GB2571714A

GB2571714A - Drive shaft and method and apparatus suitable for use in the manufacture thereof

Info

Publication number: GB2571714A
Application number: GB1803486.8A
Authority: GB
Inventors: Dewhirst Michael; Lewis Paul
Original assignee: Lentus Composites Ltd
Current assignee: Lentus Composites Ltd
Priority date: 2018-03-05
Filing date: 2018-03-05
Publication date: 2019-09-11
Also published as: WO2019171043A2; WO2019171043A3; GB201803486D0

Abstract

A composite flexible drive shaft 12 comprises a cylindrical section 14, and a bellows-shaped section 16. The fibre winding angle of fibres in the cylindrical section 14 is different to the winding angle of fibres in at least part of the bellows section 16. The bellows section may comprise side walls 20 located to each side of a nose 18 and hinge portions 22 located between the nose 18 and the side walls 20 and between the side walls 20 and cylindrical section 14. The winding angle may be varied to provide the side walls 20 with substantially the same stiffness as the cylindrical section 14, and the hinge and nose portions with reduced stiffness to allow flexing in use. The drive shaft may be formed on a mandrel (30, Figure 3) comprising low melting temperature projecting components (32) and sheathed in a flexible sleeve prior to laying-up. A further flexible sleeve may sheath the layed-up shaft prior to curing. During curing the components (32) melt such that the drive-shaft can be removed from the flexible sheaths and mandrel after curing.

Description

(57) A composite flexible drive shaft 12 comprises a cylindrical section 14, and a bellows-shaped section 16. The fibre winding angle of fibres in the cylindrical section 14 is different to the winding angle of fibres in at least part of the bellows section 16. The bellows section may comprise side walls 20 located to each side of a nose 18 and hinge portions 22 located between the nose 18 and the side walls 20 and between the side walls 20 and cylindrical section 14. The winding angle may be varied to provide the side walls 20 with substantially the same stiffness as the cylindrical section 14, and the hinge and nose portions with reduced stiffness to allow flexing in use. The drive shaft may be formed on a mandrel (30, Figure 3) comprising low melting temperature projecting components (32) and sheathed in a flexible sleeve prior to laying-up. A further flexible sleeve may sheath the layed-up shaft prior to curing. During curing the components (32) melt such that the drive-shaft can be removed from the flexible sheaths and mandrel after curing.

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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Figure 1

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DRIVE SHAFT AND METHOD AND APPARATUS SUITABLE FOR USE IN THE MANUFACTURE THEREOF

This invention relates to a drive shaft, and in particular to a drive shaft fabricated from a composite material. It also relates to a method of manufacture or fabrication thereof, and to an apparatus suitable for use in the manufacture or fabrication thereof.

The use of composite materials has become increasingly widespread in a range of applications as the materials are of good strength and relatively low weight compared to traditional materials. By way of example, rotary drive shafts are often formed of metallic materials. Consequently, the drive shafts are of relatively high weight. In a number of applications, for example aerospace related applications and certain automotive related applications, there is a desire to reduce component weights in order to allow efficiency improvements to be made. Where the rotary speed of the drive shaft is to vary significantly in use, then the reduced weight may also be advantageous in that inertia may be reduced. The use of composite material instead of traditional materials allows such weight related benefits to be made whilst maintaining component strength at acceptable levels.

There is a desire for a drive shaft to be able to undergo limited flexing, in use, in order to accommodate slight axial misalignments between the components to which the drive shaft is connected.

Whilst using composite materials rather than traditional metallic materials can lead to weight savings whilst maintaining acceptable strength characteristics, the composite materials typically have to be of relatively stiff form in order to be able to transmit the required torque loadings, in use, and the level of stiffness may be such that the required level of flexing cannot be achieved, especially in drive shafts of relatively large diameters.

One technique that it known to improve the flexibility of a composite material shaft is to form it in such a manner as to include a region of bellows shaped form. Whilst such a technique allows the flexibility of the drive shaft to be enhanced, there are concerns that the presence of the bellows shaped region can result in the shaft being weakened and incapable of transmitting the required loads over the required lifetime of the drive shaft.

