METHOD AND MACHINE FOR BONDING A FLEXIBLE COATING TO A SUPPORT USING ELECTROMAGNETIC WAVES AND LINING PRODUCED IN THIS WAY

Abstract

A machine (1) and a method for thermobonding using an emission of electromagnetic waves (13), for example microwaves, to activate one or a plurality of adhesive layers located between a support and one or a plurality of layers of flexible covering, through a bed of particles (4) fluidized by a humidified gas. A multi-layer upholstery item including at least one non-permeable layer and produced in a single operation is also described.

Claims

1. Machine (1) for the thermobonding of a flexible covering (2) to a support (11), of the type comprising: a housing (3) for a bed of particles (4) fluidised by a flow of gas, comprising a gas distributer (6), a diffusion grating (7), a bed of particles (4) and a flexible cover sheet (8), a gas supply system (25, 27), a compression member (10) suitable for pressing the support onto the bed of particles, wherein the gas supply system comprises means (26) for supplying a gas flow having a relative level of humidity of between 70% and 100%, the housing comprises at least one emitter (12) of electromagnetic waves (13) placed so that the waves are oriented in the direction of the compression member.

2. Machine according to claim 1, wherein each wave emitter (12) has an electromagnetic wave generator (14), a waveguide (15) and an antenna (16), said antenna being placed under the bed of particles (4) and being suitable for diffusing the electromagnetic waves (13) through a solid angle (17) centred on the antenna and at an angle suitable for intercepting the support (11).

3. Machine according to claim 1, wherein the housing (3) is enclosed in a metal casing (18) suitable for containing the electromagnetic waves within the casing.

4. Machine according to claim 3, wherein the casing (18) comprises a door (19) suitable for permitting the introduction of the flexible covering and of the support to the inside of the housing.

5. Machine according to claim 3, further comprising at least one wave stirrer (31) inside the casing (18) to distribute the electromagnetic waves (13).

6. Method for thermobonding a flexible covering (2) onto a support (11), of the type using a machine (1) according to claim 1, using a compression member (10) able to press the support onto a bed of particles (4) fluidised by a flow of gas generated by a system (25, 27) for supplying gas into a housing (3) comprising a gas distributer (6), a diffusion grating (7), a bed of particles (4) and a flexible cover sheet (8), the method comprising: stacking at least the covering, an adhesive layer (20) and the support in this order on the cover sheet, using a flow of wet gas to fluidise the bed of particles, applying the compression member onto the support in order to press the support onto the covering, modifying the supply of gas so as to consolidate the bed of particles, triggering an emitter (12) of electromagnetic waves (13) so as to heat at least the adhesive layer, maintaining the emission of waves for a predetermined time suitable for activating the adhesive layer, stopping the emission of waves, raising the compression member and discharging the covered support.

7. Method according to claim 6, wherein the humidity of the gas is used to wet the adhesive layer (20) in order to render it reactive to the electromagnetic waves (13).

8. Method according to claim 6, wherein the support (11) used comprises a foam layer (21), an adhesive layer (20) and a shaped plate (21), these items not being assembled, and the assembly of the support is carried out simultaneously with the bonding of the covering (2) to the support.

9. Method according to claim 6, wherein a fire-resistant felt (23) and a second adhesive layer (20) are also interposed between the covering (2) and the support (11).

10. Machine according to claim 2, wherein the housing (3) is enclosed in a metal casing (18) suitable for containing the electromagnetic waves within the casing.

11. Machine according to claim 4, further comprising at least one wave stirrer (31) inside the casing (18) to distribute the electromagnetic waves (13).

12. Method according to claim 7, wherein the support (11) used comprises a foam layer (21), an adhesive layer (20) and a shaped plate (21), these items not being assembled, and the assembly of the support is carried out simultaneously with the bonding of the covering (2) to the support.

13. Method according to claim 7, wherein a fire-resistant felt (23) and a second adhesive layer (20) are also interposed between the covering (2) and the support (11).

14. Method according to claim 8, wherein a fire-resistant felt (23) and a second adhesive layer (20) are also interposed between the covering (2) and the support (11).

Description

[0033] Other aims, features and advantages of the invention will become clear in light of the following description and the attached drawings in which: [0034] FIGS. 1A and 1B are schematic cross-sectional front views of a machine in accordance with the invention, in the loading and working positions respectively, [0035] FIG. 2 is a side view of a machine in accordance with the invention, showing its protective casing and the door thereof, [0036] FIG. 3 is a partial cross-sectional view of an upholstery item in accordance with the invention.

[0037] The machine 1 shown in FIG. 1A has a housing 3, preferably made of metal, in which are arranged, from top to bottom, a flexible cover sheet 8 defining the upper part of a bed of particles 4 formed from glass microbeads 5. This bed of particles 4 rests on a diffusion grating 7 permitting passage of a gas from a space, named a distributor 6, located below the grating 7 into the bed of particles 4 so as to fluidise this bed of particles. The distributor 6 is supplied with gas, preferably air under pressure by a gas supply system comprising a pump 25 connected to a duct 27 opening into the distributor 6.

