UNIVERSAL JOINT ASSEMBLIES

Abstract

A method of producing a universal joint assembly. The method comprises providing a joining member for forming a universal joint, said joining member comprising a first pivot and a second pivot; applying continuous fibre reinforcement and a polymer matrix to a form including said joining member to create a single fibre-reinforced polymer structure in which the joining member is embedded; and splitting said single fibre-reinforced structure into a first fibre-reinforced polymer shaft and a second fibre-reinforced polymer shaft that are coupled together by the joining member to form a universal joint.

Claims

1. A method of producing a universal joint assembly comprising: providing a joining member for forming a universal joint, said joining member comprising a first pivot and a second pivot; applying continuous fibre reinforcement and a polymer matrix to a form including said joining member to create a single fibre-reinforced polymer structure in which the joining member is embedded; and splitting said single fibre-reinforced structure into a first fibre-reinforced polymer shaft and a second fibre-reinforced polymer shaft that are coupled together by the joining member to form a universal joint.

2. The method of claim 1, wherein the first pivot of the joining member is embedded within continuous fibre reinforcement of the first fibre-reinforced polymer shaft and the second pivot of the joining member is embedded within continuous fibre reinforcement of the second fibre-reinforced polymer shaft.

3. The method of claim 1, wherein the form comprises a sacrificial core that at least partially surrounds the joining member and around which the continuous fibre reinforcement is applied, and the method comprises removing said sacrificial core after splitting the single fibre-reinforced structure.

4. The method of claim 1, wherein the form comprises a single mandrel around which the continuous fibre reinforcement is applied.

5. The method of claim 1, further comprising: braiding the continuous fibre reinforcement onto the form.

6. The method of claim 1, further comprising: guiding the continuous fibre reinforcement around conical fibre guiding extensions of the first and second pivots of the joining member, and subsequently removing said conical fibre guiding extensions.

7. The method of claim 1, further comprising: applying dry continuous fibre reinforcement to the form, placing the dry continuous fibre reinforcement and the form into a mould, and then introducing the polymer matrix to the mould.

8. A universal joint assembly comprising: a first fibre-reinforced polymer shaft; a second fibre-reinforced polymer shaft; and a joining member comprising a first pivot embedded within continuous fibre reinforcement of the first fibre-reinforced polymer shaft and a second pivot embedded within continuous fibre reinforcement of the second fibre-reinforced polymer shaft, said joining member coupling the first fibre-reinforced polymer shaft to the second fibre-reinforced polymer shaft to form a universal joint.

9. The universal joint assembly of claim 8, wherein the continuous fibre reinforcement of the first fibre-reinforced polymer shaft in which the first pivot is embedded is diverted around the first pivot.

10. The universal joint assembly of claim 8, wherein continuous fibre reinforcement of the first fibre-reinforced polymer shaft is aligned with continuous fibre reinforcement of the second fibre-reinforced polymer shaft when the first fibre-reinforced polymer shaft is aligned with the second fibre-reinforced polymer shaft.

11. The universal joint assembly of claim 8, wherein the first fibre-reinforced polymer shaft comprises continuous fibre reinforcement that extends parallel to an axis along which the first fibre-reinforced polymer shaft extends.

12. The universal joint assembly of claim 8, wherein the joining member comprises a hole with an inner diameter that is equal to or greater than an inner diameter of the first fibre-reinforced polymer shaft and/or the second fibre-reinforced polymer shaft.

13. The universal joint assembly of claim 8, wherein the joining member comprises two coaxial first pivots embedded within continuous fibre reinforcement of the first fibre-reinforced polymer shaft and two coaxial second pivots embedded within continuous fibre reinforcement of the second fibre-reinforced polymer shaft.

14. The universal joint assembly of claim 8, wherein the first fibre-reinforced polymer shaft comprises a coupling region in which the first pivot of the joining member is embedded, and a main region extending away from the coupling region, wherein the main region has a smaller diameter than the coupling region.

15. The universal joint assembly of claim 8, wherein the first fibre-reinforced polymer shaft comprises one or more regions with additional layers of fibre reinforcement.

