CN221026740U

CN221026740U - Tension control device for pre-wound collagen film

Info

Publication number: CN221026740U
Application number: CN202322895249.0U
Authority: CN
Inventors: 卡洛斯·玛丽亚·隆戈阿雷索; 胡安·内格里桑佩尔
Original assignee: Viscofan Technology Suzhou Co ltd
Current assignee: Viscofan Technology Suzhou Co ltd
Priority date: 2023-10-27
Filing date: 2023-10-27
Publication date: 2024-05-28
Anticipated expiration: 2033-10-27

Abstract

A tension control device for pre-wound collagen films, comprising a plurality of pendulum units, the pendulum units comprising a curved rod (1) and a ring (2) at one end of the rod (1), wherein the pendulum units are identical in weight and are inserted through the ring (2) by a cylindrical rod (8) passing through a pivot axis (6) of the rod for rotation, and wherein the width of the cylindrical rod (8) corresponds to the width of the film. The pendulum unit effects an adjustment of the winding tension by gravity such that the winding tension is the same or very similar at all points, thus avoiding slackening.

Description

Tension control device for pre-wound collagen film

Technical Field

The present utility model relates to a continuous process for producing flexible films made of organic polymers. More particularly, the present utility model relates to a tension control device for pre-winding collagen films intended for food packaging.

Background

Artificial films or casings are often sold in the form of rolls or reels of material that have a great shape regularity and contain a predetermined number of meters wound around a central tubular core or "core" that is typically made of cardboard. In order to ensure the quality of the material, the precise dimensions of the rolls and the number of linear meters contained in the rolls, perfect control of the winding of the material must be made, so as to avoid deviations in direction, irregular accumulation, wrinkles and other anomalies, due to which the rolls lose their symmetry and their regular geometry and therefore their applicability in future performances.

The worldwide production of flexible sheets or webs is very widespread in industry and includes, inter alia, the production of plastic films based on natural or synthetic polymers, the production of fibrous films such as cellulose and vegetable fibers in the paper industry, or the production of textiles from yarns and also from nonwoven both pressed and interwoven fibers. All of these industries have as their products flexible flat sheets in which two dimensions significantly exceed the third, thickness dimension and which must be guided from their origin along the lines along which they undergo certain transformations. One of the greatest challenges during this process is maintaining the flat shape (flatness) of the sheet until the last roll is reached.

In the specific case of a web made by casting techniques comprising a film of polymer dispersed or dissolved in a solvent, as in the case of collagen webs, a film-forming material in paste form (that is to say having a certain viscosity and cohesion value) is pushed through a nozzle with a straight slot, wherein the openings must have a constant and predetermined thickness. Thus, the material flowing out of the nozzle takes the form of a flat sheet or film having a thickness equal to the thickness of the groove and a width equal to the length of the groove. While all points exiting from the extrusion nozzle form a so-called "extrusion front". The lamination quality is continuously deposited on the horizontal conveyor belt at a line speed that may be equal to or different from the output speed of the lamination quality. If the speeds are the same, none of the dimensions of the flat sheet or film are affected by additional external forces other than gravity. If the paste from which the flat sheet or film is derived has sufficient tackiness and cohesiveness, the material will be able to cure on the tape without changing the flat dimensions other than its thickness, which tends to decrease due to mass loss due to evaporation of the solvent used. When the polymer sheet has cured sufficiently to be self-supporting, the polymer sheet separates from the conveyor belt to continue the drying and curing process and is finally rolled.

All points wound on the roll simultaneously form a "winding front". The linear distance travelled by a point of the sheet from extrusion to winding is referred to as the "machine length". In an absolutely flat sheet, the "machine length" from the "extrusion front" to the "rolling front" is the same at all points. The coil is subject to the possibility of suffering from some type of relaxation (void) from its origin, which leads to significant production problems both during the handling of the material and during its final rolling. This is mainly manifested in the occurrence of creases or folds in the film, which make the film an unacceptable material. Indeed, a slack is such a region or area within the plane of the sheet: in said zones or regions, the material exceeds in several directions the dimensions corresponding to flat regions with similar surfaces and characteristics contained in said sheet and is therefore not subjected to the same tension as these regions during dragging thereof in the machine direction, since all the material advances at the same speed.

Generally, any loose surface resists passing through a pair of pinch rolls or into a coil or reel without causing wrinkling.

The reasons for producing films with dimensional variations are manifold and may occur at any other stage from the origin of the sheet itself to production. However, the fibrous collagen sheet obtained by casting may contain various irregularities, especially due to:

a) Instantaneous variation in thickness of the sheet forming the nozzle slot;

b) The non-uniformity of mass due to variations in the size of the fibers and their distribution in the aqueous dispersion may manifest itself as a difference in mass distribution or film thickness during drying.

