Abstract:
The apparatus includes an elastic layer for supporting a person. A plurality of rows of expandable and retractable tubes are embedded in the elastic layer. A source of compressed air and a control system are provided for sequentially injecting and releasing air into and from a first set of alternate tubes and then into and from a second set of alternate tubes for imparting continuous motion to the elastic layer.

Description:
SPECIFICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/299,350, filed Jun. 19, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for imparting continuous motion to a mattress for supporting a bed-ridden patient. 
     2. Description of the Prior Art 
     Mattresses have been produced to prevent decubitus ulcers (bed sores) from forming on bed-ridden patents due to the lack of movement and circulation of the patient, however, the known mattresses do not operate effectively to perform their intended function and/or they are difficult to operate. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a new and useful mattress and system for effectively preventing bed-sores from forming on patients. 
     The mattress comprises an elastic layer with a system for imparting continuous motion to the support layer. 
     The system comprises a plurality of rows of spaced apart expandable and retractable tubes embedded in the elastic layer with means for expanding and retracting sequentially a first set of alternate rows of tubes and then a second set of alternate rows of tubes to impart motion to the elastic layer. 
     In a further aspect, a source of gas under pressure and an exhaust means is provided. A control means sequentially connects a first set of alternate rows of tubes to the source of gas and then to the exhaust means and a second set of alternate rows of tubes to the source of gas and then to the exhaust system for exhausting and retracting the first set of tubes and then the second set of tubes. This sequence will be controlled by zones or as a complete mattress. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates the mattress of the invention on a bed frame. 
     FIG. 2 is a top plan view of the expandable and retractable pressure tubes of the mattress of the invention. In FIGS. 1 and 2, the pressure tubes are shown above the support layer, however, they will be molded into the support layer near its upper surface as seen in FIG.  3 . 
     FIG. 3 is a side view of the mattress assembly with the pressure tubes depicted in the top layer near its upper surface. 
     FIG. 4 is a view of one of the pressure tubes of the mattress as seen from the end of the mattress. 
     FIGS. 5 and 6 are cross-sectional views of one of the pressure tubes of the mattress in retracted and expanded positions respectively. 
     FIG. 7 is a cross-sectional view of a section of the pressure tubes of the mattress with the pressure tubes in retracted positions. 
     FIG. 8 is a cross-sectional view of a section of the pressure tubes of the mattress with alternate pressure tubes in expanded positions. 
     FIG. 9 is a cross-sectional view of part of the pressure tubes in expanded positions with the mattress shaped by a patient&#39;s contour. 
     FIG. 10 is a block diagram of the air supply system of the invention. 
     FIGS. 11 and 12 are enlarged side views of two of the pressure tubes of the mattress. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings there is illustrated a bed frame  21  that supports the mattress  23  of the invention for supporting a person. The mattress is a two layer mattress comprising an upper layer  25  and a lower layer  27 . The layer  25  preferably is formed of a gel/poly matrix with pressure tubes  31  molded into the mattress, The gel/poly matrix may be an elastic or visco-elasfic material with a shore A durometer hardness range of from shore A 0  to A 40 . The pressure tubes  31  may be formed of a low density/low molecular weight polyethylene or plastic (slightly higher hardness and higher density that the gel/poly matrix) extruded tube upper and lower halves. 
     The lower layer  27  preferably is of the high density polyurethane foam that will be both supportive and flexible. The high density polyurethane foam will be permanently bonded to the gel/poly matrix with an anti-microbial, bacteria resistant, fluid proof, flame retardant, stain and tear resistant, non-allergenic fabric cover. Both layers  25  and  27  are shown in FIG. 1 as supported by the bed frame  21 . 
     The tubes  31  are molded or embedded in the layer  25  in spaced apart parallel rows extending across the width of the layer  25  and located near the top surface  25 T of the layer  25 . 
     Referring to FIGS. 5 and 6, each of the tubes  31  comprises a lower tube half  31 L and an upper tube half  31 U. The lower half  31 L is U-shaped in cross-section having a base  41  and thin side walls  41  A defining a central space or chamber  43  between the two walls. Each wall  41 A has a slot  41 S formed therein from its upper edge  41 U defining two walls  45  and  47 . Each wall  45  at its upper end has a downward extending flange  45 F. In FIG. 6, the dimension D may be equal to a 0.10″ to 0.40″. 
     The upper half  31 U has a rounded upper portion  51 , a central wall  53  slidable in opening  43  and two side walls  55  slidable in the two slots  41 S. Each wall  55  has an upward extending flange  55 F at its lower end. Although not shown, suitable seals will be provided between the walls  55  and  45  and  47 . 
     In the retracted position, the flange ends of the walls  55  engage the bottoms of the slots  41  S as seen in FIG.  5 . In the extended position, the upper half  31 U moves up as shown in FIG.  6 . The two pairs of flanges  45 F and  55 F will engages each other if the upper half  31 U moves too high and prevent walls  55  from moving out of the slots  41 S. The upper portion  31 U of each pressure tube will be able to move upward from 0.10 to 0.40 of an inch relative to its lower portion  31 L. 
     A gas which is preferably air is injected into the opening or chamber  43  to move the upper half  31 U to its extended position and is withdrawn from the chamber  43  to move the upper half  3 U to its retracted position. When this occurs motion is imparted to the plastic layer  25 . 
