GB2058161A

GB2058161A - Blanket for screen printing machines

Info

Publication number: GB2058161A
Application number: GB8029354A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-09-11
Filing date: 1980-09-11
Publication date: 1981-04-08
Also published as: GB2058161B; ATA430980A; NL8004901A; DE2936633A1; DE2936633C2

Abstract

A printers blanket (1) for a screen printing machine comprises at least one layer of textile fabric which is free of coatings and is reinforced by warp (10) or weft reinforcement threads which may be additional to the basic weave. Multiple layer fabrics are described joined at the selvedges or by crossing warps or wefts. Various twill weaves are suggested. Preferably the yarn is a synthetic plastics monofilament of a diameter not less than 0.1 mm. The fabrics are desirably rot proof and chemical resistant.

Description

SPECIFICATION Blanket for screen printing machines The invention relates to fabric blankets for screen printing machines.

Blankets for screen printing machines are already known per se, wire fabrics being used to serve as printing blankets. The disadvantage of these wire fabrics lies in the fact that the metal wires can tear and in prolonged use, for example during endless rotation, the material thereof suffers fatigue, becomes brittle and wears relatively quickly. A wire fabric which has broken up has the disadvantage that it can contribute to destruction of the web of material which it is intended to carry. Such blankets which consist of a wire fabric are generally used in order to ensure that the air underneath the material can escape or to ensure that there is also a possibility of drawing the printing paste through. The belt is porous.

When the printing paste is applied, it is possible the more easily to print through than with conventional blankets such as are generally used.

Usually, the blankets used have a surface coated with rubber or synthetic plastics material but these have the disadvantage of not being porous.

Furthermore, they are expensive to produce.

The invention is based on the problem of providing a porous blanket for screen printing machines which is on the one hand capable of coping with the requirements of such a blanket and which on the other is long-lived and causes no damage to the material when a negligible amount of wear occurs. Furthermore, a part of the problem lies in improving entrainment of the web of material by the blanket.

The invention resides in that the fabric is constructed as a reinforced coating and adhesionfree textile fabric. This means that the textile fabric should have neither coating no solidification means and be in fact a simple textile woven fabric which is however reinforced. The reinforcement can be provided by disposing the fabric as a double cloth, by incorporating reinforcing threads in a warp or weft direction, by providing an increased number of warp or weft threads or by arriving at a specific choice of material, particularly for these reinforced warp or weft threads which may consist of synthetic or semisynthetic monofilar threads or which may also be of wire if they are individually located, particularly in the bottom fabric or are in the top and bottom fabric. Also, it is possible to provide reinforced dispositions of warp and/or weft threads in the fabric.

The reinforcing effect can also be provided by the choice of particular synthetic or semi-synthetic threads or fibres for producing the fabric as a blanket.

A further quite substantial thought underlying the invention lies in texturising the surface of the fabric. The fabric texture can be occasioned by a particular weave, for example a double twill weave or the like. Texturising can be produced by floating threads, etc. The texturising ensures that the blanket has a frictional adhesion with the web of material which is carried through the machine accurately and in a trouble-free fashion, regardless of how such a screen printing machine looks.

The invention is designed particularly for screen printing machines but this does not exclude the possibility of printing machines of another type being provided with such a blanket.

Examples of embodiment of the invention are shown in the accompanying drawings, in which: Figure 1 is a diagrammatic side view of a screen printing machine in which a blanket is disposed for endless rotation; Figure 2 is a partial plan view of a blanket; Figure 3 is a cross-section through a tubular fabric which can be used as a blanket; Figure 4 is a part of a cross-section through the blanket which is constructed on the hollow strip principle; Figure 5 is likewise a partial cross-section through a blanket which is constructed as a hollow fabric, consisting of three materials in constant exchange, likewise in cross-section; Figure 6 is a double cloth in which the bottom fabric is fastened in punctiform fashion; Figure 7 is a partial plan view of the blanket with the surface structurised by the weave;; Figure 8 is a double cloth with a fastening warp shown as part of a blanket, in cross-section; Figure 9 is likewise a partial cross-section through a double cloth with a binder warp and a reinforcing warp; Figure 10 is a double cloth with a binder weft; Figure 11 is a double cloth with a filler weft, one of the wefts changing the fabric; Figure 12 shows a double twill in the weave design; and Figure 13 shows a triple cloth, the warps being in places woven to another cloth, the illustration being in section in a weft direction.

