Title of Invention

AIR DISTRIBUTION FRAME IN HEATING CHAMBER

Abstract

A heating chamber (1) for evaporating a fluid from a web (3) of packaging material passing through the heating chamber (1) is described, which comprises an air-distribution system and a frame (5) provided with heating elements (6) arranged to heat the web (3). The frame (5) is hollow and provided with a plurality of holes (11) such that the air is distributed through the hollow frame (5) and introduced in the heating chamber (1) through the holes (11) . A method for evaporating a fluid from a web (3) of packaging material is also described, which comprises the step of passing the web (3) through a heating chamber (1) comprising a frame (5) provided with heating elements subjecting the web (3) to heat. The frame (5) is hollow and an airflow distributed through the frame (5) is provided to the chamber (1) through a plurality of holes (11) in the frame (5), so that the web (3) is subjected to heat from the heating elements (6) and to the air flow. Elected for publication: Fig. 2

Full Text

AIR DISTRIBUTION FRAME IN HEATING CHAMBER Technical field of the invention This invention relates to a heating chamber for evaporating a fluid from a web of packaging material passing through the chamber, comprising an air-distribution system and a frame provided with heating elements arranged to heat the web. The invention also relates to a method for evaporating a fluid from a web, comprising the step of passing the web through a heating chamber comprising a frame provided with heating elements subjecting the web to heat. Background art Within packaging technology, use has long been made of packages for packing and transporting products such as milk, juice and other beverages. A large group of these packages is produced from a laminated packaging material comprising a core layer of, for example, paper or paper-board and an outer, liquid-tight coating of thermoplastic material on at least that side of the core layer which forms the inside of the package. Sometimes the material also includes a gas barrier, for example in the form of an aluminum layer. Such packaging containers are often produced in that a web of packaging material is formed into a tube by overlappingly sealing the longitudinal edges of the web. The tube is continuously filled with a product and then transversally sealed and formed into cushions. The seal-ing is made along narrow transverse mutually spaced apart sealing zones. The transverse sealing of the tube takes place in a per se known manner substantially at right an-gles to the longitudinal direction of the tube. The sealed-off portions of the tube thus containing contents are thereafter separated from the tube by means of inci-sions in these sealing zones. Afterwards, the packages may be formed into for example parallelepipedic packages by additional folding and sealing operations. This technology of forming a tube from a web is well known per se and will not be described in detail. To extend the shelf-life of the products being packed it is prior known to sterilize the web before the forming and filling operations. Depending on how long shelf-life is desired and whether the distribution and storage is made in chilled or ambient temperature, dif-ferent levels of sterilization can be chosen. One way of sterilizing a web is chemical sterilization using for ex-ample a bath of hydrogen peroxide. After the sterilization bath it is crucial that the sterilizing agent is thoroughly removed from the material web. In prior art the removal is conducted by leading the material web between a pair of squeegee rollers, where excessive sterilizing agent is removed, and there after through a heating chamber, in which the web is heated by heating elements so that the agent is evaporated, The sole use of heating elements is, however, in some cases inconvenient. Firstly, it may be difficult to obtain a homogenous heating of the material web and sec-ondly, in the case of an unexpected shutdown of the proc-ess, material web in the heating chamber may be subjected to too much heat, resulting in blistering of the thermo-plastic material forming the liquid-tight coating of the container and other constructional damages. It is also known in the art to add nozzles close to the heating elements through which air can be introduced in the heating chamber. In prior art this type of arrangement has required a separate preheater of the air and the nozzles could not provide a sufficient airflow for all cases. Summary of the invention It is the object of the present invention to offer a solution to the above problems. This purpose is achieved with a heating chamber for evaporating a fluid from a web of packaging material passing through the chamber, com-prising an air-distribution system and a frame provided with heating elements arranged to heat the web, wherein the frame is hollow and provided with a plurality of holes such that the air is distributed through the hollow frame and introduced in the chamber through the holes. The purpose is also achieved with a method for evaporating a fluid from a web of packaging material, comprising the step of passing the web through a heating chamber comprising a frame provided with heating ele-ments, subjecting the web to heat, wherein the frame is hollow and an airflow distributed through the frame is provided to the chamber through a plurality of holes in the frame, so that the web is subjected to heat from the heating elements and to the air flow. The use of air in the heating chamber makes the tem-perature