Patent Application
20240190062
The present invention relates to a mold for manufacturing by extrusion blow-molding a hollow tank body made of plastic material for a motor vehicle from a parison, the tank comprising at least one internal component fixed inside the parison during the molding of the hollow body. More particularly, the invention relates to a mold comprising two parts comprising a plurality of sections internally defining a mold cavity comprising a total molding surface intended to reproduce a predetermined shape of the hollow body to be manufactured.
The invention also relates to a machine for molding by extrusion blow-molding a hollow tank body made of plastic material for a motor vehicle from a parison.
The invention finally relates to a method for molding by extrusion blow-molding a hollow tank body made of plastic material for a motor vehicle from a parison, the tank comprising at least one internal component fixed inside the parison during the molding of the hollow body.
In document WO 2008/138869, the Applicant describes a mold for manufacturing a fuel tank provided with an internal component or a set of internal components. The mold cavities comprise a plurality of movable rods, a contact surface is provided at the free end of each movable rod to locally push the parison in the molten state and bring it into contact with a region of an internal component to form, by pressing, a fixing of the internal component inside the parison. Another example is described in document US 2014/265052.
Since the contact surface of a movable rod is limited by its cross-section, the more regions to be fixed the internal component has, the more movable rods must be provided. The free end of a movable rod typically has a contact surface of about 4000 mm2, which represents less than 2% of the total surface area of the mold. With six movable rods, it is less than 12% of the total surface area of the mold. Likewise, the more internal components are contained in the set of internal components, the more movable rods must be provided. This is not satisfactory because the design of the mold becomes more complex and more expensive to manufacture.
Furthermore, the Applicant has observed that in the location where the parison is pushed by a movable rod toward a region of an internal component, the material of the parison is stretched toward this fixing region so that the parison has a reduced thickness at the fixing. This is not desirable because a reduction in the thickness of the material at the location of the fixing can cause a lack of fixing of the internal component. Furthermore, the reduction in thickness observed at the fixing is often accompanied by another deformation. This other deformation is a rippling of the material around the fixing. This is not desirable since the more deformations the reservoir undergoes during its manufacture, the worse the mechanical resistance of the resulting reservoir will be. The aforementioned risks are obviously aggravated by the proliferation of the movable rods.
The Applicant has also observed that the proliferation of the movable rods leads to a degradation of the cooling temperature of the mold because the movable rods do not form part of the cooling circuit of the mold. This is not satisfactory because a degradation of the cooling temperature homogeneity of the mold is likely to cause deformations of the tank during its manufacture.
Another disadvantage of the above-mentioned mold is that the proliferation of the movable rods leads to the proliferation of the movement mechanisms of the movable rods, which leads to increases the size and complexity of the extrusion blow-molding machine equipped with such a mold.
It is thus understood the cost of manufacturing a tank provided with one (or more) internal component(s) increases with the number of movable rods necessary to fix the internal component(s).
The object of the invention is in particular to remedy the aforementioned disadvantages by providing a mold guaranteeing manufacturing without deformation and at a lower cost of a tank comprising one (or more) internal component(s), independently of the number of attachments of the internal component(s) inside the parison.
To this end, the invention relates to a mold for manufacturing by extrusion blow-molding a hollow tank body made of plastic material for a motor vehicle from a parison, the tank comprising at least one internal component fixed to the interior of the parison during the molding of the hollow body, the mold comprising two parts movable relative to one another delimiting internally, when they are closed against each other, a total molding surface intended to reproduce a predetermined shape of the hollow body to be manufactured, at least one of the parts of the mold comprising:
Advantageously according to the invention, the mold makes it possible to fix one or more internal components without resorting to a plurality of movable rods, those being replaced by a mold section having a molding surface that is sufficiently extended to be able to press the parison against a plurality of regions for fixing the internal component(s) at the same time.
In addition to the savings in terms of cost, the invention makes it possible to avoid locally deforming the material of the parison during the contacting thereof with a region to be fixed due to the fact that the first molding surface extends between, that is to say in particular comprises, various regions for fixing the internal component(s) with the inside of the parison. By virtue of this arrangement, the thickness of the material at the location of each fixing region is not reduced and the rippling of the material around this fixing region is avoided.
Another advantage of the mold according to the invention is that it makes it possible to avoid increasing the size and complexity of the blow-molding machine equipped with such a mold, regardless of the number of fixing regions and the number of internal components of the future tank.
The invention may also comprise one or more of the following optional features, taken alone or in combination.
The first molding surface of the mold part may be configured to extend along a circumscribed surface containing the contact regions associated with the mold part. Thus, each part comprising a first molding surface has a single surface toward the parison in the intermediate closing position in order to fix the parison, thanks to the various distinct contact regions of the first molding surface, according to a plurality of predetermined fixing regions or all the regions for fixing said at least one internal component of the part of the mold at the same time.
The circumscribed surface of the first molding surface of the part of the mold may comprise a predetermined margin distance at least around the contact regions of said at least one internal component associated with the part of the mold in order to limit the ripples of the material around each fixing region. It is thus understood that the first molding surface comprises a single surface more extended around the regions for fixing said at least one internal component in order to avoid an excessive relief difference near the regions for fixing said at least one internal component inside the parison. The predetermined margin distance at least around the contact regions may be between 1 mm and 60 mm.
The circumscribed surface of the first molding surface of the part of the mold is preferentially at least equal to 30% of the total molding surface. It is apparent that, according to the embodiment, that is to say if only one part of the mold or the two parts of the mold comprises at least one first section, the total percentage of the at least one first mold section is respectively at least equal to 30% or at least equal to 60% of the total molding surface. However, the circumscribed surface of the first molding surface of the mold part may be between 20% and 40% of the total molding surface without departing from the scope of the invention, that is, for example equal to 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%.
Thus, according to a first embodiment, each part of the mold may comprise at least one first section and a second section and, according to a second embodiment, only one of the parts of the mold comprises at least one first section and a second section. Typically, in the second embodiment, the first part of the mold may comprise at least one first section and a second section and, the second part of the mold may comprise a single section made of one piece.
In the final closing position, the at least one first mold section of each part of the mold is preferentially surrounded by its associated second section of the part of the mold. Thus, said at least one internal component is entirely enclosed in the hollow body.
In the first embodiment, the at least one first mold section of each part of the mold may comprise at least one support region configured to press the parison against said same at least one internal component in order to form at least two different regions for fixing said same at least one internal component for fixing said same at least one internal component inside the parison during the molding of the hollow body. It is understood that at least one contact region of the at least one first section of the first part of the mold can thus be aligned, that is to say plumb with, at least part of a contact region of the at least one first section of the second part of the mold in order to fix two substantially opposite regions of the internal component at the same time in two distinct regions of the interior of the parison. Thus, the first mold sections act as a vice which clamps said at least one internal component.
Regardless of the embodiment, the at least one first section of the part of the mold may comprise, as in particular in one of the contact regions, at least one suction element intended to suction the parison during the molding of the hollow body. Thus, the parison is better pressed on the first molding surface, which also avoids the local deformation of the parison.
The at least one first section of the mold part may comprise an element selected from a gripping element, a heating element and a combined gripping and heating element for gripping and/or heating a workpiece, which may or may not be said at least one internal component, intended to be molded with the first portion of the hollow body. Thus, it is possible to connect a workpiece to the first portion of the hollow body during its molding. In one example, the gripping element is a gripper or a suction element and the heating element is an electric heater. In one example, the workpiece is a metal fastener or fibrous reinforcement. In another example, the heating element is a hydraulic heater.
The at least one first section of the part of the mold may comprise a blowing tool intended to introduce a pressurized gas inside the parison. In one example, the blowing tool is a blowing needle. Insofar as a blowing tool is necessary, this arrangement makes it possible to avoid placing a blowing tool in the second mold section, which would have the consequence of degrading the evaporative and mechanical performance of the resulting tank, as well as increasing the risks of deformation experienced by the tank during its manufacture.
The at least one first section of the part of the mold may comprise a first cooling device intended to cool the first portion of the hollow body. This makes it possible to avoid any deformation of the first portion of the hollow body during its manufacture.
The second section of the part of the mold may comprise a second cooling device intended to cool the second portion of the hollow body. This makes it possible to avoid any deformation of the second portion of the hollow body during its manufacture.
Advantageously, the first cooling device and the second cooling device are part of the same cooling circuit. This makes it possible to homogenize the temperature of the mold.
The at least one first section of the part of the mold may comprise a plurality of first sections in order to increase the modularity of the mold.
The invention also relates to a machine for molding by extrusion blow-molding a hollow tank body made of plastic material for a motor vehicle from a parison, characterized in that the machine comprises a mold as presented above. Thus, the molding machine benefits from all the advantages associated with the mold.
The invention finally relates to a method for molding by extrusion blow-molding a hollow tank body made of plastic material for a motor vehicle from a parison, the tank comprising at least one internal component fixed inside the parison during the molding of the hollow body, characterized in that the method comprises the following steps:
The molding method according to the invention preferably uses an extruded parison. According to the invention, each internal component is surrounded by the parison, either by extruding the parison around each internal component, or by inserting each internal component into the parison. In the case where the internal component is inserted into the parison, the parison can be brought into the open mold by means of a robot.
The extruded parison can be stretched to allow insertion of the internal component without risk of collision with the parison; this may be done by an appropriate device. In one example, the molding method according to the invention uses a tool to stretch the parison to hold it open, such as, for example, of the type referenced 6 in document WO 2008/138869. This tool may consist of clamps, jaws or pincers capable of gripping the edges of the parison and of holding them apart. This tool can be controlled by a robot.
The invention may also comprise one or more of the following optional features, taken alone or in combination.
Preferably, a pressurized gas is introduced inside the parison to pre-blow said parison between step a) and step b). Such an introduction of gas can be carried out according to step b of document WO 2008/138869 in order in particular to expand the parison by homogenizing the thickness of the parison. The introduction of gas at lower pressure than for step d) can be obtained in different ways known by a person skilled in the art. As a non-limiting example, the introduction of gas for the pre-blowing can be obtained by the blowing tool used to perform step d), by a dedicated tool mounted on the mold, by a hollow shaft for internal component support or by a nozzle comprised in the parison extrusion head.
In step b), said at least one internal component can be fixed inside the parison by welding, heading or mechanical anchoring.
Other features and advantages of the invention will become apparent from the description given below, by way of indication and in no way limiting, with reference to the accompanying drawings, wherein:
In the various figures, identical or similar elements bear the same references, optionally with an index added. The description of their structure and their function is therefore not always repeated.
In the following, the orientations are the orientations of the figures. In particular, the terms “upper”, “lower”, “left”, “right”, “above”, “below”, “forward” and “backward” are generally understood relative to the direction of representation of the figures.
“Tank” is understood to mean a sealed tank able to store a fluid under diverse and varied conditions of use and environments. The tank manufactured with the mold according to the invention is made with a wall formed of plastic material. A tank wall has an inner surface and an outer surface. The inner surface is the surface facing the space inside the tank while the outer surface is the surface facing the space outside the tank.
The term “plastic material” or “plastic” means any material comprising at least one polymer made of synthetic resin. All types of plastics may be suitable. Plastics that are well-suited to the category of thermoplastic materials.
“Thermoplastic material” refers to any thermoplastic polymer, including thermoplastic elastomers, as well as mixtures thereof. The term “polymer” refers to both homopolymers and copolymers (in particular binary or ternary). Examples of such copolymers are, in a non-limiting manner: random copolymers, block copolymers, block copolymers and grafted copolymers.
Any type of thermoplastic polymer or copolymer whose melting point is lower than the decomposition temperature is suitable. Synthetic thermoplastic materials which have a melting range spread over at least 10 degrees Celsius (10° C.) are particularly suitable. Examples of such materials are those which exhibit a polydispersion of their molecular mass.
In particular, it is possible to use polyolefins, thermoplastic polyesters, polyketones, polyamides and copolymers thereof. A mixture of polymers or copolymers may also be used, as well as a mixture of polymeric materials with inorganic, organic and/or natural fillers such as, for example, but not limited to: carbon, salts and other inorganic derivatives, natural or polymeric fibers. It is also possible to use multilayer structures consisting of stacked and integral layers comprising at least one of the aforementioned polymers or copolymers.
A polymer often employed is polyethylene. Excellent results were obtained with high-density polyethylene (HDPE).
In one example, the tank manufactured with the mold according to the invention is a fuel tank that comprises a multilayer structure comprising at least one layer of thermoplastic material and at least one additional layer which can advantageously consist of a liquid and/or gas barrier material. Preferably, the nature and the thickness of the barrier layer are chosen so as to limit as much as possible the permeability of the liquids and of the gases in contact with the wall of the tank. Preferably, this layer is based on a barrier material, that is to say a resin impermeable to a fuel such as EVOH, for example (ethylene copolymer—partially hydrolyzed vinyl acetate). Alternatively, the tank may be subjected to a surface treatment (fluorination or sulfonation), the purpose of which is to make it impermeable to the fuel.
“Parison” is understood to mean a single-piece preform, generally extruded and of a substantially tubular shape, which is intended to constitute the wall of the tank after molding, that is after an operation which consists in placing the parison, which is in the molten state, with the required shapes and dimensions using the mold to obtain a tank.
“Internal component” is understood to mean a component having a function to be fulfilled in the tank such as ventilating, reinforcing, pumping fluid, measuring the level of the fluid, decreasing the noise related to the waves of fluid in the tank. In one example, the internal component is a reinforcement pillar that connects two opposite sides of the inner surface of the tank.
“First section” and “second section” of the mold are understood to mean respectively a first and a second molding element located in at least one of the parts of the mold.
