A method of manufacturing, a rim assembly, a rim-driven-fan, and a mandrel

Abstract

A method of manufacturing a rim assembly for either a rim-driven-fan for an electrically powered fan engine or a rim-driven wheel device powered by means of electromagnetic motors. The method comprise

Description

[02] Electrically powered fan engines may include rim-driven-fans having a rim and one or more blades mounted within the rim. A plurality of magnets may be mounted around the rim to drive the rim electromagnetically using windings within the engine. To prevent radial movement of the magnets due to centrifugal force during operation, it is possible to fit a retaining band around the magnets. Such retaining bands are often fitted while the retaining band is held in tension. Whilst this applies adequate forces to combat the centrifugal forces imparted on the magnets, residual forces are often imparted to the one or more blades when the fan engine is not running. The blades may need to be made from an increased amount of material, and even heavy materials and even special high-strength materials, to accommodate such residual forces.

[03] It is an aim of the subject-matter of the present disclosure to improve on the prior art. SUMMARY

[04] According to a first aspect of the present invention, there is provided a method of manufacturing a rim assembly for either a rim-driven-fan for an electrically powered fan engine or a rim-driven wheel device powered by means of electromagnetic motors. The method comprises: providing a rim, wherein the rim is a bladeless rim; mounting a plurality of magnets around the rim; and attaching a non-magnetic retaining band in tension around the plurality of magnets. Attaching the retaining band in this way may pre-stress, or pre-load the rim.

[05] The term “bladeless” is used herein to mean a rim without blades or spokes attached to it. The retaining band constraints movement of the magnets during operation, which are biased radially outwards due to centrifugal forces imparted on the magnets. During rest, the retaining band imparts stress to blades provided within the rim if the blades were included during application of the retaining band during manufacture. By attaching the non-magnetic retaining band to the magnets mounted around the bladeless rim, the residual stresses at rest are reduced. Therefore, the blades can be designed differently and their weight can be reduced by using a reduction in material and even different materials, e.g. plastics materials like nylon.

[06] In an embodiment, the rim assembly may be cured after attaching the retaining band to fix a position of the retaining band in a pre-stressed state around the plurality of magnets.

[07] In an embodiment, the retaining band may be a filament. A filament is easier to wind around the magnets in tension than other forms of retaining band. The retaining band may alternatively be a pre-impregnated tape.

[08] In an embodiment, the attaching the non-magnetic retaining band may comprise: winding a filament or pre-impregnated tape around the magnets.

[09] In an embodiment, the retaining band may have a thickness of between 0.5 and 1,5mm.

[10] In an embodiment, the retaining band may be made from a composite material. In this way, weight may be reduced.

[11] In an embodiment, the mounting the plurality of magnets around the rim may comprise mounting the plurality of magnets in a Halbach array.

[12] In an embodiment, the method may further comprise cutting the plurality of magnets mounted around the rim to have a substantially smooth circular exterior surface in crosssection prior to attaching the non-magnetic retaining band. In this way, the substantially smooth circular exterior surface helps to balance the rim for high-speed rotation.

[13] In an embodiment, the method may further comprise: mounting the rim to a mandrel; and increasing a diameter of the mandrel to apply an outward radial force to an interior surface of the rim, prior to attaching the retaining band. In this way, the rim is supported when attaching the retaining band and the mandrel can be released from the rim assembly after the rim has been compressively stressed by the retaining band. Therefore, residual stress on the rim, and also the blades once they are attached to the rim, will be reduced.

[14] In an embodiment, providing the rim may comprise manufacturing the rim to have one or more attachment formations on an interior surface of the rim for engaging one or more complimentary attachment formations on an exterior surface of a mandrel. The mounting formations may reducing slipping of the rim as it rotates when attaching the retaining band.

[15] In an embodiment, the providing the rim may comprise manufacturing the rim to have a radially extending flange on each side of the rim to retain the plurality of magnets and the retaining band axially. In this way, mounting the magnets and retaining band can be made quicker and there will be less need for quality checks of the rim assembly.

[16] In an embodiment, the rim may be made from a metallic material, wherein the metallic material is preferably an aluminium alloy or a titanium alloy. In other embodiments, the rim may be made from a non-metallic material, the non-metallic material may be a plastics material, and may optionally be made from a composite material, e.g. carbon fibre reinforced plastic.

