Abstract:
A device and method are disclosed for forming air filled cushions. The device includes a drive mechanism to move inflatable tubing through the apparatus, and an injector, optionally including an outlet, located continuously within, or within a portion of, the tubing. This arrangement can permit the formation of air filled cushions in a continuous stream. Also disclosed is a roll of plastic tubing that is sealed transversely at a succession of intervals, with each pair of seals stopping just short of a longitudinal center line of the tubing. Such tubing might be used in conjunction with the apparatus, the central gap between the seals allowing passage of the injector.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of provisional application 60/589,748 filed Jul. 20, 2004, the entire content of which is expressly incorporated herein by reference thereto. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to improvements in the manufacture of air filled cushions. In particular, although not exclusively, this invention relates to air cushions of thin-walled plastic sheet, which can be used as infill or cushioning in the packaging and transportation of fragile articles. 
         [0004]    2. Description of Related Art 
         [0005]    Conventionally, air filled cushions are manufactured from a roll of plastic tubing. A typical example of a method of manufacturing these cushions is described in International Patent Application WO 01/21391, incorporated by reference herein in its entirety. In this method the plastic tubing is drawn through the machine from a supply roll. The walls of the plastic tubing are separated by drawing the tubing over a separator member. Air is then injected into the space between the wall through a needle, which pierces one of the walls of the tube, the hole left by the needle later being isolated by a heat seal. This process requires careful coordination of the position of the separator member and the air injecting needle, and good control of the air injecting needle so that only one wall of the tubing is pierced. 
         [0006]    A different way of manufacturing air filled cushions is to pre-perforate the plastic tubing and blow air into the tube through the perforations. Again, this requires careful coordination of the position of the injection head and the plastic tubing. 
         [0007]    Both of these processes are stop-start processes, in that the movement of the plastic tubing through the machine must be halted whilst the cushion is filled. Other references disclosing such processes include U.S. Pat. Nos. 4,049,854, 3,868,285, 3,667,593, and 3,366,523, each of which is incorporated by reference herein in its entirety. The throughput rate of the machines is therefore limited. Furthermore, since both processes inject air into the cushions through relatively small holes, a high pressure air injection system, including an air compressor, can be required. 
         [0008]    Various attempts have been made to develop a continuous process for filling air cushions, but have been only partially successful, problems being encountered in a number of areas. The difficulty of injecting air into a moving cushion leads to problems with under and over inflation of the cushions. One solution to this has been to inject air into the cushion using high pressure bursts of air, but this requires a high pressure air injection system and a complex control system. Such systems are described in, for example, U.S. Pat. Nos. 4,017,351, 3,817,803, 6,582,800, 6,659,150, 6,209,286, 5,824,392, 6,410,119 and U.S. Patent Publication No. US 2003-0163976, each of which is incorporated by reference herein in its entirety. 
         [0009]    An additional problem relates to the heat sealing mechanism. When the machine must be stopped the heat sealer cools down, and when it is restarted the heat sealer takes a small amount of time to reach operating temperature, so that one or more air cushions can not be formed properly. 
         [0010]    Moreover, further difficulties are encountered in conventional machines, including difficulty of machine set-up, particularly in drawing the tubing into and through the machine. 
       SUMMARY OF THE INVENTION 
       [0011]    The purpose and advantages of the present invention will be set forth in and apparent from the description that follows, as well as will be learned by practice of the invention. Additional advantages of the invention will be realized and attained by the methods and systems particularly pointed out in the written description and claims hereof, as well as from the appended drawings. 
         [0012]    To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the invention includes a machine for the production of air filled cushions including a drive mechanism which is operative continuously to move plastic tubing through the machine along a predefined path, and an injector located in the predefined path disposed within the plastic tubing as the tubing is moved through the machine. 
         [0013]    In further accordance with the invention, the injector has an inlet and an outlet and the drive mechanism is operative to move the plastic tubing over the outlet of the injector, whereby air can be injected through the injector into the plastic tubing. In this way, relatively low pressure air can be used, allowing for the use of a simpler air delivery and/or control system. Preferably the pressure is less than 5 psi, and most conveniently a pressure of 1-2 psi is used. The injector can be provided with a single outlet, but preferably has two or more outlets, arranged around its periphery, each outlet being operative to inflate a portion of the plastic tubing. Preferably the injector is provided with a cutter, upstream of the inlet, to cut a surface of the plastic tubing, allowing the plastic tubing to pass around the inlet. 
         [0014]    In further accordance with the invention, the machine can be adapted for use with plastic tubing having two rows of transverse, parallel, welds, the welds of each row extending toward a longitudinal centerline of the tubing from a respective one of the side edges. Furthermore, a weld of one row can be generally co-linear with a weld of the other row, with an unwelded section between them. In use, the injector can be located generally within the unwelded section, whereby at least one outlet of the separator member can be operative to inflate portions of the plastic tubing defined by adjacent welds in each row. 
