Abstract:
Apparatus for making gas-filled filling bodies includes a supply reel for storing a pre-fabricated half-tubular plastic film having an at least partially open border side and being divided into individual pockets by weld seams which extend transversally with respect to a transport direction of the plastic film. Positioned downstream of the reel and receiving the plastic film from the reel is a gas filling device for blowing air into the pockets. Positioned downstream of the gas filling device and receiving the plastic film from the gas filling device is a welding tool for welding the open border side of the plastic film for formation of closed filling bodies. The transport of the film through the apparatus is realized by a drive unit which applies a force upon the plastic film essentially downstream of the gas filling device, as viewed in the transport direction.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of prior filed U.S. provisional Application No. 60/956,284, filed Aug. 16, 2007, pursuant to 35 U.S.C. 119(e), the content of which is incorporated herein by reference in its entirety as if fully set forth herein. 
    
    
     This application also claims the priorities of German Patent Application, Serial No. 10 2006 045 793.5, filed Sep. 26, 2006, and European Patent Application 07113747.5, filed Aug. 2, 2007 pursuant to 35 U.S.C. 119( a )-( d ), the contents of which are incorporated herein by reference in its entirety as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     The present invention relates, in general, to an apparatus and method for making gas-filled filling bodies. 
     Nothing in the following discussion of the state of the art is to be construed as an admission of prior art. 
     Gas-filled-normally air-filled-filling bodies are increasingly used as filling material for transport of sensitive goods in particular. Compared to traditional filling materials for packaging purposes, like e.g. filling bodies of foamed plastic, gas-filled filling bodies can be produced, at the site where they are needed, from a half-tubular film mounted on a reel by “blowing up” the film so that the volume of the filling bodies increases by a multiple, typically at least by the factor  10  compared to the initial volume of the film reel. After use, air can easily be released again from the filling bodies so that the amount of waste is reduced, although recycling of the films is, of course, easily possible. 
     International publication no. WO 02/26589 A1 discloses a continuously operating filling apparatus for making such gas-filled filling bodies, wherein a pre-fabricated half-tubular film which is open on one side is moved past a gas filling device, deflected at an angle, and then welded under the action of a heated band of Teflon-coated steel via a welding runner. This apparatus is complex and requires substantial maintenance works as a result of the use of Teflon-coated steel. 
     German utility model no. DE 203 15 643 U discloses an apparatus for making gas-filled filling bodies, having a welding tool configured as welding runner which directly rests upon the film material. The half-tubular film is hereby transported by belts as well as guide wheels. The transport of film requires a fairly complex mechanism with several drive elements which must be precisely synchronized in order to prevent, at commencement of the filing operation, the half-tubular film, which still is made from upper and lower film portions loosely lying upon one another, from escaping the machine, or to prevent a crease formation between the upper and lower film portions, which would render an air-tight welding impossible. The respective drive devices with gear mechanisms are thus expensive, require relatively large installation space, and require a drive motor with relatively high power as a result of friction and gear losses. 
     It would therefore be desirable and advantageous to provide an improved apparatus and method for making gas-filled filling bodies to obviate prior art shortcomings. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, an apparatus for making gas-filled filling bodies includes a supply reel for storing a pre-fabricated half-tubular plastic film having an at least partially open border side and being divided into individual pockets by weld seams which extend transversally with respect to a transport direction of the plastic film, a gas filling device positioned downstream of the supply reel and receiving the plastic film from the supply reel for blowing air into the pockets, a welding tool positioned downstream of the gas filling device and receiving the plastic film from the gas filling device for welding the open border side of the plastic film for formation of closed filling bodies, a drive unit for moving the plastic film in the transport direction, with the drive unit applying a force upon the plastic film essentially downstream of the gas filling device, as viewed in the transport direction. 
     The present invention resolves prior art shortcomings by simplifying the drive for the transport of the plastic film by positioning the drive unit in the transport direction downstream of the gas filling device. 
     According to another feature of the present invention, the drive unit may be positioned downstream of the welding tool for effecting a transport of the plastic film in the transport direction. As a consequence, there is no need for transport belts or the like, and the drive unit can be greatly simplified and operated at reduced driving power. 
     According to another feature of the present invention, a braking mechanism may be provided for decelerating an unwinding of the plastic film from the supply reel so that the plastic film is held taut between the supply reel and the drive unit. In this way, air is prevented from escaping the pockets during advance of the plastic film through the gas filling device and downstream thereof. Operation of the brake mechanism may be triggered automatically or by hand. As a result of the provision of the brake mechanism, the respectively detached upper and lower film portions bear upon the gas filling device and thus prevent release of air and thereby reduce air losses. 
     Escape of injected air can also be prevented by implementing the welding operation as close as possible following the injection of air so that certain residual leaks do not significantly affect the filling degree of the filling bodies. According to another feature of the present invention, the drive unit may hereby be constructed to include two electric motor driven rollers which abut one another in a circumferential region and are each provided with a friction layer, and between which a border area of the plastic film is guided, as the plastic film moves in the transport direction. Suitably, the two rollers are disposed in offset relationship in horizontal direction. 
     According to another feature of the present invention, an upper one of the rollers is positioned in transport direction of the plastic film offset behind the lower one of the rollers, with the lower roller spatially following immediately the gas filling device. As a result, the plastic film can be deflected slantingly downwards at an angle of about 20° to 50° with respect to an imaginary extension of the horizontal transport path following the gas filling operation. Such an angular guidance prevents a migration of the film away from the transport direction as a result of warping caused during the blowing operation or a creasing between upper and lower film portions that would complicate the welding process. 
     The offset disposition of the rollers also allows the lower roller to form an abutment for the welding tool. As a result, the welding tool can be arranged immediately adjacent the gas filling device so that leaks upstream of the welding operation are minimized. The moved roller as abutment also realizes a superior quality of the weld seam. 
     As the plastic half tube is driven at only one area, with this drive operating in a section where the upper and lower film portions have already been welded, a reliable transport can be attained without warping between upper and lower film portions so that problems relating to the precise synchronization of different drive elements can be eliminated beforehand. 
     According to another feature of the present invention, air can be blown out slantingly from the gas filling device to define an air stream which has a movement component in transport direction of the plastic film and a movement component transversally to the transport direction. In this way, air is also prevented from escaping, after the plastic film is filled with gas and prior to the welding process. 
     According to another aspect of the present invention, a method of making gas-filled filling bodies includes the steps of unwinding from a supply reel a pre-fabricated half-tubular plastic film, which has an at least partly open border side and is divided into individual pockets by weld seams, continuously moving the plastic film past a gas filling device for blowing air into the pockets of the plastic film, and moving the plastic film past a welding tool for welding the open border side of the plastic film in an air-tight manner, wherein a transport of the plastic film is effected by a drive unit which applies a force upon the plastic film in transport direction downstream of the gas filling device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
         FIG. 1   a  shows a fragmentary schematic side view of an apparatus for making gas-filled bodies in accordance with the present invention; 
         FIG. 1   b  is a plan view of the apparatus of  FIG. 1   a;    
         FIG. 2  is a perspective illustration, in exploded view, of a reel holder for attachment of a supply reel; 
         FIG. 3  is a portion of a plastic film in a flat state; and 
         FIG. 4  is a portion of the plastic film in a filled state. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
     Turning now to the drawing, and in particular to  FIG. 1   a , there is shown a fragmentary schematic side view of an apparatus in accordance with the present invention, generally designated with reference numeral  10 , for making gas-filled filling bodies from a half-tubular film  40  made of plastic. A specific construction of such a plastic film  40  is fully described in international publication no. WO 02/26589 A1, the entire specification and drawings of which are expressly incorporated herein by reference. It will be appreciated by persons skilled in the art that  FIGS. 1   a ,  1   b  show only the relevant parts of the apparatus  10 , namely a gas filling device  16  for injecting air, a welding tool  18  for welding, and a drive unit  12 ,  14  for transport of the film  40 . Of course, the apparatus  10  contains much mechanical elements which do not appear in the foregoing figures. However, these elements are not part of the invention, and thus have been omitted from the figures for the sake of simplicity. 
     As shown in  FIG. 3 , the half-tubular film  40  has pairs of transverse weld seams  42  between which a perforation  44  is respectively provided. The transversal weld seams  42  end at a predefined distance from the open end of the half tube. Openings  46  in the intermediate space between the transversal weld seams  42  are provided for control of the apparatus  10 , in particular for recognizing the position of the weld seams  42  or for control of the film welding operation in dependence on the film material, or the film materials when multilayered films are involved, or the film thickness.  FIG. 3  shows the film  40  in a flat state when being rolled off a supply reel  54  ( FIG. 2 ) for transport through the apparatus  10 , whereas  FIG. 4  shows the film  40  in a gas-filled state. 
     The film  40  is preferably made through co-extrusion of two layers, e.g. an outer layer of thermally stable plastic (e.g. melting temperature of about 120 to 130° C) in confronting relationship to a lighter meltable thinner inner layer (melting point, e.g., about 85° C). The welding properties are hereby greatly improved. 
     The film  40  is supplied from the supply reel  54  which can be locked in fixed rotative engagement with respect to a reel holder  52 . Rotation of the reel holder  54  can be delayed by a brake mechanism whose strength can be automatically controlled by an engagement arm  50  over which the film  40  can be looped (not shown). By slowing down the unwinding operation of the film  40 , as it is advanced through the apparatus  10 , the film  40  is constantly transported under a defined tensile stress that keeps the film  40  taut. 
     The film  40  enters the apparatus  10  according to  FIG. 1   a  from the left and is guided first by a freely running deflection roller  22  for movement in a feed direction marked by the arrow. The film  40  then reaches an entry slot  32  of the apparatus  10 . The entry slot  32  is formed by guide plates and extends initially in a substantial horizontal direction. The entry slot  32  as well as an exit slot  30  on the opposite end of the apparatus  10  has a depth of few centimeters so that only the border area of the film tube  40  is guided in the slots  32 ,  30 . The remaining area of the film tube  40 , which typically has a width of approx. 20 cm, remains untouched by the slots  30 ,  32 , but drags along a horizontal contact surface  36  so that filler pads can evolve unimpeded during gas filling, and the width of the filler pads can be flexibly selected. 
     A flat gas filling device  16  engages between the upper and lower film portions or layers, which are initially not interconnected along their margins, and has a wedge-shaped configuration on both ends for lifting the upper and lower film layers from one another and unite them again on the other end. An air passage  13 , shown in  FIG. 1   b , extends in the illustration of  FIG. 1   a  transversely to the drawing plane through the gas filling device  16  and is supplied with air by a fan which is arranged behind a base plate  26  and thus not visible in  FIG. 1   a . The air passage  13  extends slantingly or is configured in such a way that the exiting air flow has a movement component transversely to the drawing plane and in addition a component in movement direction of the film  40 , as indicated by arrow  24 . In this way, air losses in the area of the welding tool  18  can be additionally compensated. 
     The drive unit for transporting the film  40  includes two rollers  12 ,  14  which are driven in synchronism by an electromotive drive and provided with a rubber coating. The electromotive drive of the rollers  12 ,  14  is also provided behind the base plate  26  and thus not visible. One of the rollers, i.e. roller  12 , engages the film  40  from below and is arranged adjacent to the gas filling device  16 . This roller  12  serves also as abutment for the welding tool  18  which is pushed onto the topside of the film  40  and has a relatively small-area welding die to generate a weld seam of a width of typically about 2 to 3 mm. 
     The welding tool  18  is secured to a lever arm  20  which is supported by a support  48 , shown in  FIG. 1   b , and is spring-biased against the film  40 , when the welding tool  18  is operative, but is detached from the film  40 , when assuming an idle state at standstill so as to avoid a melting of the film, whereby the lever arm  20  is swung by hand via an eccentric arrangement which activates the film advance at the same time via a not shown switch. The welding tool  18  is heated electrically via a heating cartridge and hereby held within a predefined temperature range by electronic control. 
     Provided in opposition to the roller  12  is the other roller  14  which is positioned offset to the rear in the transport direction of the film  40  and bears upon the roller  12  in a contact zone  28 . As a result of the offset disposition of the roller  14  in relation to the roller  12 , the film  40  is routed initially along a section of the circumference of the roller  12  and then guided slantingly downwards at an angle α of about 20° to 50° in relation to the horizontal between respective guide plates to the exit slot  30  where the filled gas bodies are discharged. The contact zone  28  between the rollers  12 ,  14  is thus located lower than the initial film transport plane. This angled disposition results in a proper guidance of the film  40  and in a proper weld seam formation. Also, the offset disposition of the roller  14  permits its use as abutment for the welding tool  18 , so that the welding tool  18  can be arranged relatively closely to the gas filling device  16 . As a result, air loss caused by leaks is minimized, with the air losses additionally reduced by the slanted air injection. 
       FIG. 1   b , which is a basic view of the apparatus  10  along a section plane provided in the transport plane of the film  40 , and not to scale, shows the position of the film  40  by way of broken line, respectively. The welding zone or contact surface of the welding tool  18  upon the roller  12  is designated by the area  17 .  FIG. 1   b  shows in particular a possible shape of the air passage  13 , with a slant  15  deflecting an air flow also with a flow component in the direction of the welding zone  17 . This configuration causes the air passage  13  to extend into the region of the circumference of the roller  12 . As the upper and lower film layers lie substantially upon one another before being exposed to the welding tool  18 , the illustrated configuration of the air passage  13  ensures optimum filling without leaks prior to the welding operation. It is also possible to slantingly guide the entire air passage  13  in the opening area, as indicated by the dashed line in the area of the air passage  13 . 
     While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.