] where aMIN is greater than or equal to, or indeed is strictly greater than p, and amAx is less than or equal 30 to, or indeed is strictly less than -- p. 2 Advantageously, these constructional provisions enable the device, and more particularly the subassembly formed by the wheel assembled onto the shaft to accommodate dimensional variations in its component 4352309_1 (GHMatters) P93775.AU 12 parts, and in particular the effects of differential volume expansion of said parts. As shown in Figure 4, the dimensional variations, both axial and radial, that accompany going from a 5 contracted configuration shown in uninterrupted lines to an expanded configuration, shown in dashed lines, are absorbed by the relative movement, and more particularly by the relative sliding of the contact surface of the hub 5 over and along the first conical thrust surface 12, 10 without causing any destructive excess stress. To be safe, instead of setting the conical taper limits amino, amax as a function of the exact value of the angle of adhesion p, it is possible to set them as a function of a value that is strictly greater than said 15 angle adhesion, e.g. greater than or equal to 2 x p, or indeed greater than or equal to 3 x p. Applying such safety factors makes it possible to ensure that the contact interface between the wheel 2 and the thrust member 10 is sufficiently steeply inclined, regardless of 20 the stress direction, to guarantee that functional slip appears under all predictable operating conditions, and in particular to guarantee that the relative movement of the parts in the "go" direction (expansion) and in the "return" direction (contraction) is reversible. 25 Optionally, the reference angle of adhesion p is considered to be the value corresponding to the predictable maximum of the coefficient of friction value(s) that can occur during operation of the device, which values can, in particular, depend on the 30 predictable surface state, and in particular wear, of the parts, and on operating temperature. Although it is possible to make provision to use a lubricant, between the wheel and the first thrust member, e.g. a high-temperature lubricant of the graphite-copper 35 solid lubricant type, it is the dry coefficient of friction that is preferably taken into account in order to determine the thrust taper angle. 4352309_1 (GHMatters) P93775.AU 13 As shown in Figure 5, and subject to such an arrangement being compatible with the required accuracy as regards making the axes of the wheel and of the shaft coincide, and with the wheel 2 being held radially and 5 more generally with the behavior of the device 1 in the face of dynamic radial stresses, it is possible for the second thrust member to form merely a shoulder that is substantially radial, i.e. that is not inclined relative to the axis, with only the first thrust member having a 10 conical shape making it capable, on its own, of accommodating expansion. Geometrically, such an arrangement can be considered as corresponding to a situation in which the second thrust member 11 has a thrust surface carried by a 15 generator cone that is substantially flattened, of half angle at the vertex equal to n/2. In such a situation, the first focus F 12 is then preferably axially situated substantially, or indeed exactly, in register with said shoulder. 20 However, in particularly preferable manner, the second thrust member 11 has, against the wheel 2, a second thrust surface 13 that is substantially conical, that is opposite relative to the first thrust surface 12, and that is substantially carried by a second generator 25 cone C 13 , having its vertex F 13 or "second focus" pointing towards the first thrust member 10, and having the half angle at its vertex a13 greater than or equal to, or indeed strictly greater than, the angle of adhesion 913/2 corresponding to the coefficient of friction between said 30 second thrust surface 13 and the wheel 2. The first thrust member and the second thrust member can thus form frustoconical elements that penetrate in opposite directions into the hub 5, preferably by coming to bear respectively against first and second reentrant 35 seats 14 and 15 that are substantially complementary to the shape of the first and second thrust surfaces, and more particularly substantially frustoconical. Contact 4352309_1 (GHMatters) P93775.AU 14 is preferably end-on surface-on-surface contact in order to procure stable thrust and clamping pressure distributed over a large load-bearing surface area, and in a manner that is substantially uniform all the way 5 around the axis of rotation. Advantageously, putting in place a carrying and clamping system of the "X-shaped" bi-conically tapering type facilitates centering the hub 5 on the shaft 3, and therefore balancing the wheel 2, while also distributing 10 the absorption of the dimensional variations on either side of the wheel, each thrust member 10, 11 being capable of absorbing its share of expansion by allowing the wheel to move locally relative to its thrust surface 12, 13, thereby ensuring that the assembly behaves 15 uniformly, reproducibly, and reliably. Preferably, the first and second focuses F 12 , F 13 lie axially between the first thrust surface 12 and the second thrust surface 13. In other words, the "focal distance" of each 20 generator cone C 12 , C 13 is preferably less than or equal to the support span of the shaft d 3 lying axially between the contact zone in which the wheel 2 is in contact with the first thrust member 10 and the contact zone in which said wheel 2 is in contact with the second thrust member 11, 25 said support span defining the segment of the shaft 3 in which axial and/or radial dimensional variations can affect the assembly, and in particular the stress state of the wheel. Preferably, the half-angle at the vertex a 12 of the 30 first generator cone C 12 , or, respectively, the half-angle at the vertex a 1 3 of the second generator cone C 13 , lies substantially in the range 30 to 60', and preferably lies in the range 400 to 50', or indeed is substantially equal to 45'. 35 Advantageously, in addition to facilitating relative sliding of the parts, such a provision, makes it possible to apply to the wheel 2 a clamping force that is 4352309_1 (GHMatters) P93775.AU 15 particularly well proportioned and in which the working axial compression component can be particularly high and easy to adjust, while, proportionally, its radial component remains moderate. 5 Naturally, the characteristics of the second thrust member 11 can be deduced mutatis mutandis and independently from one another from all or some of the characteristics of the first thrust member 10. In addition, in order to guarantee the device is 10 balanced and in order to avoid imbalance and vibration, said device, and more particularly the shaft 3, the wheel 2, the thrust members 10, 11 and more generally the assembly are preferably bodies of revolution, or at least are invariant in rotation, about the axis (X-X'). 15 Advantageously, the first generator cone C1 is centered on the axis of rotation (X-X'). Advantageously, the second generator cone C 13 is also centered on the axis (X-X'). More particularly, the first and second generator 20 cones C 12 , C 1 3 are advantageously in mutual alignment and centered on the axis of rotation (X-X'), their respective focuses being situated on said axis. The conical tapers of the first and of the second thrust members, and the configurations of the first and 25 of the second focuses F 12 , F 13 , may have variations, as shown, in particular as shown in Figures 5 to 9 without going beyond the ambit of the invention. Preferably, as shown in Figures 6 and 7, the first focus F 12 and the second focus F 13 substantially coincide. 30 In other words, the first and second generator cones

