Patent Publication Number: US-2005132664-A1

Title: Device for feeding and cutting film in machines for conditioning products

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a unit for feeding and cutting film on machines for conditioning products, in particular products which mainly have a cylindrical or prismatic shape which are wrapped with heat-shrink material.  
      At present automatic machines of the above-mentioned type have an operating line basically equipped with stations for positioning products and forming predetermined groups of said products, followed, further downstream according to a direction of feed of the products, by stations for wrapping the groups in plasticized wrappers.  
      The intermediate positioning and forming stations are therefore designed to form predetermined groups of products and to transport them towards the wrapping stations.  
      Once wrapped, the group of products leaves the station and, by means of a conveyor line, reaches a packaging station where said wrapping process is completed. The plasticized wrapper, preferably made of heat-shrink film, is heated so that it tightly adheres to the group of products.  
      The product wrapping stations therefore have a system for supplying the film, which normally comes from a special feed and cutting station located below the product conveyor surface.  
      Therefore, this station is connected to suitable conveyor devices for bringing the film to the product conveyor surface, where the wrapper is formed by wrapping the film around the products.  
      A construction solution for such a film feed and cutting station is described in patent EP-491666.  
      Said solution involves a cutting unit with means for supporting and moving a knife consisting of a pair of chains, parallel and opposite one another, supporting the knife rigidly and on both sides, closed in a ring on a corresponding pair of gear wheels, one of which is motor-driven.  
      The pair of chains structured in this way allows continuous movement of the knife, through an almost oval path, cyclically bringing the knife into a position in which it makes contact with and cuts a piece of film.  
      In said solution, the cutting unit is located below the operating line where the products pass, and the conveyor devices comprise a motor-driven angled surface which, as indicated, supplies the wrapping station with film.  
      A second solution described in patent EP-581747, has a structure comprising a knife located immediately below the product conveyor surface and a set of film feed rollers located upstream of the knife relative to the direction of film feed.  
      To cut the film, the knife which extends transversally to the machine, is moved along a straight line, in both directions, basically acting like a guillotine on the film.  
      Said solutions were further modified to obtain effective “continuous cycle” operation in packaging and the machine is described in patent EP-839723.  
      In the latter solution, the device for feeding and cutting film has a pair of counter-rotating rollers between which the film passes.  
      The first roller in the pair has a knife projecting radially from the roller, whilst the second roller has a radial groove housing the knife during a cutting rotation.  
      However, the above-mentioned machines have some disadvantages in particular due to the positioning, relative to the rest of the machine, of the many components in the station and the consequent architecture of the devices which supply film to the wrapping station.  
      Since they must satisfy high parameters for synchronization with product feed on the operating line, such devices have a rather complex structure. Said structure must also guarantee a continuous supply of film to the subsequent stations, usually pushing the film upwards, since, as already indicated, they are normally located below the conveyor surface.  
      The complexity of the devices therefore means that their cost is high, placing such machines in a niche in the market reserved for those with proportionate investment budgets.  
     SUMMARY OF THE INVENTION  
      The aim of the invention is, therefore, to overcome the afore-mentioned disadvantages, with a device for feeding and cutting film in a machine for conditioning products which has a simple and economical structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The technical features of the present invention, in accordance with the aforesaid aims, may be clearly inferred from the claims herein, in particular claim  1  and, preferably, from any of the claims directly or indirectly dependent on claim  1 .  
      The advantages of the present invention are 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 schematic side view with some parts cut away to better illustrate others of a machine for conditioning products comprising a device made according to the present invention;  
       FIG. 2  is a schematic front view with some parts in cross-section of a detail of the device made according to the present invention;  
       FIG. 3  is a schematic side view with some parts cut away to better illustrate others of a different embodiment of the device made according to the present invention;  
       FIG. 4  is a schematic top plan view with some parts cut away for greater clarity of a detail of the machine illustrated in  FIG. 1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      With reference to the accompanying drawings, and in particular with reference to  FIG. 1 , the numeral  1  denotes a device for feeding and cuffing a continuous film  2  to a machine or line  3  for conditioning products  4 .  
      In particular, said machine  3 , in a generic standard configuration, comprises a station  5  for wrapping the products  4  and a station  6  for positioning and supplying the products  4  to the subsequent stations. Said stations  5  and  6  are basically of the known type and so are not described in further detail in this text.  
      The device  1  comprises a conveyor surface  7 , mobile in a direction V of feed, supporting the products  4  which normally have a base  4   a  on which they rest.  
      In particular with reference to  FIG. 1 , it can be seen how the device  1  comprises a single conveyor surface  7 , formed by the upper branch  8  of a belt  9  wound in a loop about a plurality of rollers  10  of which at least one is a driving roller and the others are driven rollers.  
      In greater detail, it may also be seen that the device  1  comprises a set of rollers  10   a  arranged in such a way that, extending as it does, the upper branch  8  forms a transversal slot  11  in the surface  7 , constituting a cutting line for the uses better described below. Said rollers  10   a  therefore form return means  10   a.    
      In embodiments not illustrated, the slot  11  may be formed by a succession of two conveyor surfaces with the respective rear and front ends opposite and at a distance from one another.  
      As is also shown in  FIG. 4 , at the conveyor surface  7 , and precisely the slot  11 , there is a knife  13  which is transversally mobile along the slot  11 . Basically, in the embodiment illustrated the knife  13  cuts transversally relative to the surface  7  or, in any case, transversally to the direction V of feed of the products  4 . In the particular embodiment illustrated, the knife  13  is “V”-shaped and has a double blade to allow the film to be cut in one direction and the other as it moves along the above-mentioned cutting line. Advantageously, in embodiments that are not illustrated, the knife  13  may have any shape and may even be substituted by a pair of knives, each with a single cutting edge and designed to cut the film  2  in one direction only, as described below.  
      In particular with reference to  FIG. 2 , it can be seen that the knife  13  is supported by a bracket  14  rigidly connected to a support  15  engaging, by means of a counter-support  16 , with a toothed belt  17  wound in a loop around a pair of pulleys  18 , only one of which is visible in the accompanying drawings.  
      The pulley  18  is connected to a motor M for moving the belt  17 , together with the knife  13 , transversally to the surface  7 , to form a piece  2   a  of film  2 .  
      A sliding element  19  supports the counter-support  16  and is slidably connected to a guide  20 , which is also consequently positioned transversally to the conveyor surface  7 .  
      Opposite the knife  13  there is a pair of pneumatic pistons  21 , visible in  FIGS. 1 and 3 , to hold the film  2  during the cutting operations, by means of a forked pad  21   a  which allows the knife  13  to pass. Advantageously, there may be any number of pistons  21  according to the machine  3  requirements and the size of the film  2  used to wrap the products  4 . As described, said pistons  21  constitute presser means.  
      With reference to  FIG. 1 , it may be seen that in the case illustrated the film  2  is wound in a reel  22 , located, in the particular configuration illustrated and by way of example only, below the surface  7 .  
      A motor-driven roller  23  is positioned at a tangent to the reel  22  and forms, as described in more detail below, film  2  unwinding means  24 .  
      During normal use, the film  2  unwound from the reel  22  according to an unwinding path S reaches the conveyor surface  7  through a slot  25  and is held on the surface  7  by the weight of the products  4 .  
      Said unwinding path S is formed by a plurality of guide rollers  26  for the film  2 . Three of these rollers  26  are illustrated, although advantageously there may be any number of them, according to the particular requirements of the machine  3 .  
      The device  1  also comprises a sonar  27  and a unit  28  for the emission of fluid, normally compressed air  29 , located downstream of the reel  22  according to the direction of unwinding S 1 , to prevent, as is clarified below, film  2  tensioning when the film  2  is unwound from the reel  22 , by the unwinding means  24  and the products  4  are fed on the conveyor surface  7  downstream of the slot  25  since the products  4  pull the film  2 , as described below.  
