Process to prepare a footwear product

Abstract

The invention is directed to a process to manufacture a footwear product comprising a shoe upper connected to a sole or midsole wherein the process comprises the following steps, (a) placing a last having an opening and in a shoe upper thereby covering the foot bed. (b) placing the shoe upper in a mould made of a thermoformed plastic film such that a cavity remains below the footbed of the shoe upper, (c) adding a curable liquid from above through the openings to fill the cavity, (d) curing the curable liquid to obtain a sole as attached to the footbed of the shoe upper and (e) removing the footwear product from the mould. Steps (b) and (c) are performed in a linear production line comprising a sequence of a thermoforming station, a placing station and a filing station.

Description

[0001] PROCESS TO PREPARE A FOOTWEAR PRODUCT

[0002] The invention is directed to a process to manufacture a footwear product comprising a shoe upper connected to a sole or midsole.

[0003] US4858337 describes a method to prepare a footwear product having a rubber sole. In this method an upper, midsoles and outsoles are separately fabricated and subsequently joined together.

[0004] US2022 / 0132989 describes a process to make a midsole or sole of rubber in a plastic mould made by thermoforming. 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 footwear outsoles, cures in complex metal moulds made by substrative machining.

[0005] US2014 / 0068879 describes a method where a midsole is attached to an upper by placing the upper in a moulding tool. A receiving space below the upper in the moulding tool is created to which receiving space a flowable plastic material is supplied. After solidification of the plastic material an upper is obtained having a midsole of solidified material.

[0006] US2018 / 0325215 describes a process for connecting a polyester knitted upper to a rubber sole by moulding the sole to the upper. By providing a high stich density at the lower edge of the knitted upper the flow of curable liquid is limited resulting in a good and stable contact.

[0007] The object of the present invention is to provide a process which can manufacture a product comprising a shoe upper connected to a sole or midsole made of a curable liquid in a simple manner.

[0008] This object is achieved by the following process.

[0009] A process to manufacture a footwear product comprising a shoe upper connected to a sole or midsole wherein the process comprises the following steps

[0010] (a) placing a last having a conduit provided with an inlet opening and an outlet opening in a shoe upper having a foot bed provided with a footbed opening thereby covering the foot bed with the last and wherein the outlet opening of the conduit aligns with the footbed opening of the shoe upper,

[0011] (b) placing the shoe upper with the last as obtained in step (a) in or onto a mould made of a thermoformed plastic film such that a cavity remains below the footbed of the shoe upper,

[0012] (c) adding a curable liquid from above through the aligned openings of the footbed of the shoe upper and the partial last to fill the cavity,

[0013] (d) curing the curable liquid to obtain a sole or midsole as attached to the footbed of the shoe upper,

[0014] (e) removing the shoe upper from the mould, and wherein step (b) and (c) are performed in a linear production line comprising a sequence of a thermoforming station, a placing station and a filing station and wherein the following steps are performed:

[0015] (i) making the mould in the thermoforming station,

[0016] (ii) performing step (b) by placing the shoe upper in the mould in the placing station and

[0017] (iii) performing step (c) in the filling station and wherein the moulds of steps (i)-(iii) are the moulds made by thermoforming and are interconnected moulds which intermittently move from the thermoforming station to the filing station.

[0018] The process is advantageous because it can manufacture a shoe upper connected to a sole or mid sole made of a curable liquid having long curing times. In a prior art process long curing times are not desired because large numbers of complex metal moulds would then be required when producing large numbers. In the present process the moulds are simpler as they are made by thermoforming a plastic film. The process further allows to simply combine various designs and / or colours for the sole or mid sole to a shoe upper by simply using a differently shaped thermoformed mould in step (b) and / or a different curable liquid in step (c). Further advantages will be explained when describing the invention in more detail below.

[0019] Terms like above or below are used to describe the preferred manner in which the process may be performed.

[0020] The shoe upper may be made of any material. For example the shoe upper may be made by injection moulding of a curable liquid. Examples of suitable shoe uppers made by injection moulding are rubber shoe uppers, polyethylene vinyl acetate uppers, polyamide uppers and polyurethane uppers. The shoe upper may also be a leather upper, a cotton canvas upper or a suede upper. The process is advantageous to connect a rubber upper with a rubber sole or mid sole and more preferably to connect to a natural rubber sole or mid sole. The process allows to simply combine various designs and / or colours for the sole or mid sole to a rubber upper by simply using a differently shaped thermoformed mould in step (b).

[0021] The advantages of the process are even more apparent when the shoe upper is a knitted sock. The curable liquid can enter the openings of the knitted material in step (c). In this way the curable liquid can intimately contact the footbed of such a sock in step (c) and (d) and form a very strong connection between the sole and the sock. Such a knitted upper is well known and for example described in the afore mentioned US2018 / 0325215 and in EP3954815, US2022 / 0154374, US2020 / 0170330, US2018 / 0343959, EP3564422 and US2018 / 0303204. The yarn used to knit the knitted upper may be polyester, polyamide and is preferably a natural yarn such as cotton, hemp or jute.

[0022] In step (a) a last is placed in the shoe upper. The last may be a metal part, a wooden part, a ceramic part or a plastic part or a combination of such materials. The last may be made by subtractive or additive manufacture. Preferably the part of made by additive manufacture, also referred to as 3D printing. The last may also be a partial last as will be described in more detail below, preferably obtained by thermoforming of a plastic film. The last or partial last is preferably reused in the process. When reference is made to last also a partial last is meant unless explicitly excluded.

[0023] The last may be a full last or a partial last. The full last as used in this process may be a well known last used in the footwear industry. The difference with the well known full last is that a conduit is present having an inlet opening and an outlet opening. The inlet opening is present at the upper end of the last when viewed as how a person would wear footwear. The outlet opening is present in the sole of the last.

[0024] A partial last is in essence the lower part of a full last. The partial last thereby covers the footbed of the shoe upper. Preferably the shape of the partial last is such that it covers the footbed of the shoe upper and that an upright edge is present along the circumference of the partial last. The upright edge may be between 5 and 30 mm, preferably between 10 and 15 mm wide. The upright edge is shaped such that it can align with the internal shape of the shoe upper, for example by bending. The upright edge has the function to keep the partial last fixed to the footbed while step (c) and (d) is performed. When the shoe upper is a knitted sock the partial last further avoids that excess curable liquid flows into passes the footbed of the shoe upper.

[0025] The partial last is provided with an outlet opening which aligns with the footbed opening in the footbed of the shoe upper. This opening and the aligned opening in the footbed of the shoe upper allows that a curable liquid can be added from above and into the cavity in step (c). To the opening of the partial last an open-ended conduit may be present. This conduit extends upwards and allows a simple connecting between the means to supply the natural latex in step (c) and the opening in the partial last. This conduit is an integral part of the partial last and is formed when manufacturing the partial last by thermoforming. To said conduit a funnel may be provided to receive the curable liquid when provided from above.

[0026] The plastic film used to manufacture the partial last of step (a) when made by thermoforming and the mould of step (b) may be any type of plastic and especially plastics suitable for thermoforming such as thermoplastic films. The material for the plastic film 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 film suitably varies between 50 and 300 microns. For the mould a material is preferred which can withstand the more elevated temperatures when curing the curable liquid in step (d). Curing typically involves exothermic reactions which result in a temperature rise. Preferably a curable liquid is chosen which does not result in a high temperature rise and / or a large expansion to avoid deformation of the mould. Further a curable liquid is also preferred in that it does not require a pressure build up in the cavity in steps (c) and (d). Thus the pressure in the cavity is the same as the ambient pressure. This is advantageous because it simplifies how the shoe upper with the last is placed in or onto a mould. Because no or almost no pressure is build up in the cavity the shoe upper only has to be positioned in or above the mould and no extra force is required to counter force any pressure build up. This even allows for the shoe upper to hover above the mould leaving a small gap between shoe upper and the mould. This results in a small ridge of the sole or midsole along the shoe upper which is typical for footwear made by this process. The gap also allows air to escape from the mould as the curable liquid fills the mould. The gap also increases tolerances for both the fluid quantity and size and shape of the shoe upper thereby simplifying the manufacture of the shoe upper. A curable liquid which does not result in a high temperature rise and / or a large expansion is preferably a free flowing curable liquid and more preferably a curable poly urethane, a curable silicon, a curable synthetic rubber or a curable natural rubber.

[0027] Thermoforming is a well-known manufacturing technique, where a plastic film is heated and drawn into a shaped master mould. 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 costly and time consuming and is preferably used when a large numbers i.e. more than 500, of the same moulded products are to be manufactured. For the present invention it is preferred that the partial last is manufactured by thermoforming wherein the master mould is obtained by means of additive manufacturing, also referred to as 3D-printing. Applicants found that by using 3D printing it is possible to more simply make different shaped master moulds for different sized partial lasts and moulds. In this way it is possible to manufacture different designed footwear products in different sizes using less complicated master moulds. If one of these designs is to be produced in larger numbers the same master moulds may also be used for the large scale production.

[0028] 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.

[0029] Examples of suitable shaped master moulds and how they are used in a thermoforming manufacturing process are described in applicants patent applications US2022 / 0132989 and W02020 / 127807.

[0030] In step (a) the last is placed in the shoe upper. This is state of the art technology well known in the footwear industry. When making use of the novel partial last it is preferred to place the partial last making use of a tool, especially when the partial last is made of a thin plastic film. This tool is suitably a reusable last applicator. The preferred reusable last applicator can releasably connect to the partial last to form a combined object. This combined object has dimensions which allow the combined object to enter the interior of the shoe upper. In step (a) the combined object is placed in the shoe upper. By placing the combined object the partial last is positioned onto the footbed of the shoe upper. After the combined object is placed in the shoe upper the reusable last applicator is disconnected from the partial last and removed from the shoe upper before step (c) is performed. The reusable last applicator may be releasably connected to the partial last by means of a snap fit connection. The reusable last applicator may be made of a metal or of an engineering plastic. It can be obtained by 3D printing.

[0031] In step (a) the placing the last or partial last may be performed manually or in an automated manner. For example, a robot may pick a partial last using the reusable last applicator and place the combined object in the shoe upper. The reusable last applicator may be part of an arm of the robot. When the robotic arm retrieves from the shoe upper the partial last and last applicator disconnect and the partial last remains on the footbed of the shoe upper. The robotic arm with the reusable last applicator can then pick a next partial last and perform a next step (a).

[0032] In step (b) the shoe upper with the last as obtained in step (a) is placed in or onto a mould. The mould is made of a thermoformed plastic film. When placed a cavity remains below the footbed of the shoe upper defined by the mould and the footbed of the shoe upper. This cavity may be enclosed by the shoe upper touching the upper end of the mould. The shoe upper may also be positioned slightly above the mould where the shoe upper and the mould are distanced by a gap. The width of this gap between the mould and the shoe upper may be between 1 and 10 mm. Such a gap shaped opening is advantageous because it allows air to escape from the cavity when the curable liquid is added in step (c).

[0033] In step (c) a curable liquid is added from above through the opening to fill the cavity. The curable liquid may be any curable liquid which does not expand too much when curing and does not give rise to excessive temperature rise when curing. Examples of suitable curable liquids are curable poly urethane, a curable silicon, a curable synthetic rubber or a curable natural rubber.

[0034] A preferred curable liquid is natural latex obtained as a liquid from a rubber tree. Other sources of natural latex are guayule plant and dandelion flowers. Natural latex is an aqueous suspension of rubber particles. The suspension may for example comprise of between 40 and 50 wt% water and between 50 and 60 wt% rubber particles. The natural latex may comprise preserving agents and additives like ammonia. Natural latex may be slightly different depending on its origin and the presence of ammonia and its content. The rubber particles are comprised of rubber polymers contained in an outer shell of a protein membrane. Curing of the latex involves dissolving the protein membrane and evaporation of the water resulting in coagulation of the rubber particles. Gelling agents are mixed with the latex to enhance dissolving of the protein membrane. The natural latex suitably contains such a gelling agent. Examples of suitable gelling agents are acid coagulants, for example formic acid, siloxane based heat sensitisers and / or sodium silico fluoride. The optimal ratio of natural latex and gelling agent depends on the type of natural latex used and the type of gelling agent. When adding a natural latex care should be given to avoid excessive strain on the flow of natural latex such to avoid premature coagulation.

[0035] In step (d) the curable liquid is cured to obtain a solid sole or mid sole as attached to the shoe upper. Curing can be performed under normal curing conditions for the curable liquid. The process is advantageous in that the most optimal curing conditions can be chosen in terms of temperature and pressure without being limited to a certain maximum curing time or time in mould. This because the moulds are made by thermoforming and for a single use. Thus, the time in mould will not negatively influence the production speed. The optimal condition for curing the curable liquid depends on the type of curable liquid.

[0036] For the preferred natural rubber the curing of the sole or mid sole is suitably performed at a relatively lower temperature of between 30 and 80 °C, preferably between 40 and 60 °C, for a period of between 1 and 3 hours in step (d) before removing the shoe upper from the mould. This may be performed in a climate chamber where the moulds are placed in racks. Moulds may be connected to each other and placed as a whole in such a rack. In step (d) the natural rubber solidifies sufficiently for removing the sole or mid sole from the mould. For example a natural rubber may cure to a point where it does not flow anymore, like a gel, enabling the removal of the mould. After removing the shoe upper from the mould the shoe upper is suitably positioned with the sole pointing upwards to avoid deformation. The shoe upper is then suitably further dried at a temperature of between 30 and 80 °C, preferably between 60 and 80 °C, for a period of between 8 and 24 hours, preferably between 8 and 12 hours. Drying at ambient conditions, for example at 30 C, has been found possible. A final vulcanisation is performed on the shoe upper at a temperature of above 80 °C and preferably between 80 and 120 °C, more preferably between 90 and 100 °C for a period of between 30 minutes and 3 hours. After this high temperature curing a low temperature post curing / drying may be performed to obtain a fully cured and dried product. The low temperature post curing / drying step may be performed at between 20 and 60 °C, preferably between 40 and 50 °C for a period of between 6 and 30 hours, preferably between 15 and 30 hours. Preferably a fully dried shoe upper is subjected to the final vulcanisation thereby avoiding a post vulcanisation drying step.

[0037] Any high temperature curing may be performed in an oven or in a ventilated space where the temperature can be controlled. The post curing / drying step may be performed in the same oven or space. Preferably the post curing / drying step is performed in a ventilated space where the temperature and humidity can be controlled. This allows a more efficient use of the high temperature oven when manufacturing high numbers of footwear.

[0038] After performing step (d) the footwear product is removed from the mould in step (e). This may be performed manually or automatically. A rubber sole or mid sole will have shrunk in the mould facilitating its removal.

[0039] The last may be removed from the from the shoe upper prior, during or after step (e). It is found that a partial last made of PET film can be easily removed from the footwear product.

[0040] The process according to this invention is advantageous because it can be performed in a semi-automated or fully automated manner making use of a linear production line. Step (b) and step (c) are performed in such a linear production line comprising a sequence of a thermoforming station, a placing station and a filing station. The following steps are performed in such a linear production line:

[0041] (i) making a mould in the thermoforming station,

[0042] (ii) performing step (b) by placing the shoe upper in a mould in the placing station and

[0043] (iii) performing step (c) by adding the curable liquid through the aligned openings of the footbed of the shoe upper and the partial last to a mould in the filling station.

[0044] The moulds in steps (i)-(iii) are the moulds by thermoforming. These moulds are interconnected while performing steps (i)-(iii). The interconnected moulds intermittently move from the thermoforming station to the filing station. The different stations may be at different locations along the linear production line. The location of two stations may also be at the same location. For example, the placing and filling station may be at the same location. The intermittent movement is to bring the mould or moulds to the next station when a step is completed. Because the moulds are interconnected the time at which the moulds are stationary, i.e. at one station, will be determined by the most time-consuming step. In practice this is usually step (iii) wherein step (c) of the process is performed. The time at which the moulds are stationary at a station may be between 5 and 30 seconds. The time where the moulds move between two stationary periods may be less than 10, preferably less than 5 seconds, for example less than 2 seconds.

[0045] Preferably the linear production line further comprises a cutting station after the filing station. At the cutting station the interconnected moulds obtained in step (iii) are cut into sections at the start of step (d) or prior to step (d). Cutting into sections allows one to more effectively store the moulds, for example in the above referred to racks, while performing step (f). Suitably steps (i)-(iii) for a single mould is performed in a time period of between 10 and 30 seconds and wherein step (d) is performed in a time period of between 1 hours and 12 hours. By cutting it is possible to perform steps (i)-(iii) in the linear production line and perform step (d) independent of the linear production line at the elevated temperatures as described above.

[0046] In the thermoforming station one or more moulds can be made simultaneously. For example, between 1 and 4 moulds can be made simultaneously. Preferably the curable latex is then also added simultaneously in a step (iii) to the moulds which are formed simultaneously in a previous step (i). The placing in step (ii) do not necessarily have to be performed simultaneously. For example the shoe uppers may be placed one at a time, manually or automatically.

[0047] The moulds and partial last made by thermoforming and obtained in this process may be recycled. Preferably the plastic moulds are mechanically recycled to a plastic film which may in turn be used to make the partial last for use in step (c) and / or the mould for use in step (d). The used plastic moulds as obtained in this process may also be reused to make a footwear product comprising a shoe upper connected to a sole or midsole, preferably according to some aspects of this invention. Preferably the used plastic mould is reused to make a footwear product comprising a shoe upper connected to a sole or midsole wherein the process comprises the following steps (aa) placing a last having a conduit with an inlet opening and an outlet opening in a shoe upper having a foot bed provided with a footbed opening thereby covering the foot bed with the last and wherein the outlet opening of the conduit aligns with the footbed opening of the shoe upper, (bb) placing the shoe upper with the last as obtained in step (aa) in or onto the used plastic mould made of a thermoformed plastic film such that a cavity remains below the footbed of the shoe upper,

[0048] (cc) adding a curable liquid from above through the conduit of the last and via the aligned opening of the footbed opening of the shoe upper to fill the cavity,

[0049] (dd) curing the curable liquid to obtain a sole or midsole as attached to the footbed of the shoe upper, and

[0050] (ee) removing the shoe upper from the plastic mould.

[0051] Steps (aa), (bb), (cc), (dd) and (ee) may be performed as described for steps (a), (b), (c), (d) and (e) of this invention respectively. In this process the used plastic moulds are not interconnected or are groups of a small number of connected plastic moulds. For this reason the step (bb) and (cc) are preferably performed in a linear production line not comprising a thermoforming station, and comprising a placing station and a filing station and wherein the following steps are performed:

[0052] (Aii) performing step (bb) by placing the shoe upper in or onto the plastic mould in the placing station and

[0053] (Aiii) performing step (cc) in the filling station.

[0054] Steps (Aii) and (Aiii) may be performed as described for steps (ii) and (iii) of this invention respectively. Step (dd) is preferably performed substantially not in the linear production line and performed separate from the linear production line in for example racks as described above for step (d).

[0055] The plastic moulds as used in the process may be used moulds as obtained in a step (e) of the process of this invention or alternatively be plastic moulds directly obtained by thermoforming. For this reason the invention is also directed to the following process. Process to make a footwear product comprising a shoe upper connected to a sole or midsole wherein the process comprises the following steps

[0056] (aaa) placing a last having a conduit with an inlet opening and an outlet opening in a shoe upper having a foot bed provided with a footbed opening thereby covering the foot bed with the last and wherein the outlet opening of the conduit aligns with the footbed opening of the shoe upper,

[0057] (bbb) placing the shoe upper with the last as obtained in step (aaa) in or onto the a plastic mould made of a thermoformed plastic film such that a cavity remains below the footbed of the shoe upper, (ccc) adding a curable liquid from above through the conduit of the last and via the aligned opening of the footbed opening of the shoe upper to fill the cavity,

[0058] (ddd) curing the curable liquid to obtain a sole or midsole as attached to the footbed of the shoe upper, and

[0059] (eee) removing the shoe upper from the plastic mould.

[0060] Steps (aaa), (bbb), (ccc), (ddd) and (eee) may be performed as described for steps (a), (b), (c), (d) and (e) of this invention respectively. In this process the plastic moulds are not interconnected or are groups of a small number of connected plastic moulds. Preferably the process is performed making use of two separate linear production lines X and Y, wherein linear production line X comprises a thermoforming station and a cutting station and linear production line Y comprises comprising a placing station and a filing station and wherein the following steps are performed:

[0061] (Bi) making the plastic mould in the thermoforming station of linear production line X to obtain interconnected thermoformed moulds and cutting the interconnected thermoformed moulds in the cutting station of the linear production line X to obtain single or groups of plastic moulds,

[0062] (Bii) performing step (bbb) by placing the shoe upper in or onto the plastic mould obtained in step (Bi) in the placing station of the linear production line Y and

[0063] (Biii) performing step (ccc) in the filling station of linear production line Y.

[0064] Steps (Bi), (Bii) and (Biii) may be performed as described for steps (ii) and (iii) of this invention respectively. Step (ddd) is preferably performed substantially not in the linear production line Y and performed separate from the linear production line Y in for example racks as described above for step (d).

[0065] In the above processes steps (Aii)-(Aiii) or (Bi)-(Biii) for a single mould may be performed in a time period of between 10 and 30 seconds.

[0066] The invention will be illustrated by the following Figures.

[0067] Figure 1 shows a shoe upper (1) having a footbed opening (2) in its footbed (3).

[0068] Figure 2 shows a partial last (6) having a footbed (7) and an upright edge (9). The partial last (6) is provided with a conduit (13) having an inlet opening (4) and an outlet opening (5). Figure 3 shows the shoe upper (1) of Figure 1 combined with the partial last (6) of Figure 2. To position the partial last (6) in the shoe upper (1) a last applicator (12) is connected to the partial last (6). This last applicator (12) is subsequently removed as shown in Figure 4.

[0069] Figure 5 shows the shoe upper (1) with the partial last (6) of Figure 4 as placed in a mould (14) made by thermoforming. This results in that a cavity (15) remained below the footbed (3) of the shoe upper (1).

[0070] Figure 6 shows the shoe upper (1) on the mould (14) of Figure 5 connected to a supply conduit (11) for a curable liquid. The supply conduit (11) is fluidly connected to conduit (13) such that curable liquid flows via the partial last (6) into the cavity (15) as shown by the dotted markings. The curable liquid can cure and take the shape of the mould (14) to obtain a sole (17) as connected to the footbed (3) of the shoe upper (1). When the sole (17) is cured the resulting footwear product (16) is removed from the mould (13).

[0071] Figure 7 shows the footwear product (16) as separated from the mould (14) and consisting of the shoe upper (1) connected to a sole (17).

[0072] Figure 8 shows a shoe upper (1) on a mould (14) as in Figure 6 except in that instead of a partial last (6) a full last (8) is positioned within the shoe upper (1). The shoe upper is placed onto the mould (14) where the shoe upper (1) and the mould (14) are distanced by a gap (18). The full last (8) is provided with the conduit (13). . The supply conduit (11) is fluidly connected to conduit (13) such that curable liquid flows via the partial last (6) into the cavity (15) as shown by the dotted markings. The curable liquid can cure and take the shape of the mould (14) to obtain a sole (17) as connected to the footbed (3) of the shoe upper (1). When the sole (17) is cured the resulting footwear product (19) is removed from the mould (13).

[0073] Figure 9 shows a detail of the toe section of the shoe upper (1) of Figure 8. The gap (18) is shown in more detail where the width (dd) of this gap (18) may be between 1 and 10 mm. Such a gap shaped opening is advantageous because it allows air to escape from the cavity when the curable liquid is added in step (c).

[0074] Figure 10 shows the footwear product (19) as separated from the mould (14) and consisting of the shoe upper (1) connected to a sole (17). Footwear product (19) is different from footwear product (16) of Figure 7 in that at the upper end of the sole (17) a ridge (20) is present as a result of the gap (18).

[0075] Figure 11 illustrates a linear production line (21) comprising a sequence of a thermoforming station (22), a placing station (25), a filing station (26) and a cutting station (27). In the thermoforming station a plastic film (24) as supplied from a roll (23) is heated and drawn into a shaped master mould wherein a mould (14) is made by thermoforming. This thus obtained mould (14) is moved to the placing station (25) while still being connected to the plastic film (26). In this manner a row of interconnected moulds (14) are produced in the thermoforming station (22). In the placing station (25) a shoe upper (1) with a full last (8) inside is placed onto the mould (14). After placing the shoe upper (1) the combined shoe upper (1) and mould (14) is moved to the filling station (26) while still being connected at its left side to new moulds (14). In the filling station (26) curable liquid is added from a curable liquid reservoir (27) above through the conduit (11) and the conduit (13) of the last and via the aligned opening (2) of the footbed opening (3) of the shoe upper (1) to fill the cavity (15). After filling the cavity (15) the mould (14) with the shoe upper (1) is moved in the direction of arrow (a) to the cutting station (27) where the moulds (14)- shoe upper (1) combinations (30) are disconnected from the row of interconnected moulds (14). This allows curing of the combinations (30) separate from the linear production line (21) in a curing section (28). At the end of the curing time the combination (30) is removed from the curing section (28), arrow (b), to a separation section (29) where the mould (14) via arrow (c), and the last (8), via arrow (d), are removed from the shoe upper-(l) sole (17) to obtain the footwear product (19) via arrow (e). The full last (8) can be reused to make new footwear products and the used mould (14) may be mechanically or chemically recycled.

[0076] Figure 12 shows a partial last (6) and a last applicator (12) spaced just apart from each other for clarity reasons. The partial last (6) has an indentation (6a) which aligns with an extrusion at the lower side of the last applicator (12) enabling a correct placement of the last applicator onto the partial last.

[0077] The invention will be illustrated by the following non-limiting example.

[0078] Example

[0079] Reference is also made to the Figures. A knitted shoe upper (1) made from cotton yarns and having an open woven structure and having an opening (2) in its footbed (3) was combined with a last (8). The knitted shoe upper was impregnated with natural rubber and subsequently dried before combining it with the last (8). The last (8) was made by 3D printing of a ABS material. The last (8) was provided with a conduit (13) having an outlet opening (5) which aligns with the footbed opening (2) in the footbed (3) of the knitted upper (1).

[0080] The last (8) was manually placed in the knitted upper (1). making use of a reusable last applicator (12).

[0081] The dried knitted upper (1) provided with the last (8) was placed in a mould (14) such that a cavity (15) remained below the footbed (3) of the knitted upper (1). The mould (14) was obtained by thermoforming a PET film having a thickness of 220 micron. A natural latex further containing sodium silico fluoride and zinc oxide in a typical additive content was added from above through supply conduit (11) and conduit (13) to fill the cavity (15). The mould (14) with the filled cavity (15) and the dried knitted upper (1) was placed in an oven at 90 °C for one hour wherein the natural latex cured. After this hour the mould (14) with the filled cavity (15) and the knitted upper (1) was subjected to a post curing / drying step at 40 °C for another 24 hours. The thus obtained footwear product (19) was removed from the mould (14). The last (8) was removed from the footwear product (19). The rubber sole (17) was found to be very intimately connected with the knitted upper (1), thereby not requiring any further means for securing the sole to the knitted upper.

Claims

CLAIMS1. A process to manufacture a footwear product comprising a shoe upper connected to a sole or midsole wherein the process comprises the following steps(a) placing a last having a conduit with an inlet opening and an outlet opening in a shoe upper having a foot bed provided with a footbed opening thereby covering the foot bed with the last and wherein the outlet opening of the conduit aligns with the footbed opening of the shoe upper,(b) placing the shoe upper with the last as obtained in step (a) in or onto a mould made of a thermoformed plastic film such that a cavity remains below the footbed of the shoe upper,(c) adding a curable liquid from above through the conduit of the last and via the aligned opening of the footbed opening of the shoe upper to fill the cavity,(d) curing the curable liquid to obtain a sole or midsole as attached to the footbed of the shoe upper,(e) removing the shoe upper from the mould, and wherein step (b) and (c) are performed in a linear production line comprising a sequence of a thermoforming station, a placing station and a filing station and wherein the following steps are performed:(i) making the mould in the thermoforming station,(ii) performing step (b) by placing the shoe upper in or onto the mould in the placing station and(iii) performing step (c) in the filling station and wherein the moulds of steps (i)-(iii) are the moulds made by thermoforming and are interconnected moulds which intermittently move from the thermoforming station to the filing station.

2. The process according to claim 1, wherein the shoe upper is a knitted sock.

3. The process according to any one of claims 1-2, wherein the curable liquid is a free flowing curable liquid and wherein in step (c) and (d) the pressure in the cavity is equal to the ambient pressure.

4. The process according to claim 3, wherein in step (b) the shoe upper is positioned slightly above the mould leaving a gap between the mould and the shoe upper.

5. The process according to claim 4, wherein the width of the gap is between 1 and 10 mm.

6. The process according to any one of claims 3-5, wherein the free flowing curable liquid is a curable poly urethane, a curable silicon, a curable synthetic rubber or a curable natural rubber.

7. The process according to claim 6, wherein the curable liquid is a natural rubber latex.

8. The process according to claim 7, wherein step (d) is performed at a temperature of between 30 and 60 °C for a period of between 1 and 3 hours.

9. The process according to any one of claims 7-8, wherein after performing step (e) a drying and vulcanization step (f) is performed wherein the footwear product is dried at a temperature of between 40 and 80 °C for a period of between 8 and 12 hours followed by a vulcanization at a temperature above 80 °C for a period of between 1 and 3 hours.

10. The process according to any one of claims 1-6, wherein the last is a metal part, a wooden part, a 3D printed part or a thermoformed part.

11. The process according to claim 10, wherein the last is a partial last which partial last is made of a thermoformed plastic film and wherein in step (a) the last is placed in the shoe upper making use of a reusable last applicator, wherein the reusable last applicator can releasably connect to the partial last made of a thermoformed plastic film to form a combined object which combined object is placed in the shoe upper in step (a) and wherein after the combined object is placed in the shoe upper the reusable last applicator is disconnected from the partial last made of a thermoformed plastic film and removed from the shoe upper before step (c) is performed.

12. The process according to any one of claims 1-11, wherein the mould in step (b) is made of a thermoformed PET plastic film.

13. Process according to any one of claims 1-12, wherein in the linear production line further comprises a cutting station after the filing station, wherein in the cutting station the interconnected moulds obtained in step (iii) are cut into sections prior to performing step (d) or at the start of performing step (d).

14. Process according to claim 13, wherein steps (i)-(iii) for a single mould is performed in a time period of between 10 and 30 seconds.

15. Process according to any one of claims 1-13, wherein the last is removed from the shoe upper prior, during or after step (e) and reused in a step (a) of this process to manufacture a next footwear product.

16. Process to make a footwear product comprising a shoe upper connected to a sole or midsole wherein the process comprises the following steps(aa) placing a last having a conduit with an inlet opening and an outlet opening in a shoe upper having a foot bed provided with a footbed opening thereby covering the foot bed with the last and wherein the outlet opening of the conduit aligns with the footbed opening of the shoe upper,(bb) placing the shoe upper with the last as obtained in step (aa) in or onto a used plastic mould as obtained in step (e) of a process according to any one of claims 1-15 such that a cavity remains below the footbed of the shoe upper,(cc) adding a curable liquid from above through the conduit of the last and via the aligned opening of the footbed opening of the shoe upper to fill the cavity,(dd) curing the curable liquid to obtain a sole or midsole as attached to the footbed of the shoe upper, and(ee) removing the shoe upper from the used plastic mould.

17. Process according to claim 16, wherein the step (bb) and (cc) are performed in a linear production line comprising a placing station and a filing station and wherein the following steps are performed:(Aii) performing step (bb) by placing the shoe upper in or onto the plastic mould in the placing station and(Aiii) performing step (cc) in the filling station.

18. Process to make a footwear product comprising a shoe upper connected to a sole or midsole wherein the process comprises the following steps(aaa) placing a last having a conduit with an inlet opening and an outlet opening in a shoe upper having a foot bed provided with a footbed opening thereby covering the foot bed with the last and wherein the outlet opening of the conduit aligns with the footbed opening of the shoe upper,(bbb) placing the shoe upper with the last as obtained in step (aaa) in or onto the a plastic mould made of a thermoformed plastic film such that a cavity remains below the footbed of the shoe upper,(ccc) adding a curable liquid from above through the conduit of the last and via the aligned opening of the footbed opening of the shoe upper to fill the cavity,(ddd) curing the curable liquid to obtain a sole or midsole as attached to the footbed of the shoe upper, and(eee) removing the shoe upper from the plastic mould.

19. Process according to claim 18, wherein the process is performed making use of two separate linear production lines X and Y, wherein linear production line X comprises a thermoforming station and a cutting station and linear production line Y comprises comprising a placing station and a filing station and wherein the following steps are performed:(Bi) making the plastic mould in the thermoforming station of linear production line X to obtain interconnected thermoformed moulds and cutting the interconnected thermoformed moulds in the cutting station of the linear production line X to obtain single or groups of plastic moulds,(Bii) performing step (bbb) by placing the shoe upper in or onto the plastic mould obtained in step (Bi) in the placing station of the linear production line Y and (Biii) performing step (ccc) in the filling station of linear production line Y.

20. The process according to any one of claims 16-19, wherein the shoe upper is a knitted sock.

21. The process according to any one of claims 16-20, wherein the curable liquid is a free flowing curable liquid and wherein in step (cc) and (dd) or (ccc) and (ddd) the pressure in the cavity is equal to the ambient pressure.

22. The process according to claim 21, wherein in step (bb) or (bbb) the shoe upper is positioned slightly above the mould leaving a gap between the mould and the shoe upper.

23. The process according to claim 22, wherein the width of the gap is between 1 and 10 mm.

24. The process according to any one of claims 21-23, wherein the free flowing curable liquid is a curable poly urethane, a curable silicon, a curable synthetic rubber or a curable natural rubber.

25. The process according to claim 24, wherein the curable liquid is a natural rubber latex.

26. The process according to claim 25, wherein step (d) is performed at a temperature of between ambient and 60 °C for a period of between 1 and 3 hours.

27. The process according to any one of claims 25-26, wherein after performing step (ee) or (eee) a drying and vulcanization step (ff) or (fff) is performed wherein the footwear product is dried at a temperature of between 40 and 80 °C for a period of between 8 and 12 hours followed by a vulcanization at a temperature above 80 °C for a period of between 1 and 3 hours.

28. The process according to any one of claims 16-27, wherein the last is a metal part, a wooden part, a 3D printed part or a thermoformed part.

29. The process according to claim 28, wherein the last is a partial last which partial last is made of a thermoformed plastic film and wherein in step (a) the last is placed in the shoe upper making use of a reusable last applicator, wherein the reusable last applicator can releasably connect to the partial last made of a thermoformed plastic film to form a combined object which combined object is placed in the shoe upper in step (aa) or (aaa) andwherein after the combined object is placed in the shoe upper the reusable last applicator is disconnected from the partial last made of a thermoformed plastic film and removed from the shoe upper before step (cc) or (ccc) is performed.

30. The process according to any one of claims 16-29, wherein the mould in step (bb) or (bbb) is made of a thermoformed PET plastic film.

31. Process according to any one of claims 16-30, wherein steps (Aii)-(Aiii) or (Bi)-(Biii) for a single mould is performed in a time period of between 10 and 30 seconds.

32. Process according to any one of claims 16-31, wherein the last is removed from the shoe upper prior, during or after step (ee) or (eee) and reused in a step (aa) or (aaa) of this process to manufacture a next footwear product.

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