GB2321873A

GB2321873A - Joining of flexible materials

Info

Publication number: GB2321873A
Application number: GB9702325A
Authority: GB
Inventors: Kenneth Hillier; John Michael Hilton; Michael Troughton
Original assignee: Caligen Foam Ltd
Current assignee: Caligen Foam Ltd
Priority date: 1997-02-05
Filing date: 1997-02-05
Publication date: 1998-08-12
Also published as: GB9702325D0

Abstract

A method of butt jointing flexible materials and particularly polyurethane foam comprises moving a heat source 15 past at least one of the surfaces to be joined to bring the surface into a melted condition and bringing the surfaces into contact with one another behind heat source 15 while the heated surface remains sufficiently melted to cause the surfaces to adhere to one another. The surfaces are preferably arranged to return into contact with one another due to the inherent resilience of the material. Preferably heating is effected by passing a heated bar or wire between the surfaces at a temperature between 400‹C and 600‹C and moving at a speed of 20 to 50 cms per minute. The unheated surfaces may be separated by a separating guide bar movable ahead of and at the same speed as the heat source.

Description

TONING OF FLEXIBLE MATERIALS This invention relates to a method and apparatus for joining of flexible materials and particularly, but not exclusively, for joining foamed plastics materials.

Foamed plastics materials such as polyurethane foam are produced in blocks or rolls of substantial dimensions. A typical block of foam may be 60 metres long, 1.8 metres wide and 0.8 metres high. Such blocks require to be converted into more handleable form for sale to customers and subsequent use.

One known method of converting foam blocks to sheet form is known as loop slitting. This is carried out by forming the block into a loop by joining its ends. The loop is then mounted on a slitting machine and rotated against a knife blade which slits or peels the surface from the rotating loop to form a continuous sheet of foam which is formed into one or more rolls.

Polyurethane foam sheets produced in this way are used for a variety of purposes and are commonly laminated to other materials to form a composite structure. The foam is frequently laminated to a textile material and used as a furnishing fabric or for the production of headliners for the interior of vehicles. For this purpose the foam is commonly attached to the fabric by flame lamination, a technique involving heating of the surface of the foam and bringing it into contact with the fabric to which it then adheres upon cooling. However during the flame lamination process, the foam burns away to a greater extent than the adhesive used to join the ends of the block prior to slitting, with the result that a visible line appears at regular intervals along the laminated material where the ends of the block were joined. This is often aesthetically unacceptable with the result that sections of the laminated material have to be discarded.

It is an object of the present invention to provide an alternative means of joining the ends of a foam block which will not result in 9 visible joint line after flame lamination. However the invention is also applicable to the joining of other flexible materials.

According to one aspect of the invention there is provided a method of butt jointing flexible materials comprising moving a heat source past at least one of the surfaces to be joined to bring same into a melted condition and bringing the surfaces into contact with one another behind the heat source while the heated surface remains sufficiently melted to cause the surfaces to adhere to one another.

Preferably the surfaces are arranged to return into contact with one another due to the inherent resilience of the material.

The unheated surfaces may initially be in contact with one another, the method including separating the surfaces prior to introduction of said heat source.

Separation of the unheated surfaces may be effected by the heat source itself or by separating means movable ahead of and at the same speed as the heat source.

The method may comprise heating only one of the surfaces to be joined but preferably both surfaces are heated.

Preferably heating is effected by direct contact between the surface to be heated and a heated bar or wire. Alternatively heating may be effected by an infra red heater or by gas heating means.

Where the material comprises polyurethane foam the temperature of the heated surface may be raised to between 200or and 1100 C and preferably to between 400"C and 600"C. The speed of movement of the heat source is preferably between 10 and 500 cms per minute and more preferably between 20 and 50 cms per minute. The heat source may be moved at a uniform or variable speed. Advantageously the power of the heat source is increased as the heat source moves through the foam to counteract the cooling effect of the foam and maintain the desired temperature at the surface of the foam throughout the joining process.

Alternatively the speed of movement of the heat source may be reduced as it moves through the foam.

The invention also provides apparatus for use in the butt jointing of flexible materials comprising heating means and means for moving the heating means across at least one of the surfaces to be joined to bring the surface to a melted condition, the apparatus being so constructed as to permit the surfaces to be joined to come into contact with one another behind the heating means while the heated surface or surfaces remain in a melted condition.

