Abstract:
An air pad having a plurality of foam filled air chambers interconnected by at least one air passage connecting at least two of the air chambers to one another. The air passages are also filled with foam whereby the flow of air from one air chamber to another due to impact is restricted. The pad is manufactured by radio frequency welding of two layers of plastic film to one another about a foam body to join the plastic film in the area surrounding each of the air chambers.

Description:
This is a division of U.S. patent application Ser. No. 09/108,634, filed Jul. 1, 1998. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     This application claims priority from a provisional application filed Jul. 1, 1997, under U.S. patent application Ser. No. 60/051,419, entitled “Air Pad.” This invention relates to an air pad and in particular to an air pad that automatically spreads an impinging force over a larger area of a surface, reducing the force per unit area sufficiently to protect the surface from damage and/or to provide improved comfort. 
     Various types and structures of air pads are known. Many are difficult to produce on a large scale and at a low enough cost to be widely accepted in the marketplace. The present invention has been developed to provide an air pad which can be economically produced on a commercial scale and provide improved performance compared to previous air pads. 
     The air pad of the present invention includes first and second plastic film portions that are joined to one another forming two or more air chambers with integral, interconnecting air passages therebetween. Both the air chambers and the air passages contain foam. 
     The plastic film portions can be joined together by a heat joining process such as dielectric welding or sealing, also known as radio frequency welding, as well as a variety of other plastic heat joining processes including, but not limited to, ultrasonic welding, vibration welding, induction welding, microwave welding, friction welding, etc. In addition, adhesive bonding of the plastic sheets can be used in some embodiments of the air pad. 
     In one method of manufacturing the air pad, a layer of sheet foam is placed between the two plastic film portions. The plastic film portions are joined by radio frequency welding. During the joining process, the plastic film portions, in the areas surrounding the air chambers, are fused together to join the film portions. Additionally, where the plastic film portions are joined, the cellular structure of the foam layer between the plastic film portions is collapsed. The collapsed foam material forms a part of the fused joint between the plastic film portions. 
     In another method of manufacturing the air pad, a foam body is pre-molded or pre-formed in the shape of the air chambers and interconnecting air passages. The plastic film portions may also be pre-molded into the shape of the air chambers and interconnecting air passages. The plastic sheets are then joined together with the pre-molded foam body therebetween, substantially filling the air chambers and air passages. 
     The air pad is preferably manufactured as a sealed air tight pad. If desired, an inflation valve, or pump, to inflate the air pad, such as that shown in U.S. Pat. No. 4,566,137, hereby incorporated by reference, can be added to the air pad to enable the air pressure within the pad to be varied. 
     The air pad of the present invention can be used to provide impact protection for various parts of the body. When an impact is received, air will flow from one or more of the chambers, through the interconnecting air passages, to adjacent chambers in response to an increased air pressure within the chambers receiving the impact. The foam, within both the air chambers and the interconnecting air passages, slows the flow of air between chambers. This regulation or restriction of the air flow from one chamber to the next, prevents the air chambers from deflating as quickly as air chambers in a pad with no restriction of the air flow between chambers. 
     The air pad can be used to provide impact protection within protective equipment such as that worn during athletic events. This includes shin guards, knee pads, elbow pads, shoulder pads, within a flexible fabric or elastic cover, etc. The air pad can also be used to provide impact protection as a pad within a substantially rigid shell such as a helmet, shoulder pad, elbow pad, etc. The air pad can also be used in low or no impact applications where additional cushioning is desired for comfort, as opposed to impact protection. These uses include, but are not limited to, shoulder straps and handles for luggage, briefcases, computer cases, golf bags, back packs, etc. The air pads can also be used in shoes, shoe tongues, etc. 
     Since the air pad is made by placing a foam sheet between two layers of plastic and then fusing the plastic together between the desired air chambers, it is simple to manufacture the pad. As a result, economical manufacture on a commercial basis is possible. A wide variety of sizes and shapes can be made. Different performance characteristics, i.e., impact spreading and cushioning can be achieved by different foam thicknesses and types of foam. 
