EP0878318B1 - Method for applying a print onto a plastic tube as well as a tire-shaped tube be printed according to the method - Google Patents

Abstract

The tube is first printed and is then heat-shrunk into a circular shape and filled. The tube is first flat-printed symmetrically with the tube centre-line before the tube is bent into a ring. The initial printed image applied is distorted in comparison with the unfolded image. The distortion of the printed image is equal to the change in shape of the tube as a consequence of subsequent tube-shrink. A pre-print distortion factor is calculated which is related to the ring geometry and the heat-shrink characteristics of the plastics tube. The distortion factor relates to the centreline of the product in the filled ring and is positive, and is added to the longitudinal dimension of the printed image.

Description

The invention relates to a method for applying a surface pressure to a Plastic tube, which is crimped after printing and a wreathed tube, printed using the process.

For printing on plastic tubes that are used as sausage casings, are in and of themselves suitable for almost all common printing processes. In practice Mainly two processes have prevailed, namely flexographic printing and gravure printing, the latter especially when printing large runs is applied. The plastic hoses are usually on the outside printed, because hygiene direct contact between the printing ink and prohibit the sausage surface. For sausage casings made of multilayer plastic sheets with seam there is the possibility to apply the pressure between two layers. The printing of the plastic hoses must be carried out so that the Print image neither when storing and processing the plastic hoses nor when Distribution of the sausages surrounded by such plastic hoses or sausage skins changed.

• Neutrales Verhalten gegenüber der Wursthülle selbst und gegenüber dem Wurstbrät,
• Beständigkeit gegen Fett, Wasser, Salz, Lake, Gewürze und Würzstoffe,
• Temperaturbeständigkeit, inert gegen Rauchgase,
• Alterungs- und Lichtbeständigkeit,
• Abriebfestigkeit,
• Festigkeit bei Dimensionsänderungen, d.h. Mitgehen des Druckbildes mit der Wursthülle bei Dehn- und Schrumpfvorgängen.

In the prior art, as described, for example, in the series "Fleischforschung und Praxis", 2nd edition 1991, Hans Holzmann Verlag GmbH & Co. KG, Bad Wörishofen, pages 41-48, the following requirements must be met:

• Neutral behavior towards the sausage casing itself and towards the sausage meat,
• Resistance to fat, water, salt, brine, spices and seasonings,
• Temperature resistance, inert to flue gases,
• Resistance to aging and light,
• Abrasion resistance,
• Strength in the event of dimensional changes, that is, the printed image goes along with the sausage casing during stretching and shrinking processes.

The latter requirement also means that the print image at stretch and Shrinkage changes, i.e. different dimensions compared the print image before such stretching and shrinking processes and thus is distorted.

Flexo printing mainly works from roll to roll, with that from a roll of plastic tubing is guided over a roller on the the rubber cliché is applied to the printed image. The raised parts of the Clichés are wetted with printing ink on the surface of the plastic tube is transmitted. In addition to normal flexographic printing inks, the printing ink is mainly used so-called reaction colors, which consist of two components, namely the color and the hardener. The two components are mixed together in a certain ratio right before printing begins and must be printed in a given time for the reaction - the networking - can take place on the surface of the tubular casing.

The flexographic printing inks are solvent inks (possibly also water-soluble inks) with relatively low solids contents, which are set the lower the higher the print speed. With a multi-color print must the plastic tube to be printed passes through as many ink stations as Colors are applied. The printed plastic tube is wound up and made up.

Printed sausage casings or plastic hoses are effective as advertising Packaging to create a branded item, but can only describe and classify the product as such. In addition, by the declarations necessary for food law are applied.

Nowadays, more and more printed plastic hoses are used as sausage casings used. This makes it possible for everyone to be interested in the consumer Include information in the print image, e.g. the indication of the type of sausage and their quality level, references to awards, trademarks, and others Markings as well as the name and address of the sausage manufacturer. Furthermore can provide special information for storage, preparation and consumption be attached.

