Method of manufacturing tiles

Abstract

 A method of producing a patterned tile (19) comprises cutting a plain tile (12)from a sheet of plasticised P.V.C. material (10), printing a pattern on the tile, coating the patterned tile (15) with a radiation curable lacquer to form a wear layer and curing the lacquer. The tile (12) is located in the printing machine (13) by locating means (14) so that the pattern is printed in register with the tile.
The apparatus for producing a tile by this method comprises a tile cutting machine (11), a dry offset or indirect letterpress printing machine (13), a curtain coating machine (16) and an ultra-violet radiation lacquer curing machine (18).

Description

[0001] This invention relates to the manufacture of tiles, and has particular reference to the manufacture of floor tiles of a vinyl material and having a pattern thereon. However the invention is also applicable to the manufacture of tiles of other materials and for other end uses, such as for example wall coverings.

[0002] It is customary, in the manufacture of such tiles to produce a sheet of the material from which the tile is to be made, print a pattern thereon and then, or after further treatment or lamination with other sheet materials, cut the sheet to form a tile. In the case of a symmetrically patterned tile the cutting step must be done in register with the pattern on the sheet so that a tile having the pattern correctly located thereon is produced, and so that there is conformity between any two tiles having the same pattern. This step of cutting the tiles in register with the pattern, is a difficult one and in consequence complicated and thereby expensive machinery is required for carrying it out. Because of the difficulties encountered in this step a large number of reject tiles tend to be produced, which therefore increases the cost of producing a given quantity of acceptable tiles. Another feature of symmetrically patterned tiles produced in this way is that it is usual for the pattern to include a large border area since discrepancies in the positioning of the pattern on the tile and the width of such a border around the four sides of the_tile are not so apparent with a wide border as they are if there is no border or if the borders are narrow as the case may be. This detracts from the effect of patterning the tile and reduces the scope of the patterns which can be used.

[0003] In the case of both symmetrically and randomly patterned tiles relatively simple designs tend to be used owing to the difficulties encountered in the printing step. In this step it is customary to print the pattern onto a thin P.V.C. film and then to laminate the printed film and the tile sheet material to form the printed sheet from which the tiles are cut. The P.V.C. film has a tendency to distort during either the printing step or the laminating step, and in consequence unsatisfactory tiles may be produced. There is also considerable difficulty in printing in register on the P.V.C. film and cutting the tile in register with the pattern on the laminate. A further disadvantage of the aforementioned method is that it requires the use of printing rollers of a width equal to the width of the sheet from which the tiles are cut, and such wide rollers are costly to manufacture.

[0004] It is an object of the present invention to provide a method by which tiles can be produced and which does not have the aforementioned disadvantages.

[0005] The invention provides a method of manufacture of a patterned tile comprising the steps of, in sequence, cutting a sheet of material to form a plain tile and then printing a pattern on a face of said tile. The pattern may be printed in register with the tile.

[0006] In the method of this invention each tile passes through the printing machine individually, but can be located therein with great precision. In consequence the number of unacceptable printed tiles produced is considerably reduced in comparison with the number produced by the abovementioned conventional method. Surprisingly therefore, although it was expected that a longer time would be required to produce a tile by the method of the invention, by comparison with the conventional method, in which case it probably would be basically a more expensive method of production, nevertheless, due to the fact that considerably fewer unacceptable tiles are produced, it has been found that, the present method is economically favourable with the conventional method. A further advantage of the method of the present invention is that it requires the use of printing plates which are only the width of a single tile, and such plates are considerably less costly than the wider rollers required by the prior art method.

[0007] For example, the conventional method can produce a printed sheet at the rate of 900 square metres per hour but cutting in register is a much slower part of the process and the proportion of cut tiles rejected is high. By comparison the present method can produce patterned tiles at a rate of about 500 square metres per hour but the proportion of tiles rejected is very low. It has been found that in practice the rate of production of acceptable patterned tiles is comparable with the two methods at approximately 500 square metres per hour. In consequence the two methods are surprisingly comparable from an economic standpoint.

