VAN LEUSDEN, Everardus Johannes Maria (Fazantenkamp 27, CB Maarssen, NL-3607, NL)
ATKINS, Michael Paul Nicholas (Hilltop Cottage, Barton Road, Pulloxhill Bedfordshire MK45 5HP, GB)
| CLAIMS: 1. A moulded plastic tile comprising a plastic tile body having a pair of opposing main faces; at least one laminated top sheet provided on at least one main face of the tile body, the laminated top sheet comprising a backing sheet and an external sheet; wherein the backing sheet is bonded with the material of the tile body at an interface layer, the interface layer being defined between the tile body and the backing sheet during the process of moulding the tile; the interface layer being formed by the materials of the backing sheet and the tile body adjacent layers of which are blended together and set during the moulding process, thereby forming a bond between the materials of the tile body and the backing sheet; and wherein the interface layer forms an integral part of each of the backing sheet and the tile body. 2. A tile of Claim 1 , wherein the backing sheet is made from a plastics material capable of blending and bonding with the material of the tile body during the process of moulding of the tile body. 3. A tile of Claim 2, wherein the backing sheet material is the same as the material of the tile body. 4. A tile of any preceding claim, wherein the external sheet has colour and/or texture, and/or physical and/or chemical properties different from the tile body. 5. A tile of Claim 4, wherein the upper surface of the external sheet comprises a printed pattern. 6. A tile of any preceding claim, wherein the material of the tile body is polyvinyl chloride (PVC). 7. A tile of any preceding claim, wherein the external sheet further comprises an upper protective layer which covers the upper surface of the external sheet for protecting the external sheet from wear. 8. A tile of any preceding claim, wherein the tile comprises interlocking integral members formed around the perimeter of the tile body, the interlocking members being configured to interlock with corresponding interlocking members of another tile for securing the tiles together. 9. A method of making a tile comprising the steps of: providing at least one laminated top sheet comprising a backing sheet and an external sheet; providing a mould for forming a tile, the mould comprising a pair of internal spaced apart opposing moulding faces defining a moulding cavity; applying the laminated sheet to at least one of the opposing moulding faces of the mould so that the backing sheet faces the other opposing moulding face; introducing molten plastic material into the mould cavity for forming a tile body; allowing a layer of the molten material of the tile body to blend with a layer of the material of the backing sheet of the laminated sheet thereby defining an interface layer therebetween; cooling the contents of the mould to set the molten tile body material and the blended materials of the interface layer thereby forming a bond between the materials of the tile body and the backing sheet; whereby the interface layer forms an integral part of each of the backing sheet and the tile body; and extracting the moulded tile from the mould. 10. A method of Claim 9, wherein the molten material is retained in the mould in contact with the backing sheet for a period of time between 20 seconds and 40 seconds, which is sufficient to allow the bonding to finish; whereby the backing sheet does not melt to the same level of liquidity as the molten plastics introduced into the mould, but becomes sufficiently soft in order to blend with the molten material tile body and, upon cooling, to form a bond with the material of the tile body. 11. A method of Claim 9 or Claim 10, wherein the method comprises the step of forming integral interlocking members around the perimeter of the tile body during the process of moulding the tile. 12. A method of any one of Claims 9 to 11 , wherein the method comprises the step of statically electrically charging the laminated top sheet prior to introducing the laminated top sheet into the mould. 13. A method of Claim 12, wherein the moulding face of the mould to which the laminated top sheet is to be applied is statically electrically charged with an opposite charge. 14. A method of Claim 13, wherein the static electric charges provided to the laminated top sheet and to the relevant moulding face are sufficient to attract and hold the laminated top sheet in engagement with the relevant moulding face of the mould cavity. 15. A method of Claim 14, wherein the method further comprises the step of bringing the laminated top sheet into a position in which the external sheet of the laminated top sheet faces the relevant moulding face of the mould and in which the laminated top sheet is positioned substantially parallel to and in register with the moulding face of the mould to which the laminated sheet is to be applied, and at a predetermined distance from that moulding face; and releasing the laminated top sheet whereby the static electric charge force acting between the laminated top sheet and the moulding face is sufficient to attract the laminated top sheet to the moulding face and retain in engagement with the moulding face prior and during the step of introducing the molten tile material into the mould. 16. A method of Claim 15, wherein the predetermined distance is 20mm. 17. A method of any of claims 9 to 16, wherein the method comprises cutting the laminated top sheet of a required size from a larger laminated sheet prior to placing the laminated top sheet in the mould. 18. A method of Claim 17, wherein the larger laminated sheet has a width equal the width of one side of the tile and a length sufficient to allow a plurality of tiles to be cut from the larger sheet. 19. A method of Claim 18, wherein, the larger sheet is wound into a roll and is mounted on a support mechanism of a cutting machine, which comprises a cutting mechanism. 