C

12 , C 13 preferably converge towards a common vertex. In this way, the sum of their respective focal distances d 12 , d 13 , each equal to the height measured axially between the vertex of the cone and the base plane 35 intersecting the axis of rotation (X-X') and containing the base ring marking the axially innermost contact made by the hub 5 against the first and second thrust surfaces 4352309_1 (GHMatters) P93775.AU 16 12, 13, respectively, is advantageously substantially equal to the support span d 3 of the shaft lying between said thrust surfaces, i.e. d 3 = dl+d13. Advantageously, such a provision makes it possible, 5 in a manner that is substantially exact, at least at constant temperature, or with slowly varying temperature, to compensate for the expansion of the entire support span of the shaft d 3 , i.e. to adapt the reaction of the device to the exact dimensions of the assembly, both 10 axially and radially. As shown, in particular in Figure 4, it can be observed that, on either side of the focal plane PF, i.e. of the plane that is normal to axis of rotation (X-X'), that contains the focus(s) F 12 , F 13 in question, the 15 tangent of the half-angle at the vertex a 12 , a 13 , that corresponds to the slope of the thrust surface 12, 13 in question, is substantially equal to the ratio 1 where d12

R

12 represents the radius measured between the axis of rotation (X-X') and the point at which the hub 5 meets 20 the thrust surface 12, and where d 12 represents the axial distance of said point from the focus. Thus, regardless of the respective values of the coefficients of linear thermal expansion of the shaft and of the hub, whether they are equal or different, the 25 movement of any point of the seat 14 and of the hub 5 relative to the first thrust member 10, or conversely of any point of the first contact surface 12 relative to said first seat 14, takes place along said slope, so that the wheel can slide locally along said first thrust 30 member, by moving up or down the slope, without interfering with said thrust member and without, conversely, becoming detached therefrom. Therefore, it is advantageously possible to keep axial clamping that is substantially constant and having 35 stresses that are neither too accentuated, nor too relaxed by differential expansion effects. 4352309_1 (GHMatters) P93775.AU 17 As shown in Figure 4, if consideration is given to a point A belonging to the hub that expands relative to a focus F 12 , F 1 3 in question until it reaches a point A', the axial component 6A, and the radial component 6R of the 5 vector AA' are respectively proportional to the radius at which said point A is situated relative to the axis of rotation (X-X') and proportional to the axial distance of said point A relative to the focal plane PF, said vector AA being collinear with the generator line of the first 10 cone a 12 intersecting said point A. Thus, the invention makes it possible to ignore dimensional variations related to the linear differential expansion between the shaft 3 and the wheel 2, in three dimensions, by means of conical thrust members 10, 11 15 having focuses that coincide on the axis of rotation and that thereby define a common expansion focus from which all of said dimensional variations, both of shaft and of the wheel, radiate. Accommodating these dimensional variations takes 20 place by relative sliding between the seats of the hub and the thrust surfaces presented by the shaft, substantially without modifying the positions of these components or modifying the axial loading. Preferably, in substantially analogous manner or 25 indeed in substantially symmetrical manner, the same applies at the coupling between the opposite portion of the hub 5 and the second thrust member, it thus being possible for the wheel 2 to "swell" around the shaft 3 and then to return to its initial position, or vice 30 versa, it being possible for the shaft 3 to expand or to contract in the hub, in particular substantially as a dilatation relative to the center of the support span d 3 , it being possible for the principle shown in the diagram of Figure 4 to apply mutatis mutandis to each interface 35 between a thrust member 10, 11 and the wheel 2, and depending on the respective coefficients of expansion and 4352309_1 (GHMatters) P93775.AU 18 on the respective temperatures of each of the parts in question. Ideally, the parts (wheel and corresponding thrust member) thus move freely by surface sliding with friction 5 over the same slope predefined by construction, in one direction (expansion) and in the other direction (contraction), while inducing substantially no significant increase nor any significant relaxing of the axial compression working stress, thereby avoiding losing 10 the operating clamping without however exposing the assembly to degradation by deformation or breakage. By way of example, if consideration is given to behavior of the parts as shown in Figure 4, applied to one of the assembly configurations corresponding to 15 Figures 3, 6, or 7, the hub 5 can, when it heats up, undergo a volume expansion, both axially and radially, starting from a contracted configuration (shown in uninterrupted lines in Figure 4), and therefore become longer and wider while seeing its corresponding 20 dimensions increase relative to the dimensions of the shaft and of the abutment members 10, 11 on which it rests. The surface of the first seat 14 can move up the slope of the first conical thrust surface 12 (leftwards 25 in said figures), or, respectively, the surface of the second seat 15 can move up the slope of the second thrust surface 13 (rightwards), it thus being possible for the axial ends of the wheel to move apart freely from each other under the effect of the expansion, in particular 30 axially, each moving away from the focal plane that corresponds to it, optionally in a manner substantially symmetrical about the same focal plane PF (Figures 3, 6, and 7), until said ends reach a position corresponding to the expanded configuration (shown in dashed lies in 35 Figure 4), in which said ends go beyond the gauge plane attached to the shaft 3 and facing which they initially find themselves in the contracted configuration. 4352309_1 (GHMatters) P93775.AU 19 Particularly preferably, as is shown in Figures 3 and 6, the focal plane PF may be substantially centered axially on the support span of the shaft d 3 , and/or may substantially coincide with the midplane of the wheel 2, 5 and more particularly of the hub 5, which midplane is perpendicular to the axis of said wheel and subdivides said wheel, or, respectively, its hub, substantially into two equal halves. In this configuration, the two generator cones C 12 , 10 C 13 are advantageously opposite via their vertices and have angles at their vertices that are equal. However, it is not impossible for the focal plane PF to be offset towards one or the other of the thrust members relative to the center of the support span d 3 of 15 the shaft and/or relative to the midplane of the wheel, as is shown in Figure 7, the first and second generator cones then having angles at their vertices that are of distinct values. In other variant embodiments, the first focus F 1 2 and 20 the second focus F 13 may be remote from each other axially, the first and the second generator cones C 12 , C 13 being either separate, as shown in Figure 8, so as to cover, together, only a fraction of the total support span d 3 between the first thrust surface 12 and the second 25 thrust surface 13, while allowing a non-covered fraction A' to remain, or, conversely, as shown in Figure 9, overlapping in such a manner as to cover redundantly at least a fraction A of said total support span d 3 . The defocusing distance axially separating the first 30 focus from the second focus is referenced A (delta), said distance being referenced either negatively A (delta negative) to designate an interfering overlap of the generator cones, or referenced positively A+ (delta positive) to designate that said cones are disunited. 