The present invention relates to the manufacture and joining of articles such as ligneous, wooden or wood like articles and to the articles once manufactured. In a particular arrangement of the present invention it relates to the production of articles of natura lly occurring fibrous materials such as woods, including bamboo, and relates particularly to the joining of pieces of such materials in the production of an article comprising such materials.

There are a number of ways to join articles and the optimum joining technique depends on the materials in question and the performance requirements for the subsequently formed joint. Metal articles, for example, may be welded, riveted or bonded whilst ligneous or wooden articles may be jointed and bonded but may not be welded and are not often riveted. The dynamic performance of the joint once formed can have a significant effect on the performance of the finished article and much work is undertaken to ensure the optimum joint is obtained. Ligneous articles are articles made of wood or have the appearance or texture of wood.

Some materials are more difficult to join than others and factors such as external surface properties and the physical structure of some materials means that they are extremely difficult to join successfully and this has prevented them being used in many applications. This difficulty is often experienced in association with naturally grown fi brous materials, such as bam boo, and other materials having a generally wooden structure. The relatively smooth and naturally lubricated external surface of bamboo does not lend itself to bonding techniques that can be readily employed on other materials. In addition, the hollow nature of bamboo and the relatively soft nature of the inner surface of bamboo canes makes it difficult to employ joining techniques that rely on consistent mechanical interconnection or bonding to the surface. Whilst it is known to join bamboo by external bindings and by the application of resin supported wrappings of cloth-like materials, such arrangements have seldom provided reliable bonds and are often necessarily large relative to the diameter of the bamboo and are, thus, relatively stiff relative to the bamboo. The difference in relative stiffness between the fibrous material and the resin supported joint can result in premature joint failure as the joint is unable to flex in the same manner as the fibrous material it surrounds.

There, therefore, exists a requirement for a reliable method of joining portions of naturally grown fibrous materials to each other and to other articles which is able to more closely match the natural flexure and stiffness profile of the fibrous material it is joining and for products made by the joining method. This is particularly the case for bamboo and other such similar fibrous materials which are often very quick growing and, therefore, very economical to use in such products but are hitherto somewhat under-utilised.

Accordingly, the present invention provides a method of joining two or more ligneous parts comprising the steps:

a) providing two or more parts of ligneous material having surfaces it is desired to join;

b) placing said pieces in a desired positional inter-relationship;

c) applying a reinforcing material across the surfaces of said pieces and between said pieces; d) applying a resin to said reinforcing material such as to impregnate said material and contact the surface of said pieces of ligneous material; characterised by

e) applying said reinforcing material in the form of a woven material having both a warp (N) and a weft (P) direction and comprising tows of a plurality of fibres lain in side-by-side relationship, said tows being woven at an angle Θ to each other in each of the warp and weft direction of the woven material such as to form a woven structure having fibres in each tow extending in each of two parallel planes PL1, PL2.

Preferably, the reinforcing material in the form of a woven Hopsack weaves comprising tows of multiple single strands of flax material. In one preferred arrangement said parts are provided as bamboo parts.

The method may include the step of providing the reinforcing material in the form of a pre-formed cut-out having main surface portions and one or more cut-out portions having edges and wrapping said main portions around said two or more pieces of ligneous material (e.g. bamboo) and abutting said edge portions such as to present a reinforcing material with substantially no gaps between edges. One may apply two or more layers of reinforcing material to said two or more pieces of ligneous material. The said layers of reinforcing material may be applied at different orientations to each other such that the warp and weft of each layer extends in a different direction to that of a layer adjacent thereto. The method may include the step of confining said pieces and reinforcing material within a mould and applying said resin by injection thereof into said mould. Advantageously, said resin comprises a SP 106 Multi-Purpose Epoxy System. Preferably, said resin comprises S P106 resin and SP106 slow ha rdener in a ratio of su bstantially 5 : 1 vol ume ratio respectively. Preferably, the end composite has approximately volume fraction of fibre of 30%.

Advantageously, the method includes providing the reinforcing material in the form of a natural fibre. An example of a suitable fibre is flax. Adhesion may be improved by surface treating the surface of any portions of any pieces to which the resin is to be applied. Such surface treatment may comprise corona treatment or heat treating the surface. The heat treatment may include applying a flame to said surface in order to treat it. Said flame may be applied for between 5 and 30 seconds at a temperature of between 200 and 300 degrees C. Alternatively, the surface treatment may comprise shot blasting. Jointing of pieces may be performed by holding said pieces in a desired position by means of a jig having clamping means thereon for securely clamping said pieces in a desired position.