When the film is separated from the blade, there may be regions that no longer have the same mechanical properties and respond differently to the nominal tension of the line holding the mass motion. For example, if from that time on there is an irregular tension distribution in different areas of the film due to occasional misaligned rollers and these weakened areas are subjected to tension exceeding their elastic limit, the material will collapse, creating a relaxed area and losing its flatness. There may also be areas with different humidity which are no longer supported by the support belt and are subjected to the action of gravity when they finish drying. This manifests itself in a significant lack of flatness of the sheet, which may occur in buckling, sagging in different areas along its surface, in both the central and peripheral areas, or at the edges of the sheet. The result of creating a slack at one point on the sheet is that the "machine length" increases at that point on the sheet.

The main problem caused by the relaxation of the flexible sheet material is, besides possible rejection as commercial material, the creation of creases or wrinkles during rolling and deformation of the roll itself, which gives it an equally refusable appearance or even is not available for subsequent processing operations. Ideally, all points on the collagen membrane should have the same "machine length". During rolling, however, it can occasionally be seen that, for example, in the middle part of the coil, the material is tight, while the edges form waves, since the edges are slightly longer than the average value, and this "extra" material is the cause of the wrinkles.

If there is asymmetry in the excess, e.g. one edge has more material than the other, the rolling will be uneven and will result in wrinkles in the area with the most material accumulated. This also occurs if the rolls are not properly aligned.

The tension at all points of the "winding plane" must be the same. However, at the point where there is slack, the tension is low and rolling is irregular, thereby generating wrinkles.

Disclosure of utility model

The present utility model solves the above-mentioned technical problem by adjusting the winding tension at all points so that the winding tension is the same or very similar.

In order to solve the above technical problem, the present utility model provides a tension control device for pre-winding a collagen film, wherein the tension control device comprises a plurality of fingers or pendulum units, wherein each pendulum unit comprises a curved rod and a ring at one end of the rod, wherein the fingers are identical in weight and are inserted through the ring by a cylindrical rod passing through a pivot axis of the pendulum unit for rotation, and wherein the width of the cylindrical rod corresponds to the width of the collagen film.

In one embodiment, the side of the section of the rod resting on the collagen membrane is curved.

In one embodiment, the rod is made of aluminum or PVC.

In one embodiment, the rod is provided with a weight at the end opposite the ring.

In one embodiment, the rod is sized to: the width is between 1.5mm and 15mm and the distance of the outer curvature arc is between 11cm and 30 cm.

The pre-winding tension control device is a self-adjusting dynamic device that achieves the technical effect by means of several identical pendulum units that apply tension by gravity using their own weight, the several identical pendulum units being mounted on a common pivot axis that is transverse to the machine direction and that is mounted a few centimeters from the flexible film being coupled to the reel. The plane of the film may coincide with the horizontal plane or an oblique angle may be established with respect to the horizontal plane. Each cell applies a force normal to the point of contact with the membrane by taking advantage of its own weight or by the component of gravity (depending on the inclination of the membrane with respect to the horizontal plane). For this purpose, the pendulum unit or the finger comprises a curved lever and a ring at one end of the lever, wherein the pendulum unit is identical in weight and is inserted through the ring by a cylindrical rod passing through the rotation axis or the pivot axis of the lever, and wherein the width of the cylindrical rod corresponds to the width of the membrane.

Drawings

To facilitate a better understanding of the features of the utility model and to supplement the description, the following drawings are attached as an integral part of the description, which are illustrative and not limiting in nature:

Fig. 1a: the pendulum unit or "finger" is schematically shown in side view, having two main parts, a curved lever and a ring.

Fig. 1b: showing the cross section of the bar and the curved lower bearing side thereof.

Fig. 2: is a diagram showing a two-dimensional film that includes a region having a slack, thereby producing an appearance of poor flatness.

Fig. 3: a view of the side profile of the finger for three different support positions on the film corresponding to three different slack portions is schematically shown before entering the reel.

Fig. 4a: representing some of the fingers in different relaxed positions;

Fig. 4b: showing a larger set of fingers acting in positions with different sag;

Fig. 4c: is an overall image in which the relative position of the anti-wrinkling system of the present utility model with respect to the film and the reel on which the film is wound can be seen.