20. A method of Claim 19, wherein a free end of the roll is passed through the cutting mechanism which cuts off sheets of a pre-set length from the roll. 21. A method of Claim 20, wherein the method comprises the step of transferring the laminated top sheet to the mould. 22. A method of any one of Claims 17 to 21 , wherein an automatic robotic arm picks and transfers a cut laminated top sheet to the mould and for applying the laminated top sheet to one of the opposing faces of the mould. 23. A method of Claim 22, wherein the laminated top sheet is picked and held by the robotic arm using vacuum. 24. An apparatus for making a tile as defined in any one of Claims 1 to 8, the apparatus comprising: a mould for forming a tile, the mould comprising a pair of internal spaced apart opposing moulding faces defining a moulding cavity; a picking arm configured to pick up and transfer a laminated top sheet comprising an external sheet and a backing sheet into the moulding cavity before a molten plastic material for forming a tile body is introduced into the moulding cavity, and to cause the external sheet of the laminated top sheet to become attached to one of the opposing moulding faces of the mould; means for introducing a molten plastic material into the moulding cavity; and means for extracting a moulded tile from the mould. 25. An apparatus of Claim 24, wherein the picking arm is configured to pick up a laminated top sheet from a location remote the mould. 26. An apparatus of Claim 25 or Claim 25, wherein the apparatus comprises a cutting machine configured to cut a laminated top sheet of a required size from a larger laminated sheet and a transfer mechanism for transferring a laminated top sheet to a picking location remote the mould. 27. An apparatus of Claim 25 and Claim 26, wherein the picking arm is configured to pick a laminated top sheet from the picking location remote the mould. 28. An apparatus of Claim 26 or Claim 27, wherein the cutting machine is configured to accommodate and comprises a support mechanism to support a larger laminated sheet which has a width equal the width of one side of a tile to be moulded and a length sufficient to allow a plurality of tiles to be cut from the larger sheet, wherein the larger sheet is wound into a roll, and wherein the support mechanism rotatably supports the roll. 29. An apparatus of Claim 28, wherein the cutting machine also comprises a cutting mechanism configured to cut laminated top sheets of pre-set length from the roll. 30. An apparatus of Claim 28 or Claim 29, wherein the cutting machine preferably comprises a set of rollers for drawing a free end of the roll between the support mechanism and the cutting mechanism. 31. An apparatus of any one of Claim 24 to Claim 30, wherein the picking arm comprises a vacuum activated gripping head adapted to pick a laminated top sheet using vacuum. 32. An apparatus of Claim 31 , wherein the picking arm is configured to pick a laminated top sheet by gripping the laminated top sheet at the backing sheet. 33. An apparatus of any one of Claims 24 to Claim 32, wherein the picking arm is an automatic electronically controlled robotic arm. 34. An apparatus of any one of Claims 24 to Claim 33, wherein, the mould is a divided mould comprising a pair of complementary constituent parts, each part comprising one of a pair of opposing moulding faces, which define the moulding cavity when the parts are brought together; wherein the complementary parts are movably arranged with respect to one another so that the parts can be moved apart to allow the laminated top sheet to be inserted in the mould and to allow a moulded tile to be extracted from the mould; and brought together to receive the molten material; and wherein one complementary part is stationary and the other complementary part is movable. 35. An apparatus of Claim 34, wherein the complementary parts are arranged to move with respect to each other in the direction substantially perpendicular the opposing moulding faces of the mould. 36. An apparatus of Claim 34 or Claim 35, wherein the picking arm is configured to move so as to bring the laminated top sheet into a position in which the external sheet of the laminated top sheet faces the relevant moulding face of the mould and in which the laminated top sheet is positioned substantially parallel to and in register with a relevant moulding face and spaced apart from that moulding face in the direction substantially normal to that moulding face to a predetermined distance before the laminate top sheet is brought into contact with that moulding face. 37. An apparatus of Claim 36, wherein in order for the picking arm to position the laminated top sheet parallel to and in register with and normally spaced apart from the moulding face, the complementary parts of the mould are positioned spaced apart sufficiently to allow the picking arm to access the space defined between the spread apart complementary parts. 38. An apparatus of any one of Claim 24 to 37, wherein the apparatus comprises an arrangement for statically electrically charging the laminated top sheet prior to introducing the laminated top sheet into the mould. 39. An apparatus of Claim 38, wherein the apparatus also comprises an arrangement for statically charging with an opposite charge a moulding face of the mould to which the laminated top sheet is to be applied. 40. An apparatus of Claim 39, wherein the static electric charges of the laminated top sheet and the relevant mould face are sufficient to attract and hold the laminated top sheet in engagement with the relevant moulding face of the mould cavity. 41. An apparatus of Claim 39 or Claim 40, wherein when the picking arm takes a position in which the external sheet of the laminated top sheet faces the relevant moulding face and is positioned substantially parallel to and in register with the relevant moulding face of the mould and at a predetermined distance from that moulding face, the picking arm is configured to release the laminated top sheet; wherein the static electric charge force acting between the laminated top sheet and the moulding face is sufficient to attract the laminated top sheet to the moulding face so that the external sheet and the moulding face are in contact substantially across their entire surfaces and to retain the laminated top sheet in engagement with the moulding face prior and during the moulding process of the tile of the invention. 42. An apparatus of Claim 41 , wherein the predetermined distance is 20mm. 43. An apparatus of Claim 34, wherein the complementary parts of the mould are adapted to move together once the laminated top sheet has been applied to the relevant moulding face, so as to close the mould and to form the moulding cavity. 44. An apparatus of Claim 43, wherein the complementary parts are closed under a predetermined pressure to maintain the integrity of the mould cavity during the moulding process. 45. An apparatus of Claim 44, wherein the complementary parts are closed at a pressure of 300 tonnes. 46. An apparatus of any one of Claims 24 to 45, wherein the mould is positioned so that the opposing moulding faces lie in planes oriented substantially perpendicular to the ground. 47. A tile substantially as herein described with reference to and as shown in the accompanying drawings. 48. A method of producing a tile substantially as herein described with reference to the accompanying drawings. 49. An apparatus for producing a tile substantially as herein described with reference to and as shown in the accompanying drawings. |
FIELD OF THE INVENTION
The present invention relates generally to a plastic tile, such as, for example, but not in any way limited thereto, a floor tile, and a method an apparatus of manufacturing such a tile.
BACKGROUND OF THE INVENTION
Plastic tiles, such as PVC tiles, are popular in the domestic and industrial sectors mostly because they are relatively inexpensive, lightweight compared to ceramic or stone tiles, damage- resistant in transportation and are easy to install and to maintain.
Two main methods are typically used for making floor tiles, namely, cutting individual tiles from a larger rolled sheet and moulding.
A decorative pattern is typically applied to a rolled sheet during the process of manufacturing the sheet using a printing press. The use of the printing press makes it possible to apply a virtually unlimited variety of patterns to the rolled sheet. Some of the finishes may have the appearance of natural materials, such as, for example, wood or stone. Other finishes include various graphic patterns. No adhesive backing is usually applied to the rolled sheet, and tiles cutout from the sheet are normally fitted to a floor surface using a separately supplied adhesive. A prior art cut-out plastic tile with a decorated upper surface is shown in Figure 1.
Moulded plastic tiles, such as tile 1 shown in Figure 2, are individually formed and typically have greater thickness than the tiles cut from the rolled sheet. The advantage of moulded tiles resides in that moulding makes it possible to manufacture a plastic tile with integral interlocking fastening members 2, a feature not achievable in cut tiles. The interlocking members 2 allow the moulded plastic tiles to be fitted without the use of an adhesive, thereby simplifying the installation process considerably. Moulded tiles can have different surface textures achieved by different surface finishes on one or both inner sides of the mould. A drawback of moulded plastic tiles is that the appearance (i.e. colour, texture etc.) and physical and chemical properties of the upper surface of moulded plastic tiles are limited to the appearance and the physical and chemical properties of the plastics material from which the tiles are made. Accordingly, the aesthetic appearance of a moulded tile and its other characteristics, such as, wear resistance, fire resistance, reaction to chemicals and other physical aspects of the floor tile are solely dependent upon and are as direct result/consequence of the material used to mould the tile.
In view of the above, it is an object of the present invention is to provide a moulded plastics tile having an upper surface finish not limited to the plastics material used to mould the tile and a corresponding method for making such a tile. SUMMARY OF THE INVENTION
Accordingly, the present invention provides a moulded plastic tile comprising
a plastic tile body having a pair of opposing main faces;
at least one laminated top sheet provided on at least one main face of the tile body, the laminated top sheet comprising a backing sheet and an external sheet;
wherein the backing sheet is bonded with the material of the tile body at an interface layer, the interface layer being defined between the tile body and the backing sheet during the process of moulding the tile; the interface layer being formed by the materials of the backing sheet and the tile body adjacent layers of which are blended together and set during the moulding process, thereby forming a bond between the materials of the tile body and the backing sheet; and
wherein the interface layer forms an integral part of each of the backing sheet and the tile body.
Preferably, the backing sheet is made from a plastics material capable of blending and bonding with the material of the tile body during the process of moulding of the tile body. Ideally, the backing sheet material is the same as the material of the tile body.
Preferably, the material of the tile body is polyvinyl chloride (PVC).
In a preferred embodiment, the external sheet has colour and/or texture, and/or physical and/or chemical properties different from the tile body. Ideally, the upper surface of the external sheet comprises a printed pattern.
Preferably, the external sheet further comprises an upper protective layer which covers the upper surface of the external sheet for protecting the external sheet from wear. Ideally, the upper protective layer is transparent or translucent. Ideally, the protective layer is laminated with the external sheet. Preferably, the material of the protective layer is the same as the material of the tile body. Preferably, the material of the protective layer is PVC.
The laminated top sheet is manufactured separately, prior to making a tile of the invention. Most preferably, the material of the external sheet is selected such that it is capable of maintaining its integrity during the process of moulding of the tile.
Advantageously, the tile comprises interlocking integral members formed around the perimeter of the tile body, the interlocking members being configured to interlock with corresponding interlocking members of another tile for securing the tiles together.
Preferably, the thickness of the backing sheet is 0.3mm, the thickness of the external sheet without the protective layer is 0.2mm and the thickness of the protective layer is 0.2mm. It will be appreciated that the invention is not limited to the specific values of the material thickness of these layers.
The present invention also provides a method of making a tile comprising the steps of: providing at least one laminated top sheet comprising a backing sheet and an external sheet; providing a mould for forming a tile, the mould comprising a pair of internal spaced apart opposing moulding faces defining a moulding cavity;
applying the laminated sheet to at least one of the opposing moulding faces of the mould so that the backing sheet faces the other opposing moulding face;
introducing molten plastic material into the mould cavity for forming a tile body;
allowing a layer of the molten material of the tile body to blend with a layer of the material of the backing sheet of the laminated sheet thereby defining an interface layer therebetween;
cooling the contents of the mould to set the molten tile body material and the blended materials of the interface layer thereby forming a bond between the materials of the tile body and the backing sheet; whereby the interface layer forms an integral part of each of the backing sheet and the tile body; and
extracting the moulded tile from the mould.
Preferably, the molten material is retained in the mould in contact with the backing sheet for a period of time between 20 seconds and 40 seconds, which is sufficient to allow the bonding to finish.
In a most preferred arrangement, the method comprises the step of forming integral interlocking members around the perimeter of the tile body during the process of moulding the tile.
Conveniently, the method comprises cutting the laminated top sheet of a required size from a larger laminated sheet prior to placing the laminated top sheet in the mould.
Preferably, the larger laminated sheet has a width equal the width of one side of the tile and a length sufficient to allow a plurality of tiles to be cut from the larger sheet. Ideally, the larger sheet is wound into a roll and is mounted on a support mechanism of a cutting machine, which comprises a cutting mechanism. A free end of the roll is passed through the cutting mechanism which cuts off sheets of a pre-set length from the roll.
Ideally, the method comprises the step of transferring the laminated top sheet to the mould.
Preferably, an automatic robotic arm is provided for picking and transferring a cut laminated top sheet to the mould and for applying the laminated top sheet to one of the opposing faces of the mould. Ideally, the laminated top sheet is picked and held by the robotic arm using vacuum.
Advantageously, the method comprises the step of statically electrically charging the laminated top sheet prior to introducing the laminated top sheet into the mould. Preferably, the moulding face of the mould to which the laminated top sheet is to be applied is statically electrically charged with an opposite charge. Ideally, the static electric charges of the laminated top sheet and the relevant moulding face are sufficient to attract and hold the laminated top sheet in engagement with the relevant moulding face of the mould cavity. The method further comprises the step of bringing the laminated top sheet into a position in which the external sheet of the laminated top sheet faces the relevant moulding face of the mould and in which the laminated top sheet is positioned substantially parallel to and in register with the moulding face of the mould to which the laminated sheet is to be applied, and at a predetermined distance from that moulding face; and releasing the laminated top sheet whereby the static electric charge force acting between the laminated top sheet and the moulding face is sufficient to attract the laminated top sheet to the moulding face and retain in engagement with the moulding face prior and during the step of introducing the molten tile material into the mould. In one arrangement, the predetermined distance is 20mm.
Preferably, the mould is a divided mould comprising a pair of complementary constituent parts, each part comprising one of a pair of opposing moulding faces, which define the moulding cavity when the parts are brought together. Ideally, the method comprises the step of moving the complementary parts apart with respect to one another to allow the laminated top sheet to be inserted in the mould and to allow a moulded tile to be extracted from the mould; and a further step of bringing the complementary parts together upon the application of the laminated sheet to one of the complementary parts to receive the molten material. Preferably, the method includes the step of retaining one complementary part stationary and moving the other complementary part.
Preferably, the moulding process is an injection moulding process.
In a further aspect, the invention provides an apparatus for making a tile in accordance with the invention, the apparatus comprising:
a mould for forming a tile, the mould comprising a pair of internal spaced apart opposing moulding faces defining a moulding cavity;
a picking arm configured to pick up and transfer a laminated top sheet comprising an external sheet and a backing sheet into the moulding cavity before a molten plastic material for forming a tile body is introduced into the moulding cavity, and to cause the external sheet of the laminated top sheet to become attached to one of the opposing moulding faces of the mould; means for introducing a molten plastic material into the moulding cavity; and
means for extracting a moulded tile from the mould.
Preferably, the picking arm is configured to pick up a laminated top sheet from a location remote the mould.
Preferably, the apparatus comprises a cutting machine configured to cut a laminated top sheet of a required size from a larger laminated sheet and a transfer mechanism for transferring a laminated top sheet to a picking location remote the mould. Ideally, the picking arm is configured to pick a laminated top sheet from the picking location remote the mould.
In one preferred arrangement, the cutting machine is configured to accommodate and comprises a support mechanism to support a larger laminated sheet which has a width equal the width of one side of a tile to be moulded and a length sufficient to allow a plurality of tiles to be cut from the larger sheet, wherein the larger sheet is wound into a roll, and wherein the support mechanism rotatably supports the roll. The cutting machine also comprises a cutting mechanism configured to cut laminated top sheets of pre-set length from the roll. The cutting machine preferably comprises a set of rollers for drawing a free end of the roll between the support mechanism and the cutting mechanism.
Ideally, the picking arm comprises a vacuum activated gripping head adapted to pick a laminated top sheet using vacuum. Preferably, the picking arm is configured to pick a laminated top sheet by gripping the laminated top sheet at the backing sheet.
Preferably, the picking arm is an automatic electronically controlled robotic arm.
Preferably, the mould is a divided mould comprising a pair of complementary constituent parts, each part comprising one of a pair of opposing moulding faces, which define the moulding cavity when the parts are brought together. Ideally, the complementary parts are movably arranged with respect to one another so that the parts can be moved apart to allow the laminated top sheet to be inserted in the mould and to allow a moulded tile to be extracted from the mould; and brought together to receive the molten material. Preferably, one complementary part is stationary and the other complementary part is movable. In one preferred arrangement, the complementary parts are arranged to move with respect to each other in the direction substantially perpendicular the opposing moulding faces of the mould.
In a preferred configuration, the picking arm is configured to move so as to bring the laminated top sheet into a position in which the external sheet of the laminated top sheet faces the relevant moulding face of the mould and in which the laminated top sheet is positioned substantially parallel to and in register with a relevant moulding face and spaced apart from that moulding face in the direction substantially normal to that moulding face to a predetermined distance before the laminated top sheet is brought into contact with that moulding face. Preferably, in order for the picking arm to position the laminated top sheet parallel to and in register with and normally spaced apart from the moulding face, the complementary parts of the mould are positioned spaced apart sufficiently to allow the picking arm to access the space defined between the spread apart complementary parts.
Advantageously, the apparatus comprises an arrangement for statically electrically charging the laminated top sheet prior to introducing the laminated top sheet into the mould. Preferably, the apparatus also comprises an arrangement for statically charging with an opposite charge a moulding face of the mould to which the laminated top sheet is to be applied. Ideally, the static electric charges of the laminated top sheet and the relevant mould face are sufficient to attract and hold the laminated top sheet in engagement with the relevant moulding face of the mould cavity. In a preferred configuration, when the picking arm takes a position in which the external sheet of the laminated top sheet faces the relevant moulding face and is positioned substantially parallel to and in register with the relevant moulding face of the mould and at a predetermined distance from that moulding face, the picking arm is configured to release the laminated top sheet. Ideally, the static electric charge force acting between the laminated top sheet and the moulding face is sufficient to attract the laminated top sheet to the moulding face so that the external sheet and the moulding face are in contact substantially across their entire surfaces and to retain the laminated top sheet in engagement with the moulding face prior and during the moulding process of the tile of the invention. In one arrangement, the predetermined distance is 20mm. Preferably, the complementary parts of the mould are adapted to move together once the laminated top sheet has been applied to the relevant moulding face, so as to close the mould and to form the moulding cavity. Preferably, the complementary parts are closed under a predetermined pressure to maintain the integrity of the mould cavity during the moulding process. Preferably, the complementary parts are closed at a pressure of 300 tonnes.
Preferably, the apparatus comprises an arrangement for injecting a molten plastics material under pressure into the mould cavity.
In one configuration, the mould is positioned so that the opposing moulding faces lie in planes oriented substantially perpendicular to the ground.
The backing sheet preferably does not melt to the same level of liquidity as the molten plastics introduced into the mould, but becomes sufficiently soft in order to blend with the molten material tile body and, upon cooling, to form a bond with the material of the tile body. For this reason, in a manufactured tile, an interface layer is formed between the backing sheet and the plastics tile body at which the materials of the backing sheet and the tile body are blended and set, i.e. bonded with each other across the entire surface of the tile body. Accordingly, the resulting bonding between the backing sheet and the tile body is permanent and irreversible in that the interface layer becomes an integral part of each of the backing sheet and the tile body so that the backing sheet and the tile body cannot be separated at the interface layer by applying external forces to the tile or due to decay or weakening within the interface layer. Thus, the bonding between the backing sheet and the tile body is considerably superior to an adhesive-based bonding, the latter being prone to failure either at the boundary between the adhesive layer and a substrate material or within the adhesive layer. The bonding between the materials of the tile body and the backing sheet is a physical bond or is a both a physical and a chemical bond.
Thus, the present invention provides a moulded plastics tile which comprises a separately made laminated top sheet that is bonded with the material of the plastic tile during the moulding process, so that a layer of backing material of the top sheet becomes integrated with a layer of the material of the tile. The material of the backing sheet of the laminated top sheet is blended and set with the material of the tile body at the boundary between the materials of backing sheet and the tile body rather than adhered thereto. The so bonded laminated top sheet comprises an external sheet which has a surface colour, ornamental pattern, decoration and/or texture and physical and/or chemical properties independent, and, preferably, different from the material of the tile body. Unlike known moulded plastic tiles, the tile of the present invention can be made having virtually any desired colour, decoration patterns, texture and physical and chemical properties which are independent from the material of the tile body. As previously discussed, the moulding process makes it possible to manufacture a plastic tile formed with a plurality of interlocking members provided at the perimeter of the tile for interlocking with corresponding members of an adjacent tile, thereby providing for a fast and easy way of installing the tiles at a desired location, whereby no adhesive is required to secure the tiles in their position on a desired surface. The present invention makes it possible to make a moulded plastics tile which has a top layer that has an ornamental pattern and/or physical and/or chemical properties independent and/or different from those of the body of the tile. The present invention also allows the integration of the step of forming such a top layer into the process of moulding the tile body, thereby optimising the moulding process. Furthermore, the top sheet of the tile of the invention becomes irreversibly bonded with the material of the tile body, thereby forming a bond which is superior to an adhesive-based type of bonding.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The invention will now be described with reference to the accompanying drawings which show by way of example only, a tile and a method and an apparatus for making such a tile according to the invention. In the drawings:
Figure 1 is a perspective schematic illustration of a prior art plastic tile cut from a larger sheet.
Figure 2 is a perspective schematic illustration of a prior art plastic moulded tile;
Figure 3 is partial cross-sectional view of a laminated top sheet of a plastic moulded tile in accordance with the invention prior to forming the tile of the invention;
Figure 4 is partial cross-sectional view of a plastic moulded tile in accordance with the invention;
Figure 5 is a side elevation of a cutting machine of an apparatus for making a tile of the invention;
Figure 6 is a perspective view of the cutting machine of Figure 5;
Figure 7 is a side elevation of an apparatus for making a tile in accordance with the invention;
Figure 8 is a top view of the apparatus of Figure 7;
Figure 9 is an end elevation of the apparatus of Figures 7 and 8; and
Figure 10 is a perspective view of a gripping head of the apparatus of Figures 7 to 10.
As shown in Figures 3 and 4, a moulded plastic tile 3 in accordance with the invention comprises a plastic tile body 4 having a pair of opposing main faces 4a, 4b and at least one laminated top sheet 5 provided on at least one main face 4a of the tile body 4. The laminated top sheet 5 comprises a backing sheet 51 and an external sheet 52. The external sheet 52 further comprises an upper protective layer 53 which covers the upper surface of the external sheet 52 and protects the external sheet from wear.
The backing sheet 51 is bonded with the material of the tile body 4 at an interface layer 6.
As will be described below in more detail, the interface layer 6 is defined between the tile body 4 and the backing sheet 51 during the process of moulding the tile 3. The interface layer 6 is formed by the materials of the backing sheet 51 and the tile body 4 which are blended together and set during the moulding process, thereby forming a bond between them. The interface layer 6 forms an integral part of each of the backing sheet 51 and the tile body 4.
The material of the tile body 4 and the backing sheet 51 is preferably polyvinyl chloride
(PVC).
The external sheet 52 has colour and/or texture, and/or physical and/or chemical properties which need not be same as those of the tile body. In the presently described embodiment, although not shown in the drawings, the upper surface of the external sheet 52 comprises a printed pattern, which may be, for example, but not limited thereto, an imitation of a natural material, such as wood or stone, or a graphical pattern.
The upper protective layer 53 is preferably transparent or translucent and is laminated with the external sheet 52. Preferably, the material of the protective layer 53 is PVC.
In the presently exemplified embodiment, the thickness of the backing sheet 51 is 0.3mm, the thickness of the external sheet 52 without the protective layer 53 is 0.2mm and the thickness of the protective layer 53 is 0.2mm.
