Abstract:
Method and apparatus which facilitate the tearing of packing materials into desired lengths by pre-tearing them along the rows of perforations which are provided for that purpose. In the disclosed embodiments, a preconfigured packing material having inflatable chambers separated by rows of perforations is fed at a predetermined speed in a direction generally perpendicular to the rows and periodically pulled upon rather abruptly to produce a partial tearing of the material along central portions of the rows of perforations.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of Invention  
         [0002]     This invention pertains generally to air-filled packing materials and, more particularly, to a method and apparatus for pre-tearing strings of such materials so they can be more readily separated into desired lengths for use.  
         [0003]     2. Related Art  
         [0004]     In recent years, air-filled packing materials have come into wide use as a cushioning material or void filler in shipping cartons and the like.  
         [0005]     One of the advantages of such materials is that they can be made from a preconfigured film material which is shipped and stored in a relatively compact form, typically on rolls or folded in boxes, and not inflated until it is at or near the point of use.  
         [0006]     The inflated film material is usually discharged from the machine which inflates it in the form of a continuous string of cushions with lines of perforations between the cushions so that the material can be torn into desired lengths.  
         [0007]     One problem with such materials is that if the perforated areas are made strong enough to get through the machines, it may be difficult to tear the cushions apart.  
       OBJECTS AND SUMMARY OF THE INVENTION  
       [0008]     It is, in general, an object of the invention to provide a new and improved method and apparatus for making air-filled packing materials.  
         [0009]     Another object of the invention is to provide a method and apparatus of the above character which facilitate the tearing of perforated materials into desired lengths.  
         [0010]     These and other objects are achieved in accordance with the invention by providing a method and apparatus which facilitate the tearing of packing materials into desired lengths by pre-tearing them along the rows of perforations which are provided for that purpose. In the disclosed embodiments, a packing material having inflated chambers separated by rows of perforations is fed at a predetermined speed in a direction generally perpendicular to the rows and periodically pulled upon rather abruptly to produce a partial tearing of the material along the rows of perforations. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is an isometric view of one embodiment of a system for pre-tearing and inflating strings of air-filled packing cushions in accordance with the invention.  
         [0012]      FIG. 2  is a perspective view of the machine which inflates and seals the film material in the embodiment of  FIG. 1 .  
         [0013]      FIG. 3  is top plan view, partly broken away, of the preconfigured film material which is pre-torn and inflated in the embodiment of  FIG. 1 .  
         [0014]      FIG. 4  is a fragmentary isometric view of the embodiment of  FIG. 1 , with the covers of the pre-tear unit removed.  
         [0015]      FIG. 5  is a fragmentary elevational view of the pre-tear mechanism in the embodiment of  FIG. 1 .  
         [0016]      FIG. 6  is an isometric view of the drive mechanism of the pre-tear unit in the embodiment of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0017]     In the drawings, the invention is illustrated in connection with a system which includes a machine  11  for inflating and sealing a preconfigured film material  12  to form strings of air-filled packing cushions  13 . The system also includes a bin  14  positioned to receive the strings of cushions from the machine, and a dispensing head  16  through which the strings of cushions are withdrawn from the bin  
         [0018]     The inflating and sealing machine can, for example, be of the type shown in U.S. Pat. No. 6,582,800, the disclosure of which is incorporated herein by reference. This machine has a base plate  17  which is adapted to rest on a table top or bench, and a generally rectangular enclosure housing  18  mounted on the base plate. The material is fed through the machine by a pair of traveling belts  19  which are trained about drive rollers  21 , take-up rollers  22  and guide rollers  23 - 26 . The belts are positioned on opposite sides of the path of the film material, with only the upper belt being visible in  FIG. 2 . The lower belt is identical to the upper one, but inverted so that the two belts are positioned symmetrically about the film path.  