Preferably the surfaces to be joined are initially in contact with one another, the apparatus including means for moving the surfaces apart ahead of said heating means.

The heating means preferably comprises a heated bar or wire adapted to be moved past the surfaces to be joined in contact with one or both of them.

Preferably the apparatus includes an unheated bar adapted to move the surfaces apart and a heated wire adapted to move past and in contact with at least one of the surfaces behind and at the same speed as the unheated bar.

The unheated bar may be arranged to extend around one side of the heated wire whereby to shield one of the surfaces from the wire while permitting contact between the wire and the other surface.

In the case of polyurethane foam the heating means may be heated to a temperature between 200or and 1 1000C and preferably between 260or and 4000 C. Preferably said means for moving the heating means is adapted to move it past the surfaces to be joined at a speed of between 20 and 50 cms per minute.

Preferably the heating means is supplied with heat from a heat source disposed externally of the foam. Alternatively the heating means may comprise an infra red heater or gas heater adapted to be moved through the foam so as to move past and direct heat on to one or both of the surfaces to be joined.

Where the heating means is a heated wire, means is preferably provided to maintain the wire under tension during movement between said surfaces.

The invention also provides butt jointed flexible material produced by the method or apparatus aforesaid.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Fig. 1 is a side elevation of a loop slitting machine for polyurethane foam; Figs. 2 and 3 show one form of heating means at different stages of operation; Fig. 4 shows an alternative form of heating means at an intermediate stage of the joining process; Figs. 5 and 6 show modifications incorporating a separate guide bar and heating means; and Fig. 7 shows a further modification using alternative heating means.

Referring to the drawings, Fig. 1 shows a loop slitter comprising a series of rollers 10 which serve to support and guide a loop 11 of polyurethane foam and to drive same in the direction of the arrow 12. A knife 13 is positioned adjacent the inner surface of the loop and peels a thin layer of foam from the surface of the loop as the latter moves past the knife.

The peeled foam is drawn clear of the surface of the loop and fonned into a roll 14 which may subsequently be removed for sale or further processings.

The loop 11 of polyurethane foam is produced from a long block of rectangular cross-section the ends of which are brought into contact with one another and joined together. The present invention is concerned with the production of the join between the adjacent ends of the block.

Figs. 2 and 3 show a first form of apparatus for producing a join between the abutting ends 11A and 1 1B of the foam block. In this embodiment a heated rod or wire 15 is moved by means (not shown) between the abutting ends, the rod serving firstly to push the abutting surfaces apart and to apply heat to the separated surfaces, the heated surfaces then moving together behind the rod due to the inherent resilience of the foam material. Heating of the surfaces brings them to a molten condition such that when they move back into contact with one another they adhere together thus forming a join between the ends 1 1A and 11B. Fig. 2 shows the rod 15 at the commencement of movement through the foam at which stage the abutting surfaces have been moved apart at the lower region of the joint area. As the rod moves upwards in the direction of the arrow, the foam is moved apart ahead of the rod and closes together behind it as shown in Fig. 3 where the rod has reached the upper part of its movement.

Fig. 4 shows an alternative form of apparatus in which the heated rod or wire of Figs. 2 and 3 is replaced by a heated bar 17 having a curved relatively wide leading edge 1 7A tapering to a point at its trailing edge 1 7B.

The bar is moved vertically between the abutting surfaces of the foam material in an upward direction in the same manner as the rod 15 of Figs. 2 and 3. The tail portion 1 7B of the bar 17 serves to fill the space between the separated surfaces to minimise contact between the surfaces and the atmosphere and thereby reduce cooling of the surfaces before they move into contact behind the bar. Preferably heat is applied at the tail portion of the bar to provide maximum control of foam temperature in the region where the surfaces move back into contact with one another.

The rod, wire, bar or the like is preferably heated electrically and supported at its opposite ends in a U-shaped frame or carrier which extends partly around the foam block as the rod moves through the foam. Where the heating means comprises a wire, it is preferably maintained under tension by springs, pulleys and weights or other suitable means. The wire or rod may be up to 10 mm in diameter but is preferably between 0.75 mm and 3 mm in diameter.