Description

BRIEF DESCRIPTION OF FIGURES

[0043] One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures in which:

[0044] FIG. 1 is a schematic view of a universal joint assembly according to an example of the present disclosure;

[0045] FIG. 2 is a cross section of the universal joint assembly shown in FIG. 1;

[0046] FIG. 3 shows the joining member of the universal joint assembly in more detail;

[0047] FIGS. 4-10 illustrate various steps in a method of manufacturing the universal joint assembly shown in FIG. 1; and

[0048] FIG. 11 shows an aeroplane with an aeroplane wing actuator comprising the universal joint assembly shown in FIG. 1.

DETAILED DESCRIPTION

[0049] FIGS. 1 and 2 illustrate a universal joint assembly 100 comprising a first fibre-reinforced polymer (FRP) shaft 102, a second FRP shaft 104 and a joining member 106.

[0050] The first and second FRP shafts 102, 104 comprise continuous fibre reinforcement (e.g. continuous carbon fibre reinforcement) within a polymer matrix (e.g. epoxy).).

[0051] The continuous fibre reinforcement extends in several different directions and, in this example, includes zero degree fibre 105 that extends at 0° to the axes in which the shafts 102, 104 extend. The first and second FRP 102, 104 shafts also comprise several regions of additional fibre reinforcement 107, e.g. to provide additional stiffness and/or strength to the universal joint assembly 100.

[0052] The first and second FRP shafts 102, 104 are coupled together with the joining member 106.

[0053] The joining member 106 is shown in FIG. 3. The joining member 106 has a cruciform shape and comprises a central hub 108 from which two first pivots 110 and two second pivots 112 extend. The first pivots 110 are coaxial and extend along a first pivot axis. The second pivots 112 are coaxial and extend along a second pivot axis. The first pivot axis is perpendicular to the second pivot axis.

[0054] Each of the first and second pivots 110, 112 comprises a pivot lug that extends from the central hub 108 and a bearing that can rotate about the pivot lug, i.e. about the corresponding first or second pivot axis. The central hub 108 defines a hole 113 which extends perpendicular to the first and second pivot axes.

[0055] In the universal joint assembly 100, the bearings of the first pivots 110 are embedded within continuous fibre reinforcement of the first FRP shaft 102. The continuous fibre reinforcement of the first FRP shaft 102 is diverted, unbroken, around the bearings of the first pivots 110. The first FRP shaft 102 is thus firmly attached to the bearings of the first pivots 110. In this example no adhesive is needed to fix the first FRP shaft 102 to the bearings of the first pivots 110.

[0056] The first pivots 110 are attached to the first FRP shaft 102 such that the first pivot axis is perpendicular to the axis along which the first FRP shaft 102 extends. The first FRP shaft 102 is thus able to rotate relative to the central hub 108 of the joining member 106 about an axis perpendicular to the direction in which it extends.

[0057] Similarly, the bearings of the second pivots 112 are embedded within continuous fibre reinforcement of the second FRP shaft 104. The continuous fibre reinforcement of the second FRP shaft 104 is diverted, unbroken, around the bearings of the second pivots 112. The second FRP shaft 104 is thus firmly attached to the bearings of the second pivots 112. In this example no adhesive is needed to fix the second FRP shaft 104 to the bearings of the second pivots 112.

[0058] The second pivots 112 are attached to the second FRP shaft 104 such that the second pivot axis is perpendicular to the axis along which the second FRP shaft 104 extends. The second FRP shaft 104 is thus also able to rotate relative to the central hub 108 of the joining member 106 about an axis perpendicular to the direction in which it extends.

[0059] The first and second FRP shafts 102, 104 are thus coupled by the joining member 106 to form a universal joint. When the first FRP shaft 102 is rotated about the axis along which it extends, this rotational movement is transmitted through the joining member 106 to rotate the second FRP shaft 104 about the axis along which it extends, even when the first and second shafts 102, 104 are not aligned.

