Process for thermo-adhesive bonding of semi-finished products

Abstract

A process for thermo-adhesive bonding of semi-finished products includes preparing an inner sock, an outer sock and an impermeable membrane provided with a thermo-adhesive disposed on an inner surface and/or an outer surface of the membrane; fitting the inner sock onto a rigid reference shape; fitting the membrane over the inner sock; fitting the outer sock over the membrane; heating the outer sock, the membrane and the inner sock arranged on the rigid reference shape in an oven until at least partial melting of the thermo-adhesive; cooling the outer sock, the membrane and the inner sock arranged on the rigid reference shape until cross-linking of the thermo-adhesive and stable bonding of the membrane to the outer sock and/or the inner sock. Also, exerting a substantially uniform pressure on the outer sock, the membrane and the inner sock disposed on the rigid reference shape during cooling, so as to compact them.

Claims

1. Process for thermo-adhesive bonding of semi-finished products, comprising: preparing at least one inner sock; preparing at least one outer sock; preparing at least one membrane with a thermo-adhesive placed on an inner surface and/or on an outer surface of said membrane; fitting the inner sock on a rigid reference shape; fitting the membrane over the rigid reference shape and over the inner sock; fitting the outer sock over the rigid reference shape and over the membrane; heating the outer sock, the membrane and the inner sock arranged on the rigid reference shape until at least partial melting of the thermo-adhesive is determined; and cooling the outer sock, the membrane and the inner sock arranged on the rigid reference shape until cross-linking of the thermo-adhesive and a stable union of the membrane with the outer sock and/or the inner sock is determined; wherein, during cooling, it is also provided to exert a substantially uniform pressure on the outer sock, on the membrane and on the inner sock arranged on the rigid reference shape to compact said outer sock, membrane and inner sock.

2. The process of claim 1, wherein exerting the uniform pressure comprises: placing the outer sock, the membrane and the inner sock arranged on the rigid reference shape in a flexible bag and generating a pressure difference between an outside and an inside of the bag so as to compress the bag against the outer sock, the membrane and the inner sock.

3. The process of claim 1, wherein cooling comprises: placing the outer sock, the membrane and the inner sock arranged on the rigid reference shape in an auxiliary casing in turn placed in a rigid casing; wherein the auxiliary casing is impermeable to gases; wherein a first volume is delimited between the rigid casing and the auxiliary casing; wherein a second volume is delimited inside the auxiliary casing; and introducing a gas at a first pressure through an inlet into the first volume and discharging said gas at a second pressure through an outlet from the first volume, wherein the second pressure is lower than the first pressure, in order to generate an expansion and cooling of the gas contained inside the first volume, cooling the auxiliary casing and the outer sock, the membrane and the inner sock arranged on the rigid reference shape.

4. The process of claim 3, wherein the auxiliary casing is a flexible bag; wherein the process comprises: maintaining the first volume at a third pressure equal to the difference between the first pressure and the second pressure; wherein the second volume is at a fourth pressure lower than the third pressure so as to exert said substantially uniform pressure on the outer sock, the membrane and the inner sock arranged on the rigid reference shape.

5. The process of claim 1, wherein heating is performed in an oven.

6. The process of claim 5, wherein heating in the oven the outer sock, the membrane and the inner sock arranged on the rigid reference shape comprises: circulating in the oven a heated fluid comprising steam, wherein the heated fluid comes into direct contact at least with the outer sock.

7. The process of claim 1, wherein the inner sock and the outer sock are made as separate elements.

8. The process of claim 1, wherein the inner sock and the outer sock are made as a single, substantially tubular element, wherein the outer sock and the inner sock are joined to each other at an ankle area already before the inner sock is placed on the rigid reference shape.

9. The process of claim 8, wherein fitting the outer sock on the rigid reference shape and above the membrane comprises: turning the outer sock inside out while the inner sock and the membrane are already on the rigid reference shape in order to place said outer sock over said membrane.

