Abstract:
A seating cushion includes an upper layer that is secured to a lower layer. The upper layer includes a plurality of interconnected gel pockets and the lower layer includes a plurality of interconnected gas pockets. In one configuration, each layer is formed from two sheets of material that are joined together at a plurality of corners to form the pockets of the layer. The layers are secured together such that a pair of sheets are disposed in the middle portion of the cushion. The upper and lower layers may be joined to a resilient foam base.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from U.S. Provisional Patent Application Ser. No. 60/576,230 filed Jun. 2, 2004, and U.S. Provisional Patent Application Ser. No. 60/576,715 filed Jun. 3, 2004; the disclosures of both are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. TECHNICAL FIELD  
         [0003]     The present invention generally relates to seating cushions and, more particularly, to seating cushions designed for extended use situations such as office chairs, vehicle seats, and wheelchairs. Specifically, the present invention relates to the structure of a seating cushion that includes both gel and air layers. The invention also relates to the method of manufacturing the cushion.  
         [0004]     2. BACKGROUND INFORMATION  
         [0005]     Those who sit for extended period of time at office chairs or as drivers desire comfortable seat cushions that minimize pressure points. Those who are forced to use wheel chairs for long periods of time desire seat cushions that minimize the risk of sores caused by pressure points. All seat cushion users desire comfortable seat cushions that uniquely conform to the user&#39;s body each time the user sits on the cushion.  
         [0006]     Many existing seat cushions use foams and gels to provide comfortable supporting surfaces for the user. One problem with large foam cushions is the overall weight of the cushion. Another problem is that the cost of the material used to form the body portion has risen. Cushion manufacturers thus desire a cushion configuration that minimizes the amount of foam used in order to reduce the weight and cost of the cushion. Cushion manufacturers also desire a cushion configuration that is designed to work with gel materials that are injected as a liquid and cure to a solid soft gel. Although numerous designs exist in the art, room remains for improvement in the art.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     The invention provides a cushion having connected upper and lower layers wherein the upper layer includes a plurality of gel pockets and the lower layer includes a plurality of air pockets. In one configuration, each layer may include first and second sheets of material. In another configuration, only three sheets of material are used to form the upper and lower layers. Another configuration aligns the pockets of the upper layer with the pockets of the lower layer. The aspects of the different configurations may be used alone or in combination with each other.  
         [0008]     The invention provides a method for forming a cushion that includes the steps of joining first and second sheets together to form a gel chamber; joining third and fourth sheets together to form a gas chamber; connecting the gel chamber to the gas chamber; and at least partially filling the gel chamber with a gel material and filling the gas chamber with a gas.  
         [0009]     In another configuration, the invention provides a method for forming a cushion that includes the steps of welding first, second, and third sheets together to form at least one gel pocket and at least one gas pocket; and at least partially filling the gel pocket with a gel material and filling the gas pocket with a gas. In another configuration, a plurality of interconnected pockets are formed for the gel and a plurality of interconnected pockets are formed for the gas. The gel is inserted into the plurality of interconnected pockets in a flowable form and then cured so that it does not migrate from pocket to pocket when subjected to pressure. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic perspective view of an exemplary cushion made in accordance with the concepts of the invention.  
         [0011]      FIG. 2  is a section view taken along line  2 - 2  of  FIG. 1 .  
         [0012]      FIG. 3  is a top plan view of an exemplary six-pocket cushion showing the perimeter weld and two intermediate corner welds.  
         [0013]      FIG. 4  is a perspective view of a cover for the cushion.  
         [0014]      FIG. 5  is a perspective view of an alternate cover for the cushion of the invention.  
         [0015]     Similar numbers refer to similar parts throughout the specification.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     An exemplary cushion made in accordance with the concepts of the present invention is indicated generally by the number  10  in  FIG. 1 . Cushion  10  includes an upper layer  12  and a lower layer  14  that are connected together to form an integral cushion  10 . Optionally, cushion  10  may be combined with a body layer  16  when placed into service. Body layer  16  is particularly useful for wheelchair applications where a saddle-shaped seat is desired.  
         [0017]     Upper layer  12  is formed from a pair of opposed sheets of material (first sheet  30  and second sheet  32 ). Each sheet  30  and  32  is formed from a weldable, air-impermeable, flexible material. In one embodiment, each sheet is 0.3 mm to 0.8 mm in order to provide desired strength and weld properties. In one embodiment, the material is a polyurethane. When joined together, sheets  30  and  32  define a plurality of pockets  18  that are each interconnected with passageways  33  such that a fluid may flow from pocket  18  to pocket  18 . In the exemplary embodiment, the pockets are rectangular.  