[17] According to another aspect, there is provided a method of manufacturing a rim-driven-fan or a rim-driven wheel device. The method comprises: providing the rim assembly of any preceding aspect or embodiment; providing a plurality of fan blades or spokes; and mounting the plurality of fan blades or spokes to the rim after attaching the retaining band. Mounting the blades after manufacturing the rim assembly means that residual loads resulting from the pre-stress from the retaining band will be accommodated by the rim assembly and residual loads transferred to the blades will be reduced. In this way, design flexibility for the blades can be improved and the blades can be made thinner for example, and from a lighter material.

[18] In an embodiment, the providing the plurality of fan blades may comprise providing a blisk comprising the plurality of fan blades, and wherein the mounting the plurality of fan blades to the rim may comprise attaching the blisk to an interior surface of the rim.

[19] In an embodiment, the providing the plurality of fan blades or spokes may comprise manufacturing the plurality of fan blades or spokes from a plastics material, wherein the plastics material is preferably nylon.

[20] In an embodiment, the providing the plurality of fan blades may comprise providing a blisk comprising the plurality of fan blades, and wherein the mounting the plurality of fan blades to the rim may comprise attaching the blisk to an interior surface of the rim.

[21] In an embodiment, the providing the plurality of fan blades may comprise manufacturing the plurality of fan blades from a plastics material, wherein the plastics material is preferably nylon. In this way, the weight of the assembly is reduced compared to using metal, for example.

[22] The plastics materials may be a composite material, at least some of the constituents of which are made from plastic. For example, the composite material may be carbon fibre reinforced plastic.

[23] According to another aspect, there is provided a rim assembly manufactured using the method of any preceding aspect or embodiment.

[24] According to another aspect, there is provided a rim-driven-fan manufactured using the method of any preceding aspect or embodiment.

[25] According to another aspect, there is provided a rim-driven-wheel device manufactured using the method of any preceding aspect or embodiment.

[26] According to another aspect, there is provided a rim assembly for either a rim-driven-fan for an electrically powered fan engine or a rim-driven wheel device powered by means of electromagnetic motors. The rim assembly comprises: a rim, wherein the rim is a bladeless rim; a plurality of magnets mounted around the rim; and a non-magnetic retaining band attached in tension around the plurality of magnets to pre-stress the rim.

[27] In an embodiment, the retaining band may comprise a filament wound around the plurality of magnets. Alternatively, the retaining band may comprise a pre-impregnated tape.

[28] In an embodiment, the retaining band may have a thickness between 0.5 and 1.5 mm.

[29] In an embodiment, the retaining band may be made from a composite material.

[30] In an embodiment, the plurality of magnets may be mounted in a Halbach array.

[31] In an embodiment, the plurality of magnets may provide a substantially smooth circular exterior surface.

[32] In an embodiment, the rim may be made from a metallic material, wherein the metallic material is preferably an aluminium alloy or a titanium alloy.

[33] In an embodiment, the rim may comprise a radially extending flange at each side to retain the retaining band and the plurality of magnets axially.

[34] In an embodiment, the rim may comprise one or more attachment formations on an interior surface thereof for engaging one or more complimentary attachment formations on an exterior surface of a mandrel.

[35] According to another aspect, there is provided a rim-driven-fan for an electrically powered fan engine. The rim-driven-fan may comprise: the rim assembly any preceding aspect or embodiment; and a plurality of blades mounted to the rim after attaching the retaining band.

[36] In an embodiment, the rim-driven-fan may comprise a blisk comprising the plurality of blades, wherein the blisk may be mounted to an interior surface of the rim.

[37] In an embodiment, the plurality of blades may be made from a plastics material, wherein the plastics material is preferably nylon.

[38] The plastics materials may be a composite material, at least some of the constituents of which are made from plastic. For example, the composite material may be carbon fibre reinforced plastic.

[39] According to another aspect, there is provided a rim-driven wheel device configured to be powered by means of electromagnetic motors. The rim-driven wheel device comprises: the rim assembly of any preceding aspect or embodiment; and a plurality of blades mounted to the rim after the retaining band.