The blanket 1 according to the invention of a screen printing machine which, as Figure 1 shows, may be endlessly rotating, is driven by a motor 2 and over cylinders 3, 30, 31, being tensioned by a tensioning roller 32, and carries a web of material 4 through printing mechanisms 5 which may be of any desired construction.

In the present connection, what is of interest is the construction of the blanket so that it permits of trouble-free transport of the web of material 4 through the screen printing machine. This blanket 1 must comply with the most widely diverse requirements; it must be capable of being subjected to a tractive loading; it must be permeable to air and it must be possible for suction to be applied to it if, as is not shown, a suction apparatus for example, a reciprocating suction container, is disposed beneath the printing mechanism 5. It must also be acid-resistant since the printing pastes applied by the printing mechanisms generally contain corrosive acids.

The blanket 1 according to the invention consists of a fabric and is in fact a reinforced textile fabric.

Some of the possible ways of producing such a fabric are shown in Figures 2 to 13.

The embodiment according to Figure 2 shows a simple fabric in which reinforcing warp threads 10 are woven in in the warp direction. The reinforced warp threads which can consist of monofilar synthetic plastics wires or which may also be made from ordinary metal wire, can influence the nature of the weave; they can be integrated into the weave or may be present in the weave in the form of an auxiliary warp. The reinforcing threads can also be thicker in cross-section than the normal warp threads. In this case, the same material may be used for all the warp threads in the fabric.

In the selvedge 15 of the blanket 1, the reinforcing warp threads 10 may be of denser sequence than in the central zone so that the selvedge can be more accurately guided through the machine. The normal warp threads are identified in the drawing by reference numeral 110 while the weft is designated 111. Linen, twill, satin or also a mixed weave may be used. It is extremely advantageous to choose a weave which provides a texturising of the surface.

The reinforcement of the blanket 1 can also be brought about by the blanket being constructed as a double cloth as is shown in Figure 3. Figure 3 shows a hollow fabric, in fact one which has an upper warp 110' and a bottom warp 1 10". The top fabric (OGW) and the bottom fabric (UGW) are joined to each other after the fashion of a tubular fabric. In other words, there are two layers of material disposed one above the other in which, where the selvedges are otherwise formed, the weave of the top fabric merges without interruption into the weave of the bottom fabric.

The cross-section is taken parallel with the weft.

The top wefts 111' are represented by solid lines while the bottom wefts are identified by broken lines and reference numeral 111". The warp threads which are in section appear as circles, in fact filled in so that they are solid black in the case of the top warp threads or are white in the interior, in other words they are left empty, in the case of the bottom warp threads 1 10".

Figure 4 shows a possible double cloth which may be used for making the blanket 1, in which a hollow strip structure is incorporated into the double cloth. The cross-section is the same as in Figure 3 except that the weft changes from time to time from the bottom fabric (UGW) to the top fabric (OGW). The points of alternation are indicated in the drawing by reference numeral 12.

Figure 5 shows a possible triple hollow cloth in the same direction of section as in Figures 3 and 4, namely one in which the cross-section is drawn in the weft direction. Here, three materials are in constant interchange in a superposed relationship.

There is also a third warp designated 1 Oa and a third weft designated 111 a. Since the weft may change from one material into another, some of the points of alternation are again designated 12.

This example only illustrates that the idea underlying the invention whereby a blanket is produced from textiles material and is reinforced, can be implemented in various ways.