35 When A is zero, the focuses coincide. The provision consisting in choosing the focal distance (s) d 12 , d 13 of the generator cone (s) C 12 , C 13 in 4352309_1 (GHMatters) P93775.AU 20 such a manner that their cumulative value (or individual value when only one of the thrust members is conical) is strictly less than (delta positive) or, conversely, strictly greater than (delta negative) the total support 5 span d 3 , makes it possible to facilitate either a phenomenon of under-compensation, in which the relative expansion of the parts is not sufficiently compensated and causes interference between the wheel 2 and the thrust member 10, 11 in question, or, conversely, a 10 phenomenon of over-compensation that tends to facilitate relaxing of the compression constraints between the two parts, in the direction of separation of the contact surfaces of said parts. Advantageously, in the first above situation, the 15 clamping force is facilitated, in order to improve penetration, centering, and stiffness of the blocking of the wheel on the shaft. Conversely, in the other above situation, if concern exists that friction and phenomena of wear that are too 20 large might appear, attempts are made to minimize them by reducing the contact pressures in order to avoid any accidental binding or seizure of the wheel 2 on its thrust members 10, 11. The choice of focal length for the generator cones 25 depends on the desired behavior, and also on the respective values of the coefficients of linear expansion of the wheel 2 and of the shaft 3, and finally on the thermal stress conditions of the assembly. Figure 10 diagrammatically shows these phenomena, 30 assuming that the coefficient of expansion of the wheel 2 and more particularly of the hub 5, is greater than the coefficient of expansion of the shaft 3, and that the temperatures of the two elements are substantially identical. 35 Naturally, it is quite possible, and indeed preferable, for the coefficient of expansion of the component material of the shaft to be greater than the 4352309_1 (GHMatters) P93775.AU 21 coefficient of expansion of the hub, and then, at identical temperature, the phenomena described below are reversed, the reasoning remaining analogous. The same could also apply, subject to the coefficient of expansion 5 values, if the temperature of the shaft is very much higher than the temperature of the wheel, e.g. because of said wheel cooling rapidly after a long cycle of hot operation. With reference to Figure 10, if consideration is 10 given firstly to the top portion of the figure, in which portion the focal length of the first cone C 12 is shorter than the length LO of the segment of the assembly that is affected by the expansion (with, for example LO = d 3 /2 in the variants of Figures 6, 8 and 9), it can be observed, 15 by geometrically constructing the theoretical movement to which an edge segment of the part lying between two points A and B would be subjected, depending on whether said points belong to the wheel 2 or, conversely, to the shaft 3, that, instead of causing neutral sliding, said 20 expansion causes interference 20, i.e. a virtual penetration of the envelope of the wheel 2 into the envelope of the shaft 3, as shown in Figure 11. In practice, it can be understood that such a situation could result in a major increase in the 25 stresses in said zone, or indeed in plastic deformation of the parts. For reasons of clarity and for convenience of description, the points respectively belonging to the wheel 2 and the shaft 3 are respectively given the 30 subscript 2 and the subscript 3. In addition, when a letter designates a point of the part in the contracted configuration of said part, the prime symbol (') is added to the letter designating the arrival point corresponding to the expanded 35 configuration. Geometrically, for example, the following vector relationship applies: OA' 3 =(1+a 3 xAT).OA 3 where a 3 4352309_1 (GHMatters) P93775.AU 22 represents the coefficient of linear expansion of the shaft 3 and AT represents the variation in temperature. Conversely, when the focal length of the cone C 12 is greater than the length Lo of the segment that is affected 5 by the expansion, in such a manner that said cone converges beyond the reference plane situated axially at said distance LO from the initial thrust of the wheel on the thrust member, the expansion of the hub results in separation 21 of said hub, the envelope of the wheel 10 tending to separate and to move away from the envelope of the first thrust surface 12, as is shown in Figure 12. Figure 16 shows another geometrical illustration of the operating principle of the invention. The physical focus of the conical thrust member 10 15 in question is referenced Fe, the position of which point is determined by construction, and the real focus of expansion, from which point the expansion of the part in question takes place, is referenced FR. Reference LA, or respectively LB, designates the 20 straight line passing through the real focus FR and through a point A, or respectively a point B, of the load-bearing surface of the part in question (i.e. of the seat 14 of the wheel 2 or of the thrust surface 12 of the thrust member 10, considered to be the same as the shaft 25 3, for reasons of convenience), said point being situated at a radius RA, or respectively RB from the real focus, and shifting by a value dRA, or respectively dRB, during the expansion. Unless otherwise indicated, the same referencing conventions as in the preceding example are 30 used. Reference axA, or respectively aB designates the angle formed by the straight line LA, or respectively LB, and the axis of rotation (X-X'), and reference ap designates the half-angle at the vertex of the generator cone of the 35 thrust member lying between said axis (X-X') and the generator line Le. 4352309_1 (GHMatters) P93775.AU 23 Reference A/2 also designates the axial gap between the physical focus Fe and the real focus FR, it being possible advantageously for said gap to correspond to the defocusing half-distance defined above, if it is 5 considered that the real focus in question is situated half-way between the two physical focuses corresponding to the physical focuses of the thrust members 10, 11, and more particularly in the midplane of the wheel. When the gap A/2 is zero, FR coincides with Fe, and 10 thus the angles aA and up (or respectively aB and ap) are identical (the system is almost perfectly focused). The real expansion then takes place by exact sliding of the surfaces of the wheel 2 and of the thrust member along the straight line LA, coinciding with the straight line LB 15 and the generator line Le of the generator cone. The slope of the thrust surface thus accommodates exactly and proportionally the axial component and the radial component of the expansion. When said gap A/2 is not zero, the system is 20 defocused and the angles aA and ap are