It is an object of the invention to provide a drive shaft of a composite material and an associated method of manufacture in which the flexibility of the shaft can be enhanced whilst allowing the required torque transmitting properties of the drive shaft to be maintained.

According to the present invention there is provided a drive shaft comprising a tubular component of wound fibre composite form, the component including a cylindrical section in which the wall of the component is of cylindrical form and extends in a direction parallel to the axis of the drive shaft, the component further including a bellows shaped section, wherein the fibre winding angle of the fibres in the cylindrical section is different to the winding angle of the fibres in at least part of the bellows shaped section.

Without varying the winding angle along the shaft in the manner of the invention, the bellows, whilst aiding in allowing flexing of the drive shaft, may be of reducing strength or torque transmitting capacity. Manufacturing the drive shaft in such a manner as to ensure that the bellows section is of sufficient torque transmitting capacity may result in the cylindrical section being unnecessarily large wall thickness, and in the shaft being excessively heavy, and may restrict the ability of the shaft to flex in the required manner.

By varying the winding angle in the manner of the invention, the stiffness and other characteristics of the cylindrical section and at least part of the bellows shaped section can be controlled independently of one another, at least to a degree, and need not be the same as one another.

The bellows shaped section conveniently comprises a central nose portion, side walls located to each side of the nose portion, and hinge portions connecting the side walls to the nose portion and to the cylindrical section of the component. The varying winding angle may be such as to result in the side walls being of substantially the same stiffness as the cylindrical section. By doing so, the drive shaft can be designed in such a manner that flexing thereof preferentially takes place within the hinge portions and the nose portion. The hinge portions and the nose portion may be designed in such a manner as to include additional material and/or such that the material is reinforced such that the hinge portions and the nose portion are able to flex to achieve the required level of flexing of the drive shaft whilst maintaining the ability of the drive shaft to transmit the required torque loading, in use.

It will be appreciated that by driving the flexing of the shaft to certain areas thereof, and designing those parts of the shaft in such a manner as to ensure that the shaft is capable of undergoing the required level of flexing whilst transmitting the required loadings, overengineering of other parts of the shaft can be avoided. The shaft can thus be manufactured in such a manner as to be of low weight, avoiding unnecessarily thickening parts of the shaft.

The varying winding angle can be used to vary the local stiffness of the shaft and thereby avoid the presence of parts of the shaft that will be overloaded in normal use, and to avoid the presence of weak spots therein.

The invention further relates to a method of manufacture of a drive shaft comprising winding a fibre material onto a mandrel, and curing a resin material carried by or impregnated into the fibre material to form a composite material component shaped to include a cylindrical section in which the wall of the component is of cylindrical form and extends in a direction parallel to the axis of the drive shaft, the component further including a bellows shaped section, wherein the method comprises a step of varying a fibre winding angle such that the winding angle of the fibres in the cylindrical section is different to the winding angle of the fibres in at least part of the bellows shaped section. The winding angle may be varied to achieve the effects described hereinbefore.

In order to form a wound fibre composite material component of the above described shape on a mandrel, and allow subsequent removal of the component from the mandrel, the mandrel would need to include collapsible features to define the bellows section, the collapsible features being collapsed after forming of the component to allow the removal of the component from the mandrel. This would require the mandrel to be of complex, and expensive, form. Another object of the invention is to provide a manufacturing technique whereby a drive shaft of the form described hereinbefore can be manufactured. The technique may be used to manufacture other components of complex form without departing from the scope of the invention.

According to another aspect of the invention, therefore, there is provided a manufacturing method comprising providing a cylindrical mandrel, locating upon the mandrel projecting components of a low melting temperature material, locating a flexible sleeve over the mandrel and projecting components, the flexible sleeve, once positioned over the mandrel and projecting components, having an outer profile substantially matching a desired internal profile of the component to be manufactured, winding over the sleeve a fibre material and curing a resin carried by or impregnated into the wound fibre to form a composite material component, the curing operation melting the projecting components, removing the composite material component and flexible sleeve from the mandrel, and removing the flexible sleeve from within the composite material component.