10. The process of claim 1, wherein the inner sock and/or the outer sock are knitted.

11. The process of claim 10, wherein the inner sock and/or the outer sock comprise at least one thermoplastic yarn.

12. The process of claim 11, wherein heating and cooling the outer sock, the membrane and the inner sock arranged on the rigid reference shape causes the at least partial melting and subsequent cross-linking of the at least one thermoplastic yarn and a formation of more rigid and less rigid portions of the inner sock and/or the outer sock.

13. The process of claim 1, wherein the membrane is polyurethane, optionally breathable, optionally elastic.

14. The process of claim 1, wherein the membrane is impermeable.

15. The process of claim 1, wherein the thermo-adhesive is placed in dots on the inner surface and/or on the outer surface of said membrane.

16. The process of claim 4, further comprising: closing the inlet and the outlet to maintain said third pressure in the first volume and keeping on pressing the bag against the outer sock, the membrane and the inner sock arranged on the rigid reference shape.

17. The process of claim 6, wherein the heated fluid comprises overheated air, steam, preferably overheated, or a mixture of overheated air and steam, preferably overheated.

Description

DESCRIPTION OF DRAWINGS

(1) This description will be shown below with reference to the attached drawings, provided for indicative purposes only and, therefore, not limiting, in which:

(2) FIG. 1 illustrates a shoe made through the process according to the present invention;

(3) FIG. 2 illustrates a rigid reference shape employed in the process according to the present invention;

(4) FIG. 3 shows two socks used in an embodiment of the process according to the present invention;

(5) FIGS. 4, 5, 6 and 7 illustrate the rigid reference shape with the socks of FIG. 3 in respective steps of the process of the present invention;

(6) FIG. 8 illustrates the rigid reference shape with the socks placed in an oven according to a further step of the process of the present invention;

(7) FIG. 9 illustrates a cooling device used in the process of the present invention;

(8) FIGS. 10 to 13 illustrate the respective operating steps implemented by the device in FIG. 9.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(9) With reference to FIG. 1, a footwear obtained through the process for thermo-adhesive bonding of semi-finished products according to the present invention has been overall indicated with reference numeral 1. The process according to the invention may also be used to make other articles, such as clothing articles or medical articles or accessories, such as bags or suitcases.

(10) The footwear 1 comprises an upper 2 and a sole 3. As specified above, the upper 2 surrounds the foot and comprises both the upper portion of the footwear 1, which is more exposed and in evidence and covers the foot on the top, and also the lower portion, or insole, intended to remain hidden between the upper and the sole 3 of the footwear 1.

(11) The upper 2 is made from a tubular element comprising an outer sock 4 and an inner sock 5 (FIGS. 3, 4 and 5) and a membrane 6 that is waterproof and breathable (shown in FIG. 5) and, for example, also elastic.

(12) The tubular element is made by weaving, for instance by means of a circular weaving loom, which is of a type known in itself and therefore not described herein.

(13) The tubular element comprises natural and/or synthetic yarns and can also be provided with thermo-plastic yarns, i.e. yarns made of thermoplastic polymers (thermo-melting and/or thermo-shrinking) which have the ability to change their structure at a certain temperature (usually between 60° C. and 180° C.) and therefore to melt once this temperature is reached and to cross-link once cooled. Thermo-plastic yarns may be arranged in different ways and with different densities and percentages during weaving. For example, the percentages of the thermo-plastic yarns are higher at the toe and/or heel and/or insole of the upper 2 and lower elsewhere. The arrangement and/or characteristics of the thermo-plastic yarns allow for different textures and/or stiffnesses in different areas/portions/points of the upper 2.

(14) According to the embodiment illustrated in FIGS. 3-6, the outer sock 4 and the inner sock 5 are mutually joined at, for example, an area intended to be positioned around a user's ankle (collar of the shoe). The inner sock 5 and the outer sock 4 are woven in a single weaving step. At the end of the weaving, the inner sock 5 and the outer sock 4 are mutually joined in said ankle area and consecutively arranged with respect to each other to form a single tubular body provided with two auxiliary openings 7, 8 placed at its opposite ends, as illustrated in FIG. 3.

