A machine for continuously producing moulded products

Abstract

The invention is directed to a machine for continuously producing moulded products. The machine has a production direction and comprises: (i) a forming station to form a shaped plastic film mould by thermoforming. (ii) a filling station suited to add a liquid curable composition to the shaped plastic film mould from above. (iii) a pressing station comprising of a pressing tool and an endless belt such that the endless belt covers the filled plastic film mould and moves together with the filled plastic film mould in the production direction to obtain in use a cured or semi-cured filled plastic film mould.

Description

[0001] A MACHINE FOR CONTINUOUSLY PRODUCING MOULDED PRODUCTS

[0002] The invention is directed to a machine for continuously producing moulded products having a planar surface and a shaped recess wherein the machine has a production direction. In the production direction a forming station and a filling station is present. The invention is also directed to a process to continuously produce a moulded product having a planar surface and a shaped recess.

[0003] Such a machine and process is described in US2022 / 0132989. In this publication a process is described wherein in a first step a shaped plastic film mould is made by thermoforming from a planar plastic film using a shaped master mould. In a next step a curable cold pour industrial liquid rubber is added to the shaped plastic mould. A second form negative mould is placed on top of the filled shaped plastic mould. The resulting package is pressed from both sides for 15 minutes. After 12 hours the fully cured moulded product is removed from the plastic moulds. The process up to at least the filling of the mould may be performed making use of an adapted thermoforming packaging machine. An advantage of this process is, according to this publication, that the long curing period takes place while the moulded product is present in the described disposable plastic moulds. This in contrast with known industrial processes where the moulded product, such as foot wear outsoles, cures in complex metal moulds made by substrative machining.

[0004] A disadvantage of the process of US2022 / 0132989 is that it requires that the package is pressed from both sides for 15 minutes. When moulded products are to be made in high numbers this pressing step complicates the process.

[0005] The object of the present process is to provide a more simple process and machine which achieves many of the advantages of the process and machine described in US2022 / 0132989 but which does not require the state of the art pressing step.

[0006] This object is achieved by the following machine. A machine for continuously producing moulded products having a planar surface and a shaped recess wherein the machine has a production direction and wherein in the production direction the following stations are comprised: a forming station with a shaped master mould suited to form a shaped plastic film mould from a planar plastic film by thermoforming and wherein the shaped plastic film mould has a downwardly extending shaped recess, a filling station suited to add a liquid curable composition to the shaped recess of the shaped plastic film mould from above such to obtain in use a filled plastic film mould, and a pressing station comprising of a pressing tool and an endless belt guided by two or more belt rollers which belt rollers are positioned perpendicular to the production direction such that the endless belt covers the filled plastic film mould and moves together with the filled plastic film mould in the production direction to obtain in use a cured or semi-cured filled plastic film mould.

[0007] Applicants found that with this machine it is not necessary to position a second form negative mould on top of the filled shaped plastic mould. The endless belt now covers and presses the filled shaped plastic mould for a certain time when it moves in the production direction. By pressing the contents of the filled plastic moulds from above by the moving belt and the pressing tool and curing for a certain time in the pressing station it is possible to create at least a film of cured material at the surface facing the endless belt. This film allows the endless belt to separate from the filled shaped plastic mould when they both arrive at an end of the pressing station. It is found that this machine achieves that pressing is only required in terms of seconds as compared to the minutes required in the process and machine of the prior art.

[0008] The invention is also directed to the following process. Process to continuously produce a moulded product having a planar surface and a shaped recess wherein the following steps are performed in a linear production line having filling a filling station and a pressing station comprising the following steps:

[0009] (a) filling a shaped recess of one or more moulds from above with a liquid curable composition to obtain in one or more filled moulds having a planar upper surface in the filling station, (b) moving the one or more filled moulds from the filling station to the pressing station where the one or more moulds are covered from above by a moving belt,

[0010] (c) pressing the moving belt onto the one or more filled moulds by means of a heated pressing tool in a first part of the pressing station,

[0011] (d) moving the moving belt and the one or more filled moulds to a second part of the pressing station,

[0012] (e) curing at least the upper surface of the liquid curable composition as present in the one or more filled moulds in the second part of the pressing station,

[0013] (f) moving the one or more moulds away from the second part of the pressing station thereby separating the endless belt from the cured upper surface and reusing the endless belt in step (c) and

[0014] (g) curing the remainder of the liquid curable composition in the one or more moulds obtained in step (f) to a cured moulded product and removing the one or more cured moulded products from the one or more moulds.

[0015] Further advantages of the invention will be discussed when describing the invention in more detail below.

[0016] The machine according to the invention has a production direction and a forming station with a shaped master mould suited to form a shaped plastic film mould from a planar plastic film by thermoforming. Such machines having a forming station are known as thermoforming packaging machines. Preferably the machine is an adapted commercially available thermoforming packaging machine.

[0017] Thermoforming may be performed by known thermoforming processes. Thermoforming is a manufacturing process where the planar plastic sheet is heated to a pliable forming temperature and formed to a specific shape in the shaped master mould. The sheet is heated to a high-enough temperature that permits it to be stretched into or onto a mould and cooled to a finished shape.

[0018] The planar plastic sheet may be any type of plastic and especially plastics suitable for thermoforming such as thermoplastic films and thermoplastic foams. . The material for the plastic sheet is preferably strong at a minimum sheet thickness. The plastic is suitably a thermoplastic polymer. Examples of suitable thermoplastic polymers are polyethylene, polypropylene, polycarbonate, polystyrene and preferably polyethylene terephthalate (PET). The thickness of the sheet may vary from 50 microns to even 5 mm, wherein the lower part of the range may be used to make smaller products and the upper end of the range may be used to make larger products. For the footwear parts of this invention the thickness of the sheet suitably varies between 50 and 200 microns. When thermoplastic foams are used the thickness may be up to 3000 microns, preferably up to 600 microns.

[0019] The shaped master mould has a form negative shape of the shaped plastic film. In the thermoforming process the planar plastic film will be drawn into the shaped master mould while heating the film. The film will after cooling be shaped according to the shape of the master mould. The shaped master mould may be made from a metal. Such a master mould may be made by subtractive manufacturing wherein the master mould is manufactured by a controlled material-removal process using one or more machining tools. This method is time consuming and is preferably used when a large numbers ie more than 500, of the same moulded products are to be manufactured. When one desires to manufacture mould products having varying designs in smaller numbers, for example when making a small number of prototypes or exclusive products, it is preferred to manufacture the master mould by means of addition manufacturing, also referred to as 3D-printing. Applicants found that by using 3D printing it is possible to simply make a shaped master mould having a bespoke shape which can be economically used as part of the present machine of this invention when used for making moulded products in relatively small numbers. If the new design is to be produced in larger numbers the same moulds and supports may also be used for the large scale production.

[0020] A number of 3-D printing technologies will be available to the skilled addressee, printing in a range of materials including plaster, thermoplastics, photopolymerised polymers, or thermally-sintered materials. Specific examples of suitable materials and additive manufacturing techniques are ABS Plastic manufactured using Fused Deposition Modelling FDM, Selectively Laser Sintered SLS Nylon and Selectively Laser Sintered SLS Alumide®. Suitable printers are for example FDM 3D printers made by Ultimaker, SLS Printers, for example the ProX SLS 6100 made by 3D Systems and MJF Printers made by HP thermoplastics.

[0021] Examples of suitable shaped master moulds which can be used in the machine and process of this invention are described in US2022 / 0132989, and W02020 / 127807.

[0022] The machine of this invention also comprises a filling station suited to add a liquid curable composition to the shaped recess of the shaped plastic film mould from above such to obtain in use a filled plastic film mould. Such a filling station may be designed as the filling stations of known thermoforming packaging machines. Preferably the liquid curable composition is added to the shaped recess from above, wherein the plastic film mould or moulds move horizontally in the production direction. For this reason it is preferred that a reservoir for liquid curable composition is positioned at the filling station at an elevation higher than the horizontally moving plastic film mould or moulds.

[0023] The machine of this invention also comprises an endless belt. The endless belt covers the filled plastic film mould in the pressing station and moves together with the filled plastic film mould in the production direction when in the pressing station.