The method may include the step of cutting one or more of the pieces such as to provide a mating surface cut to correspond with a mating surface on an abutting piece. Such pieces may be in the form of tubular pieces.

The method may include the step by the step of including an inner fitment, such as a drop-out for example, having an inner portion for insertion within said pieces and an outer portion to remain outside of said pieces and applying said reinforcing material and resin over both the outer portion of said inner fitment and an outer surface of said piece.

The finished product may comprise a cycle frame, a piece of furniture or any one of a number of articles. According to another aspect of the present invention there is provided an article comprising a plurality of parts of ligneous material having a desired positional inter-relationship joined to each other by a reinforcing material and an adhesive characterised in that said reinforcing material comprises a woven material having both a warp (N) and a weft (P) direction and comprising tows of a plurality of fibres lain in side-by-side relationship, said tows being woven at an angle Θ to each other in each of the warp and weft direction of the woven material such as to form a woven structure having fibres in each tow extending in each of two parallel planes PL1, PL2.

Preferably, said material comprises a woven Hopsack weave comprising tows of multiple single strands of flax material. Said ligneous material may comprise bamboo. Preferably, the reinforcing material comprises a pre-formed cut-out having main surface portions and one or more cut-out portions having edges and wrapping said main portions around said two or more pieces of, for example, bamboo and abutting said edge portions such as to present a reinforcing material with substantially no gaps between edges.

Preferably, two or more layers of reinforcing material are applied to said two or more pieces ligneous material. Said layers of reinforcing material may be at different orientations to each other such that the warp and weft of each layer extends in a different direction to that of a layer adjacent thereto.

Preferably, the article includes an outer surface over said a formed joint being of resin material alone and having a pre-defined surface shape corresponding to that of a mould in which said article is formed.

Advantageously, the surfaces of said pieces comprise heat treated surfaces.

Preferably, said resin comprises a SP 106 Multi-Purpose Epoxy System and particularly preferably comprises S P106 resin and SP106 slow ha rdener in a ratio of su bstantially 5 : 1 vol ume ratio respectively.

Advantageously, the end composite has approximately volume fraction of fibre of 30%.

Advantageously, the reinforcing material comprises a natural fibre. The reinforcing material may comprise flax.

The article may include an inner fitment (drop-out for example) having an inner portion for insertion within said pieces and an outer portion to remain outside of said pieces and being affixed within said piece by reinforcing material and resin over both the outer portion of said inner fitment and an outer surface of said ligneous material(bamboo) piece.

The present invention will now be more particularly described y way of example only with reference to and as illustrated in the accompanying drawings, in which: Figure 1 is a representation of a cycle frame which is indicative of the sort of product that could be made with the present invention;

Figure 2 and 3 illustrate the profile cutting requirements when joining two tubes;

Figure 4 illustrates a tube cut in accordance with the requirements shown in figure 3;

Figure 5 illustrates a template that may be used to guide the cutting process;

Figure 6 illustrates an assembled tubular junction without a jointing system applied thereto;

Figure 7 illustrates the assembly of figure 6 but further illustrates the present invention applied thereto in a manner that illustrates the jointing arrangement;

Figure 8 is a plan view of the open weave structure of the material applied in the present invention to the joint of, for example, figure6;

Figure 9 is a cross-sectional view of the weave structure of figure 8 taken in the direction of arrows A-A; Figure 10 is a cross-section of the typical prior art arrangement of weave structure;

Figure 11 is a representation of a mould form for use in the manufacture of a finished bonded joint;

Figure 12 illustrates the mould of figure 11 with inserts used to prevent resin entering internal portions of the component to be produced;

Figure 13 illustrates the mould in an assembled state;

Figure 14 is an illustration of the joint of figure 6 with the resin joining system of the present invention applied thereto;

Figure 16 is an illustration of two types of insert that may be incorporated into the product of figure 1;

Figure 17 is a graph comparing the performance of an aluminium frame and a bamboo frame;

Figures 18 to 26 are graphs of performance characteristics;

Figure 27 is a graph illustrating failure profiles; and

Figure 28 is a graph illustrating the results of comparative deflection tests.

