Roll Systems For Webs Of Material

Abstract

This invention relates to a roll system for guiding a web of material, including a three-high roll arrangement of which the takeup or delivery roll assembly includes shaft means with two disc means of the same diameter thereon, which disc means are separated by a distance greater than the width of the path of the web and in operation co-operate with the roll of the other of the two assemblies to support the intermediate roll.

Description

This invention is concerned with improvements in roll systems for guiding webs of material, particularly webs of considerable width and/or made of particularly thin materials.

In the production and/or processing of webs of material it is necessary in many cases either to reduce the tension acting on the web, this being necessary particularly during drying and/or winding operations in the case of sensitive materials, or to increase the tension as may be necessary particularly in stretching and/or coating operations.

The invention is further illustrated by way of example in the accompanying drawings, in which:

FIG. 1 is an elevational cross section of a three-high roll assembly of the prior art,

FIG. 2 is an elevational cross section of a three-high roll assembly of the present invention,

FIG. 3 is a perspective view of the assembly of FIG. 2 with a heating or cooling attachment,

FIG. 4 is an elevational cross section of the assembly of FIG. 2 with a disc covering,

FIG. 5 is an elevation of the simplest form of roll assembly with discs,

FIG. 6 is a similar view showing a roll between the discs, and

FIG. 7 is a similar view showing a roll between and integral with the discs .

A large number of devices have been developed for this operation of applying different degrees of tension to web material, and the mode of operation of these devices will now be discussed.

The first group is constituted by known systems comprising a plurality of rolls disposed in spaced relationship to each other. In these arrangements, the rolls are usually disposed in different planes. In order to achieve the required progressive change in tension applied to the web, in many cases all the rolls of the system are driven differentially. The disadvantage of this roll arrangement is that on the one hand a large number of rolls have to be used, particularly when fairly large differences in tension in the web have to be achieved so that a structure of considerable size is necessary, while on the other hand, the necessary differential drive for the individual rolls and the synchronizing of the rolls with each other can be achieved only by complicated and expensive means. If the drive of only one roll is incorrectly adjusted, or alters while the machine is running, the machine conditions of the entire installation are adversely affected so that a time-consuming readjustment is necessary.

Roll arrangements are also known which consist of a two-high system. In such systems a roll, usually rubber-coated, is pressed against a driven roll so that a nip is formed between them. Although an arrangement of this kind is particularly simple in construction and can provide relatively large differences in web tension, such a roll system has the considerable disadvantage, particularly when the rolls are of small diameter, that the nip pressure cannot be adjusted with sufficient accuracy. Particularly in the case where wide webs are to be guided, even a very small lack of precision in the adjustment of the nip pressure manifests itself in a adverse manner, e.g., in the form of off-center pull and/or creasing of the web of material. This renders the manufactured or processed webs of material unusable or alters their physical properties to an undesirable extent, or the webs cannot for example be wound with their edges neatly arranged, so that further uneconomical edge-trimming operations have to be carried out.

In order to avoid the disadvantages resulting from guiding the web through a two-high roll arrangement, three-high arrangements are also used in practice (See FIG. 1). In these systems one roll 3, on shaft 10", usually rubber-coated, is pressed against two spaced rolls 1 and 2, on shafts 10' and 10'", one of which is driven by drive shaft D. The arrangement may be such that the coated roll presses against the other two rolls either from above or below, the coated roll adjusting itself between the two other rolls but the web W passing through two nips N.sub.1 and H.sub.2.

This method involving the passage of the web through the nips is used on the one hand for moving the web in the horizontal plane for processing operations and on the other for achieving greater differences in tension where this is required. If the web were passed through only one nip, then to bring the web into the horizontal plane again, additional direction-changing rollers would have to be fitted. Such systems are, however, on the one hand more complicated and more difficult to operate and on the other undesirable because of the increased length of passage therethrough, since this can result in damage to the web, e.g., scratching its surface or increased static charge. For these reasons therefore the web is guided through two nips. This method of guiding the web however has the considerable disadvantage that creases can be pressed into the web, particularly in the case of wide and/or thin and therefore sensitive material, and this leads to considerable reduction in the quality of the web such that it may be rendered unusable.

The present invention provides a roll system for guiding a web of material, the system including a three-high roll arrangement (FIGS. 2, 3 and 4) of which the take-up or delivery roll assembly includes a shaft 4 with two discs 5 and 6 of the same diameter thereon, which discs are separated by a distance greater than the width of the path of the web W and in operation co-operate with the roll 3, on shaft 11", of the other of the two assemblies mentioned (1, on shaft 11', and 3) to support the intermediate roll 3.

It is possible by means of the roll system of the invention to exploit the advantages of automatic adjustment provided by a three-high system without having to accept its disadvantages occurring as the result of guiding the material through two nips. Although only one nip N exists in the present case, high contact pressures can be absorbed, so that a change in the roll setting, for example due to the rolls moving away from one another, can be safely prevented.

In a preferred embodiment, the discs 5 and 6 are adapted to be axially displaceable on the shaft. This enables the corresponding roll assembly to be adjusted to suit the particular widths of the other rolls and/or the width of the web to be guided. After positioning the discs 5 and 6, they are held in position by known means such as screw-down stops or the like.

In a further embodiment of the roll 7 system, a roll is fitted between the discs 5 and 6, the diameter of this roll however being smaller by any desirable amount than the diameter of the discs 5 and 6. However, depending upon the thickness of the web W to be passed through the roll system, the diameter of the roll 7 is preferably such that when the web W moves through the system, although there is contact between it and the roll, no nipping takes place.

In the case of the last-mentioned embodiment, it has been found particularly desirable to mount the discs on bearings. This renders it possible for the discs and the roll to run at differential speeds depending upon their diameters, when the web is being moved through the system and is in contact with the roll. In these constructions, the web is well supported during its passage through the roll system without it being necessary to accept the disadvantage of a second nip.

In another embodiment, there is a roll between and integral with the discs. This arrangement can be regarded as being equivalent to a roll, a central portion of which, corresponding to the width of the web, has been reduced in diameter, for example by turning in a lathe, as compared with two portions at the end-faces.

In the case of a roll between the discs, this assembly is preferably provided with attachments 12' and 12" for supplying a heating or cooling medium. By this means, it is possible to carry out tempering operations, for example cooling, heating operations in the drying or stretching of the web material, and similar processing steps. An arrangement is preferred in which there is contact between the web and the roll since this ensures particularly good heat-transfer. The two other rolls of the three-high arrangement also may be equipped with attachments of this kind so that tempering can be carried out on a differential basis.

Although it is not always absolutely necessary to use a driven form of roll system, it is preferred in practice to drive at least one of of the roll assemblies. For this purpose, use is made of known equipment such as motors and clutches.

Although it is not necessary for the three roll assemblies of the system to be of like overall diameter, it is however preferred in practice to use arrangements in which the outside diameters are all the same.

In many cases and especially when sensitive webs of material are to be handled, it has been found particularly advantageous to apply a covering, preferably of rubber or plastic material, to the surface of the rolls and/or the supporting discs. This counteracts the effect of slip of the web which may result in scratching its surface.

The rolls and/or the shaft and/or the discs are preferably made of steel, in particular stainless steel. For certain applications however, they may be made of other materials such as plastic materials.

Depending upon the number of processing operations to be carried out, the roll system of the invention may be duplicated several times in a single installation, and different arrangements, e.g., in the form of cooling or heating stations, may be used.

The roll system of the invention is inherently suited for the guiding of webs of material generally, but it has proved particularly successful in the guiding of very wide webs, of a width of approximately 3 m to 5 m and more, and of very thin webs having a thickness in the region of 100 .mu.m and less. More especially, the new arrangement enables extremely thin films, as made at present in polyesters for example, and having a thickness in the range of about 2 to 20 .mu.m, to be guided in a satisfactory manner without the webs of material being damaged as they have been when the existing machines have been used.

Referring to FIGS. 5, 6 and 7, 4 is a shaft and 5 and 6 are discs thereon as described above, this assembly being the take-up or delivery roll assembly of a three-high system.

As shown in FIG. 6, a roll 7 is disposed between the discs 5 and 6, the diameter of the roll 7 being less than that of the discs. The discs 5 and 6 are mounted on bearings 8 and 9, respectively.

In FIG. 7, the roll 7 is shown integral with the discs 5 and 6.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

Claims

What is claimed is:

1. A roll system for guiding a web of material, including a three-high roll arrangement of which the take-up or delivery roll assembly includes shaft means with two disc means of the same diameter thereon, which disc means are separated by a distance greater than the width of the path of the web and in operation co-operate with the roll of the other of the two assemblies to support the intermediate roll.

2. A roll system as claimed in claim 1, in which the disc means are adapted to be axially displaceable on the shaft.

3. A roll system as claimed in claim 1, in which a roll is located between the disc means, the diameter of which roll is smaller than that of the discs.

4. A roll system as claimed in claim 3, in which the diameter of the roll between the discs, in the case of any particular web, is such that although the web is touched by the roll, it is not nipped between the latter and the intermediate roll.

5. A roll system as claimed in claim 3, in which the roll between the discs is integral therewith.

6. A roll system as claimed in claim 1, in which any roll is provided with attachments for the supply of a heating or cooling medium.

7. A roll system as claimed in claim 1, in which at least one of the rolls is adapted to be driven.

8. A roll system as claimed in claim 1, in which the said discs and the rolls of the two other roll assemblies are of the same outside diameter.

9. A roll system as claimed in claim 1, in which the cylindrical faces of the rolls, and/or of the said discs, have coverings, particularly of rubber or plastic material, while preserving the relative values of the diameter of the discs and of the diameter of any roll between them.

10. A roll system as claimed in claim 3, in which the said discs are mounted on bearings.