Patent Publication Number: US-2006013918-A1

Title: Method and apparatus for manufacturing panel bodies of plastic material, and use thereof

Description:
The present invention relates to a method and apparatus for manufacturing panel bodies of plastic material, wherein the plastic material is injected into a mould cavity of a mould for the filling thereof, and a use of such a method and apparatus, as disclosed in the preamble of respective claim  1 , and claim  7 , and in claims  15  and  16 .  
      It is already known to mould panel bodies of plastic material, but where the material density more often than not causes such bodies to be disproportionately heavy when they have an essentially uniform thickness, e.g., several centimetres. At the same time, a disproportionately large amount of plastic material will be used in such bodies, making them disproportionately expensive.  
      The main object of the present invention is to overcome these known problems, and at the same time provide panel bodies which have the desired thickness as well as sufficient rigidity.  
      According to the invention, the method is characterised in that prior to the injection of the plastic material, strings, bars, tubes or netting of reinforcing material are placed in the mould in recessed portions of a first volume of the mould cavity, that the reinforcing material is held up at some points by pushers projecting up through the respective bottoms of the same recessed portions until the recessed portions have been filled with plastic material and surround the reinforcing material, that the pushers are withdrawn from the recessed portions and from support of the reinforcing material as the mould cavity expands to its second volume, and that after the injection of the plastic material the mould cavity is made to expand from a first volume to a second, larger volume, whilst the plastic material expands, the plastic material having added thereto a drive means compound, e.g., a foaming agent or a blowing agent, and that the moulded panel body is subsequently removed from the cavity of the mould.  
      According to the invention, the apparatus is characterised in that it has a means for locking the mould bottom in the first position until the first volume has been filled by plastic material to which a blowing agent has been added, that the mould bottom in a known way is designed to move into its second position whilst the plastic material expands, the panelflat body thus acquiring said second volume, that in the mould cavity, in connection with the first volume, there are provided recessed portions designed for the placement of reinforcing material of strips, bars, tubes or netting prior to the injection of the plastic material, that pushers are designed to movably project through the bottom of the respective recessed portions in order at some points to hold the reinforcing material up above the said bottom until the recessed portions have been filled with plastic material by its injection into the mould cavity and surround the reinforcing material, and that the pushers are designed to be withdrawn from the recessed portions and from supporting engagement with the reinforcing material as the mould cavity expands to its second volume.  
      Other embodiments of the method and apparatus will be set forth in the attached patent claims and in the following description with reference to the attached figures.  
      The invention can be used, e.g., for manufacturing panel bodies to be used as floor, wall or ceiling panels, or as shuttering or trim panels. 
    
    
       FIG. 1  is a vertical section through the apparatus according to the invention.  
       FIG. 2  is a second vertical section through the apparatus according to the invention. 
    
    
      Not all the reference numerals used in  FIGS. 1 and 2  will be described in detail in the description of the invention, but for the sake of order they are listed below so that a skilled person will more easily understand what each numeral refers to.  
      Thus, the description will essentially only relate to and include the reference numerals deemed to be necessary for understanding the basic principles of the inventive idea and the illustrated embodiment that is proposed according to the invention. However, it will be understood that structural changes could be made to the embodiment shown in  FIGS. 1 and 2  without thereby departing from the inventive idea.  
      The reference numerals shown in the drawings indicate the following elements as listed in Table I below.  
                   TABLE I                          1   Guide pin       2   Seger ring       3   Guide bushing       4   Distance plate       5   Block cylinder       6   Screw       7   Screw       8   Screw       9   Spacer bolt       10   Guide sleeve       11   Screw       12   Pressure cylinder       13   Seger ring       14   Flanged bearing       15   Positioning dowel       16   Guide cylinder       17   Sleeve       18   Pipe plug       19   Pipe plug       20   Spiral spring       21   Pusher       22   Pressure cylinder       23   Seger ring       24   Screw       25   Slide bar       26   Adjustment screw       27   Screw       28   Backing plate       29   Spacer sleeve       30   Pressure pad       31   Pusher plate       32   Screw       33   Pressure cylinder       34   Flanged bearing       35   Guide sleeve       36   Block cylinder       37   Screw       38   Moulding plate       38′   Edge       39   Mould component       40   Mould component       41   Moulding plate       42   Backing plate       43   Mould component       44   Insulating washer       45   Screw       46   Heating cartridge       47   Screw       48   Heating cartridge       49   Hinge bolt       50   Screw       51   Lever arm       52   Hinge bolt       53   Block cylinder       54   Screw       55   Mould component       56   Bottom anchor bar       57   Pressure pad receiver       58   Mould component       59   Cavity in first volume       60   Reinforcement       60′   Recessed portion       61   Pipe plug       62   Jaws       63   Screw       64   Distance plate       65   Hose nipple       66   Screw       67   Elbow       68   Insulating washer       69   Heating cartridge       70   Mouthpiece       71   Heating cartridge       72   Pipe plug       73   Jaws       74   Spacer bolt       75   Distance plate       76   Block cylinder       77   Screw       78   Core pins       79   Screw       80   Heating flue block       81   Screw       82   Heating flue block       83   Nozzle       84   Guide sleeve       85   Needle piston       86   Lever arm       87   Screw       88   Hinge leaf       89   Washer       90   Screw       91   Shut-off pre nozzle       92   Screw       93   Screw       94   Thermosensor       95   Screw       96   Guide ring       97   Nozzle element       98   Inlet nozzle                  
 