It will be appreciated that the invention allows a complex shaped composite material component to be formed without using a complex mandrel with collapsing features. The component may take the form of a drive shaft of the form described hereinbefore.

The flexible material sleeve is conveniently of a silicone material.

A second flexible material sleeve may be provided over the fibre material and resin prior to curing. This may aid in ensuring that the outer surface of the composite material component is of the desired shape. By way of example, if the shaft is desired to include overhanging or reentrant sections, the second sleeve may be shaped to push the fibre material and resin into recesses formed in the first mentioned flexible sleeve to form such formations. The assembly may be placed within a mould prior to curing, for example at an elevated temperature.

The invention also relates to an apparatus for use in the manufacture of a component comprising a cylindrical mandrel, projecting components of a low melting temperature material located upon the cylindrical mandrel, and a flexible sleeve located over the mandrel and projecting components, the flexible sleeve, once positioned over the mandrel and projecting components, having an outer profile substantially matching a desired internal profile of the component to be manufactured.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a view illustrating a drive shaft in accordance with an embodiment of the invention;

Figure 2 is a sectional view illustrating part of the drive shaft of Figure 1; and

Figures 3 to 5 illustrate apparatus for use in the manufacture of the drive shaft of Figure 1.

Referring firstly to Figures 1 and 2, a drive shaft 10 is illustrated. The drive shaft 10 is of wound fibre composite material form comprising reinforcing fibres of, for example glass or carbon form, wound onto a mandrel or former. The fibres may be coated or impregnated with a suitable resin prior to winding or, after winding, a suitable resin may be impregnated into the fibres. After completion of winding, the resin material is cured or allowed to cure. The curing operation is, to some extent, dependent upon the nature of the resin material used. Typically, resins are cured by heating and subsequently being allowed to cool to ambient temperatures. However, other resins may require other forms of treatment in order to cure.

The process for forming a drive shaft from a wound composite material is well known and will not be described herein in further detail save as required to understand the invention.

As shown in Figures 1 and 2, the drive shaft 10 is of generally cylindrical form, and comprises a wound fibre composite material component 12 including generally cylindrical sections 14 separated by bellows shaped sections 16. Each bellows shaped section 16 is shaped to define a nose 18, angled side walls 20 located to each side of the nose 18, and hinge portions 22 whereby the side walls 20 connect to the nose 18 and to the adjacent cylindrical sections 14.

The winding process by which the wound fibre material is wound onto the mandrel or former results in the fibres being wound with a varying winding angle. Specifically, the winding angle of the fibre material forming the cylindrical section 14 is different to the winding angle of the fibre material forming at least part of the bellows sections 16. By way of example, the winding angles may be selected so as to ensure that the cylindrical section 14 is of substantially the same stiffness as the side walls 20, the hinge portions 22 and nose 18 being of a reduced stiffness compared to the side walls 20 and the cylindrical section 14. Accordingly, the hinge portions 22 and nose 18 of each bellows section 16 may flex preferentially, substantially no flexing of the side walls 20 or cylindrical section 14 occurring in normal use, to achieve the desired level of flexing of the drive shaft 10.

Winding the fibre material with a varying winding angle requires, for example, the winding apparatus used to be capable of varying the speed with which a fibre guide moves in the axial direction of a mandrel as the mandrel is rotated at a constant speed. By appropriate control over the operation of the winding apparatus, the winding angle can be changed as the fibre guide passes along the length of the mandrel so as to form at least parts of the bellows sections with a different winding angle to that used when winding the cylindrical sections.