         [0015]    In further accordance with the invention, the machine can include a sealing mechanism. The sealing mechanism can be located downstream of the outlet so as to seal the plastic tubing longitudinally. Preferably the sealing mechanism is a heat sealer mechanism, which has an operating position in which it abuts the plastic tubing and a standby position in which it is removed from the plastic tubing and the heat sealer can be moved from the operating position to the standby position when the machine is stopped. In a preferred embodiment the heat sealer comprises at least two spaced elongate bars, which are preferably generally equal in length to the air filled cushions produced by the machine. This ensures a good seal can be achieved. 
         [0016]    In further accordance with the invention, the machine can further include a perforator. The perforator can be located downstream of the sealing mechanism, whereby the perforator is operative to perforate the plastic tubing longitudinally. Preferably the machine further comprises a barrier, upstream of the injector, which is operative to maintain portions of the tubing deflated. The machine can also include a pressure sensor which is operative to place an outlet in fluid communication with the inlet if the pressure in the injector becomes too high. The machine can be provided with further sensors and control mechanisms, such as a speed sensor and control and an inflation sensor and control. 
         [0017]    In accordance with another aspect of the invention, there is further provided a roll of tubing that is sealed transversely at a succession of spaced intervals along its length by pairs of seals, each seal extending in a line from a respective opposite edge of the plastic tubing to a short distance from the centre thereof. Preferably the seals have little or no significant longitudinal components. The tubing can be made of a plastic material, but can also be made at least in part from other materials such as paper that is sealed using an adhesive or other means. 
         [0018]    In further accordance with the invention, a method is provided of producing air filled cushions. The method includes providing a roll of tubing being sealed transversely at a succession of spaced intervals along its length, by pairs of seals, each seal extending in a line from a respective edge of the plastic tubing to a short distance from the centre thereof, continuously inflating the tubing between successive seals to form inflated cushions, and sealing the tube along at least one longitudinal line. Preferably, the tube is sealed along at least two longitudinal lines where each longitudinal seal extends across two transverse seals. 
         [0019]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention claimed. 
         [0020]    The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the method and system of the invention. Together with the description, the drawing serves to explain the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Preferred embodiments of the invention, selected by way of example, will now be described, with reference to the following drawings, in which: 
           [0022]      FIG. 1  shows schematically a perspective view of internal components of a machine suitable for the manufacture of air-filed cushions; 
           [0023]      FIG. 2  shows schematically a section view of the internal components of the machine during the manufacturing process; 
           [0024]      FIG. 3  shows schematically a section view of the internal components of the machine when opened to load or unload plastic tubing; 
           [0025]      FIG. 4  shows schematically a top view of the internal components of the machine during the manufacturing process; 
           [0026]      FIG. 5  shows schematically a portion of plastic tubing suitable for use in the machine; 
           [0027]      FIG. 6  shows schematically a rear view of the machine; and 
           [0028]      FIG. 7  shows schematically a second embodiment of the invention, having a more compact structure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. The method and corresponding steps of the invention will be described in conjunction with the detailed description of the system. 
         [0030]    The methods and systems presented herein may be used for providing packaging cushions for cushioning articles during shipment. For purpose of explanation and illustration, and not limitation, an exemplary embodiment of the system in accordance with the invention is shown in  FIG. 1  and is designated generally by reference character  10 . 
         [0031]    The internal components of a machine for the manufacture of gas-filled (preferably air-filled) cushions is illustrated in  FIG. 1 . The machine  10  comprises an air barrier  11 , an injector  12 , heat sealers  14 , and pull rollers or drive rollers  16 , which incorporate a perforator  18 . These components of the machine  10  define a path along which tubular film passes through the machine  10 . 
         [0032]    A variety of materials can be used for the film material. Most preferably, a plastic material of varying weights of polyethylene can be used. However, other types of plastic films can be used as desired, including metallized plastic films and the like. Moreover, other materials such as paper based films can also be used that are sealed with adhesive material, or paper films having a thin polyethylene coating to facilitate sealing can also be used. 
         [0033]    As depicted herein, the air barrier  11  is disposed upstream of the injector  12  and includes two tracked belts. These belts are preferably made from spongy, rubberized tracking material. The injector  12  comprises an elongate hollow tube having an air inlet  20  and a plurality of outlets  22 . At its upstream end it has a smooth rounded tip  24 . The outlets  22  are disposed close to the tip  24  and comprise a pair of elongate slits which are disposed diametrically opposite from each other on the circumference of the injector  12 . 