In the production of wreathed plastic hoses, such as those used for sausage wreaths are used, the problem arises that one on the initially flat straight plastic tubing applied pressure by shrinking during of the wreath is distorted and therefore difficult to read, for example Bar codes, texts, logos or other markings can occur.

EP-A 0 495 285 describes a method for applying pressure to a Flat film made of plastic described, which after printing to a tube molded and shrunk onto a cylindrical or conical object. The pressure is distorted from the size after shrinking, this pressure distortion is chosen to be as great as that when the Distortion occurring. For different horizontal zones of the printed image are distortion factors based on the ratio of the hose circumference to the The scope of the object to be wrapped is determined according to which the Pre-distorted print image. The distortion factors take into account that the Hose circumference is larger than the circumference of the object to be wrapped and therefore the printed image with the film shrinks accordingly in the transverse direction.

The known method involves uniform shrinking a film on an object, the distortion factors for the pressure on the same relationship between hose circumference and circumference of the object to be wrapped are due. There is no evidence of predistortion of a Print image on a hose to be wreathed after the print job is applied.

The object of the invention is a method and a printed by the method, wreathed hose filled with a food to create the pressure after the wreath is largely free of distortion.

This object is achieved by a method in such a way that the surface pressure symmetrical to the center line in the longitudinal direction of the flat, an elongated rectangular tube forming hose in front of the wreath is printed that the areal pressure along the center line depending on the Wreath geometry and the shrinkage behavior of the hose is pre-distorted and that the predistortion is the same as that of the wreath due to the shrinkage occurring amount of tube distortion is selected.

In one embodiment of the method, the flat area is used for pre-printing Pressure is a distortion factor given after the ringing of the hose Final dimension of a route added. The distortion factor increases with increasing Inner diameter of the rim with constant rim caliber of the curved hose from. In forming the method, the distortion factor of the pressure is along the Center line of the tube positive. In particular, the distortion factor for 24 - 5 cm is Inner ring diameter 5 to 30% of the length of the center line of the pressure after Shrink the hose.

As part of the task, a wreathed hose is created, in which the flat pressure on the food-filled, hose along the length of the hose the same length as the length of the not predistorted printed image along the center line of the hose in front of the collar.

In a development of the invention, the tube material is a thermally shrinkable single or multi-layer tubular casing, in particular based on Cellulose hydrate, regenerated cellulose, non-derivatized cellulose, polyamides, Polyester and / or polyolefins.

According to the invention, the pressure of such a hose is a combination of words and pictures, a text, a bar code, a logo, a trademark, an image, a Word, label or other identification.

Figur 1

eine Draufsicht auf einen schematisch angedeuteten rechteckigen Druck auf einem flachgelegten, nicht gekranzten Kunststoffschlauch,

Figur 2

eine Draufsicht auf den Kunststoffschlauch der Figur 1 mit verzerrtem Druck nach dem Kranzen und dem Füllen mit einem Nahrungsmittel,

Figur 3

eine Draufsicht auf einen schematisch angedeuteten trapezförmigen Druck auf einem flachgelegten, nicht gekranzten Kunststoffschlauch, und

Figur 4

eine Draufsicht auf den Kunststoffschlauch der Figur 3 mit unverzerrtem Druck in Längsrichtung des Schlauches, nach dem Kranzen und dem Befüllen mit einem Nahrungsmittel.

The invention is explained in more detail below with reference to the drawings. Show it:

Figure 1

2 shows a top view of a schematically indicated rectangular print on a flat, non-crowned plastic tube,

Figure 2

2 shows a top view of the plastic tube of FIG. 1 with distorted pressure after the ringing and filling with a food product,

Figure 3

a plan view of a schematically indicated trapezoidal pressure on a flat, not crowned plastic tube, and

Figure 4

a plan view of the plastic tube of Figure 3 with undistorted pressure in the longitudinal direction of the tube, after the ringing and filling with a food.