Figure 6 again shows a further embodiment in which the weft used is not a simple linen weave but a weave which may be differently constructed in the top fabric (OGW) in comparison with the bottom fabric (UGW), and the points of alternation of one of the wefts is again designated 12. Since the points of alternation are not so located that the weft threads merge completely into the parallel fabric as in the case of the embodiment shown in Figures 4 and 5, ail that they form here are fastening points 13 which can be distributed at will over the width of the entire web of material, namely the blanket. These fastening points also at the same time provide for a certain surface texturising of the top fabric (OGW).

Figure 7 shows that texturising of the top fabric by the weave is possible in such a way that an even structurising of the surface of the blanket can be achieved, for example after the fashion of a huckaback weave which is used for towels.

Figures 8 and 9 show that not only the weft can change from one fabric to the other but that also in addition a binder warp 10' may be provided in the material and serve as a reinforcing warp. The sections through Figures 8 and 9 are taken in the warp direction. The binder warp changes from the top fabric (OGW) to the bottom fabric (UGW).

Figure 9 shows an embodiment in which it is not a binder warp 10' which is present, preferably as a reinforcing warp, but a pure reinforcing warp 10 which is inserted between the bottom fabric (UGW) and the top fabric (OGW), the binder warp 10' possibly being a normal binder warp with no particular reinforcing character. Naturally, it is also possible for both the reinforcing warp threads 10 and also the binder warp threads 10' to be produced from particularly strong monofilar material, for example polyamide wires.

Figures 10 and 11 again show sections taken in the weft direction; in fact Figure 10 shows a pure double cloth in which, in contrast to Figure 6, not one of the weft threads of the bottom fabric which is woven into the top fabric but a binder weft 11' is provided instead.

Figure 11 shows a similar cross-section to Figure 10, but in this case the binder weft 11' is also at the same time the weft for the top fabric and furthermore a reinforcing weft 11 is incorporated in the material, in fact at any desired interval so that the material is also transversely reinforced.

Figure 12 shows a pattern for a double twill.

This is a particular type of weave which provides for good texturising in the web of material. This pattern of weave, also referred to as a herringbone pattern, has particular advantages which reside in the fact that the relevant tips 14 of the twill weave may be disposed behind the rear pile knots of the material 4, so that it is possible to achieve a serrated connection between the back of the web of material and the surface of the blanket 1. This double twill can be woven as a single fabric or also as a double fabric so that the blanket 1 carries for example the twill on both sides, but it is also possible for only the top fabric (OGW) to be of double twill weave while the bottom fabric (UGW) may for example be left smooth. This is entirely optional.The selvedges 15 of the fabric which is to be used as the blanket 1 may for example have a linen weave while the actual surface of the blanket 1, may have a special weave, for example a double twill, a double satin, a hailstone or a socalled ice weave or the like.

Figure 1 3 again shows a triple material with a top fabric (UGW), a middle fabric (MGW) and a bottom fabric (UGW), the section through this embodiment again being shown in a warp direction. Here, the warps change from one fabric to another and the points of alternation are shown in the drawing as 12'.

The blanket 1 thus consists of a texturally woven strip with neither coating nor solidification by the application of a solution or the like. This would in fact hamper the freedom with which printing paste can be sucked through the blanket 1, since it closes the pores in the fabric. Thus, the blanket has a ciosed and relatively flat surface.

When the blanket is in use, no adhesive and no needles need be used. The blanket acquires frictional adhesion as a result of the textile fabric itself and the air underneath the material can escape, which is particularly important in the printing area and there is, as has already been mentioned, opportunity for suction of the printing paste through the blanket. The blanket is therefore porous and when the printing paste is applied, it can be forced through all the better.

The slight fabric structure which arises from a correspondingly chosen weave thus has the character of a serration which is effective in conjunction with the material, for example a carpet material, which shows at the back the knots in the pile, which are present in the basis fabric or weave, or in the basic non-woven material or the like, for example in the case of tufting or similar materials.

The material chosen for manufacturing the blanket should be acid-resistant and sufficiently resistant to traction, having as far as possible low elongation properties. Various materials are suitable, for example aromatic polyamides, polypropylene, polyacrylic material, and possibly, according to whether acids are present in the printing pastes, also polyester or polyethylene.

