PATENT DOCUMENT

Abstract:
A soliton air mattress includes an array of air bladder cells that are individually inflatable to quiescent pressure levels which provide comfortable support for a human body, and a soliton wave generator including an air pressure-pulse generator controlled by a wave sequence generator for introducing into ordered sequences of air bladder cells a wave-like time sequence of air pressure pulses which vary quiescent pressure levels in the cells, the pressure wave resulting in a soliton traveling wave of body support force reduction which traverses surfaces of the air bladder cells, thus reducing normal forces exerted on a body and minimizing the occurrence rate of shear forces exerted on the body, thereby inhibiting formation of bedsores. The soliton wave patterns may optionally simulate water waves and/or rocking motions of a boat to produce relaxing effects.

Full Description:
[0001]    This application is a continuation-in-part of U.S. application Ser. No. 14/179,791, filed Feb. 13, 2014, and claims priority of the following patent applications: U.S. 62/038,946, filed Aug. 19, 2014; U.S. Ser. No. 14/179,791, filed Feb. 13, 2014, U.S. 61/771,083, filed Mar. 1, 2013; U.S. 61/764,060, filed Feb. 13, 2013. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    A. Field of the Invention 
         [0003]    The present invention relates to mattresses of he type used to support a recumbent human. More particularly, the invention relates to novel air mattresses which have an array of individually inflatable and deflatable air bladder cells that receive air pressure pulses in a timed sequence which results in a soliton traveling wave of body support force variation to traverse the surface of the air bladder cells. The soliton body support forces waves can be programmed to travel longitudinally, laterally or obliquely on the upper support surfaces of the air bladder cells, according to pre-determined patterns which can be used to minimize formation of decubitus sores on a patient&#39;s body and alternatively to simulate comforting motions such as floating on a rolling water wave, or rocking in a boat, which simulations may optionally be accompanied by appropriate music and/or environment-simulating sounds. 
         [0004]    B. Description of Background Art 
         [0005]    Pressure sores, which are also known as decubitus ulcers or bed sores occur in the outer tissues of a person&#39;s body if parts of the body are subjected to relatively large normal force pressure gradients, and/or tangential or shear forces, for long periods of time. Such sores are caused by reduction in blood circulation caused by surface force pressures which exceed the person&#39;s capillary blood pressure. The problems with bed sores forming on the skin of persons with medical conditions which require them to be in relatively immobile positions on a hospital bed or in a wheel chair can be severe, resulting in painful, difficult to treat conditions, loss of limbs, or even death. 
         [0006]    For the foregoing reasons, hospitals, nursing homes and other such health care facilities which provide care giving to ailing or elderly people are keenly aware of the necessity for carefully monitoring people under their care to prevent formation of bed sores. A commonly used method to minimize the possibility of bed sore formation is to turn the patient periodically, i.e, to re-adjust the patient&#39;s position on a bed mattress or in a wheel chair so that long-term normal force pressure gradients, can be relieved from parts of a patient&#39;s body. However, turning invariably results in renewed higher pressures on other parts of the body, so the turning process must be repeated usually at least on a daily basis. 
         [0007]    Presumably in response to a perceived need for reducing problems of bed sore formation, a variety of devices and methods have been proposed to reduce long-term, large force or pressure concentrations on a person&#39;s body. For example, Cottner et al, in U.S. Pat. No. 5,243,723, Sep. 17, 1993, Multi-Chambered Sequentially Pressurized Air Mattress With Four Layers discloses an air mattress which has two lower layers constantly pressurized at about 1 psi gauge, and two upper layers that each have serpentinely shaped, transversely disposed interdigitated membrane areas which are cyclically and alternately pressurized with varying air pressure in a push-pull fashion which creates a standing wave of variation in support force for a patient, with the intended purpose of minimizing formation of decubitus sores. The standing waves produced by alternate inflation and deflation of adjacent interdigitated members shifts support forces up and down, leaving the average maximum reaction support force concentrations on parts of a patient&#39;s body unchanged. Moreover, the continuous oscillating motion of the interdigitated members exerts continuous reciprocating tangential or shear forces on parts of a body supported by adjacent interdigitated members, which shear force can collapse blood vessels and thus reduce blood circulation, which can contribute to the formation of shear-force induced decubitus sores. 