(15) In accordance with the process of the invention, a rigid reference shape 9 (FIG. 2) is prepared which reproduces in negative the upper 2 to be formed. The rigid reference shape 9 is, for example, made of a plastic material and is such that it can withstand high temperatures and pressures of the process without being damaged and/or deformed. The rigid reference shape 9 substantially reproduces the outline of a foot and is provided, at the ankle, with anchoring elements 10 (schematically shown as holes) for engagement with a support 11, shown in FIG. 8.

(16) In addition, the water-proof and breathable membrane 6 with a shape similar to that of the outer sock 4 is prepared. The waterproof and breathable membrane 6 is, for example, polyurethane. The membrane may also be made of other materials, such as PTFE. A thermo-adhesive is applied to an inner surface and/or an outer surface of said membrane 6, such as a plurality of thermo-adhesive droplets distributed over said surfaces. At room temperature, the thermo-adhesive droplets are solid and the membrane 6 can be manipulated.

(17) The process involves closing, sewing or sealing the auxiliary opening 7 of the inner sock 5 and first fitting on the rigid reference shape 9 said inner sock 5 by passing the rigid reference shape 9 through the auxiliary opening 8 of the outer sock 5 until the tip of the inner sock 5 is brought at a tip of the rigid reference shape 9. The outer sock 4 is left outside the inner sock 5 and hung on said inner sock 5 (as in FIG. 4).

(18) While the inner sock 5 alone is placed on the rigid reference shape 9, the water impermeable and breathable membrane 6 is fitted over the inner sock 5, as shown in FIG. 5.

(19) At this point, the outer sock 4 is turned inside-out and also fitted over the rigid reference shape 9 and over the membrane 6 by passing the rigid reference shape 9 through the auxiliary opening 8 of the outer sock 4. In this configuration (FIG. 6), the membrane 6 is interposed between the inner sock 5 and the outer sock 4 and the thermo-adhesive in droplets (still in a solid state) lies between the inner sock 5 and the membrane 6 and/or between the membrane 6 and the outer sock 4.

(20) The auxiliary opening 8 of the outer sock 4 is closed (e.g. sewn or welded) and the assembly comprising the rigid reference shape 9, the inner sock 5, the membrane 6 and the outer sock 4 (illustrated in FIG. 7) is hooked to the support 11 and inserted into an oven 12. In a variant embodiment, the auxiliary opening 8 of the outer sock 4 is not closed at this stage but later, for example by application of the sole 3 after the heating and cooling described below.

(21) The oven 12, illustrated in FIG. 8, comprises an outer casing 13 and an inner casing 14. The inner casing 14 encloses a containment volume intended to house the assembly. The inner casing 14 and the outer casing 13 enclose a gap 15 between them. The inner casing 14 is also provided with passageways 16 that connect the gap 15 with the containment volume.

(22) A fan 17 is mounted on the outer casing 13 and on the inner casing 14 and has a main mouth facing into the containment volume and radially peripheral outlets opening into the gap 15. The fan 17 is therefore operationally active between the containment volume and the gap 15 to determine circulation of a fluid between said containment volume and the gap 15.

(23) Electrical heating elements 18, schematically shown in FIG. 8, are placed in the gap 15 and appropriately powered and controlled to heat the fluid circulating in the oven 12.

(24) The oven 12 is also provided with nozzles 19 facing into the gap 15 and connected to an overheated water steam generating device, not shown, configured to feed steam into the oven 12 itself. The hot fluid that is circulated through the oven 12 and comes into direct contact with the assembly comprising the rigid reference shape 9, the inner sock 5, the membrane 6 and the outer sock 4 comprises overheated air or steam, preferably overheated, or a mixture of overheated air and steam, preferably overheated.

(25) For instance, the percentage of overheated air in the mixture of overheated air and steam is from 10% to 70%; the temperature of overheated air is from 50° to 300° 0°; the temperature of overheated steam is from 150° to 200° C.°. In this way, the assembly (rigid reference shape 9, inner sock 5, outer sock 4, membrane 6) is brought to a temperature of 50° to 300° C.° for a time of 10 to 300 sec. Heating in the oven 12 results in at least partial melting of the thermo-adhesive droplets and any thermoplastic yarns of the inner sock 5 and/or the outer sock 4.