    
    
     Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an air pad made according to the present invention; 
     FIG. 2 is an exploded perspective view of the air pad of the present invention showing the components of the pad; 
     FIG. 3 is a plan view of a dielectric sealing tool for manufacture of the air pad of the present invention; 
     FIG. 4 is an exploded perspective view of an air pad similar to FIG. 2 showing an alternative construction and method of manufacturing the pad; 
     FIG. 5 is a side elevation view of two air pads placed together forming a double layer for enhanced impact protection and/or cushioning; 
     FIG. 6 is an exploded perspective view of a knee pad utilizing the air pad of the present invention; 
     FIG. 7 is an exploded perspective view of an elbow pad utilizing the air pad of the present invention; 
     FIG. 8 is an exploded perspective view of an add-on luggage handle pad utilizing the air pad of the present invention; 
     FIG. 9 is a perspective view of a shoulder strap pad utilizing the air pad of the present invention; 
     FIG. 10 is an partial perspective view of a boat with the air pad of the present invention attached thereto for use as a boat bumper; 
     FIGS. 11 and 12 are cross sectional views of alternative embodiments of the air pad of the present invention; and 
     FIG. 13 is a perspective view similar to FIG. 1 of yet another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The air pad of the present invention is shown in FIG.  1  and designated generally at  10 . Air pad  10  is made of two plastic film portions joined together with a foam layer therebetween. The foam substantially fills a plurality of spaced apart air chambers  12 . The chambers  12  are connected to one another by interconnecting air passages  14 , which also contain foam. The air chambers are surrounded by fused portions  16  where the two plastic film portions are joined together. The air pad  10  shown in FIG. 1 is representative of one arrangement, or configuration, of the air chambers. The air pad of this invention is not limited to any particular size, shape or arrangement of the chambers  12 . 
     With reference to FIG. 2, the construction of the air pad is shown in greater detail. The air pad is made of two sheets of flexible plastic film, lower sheet  18  and upper sheet  20 , with a layer of foam  22  therebetween. It will be apparent that one sheet of plastic, folded over on itself, can be used in place of two separate sheets. The plastic sheets can either be flat, as the sheet  18  or alternatively, the plastic sheets can be preformed to the shape of the air chambers as shown with the upper sheet  20 . The plastic sheets and foam are placed between two dielectric sealing tools which engage portions of the sheets  18  and  20 . The dielectric tools are used to locally heat and seal the sheets and to collapse the cellular structure of the foam  22  therebetween. The plastic sheets are thus sealed to one another in the area surrounding the air chambers. 
     FIG. 3 shows a representative example of a dielectric tool  26  illustrating the contact surface  28  of the tool where the tool contacts the plastic sheets to seal them. The air chambers  12  and interconnecting air passages  14  of the air pad are formed between the locations where the dielectric tool contacts the plastic sheet in recesses or cavities  12 ′ and  14 ′, respectively, in the dielectric tool. 
     Another method of manufacturing the air pad is shown in FIG.  4 . There, a lower plastic sheet  30  and an upper plastic sheet  32  are both preformed to the shape of the air chambers and interconnecting passages. In addition, the foam  34  is also pre-formed or die cut to the shape of the air chambers and air passages. The plastic sheets can be joined together using radio frequency sealing or other weld joining processes mentioned above. However, there will be no foam between the sheets where the sheets are joined. Since there is no foam where the sheets are joined together, adhesive can be used to Join the plastic sheets together instead of a heat welding type joining process. 
     The foam can be either an open cell or a closed cell type foam. With an open cell foam, air flows through the foam cells as the air travels from one chamber to another. With a closed cell foam, air on the surface of the foam is allowed to flow between the foam and plastic sheets from one chamber to the next. Upon impact, the air contained within the closed cells is also compressed. A closed cell foam will likely produce a greater restriction to air flow between chambers. The foam can be made of a variety of plastic resins including, but not limited to polyurethane. A dielectric foam having a PVC additive may be preferred when dielectric sealing is used to manufacture the pad. Other resilient foam materials can be used as well. 
     Likewise, a variety of plastic resins can be used for the plastic film sheets including polyurethane, vinyl and blends containing different percentages of each or other resins. While vinyl and polyurethane are preferred, any plastic film which can be dielectrically or adhesively sealed can be used. The plastic film can include various additives such as UV stabilizers and flame retardants. 
     The plastic film can also be laminated, bonded to or coated to other materials such as, but not limited to, nylon, polyester, fabrics and hook and loop fastener materials. For example, with reference to FIG. 11, a pad  102  is shown. The pad  102  has plastic film sheets  104  and  106  with foam  108  forming the air chambers  110 . The plastic film sheet  106  is laminated to a layer  112  which can be a nylon, polyester etc. layerwhich is woven, knit etc., into a fabric. The layer  112  can provide durability to the air pad when made of a durable woven material and can also provide a different appearance to the air pad. The pad  102  is formed by first laminating the plastic film sheet  106  to the outer layer  112 . The laminate construction is then used to form the pad  102  as described above. The selection of the material  112  is guided by those materials which can withstand the heat sealing process such as the dielectric welding used to join the plastic sheets  104  and  106 . Another embodiment is shown in FIG.  12 . In this embodiment, the layer  112  is the backing to the loop portion of a hook and loop fastener. As a result, a plurality of randomly oriented loops  114  forms the exterior surface of the air pad. 
     The film thickness is typically between 5 and 20 thousands. A preferred range is between 10 and 15 thousands. Below 10 thousands, sealing can be difficult. Above 15 thousands, depending on the material type, the plastic may not be sufficiently elastic and overly compresses the foam within the air chamber. Other 
     A single layer of air chambers can be used to provide impact protection and/or cushioning. Alternatively, two or more layers of air chambers can be used to provide enhanced protection and comfort. This is also shown in FIG. 5 where two air pads  36  and  38  are placed together, forming a double layer of air chambers. When using multiple layers, it is preferred to arrange the air chambers  40  of one layer between the air chambers  42  of an adjacent air layer as shown. With multiple layers of air chambers, the force of an impact is spread over a larger number of chambers, providing a greater reduction in the force per unit area applied to the under lying surface. A double layer of air chambers can be formed with a single pad that is folded over on itself to form two layers, as shown in FIG. 1 by the arrow  39 . The joined plastic film sections  41  form a hinge between the two rows of air chambers  12 . 
     The air pads of the present invention can be used in a variety of applications. One application is shown in FIG. 6 where it is used as a liner within a knee pad assembly  46 . The assembly  46  includes an air pad  48  having a plurality of air chambers  50  and interconnecting air passages  52 . The knee pad assembly further includes a semi-rigid or rigid molded plastic shell  54  to which the air pad is mounted by extending tabs  59 . Other mounting means can be used to mount the air pad to the outer cover. An inner cover  56  may be added to cover the inner side of the air pad to provide a soft, comfortable surface for contact with the wearer. Straps  58  and  60  are used to attach the assembly to a person&#39;s leg. The straps pass through slots on the outer cover, such as slot  61 . The molded shell can be made of a variety of plastics, including but not limited to polypropylene. In some applications, the air pad can be used as a liner within a flexible cover of fabric, vinyl, leather, etc. instead of a rigid molded plastic cover. 
     An elbow pad assembly is shown in FIG. 7 which includes an air pad  62  having four generally spherical air chambers  64  and a fifth tubular air chamber  66  that is not interconnected with any of the other air chambers. The air pad is folded over with the tubular air chamber  66  being disposed between the spherical chambers  64 , forming a double layer of air chambers. The air pad  62  is placed within a shell  68 . Straps  70  and  72  are joined to the shell  68  for receiving the arm of a wearer. 
     The air pad of the present invention can be incorporated into a pad for a luggage handle or strap as shown in FIG.  8 . An air pad  74  is formed with a hinge  76  allowing the pad to be folded over on itself forming a double layer of air chambers. The folded pad is inserted into a pocket  78  within a fabric cover  79 . The cover  79  includes mating hook and loop fastener strips  80  and  82 , allowing the cover  79  to be wrapped around a luggage handle or a luggage shoulder strap to provide additional cushioning. 
     An air pad  84  is shown in FIG. 9 for use in conjunction with a shoulder strap  86 . The pad  84  includes a number of air chambers  88 . A panel  85  is sewn to the pad  84  by stitching  87  to form a slot between the pad  84  and panel  85 . The strap  86  extends through the slot to mount the pad to the strap. The pad can be integrally formed into the shoulder strap by sewing the ends of the pad to the shoulder strap webbing. The shoulder strap can be used in luggage, purses, back packs, etc. 
     Another application of the air pad of the present invention is shown in FIG. 10 where an air pad  96  is mounted to a boat  98 . Pad  96  hangs over a side edge  100   
     Another application of the air pad of the present invention is shown in FIG. 10 where an air pad  96  is mounted to a boat  98 . Pad  96  hangs over a side edge  100  of the boat to provide protection to the boat. Pad  96  includes spherical air chambers  97  and interconnecting air passages  99 . 
     An alternative embodiment of the air pad of the present invention is shown in FIG.  13 . There the pad  118  shown is similar to the pad  10  in FIG.  1 . The pad has one or more air chambers  120  which are filled with foam as described above. The air chambers  120  are not interconnected with any other of the air chambers in the pad. Depending on the comfort or cushioning characteristics required, the air pad may have one or more air chambers that are filled with foam but not interconnected with another air chamber whereby upon impact, the air sealed within the air chamber  120  is only compressed. The air does not travel out of the chamber  120 . 
     The air pad of the present invention can be used by itself in a comfort or protection device. Alternatively, a cushion can be constructed having one or more air pads according to the present invention, combined together with one or more layers of foam or other cushioning material. Depending upon the application, having multiple layers of air pads and foam may be desired. 
     The air pad of the present invention can be used in any application where cushion or impact protection is desired including, but not limited to, shoe soles, shoe sole liners, sole inserts and the tongue of the shoe, medical devices, athletic equipment, apparel, sports, fishing, hunting, hiking, and camping equipment and can be used in many fields including, but not limited to, athletics, packaging, aerospace, automotive, marine and military. 
     It is to be understood that the invention is not limited to the exact construction illustrated and described above, but that various changes and modifications may be made without departing from the spirit and scope of the invention.