         [0008]    The present invention was conceived of to provide air mattresses which provide soliton traveling waves of support-forces for the body of a person supported by the mattress, which can reduce maximum force concentrations of the type that can lead to the formation of decubitus bed sores. 
       OBJECTS OF THE INVENTION 
       [0009]    An object of the present invention is to provide a soliton traveling wave air mattress apparatus which includes an inflatable air mattress that has a multiplicity of hermetically isolated air bladder cells and a pressure pulse generator which dynamically varies inflation pressures in the cells to thus create a soliton traveling wave of support-force which travels over the upper surface of the mattress. 
         [0010]    Another object of the invention is to provide a soliton traveling wave air mattress apparatus which includes a mattress that has a multiplicity of laterally disposed, hermetically isolated air bladder cells, and an air pressure pulse generator which sequentially varies air pressure in the cells to thus create longitudinally traveling soliton body support-force waves on the upper surfaces of the air bladder cells. 
         [0011]    Another object of the invention is to; provide a soliton traveling wave air mattress comprised of a planar matrix of air bladder cells which are hermetically isolated from one another, and a pressure pulse generator for varying air pressures in the cells by pressure pulses which are applied sequentially to individual cells or groups of cells to create on the upper surfaces of the cells soliton traveling waves of support-force for the body of a person supported by the mattress, the soliton traveling waves being directable longitudinally, laterally, obliquely, or in other directions on the surface of the mattress. 
         [0012]    Another object of the invention is to provide a soliton traveling wave air mattress which has a matrix of air bladder cells, each of which has associated therewith a surface reaction force-sensor, the sensors being useable to calculate a gradient vector of surface reaction forces measured by the sensors, and a pressure pulse generator for directing waves of negative pressure pulses to air bladder cells along the path of the gradient vector to thus create a soliton traveling wave of support force reduction which travels in the direction the gradient vector. 
         [0013]    Another object of the invention is to provide a soliton traveling wave air mattress apparatus which has a multiplicity of individually inflatable and deflatable air bladder cells that are hermetically isolated from one another, and a wave generator including a pressure pulse generator and air bladder selector valves which introduces a wave of air pressure pulses into selected sequences of cells to thus create a traveling wave of body support force reduction directed along the gradient path. 
         [0014]    Another object of the invention is to provide a soliton traveling wave air mattress apparatus which has a multiplicity of individually inflatable and deflatable air bladder cells that are hermetically isolated from one another, and a wave generator which includes a pressure pulse generator and a selector valve mechanism which introduces pulses of air pressure sequentially into selected air bladder cells in a sequential fashion that produces a soliton traveling pressure wave in the air bladder cells which in turn causes the upper surfaces of the air bladder cells to produce thereon a corresponding soliton traveling wave of support force for a body supported on the upper surface of the air mattress. 
         [0015]    Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims. 
         [0016]    It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferrable from the description contained herein be included within the scope of the invention as defined by the appended claims. 
       SUMMARY OF THE INVENTION 
       [0017]    Briefly stated, the present invention comprehends a method and apparatus for alleviating formation of bed sores or decubitus sores on parts of the body of a person such as a medical patient who is supported in a relatively immobile recumbent position on a hospital bed for long periods of time. The apparatus according to the present invention includes an air mattress which is constructed from individually inflatable and deflatable air bladder cells which are arranged in a rectangular array having an upper horizontal patient support surface. The individual air bladder cells are inflated to suitable quiescent pressure levels which provide comfortable support for the body of a recumbent patient. The quiescent or bias pressure levels of the several air bladder cells may be individually adjusted to values which minimize the sum of maximum reaction force concentrations exerted on the body of a patient, as measured by an array of force or pressure sensors which may be associated with the array of air bladder cells. 