      In particular, the sonar  27  is designed to detect said tensioning and, by blowing an air jet  29 , the device  28  can form a loop  30  in the film  2 , so that it basically creates a film  2  reserve  31  along the unwinding path S.  
      The sonar  27  and the device  28  basically constitute safety means  32 . In embodiments not illustrated, such safety means  32  may comprise other devices of a substantially known type, all designed to form a film  2  reserve  31 .  
      The device  1  has sensor means  33  positioned along the film  2  unwinding path S to synchronize film  2  unwinding with product  4  feed. Said means  33  comprise a first photocell  34  aligned with the film  2 , located upstream of the slot  25  according to the direction of unwinding S 1 .  
      As described below, the photocell  34  synchronizes product  4  feed with the film  2  if the latter has a printed motif to be positioned relative to the products  4  when they are wrapped in a piece  2   a  of film.  
      In particular, in these cases the film  2  has a reference element identifiable by the photocell  34 , which may be the above-mentioned printed motif, a mark on the film  2  or any reference on the film  2 . The photocell  34  is slidably connected to a guide  35  and is mobile between a first position, corresponding to a minimum size of the piece  2   a  of film  2  which will be used to wrap the products  4  and a second position, illustrated with a dashed line in  FIG. 1 , corresponding to a maximum size of the piece  2   a  of film.  
      A second photocell  36  is located, at the conveyor surface  7 , downstream of the slot  25  and upstream of the knife  13  according to the direction V of product  4  feed. This second photocell  36  operates in conjunction with a separator element  37  of the positioning and supply station  6  to form a group  38  of products  4 , according to a substantially known method, not described in detail. The photocell  36  is mobile on a guide  39  between a position distanced from the knife  13  and a position substantially close to the knife  13 , illustrated with a dashed line in  FIG. 1 , so that it can form groups  38  consisting of a predetermined desired number of products (conditioning the groups of products).  
      The sensor means  33  also comprise a third photocell  40  located close to the conveyor surface  7 , downstream of the knife  13  and upstream of the wrapping station  5 , according to the direction V of feed, to establish the length of the piece  2   a  of film which will be used to wrap the group  38  of products  4  if the film  2  does not have any motif to be centered with the group  38  during wrapping. Hereinafter this type of film  2  is called “transparent”.  
      The photocell  40  is also mobile on a respective guide  41 , extending substantially parallel with the surface  7 , between a minimum size position, illustrated with a dashed line in  FIG. 1 , corresponding to a minimum measurement of the piece  2   a  of film  2  that will be used to wrap the products  4 , and a maximum size position, corresponding to a maximum measurement of the piece  2   a  of film.  
      Finally, the device  1  comprises a fourth photocell  42  located immediately upstream of the knife  13  and designed to confirm alignment of the products  4  with the cutting line.  
      In particular with reference to  FIG. 3 , it may be seen that the knife  13 , together with the bracket  14 , the support  15 , the counter-support  16 , the belt  17 , the pulleys  18 , the sliding element  19  and relative guide  20 , the pneumatic pistons  21 , the motor M and the return rollers  10   a  may be installed on a carriage  43 , mobile at the same speed as the surface  7 , along a respective guide  44  in the direction V of product feed, between a start of stroke position, where a cut in the film  2  begins, and an end of stroke position, not illustrated, where the cut ends.  
      As described below, this embodiment allows “continuous” use of the machine  3 , that is to say without interruption in the supply of products  4  to the wrapping station  5 .  
      Obviously, if knife  13  movement along paths not completely perpendicular to the surface  7  is required, different speeds V 1  and V 2  may be calculated, respectively for the carriage  43  and the surface  7  again to allow a transversal cut, but with different speeds and, therefore, machine  3  productivity.  