The use of moulding makes it possible to make a plastics tile with interlocking integral members, such as, for example, interlocking members 2 in Figurel , formed around the perimeter of the tile body 4 which are configured to interlock with corresponding interlocking members of another tile for securing the tiles together. The provision of such interlocking members considerably facilitates the process of installation of such tiles, compared to prior art tiles which require an adhesive in order to be fitted.
The laminated top sheet 5 is manufactured separately, prior to making a tile 3 of the invention. Specifically, the laminated top sheet 5 of a required size matching the size of a tile to be made is cut from a previously fabricated larger laminated sheet. In the presently described embodiment, a specifically designed cutting machine 20 (Figures 5 and 6) is provided configured to cut a laminated top sheet 5 of a required size from a larger laminated sheet 55. The cutting machine 20 is a part of an apparatus, indicated generally by reference numeral 200 and shown Figures 7 to 10 for making a moulded plastics tile 3 in accordance with the invention. The cutting machine 20 is suitably configured to accommodate a larger laminated sheet 55 which has a width equal the width of one side of a tile 3 of the invention to be moulded and a length sufficient to allow a plurality of laminated top sheets 5 of a required length (typically equal the length of the tile, which is typically equal the width of the tile 3) to be cut from the larger sheet 55. The larger sheet 55 is wound into a roll 56 which is rotatably supported by a support mechanism in the form of a shaft 24 at one end of the cutting machine 20.
A free end of the roll 56 is fed through a set of rollers 25 into a cutting mechanism 26 configured to cut laminated top sheets 5 of pre-set length from the roll 56. The cutting mechanism 26 comprises a fixed clamp 26a and a movable clamp 26b. The clamps 26a, 26b are spaced apart longitudinally, i.e. in the direction of movement of the material unwinding from the roll 56 and each clamp 26a, 26b comprises an elongate bar (not indicated by a numeral) which extends substantially transversely in relation to the direction of movement of the roll material. The fixed clamp 26a is located between the roll 56 and the movable clamp 26b. The movable clamp 26b comprises a cutting blade 26c movable transversely in relation to the direction of movement of the material of the roll 56. Initially, both clamps 26a, 26b are open so that the material of the roll 56 can pass through each clamp. At the start of a production cycle, a free end of the roll 56 is fed through both clamps 26a, 26b so that there is roll material underneath the cutting blade 26c. The movable clamp 26b closes to hold the roll material while the cutting blade 26c moves across the roll material and creates a new edge of a first laminated top sheet 5. The movable clamp 26b then moves forward, i.e. away from the roll 56 and the fixed clamp 26a, and draws the roll material through a required distance thereby defining the length of a laminated top sheet 5 to be cut off. Next, the fixed clamp 26a closes whereas the movable clamp 26b opens and travels back to its original position at which the movable clamp 26b closes again and the cutting blade 26c cuts across the roll material cutting off a new laminated top sheet 5 and creating a new edge for another laminated top sheet. The movable clamp 26b, then moves forward and draws a further length the roll material through a required distance and the cycle is repeated.
The cut off laminated top sheets 5 continues to travel to a picking location 30 (see Figure
8) on a transfer mechanism provided in the form of a conveyor 23. At the picking location 30, a stopping arrangement 31 is provided for stopping the cut off laminated sheet 5 in an accurate required orientation and at exact coordinates. In the presently, described embodiment, the laminated top sheet travels with the backing sheet 51 facing upwardly.
From the picking location 30, the laminated top sheet 5 is picked and transferred to a mould 70 by a picking arm provided in the form of an automatic robotic arm 80. The robotic arm 80 comprises a gripping head 81 in the form of a plate equipped with vacuum cups 82 connected to an automatically controlled source of vacuum. In order to pick the laminated sheet 5 from the picking location, the robotic arm 80 places the gripping head 81 against the surface of the backing sheet 51 of the laminated sheet 5 and the vacuum cups 82 are activated. The robotic arm 80 then travels towards the mould 70 along a guide mechanism, indicated generally by reference numeral 40 in the drawings.
At a location intermediate the picking location 30 and the location of the mould 70, an arrangement is provided comprising a bar 90 for statically electrically charging the laminated top sheet 5, prior to introducing the laminated top sheet 5 into the mould 70. As the robotic arm 80 travels past the bar 90 for a predetermined period of time (e.g. 2 seconds), the laminated top sheet 5 becomes statically electrically changed in accordance with a pre-determined set of parameters.
In the presently described embodiment, the statically charged laminated top sheet 5 is transferred by the robotic arm 80 to a position upwardly spaced from the mould 70.