         [0018]    According to the invention, air pressure in each of the cells is cyclically varied in a manner which causes the support forces afforded by the mattress for a human body to have superimposed on quiescent static or bias values time-varying pressure components to thus produce soliton traveling waves of support force superimposed on the static support forces. Soliton traveling wave components of a quiescent support force are produced by varying in a pre-determined time sequence air pressure in sequences of individual air bladder cells according to pre-determined programs which control pressurized air inlet to and exhausted from individual air bladder cells via electrically controlled valves. 
         [0019]    For example, to produce a soliton traveling wave of support force reduction which travels from the head-end towards the foot-end of the mattress, air pressure in a first laterally disposed zone of air bladder cells located at an end of the longitudinal axis of the mattress near the patient&#39;s head is momentarily reduced to produce a pressure reduction pulse, followed by a reduction of air pressure in air bladder cells located in longitudinal zones successively closer to the foot-end of the mattress, and so forth, until a pressure reduction pulse occurs in a last longitudinal zone of air bladder cells near the foot-end of the mattress. The soliton traveling pressure wave pulse cycle and resultant soliton traveling support force wave cycle can be activated intermittently, such as once every hour, continuously in groups of several cycles periodically or in response to sensor measurements of reaction forces exerted on a patient. 
         [0020]    In one embodiment of the invention, the air bladder cell matrix will have at least two and preferably three parallel longitudinally disposed zones located side-by-side, and preferably have at least 3 and preferably 4 or more laterally disposed zones. For example, a 3 column×4 row array of 12 air bladder cells which has four longitudinally arranged, laterally disposed zones each three-cells wide enables soliton traveling support force waves to be propagated longitudinally, i.e., head-to-foot, or foot-to-head, laterally, i.e., left-to-right and right-to-left, and obliquely. 
         [0021]    Under computer program control, the air pressure in individual air bladder cells, or in groups of cells, such as in all or some of the cells in a row or column, can be temporarily varied from quiescent values of air pressure in a wide variation of time sequences to thus produce a wide variety of soliton waves of patient support forces which travel over the upper surface of the mattress. The traveling soliton support wave patterns can be optimized to alleviate or minimize the formation of decubitus sores which can result from long periods of large static support pressures on parts of a patient&#39;s body. 
         [0022]    In a simple example, the pressure in all three of the laterally arranged air bladder cells in the first, head-end longitudinal zone of a 3×4 matrix air mattress may be reduced from quiescent steady state values by a pulse of negative air pressure input to the cells in that zone for a period of several seconds. At the end of the first air pressure pulse, air pressures in the cells may be restored to their original bias or quiescent values, which have been previously adjusted to provide comfortable support of a patient. 
         [0023]    After an initial pressure pulse has been applied to a first air bladder cell or group of cells, similar pressure reduction pulses are applied sequentially to transverse zones 2, 3 and 4. This sequence of air pressure reduction pulses results in a soliton traveling wave of support forces reduction which travels longitudinally from the head-end to the foot-end of the mattress. 
         [0024]    The traveling waves of air pressure reduction pulses in the air bladder cells can be performed as a single cycle, at pre-determined times, repeated for several cycles, or performed continuously for pre-determined time periods. Also, the time interval between an air pressure reduction pulse in one zone of air bladder cells and the initiation of an air pressure pulse in a subsequent zone in a pre-selected spatial sequence need not be zero, as it would be in a traveling wave which characterizes water waves, but may, for example, have a finite, selectable, value. In other words, the duty cycle of a pulse generator used to activate air pressure control valves to thus apply a sequence of air pressure pulses to a sequence of air cell bladder zones can be as small as desired. Or, put another way, the time interval between successive pressure pulses applied to successive cells or group of cells, can be as long as desired. 
         [0025]    According to the invention, soliton traveling waves of air pressure pulses which decrease for pre-determined time intervals and repetition rate, the maximum reaction force concentrations on parts of a human body can be programmed to travel longitudinally from head-to-foot, as described in the simplified example above, or in the opposite, foot-to-head longitudinal direction on the mattress surface. As stated above, longitudinally traveling soliton body support force waves are produced by varying the air pressure simultaneously in each air bladder cell in a first transverse row of cells, subsequently varying the air pressure in the air bladder cells in a longitudinally adjacent row of cells, and so forth, until the soliton wave of support forces on parts of a patient&#39;s body has traversed the entire length or a selected segment of the length of the mattress. 