different. The ratio between the real axial expansion and the real radial expansion then no longer corresponds to the theoretical ratio offered by the thrust member, the effective axial accommodation capacity of the assembly 25 then no longer being the same as the radial accommodation capacity. Reference VR designates the "knocking value" corresponding to the (normal) distance that theoretically, after expansion, separates the contact 30 surface 12 from the seat 14, which distance is positive in the event of separation and negative in the event of interference. However, such knocking represents a virtual phenomenon that can advantageously be compensated by 35 implementing a compensation system 25 as described below, it then being possible for interference, as in Figure 11, to result in the moving first thrust member 10 moving 4352309_1 (GHMatters) P93775.AU 24 backwards axially (away from the second thrust member) with an increase in the initial axial elastic loading, and, conversely, it being possible for an increase in play, as shown in Figure 12, to result in said first 5 thrust member 10 moving forwards, with a reduction in said initial axial elastic loading. The knocking value VR is proportional to the difference between the respective linear expansions of the parts and the distance p corresponding to the length 10 of the segment that is orthogonally lowered from the real focus FR on the generator line Le of the thrust member (counted positively in this example when the focal length of the thrust member is shorter than the real focal length). 15 With reference to Figure 16: For the shaft 3: UA = dRA 3 x sin (ap - aA) = (a 3 x AT 3 x RA) x sin (ap - aA) = a 3 x AT 3 x pV and: 20 UB = dRB 3 x sin (ap - aB) = (a 3 x AT 3 x RB) x sin (ap - aB) = a 3 x AT 3 x pV For the wheel 2: VA = dRA2 x sin (ap - aA) = (a 2 x AT 2 x RA) x sin (ap - aA) = a 2 x AT 2 x p 25 and: VB = dRB2 X sin (ap - aB) = (a 2 x AT 2 x RB) x sin (ap - aB) = a 2 x AT 2 x p hence: VR = UA - VA = UB - VB = (a 3 x AT 3 - a 2 x AT 2 ) x p 30 In the example shown in Figure 16, in which it is considered, in particular that a 3 > a 2 (and more particularly that a 3 = 3 x a 2 ) , since each expansion of the parts undergoes a temperature variation that is substantially equal (AT 3 = AT 2 ) this leads to separation 35 of the shaft and of the hub 5. If necessary, in the radially innermost portion of the thrust member 10 connecting the operating thrust 4352309_1 (GHMatters) P93775.AU 25 surface 12 to the central body 10' of said thrust member, it can be advantageous to provide an optionally rounded setback 10" that makes it possible to preserve a central body that is relatively solid, strong, and stable, while 5 also allowing the wheel 2 to come into contact with said thrust surface 12, even if said thrust surface is of small dimensions, and to move relative to said thrust surface. The inventors have also observed that, although 10 implementing conical thrust members 10, 11 advantageously enables the system to self-adapt to accommodate the relative dimensional variations between the parts, and, in particular the relative dimensional variations of the wheel and of its hub 5 relative to the shaft 3 and to the 15 thrust members 10, 11, in particular under steady-state conditions, during which each part is exposed to a substantially uniform temperature, it could be useful to perfect this adaptation capacity in order to procure finer regulation of the clamping, or indeed in order to 20 maintain axial clamping that is substantially constant also when the device is subjected to rapid temperature variations that generate thermal gradients within the same part. It can easily be understood that, on a support span 25 d 3 in question, the shaft 3, or respectively the hub 5, may present an internal temperature gradient, e.g. between its outer portions that are the most exposed to hot fluid, and its colder core, or, conversely, between certain outer segments that are cooled more rapidly by 30 applying a cold fluid while the core of the shaft is still hot, or finally between an upstream portion exposed to admission of the fluid, and a downstream portion that is cooled at the exhaust. So long as the temperature is not uniform and is not 35 stabilized over the entire support span, each portion of the shaft, and respectively of the hub 5, adopts its own mode and its own amplitude of expansion, depending on the 4352309_1 (GHMatters) P93775.AU 26 temperature at which it finds itself, so that over the support span as a whole, said expansion is distinct from the theoretical ideal expansion as a function of which the conical thrust surfaces 12, 13 are dimensioned and 5 pointed by construction. In practice, this creates, at least temporarily, a phenomenon equivalent to the above-mentioned phenomenon of "defocusing", causing, depending on the situation, under-compensation or over-compensation as described 10 above. In order to compensate for these phenomena, and thus in order to improve the dynamic thermal behavior of the device, in particular during optionally periodic rapid transient phases, during which the thermal environment of 15 the device is modified over a period shorter than its response time as regards assimilation or dissipation of heat energy, the inventors have made provision, in accordance with a characteristic that can constitute a separate invention, independently from the arrangement of 20 the thrust members, and in particular from their conical tapering, for the first or the second thrust member 10, 11 to be axially backed up, against the wheel 2, by an elastically deformable compensation system 25 that is interposed between the thrust member in question and an 25 abutment member 26 fastened to the shaft 3. By way of example, the abutment member 26 may be formed by a nut, of the type having notches, that may advantageously be prevented from moving in rotation by means of one or more clips 26' that radially connect a 30 notch formed in said nut to a corresponding indent provided in the shaft 3. Advantageously, the compensation system 25 acts as a spring having stiffness that is determined such that said spring can deform, either by compressing by contraction 35 in order to absorb over-stress caused by the interference of the wheel 2 against the thrust member 10, 11, or, conversely, by expanding to hold the thrust member 10, 11 4352309_1 (GHMatters) P93775.AU 27 pressed and compressed against the seat 14, 15 of the hub 5 in the event that thermal expansion tends to cause relaxing or indeed separating of the surfaces. Thus, it is possible continuously, and in fine and 5 reactive manner, to accommodate any defocusing resulting from a thermal gradient within the same part and causing non-uniform expansion that no longer coincides with the ideal slopes defined by the thrust member, while also maintaining a clamping force that is sufficient to hold 10 the wheel 2, in particular radially, but that is sufficiently moderate to avoid plastic deformation, premature wear, and, more generally, degradation of the parts and of the device 1. Thus, the assembly proposed tolerates and indeed 15 corrects dimensional variations that are non-uniform and/or of large amplitude of the wheel and of the shaft. Advantageously, as shown in the figures, the compensation system 25 can form a sort of "breechblock" that comes to bear against the face of the thrust member 20 10, 11 that faces away from the thrust surface 12, 13 that said thrust member presents to the wheel 2, the degree of nominal compression being determined as a function of the adjustment of the abutment 26, and more particularly of the tightening torque of the 25 corresponding nut. To this end, the clamping nut, and more generally, the thrust members, may be engaged over the shaft 3 by means of an anti-recoil threaded portion, of the "interrupted thread" type having its thrust surfaces 30 particularly steep, or indeed substantially radial. Preferably, the compensation system 25 includes at least a first axially deformable member 27 and a second axially deformable member 28, of the resilient washers or rings type, which washers or rings are stacked and 35 compressed axially. 