Patent Publication Number: US-6698161-B1

Title: Device for loading film on machines for wrapping products

Description:
This application is a 371 of PCT/IB00/00284 dated Mar. 16, 2000. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a device for loading film on machines for wrapping products. 
     BACKGROUND ART 
     Current machines for wrapping groups of products (of the automatic or semi-automatic type) basically consist of a platform which supports the groups of products on a pallet (the platform may be rotary or fixed) and a structure which supports the film feed means. This structure may consist of a simple vertical column, on which a unit equipped with the above-mentioned film feed means (with rotary platform) slides in both directions, or may have horizontal arms or prongs which rotate about the group of products (usually with fixed platform). 
     The film feed means in turn consist of a film reel, rotatably mounted on a vertical shaft, which is attached to a plate which forms part of a feed means support carriage. In addition to the reel, there is a plurality of rollers, again with vertical axes attached to the plate, designed to allow the tensioned film to be guided and fed towards the group of products. 
     As well as these elements, in the current wrapping machines the use of motor-driven pre-stretching units for the wrapping film is increasingly common, especially when cold-stretch films are used. This pre-stretching procedure allows an increase in the film stabilising effect with a proportional reduction in the weight of the film on each group of products wrapped. 
     In order to obtain correct stretching of the film fed, that is to say, without the film sliding around the rollers and, above all, without a significant contraction or lateral reduction in the film web (which cancels out the reduction in film weight), the use of at least one pair of motor-driven rollers, independent of one another, is necessary in order to allow different peripheral speeds, with the two rollers positioned very close to one another and a large angle for film winding around the two rollers. 
     These operating conditions, together with the existing structure of the feed means, mean that the film feed unit has a large number of rollers which are very close to one another on the drive carriage. This architecture, therefore, makes it difficult for the operator to load or insert the film (when the reel ends or if the film breaks), since the spaces between rollers are very limited and there is also sometimes a danger that the operator&#39;s fingers may be crushed when manually inserting the end of the film. 
     In an attempt to overcome these disadvantages, the manufacturers of these machines designed a first solution consisting of a carriage which supports the reel and the guide and pre-stretching rollers in a cantilever configuration, that is to say using only a support rod. This architecture partly solves the problem of loading the film in the rollers (one end of the rollers is free), but requires precision sizing of the single support part and extremely stiff rollers (since there is only one resting point) which considerably raises the cost of the machine, as well as complicating assembly. In addition, the transmission and roller speed adjustment parts (variable speed motors and pulley/gear units) are concentrated at one end of the rollers, making the longitudinal dimension of the roller carriage very large and the configuration of the mechanisms which transmit motion to the rollers complex. 
     In a second solution, the support carriage was split into a fixed part and a mobile part, that is to say, a part which turns about a horizontal or vertical pivot axis. This solution allows the operator to load the film, after turning the mobile part, by threading the end of the film into the free area of the fixed part. 
     However, the second solution also has disadvantages, due to the increased size and weight of the carriage, necessary in order to split it, with the consequent use of lifting parts suitable for this purpose, thus raising the cost of unit production. In this solution, the pre-stretching rollers must also be moved away from one another, and it is possible to reduce the winding angles, with the consequent risks that the quality of the pre-stretching operation may be lowered. 
     DISCLOSURE OF THE INVENTION 
     The aim of the present invention is, therefore, to overcome the above-mentioned disadvantages by providing a device for loading film which has an extremely compact structure, but which can be used at high speed and allows the operator to rapidly insert the end of the film between the pre-stretching rollers, whilst maintaining production levels similar to that of conventional machines. 
    
    
     The technical features of the present invention, in accordance with the above-mentioned aims, are set out in the claims herein and the advantages more clearly illustrated in the detailed description which follows, with reference to the accompanying drawings, which illustrate a preferred embodiment without limiting the scope of application, and in which: 
     FIG. 1 is a perspective view with some parts cut away to better illustrate others, of the device for loading film made in accordance with the present invention; 
     FIG. 2 is a top plan view of the device illustrated in FIG. 1; 
     FIG. 3 is a top plan view with some parts cut away to better illustrate others, of the device illustrated in the previous figures. 
    