         [0026]    In an exactly analogous fashion, air pressure in laterally adjacent or spaced apart longitudinally disposed columns of adjacent air bladder cells may be sequentially varied to produce laterally traveling waves of body support forces. Also, by sequentially varying air pressure in obliquely located air bladder cells, obliquely soliton traveling waves of body support forces may be generated using the soliton traveling wave air mattress according to the present invention. 
         [0027]    According to another aspect of the present invention, an optional force sensor array is optionally provided which has individual surface reaction force sensors associated with individual air bladder cells, in vertical alignment with individual cells. The array of reaction force sensors, which produce electrical signals proportional to reaction forces exerted by the mattress on various parts of a patient&#39;s body supported by the individual cells, may be used to create a map of body reaction force concentrations. 
         [0028]    The measured values of reaction forces may also be used to create a segmented measured reaction force gradient vector. The reaction force gradient vector may then be used to calculate a path sequence for producing a soliton traveling wave of air pressure in a sequence of air bladder cells along the reaction force gradient vector. 
         [0029]    Since a measured reaction force gradient vector may not necessarily include all of the air bladder cells in an array, and may in some cases be directed between non-adjacent air bladder cells, soliton traveling waves of air pressure may be directed individually to only a small number of the total air bladder cells in an array, some or all of which cells may be non-adjacent. In this way, patient body support reaction forces exerted by the air mattress may be momentarily and periodically reduced in an efficient manner which does not require varying air pressure in all of the air bladder cells in an array. 
         [0030]    For example, if reaction force sensors determine that a maximum reaction force is exerted by a first cell, and the force gradient vector from that maximum is directed through three additional cells, some of which may be non-adjacent, an air pressure wave need be directed only to those four air bladder cells to thus create a soliton traveling support force reduction wave which travels over just the four cells. For reasons stated above, the four cells need not necessarily be vertically or horizontally aligned, or adjacent to one another. 
         [0031]    According to the invention, a basic embodiment of the soliton traveling wave air mattress, which need not have reaction force sensors, may also be programmed to simulate relaxing motions. Thus, longitudinal traveling soliton support pressure waves in the mattress may be programmed to simulate motions corresponding to floating on a surf wave, and may be accompanied by surf sounds. Also laterally traveling soliton support force pressure waves can be programmed to simulate gentle rolling or rocking motions of a boat and may be accompanied by water sloshing sounds and/or sounds simulating creaking oarlocks. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  is a partly schematic, partly perspective view of a traveling wave air mattress apparatus according to the present invention. 
           [0033]      FIG. 2A  is a fragmentary, partly diagrammatic upper plan view of an air mattress component of the air mattress apparatus of  FIG. 1 . 
           [0034]      FIG. 2B  is a fragmentary, partly diagrammatic upper plan view of a first modification of the air mattress of  FIG. 2A . 
           [0035]      FIG. 3A  is a timing diagram showing relative timing and amplitudes of negative air pressure pulses for producing soliton traveling body support force waves in the apparatus of  FIG. 1 . 
           [0036]      FIG. 3B  is a timing diagram similar to  FIG. 3A  but showing positive pressure pulses for producing positive soliton traveling body support force waves. 
           [0037]      FIG. 4  is a view similar to that of  FIG. 2B , but showing a second modification of the air mattress of  FIG. 2A  having a second arrangement of individual inflatable air cells, in which each transversely disposed row consists of two cells. 
           [0038]      FIG. 5  is a view similar to  FIG. 4 , showing a third arrangement of air cells in which each row consists of four cells. 
           [0039]      FIG. 6  is a partly schematic, partly perspective view of a modification of the traveling wave air mattress apparatus of  FIG. 1 , which is suitable for use in health care facilities. 
           [0040]      FIG. 7A  is a partly diagrammatic upper plan view of an air mattress component of the air mattress of  FIG. 6 . 