4352309_1 (GHMatters) P93775.AU 28 In particularly advantageous manner, the first deformable member may have a stiffness less than the stiffness of the second deformable member 28. In other words, it is advantageously possible to 5 create a sort of stack comprising a "soft" washer having relatively low stiffness but a good elastic deformation amplitude, and at least one, and preferably two "hard" washers 28, 29 of stiffness and/or of thickness greater than the stiffness and/or thickness of the "soft" washer, 10 but of smaller maximum amplitude of movement. It is thus possible to create progressive differential compensation, the "hard" washers making it possible, so long as the axial dimension variation between the parts does not exceed a certain threshold, to 15 maintain a compression load that is relatively high, the "soft" washer supplying, if necessary, i.e. when said axial dimensional variation exceeds a usual threshold exceeding the capacity of the "hard" washers, a stroke that is sufficient to maintain the assembly as a whole 20 under axial stress, thereby avoiding relaxation that is too great and/or too sudden in the clamping, even though the residual holding stress is more moderate than the nominal holding stress. Naturally, the thrust member 10, 11 in question is 25 advantageously mounted to move in axial translation relative to the shaft 3, so that, in particular, it can move when stresses are exerted on one side by the dimensional variation of the hub 5 relative to the shaft 3, and on the other side by the compensation system 25. 30 Thus, more generally, the device preferably includes, on either side of the wheel 2, firstly a thrust member (the second thrust member 11 in this example) fastened to the shaft (at least axially, in the clamping direction), or indeed incorporated into said shaft, said 35 (second) thrust member procuring rigid and fixed thrust for said wheel, and secondly a thrust member (the first thrust member 10, in this example) urged against the 4352309_1 (GHMatters) P93775.AU 29 other thrust member and mounted to move under a resilient force (in the clamping axial direction in this example). In addition, the above-described compensation system 25 may naturally be advantageously adapted to fastening 5 any type of part (wheel, e.g. bladed or toothed wheel, pulley, hinge flap, etc.) to a pin or to a shaft. Preferably, the first thrust member 10 is formed by a frustoconical thrust ring 30, as shown in particular in Figures 1, 3, and 13, which ring is distinct from the 10 wheel 2 and from the shaft 3. Advantageously, this ring can come to form a wedge shaped thrust, preferably directly against the shaft 3 and against the first seat 14 provided in the hub of the wheel 5. 15 Preferably, the frustoconical ring 30 is angularly split up into at least two independent blocks 30A, 30B, and preferably into three independent blocks 30A, 30B, 30C, each of which preferably covers an angular sector that is substantially equal about the shaft 3. 20 The frustoconical ring 30 can thus be reconstructed by a succession of jaws, or its blocks can be totally separated, or optionally interconnected by flexible links, and, for example, distributed over about 120' each, thereby making it possible for each block to move, 25 if necessary, relative to the adjacent blocks, and, in particular to move away or towards said blocks, so that the ring 30 can freely accommodate the variations in perimeter caused by the expansion and contraction of the shaft. 30 In addition, said frustoconical ring 30 may have hinge slots 31 that are radially non-through slots, but that subdivide the ring, and more particularly the blocks 30A, 30B, 30C, e.g. with at least two slots per block, so as to make them easier to bend when it is necessary to 35 accommodate a change of radius of curvature of the shaft 3. 4352309_1 (GHMatters) P93775.AU 30 Advantageously, such hinge slots 31 may correspond to saw cuts that that crenellate the outside periphery of the ring 30, so that each block is formed of a chain of segments that are hinged together via their weakened link 5 zones. The ring 30 that is thus made more flexible can then continuously match the shape of the outside surface of the shaft 3 against which surface it comes to bear. Preferably, the compensation systems 25 and the 10 frustoconical ring 30 are secured together by tongue-and groove machining that avoids improper positioning of or radial leakage from the blocks 30A, 30B, 30C. Preferably, such securing takes place at a level close to the mean diameter of the first conical thrust 15 surface 12 or a little beyond that, in the upper half, i.e. in the radially outermost half, of the back of the frustoconical ring 30, so that the axial stress exerted by the compensation system 25 tends to press the sole of said ring 30 against the shaft 3 rather than separating 20 it therefrom by tilting, thereby reinforcing the assembly. In addition, as shown in Figure 4, it is remarkable that the abutment member 26 can procure substantially conical thrust for the compensation system 25, which 25 thrust follows a third generator cone C 26 having its vertex F 26 situated substantially in register with the junction where the compensation system 25 meets the thrust member 10 that it backs up. Advantageously, such a provision makes it possible, 30 in a manner analogous to the manner described above for the junction between the wheel and the thrust members, to compensate, if necessary, for the phenomena of expansion affecting the axial portion of the shaft that lies in the zone capped by the "breechblock" formed by the 35 compensation system 25. The entire axially captive (and stressed) portion of the shaft, lying firstly between the thrust members 10, 11, and then beyond that, to the 4352309_1 (GHMatters) P93775.AU 31 abutment member 26, is thus compensated for expansion, by means of a plurality of successive conical thrusts each covering a respective segment. In accordance with a characteristic that can 5 constitute a separate invention, in particular independently from the arrangement and from the conical tapers of the thrust members 10, 11, the first thrust member 10 and the second thrust member 11 can be designed to maintain the inside surface of the hub 5 of the wheel 10 2, i.e. the wall of its bore 6, away from the outside surface of the shaft 3 that faces it, and to do so over at least 50%, and preferably at least 75%, or indeed all of the support span lying between said thrust members 10, 11. 15 In other words, the thrust members 10, 11 may also optionally act as spacers making it possible to provide, at least initially, and preferably substantially to maintain radial clearance between the shaft 3 and the hub 5. 20 Advantageously, such operating clearance J, shown in particular in Figures 3 to 7, makes it possible to absorb, if necessary, the differential radial expansion between the shaft 3 and the hub 5, while avoiding any effect of clamping of the shaft 3 by said hub 5 that 25 could cause plastic deformation, or indeed cracking or splitting of the hub. Preferably, this clearance is in the form of a cylindrical chamber that extends over the entire support span d 3 of the shaft 3 that is defined between the thrust 30 members. Advantageously, such a provision also improves the self-centering procured by the conical thrust surfaces and makes it possible to stress the hub 5 essentially in axial compression so as to ensure it is held stationary, 35 no intermediate portion of the shaft coming to bear against, deflect, or hinder the positioning of the hub. 4352309_1 (GHMatters) P93775.AU 32 Preferably, the radial clearance J lies substantially in the range 1 millimeters (mm) to 4 mm and/or represents about 0.5% to 2% of the radius of the shaft 3. 5 Preferably, it is calculated, where appropriate, so that it can change, and in particular, decrease, so as to reach, under steady-state operating conditions, a predetermined level of clearance that is preferably less than the initial value of said clearance on assembly, or 10 indeed a predetermined level of operating tightness of fit making it possible to reinforce the securing between the shaft and the wheel. If it is desired to obtain such an effect when the temperature might rise while operation is starting, the coefficient of thermal expansion of the 15 shaft 3 is chosen to be greater than the coefficient of thermal expansion of the wheel 2. In addition, in accordance with a characteristic that can constitute a separate invention, the coupling means 40 may have at least one transverse element 40', of 20 the key type, that connects the first thrust member 10 to the wheel 2 at the first conical thrust surface 12, or, in particularly preferable manner, connects the second thrust member 11 to the wheel 2 at the second conical thrust surface 13, the thrust member 10, 11 in question 25 being itself prevented from moving in rotation on the shaft 3, or indeed formed integrally therewith, so that any movement in rotation of the wheel 2 relative to said thrust member 10, 11 and thus relative to said shaft 3 is prevented. 30 Advantageously, such a provision makes it possible to reinforce the fastening of the wheel and to transmit torque that is particularly high between the shaft and said wheel or vice versa. It is remarkable that this solution makes it 35 possible to distribute the torque transmission over a plurality of transverse elements, by limiting the concentrations of stresses, and by coming into engagement 4352309_1 (GHMatters) P93775.AU 33 on a relatively large and solid and thus particularly strong conical surface of the hub, unlike usual solutions that make the hub weaker over its entire length by providing it with grooves or with fluting. 5 In addition, the radial extension component of the transverse elements that are projecting and inclined relative to the axis advantageously increases the working lever arm relative to the surface of the shaft (and relative to the axis). 10 Furthermore, this end coupling advantageously makes assembly easy by it being by mere interfitting engagement, guided by the shaft itself. Preferably, as is shown in Figures 1 to 13, the transverse coupling element 40' is formed by a key, e.g. 15 a substantially rectangular block shaped key, a portion of which is designed to be received in a groove 41 provided in the conical surface of the thrust member 10, 11 in question, and the other portion of which is designed to emerge from said groove 41 and to engage in a 20 stop recess 42 that is substantially complementary, and that is provided in the corresponding portion of the wheel 2, said key being secured to the thrust member 10, 11, or indeed, respectively, to the wheel 5, e.g. by screw-fastening, in particular in order to avoid it 25 tilting during removal of the wheel. Fastening the key 40' to the end wall of the cavity of the groove 41 or of the stop recess 42 avoids causing said key to be raised and jammed by chocking, shown in Figure 14, which might otherwise prevent the thrust 30 member 10, 11 and the seat 15 from coming apart when it is desired to remove the wheel 2. In general, it is remarkable that the construction provisions of the invention advantageously make it possible to procure a reversible assembly whereby each 35 element, and in particular the wheel 2 and the first thrust member 10 or the compensation system 25 can be removed and replaced or fitted back in place. 4352309_1 (GHMatters) P93775.AU 34 In another variant embodiment, shown in Figure 15, the device may include a third thrust member 50 situated on the same side of the wheel 2 as the first thrust member 10, set back axially therefrom, and having, 5 against the wheel 2, a substantially conical third thrust surface 52, situated at a diameter greater than the diameter of the first thrust surface 12, and focused on the first focus F 12 . In particularly preferential manner, the device may 10 also include a fourth thrust member 51 having a substantially conical fourth thrust surface 53 situated set back from the second thrust member at a diameter greater than the diameter thereof. It is thus possible to obtain a structure having two 15 stepped bi-conically tapering rings having all of their conical thrust surfaces converging towards the same focus, so as to form two pairs of thrust surfaces disposed in an X-shape, each pair being stepped axially relative to the other, and being suitable for 20 withstanding the differential expansion of the parts. In general, the configuration and the dimensioning of the various elements is performed with reference to initial assembly performed at ambient temperature. However, it is possible to provide nominal 25 dimensioning, and in particular an arrangement of the conical thrust surfaces having its ideal configuration corresponding to the configuration of the assembly once it is brought to its operating temperature. It is remarkable that the device, and in particular 30 the materials and the various component parts of the device, may advantageously be designed to withstand, without being damaged, durable exposure to a fluid, and more particularly to a gas, that is at a temperature that is relatively high, and in particular greater than or 35 equal to 100C, 200 0 C, 500C, 700 0 C, or indeed 1000 0 C. The device is particularly suitable for "high temperature" applications and may, in particular, by way 4352309_1 (GHMatters) P93775.AU 35 of non-limiting example, be designed for extracting exhaust gases from combustion or incineration, or gases formed above molten baths in the mining or metallurgy industries, for generating electricity from a stream of 5 gas or of stream discharged by a furnace or by a boiler, or indeed for extracting or mixing hot reagents in the chemicals industry. It is also suited to any use in which it is exposed to durable temperature gradients, in particular between 10 the wheel and the shaft, or between the upstream portion and the downstream portion of the assembly relative to the direction of flow of the fluid, or indeed to optionally rapid temperature variations over time, the amplitude of which is of the order of larger than 100'C, 15 200 0 C, 500 0 C, 700 0 C, or even 1000 0 C. Naturally, the present invention also relates to a method of assembling a wheel 2 onto