[0008] A further advantage to be gained by use of the present method in the case of symmetrically patterned tiles is that no border, or at least a much narrower border than was possible heretofore surrounding the pattern can be included without increasing the proportion of unacceptable tiles produced. For example, with the conventional method a border of one and a half centimetres has been used to limit the number of tiles rejected due to lack of alignment and centralisation of the pattern on the tile. In the method of the present invention a border of half a centimetre or less or even no border, has been found to be satisfactory whilst not unduly increasing the number of tiles rejected for the aforementioned reason.

[0009] The printing of the tile may be by any known printing process, for example letterpress process, rotagravure. process, hot foil stamping, or a silk screen printing process. However, if more than one colour is to be used in the design than in the case of rotagravure, stamping or silk screen printing only one colour can be printed at any one time and these are therefore slower and commercially less attractive processes than the letterpress process. A typical production rate for producing patterned tiles of three colours by the silk screen process is 200 square metres per hour, and this involves the use of three machines in series which increases the capital cost of installing a production line for the tile production. Another disadvantage connected with the silk screen process for use with more than one colour is that of performing the separate print steps in register with each other. For these reasons the letterpress process is preferred, but any one of the other processes may be used if desired, particularly if the design requires the printing of only one colour.

[0010] The tile may be of any suitable material, for example, a polymeric material such as plasticised polyvinylchloride, and may be of one such material or a laminate of different materials. A typical thickness of a tile suitable for use as a floor covering is between .020 and .50 centimetres.

[0011] The printing ink used in the process of the invention is preferably either a solvent drying or radiation curable ink having a formulation such as to be compatible with the material of the tile and any wear layer applied to the printed surface of the tile as hereinafter described.

[0012] It is desirable, particularly in the case of tiles to be used as floor coverings, to coat the patterned face thereof with a wear layer. This is to prevent the "wearing off" of the pattern since printing inks tend to have a low resistance to wear. Such a wear layer may be of plasticised polyvinylchloride and may have a thickness of approximately 0.0013 cm on tiles for use as wall coverings and 0.01 cm on tiles for use as floor coverings.

[0013] However it has been found that a pleasing appearance, in the form of a controllable gloss finish, can be produced on the tile by coating the printed face of the tile with a suitable lacquer and curing the lacquer. The lacquer is chosen so as to provide the desired wear layer.

[0014] The invention also provides a method of manufacture of a patterned tile comprising the steps of, in sequence, cutting a sheet of material to form a plain tile, printing a pattern on a face of said tile, coating the patterned face of said tile with a lacquer and curing the lacquer.

[0015] The lacquer may be any radiation curable organic polymeric lacquer, for example such lacquers are commonly polyurethane-acrylate, polythiol/ene, polyester-acrylate, styrene-acrylate, or mixtures thereof. Preferably the lacquer is a modified polyurethane-acrylate or polythiol/ene based lacquer having suitable wear resistant properties after curing to provide a wear layer of comparable durability with the aforementioned polyvinylchloride wear layers of tiles produced heretofore. The curing process is preferably carried out by subjecting the coated tile to ultra-violet or electron beam radiation.

[0016] The lacquer wear layer may be applied by spraying, by means of a roller or by curtain coating. Use of a roller provides more even thickness control of the coating applied to the tile than does spraying and less wastage of coating material, but a directional effect may be produced by the roller, which would be noticeable if tiles thus coated were to be laid randomly. In consequence although curtain coating is the preferred method, since accurate and even coating of the tile is possible with this method and the coating material is readily recycled so that waste is eliminated, the other methods are not precluded from the scope of the invention.

[0017] The invention also provides a method of manufacture of a patterned tile comprising the steps of, in sequence, cutting a sheet of material to form a.plain tile, printing a pattern on said tile, passing the patterned tile through a curtain of lacquer to coat the patterned surface of the tile with a coating of said lacquer and subjecting the coated tile to radiation to cure said coating or lacquer. The radiation is typically ultra-violet radiation.