           [0041]      FIG. 7B  is a timing diagram showing relative timing of pressure pulses and resulting traveling soliton body support force waves of the apparatus of  FIG. 6 . 
           [0042]      FIG. 8  is a diagrammatic upper plan view of a two-column by six row modification of the air mattress of  FIG. 7A , showing a hypothetical reaction force gradient vector thereon. 
           [0043]      FIG. 9  is timing diagram showing a sequence of negative air pressure pulses applied to the mattress of  FIG. 8  in the direction of the reaction force gradient vector shown in  FIG. 8 . 
           [0044]      FIG. 10  is a partly diagrammatic view of a soliton wave generator for the apparatus shown in  FIG. 6 , which includes a reciprocating air pulse generator. 
           [0045]      FIG. 11A  is a partly diagrammatic view of another embodiment of a traveling wave air mattress apparatus according to the present invention, which includes a pressure/vacuum pump, showing valves of the apparatus configured for producing negative air pressure in pulses to air bladder cells of an air mattress. 
           [0046]      FIG. 11B  is a view similar to that of  FIG. 11A , but showing valves configured for producing positive pressure variations in air bladder cells. 
           [0047]      FIG. 12  is a partly diagrammatic view of a third, modular embodiment of a soliton traveling wave air mattress according to the present invention. 
           [0048]      FIG. 13  is a partly diagrammatic view of a soliton wave generator and air pressure pulse generator module of the apparatus of  FIG. 12 . 
           [0049]      FIG. 14  is a partly diagrammatic view of a first type mattress interface module and inflatable air mattress which together with the soliton wave generator and air pressure pulse generator module of  FIG. 13  comprise a third embodiment of a soliton traveling wave air mattress according to the present invention. 
           [0050]      FIG. 15  is a partly diagrammatic view of a second type mattress interface module and inflatable air mattress which together with the soliton wave generator and air pressure pulse generator module of  FIG. 13  comprise a first variation of a third embodiment of a soliton traveling wave air mattress according to the present invention. 
           [0051]      FIG. 16  is a partly diagrammatic view of a third type of an air mattress interface module and inflatable air mattress which together with the soliton wave generator and air pressure pulse generator module of  FIG. 13  comprise a second variation of a third embodiment of a soliton traveling wave air mattress according to the present invention. 
           [0052]      FIG. 17  is a partly diagrammatic view of a fourth type of air mattress interface module and inflatable air mattress which together with the soliton wave generator and air pressure pulse generator module of  FIG. 13  comprise a third variation of a third embodiment of a soliton traveling wave air mattress according to the present invention. 
           [0053]      FIG. 18  is a timing diagram showing a first, active-deflation operating mode of the soliton wave generator of  FIG. 13 . 
           [0054]      FIG. 19  is a timing diagram showing a second, passive-deflation operating mode of the soliton wave generator module of  FIG. 13 . 
           [0055]      FIG. 20  is a timing diagram showing relative timing and amplitudes of a sequence of air pulses input sequentially into individual air bladder cells of the air mattress of  FIG. 17 , to thus produce a soliton traveling body support force wave on the upper surface of the air mattress. 
           [0056]      FIG. 21A  is a fragmentary, partly diagrammatic side elevation view of the air mattress of  FIG. 17 , showing the mattress being inflated from an initial deflated state to a fully inflated state by a first sequence of deflating and inflating pulses of the type shown in  FIG. 20 . 
           [0057]      FIG. 21B  is a diagrammatic view similar to that of  FIG. 21A , showing the progression of a soliton traveling support force-reduction wave traveling in a left-to-right, head-to-foot direction produced on the upper surface of the air bladder cells of the mattress resulting from a sequence of deflating and re-inflating pressure pulses of the type shown in  FIG. 20  being input to a series of individual laterally disposed air bladder cells of the air mattress beginning at the left, head-end of the mattress and ending at the right, foot-end of the air mattress. 