“First molding surface” means the inner surface of the at least one first mold section delimiting the molding space of the first portion of the hollow body. This inner surface comprises a bottom and portions protruding from the bottom.
“Second molding surface” means the inner surface of the at least one second mold section delimiting the molding space of the second portion of the hollow body. This inner surface comprises a bottom and portions protruding from the bottom.
“The first molding surface is at least equal to 30% of the total molding surface” means that the area of the first molding surface is greater than or equal to 30% of the area of the total molding surface while being strictly less than 100% of the area of the total molding surface.
Advantageously, the sum of the molding surfaces of the two parts of the molding is equal to the total molding surface. Thus, the two parts of the mold are sufficient to manufacture the hollow tank body in its entirety.
“Plastic welding” means a set of techniques used to weld two thermoplastic parts. By way of example, plastic welding may consist, insofar as the materials of the internal component and of the parison are compatible with the welding, of applying, by pressing each contact region of the at least one first mold section, a contact pressure at the interface between the interior of the parison, which is in the molten state, and a region to be fixed of said at least one internal component. To facilitate the plastic welding, the region to be fixed of said at least one internal component is preferably previously heated to be softened and melted.
“Heading” means a set of techniques used to fix an internal component to the parison, in particular in the case where the materials of the internal component and the parison are not compatible with the welding, by pressing each contact region of the at least one first mold section, in order to induce a portion of the parison to enter a recess of the internal component by creeping therein. After the hardening of the parison, the heading prevents the component from coming out of the hardened parison, thanks to the shape of the recess. Examples of a hardened parison form and a component recess are respectively referenced 5 and 3 in FIGS. 1 and 2 of document WO 2007/090453.
“Mechanical anchoring” means a set of techniques used to fix an internal component to the parison, in particular in the case where the materials of the internal component and the parison are not compatible with the welding, by pressing each contact region of the at least one first mold section, in order to induce a part of the internal component to enter the parison by creeping therein. After the hardening of the parison, the mechanical anchoring prevents the internal component from coming out of the hardened parison, thanks to the shape of the internal component that entered the parison. Examples of a hardened parison form and an internal component entry part are respectively referenced 116 and 102 in FIG. 10 of document EP 1 211 196.
The extrusion-blow members known to the person skilled in the art are usually reproduced barring some exceptions indicated in the present description. Common members such as the supports for internal components (for example rods), the blowing means, the means for manufacturing the parison, the means for separating and guiding the parison around the internal components or the means for sealing the parison in order to perform pre-blowing, such as those explained for example in the document WO 2008/138869 (see in particular references 3, 6, 7 and 7′) are therefore not always described in the present description.
The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments can also be combined and/or interchanged to provide other embodiments.
In the present description, it is possible to index certain elements or parameters, for example first element or second element as well as first parameter and second parameter or first criterion and second criterion, etc. In this case, it is a simple indexing for differentiating and naming similar but non-identical elements or parameters or criteria. This indexing does not mean that one element, parameter or criterion has priority relative to another, and such designations can easily be changed without departing from the scope of the present description. This indexing does not imply a temporal order, for example, for assessing such a criterion.
The mold 1 comprises two parts 1a and 1b that can be moved relative to each other, internally delimiting, when they are closed against each other (as visible in
According to the invention, at least one of the parts 1a, 1b of the mold 1 comprises:
The second section 4, 4a, 4b of the part 1a, 1b of the mold 1 is movable relative to its at least one first section 3, 3a, 3b associated with the part 1a, 1b of the mold 1 between at least one intermediate closing position of the parts 1a, 1b of the mold 1 (shown in
Advantageously according to the invention, the first molding surface 11, 11a, 11b of the part 1a, 1b of the mold 1 comprises a plurality of support regions 5 as shown in
As shown in
Thus, each part 1a, 1b comprising a first molding surface 11, 11a, 11b has a single surface toward the parison 20 in the intermediate closing position (shown in
The circumscribed surface Sc of the first molding surface 11, 11a, 11b of the part of the mold may comprise a predetermined margin distance at least around the contact regions 5 of said at least one internal component 30 associated with the part of the mold 1 in order to limit the ripples of material around each fixing region. The predetermined margin distance at least around the contact regions 5 may be between 1 mm and 60 mm. Of course, the predetermined margin distance is not necessarily constant relative to each support region 5 or between each contact region.
