MOLD FOR THE MANUFACTURE OF A BICYCLE FRAME AND METHOD FOR MANUFACTURING SUCH A FRAME BY INJECTION USING SAID MOLD

Abstract

The present invention relates to a mold (1) for manufacturing a one-piece bicycle, tricycle, quadricycle, or motorcycle frame (32) by injecting a polymer material, the mold (1) comprising a fixed part (2) and a movable part (3) capable of moving towards or away from the fixed part to close or open the mold respectively, which together delimit a molding cavity (8) of the frame when the mold is closed, the mold (1) being characterized in that: - it comprises at least three sliders (15, 16, 17, 18), capable of being inserted into respective cavities (11, 12, 13, 14) of the molding cavity (8) whose positioning within said molding cavity and profile correspond to parts of the frame to be manufactured, said sliders (15, 16, 17, 18) being intended to be overmolded with polymer material during a molding operation so as to form said parts of the frame (32), - at least two of these sliders (15, 16, 17,18) are engaged with each other when in position in their respective imprint, thus forming a solid structure capable of resisting injection forces. Figure for abstract: Fig. 1,

Description

Title of the invention: MOLD FOR THE MANUFACTURE OF A BICYCLE FRAME AND METHOD FOR MANUFACTURING SUCH A FRAME BY INJECTION USING SAID MOLD Technical field of the invention

[0001] The present invention relates to a mold for manufacturing a bicycle (or bike), tricycle, quadricycle, or motorcycle frame by injecting a polymer material into said mold.

[0002] The invention also relates to a method of manufacturing a bicycle, tricycle, quadricycle or motorcycle frame by injecting a polymer material into such a mold. Technological background

[0003] In the field of bicycle frame manufacturing, the main constraints for manufacturers are to obtain a lightweight frame while limiting costs and production time.

[0004] Some frames are made by welding or gluing aluminum or steel tubes or profiles. This type of manufacturing offers the advantage of being simple and inexpensive to implement, but the quality of the resulting frame is just average, and is therefore only suitable for entry-level bikes.

[0005] Another manufacturing technique is based on carbon composite draping with vacuum curing of an epoxy resin. The draping operation consists of cutting plies of raw material, called pre-pregs, and draping them manually in a mold which will provide the shape of the part. Silicone bladders can be used for the production of composite parts with complex shapes, particularly for the production of hollow bodies.

[0006] This second manufacturing technique leads to high-end and lightweight frames, but very expensive due to the high production costs (particularly labor). Furthermore, the tolerance interval when inflating the bladders generally leads to disparities in the structure of the frame, and in particular to variations in thickness within the same frame but also from one frame to another, which poses problems of precision and repeatability.

[0007] A third technique consists of making the frame by manufacturing then assembling of half-frame parts. However, this technique requires a connection between the half-parts, this connection being likely to lack robustness, sealing and / or geometric and dimensional stability over time. Document US 2012217722 describes a mold and a method using such a mold, for the manufacture of a one-piece bicycle frame, by injection of a polymer material obtained from recycled polyethylene terephthalate bottles. In addition to the ecological aspect, this process makes it possible to reduce the risks of aging of the frame linked to the corrosion of steels, and to avoid anti-corrosion treatment operations which are costly and polluting. The frame obtained by this process is however relatively heavy, and is therefore not suitable for certain applications.

[0008] Another known method consists of implementing a mold for the manufacture of a single-piece frame by injection of a polymer material whose hollow bodies are obtained in a hybrid manner between drawers and hydraulic shaping (called water injection) of unhardened material.

[0009] Despite the undeniable advantages of existing methods, these are not entirely satisfactory, particularly with regard to the combined aspects of lightness of the frame obtained, precision of the structure of the frame, and repeatability of the method. Brief description of the invention

[0010] An aim of the invention is to propose a mold for the manufacture of a bicycle (or bike), tricycle, quadricycle, or motorcycle frame making it possible to automate the molding of the frame while controlling the thickness of material around the hollow bodies constituting the parts of the frame, for example the fork, the diagonal tube, the chainstays, the seat stays, or even the seat post.

[0011] The invention also aims to ensure good repeatability of the process, that is to say the obtaining of successive frames that are substantially identical as the molding operations progress, which all have a controlled and similar material thickness at the level of the different parts of the frame, and this with a contained process time, of the order of a few minutes, for example approximately 5 minutes.

[0012] The invention also aims to provide such a mold, leading to a lightweight frame.

