Abstract:
Air cell dunnage is disclosed which collapses for shipment and is constructed to be subsequently inflated for use. The air cell dunnage is a bubble sheet containing a multiplicity of gas cells and a base layer fused to the bubble layer. The bubble layer further includes conduits interconnecting selected groups of the selected cells and a common channel extending longitudinally on the sheet in fluid communication with each of the selected groups. The conduits provide access to selected groups of gas cells for collapsing and inflating the cells for shipment and use, respectively.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a division of pending U.S. patent application Ser. No. 09/296,363 filed Apr. 22, 1999, the specification of which is hereby incorporated herein by reference in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to air cell dunnage and, more particularly, to air cell dunnage which is intended to be inflated at the time of use.  
           [0003]    Air cell dunnage is typically used for shipping products which may be subject to breakage. The dunnage may be wrapped around the product or stuffed into a container to prevent movement of the product within the container during shipment and to protect against shock.  
           [0004]    Conventionally, manufacturing air cell dunnage involves vacuum forming a multiplicity of bubbles to form a bubble layer. The bubbles are separated by flats which are bonded (thermally) to a flat base layer to form a bubble sheet in which air is trapped within the hemispherical vacuum formed bubble. This bubble sheet or air cell dunnage as it is commonly known, is shipped in this form to end users who use the dunnage to package their products for shipment.  
           [0005]    The manufactured bubble sheet is relatively bulky, being close to 100 times the thickness of the combined thickness of the plastic film from which the bubble sheet is manufactured. Obviously, this bulk increases the cost of shipping of the manufactured air cell dunnage to the ultimate end user.  
           [0006]    Moreover, the manufacture of the bubble sheet takes place at relatively high temperature (for example, about 20 E c). After the base layer is fused to the bubble layer, the temperature of the bubble sheet drops to room temperature which is approximately 20 E c. Because of this drop in temperature, the volume of the air within the individual bubbles or cells decreases by about 25%. Using these figures, this would mean that only about 75% of the available volume of a bubble is being used. It can be shown that when 75% of the available volume of a bubble is used, the height of the bubble is only 56% of the height of a fully inflated bubble. This means that if the individual bubbles could be expanded to their full size, the bulkiness (thickness) of the product would be almost doubled. Conversely, to achieve the bulkiness of a prior art bubble sheet in which the bubbles are only expanded to 75% of their volume, a fully expanded bubble sheet would require 44% less raw material. Thus, it is desirable to increase the percentage of the available volume of the bubbles which is filled with air.  
           [0007]    The main object of this invention is to provide air cell dunnage which can be inflated by the end user, which means that the manufactured product is much less bulky than before and which also enables the individual bubbles to be filled with a greater volume of air.  
           [0008]    A further object of the invention is to provide air cell dunnage in which less material is required for a specified amount of bulkiness.  
         SUMMARY OF THE INVENTION  
         [0009]    In accordance with the invention, the individual cells of a bubble sheet are interconnected by a series of conduits which lead to atmosphere. When the bubble layer is fused to the base layer, the conduits function as a vent so that the fused bubble sheet can be flattened to evacuate the air within the bubble sheet. The flattened bubble sheet is shipped to the end user.  
           [0010]    The end user inflates the bubble sheets by connecting the conduits to an air supply. This will take place at room temperature which means that the individual cells or bubbles can be completely filled with air. After the bubble sheet has been inflated, the individual conduit(s) are sealed so that the captured air is retained within the bubble sheet which can then be used in conventional fashion. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]    [0011]FIG. 1 is a plan view of a bubble sheet in accordance with a preferred embodiment of the invention;  
         [0012]    [0012]FIG. 2 is a plan view of a bubble sheet showing a preferred mechanism for expelling air from the bubbles;  
         [0013]    [0013]FIG. 3 is a side sectional view along the line  3 - 3  of FIG. 1;  
         [0014]    [0014]FIG. 4 is a side sectional view along the line  4 - 4  of FIG. 2;  
         [0015]    [0015]FIG. 5 is a plan view showing schematically how the bubbles are inflated and, the conduits sealed; and  
         [0016]    [0016]FIG. 6 is a side sectional view along the line  6 - 6  of FIG. 5. 
     
    
     DETAILED DESCRIPTION  
       [0017]    [0017]FIG. 1 shows a bubble layer  10  in accordance with the invention after vacuum forming. A multiplicity of bubbles  12  are typically formed in a diagonal pattern which maximizes the number of bubbles in a given area. In accordance with the invention, in each “diagonal” row, the bubbles  12  are interconnected by means of conduits  14 . On one side of the sheet, i.e, the right hand side illustrated in FIG. 1, the conduits  14  lead to a channel  15  at the edge of the bubble layer  10 . Channel  15  can be used as an exhaust channel for deflating the bubbles and the conduits, and it can be accessed by the end user for the purpose of inflating the bubble sheet as described below.  
         [0018]    For purposes of explanation, the interconnected bubbles in a single row have been labeled in FIG. 1 with the letters A through Z, respectively, with the right hand bubbles indicated by the subscript  1  and the bubble in the left hand position of the same row by the subscript  5 . For example, a single diagonal row of interconnecting bubbles, contains bubbles A 1  through A 5 . Typically, the sheet  10  will be about 1.5 meters wide which means that a single diagonal row of bubbles may contain as many as sixty bubbles. The drawings are not intended to illustrate an actual bubble sheet but represent instead a schematic example for purposes of explanation.  