         [0034]    In further accordance with the invention, as depicted herein, heat sealers  14  are disposed downstream of the injector, adjacent to the outlets. Since heat sealers  14  are identical, only one heat sealer will be described. As depicted herein, for purposes of illustration and not limitation, heat sealer  14  includes two belts  40 , each belt  40  arranged around four wheels: a drive wheel  42 , a tensioner wheel  44  and two idler wheels  46 ,  48 . The two belts  40  run parallel and adjacent to each other between the idler wheels  46 ,  48  and between them define a path through which the plastic tubing is drawn. Four heat sealing blocks  50 ,  52 ,  54 ,  56  are disposed along this portion of the belts arranged in pairs of blocks of which one is positioned above and one is positioned below the belts. The upper upstream one of these blocks  50  is heated sufficiently to weld the plastic tubing together and all four blocks  50 ,  52 ,  54 ,  56  are spring loaded to press together and close the belts onto the plastic tubing, providing sufficient pressure to complete the seal. 
         [0035]    For purposes of illustration and not limitation, as embodied herein, the inlet  20  is a hollow tube, which is disposed downstream of the sealing rollers. Inlet  20  projects downwardly from the injector  12 . A cutter, preferably a knife  30 , is disposed at the upstream end of the inlet  20 , and projects diagonally between the inlet  20  and the injector  12 . It should be noted that a hot wire could be used instead of or in addition to a cutter. The inlet  20  also supports the machine  10 , being attached to a superstructure (not shown) which hold s the injector  12  in a fixed position in use. Various of the rollers and drive band wheels are also supported, being attached to the side of the machine by axles  60 ,  62 , as shown in  FIG. 4 . The pull rollers  16  are arranged just downstream of the inlet  20  and the injector  12 . The perforator  18  is arranged along the centerline of the machine  10 , to perforate between the seals produced by the heat sealers  14 . 
         [0036]    For purposes of illustration and not limitation, as embodied herein,  FIG. 2  illustrates the machine  10  in use, with polythene tubing being drawn through it.  FIG. 4  provides a top view of the air cushion production process. A tube  32  of polythene film, typically 400 mm wide, is provided. 
         [0037]    The tube  32  of film can be provided on a roll mounted on an unwind shaft as depicted, or can be supplied in fan-folded form in a box, as desired. Moreover, a support cradle can alternatively be used as depicted in WO 01/21391. Such a cradle can be advantageous in that a roll of film  32  can be placed thereon with a minimum of effort. Using a cantilevered unwind shaft can be disadvantageous to the extent that the roll of film  32  has to be further manipulated to fit it over the shaft. Merely requiring the roll to be placed on top of two rollers in a cradle arrangement minimizes the need to maneuver the roll, thereby minimizing the time required for an operator to hold the roll of film  32 . This results in a time savings, and, more importantly, reduces the chances for operator injury (particularly back strains) as rolls of film  32  can be quite heavy if they are large. 
         [0038]    The tubing, shown in  FIG. 5 , has two rows of transverse, parallel welds or seals,  34 ,  35 . The tube  32  can also be pre-perforated across its width, along the line of the transverse seals  34 ,  35 . The rows of seals  34 ,  35  extend toward a longitudinal centerline of the tubing  32  from a respective one of the side edges, a weld of one row  34  being generally co-linear with a weld of the other row  35 , and the rows of welds having an unwelded portion between them. 
         [0039]    As an alternative to perforations, score lines can additionally or alternatively be used to separate cushions from one another. Score lines can present the additional advantage that air leakage is minimized during inflation. Moreover, not having perforations across the inflation channel of the roll of film  32  can prevent the film from getting caught on the inflation tube, as it is known that perforations can cause such problems, thereby requiring the machine to be shut off, thereby reducing efficiency. Score lines can be formed on the roll of film  32  by mechanical deformation. More preferably, the score lines can be formed by way of laser scoring. Laser scoring is advantageous in that it permits precise control of the depth of the score line, permitting unprecedented flexibility and control on the amount of force needed to separate air filled cushions from one another. 
         [0040]    To load the polythene tubing  32  onto the machine, the air barrier  11  is lifted apart, as shown in  FIG. 3 , and the injector  12  is inserted into the tubing at the unwelded portion between the rows of the transverse seals  34 ,  35 . The upper halves of the heat sealers  14  can be pivoted into a standby position, as shown in  FIG. 3  so that the plastic tubing  32  can be drawn over the injector  12  and positioned between the pull rollers  16 . The polythene tubing  32  is drawn through the machine  10  by the tracks which make up the air barrier  11 , by the belts  40  of the heat sealers  14  and by the pull rollers  16 . The pull rollers  16  operate marginally more quickly than the rest of the machine which places the tubing  32  under tension, even to the extent where some slippage through the rest of the machine can occur. In normal operation the tubing  32  is continually drawn from the roll of film  32  through the air barrier  11  by its tracks. The two layers of the tubing  32  are separated in its central, unwelded portion on reaching the smooth, rounded tip  24  of the injector  12 . Air, at atmospheric pressure, enters the injector member  12  at the inlet  20  and is continually blown through the injector member to the outlets  22 . 