Figs. 5 and 6 show preferred forms of the invention in which a heated wire 20 and a separate unheated guide bar 21 are provided. The wire and bar are linked together externally of the foam and adapted to be moved through the joint area in the same direction and at the same speed. The bar 21 serves to separate the adjacent surfaces of the foam ahead of the wire 20 which then heats the separated surfaces, the heated surfaces moving back into contact with one another behind the wire because of the inherent resilience of the foam material. The guide bar 21 serves primarily to separate the butting ends of the foam at the point of entry so that they do not require to be separated by the wire itself. This minimises the tendency of the wire to cut into the foam surfaces by separating the surfaces ahead of the wire. Moreover heat is applied to the foam surfaces as they are moving together thereby providing maximum control of the temperature of the foam surfaces as they come into contact with one another behind the wire.

Fig. 6 shows a modification of the arrangement shown in Fig. 5 in which a modified bar 22 is provided. This includes a depending region 23 extending past one side of the wire 20 and thereby holding the foam at that side away from contact with the wire. The wire 20 thus applies heat only to one face of the foam.

Fig. 7 shows an alternative arrangement in which heating is effected by an infra red heat source. In this case the abutting surfaces of the ends lIA and 11B of the foam are moved apart by pairs of rollers 25A and 25B to permit movement of the infra red heat source 26 between the foam surfaces.

As in the case of the previous embodiments the heated surfaces of the foam spring back into contact with one another behind the heat source by virtue of the inherent resilience of the foamed plastics material. In a modification of this arrangement the infra red heating source may be arranged to apply heat to one face of the foam only rather than both faces as shown in Fig. 7.

Production of a satisfactory joint requires precise control of the temperature to which the surface or surfaces of the foam are heated. This in turn requires accurate control of the temperature to which the bar, rod, wire or other heat source is heated and of the speed of movement through the joint area. In tests in relation to polyurethane foam a satisfactory join has been attained using a bar, rod or wire heated to a temperature between 260o and 400"C and moved at a speed between 20 and 50 cms per minute, although it is envisaged temperatures between 200 and 1 1000C and other speeds of movement may be used. The temperature and speed of movement are controlled to produce the minimum degree of melting of the foam surface consistent with production of a satisfactorily strong joint while producing minimum alteration of the physical characteristics of the foam at the joint zone. The heat source may be moved through the joint area by any suitable drive means and in the case of a wire is preferably maintained under tension to avoid flexing as it moves between the foam surfaces.

Various modifications may be made without departing from the invention. For example alternative means of applying heat to the surfaces to be joined may be employed and while in the embodiments described the bar or the like is moved upwardly through the foam, it may be moved downwardly or from side to side. Moreover, while the invention has been described primarily with reference to the joining of polyurethane foam, it may be equally applied to the joining of other flexible materials such as rubber, thermoplastic materials and fibrous materials.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims:

1. A method of butt jointing flexible materials comprising moving a heat source past at least one of the surfaces to be joined to bring same into a melted condition and bringing the surfaces into contact with one another behind the heat source while the heated surface remains sufficiently melted to cause the surfaces to adhere to one another.

2. A method according to claim 1 wherein the surfaces are arranged to return into contact with one another due to the inherent resilience of the material.

3. A method according to claim 1 or 2 wherein the unheated surfaces are initially in contact with one another, the method including separating the surfaces prior to introduction of said heat source.

4. A method according to claim 3 wherein the unheated surfaces are separated by said heat source itself.

5. A method according to claim 3 wherein the unheated surfaces are separated by separating means movable ahead of and at the same speed as said heat source.

6. A method according to any preceding claim wherein both of the surfaces to be joined are heated

7. A method according to any of claims 1 to 5 wherein only one of the surfaces to be joined is heated.

8. A method according to any preceding claim wherein heating is effected by direct contact between the surface to be heated and a heated bar or wire.

9. A method according to any of claims 1 to 7 wherein heating is effected by infra red heating means.

10. A method according to any of claims 1 to 7 wherein heating is effected by gas heating means.

11. A method according to any preceding claim wherein the material comprises polyurethane foam.

12. A method according to claim 11 wherein the temperature of the heated surface or surfaces is raised to between 2000C and 1 1000C.

13. A method according to claim 12 wherein the temperature of the heated surface or surfaces is raised to between 4000C and 6000C.

14. A method according to any of claims 11 to 13 wherein the speed of movement of said heat source is between 10 and 500 centimetres per minute.