distribution more even over the web and by in-troducing the air through the hollow frame the need for a separate air supply system is eliminated. It is easy to provide a sufficient airflow and the improved flow of air also improves the heat conduction from the heating ele-ments, and thus shortens the start-up time. The airflow is preferably provided between the heating elements and the web, since this results in an efficient air distribution over the web. According to a preferred embodiment the airflow is directed essentially parallel to the web. This course of action renders it possible to control the airflow over the web surface as well as the temperature of the web surface. The parallelity of the flow also results in a more even flow and temperature. Since the air flows through the heating elements it is possible to use the heating elements to pre-heat the air without the need for a separate preheater and due to the same feature it is possible to cool the frame, the heating elements, the entire heating chamber, and the web material with the air. This is particularly important in the case of a standstill, which otherwise can result in blistering or other damages of the web. Thus the feature reduces spillage of material. The feature is especially useful in cases where the forming of containers is inte-grated with the process of filling the containers with a fluid, generally a beverage, where it also eliminates longer standstills necessary to remove the damaged parts of the web material, re-thread the web etc. The fluid to be evaporated is, especially in the cases where the web is suited for containers for bever-ages, a sterilization fluid, preferably hydrogen perox-ide. It is critical that the container is sterilized and also that the hydrogen peroxide is evaporated from the web material before it is contacted with the liquid. The frame carrying the heating elements is prefera-bly hingedly supported by the heating chamber. This fa-cilitates regular maintenance and also threading of the material web through the machine, which is a convenient feature in the case when several frames are included in one heating chamber and the web is threaded back and forth through the chamber and between the frames in a sandwiched manner. The characteristics given to the heating chamber above are preferably also comprised in the method of evaporating fluid from a web. The method preferably comprise also the step of preheating the air in a start-up phase by means of the heating elements. This eliminates the need for a separate air-heater, thus increasing cost effectiveness. In a preferred embodiment the method also comprises the step of using the air distribution system for coolinc the heating chamber. This step is particularly useful in the case of an unplanned standstill of the production line. If the web is left in the heating chamber for the extended period of time associated with a standstill, the built-up heat energy in the components of the heat cham- ber will radiate onto the web and could thereby cause extensive material damage, even if the heating elements are shut off. According to the invention the cooling air distributed through the frame will help avoid the blistering. It is desirable to evaporate H2O2 at approximately 80°C and in order to avoid damages to the material web, caused by the heating elements, the air flow preferably has a temperature of about 60°C. It is obvious that the preferred temperatures can be varied to accommodate a particular type of web material, sterilization agent etc. Brief Description of the Drawings A heating chamber according to the present invention will be more fully understood from the following non-limiting example of a preferred embodiment, under reference to the accompanying drawings, in which: Fig. 1 is a schematic sectional view of a heating chamber with threaded material web following a peroxide bath, Fig, 2 is a perspective view showing a heating chamber according to the configuration of Fig. 1, but without the heating chamber housing and the material web, and Fig. 3 shows a front view of a single frame with heating elements, on which a set of heating elements have been removed for better view of the air distribution holes. Detailed Description of a Preferred Embodiment In a production line where containers suitable for beverage are produced a heating chamber 1 is preceded by a sterilization bath 2 containing hydrogen peroxide. After passing through the peroxide bath 2 the web 3 of packaging material, still carrying a film of peroxide, is led through the heating chamber 1 where the last remain-ders of peroxide are to be evaporated in order not to contaminate the product contained in the resulting pack- age. Prior to entering the heating chamber 1 the web 3 passes a pair of squeegee rollers 4, where peroxide is evenly spread out over the entire width of the web 3 and excess peroxide is removed. The heating chamber 1 comprises two hollow frames 5 carrying heating elements 6. The frames 5 are constructed from metal pipes having a diameter of approximately 1 cm and are defined by a rectangular frame with several transverse ribs 5' of the same type of pipes. The heating elements 6 comprise electrically heated wire mesh heaters and are provided in the principal plane of the frame 5. The frames 5 are hingedly supported in a housing 7 defin-ing the heating chamber 1. The hinged support 8 also com-prises a coupling 9 through which the air enters the sys-tem. When threading the material web 3 through the heat-ing chamber 1 the frames 5 are put in an open position