Referring now to the drawings in general but particularly to figure 1, which illustrates a typical product 10 that may be manufactured, it will be appreciated that such products generally comprise a number of parts 12, which may be tubular or of other forms such as flat elements, such as sheet material, or solid members, such as rods or the like and which are generally joined at ends such as to form the final product. In the example shown, the product comprises a bicycle frame 14 comprising a number of elements including a head tube joint 16, a top tube 18, a down tube 20, a seat tube 22, chain stays 24a, 24b, seat stays 26a, s6b and dropouts 28a, 28b.The head tube 16 joins the top tube 18 and the down tube 20, whilst a bottom bracket joint 30 joins the down tube 20, seat tube 22 and chain stays 24. A top tube joint 32 joins the top tube 18, the seat tube 22 and the seat stays 26, whist the drop-outs 28 are inserted into respective chain stays and seat stay pairs 24a, 28a and 24b, 28b. Each of the head tube joint 16 and bottom bracket joint 30 are provided with inserts 34, 36 to accept a bearing or bearing assembly (not shown) and the insert may be moulded into the product during the manufacturing process if desired.

Figures 2 and 3 illustrate the issue associated with joining tubular members and it will be appreciated that simple but jointing is not possible as the area of contact 38 between a bluff cut tubular end 40 and the external surface of a second tubular member 42 is very limited and does not form a good mechanical joint. Figure 3 illustrates an arrangement in which the end 40 has been cut to match the profile of the outer surface of tubular member 42 and, in this instance, the area of contact 44 (shown in dark) is greatly enhanced and forms the perfect basis for a good mechanical joint. The cut end is shown in more detail in figure 4 and from which it will be appreciated that a template of paper cut to the desired end profile may be used as a guide to the cutting process. The cutting process itself may take any one of a number of forms including hand cutting to the required profile or machine cutting. If machine cutting is employed this may be by means of a computer- numerically controlled (CNC) cutter or a simple circular cutter angled to cut across the tube and produce the desired profile. Figure 5 illustrates the shape of a template 46 suitable for wrapping around a tube used to define the end profile of the top tube 18 and from which one will appreciate that the end profile comprises a number of curved portions 48, 50, 52, 54 designed to match each of the junctions with adjacent tubes or head tube joint / bottom bracket joint portions 16, 30 (numbers need re-organising on drawings once we confirm inter-relationship). Figures 6 and 7 illustrate an assembled portion of the product 10 and from which (in figure 6) it will be appreciated that the end profiles of the tubes are each cut to match the circular external profile of the head tube 16 such as to provide a good mechanical fit. Figure 7 illustrates the lay-up for the reinforcing resin and re-enforcing material described in more detail later herein but comprising a number of layers and having edge to edge abutting edges shown generally at 56 and described in more detail later herein.

Figure 8 and 9 illustrate in detail the arrangement of the re-enforcing material 60 applied to the product of figure 1 and from which it will be appreciated that it comprises a plurality of individual strands of woven material comprising a plurality of fibres lain in side-by-side relationship in each of the warp and weft of the woven material, which subsequently forms the re-enforcing material for the finished product. Whilst a number of different naturally grown fibres may be used, the example of the drawing relates to a flax natural (vegetable) fibre, which is chosen for its high strength and low embodied energy. These material properties allow for a joint design that can be optimised for both strength and sustainability. Flax is stronger than all other natural vegetable fibres and grows in a similar manner to hemp and is, therefore, the preferred natural fibre for the present application. The flax is, preferably, formed in a continuous and 0-90 degrees woven format. Continuous fibres provide greater composite strength and stiffness then chopped strand fibres. Woven fibre provides high strength in multiple directions (0 and 90 degrees). The weave type is known as a hopsack weave. This has been found to be one of the strongest structural weave types available for fibre filled composite design. The reason for this appears to reside in the fact that the hopsack weave has less kinks, or deviations out of a normal plane, than conventional weaves and the individual strands remain predominantly in one or other of two parallel planes (A,B) and deviate from said planes only briefly and occasionally, as shown. Consequently, individual strands are predominantly planar and are, therefore, subjected to any load in a manner that causes said strands to take the strain of any load L very quickly rather than simply stretch by flattening. As shown in the drawing, each individual fibre 62 is arranged in a side by side relationship with a plurality of other fibres 62 to form a tow 63 and then a first tow 63a is woven in a first normal direction N such that a plurality of fibres 62 are woven over a plurality of fibres in a second tow 63b extending in the perpendicular direction P. In effect (and as shown), the individual fibres 62 are woven over a plurality (preferably 4 or more) other fibre strands 62 in the perpendicular direction P. The tows 63a, 63b extend predominantly in one of two planes PLl, PL2 and have very little deviation from that plane save for short lengths over which they pass between the planes PLl, PL2 and, consequently, the individual fibres 62 generally and predominantly extend in a plane equal to or parallel to a plane in which any load may be placed thereon. This plane normally being substantially parallel to a longitudinal axis X of the component 12 being jointed. This means that the individual fibres 62 are in the optimum position to be able to carry any load placed thereon as the load will be operating predominantly along the longitudinal axis LF of the fibre. This is in stark contrast with figure 10 which shows the more traditional weave arrangement for reinforcing materials known as plain weave where the end composite would be weaker because there are more kinks in the weave. I n th is weave each fi bre stra nd 64 is woven in and out of every other fi bre strand in the perpendicular direction and the fibre. The present invention exploits the above properties and further enhances them by more closely matching the mechanical properties of the material used in the fibre 62 to that of the material being used in the part 12 which is being jointed. In the preferred arrangement the bamboo of the component 12 to be joined is matched with flax fibres as flax possesses very close mechanical properties to that of bamboo. It will be appreciated that other materials may be used but that an optimum joint will be obtained by closely matching the material properties of the fibres 62 to that of the component 12 being jointed.

