Abstract:
An exemplary embodiment of the invention is a flow control valve including a first sheet having a hole therein and a second sheet secured to said first sheet at a plurality of separate seal locations along a periphery of the first and second sheets. The seal locations define at least one channel between the seal locations. The second sheet has an aperture therein in fluid communication with the hole and selectively in fluid communication with the channel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional patent application No. 60/105,123 filed Oct.21, 1998, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to inflatable bladders and more particularly, to a valve formed of layers of sheet material for controlling the inflation and deflation of an inflatable bladder. 
     BACKGROUND OF THE INVENTION 
     It is known in the art to use inflatable structures for many applications, such as seat cushions, mattresses and medical devices. Many of these structures require that the rate of inflation differ from the rate of deflation of the bladder. Complex mechanical valves are used to control the rate of inflation and deflation of the inflatable structures. In other instances, a pump is used to control the inflation and deflation of these structures. 
     BRIEF SUMMARY OF THE INVENTION 
     An exemplary embodiment of the invention is a flow control valve including a first sheet having a hole therein and a second sheet secured to said first sheet at a plurality of separate seal locations along a periphery of the first and second sheets. The seal locations define at least one channel between the seal locations. The second sheet has an aperture therein in fluid communication with the hole and selectively in fluid communication with the channel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
     FIG. 1 is a sectional view of a bladder; 
     FIG. 2 is a top plan view of a baffle for the bladder of FIG. 1; 
     FIG. 3 is an exploded sectional view of a flow control valve; 
     FIG. 4 is a sectional view of the flow control valve of FIG. 3; 
     FIG. 5 is a top plan view of the flow control valve of FIG. 3; 
     FIG. 6 is a sectional view of the bladder partially inflated; 
     FIG. 7 is a sectional view of the bladder partially deflated; 
     FIG. 8 is a perspective view of the alternative embodiment of a bladder system embodying the present invention; and 
     FIG. 9 is a sectional view of the bladder system of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, it is seen that a multi-chambered bladder, generally designated  10 , comprises four layers of sheet material  12 - 15  sealed together to form a pair of chambers  16 ,  18 . The bladder  10  is a single cell that is divided by an internal baffle  20 . The bladder is inflatable with any fluid including air. A valve  22  is attached to the baffle to allow for a two stage inflation of the single bladder  10 . As described herein, chamber  16  inflates faster than chamber  18 . The bladder may be used for a medical device having the objective to apply pressure to the leg of the ankle first followed by the calf from a single air source with constant pressure. This type of staged pressure is known to stimulate blood circulation. The bladder  10  is inflated through an input port  24 . The valve  22  allows both chambers  16 ,  18  of the cell  10  to deflate rapidly at about the same rate. This sets up the next cycle of pressurization to start with both segments at zero pressure. Historically one would use the two independent cells and a timed pumping cycle. The valve  22  allows for a single, unified divided bladder and a simple pumping system. 
     The bladder  10  is formed of two layers  12 ,  13  of sheet material, such as heat sealable thermoplastic material, superimposed on each other and heat sealed about its periphery. The baffle  20  is sealed between the two layers  12 ,  13  to form two chambers interconnected by the control valve  22 . 
     Referring to FIGS. 1 and 2, the baffle  20  is formed of two layers  14 ,  15  of sheet material sealed along a portion of its outer edge at  26 . The baffle includes and extension  28  to connect one end of the baffle  20  to the outer edge of the bladder  10 . The extension  28  secures the bladder  20  to the outer sheets  12  and  13  and prevents the baffle  20  from turning back towards input port  24  during deflation. The inner surface  30  of the open end of the baffle is coated with a release material  32  to prevent the open ends of the baffle from sealing together when the outer surface  34  of the open ends of the baffle are sealed to the inner surface  36  of the cell  10 . 
     The control valve  22  is sealed to the inner surface of one layer  14  of the baffle  20 . The valve  22  restricts the air flow passing from the first chamber  16  to the second chamber  18 , and thereby inflating the first chamber faster than the second chamber. Further, the control valve  22  allows the second chamber  18  to deflate at a faster rate. One will appreciate that the valve may be sealed to the outer surface  34  of the baffle  20  to reverse the inflation and deflation rates as described hereinbefore. 