The circumscribed surface of the first molding surface 11, 11a, 11b of the part 1a, 1b of the mold 1 is preferentially at least equal to 30% of the total molding surface. It is apparent that, according to the embodiment, that is to say if only one part 1a, 1b of the mold 1 or both parts 1a, 1b of the mold 1 comprises at least one first section 3, 3a, 3b, the total percentage of the at least one first mold 1 section 3, 3a, 3b is respectively at least equal to 30% or at least equal to 60% of the total molding surface. However, the circumscribed surface Sc of the first molding surface 11, 11a, 11b of the mold part 1a, 1b may be between 20% and 40% of the total molding surface without departing from the scope of the invention, that is, for example equal to 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%.
In the intermediate closing position, the at least one first section 3, 3a, 3b of mold 1 protrudes from the second mold section 4, 4a, 4b of mold 1. In the final closing position, the second mold section 4, 4a, 4b of mold 1 surrounds the at least one first section 3, 3a, 3b of mold 1 which has not changed position, so that the first 11, 11a, 11b and second 12, 12a, 12b molding surfaces join together to form the total molding surface, or cavity 2.
The at least one first section 3, 3a, 3b of mold 1 comprises contact regions 5 configured to press the parison 20 against said at least one internal component 30 in order to form at least two different regions for fixing said same at least one internal component 30 in order to fix said same at least one internal component 30 inside the parison 20 during the molding of the hollow body 10.
Advantageously, each support region 5 is configured to allow the welding, the heading or the mechanical anchoring to fix said at least one internal component 30 inside the parison 20 during the molding of the hollow body 10. Each support region can thus comprise a geometry, mechanical characteristics and/or a material intended to facilitate welding, heading or mechanical anchoring. By way of non-limiting example, the support region 5 may comprise a flat surface, the material of which has a melting point greater than that of the parison and the region to be fixed of the internal component so that, by pressing the contact region, at least one welding fixing region is formed between the parison and the region to be fixed of the internal component. Of course, in addition or in substitution, the support region may also comprise a protrusion intended to promote a crimping and/or a recess intended to promote mechanical anchoring.
The first mold 1a part 1 comprises at least one first section 3a of mold 1 and, the second mold part 1b of mold 1 comprises at least another first section 3b of mold 1. The at least one first section 3a of mold 1 is movable relative to the at least one other first section 3b of mold 1 between the open position and the intermediate closed position of the mold 1. The at least one first section 3a, 3b of each mold 1 part 1a, 1b comprises a first actuator 6 for going from the open position to the intermediate closing position and vice versa.
The first mold 1 part 1a comprises at least one second section 4a of mold 1 and, the second mold 1 part 1b comprises at least another first mold 1 section 4b. The second mold sections 4a, 4b of mold 1 are movable relative to each other between the intermediate closure position and the final closed position of the mold 1. Each second mold section 4a, 4b of mold 1 comprises a second actuator 7 for going from the intermediate closed position to the final closed position and vice versa.
In the example shown in
In the examples shown in
In the example shown in
In the example shown in
Preferably, a pressurized gas is introduced inside the parison 20 to pre-blow said parison 20 between step a) and step b). Such an introduction of gas can be carried out according to step b) of document WO 2008/138869 in order in particular to expand the parison by homogenizing the thickness of the parison. The introduction of gas at lower pressure than for step d) can be obtained in different ways known by the person skilled in the art. As a non-limiting example, the introduction of gas for the pre-blowing can be obtained by the blowing tool used to perform step d), by a dedicated tool mounted on the mold, by a hollow shaft for internal component support or by a nozzle comprised in the parison extrusion head.
Advantageously, in step b), said at least one internal component 30 can be fixed inside the parison 20 by welding, heading or mechanical anchoring.
In the final closed position of the mold 1, the blowing of step d) is carried out under a blowing pressure of the order of 10 bar (1 MPa). In order for the blowing pressure not to be exerted on the actuator 6 via the at least one first mold section 3, a force recovery is carried out on a support plate 9 rigidly connected to the molding machine 100.
The invention is not limited to the embodiments and variants presented, and other embodiments and variants will become clearly apparent to the person skilled in the art. Thus, the above embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments can also be combined and/or interchanged to provide other embodiments. In a non-limiting manner, in the second embodiment, only one actuator 7 is used to move the second section 4a toward the single-piece section 8 (which would therefore be static) in order to further simplify the molding machine 100. Likewise, although the figures show the presence of a single first section 3a, 3b of the part 1a, 1b of the mold 1, it can be envisaged that the at least one first section 3a, 3b of mold 1 comprises a plurality of first sections 3a, 3b, for example two, three, four, five, six, seven, eight, nine or ten first sections 3a, 3b.
| Number | Date | Country | Kind |
|---|---|---|---|
| LU102744 | Apr 2021 | LU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/058950 | 4/5/2022 | WO |