[0013] To this end, the invention provides a mold for manufacturing a one-piece bicycle, tricycle, quadricycle, or motorcycle frame by injection of a polymer material, the mold comprising a fixed part and a movable part capable of moving towards or away from the fixed part to close or open the mold respectively, which together delimit a molding imprint of the frame when the mold is closed. The mold is mainly characterized in that: - it comprises at least three sliders, capable of being inserted into respective cavities of the molding cavity, the positioning of which within the molding cavity and the profile of which correspond to parts of the frame to be manufactured, said sliders being intended to be overmolded with polymer material during a molding operation so as to form said parts of the frame, - at least two of these slides are engaged with each other when they are in position in their respective imprint, thus forming a solid structure capable of resisting injection forces.

[0014] During molding, the polymer material, which advantageously comprises a thermoplastic polymer, is injected into the molding cavity, and covers the external surface of the slides then in position in their respective cavity of the molding cavity (so-called "closed" slides).

[0015] As a result, the sliders themselves act as molds for the various hollow parts of the frame being formed. By precisely adapting the profile and location of the sliders in the molding cavity, it is possible to adjust the structural and dimensional characteristics of the frame accordingly. The external profile of the hollow parts of the frame is also a function of the profile of the cavities in the molding cavity.

[0016] Furthermore, the sliders are in mechanical engagement with each other, that is to say they come into tight contact with each other, and are held in position. At least two of these sliders, preferably at least three, more preferably at least four, and even more preferably all the sliders, or all the sliders except one, are in engagement with each other. Preferably, the sliders are assembled, or more precisely are fitted into each other, by inserting a projecting part of a slider into a complementary shaped housing of a neighboring slider.A given slide may comprise a projecting part which fits into a housing of complementary shape in another slide, or it may comprise a housing receiving a projecting part of complementary shape in another slide, or both at the same time, depending on its positioning relative to the other slides and the evolution of the pressure within the molding cavity during the molding operation.

[0017] A consequence of this specific assembly is that the sliders are mechanically interconnected with each other, which forms a solid structure capable of resisting the injection forces exerted by the polymer material during its injection into the molding cavity. Thus, the sliders remain immobile in position in their respective cavity within the molding cavity throughout the duration of the injection, which guarantees regularity in the thickness of the layer of polymer material overmolded on the sliders, that is to say the thickness of the hollow bodies constituting the structure of the frame obtained at the end of the process.

[0018] This results in a frame with controlled thicknesses and tolerances, not only for the first frame, but also for all the frames subsequently manufactured in this mold, which translates into excellent repeatability.

[0019] In addition, the mechanical forces applied to the slides depend on the flow of polymer material during filling. In practice, this flow is unbalanced and it is difficult to position the weld lines in the most advantageous locations, i.e. the most mechanically resistant. The solid structure formed by the slides held in position in their molding imprint allows this freedom of positioning of the weld lines.

[0020] This specific structure also makes it possible to provide more slender slides compared to other state-of-the-art frame manufacturing molds. As a result, the size of the mold is reduced, and that of the press is also reduced, resulting in a reduction in production costs (reduction in the depreciation costs of the press investment).

[0021] The frame is formed from a set of hollow parts or hollow bodies made of polymer material, which makes it light and strong, all with a contained volume of material, thus making it economically interesting.

[0022] This frame is “monobloc” in that the hollow parts form a single hollow assembly (the complete frame) made of polymer material.

[0023] The manufacture of a single-piece frame makes it possible to avoid assembled half-frame parts with recurring weaknesses of the assemblies, such as the lack of robustness, sealing and / or geometric and dimensional stability over time. By nature (human size). This type of manufacturing also leads to a reduction in the assemblies of frame components (automation), which makes it possible to automate the process in order to improve production rates and reduce production costs.

[0024] According to other aspects, the mold according to the invention has the following different characteristics taken alone or according to their technically possible combinations: - at least two of the slides are provided with at least one housing adapted to receive a projecting portion of complementary shape of a neighboring slide, so that when the slides are in position in their respective imprint, said slides are nested into each other. This nesting or embedding leads to a stronger connection of the slides between them, which ensures increased solidity of the structure; - the mold includes at least three of the following corresponding impressions and slides:

[0025] - a first imprint having a profile of the frame fork pivot, and a first slide adapted to be inserted into the first impression, - a second impression which communicates with the first impression, having a diagonal tube profile of the frame, and a second slider adapted to be inserted into the second impression, - a third print which communicates with the second print, presenting a base and stay profile, and a third slider adapted to be inserted into the third impression, - a fourth impression which communicates with the third impression, having a seat post profile, and a fourth slider adapted to be inserted into the fourth impression; - at least two of the following slides are provided with at least one housing such that:

[0026] - the first slider is provided with at least one housing adapted to receive a projecting portion of the second slide, - the second slider is provided with at least one housing adapted to receive a projecting portion of the third slider, - the third slider is provided with at least one housing adapted to receive a projecting portion of the fourth slider; - considering that the molding impression is positioned in a conventional direction of use of a bicycle, a tricycle, a quadricycle, or a motorcycle:

[0027] - the first slide is inserted from below the mold, in a direction of the fork pivot, - the second slider is inserted from below the mold, in one direction of the diagonal tube, and fits into the first slider, - the third slide is inserted from the rear of the mold, and fits into the second slide, - the fourth slider is inserted from above the mold, in one direction of the seat post, and fits into the third slider. - the mold includes at least one of the following injection points:

[0028] - at least one injection point located on the fork pivot, preferably at least two injection points preferably located at the two ends of the fork pivot, - at least one injection point located on the down tube, - at least one injection point located on the seat post, - at least two injection points located on a front portion of each base, i.e. close to the pedals, - at least two injection points located on a rear portion of each base, i.e. at the level of the junction of the bases and the shrouds.

[0029] The invention also relates to a method of manufacturing a bicycle, tricycle or quadricycle frame by injecting a polymer material into a mold as described above.

[0030] This method comprises the following steps: - supply of a mold as described above, - closing the slides in order to engage them with each other, preferably to fit them into each other, and closing the mold by moving the moving part towards the fixed part until they come into contact so as to delimit the molding imprint, - hot injection of a polymer material into the molding cavity, overmolding the sliders in position in their respective cavity, to form the frame, - opening of the slides, and opening of the mold by separating the fixed and mobile parts to release the frame, - frame ejection.

[0031] According to other aspects, the method according to the invention has the following different characteristics taken alone or according to their technically possible combinations: - the method further comprises a step of external ribbing of the bases of the frame; - the method further comprises a step of internal ribbing of the frame stays; - the polymer material is injected into the molding cavity by injection points, the injection being carried out from the front of the frame, i.e. an injection point opening onto a fork steerer cavity or a down tube cavity, towards the rear of the frame, i.e. an injection point opening onto a chainstay and seatstay cavity or a seatpost cavity; - the polymer material is a composite material comprising a polymer matrix and a fibrous reinforcement, said fibrous reinforcement having a content of between 30% and 60% by weight relative to the total weight of the composite material. Preferably, the polymer matrix is ​​a thermoplastic polymer matrix comprising at least one thermoplastic polymer; - the polymer constituting the polymer matrix is ​​chosen from: polyacrylamide 6, polyacrylamide 12, polyacrylamide 6 / 66, polyacrylamide 610, polyacrylamide 66, polyacrylamide 66 / 6, polyaryletherketone, preferably polyetheretherketones and polyetherketoneketones, polybutylene terephthalate, polyethyleneimine, polyethylene terephthalate, glycolized polyethylene terephthalate, polycarbonate, polymethylpentene, polyoxymethylene, polyphenylether, polytetrafluoroethylene, polyvinylidene fluoride; - the fibers constituting the reinforcement are chosen from: carbon, linen, hemp, jute, basalt, aramid acrylic, fiberglass, iron, coconut, aluminum, titanium, tungsten, copper, magnesium, sisal. Description of figures

[0032] Other advantages and characteristics of the invention will appear on reading the following description given by way of illustrative and non-limiting example, with reference to the following appended figures:

[0033] [Fig-1] [Fig.l] is a perspective view of the mold according to the invention, in confi open structure, the slides all being open;

[0034] [Fig.2] [Fig.2] is a perspective view of the mold of [Fig.l], in which the first slider is closed, in position in a fork pivot imprint;

[0035] [Fig.3] [Fig.3] is a perspective view of the mold of [Fig.2], in which the second slider is closed, in position in a recess of the down tube, and in engagement with the first slider;

[0036] [Fig.4] [Fig.4] is a perspective view of the mold of [Fig.3], in which the third slider is closed, in position in an imprint of the bases and the shrouds, and in engagement with the second slider;

[0037] [Fig.5] [Fig.5] is a perspective view of the mold of [Fig.4], in which the fourth slider is closed, in position in a recess of the seat post, and in engagement with the third slider, all the sliders being thus closed;

[0038] [Fig.6] [Fig.6] is a perspective view of the mold of [Fig.5], said mold being closed by contact of the fixed and moving parts;

[0039] [Fig.7] [Fig.7] is a perspective view of the mold after manufacture and ejection of the frame;

[0040] [Fig.8] [Fig.8] is a front and sectional view of the mold of [Fig.5], which illustrates the interconnection of the slides;

[0041] [Fig.9] [Fig.9] is a representation of the frame which illustrates the positioning of the injection points;

[0042] [Fig. 10] [Fig. 10] is a perspective view of the frame obtained by the implementation of the mold according to the invention.