Although not apparent from the drawings, in the presently described embodiment, the mould 70 is a divided mould comprising a pair of complementary constituent parts. Each part comprises one of a pair of opposing moulding faces, which define a moulding cavity when the parts are brought together. As shown in the drawings, in the presently described embodiment, the mould 70 is positioned so that the planes of the opposing moulding faces are oriented substantially perpendicular to the ground. It is also apparent from the drawings that the laminated top sheet 5 is made and transferred in an orientation substantially parallel to the ground. Accordingly, the plane of the moulding cavity of the mould 70 and the laminated sheet 5 are oriented substantially perpendicular with respect to each other prior to the laminated sheet 5 being placed into the mould 70. In this connection, a guide arrangement is provided for changing the relative orientation of the robotic arm 80 so that the laminated top sheet 5 is located in a plane which is substantially parallel to the planes of the opposing moulding faces of the mould 70.
Although not apparent from the drawings, the complementary parts are movably arranged with respect to one another on a support 100. In order to allow the laminated top sheet 5 to be introduced into the moulding cavity of the mould 70, the complementary parts are moved apart along the support 100 in the direction substantially perpendicular the opposing moulding faces of the mould to allow the laminated top sheet to be inserted in the mould. Although not apparent from the drawings, in the presently described embodiment, one complementary part is stationary and the other complementary part is movable.
Although not shown in the drawings, the apparatus 200 also comprises an arrangement for statically charging with an opposite charge a moulding face to which the laminated top sheet 5 is to be applied. The static electric charges applied to the laminated top sheet 5 and the relevant moulding face of the mould 70 are sufficient to attract and hold the laminated top sheet 5 in engagement with the relevant moulding face of the mould cavity.
In order to introduce the laminated top sheet 5 into the mould 70 the robotic arm 80 lowers the laminated top sheet 5 so that the external sheet 52 of the laminated top sheet 5 faces the relevant moulding face of the mould 70 and the laminated top sheet 5 is positioned substantially parallel to and in register with the relevant moulding face of the mould 70 and at a predetermined distance from that moulding face, e.g. 20mm. The vacuum cups 82 then release the backing sheet 51 and the statically charged laminated top sheet 5 is attracted to the moulding face by the static electric forces. The static electric forces are sufficient to cause the external sheet 52 and the moulding face to come into contact across substantially their entire surfaces. The static electric forces are also sufficient to retain the laminated top sheet 5 in engagement with the moulding face at least prior to and during the process of moulding the plastic tile of the invention.
Once the laminated top sheet 5 has been applied to the relevant moulding face, the complementary parts of the mould 70 are caused to move together, so as to close the mould 70 and to form the moulding cavity. Preferably, the complementary parts are closed under a predetermined pressure, e.g. 300 tonnes, to maintain the integrity of the mould cavity during the moulding process.
Next, molten plastic material is injected under pressure into the mould cavity for forming a tile body 4. The temperature of molten plastics causes the backing sheet 51 to soften so that a layer of the molten material of the tile body 4 blends with a layer of the material of the backing sheet 51 thereby defining the interface layer 6 therebetween. Preferably, the molten material is retained in the mould in contact with the backing sheet 51 for a period of time between 20 seconds and 40 seconds, which is sufficient to allow the bonding to finish. During the same time interval the contents of the mould cools and sets the material of tile body 4 and the blended materials of the interface layer 6 thereby forming a bond between the materials of the tile body 4 and the backing sheet 51 , whereby the interface layer 6 forms an integral part of each of the backing sheet 51 and the tile body 4. Preferably, the material of the external sheet is selected such that it is capable of maintaining its integrity during the process of moulding of the tile. Also, the thickness of the backing sheet 51 is sufficient to protect the external sheet 52 from the temperature impact of the molten plastics.
Finally, the complementary parts are caused to move apart and the moulded tile 3 is extracted from the mould 70.
The backing sheet 51 preferably does not melt to the same level of liquidity as the molten plastics introduced into the mould 70, but becomes sufficiently soft in order to blend with the molten material tile body 4 and, upon cooling, to form a bond with the material of the tile body 4. For this reason, in a manufactured tile 3, an interface layer 6 is formed between the backing sheet 51 and the plastics tile body 4 at which the materials of the backing sheet 51 and the tile body 4 are blended and set, i.e. bonded with each other across the entire surface of the tile body 4. Accordingly, the resulting bonding between the backing sheet 51 and the tile body 4 is permanent and irreversible in that the interface layer 6 becomes an integral part of each of the backing sheet 51 and the tile body 4 so that the backing sheet 51 and the tile body 4 cannot be separated at the interface layer 6 by applying external forces to the tile 3 or due to decay or weakening within the interface layer 6. Thus, the bonding between the backing sheet 51 and the tile body 4 is considerably superior to an adhesive-based bonding, the latter being prone to failure either at the boundary between the adhesive layer and a substrate material or within the adhesive layer. The bonding between the materials of the tile body and the backing sheet is a physical bond or is a both a physical and a chemical bond.
It will be appreciated by those skilled in the art that modifications can be made without departing from the scope of the invention as defined in the appended claims.