[40] According to another aspect, there is provided a mandrel for supporting a rim assembly during attachment of a retaining band. The mandrel comprises: a plurality of segments, each segment having an exterior surface for engaging an interior surface of a rim of the rim assembly; one or more attaching formations for engaging one or more respective attachment formations on the interior surface of the rim to prevent the rim assembling slipping when rotating the mandrel; and a bung dimensioned to move apart radially the plurality of segments in response moving the bung axially into the mandrel. [41 ] In this way, a diameter reduction of the rim during attachment of the retaining band can be accommodated. Therefore, it will be possible to remove the mandrel after the band has been installed and there will be a reduction of residual stress on one or more blades attached within the rim subsequently.

[42] In an embodiment, the bung may be tapered.

[43] In an embodiment, the bung may have a substantially frusto-conical exterior crosssection.

[44] These and other aspects of the present invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[45] The embodiments of the present inventions may be best understood with reference to the accompanying figures, in which:

[46] Figure 1 shows a cutaway perspective view of an electric fan engine having rim-driven-fans, according to one or more embodiments;

[47] Figure 2 shows a perspective view of a rim-driven-fan from Figure 1;

[48] Figure 3 shows an aft view of the rim-driven-fan from Figure 2;

[49] Figure 4 shows a cross-sectional view of the rim-driven-fan from Figure 3 taken along line A-A of Figure 3;

[50] Figure 5 shows a perspective view of a rim of the rim-driven-fan from Figure 2 mounted to a mandrel; [51 ] Figure 6 shows an exploded perspective view of the rim and the mandrel from Figure 5;

[52] Figure 7 shows an exploded section view of the rim and the mandrel from Figure 5;

[53] Figure 8 shows a front view of the mandrel from Figure 5;

[54] Figure 9 shows a cross-section view of the mandrel from Figure 5 taken along line A-A from Figure 8;

[55] Figure 10 shows an exploded perspective view of the rim-driven-fan from Figure 2;

[56] Figure 11 shows a flow chart summarising a method of manufacturing a rim assembly for either a rim-driven-fan for an electrically powered fan engine or a rim-driven wheel device powered by means of electromagnetic motors, according to one or more embodiments; and

[57] Figure 12 shows a flow chart summarising a method of manufacturing a rim-driven fan or a rim-driven wheel device, according to one or more embodiments. DESCRIPTION OF EMBODIMENTS

[58] Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of others.

[59] With reference to Figure 1, an aero engine may be provided in the form of an electric fan engine 10. The electric fan engine 10 has an inlet 12 and an outlet 14 or exhaust. The electric fan engine 10 (or engine) includes cowling 16 and a pylon 18 for attaching the engine 10 to an airplane structure, for example. The engine 10 includes one or more fans. In this embodiment, there are two fans. However, in other embodiments there may a single fan or three or more fans. The engine 10 includes motor windings 22 which may be electrically energised by a remote power source. The motor windings 22 cooperate with a plurality of magnets 24 mounted around a rim of the fans to drive the rim of the fans in a manner that is well understood in the field. In this way, the fans may be rim-driven-fans 20.

[60] Whilst Figure 1 has been provided to illustrate the embodiment as a rim-driven-fan for an electrically powered fan engine, the present disclosure is equally applicable to a rim-driven wheel device powered by means of electromagnetic motors.

[61] With reference to Figure 2, the rim-driven-fan 20 includes a rim assembly 26 and a plurality of blades 28 mounted to the rim assembly. In other embodiments the plurality of blades may be one or more blades.

[62] With reference to Figure 3, an aft view of the rim-drive-fan 20 includes a hub 30 for mounting to an axle of the engine. The blades 28 extend radially around the hub 30.

[63] Figure 4 shows a cross-section view of the rim-driven-fan 20 taken from the line A-A in Figure 3.

[64] With reference to Figure 3, the rim assembly 26 includes a rim 32 and a plurality of magnets 24 mounted around the rim, and a non-magnet retaining band 34 attached in tension around the plurality of magnets to pre-stress, or pre-load, the rim 32.

[65] With reference to Figure 5, to manufacture the rim assembly, a rim 32 is provided, which is a bladeless rim. In other words, it is a rim where the blades, e.g. a blisk, has not yet been attached to its interior surface. The rim 32 is mounted to a mandrel 36. The mandrel includes an axially extending spigot 38 having a non-circular mounting portion 40. The non-circular mounting portion 40 may be substantially square in cross-section. The mounting portion 40 is mounted to a complimentary mounting structure of a rotary drive to induce rotation to the mandrel 36.