and then sequentially closed as the threading progresses. The material web 3 passes the length of the heating cham-ber 5 three times, guided by guide rollers 10. During the first and last passage it passes on the outermost side of the first and the second frame, respectively and during the intermediate passage it passes between the two frames. On each hollow frame there are provided, on the lower side of the transversal parts 5', holes 11 with a diameter of approximately 1-2 mm that facilitate distri-bution of air through the frame 5 and onto the web 3, via the holes 11. By means of the holes 11, an airflow essen-tially parallel to the material web 3 is provided. To keep the web from being brought into direct con-tact with the heating elements the heating chamber is provided with protective rollers or paper supports 12. The paper supports 12 are generally formed from plastic tubes. During a start-up process the air flow will help to transport heat from the heating elements 6 and spread it throughout the heating chamber. This vouches for a faster start-up procedure. The air flow is cooler than the heat-ing elements 6 so as to be able to absorb heat from the elements and spread it evenly over the web surface, thereby avoiding local blistering of the material web 3 caused by local overheating. Practically the same feature is used in case of a standstill. Then the heating ele-ments 6 are shut off, while the air is continuing to flow in order to cool the frame and the heating chamber 1 in general and the material web 3 in particular. The heating elements 6 give the interior of the chamber 1 a temperature of approximately 80°C, in order to efficiently evaporate the H2O2 and the air flow has a temperature of about 60°C. It is obvious that the preferred temperatures can be varied to accommodate a particular type of web material, sterilization agent etc. The skilled person realises that a number of modifications of the embodiments described herein are possible without departing from the scope of the invention, which is defined in the appended claims. For instance, the number of frames 5, the temperature of the heating elements 6 and the circulated air as well as the number of passages through the heating chamber 1 made by the material web 3 can be varied to meet the demands of various configurations of web material and sterilization agent. CLAIMS 1. A heating chamber (1) for evaporating a fluid from a web (3) of packaging material passing through the heating chamber (1), comprising an air-distribution sys- tem and a frame (5) provided with heating elements (6) arranged to heat the web (3), characterised i n that the frame (5) is hollow and provided with a plurality of holes (11) such that the air is distributed through the hollow frame (5) and introduced in the heat-ing chamber (1) through the holes (11). 2. A heating chamber according to claim 1, wherein the holes (11) are arranged to provide an airflow between the heating elements (6) and the web (3). 3. A heating chamber according to any of the preced-ing claims, wherein the provided airflow is directed es-sentially parallel to the web (3). 4. A heating chamber according to any of the preced-ing claims, wherein the heating elements (6) are addi-tionally arranged to preheat the air. 5. A heating chamber according to any of the preced-ing claims, wherein the air distribution system (5) is additionally arranged to cool the frame (5). 6. A heating chamber according to any of the preced-ing claims, wherein the fluid is a sterilization fluid. 7. A heating chamber according to claim 6, wherein the sterilization fluid is hydrogen peroxide. 8. A heating chamber according to any of the preced-ing claims, wherein the frame (5) is hingedly supported in order to facilitate the threading of the material web (3) . 9. A method for evaporating a fluid from a web (3) of packaging material, comprising the step of passing the web (3) through a heating chamber (1) comprising a frame (5) provided with heating elements (6) subjecting the web (3) to heat, characterised in that the frame (5) is hollow and an airflow distributed through the frame (5) is provided to the chamber (1) through a plurality of holes (11) in the frame (5), so that the web (3) is subjected to heat from the heating elements (6) and to the air flow. 10. A method for evaporating a fluid from a web (3) according to claim 9, wherein the holes (11) are provid- ing an airflow between the heating elements (6) and the web (3) . 11. A method for evaporating a fluid from a web (3) according to claim 9 or 10, wherein the holes (11) in the frame (5) direct the airflow essentially parallel to the web (3). 12. A method according to any one of claims 9-11, further comprising the step of preheating the air by means of the heating elements (6). 13. A method according to any one of claims 9-12, further comprising the step of cooling the frame (5) and the heating elements (6) by means of passing cooling air through the frame (5).

Documents:

1875-CHE-2005 AMENDED CLAIMS 25-01-2012.pdf

1875-CHE-2005 EXAMINATION REPORT REPLY RECEIVED 25-01-2012.pdf

1875-CHE-2005 FORM-3 25-01-2012.pdf

1875-CHE-2005 CORRESPONDENCE OTHERS.pdf

1875-CHE-2005 CORRESPONDENCE PO.pdf

1875-CHE-2005 FORM-18.pdf

1875-che-2005-abstract image.jpg

1875-che-2005-abstract.pdf

1875-che-2005-claims.pdf

1875-che-2005-correspondnece-others.pdf

1875-che-2005-description(complete).pdf

1875-che-2005-drawings.pdf

1875-che-2005-form 1.pdf

1875-che-2005-form 26.pdf

1875-che-2005-form 3.pdf

1875-che-2005-form 5.pdf

1875-che-2005-other-documents.pdf