     The control valve  20  of the present invention is similar to the inlet check valve described in U.S. Pat. No. 5,372,487 to Pekar for an “Inlet Check Valve For Pump Mechanism.” As best shown in FIGS. 3-5, the control valve  22  is formed of an upper and lower layer  38 ,  40  of sheet material. The lower layer  38  includes a plurality of apertures  42  disposed therein. The upper layer  40  includes a hole  44  located to be in registered relations with one of the apertures  42  of the lower layer  38 . The upper and lower layers  38 ,  40  are sealed at predetermined seal locations  46  to form a plurality of channels  48 . A central channel  50  interconnects each of the holes  42  of the lower layer  38 . Channels  48  radiate outward from the central channel  50  to provide a exhaust path for air passing through the lower layer  38 . The valve  22  is sealed to the layer  34  of the baffle  20  (See FIG. 1) positioning the apertures  42  of the lower layer  38  of the valve with the holes  52  disposed in the layer  34  of the baffle  20 . The lower layer  38  is heat sealed to the baffle  20  about the periphery of each of the apertures  42 . The inner surface  54  of the upper layer  40  of the valve  22  is coated with a release material  56  to prevent the upper layer  40  from sealing to the lower layer  38  of the valve  22  about the apertures  42 , and thereby seal off the channels  48 ,  50  of the valve. 
     During the inflation of the inflatable bladder  10  as shown in FIG. 6, air passes into the first chamber  16  through input port  24 . A pressure P 1  against the valve  22  forces the channels  48 ,  50  of the control valve to close and thereby force all the air to pass through the hole  44  disposed in the upper layer  40  of the control valve and through one aperture  42 . Accordingly, the hole  44  and aperture  42  are in fluid communication. The diameter of the hole  44  determines the rate of inflation or delay of inflation of the second chamber  18 . Preferably the hole (or fill element)  44  of the control valve  22  is positioned a sufficient distance from the outer layer  12  of the bladder  10 , which allows for continuous uninterrupted flow of air from the first chamber  16  to the second chamber  18  as shown by arrow A. As shown in FIG. 6, the outer layer  12  of the second chamber  18  may cover the hole  44  and therefore a safe gap shown as X may be needed to provide for continuous inflation of the second chamber  18 . 
     During the deflation of the inflatable bladder  10  as shown in FIG. 7, the air from the first chamber  16  deflates at a faster rate and therefore the pressure P 2  in the second chamber  18  is greater than the pressure P 1  in the first chamber  16 . This pressure differential deflects upper layer  40  from lower layer  38  and opens channels  48 . The air from second chamber  18  exits through each of the holes  52  in baffle  20  aligned with apertures  42  of the valve  22  and out channels  48 . Thus, apertures  42  are in fluid communication with channels  48  and hole  44 . The increased cross sectional area of the apertures  42  of the control valve permits the second chamber  18  to deflate at a much higher rate than it inflated. Conversely, during deflation, the pressure P 1  in the first chamber drops quickly and in order to follow suit in a compressed time span, two relatively large apertures  42  of the valve  22  are located closer to the cross seal at  54  to allow maximum flow without blocking the apertures  42  as the baffle collapsed during deflation of the second chamber. 
     The rate of inflation of the second chamber  18  is dependent upon the cross sectional area of the hole  44  in the upper layer  40  of the control valve  22 . The rate of deflation of the second chamber  18  is dependent upon the cross sectional area of the apertures  42  in the lower layer  38  of the control valve  22 . 
     While the invention as described hereinbefore include a control valve  22  having three apertures  42  for deflating the second chamber  18  and a single hole  44  for inflating the second chamber  18 , one skilled in the art will appreciate that control valve  22  do may include any number of holes  44  and apertures  42  to meet the desired rate of inflation and deflation. 
     FIGS. 8 and 9 illustrate another embodiment of the present invention, the inflation system is a back and seat cushion  60  having base inflation cushions  62  that feed side bolsters  64  utilizing the control valve  22  described hereinbefore. The control valve is sealed to the layer of a chamber disposed between the base chamber  62  and the bolster chamber  64 . 
     It will be understood that a person skilled in the art may make modifications to the preferred embodiment shown herein within the scope and intent of the claims. While the present invention has been described as carried out in a specific embodiment thereof, it is not intended to be limited thereby but is intended to cover the invention broadly within the scope and spirit of the claims.