Composite flexible coupling

Abstract

A flexible coupling for transmitting torque between parts of a transmission shaft system comprises a tubular section of continuous-fibre-reinforced composite material which has been modified to form a living hinge section with reduced bending stiffness to allow flexion of the tubular section. The tubular section may be modified through the provision of a pattern of formations within the living hinge section. The formations may be in the form of apertures and/or recesses in the continuous-fibre-reinforced composite material to create a plurality of living hinges in the material between, in particular slots and/or grooves.

1 . A method of forming a flexible coupling suitable for transmitting torque between parts of a transmission shaft system, the flexible coupling having a tubular section comprising continuous-fibre-reinforced composite material, the method comprising:
 modifying the tubular section to provide a living hinge section of reduced bending stiffness which allows flexion of the tubular section.   
     
     
         2 . A method according to  claim 1 , wherein the modifying comprises forming a pattern of formations within the living hinge section by removing continuous-fibre-reinforced composite material or by deflecting fibre of the continuous-fibre-reinforced composite material during fabrication. 
     
     
         3 . The method of  claim 2 , wherein removing or deflection creates formations which are in the form of apertures and/or recesses in the continuous-fibre-reinforced composite material, to thereby create a plurality of living hinges in the material between. 
     
     
         4 . The method of  claim 3 , wherein the formations are formed as slots and/or grooves in the continuous-fibre-reinforced composite material of the living hinge section. 
     
     
         5 . The method according to  claim 2 , wherein the tubular section is formed by a winding, braiding or lay-up process. 
     
     
         6 . The method of  claim 5 , wherein:
 (i) the winding process comprises winding a first layer of continuous fibres around a core having an axis, the fibres being wound with a first winding angle with respect to the axis and winding a second layer of continuous fibres around the core and the first layer, the second layer of continuous fibres being wound with a second winding angle with respect to the axis, wherein the first winding angle is different from the second winding angle;   (ii) the braiding process comprises braiding a plurality of continuous fibres around a core such that continuous fibres of different winding directions are laid over a region in an alternating manner; or   (iii) the lay-up process comprises depositing woven sheets of continuous fibres around a core,
 and wherein the tubular section is subsequently cured; and 
 preferably wherein a liner present in the tubular section during the winding/braiding/lay-up process is removed. 
   
     
     
         7 . The method according to  claim 5 , wherein the step of modifying the tubular section comprises:
 providing one or more pegs extending from the core; and wherein the winding/braiding/lay-up process includes passing the fibres around the peg(s) such that, when the peg(s) is/are removed, there is a peg-shaped gap in the respective layer of fibres.   
     
     
         8 . The method of  claim 5 , wherein the step of modifying the tubular section comprises:
 cutting a plurality of formations in the tubular section, preferably as sets of slots or grooves, to provide the pattern of formations that allows flexion of the tubular section.   
     
     
         9 . The method of  claim 8 , wherein the step of modifying the tubular section comprises keeping some continuous-fibre-reinforced composite material extending over the formations. 
     
     
         10 . A method of flexibly coupling parts of a transmission shaft system to accommodate axial misalignment between the parts, the method comprising:
 connecting the flexible coupling of  claim 1  between the parts.