[0043] Detailed description of embodiments of the invention

[0044] The mold according to the invention is intended for the manufacture of a bicycle frame or also bike (abbreviation of velocipede), tricycle, quadricycle, or motorcycle. The terms "bicycle" or "bike", "tricycle", "quadricycle", and motorcycle are understood in the broad sense within the scope of the invention, and thus cover two-, three-, or four-wheeled vehicles powered exclusively by the physical force of the user or such electrically assisted vehicles, equipped with a battery, and commonly called electric bicycles.

[0045] In the remainder of this text, for the sake of simplification, the frame will be referred to simply as a bicycle frame, it being understood that the characteristics described also apply to a tricycle, a quadricycle, and a motorcycle.

[0046] One embodiment of the mold is illustrated in Figures 1 to 8. In these figures, the mold is shown in several different configurations depending on the progress of the molding process.

[0047] The mold 1 is composed of two parts, namely a fixed part 2 and a movable part 3. The fixed part 2 is fixed relative to the molding installation during the molding process. The movable part 3 is able to move along an axis (A) substantially perpendicular to the fixed part and to the movable part during the molding process, during the steps of opening and closing the mold.

[0048] According to the conventional direction of use of the mold 1, it has an upper part 4 called above, a lower part 5 called below, as well as a front part 6 called front and a rear part 7 called rear. In this conventional direction, the frame 32 obtained is also in a conventional direction of use, the seat post 37 receiving the saddle being at the top and the chainstays 35 receiving the crankset being at the bottom.

[0049] The fixed and movable parts 2, 3 of the mold together delimit a molding impression 8 of the frame when the mold is closed. This molding impression 8 is intended to receive the polymer material injected hot into the mold. The molding impression is hollowed out in the internal parts 9 of the fixed and movable parts of the mold, as opposed to their external part 10.

[0050] The molding cavity 8 comprises a plurality of cavities 11, 12, 13, 14 in (fluidic) communication with each other. These are hollow regions whose shapes correspond substantially to the profile of the constituent parts of the frame to be manufactured, and are adapted to receive sliders 15, 16, 17, 18 by insertion of the latter. In practice, the dimensions of the cavities are greater than those of the sliders, in order to reserve a space between the external profile of the sliders and the walls of the cavities for the flow of the polymer material throughout the molding cavity.

[0051] It is thus understood that when the polymer material is injected into the mold, it covers the external surfaces (or external profile) of the slides, and conforms to the space 19 located between said external surfaces of the slides and the walls of the cavities, illustrated in [Fig.8]. The shapes of the slides and the cavities are therefore chosen so as to manufacture respective parts of the frame of corresponding shapes.

[0052] The molding impression 8 comprises a first impression 11 which has a profile corresponding to that of a fork pivot 33 of the frame. It opens onto the outside of the mold via an opening 20 located on the underside 5 of the mold, and extends in a substantially rectilinear direction.

[0053] A first slide 15 is intended to be inserted into the first impression 11, from the opening 20 of the bottom of the mold. This first slide 15 has a profile corresponding to the internal part or hollow part of the fork pivot 33 of the frame.

[0054] The molding imprint 8 comprises a second imprint 12 which has a profile corresponding to that of a diagonal tube 34 of the frame. It opens onto the outside of the mold via an opening 21 located on the underside 5 of the mold, and extends in a substantially rectilinear direction and inclined relative to the first imprint 11 at an angle corresponding to it between the fork pivot 33 and the diagonal tube 34 of the frame 32 to be manufactured.

[0055] A second slider 16 is intended to be inserted into the second impression 12, from the opening 21 of the underside of the mold. This second slider 16 has a profile corresponding to the internal part or hollow part of the diagonal tube 34 of the frame.

[0056] The molding impression 8 comprises a third impression 13 which has a profile corresponding to that of the bases 35 and the stays 36 of the frame. It opens onto the outside of the mold via an opening 22 located on the rear 7 of the mold, and extends in a direction substantially perpendicular to the first 11 and to the second impression 12.

[0057] A third slider 17 is intended to be inserted into the third impression 13, from the opening 22 at the rear of the mold. This third slider 17 has a profile corresponding to the internal part or hollow part of the bases 35 and the stays 36 of the frame.