[0038] According to one important feature of the invention, the gas supply system also comprises a nozzle 26 for spraying water under high pressure, permitting a mist of fine water droplets to be sent into the duct 27. These water droplets instantly vaporise and humidify the air sent by the pump 25. In the same way, the distributor 6 and the bed of particles 4 are supplied with the wet air. Depending on the flow rate of air supplied by the pump 25 and the quantity of water sprayed by the nozzle 26, the relative humidity of the air supplied to the distributor can be regulated, for example, between 70% and 100%.

[0039] The flow rate of air of the pump 25 can also be regulated, for example, between a full flow rate of the order of 10 m.sup.3 per minute and a reduced flow rate of the order of 2 m.sup.3 per minute or even a zero flow rate. When the bed of particles 4 is supplied by a full flow rate of wet air it behaves as a fluid, preferably as a muddy fluid having a viscosity of the order of 2 to 10 Pa.Math.s. When the bed of particles is supplied at a reduced flow rate or when it is not supplied, the bed of particles solidifies and holds a shape imparted to it in the fluid state, as shown in FIG. 1B.

[0040] Above the sheet 8 covering the bed of particles 4, the machine has a compression member 10, in this case a cylinder suitable for pressing a support 11 onto the bed of particles. The support 11 forms, for example, the seat part or the backrest of a seat to be covered with a flexible covering made of fabric, leather or imitation leather, etc.

[0041] The machine 1 also comprises, in its housing 3, at least one emitter 12 of electromagnetic waves 13. In the example shown in FIG. 1, the emitter 12 has a wave generator, for example, a magnetron 14 to which is/are connected one or more waveguides 15 carrying the electromagnetic waves to one or more antennas 16, for example, horn-type antennas. The antennas 16 are placed in the distributor 6 and oriented so that the electromagnetic waves are oriented towards the compression member 10, and more particularly so that the electromagnetic waves 13 are diffused through a solid angle 17 centred on each antenna and being at an angle suitable for intercepting the support 11. The electromagnetic waves 13 thus emitted have a wavelength between 1 GHz and 300 GHz, in the spectrum generally called the microwave spectrum, and more particularly in a band of 2 to 10 GHz, suitable for heating the water molecules and a power between 800 W and 4 KW depending on the exact usage (materials to be bonded, dimensions of the support etc.) of the machine.

[0042] The machine 1 is completed by a casing 18 made of conductive material and enclosing the internal space of the machine so as to confine the electromagnetic waves within the machine and to ensure the protection of people using or moving around the machine. The casing 18 can consist of an enclosure made from metal sheets closing the housing 3 which is also made of metal, the assembly being earthed to form a Faraday cage or, as shown in FIG. 2, by a casing 18 formed of a conductive mesh 28 with a mesh size suitable for blocking the electromagnetic waves used, for example, a mesh size of the order of a millimetre for the frequency range of 2 to 10 GHz. A door 19, also made of mesh in the same way and mounted in a sliding manner (for example a door which can be raised and lowered, named a guillotine type door), permits the operator to access the inside of the machine to place the various elements to be bonded onto the sheet 8 of the bed of particles 4 and/or onto the compression member 10. The runners of the door 19 are suitablefor example, by using a system of deflectors, named quarter-wave deflectorsfor avoiding leakage of electromagnetic waves when the door is closed. Bolts and safety switches are also installed on the door 19 and/or on the casing 18 to interrupt any emission of electromagnetic waves if the door is not closed correctly. When cables or ducts such as the duct 27 must pass through the housing 3 or the casing 18, suitable feedthroughs 29 are used to avoid wave leakage.

[0043] One or more wave stirrers 31 can also be installed inside the casing 18 to improve distribution of the electromagnetic weaves 13 within the casing 18.

[0044] In the example shown in FIG. 2, the electromagnetic wave emitter is simply produced by a single magnetron 14 placed in the centre of the housing and comprising an antenna 16 directed towards the support mounted on the compression member. Other embodiment variations of the electromagnetic wave emitter(s) can be envisaged depending on the features of the machine to be produced, such as the use of a plurality of magnetrons of average power (500 W-1 KW) or a high-power magnetron (1 KW-4 KW) coupled to a plurality of antennas, for example four antennas placed at the four corners of the distributor 6 etc.