Carbon fibres are also suitable. It is true that these do not have a very good shear resistance but they are highly acid resistant and can be subjected to a considerable tractive loading. Also simple polyamide might well be adequate.

Preferably, monofilar threads are chosen at least for the warp, since these are more traction resistant than some threads and it is advantageous to use monofilar wires for warp and weft if it is necessary to bridge considerable widths of material, e.g. more than 5 metres, and if the blanket dimensions are extremely wide and if the material has to support heavy loadings from, for instance, heavy carpet material. Synthetic or semi-synthetic monofilar threads help to reinforce in the same way as it is possible as a reinforcement to provide areas with increased numbers of warp or weft threads. As will be evident, the idea underlying the invention can be varied in many ways, in fact also by having floating warp or weft threads.

What is essential is that the material be rot and acid-resistant. Preferably, it is formed from synthetic plastics threads or wires, the diameter of which is not less than 0.1 m.

The materials must be resistant to all chemicals in printing pastes, printing mixtures or printing powders.

Claims

1. A blanket for screen printing machines comprising a reinforced textile fabric, which is free of coating and of adhesive.

2. A blanket according to claim 1, wherein the fabric is a double layer cloth.

3. A blanket according to claim 1, wherein the fabric is a multiple-layer cloth.

4. A blanket according to claim 1, wherein reinforcing threads or filaments are disposed in the fabric in the warp and/or weft direction.

5. A blanket according to claim 4, wherein a reinforced disposition of reinforcing warp threads is provided in a selvedge or selvedges of the fabric.

6. A blanket according to claim 2 or 3, wherein the reinforcing warp threads or reinforcing weft threads are disposed between top fabric and bottom fabric.

7. A blanket according to claim 2, 3 or 6, wherein the top fabric (OGW) and the bottom fabric (UGW) or a plurality of layers of fabrics are connected to one another by binder warp or binder weft.

8. A blanket according to claim 7, wherein the fastening points of the binder weft or of the binder warp are disposed in the top fabric.

9. A blanket according to claim 2, wherein the double cloth is woven as a tubular fabric.

10. A blanket according to claim 2, wherein the double cloth is woven as a fabric provided with hollow strips.

11. A blanket according to claim 3, wherein the fabric comprises a hollow fabric in which all the layers are in a state of constant exchange.

12. A blanket according to claim 2, wherein the two layers are joined by ordinary warp or weft threads, so that fastening points are created.

13. A blanket according to any one of the preceding claims, wherein at least one fabric surface is texturised.

14. A blanket according to claim 13, wherein the texturising is created by the weave.

1 5. A blanket according to claim 14, wherein the weave is a double twill, double satin, huckaback or polar weave, in which small areas of the surface of the fabric are raised.

16. A blanket according to claim 15, wherein the raised portions form tips which provide a frictional adhesion with the web of material to be transported by the blanket.

1 7. A blanket according to any one of the preceding claims wherein the selvedges of the fabric provide a connection between multiple layers, if present, and are woven in a reinforced pattern.

18. A blanket according to any one of the preceding claims wherein the fabric is woven from, at least partially, of acid-resistant or acidresistant synthetic and semi-synthetic threads or fibres.

19. A blanket according to claim 18, wherein the threads are monofilaments.

20. A blanket according to any one of the preceding claims, wherein the fabric is porous.

21. A blanket according to any one of the preceding claims, wherein the fabric is of rotresisting material.

22. A blanket according to any one of the preceding claims, wherein the fabric has, over its total surface, areas having an increased concentration of warp or weft threads.

23. A blanket according to any one of the preceding claims, wherein the fabric is chemicalresistant.

24. A blanket according to any one of the preceding claims, wherein the fabric is woven from synthetic plastics monofilaments, the individual diameters of which are not less than 0.1 mm.

25. A printers blanket for a screen printing machine constructed and arranged substantially as hereinbefore described and shown in any of the Figures of the accompanying drawings.