15. A method according to claim 14 wherein the speed of movement of said heat source is between 20 and 50 centimetres per minute.

16. A method according to any preceding claim wherein said heat source is moved at a uniform speed.

17. A method according to any of claims 1 to 15 wherein said heat source is moved at a variable speed.

18. A method according to any preceding claim wherein the power of said heat source is increased as the heat source moves through the material to counteract the cooling effect of the material and maintain the desired temperature at the surface of the material throughout the joining process.

19. A method according to any of claims 1 to 17 wherein the speed of movement of said heat source is reduced as it moves through the foam.

20. A method of butt jointing flexible materials substantially as hereinbefore described.

21. Butt jointed flexible material produced by the method according to any preceding claim.

22. Apparatus for use in the butt jointing of flexible materials comprising heating means and means for moving the heating means across at least one of the surfaces to be joined to bring the surface to a melted condition, the apparatus being so constructed as to permit the surfaces to be joined to come into contact with one another behind the heating means while the heated surface or surfaces remain in a melted condition.

23. Apparatus according to claim 22 wherein the surfaces to be joined are initially maintained in contact with one another, the apparatus including means for moving the surfaces apart ahead of said heating means.

24. Apparatus according to claim 22 or 23 wherein said heating means comprises a heated bar.

25. Apparatus according to claim 24 wherein said bar has a relatively wide leading edge and tapers towards its trailing edge.

26. Apparatus according to claim 25 wherein said tapering portion of the bar is adapted to fill the space between the separated surfaces.

27. Apparatus according to claim 25 or 26 wherein the tapered trailing portion of said bar is heated.

28. Apparatus according to claim 22 or 23 wherein said heating means comprises a heated rod.

29. Apparatus according to claim 22 or 23 wherein said heating means comprises a heated wire.

30. Apparatus according to claim 22 or 23 including an unheated bar adapted to move said surfaces apart and a heated wire adapted to move past and in contact with at least one of the surfaces behind and at the same speed as said unheated bar.

31. Apparatus according to claim 30 wherein said unheated bar is arranged to extend around one side of said heated wire whereby to shield one of said surfaces from said wire while permitting contact between the wire and the other surface.

32. Apparatus according to any of claims 28 to 31 wherein said rod or wire has a diameter of up to 10mm.

33. Apparatus according to claim 32 wherein said rod or wire has a diameter between 0.75mm and 3mm.

34. Apparatus according to any of claims 28 to 33 including means to maintain said wire under tension during movement between said surfaces.

35. Apparatus according to any of claims 22 to 34 for use in the butt jointing of polyurethane foam wherein said heating means is heated to a temperature between 2000C and 1 1000C.

36. Apparatus according to claim 35 wherein said heating means is heated to a temperature between 2600C and 4000C.

37. Apparatus according to claim 35 or 36 wherein said means for moving said heating means is adapted to move it past the surfaces to be joined at a speed of between 10 and 500 centimetres per minute.

38. Apparatus according to claim 37 wherein said means for moving said heating means is adapted to move it past the surfaces to be joined at a speed of between 20 and 50 centimetres per minute.

39. Apparatus according to any of claims 22 to 38 wherein said heating means is electrically heated from a source disposed externally of the material.

40. Apparatus according to any of claims 22 to 38 wherein said heating means comprises an infra red heater adapted to be moved through the foam so as to move past and direct heat on to one or both of the surfaces to be joined.

41. Apparatus according to any of claims 22 to 38 wherein said heating means comprises a gas heater adapted to be moved through the foam so as to move past and direct heat on to one or both of the surfaces to be joined.

42. Apparatus for use in the butt jointing of flexible materials substantially as hereinbefore described with reference to Figs. 2 and 3 of the accompanying drawings.

43. Apparatus for use in the butt jointing of flexible materials substantially as hereinbefore described with reference to Fig. 4 of the accompanying drawings.

44. Apparatus for use in the butt jointing of flexible materials substantially as hereinbefore described with reference to Fig. 5 of the accompanying drawings.

45. Apparatus for use in the butt jointing of flexible materials substantially as hereinbefore described with reference to Fig. 6 of the accompanying drawings.

46. Apparatus for use in the butt jointing of flexible materials substantially as hereinbefore described with reference to Fig. 7 of the accompanying drawings.

47. Butt jointed flexible material produced by the apparatus according to any of claims 22 to 45.

48. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.