[0058] The molding impression 8 comprises a fourth impression 14 which has a profile corresponding to that of a seat post 37 of the frame. It opens onto the outside of the mold via an opening 23 located on the top 4 of the mold, and extends in a direction substantially parallel to the first impression 11.

[0059] A fourth slider 18 is intended to be inserted into the fourth impression 14, from the opening 23 of the top of the mold. This fourth slider 18 has a profile corresponding to the internal part or hollow part of the seat post 37 of the frame.

[0060] When the various slides 15, 16, 17, 18 are inserted into position in their respective imprints 11, 12, 13, 14, they delimit with the imprints spaces 19 for the flow of the polymer material, which extend over the entire molding imprint. During its flow, the polymer material is overmolded on the slides and conforms on the one hand to the profile of the slides and on the other hand to the profile of the imprints.

[0061] Therefore, the parts of the frame obtained, in particular the fork pivot 33, the diagonal tube 34, the chainstays 35 and seat stays 36, and seat post 37, are hollow. They have an internal surface whose profile corresponds to the profile of the sliders, and an external surface whose profile corresponds to the profile of the prints.

[0062] A main aspect of the invention is that the sliders 15, 16, 17, 18 are interconnected to each other.

[0063] More specifically, at least one of the slides, preferably all of the slides 15, 16, 17, 18 or all of the slides 15, 16, 17, 18 except one, are provided with at least one housing 24, 25, 26, 27 adapted to receive a projecting portion 28, 29, 30, 31 of complementary shape to another slide. The slides are thus assembled by interlocking or embedding, and together form a solid structure capable of resisting injection forces. This solid structure as well as the housings and projecting parts of the slides are shown in more detail in [Fig.8],

[0064] Indeed, during the injection of the hot polymer material, the injection pressure generates significant mechanical forces in the molding cavity 8, and in particular on the slides 15, 16, 17, 18. These forces can lead to a relative movement of the slides with respect to each other, and thus to irregularities in the thickness of the different parts of the frame obtained, or even to the ejection of the slides during a molding operation.

[0065] In [Fig.8], the first slider 15 is provided at its handlebar-side end with a housing 24 (a notch) adapted to receive a projecting portion 28 of the second slider 16. The housing 24 extends substantially in the direction of the second slider 16 and has a shape complementary to that of the projecting portion 28.

[0066] In the embodiment of [Fig.8], the connections between the slides are of the mortise and tenon type. However, the invention is not limited to this specific type of connection, and any mechanical connection ensuring optimal maintenance of the slides relative to each other by mechanical interlocking or nesting while opposing the injection forces may be suitable.

[0067] The second slider 16 is provided at its end on the pedal side with two housings 25, 26 adapted to receive two projecting portions 29, 30 of the third slider 17. The first housing 25 is a notch of small dimensions which extends in the direction of an upper projecting part 29 of the third slider 17, and which has a shape complementary to that of said upper projecting part 29. The second housing 26 is a notch whose bottom is large compared to its edges, which extends in the direction of a lower projecting part 30 of the third slider 17, and which has a shape complementary to that of said lower projecting part 30.

[0068] The third slider 17 is provided at its saddle-side end with a housing 27 adapted to receive a projecting portion 31 of the fourth slider 18. The housing 27 extends substantially in the direction of the fourth slider 18 and has a shape complementary to that of its projecting portion 31.

[0069] The nesting of the slides within each other prevents any movement of the slides during the molding operation.

[0070] This is to cope with flow asymmetries of the polymer material causing asymmetry of the forces on the slide. Furthermore, the rigidity obtained by the interlocking of the slides makes it possible to adapt the flow by modifying the injection sequence so as to place the bonding lines in the most advantageous manner for the mechanical strength of the frame.

[0071] This leads to a homogeneous, reliable and repeatable shape and thickness of polymer material for all parts of the frame. Ejection of the sliders is of course also avoided.

[0072] The mold further comprises a plurality of injection points for injecting the polymer material. The positioning of the injection points is illustrated in [Fig.9], based on a projection of the frame to be obtained to facilitate representation.

[0073] This figure shows eight injection points: - two injection points 38, 39 located on the fork pivot 33, preferably at both ends of the fork pivot 33 - an injection point 40 located on the diagonal tube 34, - an injection point 41 located on the seat post 37, - two injection points 42, 43 located on a front portion of each base 35, i.e. close to the pedal assembly, - two injection points 44, 45 located on a rear portion of each base 35, that is to say at the level of the junction of the bases 35 and the stays 36.

