Abstract:
The invention relates to a low friction gliding plate designed to optimize the process of packing at least one compressible object, such as insulation material, in continuous foil. In addition the present invention relates to a method for using a low friction gliding plate in packaging at least one compressible object.

Description:
BACKGROUND 
     The invention relates to a low friction gliding plate designed to optimize the process of packing one or more compressible objects, such as insulation material. A conventional machine for packing one or more compressible objects into one larger packet usually uses a technique where the object(s) are gathered, compressed and subsequently directed into the wrapping foil forming one stack. In this way the wrapping foil is fitted tightly around the three sides of the packet. At the fourth end, the object(s) are being held in a compressed state by a set of spears. The wrapping foil is wrapped around the spears and sealed e.g. by welding where after the spears are removed. The latter will cause the compressed object(s) to expand so as to fill out the empty space left by the spears. 
     In the industry of insulation material it is of outmost importance that the cubic content of the packets is reduced to a minimum, enabling transportation of an increased number of packets per volume. By using the spears described, the volume of the packets is greater than desired, but can be compensated for by over-compressing the compressible objects. Hence, when the spears are removed, the compressed object(s) will expand into the space made by the over-compression. However, by using over-compression there is a risk that the material properties of the objects are damaged. 
     An additional problem with using spears is the friction forces existing between both the spears and the wrapping foil and the spears and the compressed objects. When the spears are removed both the wrapping foil and the compressed object(s) can be damaged due to the friction forces. 
     Further, it is quite common for the wrapping foil to have some kind of text or illustration printed onto it. Part of this print can be transferred to the spears when the spears and the wrapping foil slide against one another thereby inducing friction between the spears and the wrapping foil. If the individual objects have been pre-packed in a printed foil, part of this print will also be transferred to the spears, inducing additional friction again. Over time, there will thus be a continuous increase of friction between the spears and the foil and/or the objects. The problem with friction induced damages on foil and/or the compressed object(s) will merely grow as the print from the foil is transferred and accumulated on the spears. The only way to solve this problem is to clean the spears on a regular basis. However, this is time consuming and increases the down time of the packaging machine. 
     The conventional wrapping machine therefore leaves the problem of either damaging the product due to over-compression or wasting wrapping foil due to rewinding of the foil. In addition, there is the problem of friction induced damage to the product/wrapping foil. A device is needed, which would have minimum friction force towards the foil and/or the compressible object(s) and render over-compression of the compressible object(s) and rewinding of the wrapping foil superfluous. 
     SUMMARY 
     Embodiments of the present invention relate to methods, apparatus and systems for wrapping at least one compressible object in continuous foil. In one embodiment, the system comprises:
         wrapping means for wrapping at least a first side of said at least one compressible object whereby said continuous foil covers said first side and extends in a first direction parallel to said first side,   a low friction gliding plate,   wrapping means for wrapping at least a second side of said at least one compressible object by pushing said at least one compressible object towards said continuous foil and a low friction gliding plate whereby said second side of said at least one compressible object and said continuous foil are moved in a second direction parallel to said low friction gliding plate.       

     It is thereby possible to wrap the compressible object without having to perform an over compression in order to make space for a spear resulting in decompression when the spear is removed. This makes it possible to make smaller packages—which is a huge advantage both when it comes to transport storage and handling. 
     In an embodiment the low friction gliding plate is air lubricated. This is an especially advantageous way of obtaining a low fricton. 
     In another embodiment the surface material of said low friction gliding plate has a low friction. Such special surface material could be obtained by performing specific surface treatments such as coating or polishing. 
     In another embodiment said apparatus further comprises at least one compression plate for compressing said at least one compressible object prior to wrapping at least a first side of said at least one compressible object. The compression plate could be air lubricated. Thereby the sliding surface and the compression plate are incorporated in the same unit. 
     The invention further relates to methods of wrapping at least one compressible object in continuous foil, wherein in one embodiment a method comprises the steps of:
         wrapping at least a first side of said at least one compressible object whereby said continuous foil covers said first side and extends in a first direction parallel to said first side,   wrapping at least a second side of said at least one compressible object by pushing said at least one compressible object towards said continuous foil and a low friction gliding plate whereby said second side of said at least one compressible object and said continuous foil are moved in a second direction parallel to said low friction gliding plate.       