         [0019]    By way of example only, if the bubbles  12  are formed as one inch hemispheres, the conduits  14  may be semi-cylindrical forms about ⅛ inch in diameter and channel  15  about ¼ inch in diameter. They would also be vacuumed formed during the process of manufacturing the bubble layer. This would mean that the roller which contains the female hemispherical dies for forming the bubbles would also include comparable female semi-cylindrical dies for forming the conduits  14  and channel  15 . It is also contemplated that the conduits  14  and channel  15  may be formed in the base layer  16 , either in whole or in part.  
         [0020]    After the bubble layer shown in FIG. 1 has been formed, it is joined to a base layer  16  in conventional fashion to form a bubble sheet (FIGS. 2 and 3). The base layer  16  contacts the bubble layer only in those regions which are “flat”, i.e. the regions outside of the bubbles  12 , conduits  14  and channel  15 . Typically, layers  10  and  16  are thermally fused together.  
         [0021]    In accordance with the invention, after the bubble sheet has been formed, the bubbles are deflated so that the sheet can be shipped in a flattened condition. For this purpose, as shown in FIGS. 2 and 4, a pair of nip rollers  18  and  20  are provided. The axes of the nip rollers  18  and  20  are arrayed as shown in FIG. 2 so that they are perpendicular to the conduits  14  of each diagonal row of bubbles A, B, C, etc. The nip rollers  18  and  20  rotate in the direction of the arrows causing air to be expelled from each row of bubbles through the side channel  15  to atmosphere. Assuming that the bubble sheet moves in the direction of arrow  22  as it is produced, the bubbles shown to the left of the nip rollers  18  and  20  will be flattened and the bubbles on the right hand side will still contain air. It is desirable for the nip rollers  18  and  20  to be transverse to the conduits  14  to make sure that all of the air in a given bubble is expelled by the nip rollers. If the nip rollers were not transversed to conduits  14 , air could be trapped within the individual bubbles. The nip rollers  18  and  20  do not function to move the bubble sheet and provide only negligible resistance to the movement of the bubble sheet as it is produced.  
         [0022]    The flattened bubble sheet, as indicated above, may be approximately 100 times thinner than the inflated bubble sheet. Because of this enormous reduction in bulk, the cost of transporting and storing the bubble sheet is greatly reduced.  
         [0023]    After the deflated bubble sheet has been shipped, it is necessary to inflate the bubble sheet so that it can be used. For this purpose, apparatus of the type shown schematically in FIG. 5 can be employed. The apparatus includes a nozzle  30  having an exterior blade  32  which includes a cutting edge  34 , and a heat sealing arrangement which includes two rollers  36  and  38  (FIG. 6). As shown the nozzle  30  is tapered with its wider portion sealing the channel  15  so that air from the nozzle cannot escape.  
         [0024]    The flattened bubble sheet typically will be shipped in the form of a large roll as shown at the bottom of FIG. 5 at  39  and will be unwound in the direction of arrow  40  using conventional rollers (not shown). The nozzle  30  is inserted into the leading edge of channel  15 . Nozzle  30  provides air under pressure which inflates each of the diagonally interconnected rows of bubbles A, B, C, etc. as the bubble sheet is unrolled. The heat sealing process requires the application of heat and pressure to the plastic bubble sheet in the areas of the conduits  14 . For this purpose, the upper roller  36  may include a multiplicity of cavities  42  which conform generally to the shapes of the individual air bubbles. The lower roller  38 , on the other hand, may be cylindrical in shape with heating wires embedded in the surface of the cylinder to raise the temperature of the plastic sheet to a temperature at which fusion will occur under the pressure applied by the two rollers. The heating wire will trace a path as shown by the dotted lines  44  which ensures that the high temperature is not applied directly to the bubbles and also that the seal at the conduits  14  is generally transverse to the individual conduits.  
         [0025]    The heat sealing rollers  36  and  38  are arranged to seal the bubbles after an entire diagonal row has been inflated. For example, as shown in FIG. 5, the heat sealing rollers must not seal the conduit  14  between bubble E 1  and channel  15  until all of the bubbles E 1 -E 5  have been inflated because after that seal has been made, it is no longer possible to provide air to the remaining bubbles in the diagonal line which has been sealed. After the conduit  14  between bubble E 1  and channel  15  is sealed, as the sheet continues to move in the direction of arrow  40 , the conduit  14  between bubbles E 1  and E 2  is sealed and so forth until finally the conduit between bubble E 4  and E 5  is sealed. At this point, each of the bubbles E 1 -E 5  is independent of the remaining bubbles.  
         [0026]    The same procedure, of course, applies to each successive diagonal row of bubbles. When the leading bubble of each row, e.g. bubble C 1 , reaches the blade  32 , cutting edge  34  cuts the channel  15  so that the inflated bubble sheet can be separated from the nozzle  30  for use in conventional fashion. Because the nozzle  30  fits tightly within the channel  15  it is still possible to expand the bubbles through the unsevered portion of channel  15  below the outlet of nozzle  30 .  
         [0027]    Other arrangements of the conduits can be shown in addition to what is illustrated in FIGS. 1 and 2. It is not necessary that each diagonal row of bubbles be separately inflatable and any practical number of diagonal rows may be interconnected so that they can be simultaneously inflated.