         [0019]     Air is injected into the material before it reaches the belts by an inflation tube  27  which extends in a generally horizontal direction near the front wall of the housing. Air is supplied to the inflation tube at a pressure on the order of 3 psi by a pump located within the housing and discharged into the film material through a plurality of openings (not shown) in the side wall of the tube. A knife blade (not shown) is provided for slitting the film material along the inflation tube after the material is inflated and sealed to permit the material to separate from the tube.  
         [0020]     Heater blocks  28  are positioned adjacent to the belts on both sides of the film path for applying heat to the material through the belts to seal the material after it is inflated. The heater blocks are movable between a rest position away from the belts and a sealing position against the belts. They are urged together toward the sealing position by springs  29 , and are moved apart by a cam mechanism (not shown).  
         [0021]     Covers  31 ,  32  on the front wall of the housing enclose the belts, rollers and heater blocks and thereby protect the operator as well as keeping the film material away from the sides of the heater blocks. In the embodiment illustrated, upper cover  31  is formed as an integral part of the housing, and has a transparent window  33  in its outer wall. The two covers are spaced apart to form an opening  34  through which the edge portion of the film material can pass as the material travels along the inflation tube and between the belts.  
         [0022]     An opening  36  is formed in the lower corner of the window and the upper corner of the lower cover to facilitate insertion of the material into the machine, and a knife  37  is mounted on the upper cover for trimming the corner off the film material to make it easier to thread the material onto the inflation tube.  
         [0023]     As illustrated in  FIG. 3 , the film material  11  is in the form of an elongated length of flattened plastic tubing  39 , such as polyethylene, with rows of perforations  41  extending transversely across the tubing from one edge to the other. Between the rows of perforations, the two layers  43 ,  44  of the flattened tubing are sealed together along lines  46 ,  47  which extend from one edge  48  of the tubing in a direction generally parallel to the perforations and terminate a short distance from the second edge  49 . Each pair of seal lines  46 ,  47  defines an air chamber  51  which has an open mouth  52  that communicates with a longitudinally extending inflation channel  53  which is formed between the ends of the seals and the second edge of the material. A similar material is shown in U.S. Pat. No. 6,582,800.  
         [0024]     The film material is wound into a supply roll  56  which is mounted on a mandrel or spindle  57  for rotation about a horizontally extending axis above and to one side of the inflating and sealing machine.  
         [0025]     A pre-tear unit  59  is positioned between the supply roll and the inflation and sealing machine for tearing the material along the central portions of the rows of perforations before it is inflated and sealed. The pre-tear unit is enclosed in a housing  61  which has a pair of removable covers  62  on opposite sides of the film material.  
         [0026]     As best seen in  FIG. 5 , the pre-tear unit includes a pair of horizontally extending input guides  63 ,  64  positioned on opposite sides of the film material, a pair of feed rollers  66 ,  67  which draw the material from the supply roll, and a pair of tear rollers  68 ,  69  which receive the material from the feed rollers.  
         [0027]     The feed rollers engage opposite sides of the film material and are driven in unison by a pair of gears  71 ,  72  mounted on roller shafts  73 ,  74 . Tear rollers  68 ,  69  also engage opposite sides of the film material and are driven in unison by gears  76 ,  77  mounted on their shafts  78 ,  79 . The rollers are driven by a drive motor  81  which is connected to the shaft of tear roller  68  and a drive chain  82  trained about sprockets  83 ,  84  affixed to drive gears  71 ,  76 . The sprockets are sized such that the tear rollers turn somewhat faster than the feed rollers, and in one present embodiment, sprocket  83  has 30 teeth, sprocket  84  has 24 teeth, and the tear rollers rotate about 25 percent faster than the feed rollers.  
         [0028]     Tear roller  69  has an interrupted surface with flat sections  86  spaced in quadrature between arcuate sections  87 . This roller is thus adapted to engage the film material and pull upon it on an intermittent or periodic basis. Because the tear rollers are traveling substantially faster than the feed rollers, the pull is a rather abrupt one which tears the material apart along the rows of perforations. The rollers engage a central portion of the material, midway between edges  48 ,  49 , and hence the tearing occurs in the central portions of the rows of perforations, resulting in laterally extending slots or gaps  89  between the cushion chambers.  
         [0029]     The material emerging from the tear rollers is trained about a horizontally extending bar  91  affixed to a switch arm  92  which pivots about a pin  93 . It then passes over a guide rod  94  to inflating and sealing machine  11 . A magnet  96  is mounted on the switch, and the position of the arm is monitored by a sensor (not shown) which controls the operation of drive motor  81 , with the drive motor being turned off if the mater is not being pulled by the inflating and sealing machine.  
         [0030]     Dispensing head  16  has a generally rectangular frame  98  which is mounted in an elevated position on a post  99  next to bin  14 . A horizontally extending guide roller  101  is mounted on a bracket  102  toward the top of the post, and the dispensing head has a roller  103  mounted between the side rails  104 ,  106  of the frame and a plurality of elongated, flexible bristles  107  which extend from the upper rail  108  and terminate just above roller  103 .  
         [0031]     Operation and use of the system, and therein the method of the invention can now be described. The supply roll  56  of preconfigured film material is placed on mandrel  57 , and the free end of the material is threaded through pre-tear unit  59 . That unit then draws the material from the supply roll, and the free end of the material is trained about switch arm bar  91  and over guide rod  94 . It is then threaded onto the inflation tube  27  and engaged with belts  19  in the inflating and sealing machine. The pre-tear unit continues to draw the material from the supply roll, and the belts draw the material from the pre-tear unit and feed it through the machine. If the machine stops pulling the material, switch arm  92  will rotate in a counterclockwise direction, tripping the sensor which shuts of the drive motor in the pre-tear unit, which serves to regulate the speed of the material through the system.  
         [0032]     As the material passes through the pre-tear unit, feed rollers  66 ,  67  engage the central portion of the material continuously and feed the material at a substantially steady speed toward tear rollers  68 ,  69 . The tear rollers are traveling at a higher speed, and engage the material only intermittently or periodically. When they do, they exert a rather abrupt tug or pull on the central portion which tends to tear the in the central portions of the areas of weakness formed by the rows of perforations.  
         [0033]     The material is fed through the inflating and sealing machine with inflation tube  27  being received in the inflation channel  53  and air from the tube being injected through the open mouths  52  into chambers  51  to inflate the cushions. Heating elements  28  then form a longitudinally extending seal across the mouths of the chambers, thereby sealing the chambers to retain the air in them. After the cushions are inflated and the chambers are sealed, the material is slit along the inflation channel to permit it to separate from the inflation tube.  
         [0034]     The inflated cushions  13  are discharged into bin  14  in the form of a continuous string, and stored in the bin until they used. They are withdrawn from the bin, trained over roller  101 , and passed between the bristles  107  and roller  103  of dispensing head  16 . The bristles permit the cushions to be withdrawn from the bin without tearing apart if the string of them is pulled steadily. However, they also provide some resistance to the movement of the string such that the pre-torn cushions can be torn apart in desired numbers simply by snapping down on the string. That can be done with one hand, which is a significant improvement and advantage over the prior art where the cushions had to be grasped with both hands and torn laterally in order to separate them.  
         [0035]     The centrally located slots or openings produced by the pre-tear unit also have another advantage in that they allow the central portions of the cushions to be drawn in and rounded as they are inflated, which allows them to hold about 20 percent more air than they could without the slots.  
         [0036]     It is apparent from the foregoing that a new and improved method and apparatus for pre-tearing strings of air-filled packing materials have been provided. While only certain presently preferred embodiments have been described in detail, as will be apparent to those familiar with the art, certain changes and modifications can be made without departing from the scope of the invention as defined by the following claims.