         [0018]     Lower layer  14  also is formed from first  34  and second  36  sheets of material similar to sheets  30  and  32 . When joined together, sheets  34  and  36  define a plurality of pockets  22  that are interconnected to one another such that fluid may flow from pocket  22  to pocket  22 . Pockets  22  are filled with a gas such as air. A valve  24  is in communication with at least one pocket  22  and allows all pockets  22  to be filled with the gas and also allows the firmness of lower layer  14  to be varied by selectively adding and removing gas from pockets  22 . Valve  24  may be welded between the sheets or through a single sheet before the sheets are welded together.  
         [0019]     Upper layer  12  is formed by cutting sheets  30  and  32  to size, overlaying the layers, and welding the layers together to form pockets  18 . The welding may be by any welding method useful for welding the sheets of material together. The inventors have found that ultrasonic welding methods are useful. The sheets are welded along their perimeters and at the corners of the pockets so that material may flow from pocket to pocket. In another embodiment, sheets  30  and  32  may also be welded along 1/4 to 1/3 of each pocket  18  sidewall to restrict passageways  33 . After sheets  30  and  32  are welded, liquid gel is injected into pockets  18  at an appropriate location. The liquid gel is a type that cures to a solid, non-flowable material. The gel may thus include a catalyst that allows it to cure into a soft solid gel. A polyurethane gel has been found to be useful for this application. Polyurethane and silicone gels may also be used. A gel that remains a fluid may also be used. Pockets  18  may be configured to be substantially filled with gel after the gel is cured. In other embodiments, pockets  18  may be sized to hold both air and gel. The inlet for the gel is then sealed by an appropriate method such as spot welding the inlet. The welding may occur after the gel dries.  
         [0020]     Upper layer  14  is formed by cutting sheets  34  and  36  to size, overlaying the layers, and welding the layers together to form pockets  22 . The welding may be by any welding method useful for welding the sheets of material together. The inventors have found that ultrasonic welding methods are useful. The sheets are welded along their perimeters and at the corners of the pockets so that material may flow from pocket to pocket. In another embodiment, sheets  34  and  36  may also be welded along 1/4 to 1/2 (from each corner as shown in the drawings) of each pocket  22  sidewall to restrict the passageways between the pockets. For example, each passageway between the pockets may be about 3/8 inch wide on a pocket sidewall of about an inch long. Valve  24  is welded in place and is then used to fill pockets  22  with air. Pockets  22  are arranged to align with pockets  18  when the layers over joined together such that one gel pocket sits immediately above an air pocket.  
         [0021]     Layers  12  and  14  are connected together by any of a variety of connection methods that securely connect the layers for use over a long period of time. One method is to weld the layers together at their perimeter edges and/or at the corners of the pockets. Another method is to use an adhesive (such as a urethane adhesive). A further method is to use mechanical connectors that hold the layers together. When welding is used to hold the layers together, the welding may be performed before the layers are filled with the gel and air.  
         [0022]     Body layer  16  is a dense foam material such as a polyurethane foam. Body layer  16  may be connected to lower layer  14  with an adhesive such as a urethane glue. The foam material may be a visco-elastic foam material, a high density foam (such as a high density polyurethane foam), and other foams known in the cushion art.  
         [0023]      FIG. 4  shows an exemplary cover into which cushion  10  may be placed when in use. Cushion  10  may be fabricated from a breathable waterproof material (i.e.: Tyvek®). Although a flap is shown in the drawing, a zipper may be used to close the cover.  
         [0024]      FIG. 5  shows an alternative cover having separated chambers. In this embodiment, upper  12  and lower  14  layers are separated from body layer  16  and placed in the individual chambers when cushion  10  is in use.  
         [0025]     In an alternative embodiment of the invention, upper layer  12  is formed without pockets and the gel is placed into a single large pocket that is defined by the entire surface area of upper layer  12 . In this alternative embodiment, the upper layer is formed by welding a single sheet of material to the lower layer such that only three sheets are used to form cushion  10 . The upper sheet used to form the gel chamber may be welded after the air pockets are welded or simultaneously with the two sheets that are used to form the air pockets.  
         [0026]     In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.  
         [0027]     Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.