[0024] The movement in the production direction is suitably not a continuous movement. The endless belt and the plastic moulds have a stationary period and a moving period which intermits. During the stationary period the machine can simultaneously form one or more shaped plastic moulds by thermoforming in a stage (i), fill one or more previously formed plastic moulds by adding the liquid curable composition to the shaped recess of the one or more moulds in a stage (ii), press the endless belt onto the one or more previously filled plastic moulds in a stage (iii) and subject the previously filled and pressed moulds to curing in a stage (iv). The pressed moulds may be in stage (iv) for one or more cycles. By having the pressed moulds in stage (iv) for multiple cycles the time for partly curing the liquid curable composition can be adjusted. After stage (iv) the endless belt is separated from the filled plastic moulds by moving the one or more moulds in the production direction and the endless belt in a more upwardly direction.

[0025] After one stationary period, which may last for between 5 and 30 seconds the plastic moulds move in the production direction to a next stage thereby completing a cycle. The movement may take place within a short time period, for example between 1 and 10 seconds. In the new cycle a new set of one or more shaped plastic moulds are formed by thermoforming as in stage (i), the plastic moulds as formed in the previous cycle are filled by adding the liquid curable composition to the shaped recess of the one or more moulds as in stage (ii), the endless belt presses onto the one or more filled plastic moulds as filled in the previous cycle as in stage

[0026] (iii) and subject the filled and pressed moulds of the previous cycle to heat in stage

[0027] (iv). The formed plastic moulds in stages (i)-(iv) are preferably connected as is the normal practice in a thermoforming packaging machine.

[0028] The pressing station is provided with a pressing tool. This tool can move vertically and press the moving belt and the contents of the filled plastic moulds from above. A support is suitably positioned below the filled plastic moulds and vertically below the pressing tool. The pressing tool and the support suitably are vertically moveable towards the filled one or more filled plastic moulds to achieve pressing. At the end of a stationary period the pressing tool and support suitably move vertically away from the one or more filled plastic moulds to allow that the moving belt and the one or more filled plastic moulds can move to a next position in the pressing station. The pressing tool is preferably heated.

[0029] The support suitably has a form negative shape of the shaped plastic film like the master mould. The base may be made as described above for the master mould. The base is preferably made by 3D printing for the same reasons described above.

[0030] In the production direction the pressing station is provided with the pressing tool and a support to perform stage (iii) and a curing zone to perform stage (iv). The length of this curing zone and the time to perform a single cycle will determine the curing time. The length of the curing zone is preferably such that the pressed moulds in stage (iv) are present in this curing zone for between 1 and 20 cycles and suitably between 2 and 5 cycles.

[0031] In the curing zone the filled plastic moulds or pressed plastic moulds as described above are covered by the endless belt. The pressing station preferably comprises of heating means. These heating means may comprise of the heated pressing tool and heating means as present in the curing zone. The heating means as present in the curing zone are preferably radiation heating means, preferably positioned above the filled plastic moulds as covered by the endless belt. The radiation heating means direct a radiation towards the filled plastic moulds from above. Such a positioning enables that the film of cured material at the surface facing the endless belt is formed more easily.

[0032] The radiation heating means generate a radiation beam having a wavelength. The wavelength of the radiation beam generated by the radiation means will depend on the choice of the material of the endless belt and / or the curable composition and may range from ultra violet, visible light to infra red. The radiation may also be electromagnetic radiation such as microwave or radio waves. Preferably the radiation beam is an infra red radiation. The radiation heating means may heat up the endless belt which in turn heats up the curable composition. Alternatively the radiation heating means directly heat the curable composition.

[0033] The endless belt may have a continuous surface or made from interconnected segments. The dimensions of such a segment are preferably such that one segment covers the one or more filled plastic moulds in the pressing stage (iii). This results in that after performing stage (iv) one segment of the endless belt is separated from the filled plastic moulds by moving the one or more moulds in the production direction and the segment of the endless belt moves in an upwardly direction.