[0018] A suitable lacquer will provide a wear layer having a resistance to wear sufficient to delay wearing of the pattern for, for example, some four to five years of the tile being subjected to representative use. A suitable test for such lacquers is, for example, one in which a coated tile is subjected to wear on a Taber abraser using two H18 wheels under a loading of 500 grammes. When the wear layer is worn through under this test the pattern wears in one or two revolutions of the abraser so that an accurate assessment of the wear resistance of the wear layer can be made by noting the number of revolutions of the abraser before the pattern wears away. Lacquers giving a coating which under the above conditions, wears at a low number of revolutions would not be acceptable. Obviously the number of revolutions made before wearing of the layer is proportional to the thickness of the coating applied to the tile, but the cost of producing the tile also increases with the thickness of the coating. Consequently, a suitable lacquer is one with which a coating thickness of, say, 0.01 cm, will survive many, i.e. several hundred revolutions of the Taber abraser under the above test conditions before the pattern wears.

[0019] Suitable lacquers for this purpose are as hereinbefore mentioned, modified polyurethane-acrylate, or polythiol/ene based lacquers, such as are supplied by such companies as W.R. Grace Limited and Thiokol Limited. However the method of the present invention provides for a high flexibility in the choice of finish for the tile. by virtue of the choice of lacquer used, for example, so as to provide a desired high gloss and/or good wear characteristics.

[0020] The invention also provides apparatus for carrying out the aforementioned process comprising, in combination, means for cutting a tile from a sheet of material, means for printing a pattern on a face of said tile and means for locating said tile in said printing means to provide that said pattern is in register with said tile.

[0021] The printing means is preferably a dry offset or indirect letterpress printing machine.

[0022] The invention also provides apparatus for carrying out the aforementioned process comprising, in combination,- means for cutting a tile from a sheet of material, means for printing a pattern on a face of said tile, means for locating said tile in said printing means, means for coating the patterned face of said tile with a lacquer and means for curing the lacquer.

[0023] The coating means is preferably curtain coating apparatus and the curing means may be ultra-violet or electron beam radiation means, preferably the former.

[0024] The invention will now be described further with reference to the accompanying drawings, in which one embodiment of a process and apparatus according to the present invention is shown.

Fig. 1 illustrates in diagrammatic form, the steps in the process of the present invention; and

Figs. 2 to 4 are illustrations of the items of equipment used in performing the process of Fig. 1. Referring to Fig. 1 there is shown a sheet of material 10 which has been formed by extrusion, spreading, pressing, calendering or in any conventional manner and on which is performed, in the sequence shown by the arrows, a number of subsequent process steps. The first step is that of cutting the sheet of material 10 by means of a cutter 11 to form a plain tile 12. A pattern is then printed on a face of the tile 12 by means of a printing machine 13, preferably of the dry offset type, although other forms of printing apparatus may be used as an alternative. The tile 12 is carefully positioned in the printing machine by locating means 14 so that if required the pattern is printed in register with, that is to say in proper relationship with the periphery of, the cut tile 12. The patterned tile 15 is then coated with a lacquer by means of a curtain coating or roller coating apparatus 16 in order to provide a wear layer on the surface of the tile, and to produce a controlled gloss finish of pleasing appearance thereto. The lacquered and patterned tile 17 is then subjected to ultra-violet or electron beam radiation from radiating means 18, in order to cure the layer of lacquer on the tile 17. As a result of these process steps a patterned tile 19 is produced having a cured lacquer wear layer on the patterned surface thereof.

[0025] Fig. 2 shows a printing machine 13 suitable for use in the method of the present invention. The machine 13 is a Model 460 dry offset or indirect letterpress printing machine of the Van Dam Machine Company into which the plain tiles 12 are fed by conveyor 20. In the machine 13 each tile 12 is located and is held in position before and after printing by vacuum holding means. There is a maximum of six printing heads 21 so that up .to six colours may be printed onto the tile 12, the background of the pattern being the white of the plain tile or a colour of the plain tile if a pigment is introduced therein in the production of the initial sheet of material from which the tile is cut. Pressure adjustments for the printing rollers and plate cylinders enable half tones to be printed, or no printing, of any of the colours. The speed of printing is adjustable so as to conform with the speed of operation of the other items of equipment in the production line, and the location means is readily adjustable both for accurate location of the tile in order that the pattern is printed in register therewith and for differing sizes of tile.