           [0058]      FIG. 21C  is a partly diagrammatic view showing a body support force-reduction wave produced on the surface of the air mattress of  FIG. 17  by introducing a sequence of air pressure pulses of the type shown in  FIG. 20  to a series of pairs of adjacent air bladder cells of the air mattress, beginning at the left, head-end of the air mattress and ending at the right, foot-end of the air mattress. 
           [0059]      FIG. 21D  is a view showing a downward, head-to-foot body support force-production wave produced on the surface of the air mattress of  FIG. 17  in which odd number air bladder cells  1 ,  3 , . . . through  19  are deflated and re-inflated in a first soliton force-reduction wave, and even number air bladder cells  2 ,  4 , . . . through  20  are deflated and re-inflated in a second soliton body support force-reduction wave. 
           [0060]      FIG. 21E  is a view similar to  FIG. 21B  but showing a soliton body support force wave traveling in a toe-to-head direction produced on the surface of the air mattress by sequentially deflating and re-inflating air bladder cells by pressure pulses beginning at the foot-end of the air mattress, and ending at the head-end of the air mattress. 
           [0061]      FIG. 21F  is a view similar to  FIG. 21A , showing upwardly and downwardly soliton traveling body support force waves being produced on the surface of the air mattress by simultaneously introducing upwardly and downwardly traveling soliton waves of air pressure deflation/re-inflation pulses into the air bladder cells of the air mattress. 
           [0062]      FIG. 22  is a diagram showing plots of pressure versus time for deflation/re-inflation cycles of a series of air bladder cells of the traveling wave air mattress of  FIG. 12 . 
           [0063]      FIG. 23  is a diagrammatic view showing deflation pressure versus time curves of an air bladder cell loaded with different body weights. 
           [0064]      FIG. 24  is a timing diagram showing a sequence of negative pressure pulses applied to a sequence of air bladder cells of the air mattress of  FIGS. 12 and 13 , in which certain individual air bladder cells that have been determined during a previous soliton traveling wave pulse sequence to have been subjected to weight load forces below a pre-determined minimum value are omitted from the sequence of air bladder cells to which negative air pressure pulses are applied, thus decreasing the time intervals between which air bladder cells that support pre-determined minimum weight loads are deflated and re-inflated. 
           [0065]      FIG. 25  is a diagrammatic view of a first modification of the pressure pulse generator component of the apparatus shown in  FIG. 13 . 
           [0066]      FIG. 26  is a diagrammatic view of a second modification of the pressure pulse generator component of the apparatus shown in  FIG. 13 . 
           [0067]      FIG. 27  is a diagrammatic view of a third modification of the pressure pulse generator component of the apparatus in  FIG. 13 . 
           [0068]      FIG. 28  is a simplified upper plan view of a modification of the air mattress of  FIG. 2A , which has concentric oval ring-shaped air bladder cells. 
           [0069]      FIG. 29  is an upper plan view of a modification of the air mattress of  FIG. 28 , in which air bladder cells of the array are segmented into quadrants. 
           [0070]      FIG. 30  is a simplified upper plan view of another modification of the air mattress of  FIG. 2A , which has concentric circular ring-shaped air bladder cells. 
           [0071]      FIG. 31  is an upper plan view of a modification of the air mattress of  FIG. 30 , in which air bladder cells of the array are segmented into quadrants. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0072]      FIG. 1  is a perspective, partly diagrammatic view of a basic embodiment  10  of a soliton traveling wave air mattress apparatus according to the present invention. The apparatus includes an air mattress  20  and a mattress inflation control apparatus  27 . As shown in  FIG. 1 , mattress  20  has in upper plan view an outline shape similar to that of a typical hospital mattress, i.e., a longitudinally elongated rectangle having a length of about 80 inches and a width of about 30 to 36 inches. However, the exact dimensions and shape of mattress  20  are not critical, and may differ from the example given. 