Detailed Description

The system is dynamic in that the position of each of the pendulum units or fingers is variable over time as it depends on the flatness of the web. The system is self-adjusting in that it is subject to gravity and thus relies on a constant force, which is the self-weight of the pendulum unit or finger, which will modify the relative position of the different surface points of the web during its travel towards the reel. The rolling tension of the sheet dynamically supports the weight of the fingers; when slack occurs, the "machine length" increases and the winding tension at that point decreases. At this point, the vertical component of the finger's weight pushes down on the finger, and the finger pushes down on the diaphragm, producing two effects: a) The length is adjusted to the new "machine length" until b) the tension of the sheet at the point compensates for the vertical component of the weight of the finger at the point. Thus, the system dynamically accommodates for slack differences that may occur in the sheet.

The pendulum unit or "finger" 10 in the present utility model comprises a curved bar 1, the curvature of which bar 1 is defined by at least one arc of curvature 5 that creates a convex side or convex surface resting on the membrane 4 and a concave surface opposite the previous convex side or convex surface (fig. 1 a). The section 7 of the bar may be circular, oval or polygonal, but in the case of a polygon the side of the section resting on the membrane is preferably curved (fig. 1 b) so as not to damage the surface of the material on which it rests. The width of the rod cross section may vary, but is dependent on the nominal weight that can be assigned to each cell and the number of fingers that can be placed in a set. The width of the bars may be between 1.5mm and 15mm, for example. Typically, the length of the stem is variable, depending on the type and size of membrane to which the stem is to be applied, but the distance of the outer arc of curvature of the stem of at least the finger is conveniently between 8cm and 10cm, although the distance of the outer arc of curvature of the stem of the finger may be greater, such as between 11cm and 30 cm. In the lever we distinguish between a proximal region or half, which is the region or half that includes the pivot centre at the end of the lever, and a distal region or half, which is the half furthest from the point in which the counterweight can be housed at the other end.

The curved rod is provided with a collar 2 at one of its ends, which collar 2 is attached to one of the sides of the cross section of the curved rod, which may be concave or convex, preferably a concave side. The assembly of the lever and the ring is a so-called "finger" or pendulum unit. The ring of the finger is circular and its inner cavity has a diameter of between 2.5cm and 4cm, through which the pivot axis 6 of the finger passes. The shaft is a cylindrical rod 8, preferably hollow, having a variable length but a width suitable for the membrane in progress. The finger with the ring threaded on the shaft can swing freely due to its own weight. As can be seen in fig. 3, the fingers are adjusted according to several (three) different types of slack, so that the three slack tensions are maintained by the weight of the fingers. The number of fingers in the system may vary depending on the distance between the fingers. The more fingers, the more uniform the tension distribution across the film and the more efficient the system.

When the film under production contains slack 13, this means that there is a defect in its flatness. Thus, within the boundaries of the slack, the length of the material in any direction is greater than the length of material present between the boundaries on a similar but flat surface. In a suitably flat material, for a constant travelling speed, the stresses in both the machine direction and the transverse direction remain constant within the elastic limit of the material, so that all points of the cross section parallel to the axis of the reel enter the reel at the same time. However, the slack area, which remains unstressed and thus contains an excess length of said misaligned material, enters the reel in a disordered manner, which results in a build-up on the surface of the reel, possibly resulting in creases, wrinkles or irregularities on the surface of the reel: the rate of material entering the same leading edge parallel to the spool per unit time differs at one point from the adjacent point.

Among the advantages of such a tension distribution system to prevent wrinkling is the fact that it works dynamically, since the activation of each unit or finger is due to its own weight; with one set of fingers, the full width of the film can be covered in production and thus the arrival time of all adjacent points of the "winding front" is controlled. In one embodiment, the rod is provided with a counterweight 3 at the end opposite the ring.

Those skilled in the art will appreciate in view of this description and the accompanying drawings that the utility model has been described in terms of some preferred embodiments thereof, but that various modifications may be introduced in the preferred embodiments without exceeding the objects of the utility model as already claimed.

Claims

1. Tension control device for pre-wound collagen films, characterized in that the tension control device comprises a plurality of fingers or pendulum units (10), wherein each pendulum unit (10) comprises a curved rod (1) and a ring (2) at one end of the rod (1), wherein the pendulum units are identical in weight and are inserted through the ring (2) by a cylindrical rod (8) which passes through a pivot axis (6) of the pendulum unit for rotation, and wherein the width of the cylindrical rod (8) corresponds to the width of the collagen film.

2. The tension control device for pre-wound collagen film according to claim 1, wherein a side of the section of the rod resting on the collagen film is curved.

3. The tension control device for pre-wound collagen film according to claim 1, wherein the rod is made of aluminum or PVC.

4. Tension control device for pre-wound collagen film according to claim 1, characterized in that the rod is provided with a weight (3) at the end opposite the ring (2).

5. The tension control device for pre-wound collagen film according to claim 1, wherein the rod has a size of: the width is between 1.5mm and 15mm and the distance of the outer curvature arc is between 11cm and 30 cm.