The subject of the invention is a bamboo carbon fibre composite pipe primarily for bicycle fames. The subject of the invention also includes its production procedure.

The state of the art includes the following solutions.

Chinese patent document No. CN102392535 B describes a bamboo reinforced with carbon fibres, which material has excellent characteristics, bending strength, and oppressive strength. The devices is made of a special kind of dried bamboo and is used as a supplementing tool to the construction and reinforcement of the holding frame, for the primary purpose of supplementing the steel frame. It cannot be made of thin plywood, but must be made of the plant itself.

Chinese publication document No. CN103659989 A describes a procedure for the manufacturing of environmentally friendly bicycle frames made of bamboo. The procedure consists of 5 steps. The frame may be made of bamboo plywood. The mentioned materials are used to achieve energy efficiency, more strength, and easy weight. The device does not include carbon fibre or resin.

International publication document No. WO2012037748 Al describes a procedure for manufacturing environmentally friend bicycle frames made of bamboo.

The solution described by international patent document No. WO2013157771 Al is a bamboo bicycle frame reinforced with carbon fibres. The bamboo pipes are made of laminated plates by gluing.

Chinese utility model No. CN201189926 Y describes a safe, easy, practical, and environmentally friendly bicycle with a frame made of bamboo. The frame of the bicycle is reinforced with carbon fibre and resin-based glue. The used bamboo is applied in its natural form.

The description of several home-made bicycle solutions with bamboo frame is available online. These solutions use bamboo primarily for environmental considerations. Bamboo is used in its natural form, only its surface is treated to protect against fractures. These solutions have numerous disadvantages that are mostly due to home-production. They are made at home, meaning that the manufacturing is imprecise, slow, and costly. These procedures cannot be automated are unsuitable for industrial production. The structure of the bamboo remains unaltered in the course of assembling the frame, meaning that the diameter of the bicycle frame tube remains the same as that of the used bamboo. The manufacturing of carbon bicycle frames is entirely different structurally, but it may use similar procedures. However, they are made by using air-filled hose rolls, which method involves numerous disadvantages. In optimal cases, approximately 40 bar pressure may be achieved by air pumps, which is not enough to produce the structure at the expected quality level. However, the procedure becomes rather dangerous if even higher pressure is to be achieved by air compression.

Another disadvantage is that a solution relying on the use of the bamboo plant itself will require high quality plants in sufficient - very large - quantities.

The purpose of the invention is to eliminate the disadvantages of known solutions and to implement a structure and production procedure that exploits the advantageous characteristics of bamboo plants and enables serial production, and is an easy yet strong and stable structure, which can be primarily used for bicycle frames.

The inventive step is based on the recognition that it is advantageous to produce bamboo carbon fibre composite pipes using the material composition described in claim 1 and the production procedure described in the main procedural claim. This recognition enables the serial production of a strong and stable bamboo-based pipe structure with high precision, which is also easy and environmentally conscious.

According to the desired goal, the most general implementation form of the solution according to the invention is described in claim 1. The most general form of the production procedure is described in the main procedural claim. The various implementation forms are described in the sub-claims.

The solution in general is a bamboo carbon fibre composite pipe structure, primarily for bicycle frames.

A distinctive feature of the invention is that it has a bamboo plywood layer and a carbon fibre layer, and the bamboo plywood layer and the carbon fibre layer is fixed to each other with epoxy resin, polyester resin, or polyurethane resin. Another implementation form may be where the surface of the bamboo plywood layer is coated with a cellulose layer to prevent fractures.

Another implementation form may be where the thickness of the bamboo plywood layer is between 0.1 and 5 mm, typically between 0.5 and 1.5 mm.

Yet another implementation form may be where the weight of the carbon fibre layer is between 80 and 300 g/m ² , but preferably between 100 and 200 g/m ² .

A distinctive feature of the general production procedure is that the bamboo plywood layer and the carbon fibre layer is fixed to each other with epoxy resin, polyester resin, or polyurethane resin, and then they are rolled onto a hose roll or other inflatable roll-shaped tool, and then they are placed into a cover, and, in the next step, the hose roll or the other inflatable roll-shaped tool is pumped up with oil, thereby it is pressurized from the inside, and then the cover is removed after the resin solidified.

Another possible distinctive feature of the procedure is that the bamboo plywood layer may be covered in a cellulose layer in advance.

Another implementation solution is that a cover removal tool is placed onto the rolled layers before they are placed into the cover, which cover removal tool is preferably a silicone tube or plastic insert.

Another distinctive feature may be that a heated metal template is used as cover.

Yet another distinctive feature is that the solidification of the resin is accelerated by heating after placement into the cover, and heat is preferably provided through the cover, by heating the oil, or by applying heat treatment after the removal of the cover.

The invention is presented in more detail on drawings pertaining to the various implementation forms.

On the attached drawings,

Figure 1 shows an axonometric drawing of the structural layers, and

Figure 2 shows an axonometric drawing of the production of the pipe.