[0074] The homogeneity of the injected polymer material, the direction of the fibers when said polymer material is a composite material, and the densification of the polymer material at the end of injection are three parameters whose optimization makes it possible to further improve the mechanical strength of the frame. The arrangement of the injection points above leads to these advantages, and was determined during the mold development phase, via rheology simulations and developed following injection tests.

[0075] The number of injection points and their respective section is thus the result of precise adjustment. This number is at least three up to one point per element of the frame, i.e. approximately nine injection points.

[0076] A method of manufacturing a bicycle frame by injecting a polymer material into a mold will now be described.

[0077] This method uses the mold as described above, and thus leads to the same advantages of homogeneity, reliability and repeatability of the thicknesses and shapes of the parts of the frame.

[0078] We begin by providing a polymer material intended to be injected into the mold 1. This polymer material is preferably a composite material which comprises a polymer matrix and a fibrous reinforcement. As is known, the reinforcement is the frame which takes up most of the mechanical forces, and the matrix allows the mechanical forces to be transmitted to the reinforcement.

[0079] The fibrous reinforcement has a content of between 30% and 60% by weight relative to the total weight of the composite material.

[0080] Preferably, the fibers of the fibrous reinforcement have a length less than or equal to 20 millimeters (mm).

[0081] The composite material is preferably of plant or recycled nature.

[0082] The polymer constituting the polymer matrix is ​​preferentially chosen from: polyacrylamide 6 (PA6), polyacrylamide 12 (PA 12), polyacrylamide 6 / 66 (PA6 / 66), polyacrylamide 610 (P610), polyacrylamide 66 (PA66), polyacrylamide 66 / 6 (PA6 / 66), polyaryletherketone (PAEK), preferably polyetheretherketones (PEEK) and polyetherketoneketones (PEKK), polybutylene terephthalate (PBT), poly-ethyleneimine (PEI), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polycarbonate (PC), polymethylpentene (PMP), polyoxymethylene (POM), polyphenylether (PPE), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF).

[0083] The fibers constituting the reinforcement are preferably chosen from: carbon, linen, hemp, jute, basalt, aramid acrylic, fiberglass, iron, coconut, aluminum, titanium, tungsten, copper, magnesium, sisal.

[0084] The fixed 2 and mobile 3 parts of the mold 1 as well as the slides 15, 16, 17, 18 are placed in the open position, as shown in [Fig.l].

[0085] The slides 15, 16, 17, 18 are then inserted into their respective imprint. According to the structure of the slides of the mold of Figures 1 to 6, and in particular the positioning of their housings, the first slide 15 is first closed ([Fig.2]), then the second slide 16 ([Fig.3]), the third slide 17 ([Fig.4]), and finally the fourth slide 18 ([Fig.5]), ensuring that their projecting portion is correctly housed in the corresponding housing of the neighboring slide.

[0086] The mold 1 is then closed by bringing the movable part 3 closer to the fixed part 2 until they are in contact with each other. The mold 1 thus closed is illustrated in [Fig.6].

[0087] The polymer material is then hot injected into the molding cavity of the mold. The polymer material circulates throughout the molding cavity, overmolding the slides, thus forming the frame 32. This operation is also called filling.

[0088] The polymer material is preferably injected at a temperature between 200°C and 300°C, more preferably between 240°C and 280°C.

[0089] The injection time is preferably between 5 seconds and 10 seconds.

[0090] The injection speed is preferably constant during the injection.

[0091] The mold is preferably preheated before injecting the polymer material, to a temperature between 50°C and 100°C, more preferably between 70°C and 90°C.

[0092] The injection of the polymer material is carried out via the injection points. Preferably, the injection points are used one after the other in a defined order, so that the injection is said to be sequential.

[0093] With reference to [Fig.9] described previously in relation to the mold, the injection begins at t = 0 by the two injection points 38, 39 located at the two ends of the fork pivot 33.

[0094] After a few seconds, for example about 3 seconds, the injection begins via the injection point located on the diagonal tube 34, while continuing the injection via the two injection points 38, 39 of the fork pivot 33.

[0095] A few seconds later, for example 2 seconds later (i.e. a general injection time of approximately 5 seconds), the injection is then started via the two injection points 42, 43 located on the bases 35, while continuing the injection via the two injection points 38, 39 of the fork pivot 33 and via the injection point located on the diagonal tube 34.