By way of example, the winding angle used on the cylindrical section 14 may be in the region of +40-50°, say ±45° or ±50°, relative to the axis of the cylindrical section 14. It is anticipated that the section 14 will have a thickness in the region of 3-10mm. In the side walls 20, the winding angle may be increased to, say, ±55-70°. Doing so decreases the bending stiffness and torque strength. However, the increased diameter serves to increase the strength. Accordingly, the net result may be that the increased winding angle maintains the overall strength of the shaft, the reduction in strength arising from the increased winding angle being balanced by the change in shaft geometry. The winding angles of the hinge portions 22 between the section 14 and the side walls 20 may gradually change between these angles. At the nose 18 and hinge portions 22 associated therewith, a winding angle chosen to achieve a reduced stiffness may be used. In such an arrangement, flexing of the drive shaft 10 preferentially takes place in the nose 18 and the associated hinge portions 22.

Alternatively, rather than increase the winding angle of the side walls 20, a reduced winding angle of, say, ±25-35° may be used to result in the side walls 20 being of greater stiffness than the cylindrical section 14 to drive flexing or bending into the nose 18 and associated hinge portions 22.

In order to ensure that the hinge sections 22 and nose section 18 are capable of transmitting the required torque loadings, in use, additional material or reinforcement may be applied thereto, during manufacture. The flexibility of these parts of the component 12 may be enhanced by incorporating interlayers between certain of the fibre winding layers, if desired, to prevent bonding between adjacent fibre layers and so reduce the resistance to shearing movement therebetween, in use.

The drive shaft 10 is finished by having end fittings 24, 26 secured to the ends thereof whereby the drive shaft 10 can be secured to other components of the device with which the drive shaft 10 is to be used. Any suitable technique may be used to secure the end fittings 24, 26 in position in such a manner as to be able to withstand and transmit the required torque loadings, in use.

As shown in Figures 3 to 5, the component 12 is conveniently manufactured by providing a cylindrical mandrel 30 upon which are mounted moulded arcuate components 32 of a relatively low melting point material, for example of a suitably low melting point alloy material. A flexible material sleeve 34 of a silicone material is positioned over the material 30 and components 32. The outer profile of the sleeve 34 is shaped to match the desired internal profile of the component 12. Accordingly, the sleeve 34 may define smoothly radiused curves at the edges of the components 32, resulting in the component 12 having smoothly radiused hinge portions 22 rather than having sharp intersections at these points.

The fibre of the composite material component 12 is wound over the sleeve 34. Before curing of the resin material of the composite material component 12 a second sleeve 36 is applied to the exterior of the fibre material and resin. The internal profile of the second sleeve 36 is shaped to match the desired outer profile of the component 12. If desired, the entire assembly may then be located within a suitably shaped mould to support the second sleeve 36 in its required shape.

The resin curing operation conveniently involves heating the assembly, and the heating operation results in melting of the components 32.

After curing, as the components 32 will have melted, the component 12 can be removed from the sleeves 34, 36, the sleeves 34, 36 flexing to allow the removal thereof from the component 12.

Any required finishing operations, for example machining of the ends of the component 12 and attachment of end fittings 24, 26 thereto can then be undertaken to form the finished drive shaft 10.

The use of the outer sleeve 36 is advantageous in that it can aid in ensuring that the outer profile of the component 12 is of the desired shape. If the component 12 is to include overhanging or re-entrant sections, the outer sleeve 36 can force the material of the component 12 into recesses within the inner sleeve 34 prior to curing to result in the formation of such sections.

The outer sleeve 36, in combination with the inner sleeve 24, serves to ensure that the component 12 has the required shape and wall thickness.

Whilst the method described hereinbefore represents one technique by which the drive shaft may be manufactured, it will be appreciated that the drive shaft may be manufactured using other techniques. Furthermore, the above described manufacturing method may be used in the manufacture of other components without departing from the scope of the invention. It is not restricted to use in the manufacture of drive shafts with bellows regions of varying winding angle as described hereinbefore.

Whilst specific embodiments of the invention are described hereinbefore, a number of modifications and alterations may be made to the described embodiment without departing from the scope of the invention as defined by the appended claims. By way of example, although in the described arrangement the bellows sections 16 project radially outwardly from the cylindrical sections 14, arrangement are also possible in which the bellows sections 16 project radially inwardly. A range of other modifications and alterations are also possible.