      Similarly (see  FIGS. 3 and 4 ), second presser means  100  may be used, acting on the film  2 , downstream of the first slot  25  relative to the direction V of feed, so that the film  2  can be held in place even when there are no products  4  on the surface  7 , for example for size change-overs in the groups of products  4  to be formed. These second presser  100  may consist, for example, of pistons  101  with end pads  102  which make contact with the film  2 .  
      In practice, starting with a generic operating configuration, at the positioning station  6  outfeed, the respective bases  4   a  of the products  4  make contact with the film as it reaches the conveyor surface  7  as they pass over the slot  25 .  
      The film  2  below is unwound from the reel  22  by the roller  23  and above, at the surface  7  level, is held and pulled by the products  4  resting on the surface  7 .  
      To avoid unwanted film  2  tensioning after product  4  feed on the surface  7 , each time it detects such tensioning, the sonar  27  activates the device  28 , which, by blowing on the film  2  unwound from the reel  22 , creates the reserve  31  in the form of the loop  30 .  
      If the film  2  has a printed motif on it, which must be suitably centered relative to the products  4  when packaging is complete, the photocell  34  synchronizes film  2  unwinding with product  4  feed on the surface  7 .  
      Simultaneously, the photocell  36  dedicated to sizing the groups  38 , activates the separator element  37  to form the group  38  with which the printed film  2  size unwound from the reel  22  is associated. In normal operating conditions, the group  38  stops in front of the cutting line and the photocell  42  confirms that alignment has been achieved.  
      In particular with reference to  FIG. 4 , the products  4  are fed beyond the cutting line, still pulling the continuous film  2 , until they reach a position where a trailing section  2   b  of film  2  which will form the piece  2   a  of film after the cut, substantially between the front  4   b  of the products  4  and the cutting line, is long enough to wrap the group  38  (advantageously the trailing section  2   b  is longer than the perimeter of the group of products  4  in the side view in  FIG. 1 ). Once the products  4  are positioned, the pistons  21  block the film relative to the knife  13  which cuts the film  2 , moving transversally to the surface  7 , forming the piece  2   a  of film. If the knife  13  is of the type with two blades, it will make the cut in direction T 1  and, for the next group  38  of products, a cut in the film  2  in direction T 2 , without having to return to a starting position at the end of each cut.  
      The products  4  together with the piece  2   a  of film are then fed towards the wrapping station  5 , where a plasticized wrapper is formed around the group  38  of products using known methods that are therefore not described.  
      If the film  2  is transparent, to form the piece  2   a  of film the photocell  40  will check the distance between the products  4  and the cutting line, and the film  2  is cut when the trailing section  2   b  of film  2  is long enough to wrap the group  38 .  
      In the device illustrated in  FIG. 3 , the film  2  is cut during a carriage  43  movement in the direction V of product feed. The carriage will move at a speed equal to that of the surface  7  so that the cutting line is relatively stationary relative to the products  4  and to the film  2  to be cut. The movement of the carriage will also be such that it allows carriage  43  repositioning in the start of stroke position when a new group  38  of products  4  arrives, pulling the film  2 , close to the cutting line.  
      The entire operation of the machine  3  is regulated by a control unit, not illustrated, which processes the signals arriving from the photocells described. The many adjustments and size variations may be simply performed by changing the position of the photocells or, in a more complex way, by operating on the machine  3  software programming.  
      The invention fulfils the preset aims. Positioning the knife at the conveyor surface, downstream of the slot from which the film arrives and upstream of the wrapping station according to the direction of product feed on the conveyor surface, the structure of the machine can be significantly simplified, since the film, simply unwound from the reel, is basically pulled towards the cutting line by the products themselves.  
      Moreover, the positioning of the photocells described allows the use of both printed film and transparent film and product size change-overs are simple to perform by manually positioning the photocells.  
      The invention described is suitable for evident industrial applications. It may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted by technically equivalent elements.