a shaft 3. Advantageously, said method includes a clamping step (a) during which the wheel 2 is held stationary on the 20 shaft 3 by clamping said wheel between firstly a first thrust member 10 and secondly a second thrust member 11 that are urged axially one against the other, the first thrust member having, against the wheel 2, a substantially conical first thrust surface 12 that is 25 substantially carried by a first generator cone C 12 having its vertex F 12 or "first focus" pointing towards the second thrust member 11, and having the half-angle at its vertex a12 greater than or equal to the angle of adhesion (P12/2 corresponding to the coefficient of friction between 30 the first thrust surface 12 and the wheel 2. Preferably, prior to said step (a), said method includes a pre-positioning step (b) during which the wheel 2 is engaged over the shaft 3, the shaft being free to move in rotation so long as the clamping has not been 35 performed. Advantageously, the wheel can slide along the shaft until it comes into abutment against the second thrust member, the stop recesses 42 coming to fit over 4352309_1 (GHMatters) P93775.AU 36 the coupling keys 40' that thus penetrate into engagement in the hub 5. During another stage of this pre-positioning step (b), the wheel 2 and the conical ring 30 are then fitted 5 over the shaft in succession, where applicable the ring being reconstructed by pre-assembling the blocks 30A, 30B, 30C over the circular groove of the washer 29 of the compensation system 25, and then said conical ring 30 is moved partially in translation until it comes into thrust 10 abutment against the seat 14 of the hub 5. It is then possible to perform the clamping progressively by engaging the abutment member 26 with the thread on the shaft 3, and then by tightening it so as to force the ring 30 into the hub 5, until a predetermined 15 tightening torque is reached that corresponds to the desired intensity of the clamping force in axial compression. In doing this, the compensation system 25 is pre stressed axially in compression, and said system is 20 compressed, thereby advantageously accumulating a stroke reserve that, if necessary, enables it to redeploy subsequently so as to compensate for any separation of the wheel relative to the thrust members, but while also preserving a margin of contraction compatible with the 25 maximum compression stresses acceptable by the hub, or respectively with the maximum traction stresses acceptable by the shaft 3. Generally, and independently of whether or not a compensation system 25 is present, the shaft 3 can thus 30 advantageously be used as a tie, stressed in traction, that connects, directly or indirectly, the first thrust member 10 to the second thrust member 11, by co-operating via specific and distinct securing with each of said thrust members 10 and 11, in order to stress said thrust 35 members in mutual compression towards each other. To this end, although said shaft may preferably constitute the only member withstanding all of the 4352309_1 (GHMatters) P93775.AU 37 traction load necessary for clamping the wheel between said thrust members, it is not impossible for consideration be given to putting in place other peripheral ties connecting the first thrust member 10 to 5 the second thrust member 11, e.g. of the nut-and-bolt type, so that said shaft withstands only a fraction, preferably a majority fraction, of the traction force resulting from the axial clamping. Advantageously, by forcing the two thrust members to 10 move closer together, and more particularly by forcing the first and second conical thrust surfaces 12, 13 to move closer together, firstly the wheel is caused to be centered relative to the shaft, and secondly the bore 6 is caused to settle some distance from the wall of the 15 shaft 3, it being advantageously possible for the clamping force to be exerted significantly and preferably to a majority extent along an axial component. It is remarkable that the pre-positioning step (b) and the clamping step (a) may preferably be implemented 20 while the shaft 3 is placed substantially vertically, in order to facilitate engaging and centering the wheel 2 on the shaft, and more particularly on the second conical thrust member 11, in particular under the effect of gravity, without having to compensate for any off 25 centering of the wheel 2 relative to the shaft 3, i.e. any non-uniform distribution of the operating clearance J between the hub 5 and the shaft 3, that would be caused by the weight of the wheel 2 if the mounting was performed while the shaft was placed horizontally. 30 In addition, the method of assembly is advantageously reversible, insofar as it limits or indeed prevents any direct adhesion contact between the shaft 3 and the wheel 2, the forces being borne via at least one removable thrust member 10, in which the contact surfaces 35 coming into contact with the shaft and with the wheel are relatively small, and which can, by means of the conical 4352309_1 (GHMatters) P93775.AU 38 taper that facilitates extracting it, be easily separated not only from the shaft 3 but also from the hub 5. Advantageously, the invention thus makes it possible to procure a rigid assembly that is particularly stable 5 and safe, suitable both for withstanding transverse imbalance and also for transmitting high torque, it being possible, in addition, for said assembly to be adapted to driving elements of large dimensions, that are heavy, and that have high inertia, all this with an axial clamping 10 force that is particularly moderate. In spite of these performance values, said assembly further remains reversible, needs only a small number of fastening elements, and is of relatively simple design, compact, or indeed lightweight compared with the scale of 15 implementation. It makes it possible, in addition, to accommodate the dimensional variations of the parts, regardless of whether they are relative variations between parts or non-uniform deformations in the same part, and regardless 20 of whether such variations result from thermal expansion or indeed hot centrifugal creep under the effect of the speed of rotation, and it does all this while maintaining appropriate, or indeed substantially constant clamping stress. 25 Advantageously, the type of assembly proposed further makes it possible to consider functionally associating materials having grades and properties that are very distinct, for forming the wheel and the shaft, and makes it possible, where applicable, to omit 30 refractory super-alloys that are particularly costly and difficult to work for manufacturing the shaft. By means of the invention, it is possible, in particular to procure fans of large dimensions, e.g. driving wheels of diameter of approximately in the range 35 0.5 meters (m) to 2 m or 3 m and of weight of approximately in the range 100 kilograms (kg) to over 1 metric tonne (t), or indeed 3 t, while exerting an 4352309_1 (GHMatters) P93775.AU 39 initial axial clamping force of approximately in the range 5000 decanewtons (daN) to 50,000 daN, said fans optionally being capable of working under extremely severe thermal conditions, without causing premature wear 5 or fatigue in the parts, which, in any event, can be removed and replaced separately, without damaging the remaining parts. SUSCEPTIBILITY OF INDUSTRIAL APPLICATION 10 The invention is industrially applicable to designing, manufacturing, and using industrial fans. 4352309_1 (GHMatters) P93775.AU

Claims

1. A device (1) designed to drive a fluid in motion or to be driven by a fluid in motion, such as a fan, a pump, or a turbine, said device including at least one wheel (2) 5 that is designed to co-operate with said fluid in order to drive it or to be driven by it, said wheel being fastened to a shaft (3), itself mounted to move in rotation about an axis of rotation (X-X'), the wheel being fastened to the shaft by being clamped between 10 first and second thrust members (10, 11) that are retained by said shaft and that are urged axially towards each other, said device being characterized in that the first thrust member (10) has, against the wheel (2), a first thrust surface (12) that is substantially conical 15 and that is substantially carried by a first generator cone (C 12 ) having its vertex (F 12 ) or "first focus" pointing towards the second thrust member (11) with the half-angle at its vertex (a 12 ) being greater than the angle of adhesion (P12/2) corresponding to the coefficient 20 of friction between said first thrust surface (12) and the wheel (2).

2. A device according to claim 1, characterized in that the second thrust member (11) has, against the wheel, a 25 second thrust surface (13) that is substantially conical, that is disposed in opposition relative to the first thrust surface (12), and that is substantially carried by a second generator cone (C 1 3 ), having its vertex or "second focus" pointing towards the first thrust member, 30 with the half-angle at the vertex (a13) being greater than or equal to the angle of adhesion (Y13/2) corresponding to the coefficient of friction between said second thrust surface and the wheel. 35

3. A device according to claim 2, characterized in that the first focus (F 12 ) and the second focus (F 13 ) substantially coincide. 4352309_1 (GHMatters) P93775.AU 41

4. A device according to claim 2, characterized in that the first focus (F 12 ) and the second focus (F 13 ) may be remote from each other axially, the first and the second 5 generator cones being either separate so as to cover, together, only a fraction of the total support span (d 3 ) between the first thrust surface and the second thrust surface, or, conversely, overlapping in such a manner as to cover redundantly at least a fraction (A-) of said 10 total support span.

5. A device according to any preceding claim, characterized in that the first generator cone (C 12 ), or, respectively, the second generator cone (C 1 3 ), is centered 15 on the axis of rotation (X-X').

6. A device according to any preceding claim, characterized in that the first and second focuses (F 12 , F 13 ) lie axially between the first thrust surface (12) and 20 the second thrust surface (13).

7. A device according to any preceding claim, characterized in that the half-angle at the vertex (a 12 ) of the first generator cone (C 12 ), or, respectively, the 25 half-angle at the vertex (a13) of the second generator cone (C 1 3 ), lies substantially in the range 30 to 60', and preferably lies in the range 40 to 50', or indeed is substantially equal to 45'. 30

8. A device according to any preceding claim, characterized in that the second thrust member (11) is formed integrally with the shaft (3).

9. A device according to any preceding claim, 35 characterized in that the first thrust member is formed by a frustoconical thrust ring (30) that is distinct from the wheel and that comes to form a wedge-shaped thrust 4352309_1 (GHMatters) P93775.AU 42 against the shaft (3) and against a first seat (14) of substantially complementary shape provided in the hub (5) of the wheel (2). 5 10. A device according to claim 9, characterized in that the frustoconical ring (30) is angularly split up into at least two and preferably three independent blocks (30A, 30B, 30C), each of which preferably covers a substantially equal angular sector about the shaft.

10

11. A device according to claim 9 or claim 10, characterized in that the frustoconical ring (30) has hinge slots (31), that are radially non-through slots, and that subdivide the ring so as to facilitate bending 15 of the ring when it is necessary to accommodate a change of radius of curvature of the shaft.

12. A device according to any preceding claim, characterized in that the first and second thrust members 20 (10, 11) are designed to hold the inside surface of the hub of the wheel away from the outside surface of the shaft over at least 50%, and preferably at least 75%, or indeed all of the support span (d 3 ) lying between said thrust members, preferably by providing substantially 25 radial clearance lying in the range 0.5% of the radius of the shaft (3) to 2% of said radius.

13. A device according to any preceding claim, characterized in that the first thrust member or the 30 second thrust member is axially backed up, against the wheel, by an elastically deformable compensation system (25) that is interposed between said thrust member (10, 11) and an abutment member (26) fastened to the shaft (3), such as a nut. 35

14. A device according to claim 13, characterized in that the compensation system (25) includes at least first and 4352309_1 (GHMatters) P93775.AU 43 second axially deformable members (27, 28), of the resilient washer type, that are stacked and compressed axially, the first deformable member (27) having stiffness less than the stiffness of the second 5 deformable member (28).

15. A device according to claim 13 or claim 14, characterized in that the abutment member (26) procures for the compensation system (25) a thrust that is 10 substantially conical, and that follows a third generator cone (C 26 ) having its vertex (F 26 ) situated substantially in register with the junction where said compensation system (25) meets the abutment member (10, 11) that it backs up. 15

16. A device according to any preceding claim, characterized in that it includes a third thrust member (50) situated on the same side of the wheel as the first thrust member (10), set back axially therefrom, and 20 having, against the wheel (2), a substantially conical third thrust surface (52), situated at a diameter greater than the diameter of the first thrust surface (12), and focused on the first focus (F 12 ). 25

17. A device according to any preceding claim, characterized in that it includes coupling means (40) having at least one transverse element ( 4 0'), of the key type, that connects the first thrust member (10) to the wheel (2) at the first conical thrust surface (12), or, 30 respectively, connects the second thrust member (11) to the wheel at the second conical thrust surface (13), so as to prevent any movement in rotation of the wheel relative to said thrust member. 35

18. A device according to claim 17, characterized in that the transverse coupling element ( 4 0') is formed by a key, a portion of which is designed to be received in a groove 4352309_1 (GHMatters) P93775.AU 44 (41) provided in the conical surface of the thrust member in question, and the other portion of which is designed to emerge from said groove (41) and to engage in a stop recess (42) that is substantially complementary, and that 5 is provided in the corresponding portion of the wheel, said key being secured to the thrust member, or to the wheel (5), e.g. by screw-fastening, in particular in order to avoid it tilting during removal of the wheel. 10

19. A device according to any preceding claim, characterized in that it is designed to be exposed to a fluid having a temperature greater than or equal to 1000C, 200 0 C, 500C, 700 0 C, or indeed 1000 0 C. 15

20. A method of assembling a wheel designed to co-operate with a fluid to drive said fluid or to be driven by it onto a shaft that is mounted to move in rotation about an axis of rotation (X-X'), said method being characterized in that it includes a clamping step during which the 20 wheel (2) is held stationary on the shaft (3) by clamping said wheel between first and second thrust members (10, 11) that are urged axially one against the other, the first thrust member having, against the wheel, a substantially conical first thrust surface (12) that is 25 substantially carried by a first generator cone (C 12 ) having its vertex (F 12 ) or "first focus" pointing towards the second thrust member, with the half-angle at its vertex (a12) being greater than or equal to the angle of adhesion (P12/2) corresponding to the coefficient of 30 friction between said first thrust surface and the wheel. 4352309_1 (GHMatters) P93775.AU