     As seen in FIGS. 3,  7 ,  8 , and  9 , the tubes  31  are located in spaced apart rows. In FIG. 2, the rows of tubes are shown engaging each other, however, adjacent rows of tubes  31  will be spaced apart as shown in FIGS. 3,  7 ,  8 , and  9 . Adjacent pressure tubes  31  may be located 1″-3″ apart. As shown in FIGS. 1,  2 , and  4  the ends  31 E 1  and  32 E 2  of each pressure tube  31  will be spaced inward from the edges  25 E 1  and  25 E 2  of the layer  25  and flexible plastic tubes  61 A and  63 A will extend through the layer  25  parallel to its edges  25 E 1  and  25 E 2 . Small flexible plastic tubes  61 B and  63 B extend from tubes  61 A and  63 A into the chambers  43  of the appropriate tubes  31 . The tubes  61 A and  63 A then extends downward through layers  25  and  27 . In the embodiment disclosed, tube  61 A is located on one side of the mattress and flexible plastic tubes  61 B extend into the chambers  43  of alternate tubes  31 A and flexible plastic tube  63 A is located on the other side of the mattress and flexible plastic tubes  63 B extend into alternate tubes  31 B. Thus tube  61 A is in fluid communication with the chambers  43  of alternate tubes  31 A and tube  63 A is in fluid communication wit the chambers  43  of alternate tubes  31 B. The lower halves  31 L of tubes  31 A and  31 B will have end enclosures or walls  31 AE and  31 BE through which the tube connections  61 B and  63 B extend respectively as shown in FIGS. 11 and 12. 
     In operation of the system, air is injected and exhausted from the chamber  43  of tubes  31 A and then injected and exhausted from the chambers  43  of tubes  31 A. This is done on a continuous basis to impart continuous motion to the layer  25 . 
     The tube upper half  31 U will transfer motion into the gel/poly matrix  25 , which in turn will create movement and maintain circulation in tissue of the patient. The tube lower half  31 L will direct approximately 80% of the motion energy of the compressed air vertically into the upper half  31 U of the tube  31 . The remaining 20% of motion energy will be absorbed into the gel/poly matrix. 
     In the preferred embodiment, as shown in FIGS. 2 and 3, the length of the mattress  25 ,  27  is divided into four zones, an upper body zone, a lumbar zone, a buttocks zone, and a lower leg and heel zone. 
     Approximately, twenty eight tubes  31  are located in the upper body zone and eighteen tubes  31  are located in each of the lumbar, buttocks, and lower leg and heel zone. These numbers, however, may vary. In each zone, tubes  61 A are coupled to the chambers  43  of alternate tubes  31 A and tubes  61 B are coupled to the chambers  43  of alternate tubes  31 B. 
     The four zones will permit angle and position adjustability of the mattress and also provide the option of independent control of continuous motion in each zone. Continuous motion will be controlled by an air supply system to be discussed subsequently. The air supply system will provide 15 to 40 psig at 15 to 60 scfm compressed air supply to the expandable tubes. High/low pressure switch control will provide redundant over pressure protection and control pressure in the expandable tubes. 
     Referring now to FIG. 10, there will be descried the air supply system for imparting motion to the mattress. 
     The system comprises an electrically operated air compressor  71 , a compressed air storage tank  73 , an exhaust silencer chamber  75 , an exhaust  77 , two three way electrically actuated valves  79  and  81  and a programmable logic controller  91 . 
     Air from the compressor  71 , is applied to the storage tank  73  by way of a tube  103  which includes a pressure switch  105 . Compressed air from the tank  73  is applied to two three way valves  79  and  81  by way of tube  107  and tubes  109  and  111 . An air output of the valve  79  is applied to the tube  61 A by way of a pressure switch  113  and an air output of the valve  81  is applied to tube  61 B by way of a pressure switch  115 . Air outputs of the valves  79  and  81  are applied to the exhaust chamber silencer  75  by way of tubes  117  and  119  respectively and then by way of tube  121 . The air output of silencer  75  is applied to the exhaust  77  by way of tube  123 . 
     Switches  105 ,  113 , and  115  have electrical outputs representative of pressure applied to the PLC  91  by way of leads  131 ,  133 , and  135 . The PLC has output leads  141 ,  143 , and  145  coupled to the valve  79 , valve  81 , and the compressor  71  respectively. 
     In operation, the PLC receives inputs from pressure switches  105 ,  113 , and  115  by way of leads  131 ,  133 , and  135 . The compressor  71  is turned on and the PLC  91  senses the pressure at each of switches  105 ,  113 , and  115 . The PLC turns the compressor  71  on or off to maintain the pressure at switch  105  at about 40 psig. The switches  113  and  115  are adjustable to provide a pressure of 15-40 psig at these points and provide inputs to the PLC when the pressure at these points are at the pressure selected. The PLC controls valve  79  to apply air pressure to tubes  31 A and then exhausts these tubes to units  75  and  77  and then controls valve  81  to apply air pressure to tubes  31 B and then exhaust these tubes to exhaust units  75  and  77 . A control timer in the PLC will alternate air flow from tubes  3   1 A to tubes  31 B at 1 to 3 second pressure dwell. The PLC  91  will control the valves  79  and  81  such that each of tubes  31 A and  31 B will have a frequency of expansion and retraction of 3 to 10 seconds and pressure hold duration of 1 to 3 seconds.