[66] The rim 32 includes a radially extending flange 42 on each side of the time to retain the plurality of magnets and the retaining band axially. The rim may be made from a metallic material. The metallic material may be an aluminium alloy or a titanium alloy. In other embodiments, the rim may be made from a plastics material. The rim may be may from a composite material, e.g. carbon fibre reinforced plastic.

[67] With reference to Figures 6 to 9, the mandrel 36 includes a plurality of segments 44, a retaining ring 46, a plurality of attaching members 48, the spigot 38, and a bung 50.

[68] In this embodiment, there are three segments 44. In other embodiments there may be two of four or more segments. The segments combine to form a substantially cylindrical, or disc, shaped object having a substantially circular cross-section. Each segment 44 has an exterior surface for engaging an interior surface of the rim 32. Each segment includes one or more attaching formations 52 for engaging one or more respective attachment formations 54 on an interior surface of the rim 32 (see Figure 10) to prevent the rim assembly slipping when rotating the mandrel 36. There may be one attaching formation 52 on each segment included as a groove with screw holes on each exterior surface. The attaching formation 52 may include one or more screws 56 to be mounted within the screw holes to form a protrusion for engaging the attachment formations 54 (see Figure 10) on the interior surface of the rim 32.

[69] Each segment 44 may have a bolt hole on its side face 58 to receive one of the attaching members 48 in the form of a bolt. The retaining ring 46 may also include bolt holes for receiving the bolts. In this way, the retaining ring 46 may be attached to the segments to secure the segments 44 such that they form the substantially disc shaped object.

[70] During manufacture of the rim assembly, the disc shaped mandrel is inserted within the rim 32. The bolts and retaining ring remain in place during manufacture. There are elongated holes (not shown) in the ring 46 to accommodate the radial movement of the bolts and the mandrel segments. The bolts are then tightened up once the mandrel has engaged with the rim to fix the segments in place.

[71]

[72] The spigot 38 includes a threaded end 60 opposite to an end having the mounting portion 40. The bung 50 has a substantially frustoconical exterior cross-section. The bung 50 has an interior hole passing through it. The interior hole may have a clearance fit with the threaded end. A nut 62 may be provided to screw onto the threaded end 60 to capture the bung 50. The segments 44 may each have a chamfered corner. The chamfered corners may combine to form a substantially frustoconical shaped opening for receiving the bung 50.

[73] During manufacture of the rim assembly, the nut 62 is tightened to cause the bung 50 to move axially towards the mandrel 36. The bung 50 causes the segments to radially separate to increase a diameter of the mandrel to apply an outward radial force to an interior surface of the rim 32. In this way, the bung 50 may be dimensioned to move apart radially the plurality of segments in response to moving the bung axially into the mandrel. This occurs prior to attaching the retaining band.

[74] The plurality of magnets 24 are then mounted around the rim (see Figure 4). The magnets 24 may be mounted around the rim in an Halbach array. Next, the plurality of magnets is cut so as to ensure a smooth circular exterior surface in cross-section prior to attaching the retaining band. This cutting may be achieved by rotating the mandrel and using a grinding machine, for example. Next, the method includes attaching the nonmagnetic retaining band in tension around the plurality of magnets to pre-stress, or preload, the rim 32. This is achieved by rotating the mandrel and attaching the retaining band using the rotation. The retaining band 34 may be a filament. The retaining band may have a thickness of between 0.5 and 1.5 mm. In some embodiments, the thicknes may be 1 mm or around 1mm. The band is made by winding either the filament of pre-impregnated individual fibres, pre-impregnated tows (say 0.1-0.3mm thick) or pre-impregnated tape on to the magnets. The filament diameter is around 0.008mm. The retaining band may be made from carbon fibre, or aramid fibre. Once the retaining band has been attached, the rim assembly is cured in an oven to fix in place the retaining band whilst in tension.