[0096] The injection then begins via the injection point located on the seat post 37, typically after approximately 1 second (i.e. a general injection time of approximately 6 seconds), while continuing the injection via the two injection points 38, 39 of the fork pivot 33, via the injection point located on the diagonal tube 34, and via the two injection points 42, 43 located on the chainstays 35.

[0097] Finally, the injection is started by the two injection points 44, 45 located at the junction of the chainstays 35 and the seatstays 36, typically after about half a second (i.e. a general injection time of about 6.5 seconds), while continuing the injection by the two injection points 38, 39 of the fork pivot 33, by the injection point located on the diagonal tube 34, by the two injection points 42, 43 located on the chainstays 35, and by the injection point located on the seat post 37.

[0098] In the dynamic filling phase, the pressure in the molding cavity, from 0 to 500 bars, is adjusted by the injection press with the objective of respecting a substantially constant injection speed setpoint (constant flow rate of polymer material). This makes it possible to obtain good crystallization, which is directly linked to the mechanical properties of the frame obtained.

[0099] The pressure in the screw increases gradually, between the start of injection and the end of the so-called dynamic phase. In the filling phase (dynamic), the pressure in the screw can rise to 1000 bars. The pressure losses are due to the pressure losses in the hot bar and then to the pressure losses of filling the part, so that the pressure in the molding cavity increases gradually from 1 bar to 500 bars depending on where you are in the footprint.

[0100] After filling, a compacting step is carried out consisting of injecting a small volume of polymer material to compensate for shrinkage, deformation, shrinkage and other local losses of volume of the frame. This step makes it possible to optimize the quality of the frame.

[0101] During the compaction phase, the pressure in the molding cavity is of the order of 500 bars, and is applied everywhere in said cavity since there is no pressure loss. Indeed, we are in a static phase, so that the polymer material is substantially immobile, and therefore no longer rubs against the walls of the cavity.

[0102] The injection at each injection point is continued for 20 seconds to 40 seconds, preferably for 30 seconds to 35 seconds. There is therefore a superposition of the injection phases at the different injection points, each injection phase being offset in time relative to the previous one, typically by a few tenths of a second to a few seconds.

[0103] The material is then cooled, then after cooling, the mold 1 is opened by moving the movable part 3 away from the fixed part 2, and the slides 15, 16, 17, 18 are also opened in order to release the frame 32.

[0104] Finally, the frame 32 is ejected from the mold, manually or automatically, as illustrated in [Fig.7].

[0105] Optionally, the method further comprises a step of external ribbing of the bases 35 of the frame 32, and / or a step of internal ribbing of the stays 36 of the frame 32.

[0106] The ribbing step is explained by the fact that the rear part of the frame, including the bases 35 and the stays 36, is obtained by machining grooves in the mold coaxial with the movement of the drawers, which means there is no undercut in the axis of said movement. The presence of external ribs on the bases and the stays thus makes it possible to stiffen them.

[0107] [Fig. 10] illustrates in detail the frame obtained. The frame 32 comprises a fork pivot 33 intended to receive the fork of a bicycle receiving the front wheel, a diagonal tube 34, chainstays 35 and seat stays 36 forming the rear part of the frame intended to receive an axle carrying the rear wheel, and a seat post 37 intended to receive a saddle.

Claims

Claims

1. Mold (1) for manufacturing a one-piece bicycle, tricycle, quadricycle, or motorcycle frame (32) by injection of a polymer material, the mold (1) comprising a fixed part (2) and a movable part (3) capable of moving towards or away from the fixed part to close or open the mold respectively, which together delimit a molding imprint (8) of the frame when the mold is closed, the mold (1) being characterized in that: - it comprises at least three sliders (15, 16, 17, 18), capable of being inserted into respective cavities (11, 12, 13, 14) of the molding cavity (8) whose positioning within said molding cavity and profile correspond to parts of the frame to be manufactured, said sliders (15, 16, 17, 18) being intended to be overmolded with polymer material during a molding operation so as to form said parts of the frame (32), - at least two of these slides (15, 16, 17, 18) are in engagement with each other when they are in position in their respective imprint, thus forming a solid structure capable of resisting injection forces, and - it includes at least three of the following corresponding prints and slides, a first imprint (11) having a fork pivot profile (33) of the frame, and a first slider (15) adapted to be inserted into the first imprint (11), a second indentation (12) which communicates with the first indentation (11), having a profile of a diagonal tube (34) of the frame, and a second slider (16) adapted to be inserted into the second indentation (12), a third indentation (13) which communicates with the second indentation (12), having a profile of bases (35) and seat stays (36), and a third slider (17) adapted to be inserted into the third indentation (13), a fourth indentation (14) which communicates with the third indentation (13), having a profile of a seat post (37), and a fourth slider (18) adapted to be inserted into the fourth indentation (14).