(26) Next, the assembly is removed from the oven 12 and placed in a cooling device 100 (shown in FIG. 9).

(27) The cooling device 100 comprises a rigid casing 101, for example metallic and possibly insulated, which in the illustrated example has a substantially cup shape. The rigid casing 101 has an upper access opening 102 bounded by an edge and has a flange 103 attached to the edge. A bag 104 is disposed in the rigid casing 101. The bag 104 is closed at the bottom and has its own edge delimiting a respective opening 105. The edge of the bag 104 is interposed and secured between the flange 103 and the edge of the rigid enclosure 101. An inner surface of the rigid casing 101 and an outer surface of the bag delimit between them a first volume 106 which, during operation of the device 100, changes. The bag 104 delimits within itself a second volume 107.

(28) The bag 104 is gas-tight, flexible and elastic, for example made of rubber. In variant embodiments, the bag 104 may also be non-elastic, for example made of plastic or a fabric that has been made impermeable, i.e. made gas impermeable. The bag 104 is configured and sized to hold the assembly comprising the rigid reference shape 9, the inner sock 5, the membrane 6 and the outer sock 4. The bag 104 is part of the device 100 and is preferably usable for a plurality of cooling cycles (i.e., preferably, it is not disposable but is only changed when broken or worn).

(29) A lid 200 is configured to rest against the flange 103 and tight-seal the opening 105 of the bag 104 and the access opening 102. The rigid casing 101, the flange 103, the bag 104 and the lid 200 gas-tightly close the first volume 106 and the second volume 107.

(30) The rigid casing 101 has an inlet 108 configured to allow a gas, such as air, to enter the rigid casing 101 at a first pressure P1. The inlet 108 is, for example, connected to a compressor and/or a pressurized gas tank, not shown, and comprises a pressure regulator 109 configured to regulate the inlet pressure in the rigid casing 101 and to maintain it substantially equal to said first pressure P1. The rigid casing 101 has an outlet 110 configured to allow the gas to exit at a second pressure P2 that is lower than the first pressure P1. The outlet 110 is, for example, connected to a discharge outlet, such as an ambient discharge outlet, and comprises a pressure regulator 111 configured to regulate the pressure exiting the rigid casing 101 and maintain it substantially equal to said second pressure P2.

(31) The inlet 108 and the outlet 110 are in fluid communication with the first volume 106. The first pressure P1 at the inlet is, for example, equal to 4 bar and the second pressure P2 at the outlet is, for example, equal to 2 bar. The rigid casing 101 has an auxiliary outlet 112 disposed on a bottom of the rigid casing 101. The auxiliary outlet 112 may be closed through, for example, a valve, not shown, and is connected to a suction assembly 113, for example of the Venturi type.

(32) An auxiliary inlet 114 (FIG. 10) is also provided through the lid 200, which, when the lid 200 is properly mounted on the flange 103, is communicating with the second volume 107, i.e. with the interior of the bag 106. The auxiliary inlet 114 is also closable via, for example, a valve, not shown. The auxiliary inlet 114 is connected to, for example, a compressor, not illustrated, to allow for the entry of pressurized gas, as will be explained later.

(33) The lid 200 comprises a support 115 to which the rigid reference shape 9, on which the inner sock 5, the membrane 6 and the outer sock 4 are disposed, is constrained or constrainable. The support 115 is configured to be placed, together with the aforementioned assembly, in the second volume 107 when the lid 200 closes the access opening 102 (as visible in FIGS. 11 and 12).

(34) The lid 200 with the support 115 and the assembly (comprising the rigid reference shape 9, the inner sock 5, the membrane 6 and the outer sock 4) is lowered so as to insert said assembly inside the bag 104 and the rigid casing 101, as schematically illustrated in FIG. 10. The lid 200 goes and rests against the flange 103 hermetically gas-tight sealing the first volume 106 and the second volume 107 (FIG. 11).

(35) At this stage, the pressure inside the bag 104, i.e. in the second volume 107, and also the pressure in the first volume 106 are equal to ambient pressure, i.e. about 1 bar.