Figures 11 to 13 illustrate a mould 66 that may be used in the performance of the method of manufacture described in the claims and comprises a lower and an upper portion 68, 70. The lower portion 68 includes a void 72 for receiving a jointed portion as shown in, for example, figure 6 and includes outlets 74, 76 for accommodating any portions of the article extending from the joint. A peripheral seal groove 78 is provided around the exterior of the void 72 for accommodating a seal 80 (fig 12) which will help retain resin material within the mould once injected. Recesses 82, 84 may be provided to accommodate blanking plates 86, 88 as shown in figure 12 which may be used to blank off any interior portion of the product or an insert provided therein as, otherwise, resin may penetrate into the insert. Examples of such inserts include hollow tubular members, such as may be used for bicycle headsets/fork arrangements and other mechanical fixtures which need to be incorporated into the product but not bonded thereto. Each of the outlets 74, 76 may also be provided with a recess 90, 92 for receiving a seal (not shown) which may be a circular seal provided temporarily around the portion of the product being inserted into said outlet 74, 46. A number of clamping bolt arrangements 94 are provided around the periphery of the mould and are used to secure the upper and lower portions 68, 70 together as and when desired such as to clamp the product within the mould cavity and allow for the injection of resin material through inlet(s) 96 into a space (not shown) between the product and the cavity walls 98.

Figure 14 illustrates the finished joint 100 which is as shown in figure's 6 and 7 but now shows an enveloping and impregnating resin cover 102. The resin having been injected through inlets 96 such as to space fill any gap (not shown) within the mould and impregnate the reinforcing material which has been applied to the joint itself. The exterior of the finished joint will reflect the surface finish and shape of the void within the mould and, hence, may be a smooth or decorative surface. As shown, the surface comprises a smooth surface with gently flowing blend lines 104, 106 as the resin joins one portion to the other. Such a blended finish will help with the stress dissipation and also provides a more aesthetic appearance. Figure 16 illustrates one of a number of possible inserts that may be incorporated into the product of the present application. In this example the insert comprises a pair of drop-outs for a bicycle wheel (not shown), each of which have insertion portions 108, 110 for insertion into the interior of the tubular chain stays 24 and seat stays 26 (fig 1). The inserts may be bonded into the stays by means of conventional bonding techniques not discussed further herein and may also, or alternatively,, be secured therein by means of an externally applied wrap of resin impregnated reinforcing material.

It will be appreciated that the above mould and insert process may be applied to any one of a number of articles and that the bamboo bicycle is but one example of a suitable product.