[0034] Preferably the endless belt has a surface facing the filled moulds which does not adhere or does not significantly adhere to the film of cured material as formed in the filled plastic mould. By not significantly adhere is here meant that it is possible to separate the endless belt from the filled plastic moulds after performing stage (iv). A suitable surfaces is a polytertrafluoroethylene (PTFE) comprising surface. Preferably the endless belt is a fibre reinforced polytertrafluoroethylene (PTFE) belt.

[0035] The endless belt may be provided with a textured surface facing the curable composition. This textured surface of the endless belt will result in that the upper surface of the moulded product will be textured.

[0036] The endless belt is guided by two or more belt rollers which belt rollers are positioned perpendicular to the production direction such that the endless belt covers the filled plastic film mould and moves together with the filled plastic film mould in the production direction while performing stage (iii) and (iv).

[0037] At the end of the curing zone the endless belt is removed from the one or more filled plastic moulds. A vacuum seal may be formed between the endless belt and the film of cured material. In order to break such a seal a mechanical or air tool may suitably be present at the end of the curing zone. The endless belt preferably moves upwardly away from the filled plastic mould or moulds at the end of the curing zone in order to remove the endless belt from the one or more filled plastic moulds. This is achieved by the configuration of the belt rollers. The endless belt is guided back in the opposite direction of the production direction to be used in the pressing stage. The endless belt is guided back in an zone positioned above where the endless belt and the plastic moulds move in the production direction. In this zone cleaning means may be present to clean the surface of the endless belt.

[0038] Preferably a cutting station is part of the apparatus suited to separate one or groups of multiple cured or semi-cured filled plastic film moulds from each other. Such a cutting station is positioned after the pressing station and after the endless belt in the production direction. One or more cured or semi-cured filled plastic film moulds not covered by the endless belt may be separated from the filled plastic moulds present in the pressing station by cutting. Cutting is suitably performed in the stationary period in a stage (v). The separated one or more moulds filled with partly cured material are kept in a curing zone. Such a zone may be racks supporting the one or more moulds. The machine according to this invention is suitably used in the process of this invention.

[0039] The mould having a shaped recess of step (a) is suitably a thermoformed shaped plastic film mould as described above.

[0040] In step (a) a shaped recess of a mould is filled from above with a liquid curable composition. A preferred curable material is a so-called cold pour curing material. Such liquid materials are well known. They can be formulated just before use and poured into the mould at for example ambient conditions. Examples of suitable cold pour curing materials are silicone rubber, thermoplastic rubber, natural rubber, polyurethane (Pll) and thermoplastic polyurethane (TPU). Preferably the liquid curable material is natural rubber latex, agar agar, gelatin, mycelium, silicone or compact polyurethane and preferably natural rubber latex.

[0041] Applicants found that it is possible with this process to combine the liquid curable material with solid particles or fibres of comprisable materials. Examples of such solid materials are regrind injected moulded ethyl vinyl acetates (EVA), regrind injected moulded polyurethane (Pll), cork, recycled natural rubber, shredded footwear components and cotton fibres. The solid particles preferably have a greatest dimension of between 1 and 6 mm. The fibres preferably have a length of between 1 and 10 mm.

[0042] Because the process involves a pressing step (b) wherein the material is partly cured it has been found that it is possible to increase the amount of solid particles or fibres of comprisable materials in the moulded product. The process enables to add between 30 and 80 vol% or between 30 and 50 vol.% of solid particles or fibres of comprisable materials in the final suspension which is added in step (a). Preferably the moulds are filled with a volume of suspension which is higher than the volume of the final moulded product. More preferably the volume of suspension added to the moulds is between 5-30 preferably 5-20%, higher than the volume of the final moulded product. The above referred to ambient conditions may be between 5 and 50 C, preferably between 10 and 30 C and the pressure may be between 0.08 MPa and 0.12 Mpa, more preferably at ambient pressure.

[0043] In step (b) pressing the filled mould is pressed from above with a moving endless belt which belt moves together with the filled mould for a certain distance such that the upper surface of the liquid curable composition is cured. This curing is preferably enhanced by subjecting the liquid curable composition to radiation. Preferably the liquid curable composition is radiated from above and more preferably the liquid curable composition is radiated by infrared from above. Step (b) is preferably performed in the stages (i)-(iv) as described above.