[0060] The universal joint assembly 100 thus features only three main parts: the FRP shafts 102 and the joining member 106. The shafts 102, 104 are coupled directly to the joining member 106 without the need for end connectors on each shaft. The joint assembly 100 thus has only a limited number of joins where misalignments or rotational backlash could be introduced. Furthermore, as explained below, the universal joint assembly 100 can be manufactured efficiently with only a small number of assembly steps.

[0061] FIGS. 4-9 illustrate a method for manufacturing the universal joint assembly 100.

[0062] In a first step shown in FIG. 4, a sacrificial core 200 is formed (e.g. by moulding, machining or 3D printing). The sacrificial core 200 comprises two symmetrical halves, with only one half shown in FIG. 4. The sacrificial core 200 is shaped to form a void within the final universal joint assembly 100 which reduces mass and allows the universal joint to function.

[0063] In the next step, shown in FIG. 5, the two halves of the sacrificial core 200 are fitted around the joining member 106. Again, for clarity, only one half of the sacrificial core 200 is shown in FIG. 5. The sacrificial core 200 ensures that the joining member 106 is held in exactly the right position and orientation throughout the manufacturing process.

[0064] FIG. 6 shows an optional step of fitting braiding spikes 202 (or, more generally, fibre-diverting spikes) to the bearings of the joining member 106. These spikes 202 may be used to guide reinforcing fibres around the bearings during the subsequent fibre braiding (or other fibre placement) step.

[0065] In the next step, illustrated in FIG. 7, the core 200 and the joining member 106 are mounted on to a cylindrical mandrel 204 to create a form 205. The mandrel 204 extends along a central axis C that is perpendicular to the first and second pivot axes of the joining member 106. The mandrel 204 passes through the hole 113 in the central hub 108 of the joining member 106. The mandrel 204 has a diameter which is approximately equal to the inner diameter of the hole 113.

[0066] In the next step, illustrated in FIG. 8, a braiding machine (not shown) is used to apply continuous dry fibre reinforcement 206 over the mandrel 204, the core 200 and the joining member 106. The use of braiding allows the continuous reinforcing fibre 206 to extend in many different directions, including at 0° to the central axis C. The braiding machine may pass over some parts of the mandrel 204 several times to form regions of additional fibre reinforcement.

[0067] As illustrated in FIG. 9, the entire assembly is then placed into a mould 208, and a polymer matrix 210 is introduced which impregnates the continuous fibre reinforcement 206. The polymer matrix 210is then cured to form a single fibre-reinforced polymer structure 212 in which the joining member is embedded. Because the inner diameter of the hole 113 in the central hub 108 is approximately equal to the diameter of the mandrel 204, the inner diameter of the hole 113 is also approximately equal to the inner diameter of the single fibre-reinforced polymer structure 212 (and thus approximately equal to the inner diameter of the resulting first and second FRP shafts 102, 104).

[0068] Then, as illustrated in FIG. 10, the single fibre-reinforced polymer structure 212 is split into a first FRP shaft 102 and a second FRP shaft 104 by machining a groove 214. The groove 214 is machined to leave the first pivots 110 embedded in continuous fibre reinforcement of the first FRP shaft 102 and the second pivots 112 embedded in continuous fibre reinforcement of the second FRP shaft 104. The sacrificial core 200 protects the joining member 106 during this machining process. The first and second FRP shafts 102, 104 are thus formed from continuous fibre reinforcement that was wound onto a single mandrel 204, which ensures that they are accurately aligned.

[0069] Finally, the mandrel 204 is removed, and the sacrificial core 200 is washed out or otherwise removed to leave behind the universal joint assembly 100 shown in FIG. 1.

[0070] As shown in FIG. 11, in this example the universal joint assembly 100 comprises part of an aeroplane wing actuator 302 of a aeroplane 300. The universal joint assembly 100 allows rotational motion to be transferred along the actuator as it flexes with the wing during flight.

[0071] While the disclosure has been described in detail in connection with only a limited number of examples, it should be readily understood that the disclosure is not limited to such disclosed examples. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of the disclosure. Additionally, while various examples of the disclosure have been described, it is to be understood that aspects of the disclosure may include only some of the described examples. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.