(36) At this point, suitable control devices control the inlet pressure regulator 109 and the outlet pressure regulator 111 so as to introduce air at the first pressure P1 through the inlet 108 and simultaneously discharge air at the second pressure P2, which is less than the first pressure P1, through the outlet 110. In this way, an expansion and cooling of the air contained within the first volume 106 is generated and thus a cooling of the bag 104 and of the assembly therein. For instance, the air contained within the first volume 106 is brought to a temperature of 5° C.

(37) During this operation, the air contained in the first volume 106 is at a third pressure P3 equal to the difference between the first pressure P1 and the second pressure P2. This third pressure P3 is adjusted to be greater than the pressure inside the bag 104, i.e. of the ambient pressure, which we refer to as the fourth pressure P4. In this way, the bag 104 is pressed evenly against the outer sock 4, the membrane 6 and the inner sock 5 which in turn presses against the respective rigid reference shape 9 (which does not deform).

(38) If the bag 104 is elastic, it adapts to the variation of the second volume 107 and adheres perfectly to the assembly without forming folds. It is also possible that the bag 104 is not elastic but is so thin that the micro-folds it forms when adhering to the assembly still ensure uniform compression of the assembly.

(39) Possible pressure values are shown in Table 1 below.

(40) TABLE-US-00001 TABLE 1 Pressures P1 4 bar P2 2 bar P3 = P1 − P2 2 bar P4 1 bar (Patm) P3 − P4 1 bar

(41) With these values, the outer sock 4, the membrane 6 and the inner sock 5 are pressed with a pressure of about 1 Kg/cm.sup.2.

(42) For example, it may be contemplated to feed air at the first pressure P1 through the inlet 108 and discharge air at the second pressure P2 through the outlet 110 for a cooling time of 40 s. Further, it may be contemplated to close the inlet 108 and the outlet 110 to maintain said third pressure P3 in the first volume 106 and keeping on pressing the bag 104 against outer sock 4, the membrane 6 and the inner sock 5 disposed on the rigid reference shape 9, for example for a dwell time of 40 s. In addition, an air flow rate through the inlet 108 and the outlet 110 may also be adjusted to control cooling. For example, such a flow rate is between 25 L/min and 50 L/min.

(43) Such cooling and compression cause the stable union of the waterproof and breathable membrane 6 to the inner sock 5 and/or the outer sock 4 (thermo-adhesive) and, if present, the controlled cross-linking of the thermo-plastic or thermo-adhesive yarns (thermo-forming) and the stabilization of the multilayered semi-finished product thus obtained.

(44) Once the desired cooling is achieved, the bag 104 is detached from the assembly, for example by canceling the pressure difference P3-P4. For this purpose, the inlet 108 and the outlet 110 may be closed and the auxiliary outlet 112 of the rigid casing 101 may be opened, possibly by drawing air contained in the first volume 106 through the suction assembly 113. In addition, it may be contemplated to feed air at a pressure greater than atmospheric pressure through the auxiliary inlet 114 and directly into the bag 104 (FIG. 12).

(45) At this point, the assembly is extracted from the device 100 (as schematically represented in FIG. 13) and the operator can remove the stabilized multilayered semi-finished product from the rigid reference shape 9. Finally, the sole 3 and any further finishing elements 20, for example with an aesthetic and/or reinforcing function, are applied to the upper 2.

(46) According to an embodiment variant of the process of the present invention, the outer sock 4 and the inner sock 5 are made separately and operated as separate elements. In such an embodiment variant, both the inner sock 5 and the outer sock 4 have only one open end and the other end is closed. The process involves first fitting the inner sock 5 onto the rigid reference shape 9, then fitting the water impermeable and breathable membrane 6 over the inner sock 5 and finally fitting (without turning it inside out) the outer sock 4 onto the rigid reference shape 9 and over the membrane 6.

(47) In this variant embodiment, at the end of cooling and after extraction from the device 100, in addition to applying the sole 3 and any further finishing elements 20, it is envisaged to finish the edge of the ankle by joining together the neck of the outer sock 4 with that of the inner sock 5, for example by heat-sealing or beading.