[0026] Fig. 3 shows diagrammatically a curtain coating machine 16 of the type CC-1 of the Koating Machinery Company. The printed tiles 15 are fed from the printing machine 13 onto the input conveyor 22 of the coating machine 16. The tiles 15 then pass through a curtain of lacquer 23 and onto an output conveyor 24. The lacquer is contained in tank 25 and is pumped to the coating head 26 by means of pump 27. The pump 27 has a variable speed control 28 controlling the pump motor 29 and the lacquer is pumped to the coating head 26 through filter 30.

[0027] The lacquer passes out of the coating head 26 through a slit orifice formed by lips 31, the width of the slit being governed by adjustment of the lips 31 by means of a micro-adjustment lever 32 set against scale 33. Lacquer not adhering to a tile 15 passes into a collecting trough 34 from which it passes back to tank 25 for recycling. A shield 35 prevents air currents from deflecting the curtain 23 from its intended vertical path. The curtain 23 may be formed by gravity and/or by pressure or vacuum. Adjustment of the relative speeds of the conveyors 22, 24 and the pump 27, the width of the slit provided by the lips 31 and the pressure or vacuum applied to the coating head 26 enables the thickness of the lacquer layer on tiles 17 to be controlled to within fine limits over a wide range of adjustment.

[0028] Fig. 4 shows a conveyorised ultra-violet radiation curing machine 18 of the type Deco-Ray T-240 of the Fusion Systems Corporation. The lacquered tiles 17 are passed through the machine 18 on a conveyor 36, the machine comprising an enclosure 37 in which are mounted ultra-violet lamps. As the tiles 17 are passed under the lamps, the lacquer coating on the tiles is cured. The speed of the conveyor 36 and the intensity of the radiation may be adjusted so that the tiles are exposed to the ultra-violet radiation for a time sufficient to effect the curing of the lacquer layer, at a throughput rate commensurate with that of the other items of equipment in the production line.

Claims

1. A method of manufacture of a patterned tile comprising the steps of, in sequence, cutting a sheet (10) of material to form a plain tile (12) and then printing a pattern on a face of said tile.

2. A method according to claim 1 wherein the pattern is printed in register with the tile.

3. A method according to claim 1 or claim 2 wherein the printing step comprises a dry offset or indirect letterpress printing process.

4. A method according to any one of claims 1 to 3, comprising the step of coating the patterned face of the tile.

5. A method according to claim 4 wherein the coating step comprises a curtain coating process.

6. A method according to claim 4 wherein the patterned tile is coated with a lacquer.

7. A method according to claim 6 wherein the lacquer is a radiation curable lacquer.

8. A method according to claim 7 comprising the step of curing the coated tile by subjecting the same to radiation.

9. A method according to claim 8 comprising curing the coated tile by subjecting the same to ultra-violet radiation.

10. A patterned tile produced by a method according to any one of claims 1 to 9.

11. A tile according to claim 10 wherein said sheet (10) is of a polymeric material.

12. A tile according to claim 10 wherein said sheet (10) is of a plasticised polyvinylchloride.

13. A tile according to any one of claims 10 to 12, having a coating of radiation curable organic polymeric lacquer applied thereto.

14. Apparatus for use in the manufacture of a patterned tile (19) in accordance with the method of claim 1 comprising, in combination, means (11) for cutting a tile(12) from a sheet (10) of material and means (13) for printing a pattern on a face of said tile.

15. Apparatus according to claim 14 wherein said printing means (13) comprises locating means (14) to provide that said pattern is printed in register with said tile.

16. Apparatus according to claim 14 or claim 15 wherein said printing means (13) comprises a dry offset or indirect letterpress printing machine.

17. Apparatus according to any one of claims 14 to 16 further comprising means (16) for coating said patterned tile (15).

18. Apparatus according to claim 17 wherein said coating means (16) comprises curtain coating apparatus.

19. Apparatus according to claim 17 or claim 18 further comprising means (18) for curing said coating.

20. Apparatus according to claim 19 wherein said curing means (18) comprises radiation means.

21. Apparatus according to claim 20 wherein said radiation means (18) comprises ultra-violet radiation means.

Drawing