Figure 1 shows that the carbon fibre layer 2 is placed onto the bamboo plywood layer 1. The bamboo plywood layer 1 is covered in advance with a cellulose layer to prevent fractures, and then it is treated with epoxy resin, polyester resin, or polyurethane resin. The application of the cellulose layer is not a necessary step of the procedure and may be omitted. In this case, the carbon fibre layer 2 is placed onto the bamboo plywood layer 1 at an earlier stage. The base material of the bamboo plywood layer 1 is a 0.1 to 5 mm, preferably 0.7 mm thick layer, and the base material of the carbon fibre layer is canvas, twill, or other fabric the weight of which is between 80 and 300 g/m ² , preferably 100 and 200 g/m ² , depending on the desired strength of the composite material. From among the above-mentioned resins, epoxy resin should be used primarily due to its strength.

Figure 2 shows a situation when the composite material consisting of a bamboo plywood layer 1 and a carbon fibre layer 2, fixed to each other with resin, is rolled onto the hose roll 3. This process is part of the production procedure used for producing the pipe structure used primarily for bicycle frames. Other similarly shaped inflatable tools may also be used instead of the hose roll 3.

During the production of the invention, the bamboo plywood layer 1 is covered with an epoxy resin, polyester resin, or polyurethane resin layer, according to the desired result. The base material of the bamboo plywood layer 1 is a 0.1 to 5 mm, preferably 0.7 mm thick layer, which is preferably covered in advance with a cellulose layer to prevent fractures. As for the resin types, a slightly flexible type of epoxy resin should be preferred. Then, or in the previous step instead of the cellulose layer, the carbon fibre layer 2 is placed onto the bamboo plywood layer 1. The resulting layered material is then rolled onto the hose roll 3 or other similarly shaped inflatable tool. A cover removal tool, such as a plastic insert of a silicone tube, is placed onto the external side of the layers, so that the structure could be removed from the cover after the solidification of the resin easily and without damages. Then, it is placed into a metal casing or other suitable cover, dismountable shape or template, preferably a dismountable and heated metal template. In the next step, the hose roll 3 or the other tool used in its place is inflated, filled with oil, so that high pressure, preferably between 50 and 200 bars, is achieved. The pressure achieved this way is much higher than the pressure that could be achieved by filling up the hose roll 3 with air, making the resulting structure more dense and higher quality. Heat treatment is used to solidify the resin and to achieve cross-bonding, which heat treatment may be applied either retrospectively or during the time when the structure is placed into the metal casing. If the heat treatment is not applied retrospectively, then it can be applied by using a heated cover or by heating the oil itself. The metal cover is removed after the resin becomes solid. The presented structure has numerous advantages. An advantage of the invention is that it can be used to produce easy bicycle frames, so that the weight of the bicycle remains small, which is important both for day-to-day and competitive use. Due to the characteristics of the bamboo material, the structure has good bending strength and oppressive strength. The structure is also very strong, can absorb vibrations with high efficiency, and, due to the procedure, is also very resistant. The composite material according to the invention can be used to produce other devices as well, where strength and small weight are both important. The structure is primarily used for bicycle frames, but it can be suitable for any other use where, in addition to the above-mentioned mechanical characteristics, the appealing appearance of the bamboo is required or advantageous. For example, it can be used as the framework of temporary constructions, such as pavilions and tents, where high on-site construction speed is expected and the light structure is advantageous. It can be also used as the material of supporting structures and ladders, or it can be used to build other modules, jungle gyms, or custom-built pieces of furniture. One of the most important advantages is that we can implement a structure that is suitable for industrial production, while retaining the advantageous characteristics of bamboo plants. Another advantage is that, due to the use of oil, a sufficiently high pressure can be achieved that results in high quality and dense structures. Another advantage is that the described composite material and procedural steps are suitable for industrial application. It is also an advantage that polyester resin or polyurethane resin can be also used in place of epoxy resin. The removal of the template can be facilitated by various means, including the use of a silicone tube, a suitable plastic insert, or plastic chops. This is necessary to prevent the possibly overflowing resin from damaging the structure or making the pipe structure stuck into the shape. There is also significant freedom in selecting the carbon fibre to be used; the fineness, texture, and weight should be determined according to the desired strength of the composite material. It is also advantageous that the carbon fibre can be pasted onto the bamboo plywood in advance, in which case there is no need for a cellulose layer. It is also advantageous that the heat treatment can be omitted, if the structure is heated when it is placed into the metal casing, for example by the heated cover (i.e. the metal casing), or by heating the oil itself. The invention does not waste any bamboo, since the massive structure can be implemented using bamboo plywood plates that are only a few times thicker than the tenth of a millimeter. It is advantageous that the resin can become solid in just a couple of minutes, so that the procedure can be accelerated.

In addition to the above examples, the invention can be implemented in other forms and with other production procedures within the scope of protection.