         [0041]    The presence of the air barrier  11  prevents excess upstream inflation. As the tubing  32  is drawn past the outlets  22  the portions of the tubing defined by adjacent welds  34 ,  35  in each row become inflated, as shown in  FIG. 2 . Since the injector  12  is disposed centrally in the tubing, with outlets  22  directed to either side, two portions, one at either side of the injector  12  are inflated as the tubing  32  is drawn over the outlets  22 . To encapsulate the air in each portion the open side of each portion is sealed by heat sealers  14 . These produce two longitudinal welds  36  which each join a pair of transverse welds  34 ,  35 , sealing off the inflated air cushions. The downstream sealing blocks  54 ,  56  compress the tubing over the longitudinal weld  36 , making it more secure. 
         [0042]    Once sealed the tubing  32  must pass the inlet  20  of the injector member. To allow the tubing to pass around this inlet  20  the lower face of the tubing  32  is slit as it passes the knife  30  disposed just upstream of the inlet. The pull rollers  16  draw the tubing toward the perforator  18 . The perforator  18  produces a row of perforations  38  in the centre of the bottom face of the tubing, between the longitudinal welds. These perforations allow the tubing to be separated longitudinally if desired. Alternatively, roll of film  32  can be provided with perforations pre-formed therein. 
         [0043]    Finished cushions  64 , supported by a cushion bed plate  66  are shown in  FIG. 6 , just before they leave the machine. This machine  10  has a much higher output rate than previous machines, both because it is able to run continually, and because it can produce two streams of air cushions at once. Since the air can be injected through relatively large outlets  22  there is no need for compressed air to be used. The machine,  10  is, therefore, simple to use, having just an on-off and a temperature control. Further controls, such as a speed control and an inflation control could be added to the system if desired. 
         [0044]    The machine  10  is able to produce air cushions which are joined together to form a matrix of cells. Since these cells are more difficult to force apart they are more effective at protecting packages with irregular shapes. Furthermore, since the machine  10  can inflate multiple cushions through one central tube it uses the plastic tubing more efficiently than previous machines and generates less waste. 
         [0045]    Although the machine  10  is designed to run continually it is sometimes necessary to stop it during a production run to maintain or repair the equipment. This can cause problems with the heat sealers  14 , since conventionally the heated block  52  has to be cooled, to prevent the tubing being melted, and thus, when production is restarted, there is a warm-up time before it becomes operationally effective, during which cushions are unsealed and lost. This machine provides a facility for such eventualities. A top half of the heat sealer  14  is defined by the upper belt  40 , its four wheels  42 ,  44 ,  46  and includes the upper heated sealing block  50  and the other upper sealing block  54 . This half of the heat sealer is pivotally mounted along the axis of drive wheel  42  so that it can be swung away from its operative position, in which the portion of the belt between the idler wheels abuts the plastic tubing, to a standby position in which the belt lies away from the plastic tubing. This means that, should the machine need to stop during a production run the upper upstream sealing block can remain hot, ideally being maintained at a somewhat lower, standby, temperature by a thermostat. When the machine  10  is restarted the top section of the heat sealer  14  is pivoted back into its operating position and, since the heated sealing block  52  is still hot the sealing process can be immediately continued without losing any cushions. 
         [0046]    A second embodiment will now be described only in as much as it differs from the first embodiment, the same reference numerals being used for the same parts. If desired the machine  10   a  can be made more compact, as shown in  FIG. 7 . The injector  12   a  has been shortened in this embodiment so that the inlet  20   a  projects downwards just downstream of the heat sealing blocks  50   a,    52   a,    54   a,    56   a.  Furthermore the pull rollers  16   a  form the driving element for the heat sealer belts  40   a,  the other wheels  42   a , 44   a , 46   a ,being idler wheels. The perforator  18   a  is thus arranged just downstream of the inlet  20   a.  Since the upper heat sealer  14   a  is still capable of pivoting to a standby position the perforator  18   a  is arranged on the lower pull roller  16   a.  Since the injector  12   a  is significantly shorter in this arrangement even less pressure is required to cause air to flow to the outlets  22   a,  making the machine  10   a  even more efficient to run. 
         [0047]    The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, can, separately, or in any combination of such features, be utilized for realizing the invention in diverse forms thereof. Such combinations extend to novel combinations of devices and methods expressly disclosed herein, alone or in combination with devices and references incorporated herein by reference. as provided below. The listings of these claims are provided on separate sheets as follows: