Patent Application
20230356446
The present application claims priority to German Patent Application No. 10 2022 110 819.8 filed on May 3, 2022. The entire contents of the above-listed application are hereby incorporated by reference for all purposes.
The disclosure relates to a method of manufacturing a plastic component having at least one hollow space in the interior, said plastic component being a handlebar for a two-wheeler. A two-wheeler in the sense of the disclosure can, on the one hand, be a conventional bicycle or an electric bicycle. A two-wheeler is, however, furthermore also to be understood as a motorized two-wheeler having a motor/engine such as a motor-assisted bicycle, a moped, a motorcycle, as well as motor scooters and electric scooters.
It is already known to manufacture bicycle handlebars from plastic. For this purpose, a resin injection process is typically used that is known under then name “resin transfer molding” (RTM). In this method, glass fiber fabric and/or carbon fiber fabric are placed into a molding tool. With a closed tool, the fabric is saturated with a thermosetting matrix material such as an epoxy resin or polyurethane that is injected into the tool. The thermosetting matrix materials usually comprise two base substances that have to be mixed well with one another before the introduction into the tool. A chemical reaction takes place after the mixing and the injection into the tool. The component can be demolded after a corresponding conversion of the reactants.
The glass fiber fabrics or carbon fiber fabrics are typically arranged in the tool in a three-dimensionally woven state. An inflatable tube is furthermore placed into the interior of the fabric so that the tube can be inflated with a fluid after the resin injection of the tube in the component interior and a hollow space is created in the component. The fluid introduced under pressure is released after the end of the reaction of the reactants. The hardened component can subsequently be removed.
Bicycle handlebars comprising thermosetting matrix material have the great disadvantage in addition to increased production costs that they cannot be sensibly recycled due to the selected material. Apart from a thermal exploitation by combustion there is no reasonable recycling for the components manufactured from thermosetting matrix material.
The aforesaid disadvantages could be remedied by a plastic having thermoplastic material properties. However, completely manufacturing bicycle handlebars from thermoplastics was not done in the known methods due to the poor material properties with regard to the required stability of a bicycle handlebar. Finally, the handlebar is a safety-related component with which a fall or a hard impact from the surface can cause a handlebar fracture with serious consequences. High forces that, in addition to the risk of a handlebar fracture, likewise contribute to a constant strain on the handlebar typically already act on the handlebars on the acceleration and braking of the two-wheeler.
Starting from the disadvantages outlined above, it is therefore the underlying object of the present disclosure to provide a reliable method with which a two-wheeler handlebar can be manufactured completely from a thermoplastic, that satisfies safety-related demands, and that can be recycled in a simple manner.
In accordance with the disclosure, a method of manufacturing a component of thermoplastic in accordance with the features of claim 1 having at least one hollow space in the interior for a two-wheeler by means of plastic injection molding is provided to achieve this object in accordance with the disclosure, with preferred embodiments being the subject of the dependent claims.
The method in accordance with claim 1 accordingly takes place as follows:
The sequence of the method in accordance with the disclosure can selectively be adapted by the following steps:
The fluid used is generally water or gas. It can, however, also comprise both media since, for example, an air bubble is frequently pushed ahead of the water or with nitrogen first being used for forming the hollow space and subsequently CO2 being used for cooling the component.
In the method in accordance with the disclosure, a cavity of the closed injection molding tool forms the geometry of the component to be produced, wherein a handlebar for a two-wheeler is provided in accordance with the disclosure. The injection molding tool is equipped with at least one injector for the introduction of a fluid. The fluid is able to displace the plastic core from the interior of the component and thus to form a tubular cross-section of the handlebar. In this process, the fluid can be injected with a regulation of volume flow or pressure/time via a preset profile. The cool-down phase of the hot plastic melt can be substantially reduced by the tubular cross-section due to the comparatively thin remaining residual wall thickness. This means that only a comparatively brief cooling time is required.
The method in accordance with the disclosure is characterized overall by a very considerable cooling time reduction with respect to a handlebar of a solid material. The process time for the manufacture of a two-wheeler handlebar can be substantially shortened due to the faster cooling time. It is therefore possible to produce a hollow-walled handlebar for a two-wheeler in a very cost efficient manner with respect to previous methods. The mass of the total two-wheeler frame is furthermore considerably reduced due to the hollow space at the component interior, which not only brings about a weight advantage, but also in particular an economic advantage. A higher stiffness can also be assumed with a closed tubular cross-section. When a tubular cross-section is spoken of here, it can naturally be formed as circular, oval, polygonal, and in any other desired shape.
Advantageous embodiments of the disclosure result from the dependent claims following on from the main claim.
Provision is accordingly made in an advantageous embodiment of the method in accordance with the disclosure that a set fluid pressure of the at least one fluid is maintained over a specific time period in the interior of the component and is blown out, expelled, and/or sucked out after the maintenance.
Provision can further be made in an alternative variant of the method in accordance with the disclosure that the at least one fluid presses the plastic core, for example, into an overflow cavity introduced in the injection molding tool.
In accordance with a further possible embodiment of the disclosure, more than one overflow cavity and/or more than one injection point can be provided in the injection molding tool.
Provision is made in accordance with a variant of the method in accordance with the disclosure that the component is manufactured by the so-called mass back pressure process, wherein the at least one fluid displaces the plastic core back through a channel into the screw antechamber of the injection molding machine and wherein the at least one fluid is injected on the side of the component disposed opposite the corresponding injection point of the melt.
In accordance with an again advantageous embodiment of the method in accordance with the disclosure, the at least one shaping component cavity introduced into the injection molding tool is only partially filled with the advantageously thermoplastic melt and the plastic core is displaced by the injection of the fluid, with the liquid melt being inflated such that it is placed on the wall of the injection molding tool and a hollow space is created in the interior of the component. The at least one shaping component cavity is completely filled as part of this process. The inflation of the melt enables a very economic use of the thermoplastic provided for forming the handlebar.
Alternatively, at least one first shaping component cavity is used in the injection molding tool, with the at least one shaping component cavity being replaceable to generate any desired component geometries by means of additional shaping component cavities.
In accordance with a further advantageous embodiment of the method in accordance with the disclosure, additional metallic components to be integrated in the component such as components of aluminum and/or steel and/or non-metallic components such as pultruded woven or wound glass fiber tubes are placed into the injection molding tool individually or in groups and are back injection molded or overmolded.
In an alternative advantageous method process, unidirectional tapes and/or organosheets (a design and/or functional film and/or a tape of carbon or glass fiber fabric) are placed into partial regions or over a large area in the injection molding tool and are back injection molded, with a connection with the thermoplastic melt with material continuity being produced.
To achieve the best possible connection between the tapes and the thermoplastic melt, the tapes/organosheets can particularly advantageously be preheated to a specific temperature before the placing into the tool, with this specific temperature having to be selected in dependence on the matrix material of the tape.
Provision can alternatively be made that the unidirectional tapes and/or the organosheets are placed into the injection molding tool in a cold and/or in a hot state.
The tapes/organosheets can furthermore be positioned and held by a special apparatus in the tool, for example. The stiffness in critical regions of the component can in particular be increased by a goal-oriented fiber orientation of the tapes/organo sheets.
In accordance with a further advantageous embodiment of the method in accordance with the disclosure, the component is designed as a two-component part of hard and soft components, with components such as grip pieces on the plastic handlebar being formed as soft components that are produced by means of an index plate or turntable injection molding tool or by means of a second cavity arranged in the injection molding tool. Alternatively, provision can be made in accordance with another variant of the method in accordance with the disclosure that the spacers in the grip regions of the handlebar are formed as hard components that are co-injected in the first cavity. In the second cavity, the spacers serve as a centering aid to prevent a crumpling of the component on the injection molding of the soft components.
Another advantageous embodiment of the disclosure in turn provides that a stem is co-injected on the component so that the component and the stem form a common component or that the component has at least one defined interface for the attachment of the stem, with the interface being formed such that different stems correspond via a shape matched connection.
In accordance with an alternative advantageous method process, the at least one interface is an electronic interface for signal transmission.
The method in accordance with the disclosure can advantageously be designed such that water and/or gas, preferably nitrogen, is/are provided as the fluid to be injected that is injected via at least one injector arranged in the tool.
Another advantageous embodiment of the disclosure in turn provides that a plurality of fluids are injected into the injection molding tool and their individual fluid volume flows or pressure/time profiles are regulated separately from one another. On an introduction of a plurality of fluid volume flows by a plurality of injectors, they can be particularly advantageously regulated separately from one another.
In accordance with another advantageous embodiment, elements that are co-injected in the component such as brake lever mounts for brake levers, cable routings for cable lines for electronic signal transmission, or a bell can be integrated. Other elements can furthermore also be integrated in the component. In this case, the elements to be integrated in the plastic handlebar are placed into the injection molding tool individually or group-wise, are held by means of a holding device, and are overmolded with plastic. A handlebar assembly can take place in a particularly efficient and time-saving manner by this method sequence since the handlebar can be removed from the injection molding tool at the same time as the required components in this variant of the method in accordance with the disclosure.
Another advantageous embodiment of the disclosure in turn provides that elevated and/or recessed pockets are integrated in the component to hold elements such as light guides, headlamps, indicators, and/or comparable elements. The elements can be attached in the pockets on the handlebar, for example, on the final assembly of the bicycle.
To form a constant inner diameter, a projectile can additionally be used that has a cross-section corresponding to the hollow space of the plastic handlebar and that is driven forward through the shaping cavity of the injection molding tool by means of the fluid pressure.
Although the fluid primarily serves the formation of the hollow space in the plastic frame, it can thereby be provided with a second benefit in that it is conducted into a circulation flow after the formation of the hollow space so that it now serves the cooling of the plastic material that is still very hot directly after the injection process.
A plastic that is selected from the following groups can advantageously be used in the method in accordance with the disclosure: Polyamide, preferably polyamide 12, polyamide 6 or polyamide 6.6, polypropylene, polyethylene, polyethersulfone, polyetherimide, polyetherketone polyphenylene sulfide, polyvinyl chloride, polyester, acrylonitrile butadiene styrene (ABS), polycarbonate/acrylonitrile butadiene styrene (ABC/PC), polycarbonate (PC), and particularly preferably polybutylene terephthalate or polyterephthalate ethylene. These plastics can here be selected and used individually or in combination. The selected plastics can furthermore also be reinforced via short fibers and/or long fibers composed of glass fibers, carbon fibers and/or natural fibers.
The plastic can alternatively also be injected in the injection molding tool as a caprolactam with an associated activator and can be polymerized in the heated tool.
The handlebar comprising the thermoplastic matrix material can be recycled and thereby reused at any time.
Due to the positive property that the handlebar produced by the method in accordance with the disclosure consists of a thermoplastic, it is not electrically conductive, whereby a disruption free transmission of signals, data, and/or energy can take place. An additional cabling to conduct the produced energy from an energy-generating unit such as a dynamo to the consumer, for example to a bicycle lamp, could also be implemented by means of a correspondingly functionalized film in the hollow space of the component.
The handlebar has a small temperature conductivity due to the advantageous property that it is produced from plastic. This property can in particular be of advantage under poor weather conditions and/or at temperatures below freezing point since the rider can hold the handlebar with one hand (also without gloves) when pushing the bicycle, for example in the region of the stem, without the hand on the handlebar becoming cold as fast as on the holding of a metal handlebar. For due to the high temperature conductivity capability of metal handlebars, the hand on the handlebar cools substantially faster, whereby the rider is no longer able to hold the handlebar in the aforesaid manner after only a short time.
The disclosure finally relates to a handlebar of a thermoplastic for a two-wheeler that is manufactured in accordance with one of the aforesaid embodiments of the method in accordance with the disclosure. Provision can additionally be made in accordance with an alternative embodiment that the handlebar has a main handlebar part and two respectively replaceable end handlebar parts of thermoplastic.
Further details and advantages of the disclosure result from the embodiments shown in the following with reference to the Figures.
The Figures show:
In the embodiments in accordance with
A displacement of the plastic core from the component can generally take place in different manners. The components shown in
A blowing out of the material of the plastic core into an overflow cavity in accordance with
Finally, a blowing out process can also be provided, in which a smaller quantity of thermoplastic is introduced into the injection molding tool that is then inflated. The quantity of the plastic introduced is selected here such that no material is displaced from the injection molding tool on the inflation.
In the embodiments shown, preferably polyamide or polyolefin is used that is reinforced via glass fibers and/or carbon fibers and/or natural fibers.
The components 100 and 200 shown in
In accordance with the method in accordance with the disclosure, a plasticized plastic melt is injected at the injection point AS in the arrow direction of the arrow shown, while the fluid is pressed in the arrow direction of the corresponding arrow at the injection point AF after the injection of the melt through an injector not shown in any more detail here, that displaces the so-called plastic core from the interior of the component 100 and 200 respectively.
The tools placed in the injection molding tool form shaping component cavities here. It is possible with reference to these shaping cavities, that are not shown in more detail, to produce hollow-walled components in large volumes having a specific shape in the interior of the component.
In accordance with an alternative variant of the method, the at least one shaping component cavity can be replaceable to be able to produce any desired component geometries by means of additional shaping component cavities.
The plastic handlebar 202 can be additionally reinforced by additional stiffening elements like the ribs 206 and 208 shown in
As
In addition to the already named overflow cavity 112, the representation in accordance with
In accordance with another variant of the method in accordance with the disclosure, more than one overflow cavity 112 and/or more than one injection point AS and AF can also be provided in the injection molding tool, in particular with complex designs of the component 100 and 200.
In accordance with the representation of
In accordance with
The sectional representation of
To increase the strength of the handlebar structure, in accordance with an alternative variant of the method in accordance with the disclosure, unidirectional tapes and/or organosheets 230 can be placed into partial regions of the injection tool or over a large area into the injection tool and can be subsequently back injection molded in the component prior to the injection of the plastic melt. A connection with material continuity to the thermoplastic melt is formed here. A structural failure of the handlebar can be precluded in this manner, even on particularly high strains.
As shown in
In addition to the possibility of designing a handlebar produced by means of the method in accordance with the disclosure shown in
All in all, the present disclosure represents an excellent solution with respect to the manufacture of components of thermoplastics for two-wheelers.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 110 819.8 | May 2022 | DE | national |