    
     With reference to the accompanying drawings and in particular FIG. 1, the device disclosed is used to load film, in particular but without limiting the scope of its application, cold-stretch films, on machines for wrapping groups of products (of the known type and not illustrated). 
     The parts of these machines which form the subject matter of the present invention comprise a support frame  1  for the feed and preparation unit  2  for the film  3  (that is to say, a film  3  cold pre-stretching unit) to be wrapped around the group of products. 
     The unit  2  comprises a carriage  4  which supports a reel  5  of film  3  with vertical axis Z in such a way that it can rotate, and at least one pair of rollers  6  and  7  which rotate about their axes Z 1  and Z 2 , parallel with the axis Z of the reel  5 . 
     The two rollers  6  and  7  are designed to pre-stretch the film  3  and one end of the rollers is attached to the carriage  4  by means of a platform  8 . The two rollers  6  and  7  (see also FIGS. 2 and 3) are positioned relative to one another in such a way that they allow the passage of the film  3 , with width L, along a feed path defined by part of the corresponding outer circumference or contact surface  6   s  and  7   s.    
     The carriage  4  is also equipped with a guard  9  which covers the end of the pair of rollers  6  and  7  opposite the end attached to the platform  8 . This guard  9  covers each roller  6  and  7  in such a way that it defines a continuous through-channel C passing at least between the contact surfaces  6   s  and  7   s  of the rollers  6  and  7  for insertion of the film  3  between the contact surfaces, from the outside. 
     In order to form the above-mentioned channel C, there are two holes  10  and  11  passing through the guard  9  from the outside, at least at the opposite portions of the surfaces of the rollers  6  and  7  defining the above-mentioned surfaces  6   s  and  7   s  for contact with the film  3  to be pre-stretched. 
     More specifically with reference to the construction details, the guard  9  consists of at least two separate parts  9   a  and  9   b , each supporting and covering a relative roller  6  and  7 , defining another support platform for the rollers. In particular, the guard  9  defines an upper support platform for the carriage  4 , securing the rollers  6  and  7  on both sides. 
     In order to stiffen the guard  9  (so as to better secure the ends of the rollers  6  and  7 ), each part  9   a  and  9   b  of the guard is individually attached to the other platform  8  by its vertical portions  12  and  13  which cover part of each roller  6  and  7 . 
     Obviously, these parts  12  and  13  extend at the side of areas of the rollers  6  and  7  through which the film  3  does not pass. 
     As illustrated in FIGS. 1,  2  and  3 , a third part  14  of the guard  9  is envisaged, its structure similar to the other parts, which supports and covers the upper end of the third feed roller  15  for the film  3 , which feeds the latter towards the group of products to be wrapped, located close to the pair of rollers  6  and  7 . 
     Another particularly advantageous element of the device derives from the fact that each part  9   a ,  9   b  and  14  of the guard  9  has edges  17 ,  18  and  19  which are rounded in the direction of the relative roller  6 ,  7  and  15  and supported in such a way as to define a guide zone for the film  3  to be inserted between said rollers. This feature allows rapid insertion of the film  3 , preferably gathered in a bundle (not illustrated), from the top of the carriage and without any risk to the operator. 
     Another feature of the present device relates to the pair of rollers  6  and  7 , which consists of motor-driven rollers (with mechanisms of the known type, therefore not illustrated in detail). 
     The rotation of the motor-driven rollers is controlled by a microprocessor unit  16  (which is part of the machine control unit, of the known type, therefore not illustrated). 
     In operation, this solution leaves one end of each roller free of connecting mechanisms (as in conventional models). Said end can be used to connect the roller directly to the guard in a simple, compact fashion, instead of to the transmission. 
     The motor-driven rollers have frequency changers which, controlled by the above-mentioned microprocessor, allow the speed of the rollers to be adjusted with continuous variations in the film  3  pre-stretching value, without using mechanical elements or having to substitute pinions/gears. 
     A device structured in this way, therefore, fulfills the preset aims thanks to an extremely simple, compact structure and the use of motor-driven rollers which allow a reduction in the number of mechanical drive/speed change parts at the ends of the rollers. This particular feature of the motor-driven rollers allows the guard at the top of the rollers to be shaped so that it has a channel C for insertion of the film from the outside rapidly, safely and with easy manual operations. All of this is achieved while maintaining a stiffness of the structure suitable for the work performed by the carriage and for film pre-stretching requirements. 
     The carriage, therefore, has a reduced number of feed rollers, large angles for winding around the pre-stretching rollers (see FIGS. 2 and 3) and a much reduced distance between the latter, to prevent reduction of the lateral strip of the film during stretching. 
     The present invention may be subject to numerous modifications and variations, all encompassed by the design concept. Moreover, all components may be substituted with technically equivalent parts.