In the manufacture of wreathed plastic hoses on the front of the wreath a flat pressure is applied, it occurs due to the shrinking during the wreath process to a distortion of the pressure. Based on the figures 1 and 2 the occurrence of the pressure distortion is explained by way of example. Figure 1 shows a straight plastic tube 1, the flat width 2 of for example 50 mm. On the center line m of the flat plastic tube 1, a surface pressure 3 is applied symmetrically to this center line m, which, for example, forms a rectangle or square. In the present case the areal print 3 is a square with the side length a. The plastic hose 1 is after printing in a known manner by thermal shrinkage wreathed and then filled with food or on a roll wound up and stored until further processing.

Figure 2 shows a top view of a wreath with a food such as Sausage meat-filled plastic tube 4, the wreath caliber 5 of for example 32 mm. The pressure 3, which according to FIG. 1 is a square, has transformed into a distorted flat print 6, which is trapezoidal, caused by the curvature of the plastic tube 4.

The two side edges b and c are curved, while the side edges d, d are straight, but are inclined to one another. The pressure 6 is also arranged symmetrically to the curved center line m _{K of} the hose 4. An inner ring radius r _KI is, for example, 4 cm. It is obvious that the pressure 6 is distorted due to the curvature of the tube 4 compared to the original pressure 3. It is obvious that when printing. which consists, for example, of a bar code, which distortion can lead to problems when reading out the bar code. The trapezoidal distortion is caused by the shrinking of the rim geometry in the longitudinal direction,

3 and 4, the method according to the invention is used for avoidance described such a pressure distortion. It is assumed that with a given wreath geometry, i.e. Inner ring diameter and Wreath caliber and known material of the plastic tube, the pressure pre-distortion to be determined beforehand as the size of a so-called distortion factor. This distortion factor as a percentage of the initial length will be explained in more detail later become. It is placed on the center line of an undistorted, straight plastic tube 7, as shown in Fig. 3, and is positive, i.e. he becomes one according to the wreath given the final dimension of a route. so that a predistorted distance AA on the center line m of the plastic tube 7 is obtained. The distance AA is also the middle distance of the pressure 8 in Fig. 3. The plastic hose 7 has a flat width of 50 mm, for example after the wreath, a wreath caliber 5 of, for example, 32 mm, as in FIG. 4 is shown. The flat pre-distorted print 8 has the shape of a trapezoid with a base side e, a cover side f and the inclined sides g, g, which after converge at the top. Below the center line m is the center line of the lay flat To understand plastic hose in the longitudinal direction, which is an elongated forms a rectangular band. The plastic tube is filled with a food filled, so the center line m in the central plane, but also above or below the median plane of the filled, filled plastic hose for Coming couches.

In Fig. 4 a filled filled plastic hose 9 is shown, the one in the longitudinal direction has distortion-free flat pressure 10. The print 10 has two mutually straight sides i, i, the shortest distance BB the desired final dimension of the pressure after the wreath in the Longitudinal direction corresponds. The other two sides h, h, are corresponding to the Wreath curvature curved, parallel to each other and of equal length. By default of the distortion factor, the pressure predistortion becomes the same as that of the crown due to the shrinkage of the plastic tube 7 occurring tube distortion chosen so that it compensates for the pressure predistortion with the Hose distortion occurs and as a result one in the longitudinal direction of the plastic hose distortion-free printing is obtained.

The distortion factor is calculated as follows: Distortion factor = (1- Wreath centerline diameter Outside diameter of the ring ) 100% = Wreath caliber Inner rim diameter + 2 x rim caliber 100%

Under certain conditions, the wreath process with a hose material carried out, which has undergone pre-stretching, this value for the pre-stretching in the formula given above for the distortion factor subtracted from.

Is the material for the plastic hose a one or multilayer shrinkable polymer tubing, is generally its shrinkability in 80 ° C hot water after 5 minutes around 8%. This However, value can vary in special applications.