[0045] Reference is made to FIGS. 1A, 1B and 3 to describe the bonding method permitting a simple upholstery item (not shown) or a complex upholstery item 30 as shown in FIG. 3 to be obtained. In this method, the operator opens the door 19 of the machine 1 and places onto the sheet 8 of the bed of particles 4 a first covering 2, for example a piece of fabric and more particularly a piece of coated fabric or leather as shown in FIG. 1A. At this stage, the wet gas supply system of the machine operates at a reduced flow rate and the wet air passes through the bed of particles, passes around the covering 2 and deposits moisture on the exposed face thereof. The covering 2 may have previously been covered with an adhesive layer 20 at an adjoining preparation station or the adhesive layer is deposited at the time of loading of the machine, for example in the form of a dry film pre-cut to the size of the covering 2. The flow of wet air prevailing in the internal work space of the machine is sufficient to load the adhesive layer 20 with moisture.

[0046] In the simplest embodiment of the method in which a simple upholstery item with a single covering is produced, the operator then places the support 11 formed by a shaped plate 22 on which a foam layer 21 has previously been bonded above the covering 2 and the adhesive layer 20. Alternatively, the operator can place the support 11 at the end of the compression member 10. By means of a control panel (not shown) the full flow rate of the wet gas flow is activated and the descent of the compression member 10 is controlled so as to press the support 11 onto the covering 2 covered with the adhesive layer 20. It should be noted that during this descent, the foam layer 21 is also loaded with moisture on its outer face. The support 11, the covering 2 and the adhesive layer 20 disposed therebetween are pressed into the bed of particles 4, then in the fluid state, so that the covering 2 matches the shape of the support 11 as shown in FIG. 1B. The supply of gas is then modified so as to return to the reduced rate or, alternatively, the flow of gas is shut off so as to solidify the bed of particles 4. The force applied by the compression member 10 is preferably increased so as to cause the foam layer 21 on the covering 2 and the adhesive layer 20 to be crushed.

[0047] The assembly of the pieces being thus immobilised, the operator closes the door 19 of the machine, which triggers the electromagnetic wave emitter. The electromagnetic waves 13 pass through the bed of particles 4, the covering 2 and the adhesive layer 20 which they heat by agitation of the water molecules present in or on the adhesive layer. An emission of some tens of seconds will suffice to cause the adhesive to reach its melting point and bond the covering 2 to the foam layer 21. After this time, which can be programmed by a timer, the emission of electromagnetic waves is stopped and the adhesive cools very rapidly. In fact, it has been observed that although the bed of particles is loaded with moisture, it is actually heated to a low degree in relation to its mass and it contributes to the cooling of the adhesive layer when the electromagnetic waves stop heating it. It has been possible to observe that this phenomenon makes it possible to shorten the bonding cycle times compared to a bed fluidised by hot air which requires significant waiting and cooling time before the adhesive is in a state in which it can be handled.

[0048] Once the adhesive has cooled sufficiently to be able to be handled, which is almost instantaneous, the operator opens the door 19, which causes the compression member to rise and discharges the covered support. The compression member 10 can optionally be kept in the low position while the operator carries out some supplementary operations such as pulling on an encircling cover cord or band in a hem previously provided on the periphery of the covering so as to fold back the free edges of the covering towards the centre of the support and to fix the two ends of the cord by bonding or stapling. Once these supplementary operations have been carried out, the compression member 10 rises and the covered support can be discharged.

[0049] The inventors have observed that, in contrast to the hot air machines where the circulation of the air in the various layers and the conduction thus caused, which permit the adhesive to be activated, in a machine in accordance with the invention, the electromagnetic waves are not stopped by an impermeable covering and pass through the entire thickness of the stack of the various layers. It has thus proved to be the case that this method makes it possible to effect multi-layer bonding in a single operation, even if one of the layers is non-permeable to air.

[0050] The method can thus be used to produce a complex upholstery item 30 as shown in FIG. 3. In this case, in the step of loading the machine, the operator places onto the bed of particles the covering 2 which will be on the outside of the upholstery item, the adhesive layer 20, an optional fire-resistant felt 23 (or any other layer of flexible material enabling a technical function to be provided, for example an impermeable film), a second adhesive layer 20, the foam layer 21, a third adhesive layer 20 then the shaped plate 22 forming the skeleton of the upholstery item. The various layers are thus stacked one on top of another then the compression member is lowered so as to exert pressure on the plate 22. In the same way as above, the flow of wet gas is reduced or interrupted to solidify the bed of particles, the door 19 is closed and the emission of electromagnetic waves is activated. Since the electromagnetic waves 13 are not stopped by the various layers of the upholstery item, all the adhesive layers 20, 20 and 20 are activated simultaneously. In the same way as for the simple bonding described above, the interruption of the emission of waves causes almost instantaneous cooling of the assembly of layers and the upholstery item 30 thus produced can be handled almost instantaneously. It then suffices to open the door 19, raise the compression member and discharge an upholstery item produced in a single operation.

[0051] Of course, this description is given merely by way of illustrative example and the person skilled in the art will be able to make numerous modifications thereto without departing from the scope of the invention, such as, for example, arranging the machine 1 so as to place the cylinder on the outside of the casing 18 as long as an appropriate wave leakage-preventing feedthrough is placed around the cylinder rod.