2. A mold (1) according to claim 1, wherein at least two of the co- slides (15, 16, 17, 18) are provided with at least one housing (24, 25, 26, 27) adapted to receive a projecting portion (28, 29, 30, 31) of complementary shape to a neighboring slide, so that when the slides (15, 16, 17, 18) are in position in their respective imprint, said slides are fitted into each other.

3. Mold (1) according to claim 1 or 2, wherein at least two of the following slides are provided with at least one housing such that: - the first slide (15) is provided with at least one housing (24) adapted to receive a projecting portion (28) of the second slide (16), - the second slide (16) is provided with at least one housing (25, 26) adapted to receive a projecting portion (29, 30) of the third slide (17), - the third slide (17) is provided with at least one housing (27) adapted to receive a projecting portion (31) of the fourth slide (18).

4. Mold (1) according to one of claims 1 to 3, wherein, considering that the molding impression (8) is positioned in a conventional direction of use of a bicycle, a tricycle, a quadricycle, or a motorcycle: - the first slider (15) is inserted from below (5) of the mold, in a direction of the fork pivot (33), - the second slider (16) is inserted from below (5) of the mold, in a direction of the down tube (34), and fits into the first slider (15), - the third slider (17) is inserted from the rear (7) of the mold, and fits into the second slider (16), - the fourth slider (18) is inserted from above (4) of the mold, in a direction of the seat post (37), and fits into the third slider (17).

5. Mold (1) according to any one of the preceding claims, comprising at least one of the following injection points: - at least one injection point (38, 39) located on the fork pivot (33), preferably at least two injection points preferably located at the two ends of the fork pivot (33), - at least one injection point (40) located on the down tube (34), - at least one injection point (41) located on the seat post (37), - at least two injection points (42, 43) located on a front portion of each base (35), - at least two injection points (44, 45) located on a rear portion of each base (35).

6. A method of manufacturing a one-piece bicycle, tricycle, quadricycle, or motorcycle frame (32) by injecting a polymer material into a mold (1), characterized in that it comprises the following steps: - providing a mold (1) according to any one of claims 1 to 5, - closing the slides (15, 16, 17, 18) in order to engage them with each other, preferably to fit them into each other, and closing the mold (1) by moving the movable part (3) towards the fixed part (2) until they come into contact so as to delimit the molding impression (8), - hot injection of a polymer material into the molding impression (8), by overmolding the slides (15, 16, 17, 18) in position in their respective impression (11, 12, 13, 14), to form the frame (32), - opening of the slides (15, 16, 17, 18),and opening of the mold (1) by separating the fixed (2) and mobile (3) parts to release the frame (32), - ejection of the frame.,

7. A method according to claim 6, further comprising a step of externally ribbing the bases (35) of the frame (32).

8. A method according to claim 6 or claim 7, further comprising a step of internally ribbing the stays (36) of the frame (32).

9. Method according to any one of claims 6 to 8, in which the polymer material is injected into the molding impression by injection points, the injection being carried out from the front (6) of the frame (32), that is to say an injection point opening onto an impression (11) of the fork pivot (33) or an impression (12) of the down tube (34), towards the rear (7) of the frame (32), that is to say an injection point opening onto an impression (13) of the chainstays (35) and the seat stays (36) or an impression (14) of the seat post (37).

10. A method according to any one of claims 6 to 9, wherein the polymer material is a composite material comprising a polymer matrix and a fibrous reinforcement, said fibrous reinforcement having a content of between 30% and 60% by weight relative to the total weight of the composite material.

11. Method according to claim 10, in which the polymer constituting the polymer matrix is ​​chosen from: polyacrylamide 6, polyacrylamide 12, polyacrylamide 6 / 66, polyacrylamide 610, polyacrylamide 66, polyacrylamide 66 / 6, polyaryletherketone, preferably polyetheretherketones and polyetherketoneketones, polybutylene terephthalate, polyethyleneimine, polyethylene terephthalate, glycolized polyethylene terephthalate, polycarbonate, polymethylpentene, polyoxymethylene, polyphenylether, polytetrafluoroethylene, polyvinylidene fluoride.

12. A method according to claim 10 or claim 11, wherein the fibers constituting the reinforcement are chosen from: carbon, linen, hemp, jute, basalt, aramid acrylic, fiberglass, iron, coconut, aluminum, titanium, tungsten, copper, magnesium, sisal.

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