    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIGS. 1   a - b  illustrate a packing machine with a low friction gliding plate, in accordance with an embodiment of the invention. 
         FIGS. 2   a - f  illustrate different steps in the wrapping process using the low friction gliding plate, in accordance with an embodiment of the invention. 
         FIG. 3  illustrates an embodiment of the low friction gliding plate, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1   a  and  1   b  illustrate a packing machine  100  according to the present invention comprising a compression plate  101 , a surface table  103  on which one or more compressible objects  105  can be placed and a first top guide  107 , which insures that the compressible object(s)  105  are held on the surface table  103  during compression.  FIG. 1   a  illustrates the packing machine  100  prior to wrapping the compressible object(s)  105 , whereas  FIG. 1   b  illustrates the wrapping machine  100  post wrapping the compressible object(s)  105 . The compression plate  101 , the surface table  103  and the first top guide  107  may be air-lubricated. 
     The packing machine further comprises a lower roll of wrapping foil  109  extending below the surface table  103 , an upper roll of wrapping foil  111  extending above the first top guide  107 . The wrapping foils  109 ,  111  are kept tight by the tightening devices (not shown in the figure) ensuring that the foil  109 ,  111  is kept stretched for tight wrapping of the compressed object(s)  105 . 
     The wrapping foil  109 ,  111  can be of an elastic material, which may be stretchable in at least one direction. 
     The packing machine can be embodied with two rolls of wrapping foils. In another embodiment of the invention, only one roll of wrapping foil is utilized to wrap the compressible object(s)  105 . 
     The packing machine additionally comprises a transport surface  113  onto which the compressed object(s)  105  are transferred during the wrapping process. The machine further comprises a backstop  115  against which the compressible objects  105  are compressed. The compressed objects are held in place between the transport surface  113  and a second top guide  117 . The purpose of the second top guide  117  resembles the one of the first top guide  107 . Both top guides  107 ,  117  can be adjusted in a vertical direction to accommodate different sizes of compressible object(s)  105 . The vertical movement of the second top guide  117  is also used in wrapping the foil around the compressible object(s)  105 , which will be described later. The transport surface  113 , the stop arm  115  and the second top arm  117  may be air-lubricated. 
     The packing machine in  FIG. 1  further comprises a low friction gliding plate  119 , an upper welding bar  121  preferably situated between the low friction gliding plate  119  and the upper roll of wrapping foil  111 , and a lower welding bar  123  preferably situated such that vertically, the lower roll of wrapping foil  109  is on the same side of the lower welding bar  123 , as the upper roll of wrapping foil  111  is in relation to the upper welding bar  121 . The low friction of the gliding plate  119  is obtained by air-lubricating the plate. 
     In one embodiment of the invention, the upper welding bar  121  is mounted directly on the low friction gliding plate  119 . In another embodiment of the invention, the upper welding bar  121  is not attached to the low friction gliding plate  119  and the two objects can move independently of one another. 
       FIGS. 2   a - f  illustrate the different steps in the wrapping procedure in a side view perspective.  FIG. 2   a  shows the position of the compressible object(s)  105  before the wrapping process is initiated. Hereafter the compressible object(s)  105  are compressed by moving the compression plate  101  towards the backstop  115  positioned just behind the foil  109 ,  111 . The top guide  107  and the surface table  103  ensure that the compressible object(s)  105  do not leave the packing machine  100  during compression. 
     In  FIG. 2   b , the now compressed compressible object(s)  105  are led into and wrapped in the foil  109 ,  111 . The compressed state of the compressible object(s)  105  is maintained by keeping them compressed between the backstop  115  and the compression plate  101 . Leading the compressible object(s)  105  into the foil  109 ,  111  is enabled by a coordinated movement of the compression plate  101  and the backstop  115 . Hereby the compressible objects are moved from the surface table  103  to the transport surface  113  and the wrapping foil  109 ,  111  is wrapped around the three sides  201 ,  203  and  205  of the compressed object(s)  105 . The top guides  107 ,  117  ensure that the compressed object(s) stay on the surface table  103  and the transport surface  113 , respectively. This movement of the compressible object(s)  105  stops when the compression plate  101  aligns approximately with the gliding plate  119  (see  FIG. 2   c ). 
       FIG. 2   d  illustrates the next step in the wrapping process, where the wrapping foil  109 ,  111  is wrapped along the fourth side  207 . The wrapping foil  109 ,  111  is wrapped around the fourth side  207  of the compressed object(s)  105  by moving the transport surface  113 , the backstop  115  and the second top guide  117  upwards. During this movement the fourth and unwrapped end  207  of the compressed object(s)  105  is moved from the compression plate  101  and up and along the low friction gliding plate  119 . This means that the compression force exerted by the compression plate  101  is transferred to and maintained by the low friction gliding plate  119 . In this process, the upper roll of wrapping foil  111  is located between the low friction gliding plate  119  and the fourth end  207  of the compressed object(s)  105 . 
     As illustrated in  FIG. 2   e , the two foils  109 ,  111  subsequently meet at the bottom of the compressed object(s)  105 , i.e. at the corner where the sides  201  and  207  meet. Hereafter the two welding bars  121 ,  123  are moved together with the wrapping foil  109 ,  111  lying in between the welding bars  121 ,  123 . The two knifes  121 ,  123  melt the foil together and subsequently cut the foil in two, whereby the compressed object(s)  105  are packed. 
     After completing the wrapping of the compressible object(s)  105 , the transport surface  113  with the wrapped compressed object(s)  105 , and the second top plate  117  are moved downwards returning to their first position as shown in  FIG. 2   a . The melting knives  121 ,  123  likewise return to their first position. By turning the backstop  115  to a horizontal position, the wrapped compressed object(s)  105  are moved along the transport surface  113  in a direction away from the surface table  103 . 
       FIG. 3  illustrates one embodiment of the low friction gliding plate  119  seen in detail in a front view. The low friction gliding plate  119  is air-lubricated by means of a number of openings, nozzles, or jets  301  positioned on the plate. The shape, the number and the distance between the openings  301  may be as illustrated in the figure with circular openings equally laid out horizontally and vertically, but could equally well vary both in shape, number and the way they are laid out both horizontally and vertically. For instance, instead of circular openings, rectangular openings may be used. The low friction properties of the low friction gliding plate  119  could also be obtained by having a surface with a low roughness, which will increase its gliding properties. Such a low roughness surface can optionally be combined with the described air-lubrication. 
     REFERENCES 
     
         
           100 : Wrapping machine 
           101 : Compression plate 
           103 : Surface table 
           105 : One or more compressible objects 
           107 : First top guide 
           109 : First roll of wrapping foil 
           111 : Second roll of wrapping foil 
           113 : Transport surface 
           115 : Backstop 
           117 : Second top guide 
           119 : Low friction gliding plate 
           121 : Upper welding bar 
           123 : Lower welding bar 
           201 : Bottom side of the packet of compressed object(s) 
           203 : Rear end side of the packet of compressed object(s) 
           205 : Top side of the packet of compressed object(s) 
           207 : Front end side of the packet of compressed object(s) 
           301 : Openings, nozzles or jets