Manufacture of a product will now be more particularly described with reference to the above description and figures 1 to 16. Manufacture comprises a number of steps which commences with the selection of the desired grade and size of members 16, 18, 20, 22, 24, 26, 30 etc and the cutting of them to the desired length and end shapes as illustrated in figures 4 to 6 for each of the joints required. As mentioned, a template 46 may be incorporated for each member such as to provide a guide for cutting or the cutting process may be automated or semi-automates in the manner well known to those skilled in the art and, therefore, not described in detail herein. Once the members have been correctly cut and the ends finished so as to provide an acceptable jointing surface the members are provided with seals are assembled together into the shape of the finished product before being each clamped in their respective positions such as to maintain the desired positional relationship whilst the reinforcing material is applied. Application of the reinforcing material may take one of a number of different forms but, generally, the re-enforcing material comprises a number of layers of the cloth like material discussed above and having edge to edge abutting edges shown generally at 56 (fig 7). The reinforcing material may be cut to a template shape selected such as to allow the material to be wrapped around the joint as shown in figure 7 such as to produce the desired edge to edge abutment. Several layers may be provide, each of which has a different position for the edge to edge abutment, thereby to maximise the strength of the finished joint. The layers may be pre-impregnated with resin material when they are applied to the joints or the impregnation may be achieved during a subsequent resin injection process step. Once the layers have been applied the joint is ready for clamping between the two portions 68, 70 of the mould 66 before the seal (not shown) is applied around the ends of any members being inserted into a mould. Such seals may take the form of a circular seal rolled over the member before it is assembled and which may be simply removed after the moulding process. Blanking plates 86, 88 may be inserted as and when desired such as to blank off any open ends within the assembled joint and a releasing agent may be applied where necessary before the two portions of the mould 66 are then securely clamped to each other by inserting and applying the clamping bold assemblies 94. This sandwiches the members and the reinforcing material within the void 72 to create a gap G therebetween which will be filled by resin which is injected through inlets 96. Resin injection is done under pressure and continued until excess resin is seen to be issuing from risers or form the seals around the members themselves which is indicative of full saturation. Once resin injection is completed, the joint is allowed to cure. Such curing process may be accelerated by means of the application of heat but is preferably conducted at room temperature. Releasing the mould 66 will expose the finished surface Whilst it will be appreciated that a number of resins may be used, it is preferred that the resin comprise an SP 106 Multi-Purpose Epoxy System. Preferably the resin comprises SP106 resin and SP106 slow hardener in a ratio of substantially 5:1 volume ratio respectively. The finished product preferably has approximately volume fraction within the area surrounding or creating the joint of 30% fibre, with the remainder being resin. In addition, whilst it will be appreciated that a number of reinforcing materials may be used it is preferred that the material be of a woven Hopsack weave comprising a weave of multiple single strands of flax material. It is also preferable that multiple layers of reinforcing material are layered over each other such that the orientation of two successive layers is not the same, thereby to present multiple directions of filaments of reinforcing strands to any applied load.

In addition to the above processes, it may also be desirable to treat the surfaces of the pieces being joined to each other such as to help improve the bond. Whilst a number of surface treatments are available which will raise the surface energy thereof, it has been found that heat treatment of the surface is particularly effective in creating a better bonding surface. In such a process, the surface may be heat treated by the application of a flame for a given but relatively short period of time which helps raise the surface energy thereof and modifies the surface such as to make it more suitable for bonding to. The temperature of the flame is preferably within the temperature range of between 200 deg C and 300 deg C. The heat may be applied for between 2 and 6 seconds, although other durations may be desirable in certain circumstances. The heat treatment creates a discharge which results in an ionised gas which forms oxidation on the surface of the portion being treated which in turn increases the "wettability" of the surface. Alternative surface treatments may include grit blasting, corona surface treatment and machine finishing in which a portion of the surface is removed possibly to provide a more consistent shape and dimensional stability to the finished component.

The performance of a finished product will now be discussed with reference to figures 17 to 28 and from which it will first be appreciated that the performance has been compared to that of an aluminium bicycle frame. Figure 17 illustrates that the bamboo frame has substantially the same I nsta ntaneous Am pl itude ratio over Freq uency Ra nge to that of a n al uminiu m bicycle and, consequently, will provide a rider with substantially the same "feel" or "ride" as a more expensive aluminium framed bicycle.

Figures 18 to 26 illustrate the performance of differently surface treated arrangements.

Figure 27 is a graph showing percentage substrate failure for different surface treatments and from which it will be appreciated that the corona surface treatment (1) produced enhanced properties in each of the three samples of Control, Test condition and an eight week aged sample. The other samples include the flame (2) and grit blasted surfaces (3), as discussed above.

Figure 28 illustrates the deflection of the bottom bracket of the product of figure 1 when tested in a jig against an earlier bamboo arrangement (A) a proportionately much heavier steel frame (B) and the product of the present invention (C). From this it will be appreciated that the product of the present invention performs much better than the earlier arrangement and nearly as well as the heavier steel frame.

It will be appreciated that the present invention may be applied to any one of a number of ligneous materials but is particularly suited to the application of natural grown materials such as timber, ligneous material - including bamboo and other such materials. Some such materials may be relatively fast growing and others may be relatively slow growing but all are natural in that they grow without the intervention of man and do not comprise artificially made fibres or elements. It will be appreciated that individual items described above may be used on their own or in combination with other items shown in the drawings or described in the description and that items mentioned in the same sentence as each other or the same drawing as each other need not be used in combination with each other. In addition the expression "means" may be replaced by actuator or system or device as may be desirable. In addition, any reference to "comprising" or "consisting" is not intended to be limiting any way whatsoever and the reader should interpret the description and claims accordingly.