[75] With reference to Figure 10, to manufacture the rim-driven-fan 20, the rim assembly 26 is provided together with a plurality of fan blades 28. The plurality of fan blades 28 may be provided in the form of a blisk comprising the plurality of fan blades 28. The fan blades 28 are mounted to the rim assembly by attaching the blisk to the interior surface of the rim. It will be appreciated that the fan blades 28 are attached to the rim 32 after attaching the retaining band 34. In this way, residual forces while the engine is not operating are not transferred to the blades 28. The blades thus may be made from a lighter material. In some embodiments, the fan blades 28 may be made from a plastics material. The plastics material may be nylon. In other embodiments, the blades 28 may be made from a metallic material, but with thinner blades.

[76] It will be noted that the attachment formations (also known as keyways) 54 are provided as axially extending grooves for engaging the attaching formations 52 (also known as keys). The screws 56 are used as stops to axially locate the rim on the mandrel. The grooves may be circumferentially spaces around the rim 32. The blisk may also include attachment formations 70 around its rim 72. The attachment formations 70 of the blisk may be complimentary to those of the rim 32 and may be protrusions to fit within the grooves. In this way, circumferential slippage of the blisk relative to the rim assembly 32 during operation of the engine may be reduced.

[77] In summary, the various embodiments may be summarised with reference to Figures 11 and 12 as follows.

[78] With reference to Figure 11, the methods may be summarised as a method of manufacturing a rim assembly for either a rim-driven-fan for an electrically powered fan engine or a rim-driven wheel device powered by means of electromagnetic motors, the method comprising: providing S100 a rim, wherein the rim is a bladeless rim; mounting S102 a plurality of magnets around the rim; and attaching S104 a non-magnetic retaining band in tension around the plurality of magnets to pre-stress the rim.

[79] With reference to Figure 12, the methods may be summarised as a method of manufacturing a rim-driven-fan or a rim-driven wheel device powered by means of electromagnetic motors, the method comprising: providing S200 the rim assembly as described above; providing S202 a plurality of fan blades or spokes; and mounting S204 the plurality of fan blades or spokes to the rim after attaching the retaining band.

[80] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

[81] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different 11 dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A method of manufacturing a rim-driven-fan or a rim-driven wheel device, the method comprising:providing a rim assembly wherein the method of providing the rim assembly comprises:providing a rim, wherein the rim is a bladeless rim;mounting a plurality of magnets around the rim;attaching a non-magnetic retaining band in tension around the plurality of magnets;mounting the rim to a mandrel;increasing a diameter of the mandrel to apply an outward radial force to an interior surface of the rim, prior to attaching the retaining band; andreleasing the mandrel from the rim assembly after the rim has been compressively stressed by the retaining band;the method of manufacturing a rim-driven-fan or a rim-driven wheel device further comprising:providing a plurality of fan blades or spokes; andmounting the plurality of fan blades or spokes to the rim after attaching the retaining band;wherein the providing the plurality of fan blades comprises providing a blisk comprising the plurality of fan blades, and wherein the mounting the plurality of fan blades to the rim comprises attaching the blisk to an interior surface of the rim.

2. The method of Claim 1, wherein the attaching the non-magnetic retaining band comprises:winding a filament around the magnets.

3. The method of Claim 1 or Claim 2, wherein the retaining band has a thickness of between 0.5 and 1,5mm.

4. The method of any preceding claim, wherein the retaining band is made from a composite material.

5. The method of any preceding claim, wherein the mounting the plurality of magnets around the rim comprises mounting the plurality of magnets in a Halbach array.

6. The method of any preceding claim, further comprising cutting the plurality of magnets mounted around the rim to have a substantially smooth circular exterior surface in cross-section prior to attaching the non-magnetic retaining band.

7. The method of Claim 1, wherein providing the rim comprises manufacturing the rim to have one or more attachment formations on an interior surface of the rim for engaging one or more complimentary attachment formations on an exterior surface of a mandrel.

8. The method of any preceding claim, wherein the providing the rim comprises manufacturing the rim to have a radially extending flange on each side of the time to retain the plurality of magnets and the retaining band axially.

9. The method of any preceding claim, wherein the rim is made from a metallic material, wherein the metallic material is preferably an aluminium alloy or a titanium alloy.

10. The method of Claim 1, wherein the providing the plurality of fan blades or spokes comprises manufacturing the plurality of fan blades or spokes from a plastics material, wherein the plastics material is preferably nylon.

Images