Claims

1. A drive shaft comprising a tubular component of wound fibre composite form, the component including a cylindrical section in which the wall of the component is of cylindrical form and extends in a direction parallel to the axis of the drive shaft, the component further including a bellows shaped section, wherein the fibre winding angle of the fibres in the cylindrical section is different to the winding angle of the fibres in at least part of the bellows shaped section.

2. A shaft according to Claim 1, wherein the bellows shaped section comprises a central nose portion, side walls located to each side of the nose portion, and hinge portions connecting the side walls to the nose portion and to the cylindrical section of the component, the varying winding angle being such as to result in the side walls being of substantially the same stiffness as the cylindrical section.

3. A shaft according to Claim 2, wherein the hinge portions are designed in such a manner as to include additional material and/or such that the material thereof is reinforced such that the hinge portions are able to flex to achieve the required level of flexing of the drive shaft whilst maintaining the ability of the drive shaft to transmit the required torque loading, in use.

4. A shaft according to Claim 2 or Claim 3, wherein the winding angle used in the side walls is chosen to achieve substantially the same stiffness as that of the cylindrical section taking into account the difference in diameter thereof.

5. A shaft according to Claim 4, wherein the winding angle in the side walls is greater than that of the cylindrical section.

6. A shaft according to Claim 2 or Claim 3, wherein the winding angle used in the side walls is chosen to result in the side walls being of greater stiffness than the cylindrical section.

7. A shaft according to Claim 6, wherein the winding angle in the side walls is lower than that of the cylindrical section.

8. A method of manufacture of a drive shaft comprising winding a fibre material onto a mandrel, and curing a resin material carried by or impregnated into the fibre material to form a composite material component shaped to include a cylindrical section in which the wall of the component is of cylindrical form and extends in a direction parallel to the axis of the drive shaft, the component further including a bellows shaped section, wherein the method comprises a step of varying a fibre winding angle such that the winding angle of the fibres in the cylindrical section is different to the winding angle of the fibres in at least part of the bellows shaped section.

9. A manufacturing method comprising providing a cylindrical mandrel, locating upon the mandrel projecting components of a low melting temperature material, locating a flexible sleeve over the mandrel and projecting components, the flexible sleeve, once positioned over the mandrel and projecting components, having an outer profile substantially matching a desired internal profile of the component to be manufactured, winding over the sleeve a fibre material and curing a resin carried by or impregnated into the wound fibre to form a composite material component, the curing operation melting the projecting components, removing the composite material component and flexible sleeve from the mandrel, and removing the flexible sleeve from within the composite material component.

10. A method according to Claim 9, wherein the flexible material sleeve is of a silicone material.

11. A method according to Claim 9 or Claim 10, wherein a second flexible material sleeve is provided over the fibre material and resin prior to curing.

12. An apparatus for use in the manufacture of a component comprising a cylindrical mandrel, projecting components of a low melting temperature material located upon the cylindrical mandrel, and a flexible sleeve located over the mandrel and projecting components, the flexible sleeve, once positioned over the mandrel and projecting components, having an 5 outer profile substantially matching a desired internal profile of the component to be manufactured.

Intellectual Property Office

Application No: GB1803486.8 Examiner: Tim James

Claims searched: 1-8 Date of search: 28 August 2018

Patents Act 1977: Search Report under Section 17

Documents considered to be relevant:

Category Relevant to claims Identity of document and passage or figure of particular relevance X 1 and 8 US2002/198057 Al (VOLVO) see the figures and paragraph 0026 X 1 and 8 US4540385 A (UNI CARDAN AG) see fold 3b in the figures and column 3 lines 3840 X 1 and 8 FR2637661 Al (AEROSPATIALE) see the figures and the paragraph bridging pages 5 and 6

Categories:

X Document indicating lack of novelty or inventive step A Document indicating technological background and/or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of before the filing date of this invention. same category. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.

Field of Search:

Search of GB, EP, WO & US patent documents classified in the following areas of the UKCX :

Worldwide search of patent documents classified in the following areas of the IPC____________

B29C; B29D; B29L; F16C; F16D_____________________________________