[0044] In step (c) the endless belt is separated from the cured upper surface and reusing the endless belt in step (b). This separation and reuse may be as described above.

[0045] In step (d) the remainder of the liquid curable composition is cured in the mould to a cured moulded product and removing the cured moulded product from the mould. Step (d) is preferably performed in a conditioned climate suitably having a temperature of between 40-50 °C and at a relative humidity of between 5 and 15%.

[0046] Preferably step (c)-(f) are performed in between 10 and 30 seconds and wherein step (g) is performed in between 1 and 12 hours. The one or more shaped plastic film mould of step (a), the one or more filled mould of step (c) and the one or more filled mould of step (e) are suitably connected to each other and wherein the one or more filled mould of step (g) are disconnected from the one or more moulds of steps (a), (c) and (e). This results in that the filled plastic moulds are contained in a machine performing steps (a)-(c) for a relatively short period as compared to the period in which the final curing takes place. This enables a high throughput for the machine. Further the final curing of step (d) may takes place in relatively simple plastic moulds which can be separately stored in racks. The plastic film moulds obtained after removing the cured moulded product from the mould may be recycled. Preferably the plastic moulds are mechanically recycles to a planar plastic film which may be used in step (a).

[0047] The moulded products which can be produced with this machine or process may be any product having a planar surface. Preferably the moulded products are footwear parts such as inner and outer soles.

[0048] Figure 1 shows a schematic presentation of the machine for continuously producing moulded products according to this invention. A forming station (1 ) is shown where a shaped plastic film mould (2) having a downwardly extending shaped recess (3) is made from a planar plastic film (4) by thermoforming using a shaped master mould (5). The production direction is to the left and presented by arrow (6). A filling station (7) provided with a reservoir (8) for liquid curable composition as positioned at an elevation higher than the shaped plastic film mould (2). From this reservoir liquid curable composition is added to the shaped recess (3) of a shaped plastic film mould (2) from above via supply line (9) such to obtain a filled plastic film mould (10). The shaped plastic film mould (2) as present in the filling station (7) has been made in the forming station in a previous cycle. As shown the volume of liquid curable composition (11 ) in the filled plastic film mould (10) exceeds the upper end of the filled plastic film mould (10).

[0049] In a first part (12) of pressing station (13) this volume of liquid curable composition is covered by an endless belt (14) and pressed by a pressing tool (15) which can move downwards from the shown position and supported by a support (16) which can move upwards from the shown position. The pressing tool is heated such to enhance the formation of a covering film in the filled plastic film mould (10). The filled plastic film mould (10) as present in the first part (12) of pressing station (13) has been prepared in the filling station (7) in a previous cycle.

[0050] In a second part (17) of the pressing station (13) the filled plastic film mould (10) which in a previous cycle or cycles were in the first part (12) of the pressing station (13) remain covered by endless belt (14) and are further cured. Curing is enhanced by directing infrared radiation by radiation means (18) to the filled plastic film mould (10) from above. At the end of the pressing station (13) in the production direction (6) the endless belt (14) separates from the from the cured upper surface of the filled plastic film mould (10) as shown. A cutting station (19) is present after the pressing station and after this separation of the endless belt in the production direction. In the cutting station (19) separated cured or semi-cured filled plastic film moulds (20) are obtained which can be stored in a curing zone (21 ). Multiple cured or semi-cured filled plastic film moulds (20) are shown in curing zone (21 ). After being fully cured the moulded products (22) having a planar surface (23) are obtained by removing the cured moulded products (22) from the plastic film mould (2) in product zone (24).

Claims

CLAIMS1 . A machine for continuously producing moulded products having a planar surface and a shaped recess wherein the machine has a production direction and wherein in the production direction the following stations are comprised: a forming station with a shaped master mould suited to form a shaped plastic film mould from a planar plastic film by thermoforming and wherein the shaped plastic film mould has a downwardly extending shaped recess, a filling station suited to add a liquid curable composition to the shaped recess of the shaped plastic film mould from above such to obtain in use a filled plastic film mould, and a pressing station comprising of a pressing tool and an endless belt guided by two or more belt rollers which belt rollers are positioned perpendicular to the production direction such that the endless belt covers the filled plastic film mould and moves together with the filled plastic film mould in the production direction to obtain in use a cured or semi-cured filled plastic film mould.