      At the outset, the cavity  59  is given a first volume V 1 , the space between the moulding plate  41  and the mould components  39 ,  40 ,  43 ,  55  and  58  that form at least a part of the bottom of the cavity being D 1 , e.g., 8 mm.  
      Plastic material containing a drive means is injected into the cavity  59  via nozzle  83 ,  87 . This drive means may be a foaming agent or a blowing agent to enable the plastic material introduced into the cavity  59  to expand.  
      As soon as the cavity having volume V 1  has been filled with this plastic material, a slide bar  25  having pressure pads  30  mounted thereon, is made to move towards the right (in the figure) in that pressure is applied by the cylinder  5  which causes movement of the bolt  9  towards the right and thus the bar  25 , whereby these pressure pads  30  ultimately become aligned with pressure pad receivers  57  in a mould component anchor bar  56 . The bar will then move downwards until it reaches a backing plate  28 . By virtue of this downward movement, which is caused by the expansion of the plastic material, each of the mould components  39 ,  40 ,  43 ,  55  and  58  will ultimately come into contact with a respective edge  38 ′ of a moulding plate  38 , whereby the cavity  59  has simultaneously expanded to a volume V 2 , and where the distance between the moulding plate  41  and the mould components  39 ,  40 ,  43 ,  55  and  58  has now increased to D 2 . This means that a panel body is obtained which has a larger volume than the first injected volume amount of plastic material, the gas-forming compound (foaming or blowing agent) causing this change in volume.  
      Thus, a panel body is obtained which has substantially reduced weight, but nevertheless satisfactory strength, compared with a panel body filled with a volume amount of plastic material corresponding to a cavity volume V 2 .  
      Prior to the injection of the plastic material into the cavity  59 , strips, bars, tubes or netting of reinforcing material  60  can be placed in recessed portions  60 ′ of the first volume of the mould cavity, i.e., between the mould components  39 ,  40 ,  43 ,  55  and  58  when these are in an uppermost position. The reinforcing material  60  is held up at point-by point by pushers  21  projecting up through the respective bottoms of said recessed portions  60 ′ until the recessed portions have been filled with plastic material surrounding the reinforcing material whilst the cavity  59  still has its first volume V 1 . The pushers  21  are then withdrawn from the recessed portions and thus from support of the reinforcing material as the mould cavity expands to its second volume V 2 . This withdrawal of the pushers, i.e., a downwards movement, may take place by applying vacuum to an underside of the spring-loaded (spring  20 ) underside of the pusher  21  by connection to a pipe plug  19 .  
      When the tops of the mould components  39 ,  40 ,  43 ,  55  and  58  reach the level of the bottom of the portion  60 ′, the downward movement of the components ceases, and the moulded, volume-expanded completed element (not shown) will thus be given a planar top face and bottom face, whilst reinforcing material may be embedded therein or optionally wholly or partly dispensed with. In many cases, it may however be highly desirable to have such reinforcing material  60  embedded in the panel body in order to increase its total rigidity. The reinforcing material  60  will be completely surrounded by the expanded plastic material.  
      When the moulded shaped body is to be removed from the mould, the moulding plate  41  is removed, or swung to the side, e.g., about the pin  1 , whereupon pressure can be applied to the pipe plug  19 , thereby causing the panel to be ejected from the mould.  
      It is also possible to cause the slide bar  25  that is mounted on the pressure pads  30  to move towards the left (in the figure), whereby these pressure pads  30  gradually come to lie sideways relative to the pressure pad receivers  57  in the mould component anchor bar  56  and support the last-mentioned, so that the components  39 ,  40 ,  43 ,  55  and  58  return to their upper position as shown in  FIG. 1 .  
      In a preferred, but for the invention by no means limited embodiment, D 1 =8 mm and D 2 =28 mm, which means that the recessed portion  60 ′ is 20 mm deep.  
      Advantageously, the plastic material is a polyolefin material, e.g., polyethylene or polypropylene. It may be expedient to add a talcum to the plastic material.  
      The first volume V 1  may, e.g., be in the range of 10-60% of the second volume V 2 , preferably about 15-45%, and optionally more preferably about 27-30%.  
      Although it is shown that the bottom of the cavity may consist of several mould components  39 ,  40 ,  43 ,  55  and  58 , it will be understood that it is also possible for them to be made unitarily, which might be relevant if reinforcement is not to be embedded in the panel body.  
      On studying  FIG. 1  it will be seen that the components  39 ,  40 ,  43 ,  55  and  58  are basically individually movable, like the pushers  21 .  
      Such moulded panel bodies, with or without reinforcing material, will, e.g., be highly suitable as structural members for use in, e.g., covering floors, walls or ceilings, or optionally as shuttering panels. In one particular application, such panels are intended to be used for whole or partial internal lining of transport containers.