Any thermally shrinkable single or multi-layer material comes as tube material Tubular casing, in particular based on cellulose hydrate, regenerated Cellulose, underivatized cellulose, polyamide, polyester and / or polyolefins questionable.

The print can be a word-picture combination, a text, a Bar code, a logo, a trademark, an image alone, a word alone, a label or act in any other way.

The table below shows the distortion factors for common ring calibers from 24 to 64 mm and corresponding ring inside diameters from 5 to 24 cm in percent, which were calculated according to the above formula. It applies to the distortion factor that the distortion factor decreases as the inner diameter of the ring increases with a constant ring caliber of the curved hose. On the other hand, if the inside diameter of the ring is kept constant, the distortion factor increases with the ring diameter. BI B II B III B IV BV B VI Wreath caliber [mm] 30th 24th 40 45 51 64 Inner rim diameter [cm] 4th 5 10 15 20th 24th Distortion factor [%] 30th 24.5 22.2 18.8 16.9 17.4

Based on the specified rim geometries and the known hose material can determine the distortion factors according to the formula above become. Their determination is based on the positioning of the pressure on the Center line of the wreath product. The distortion factor for the center line of the wreath product is thus characteristic of the entire, flatly arranged Viewed pressure. As can be seen from the table above, for example a distortion factor at a pressure B II on the center line of the tubular casing of 24.5% are considered positive and at a pressure B V a Distortion factor of 16.9%, then a distortion-free pressure, i.e. a zero distortion to get the pressure on the wreath product. With the print B VI the distortion factor is 17.4%, and can be reduced to 5%, for example if the pressure is not symmetrical to the center line of the wreath product is arranged, but with its outer edge against the outer edge of the Wreath moves.

Claims (12)

1. A process for applying a planar print to a plastic tube which after printing is made into a ring shape by shrinking, which comprises printing the planar print symmetrically to the central line in the longitudinal direction of the flattened tube forming an elongate rectangular strip before the shaping into a ring, predistorting the planar print along the central line depending on the ring geometry and the shrinkage behavior of the tube, and selecting the predistortion to be of the same size as the amount of the tube distortion occurring due to shrinkage during shaping into a ring.
2. The process as claimed in claim 1, wherein a distortion factor for the predistortion of the planar print is added to the final dimension of a section predetermined after shaping the tube into a ring.
3. The process as claimed in claim 2, wherein the distortion factor decreases with increasing inner ring diameter at a constant ring caliber of the curved tube.
4. The process as claimed in claim 2, wherein the distortion factor of the print is positive along the central line of the tube.
5. The process as claimed in claim 3, wherein the distortion factor for 24 to 5 cm inner ring diameter is 5 to 30 percent of the length of the central line of the print after shrinking the tube.
6. The process as claimed in claim 3, wherein the distortion factor is chosen according to the formula (ring caliber/inner ring diameter plus 2 x ring caliber) · 100%.
7. A ring-shaped tube printed by the process as claimed in claims 1 to 6, wherein the planar print on the food-filled, ring-shaped tube along the longitudinal direction of the tube is the same length as the length of the non-predistorted printed image along the central line of the tube before shaping into a ring.
8. A ring-shaped tube as claimed in claim 7, wherein the ring caliber is in the range 24 to 64 mm.
9. A ring-shaped tube as claimed in claim 7, wherein the inner ring diameter is 5 to 24 cm.
10. A ring-shaped tube as claimed in claim 7, wherein the tube material is a heat-shrinkable single-layer or multilayer tubular casing, in particular based on cellulose hydrate, regenerated cellulose, nonderivatized cellulose, polyamide, polyester and/or polyolefins.
11. A ring-shaped tube as claimed in claim 7, wherein the print is a word-image combination, a text, a bar code, a logo, a trademark, an image, a word, a label, or other designation.
12. The use of a ring-shaped tube as claimed in one or more of claims 7 to 11 as food casing, in particular as sausage casing.

Images