2. A machine according to claim 1 , wherein the endless belt has a polytertrafluoroethylene (PTFE) comprising surface.

3. A machine according to claim 2, wherein the endless belt is a fibre reinforced polytertrafluoroethylene (PTFE) belt.

4. A machine according any one of claims 1-3, wherein heating means are present above the endless belt at the pressing station.

5. A machine according to claim 4, wherein the heating means are radiation means.

6. A machine according any one of claims 1-5, wherein a cutting station is part of the apparatus suited to separate one or groups of multiple cured or semi-cured filled plastic film moulds from each other.

7. Process to continuously produce a moulded product having a planar surface and a shaped recess wherein the following steps are performed in a linear production line having filling a filling station and a pressing station comprising the following steps:(a) filling a shaped recess of one or more moulds from above with a liquid curable composition to obtain in one or more filled moulds having a planar upper surface in the filling station,(b) moving the one or more filled moulds from the filling station to the pressing station where the one or more moulds are covered from above by a moving belt,(c) pressing the moving belt onto the one or more filled moulds by means of a heated pressing tool in a first part of the pressing station,(d) moving the moving belt and the one or more filled moulds to a second part of the pressing station,(e) curing at least the upper surface of the liquid curable composition as present in the one or more filled moulds in the second part of the pressing station,(f) moving the one or more moulds away from the second part of the pressing station thereby separating the endless belt from the cured upper surface and reusing the endless belt in step (c) and(g) curing the remainder of the liquid curable composition in the one or more moulds obtained in step (f) to a cured moulded product and removing the one or more cured moulded products from the one or more moulds.

8. Process according to claim 7, wherein in step (e) the liquid curable composition is radiated from above.

9. Process according to claim 8, wherein in step (e) the liquid curable composition is radiated by infrared from above10. Process according to any one of claims 7-9, wherein the liquid curable composition is natural rubber latex, agar agar, gelatin, mycelium, silicone or compact polyurethane.11 . Process according to claim 10, wherein the liquid curable composition is natural rubber latex.

12. Process according to any one of claims 7-11 , wherein the liquid curable composition further comprises solid compressible particles and / or fibres.

13. Process according to claim 12, wherein the liquid curable composition comprises between 30 and 80 vol% of compressible solids and / or fibres.

14. Process according to any one of claims 12-13, wherein in step (a) the added volume of liquid curable composition and compressible solids and / or fibres to the mould is between 5 and 30 percent higher than the volume of the moulded product obtained in step (g).

15. Process according to any one of claims 7-14, wherein steps (c)-(f) are performed in between 10 and 30 seconds and wherein step (g) is performed in between 1 and 12 hours.

16. Process according to any one of claims 7-15, wherein the one or more moulds having a shaped recess of step (a) is a thermoformed shaped plastic film mould.

17. Process according to claim 16, wherein the one or more shaped plastic film moulds of step used in step (a), the one or more filled moulds of step (c) and the one or more filled moulds of step (e) are connected to each other and wherein the one or more filled moulds of step (g) are disconnected from the one or more moulds of steps (a), (c) and (e).

18. Process according to any one of claims 7-17 as performed in an apparatus according to any one of claims 1-6 wherein the moulds move in the production direction in a non-continuous movement consisting of repeating cycles involving of a stationary period and a moving period,wherein during the stationary period the machine simultaneously forms one or more shaped plastic moulds by thermoforming in a stage (i), fill one or more previously formed plastic moulds by adding the liquid curable composition to the shaped recess of the one or more moulds in a stage (ii), press the endless belt onto the one or more previously filled plastic moulds in a stage (iii) and subject the previously filled and pressed moulds to heat in a stage (iv) and wherein during a moving period the plastic moulds move in the production direction to a next stage thereby completing a cycle.

19. Process according to clam 18, wherein the stationary period lasts for between 5 and 30 seconds and the moving period lasts for between 1 and 10 seconds.

20. Process according to any one of claims 7-19, wherein the moulded product is a footwear part.

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