         [0073]    As shown in  FIG. 1 , mattress  20  has a generally flat rectangular base panel  21  which may be made of a sheet of a durable flexible plastic material such as polyurethane or polyvinyl. Base panel  21  has protruding upwards therefrom a longitudinally arranged series of laterally elongated, rectangular plan view air bladder cells  22 . As shown in  FIG. 1 , each air bladder cell  22  extends from the left-hand longitudinally disposed edge  23  to the right-hand edge  24  of mattress  20 . As is also shown in  FIG. 1 , when air bladder cells  22  are inflated, e.g., to a pressure of about 1 psi gauge, the cells have in a vertical longitudinal sectional view generally the shape of a laterally elongated semi-cylinder which has an arcuately curved, convex upper semi-cylindrical surface  25  that extends upwards from base panel  21 . 
         [0074]    Although the transverse cross-sectional shape and size of air bladder cells  22  is not critical, a typical size and shape for use in a 80 inch×36 inch mattress having 6 laterally disposed air cells would be a semi-cylinder having a base diameter of about 13 inches and a length of about 36 inches, as shown in  FIGS. 1 and 2A . 
         [0075]    Confronting laterally disposed edges  26  of the air bladder cells  22  may contact each other, or as shown in  FIGS. 1 and 2A , edges  26  may optionally be spaced longitudinally apart a short distance, e.g., 1 inch. 
         [0076]    Referring to  FIG. 1 , it may be seen that traveling wave air mattress apparatus  10  includes a mattress inflation control apparatus  27  for inflating and deflating air bladder cells  22  to individual pressure levels which provide comfortable support for a person supported by mattress  20 . Apparatus  10  also includes a wave generator apparatus  44  for varying air pressure in inflatable air bladder cells  22  in a manner which results in a soliton traveling wave of support-force to propagate on the upper surface  28  of the mattress formed by the upper surfaces  25  of air bladder cells  22 . Preferably mattress  20  is enclosed by a soft fabric mattress cover, and an optional thin layer of foam rubber between the upper surface of air bladder cells  22  and an inside surface of the mattress cover. 
         [0077]    According to the invention, wave generator apparatus  44  is used to produce a soliton traveling wave of support force for the body of a person supported on the upper surface  28  of mattress  20  by sequentially varying the air pressure in selected paths of individual air bladder cells  22 , for example from the head-end to the foot-end of the mattress, in predetermined time sequences. 
         [0078]    As shown in  FIG. 1 , mattress inflation level control apparatus  27  includes a source of pressurized air  30 , which is preferably an air compressor but may optionally be a tank containing a pressurized gas such as air or nitrogen. Air pressure source  30 , which is preferably a compressor driven by an electric motor  55 , has an outlet port  31  connected through an outlet tube  32  to the inlet port  33  of a selector manifold  34 . Selector manifold  34  has multiple outlet ports  35 , e.g., six outlet ports  35 - 1 ,  35 - 2 ,  35 - 3 ,  35 - 4 ,  35 - 5  and  35 - 6 , which are individually connected through tubes to the inlet ports  36 - 1  through  36 - 6  of a group of cell selector valves  37 - 1  through  37 - 6 . 
         [0079]    Each cell selector valve  37 , which may be a simple on/off gate valve, has an outlet port  38  which is connected to a first, e.g., upper inlet tube port  39  of a Y-tube coupler  40 . Each Y-tube coupler  40  has a second, lower inlet tube port  41  and an outlet tube port  42  which is connected to an inflation port  43  of an individual air bladder cell  22 . Thus for example, outlet tube port  42 - 1  of Y-tube coupler  40 - 1  is connected with air pressure-tight fittings to air inlet port  43 - 1  of the first, head-end air bladder cell  22 - 1  of traveling wave air mattress  20 , and so forth. 
         [0080]    As will be explained in further detail below, each cell inflation selector valve  37  is controlled by electrical signals issued by an electronic control module  51  to inflate and deflate individual air bladder cells  22  to quiescent values which provide comfortable support for a person reclining on mattress  20 . 
         [0081]    Referring still to  FIG. 1 , it may be seen that wave generator apparatus  44  includes a pressure pulse generator  45  for creating negative and optionally positive pulses of air pressure in an outlet port  46  which are conducted to second, lower inlet port tubes  41  of Y-tube couplers  40 . The output port  46  of pressure pulse generator  45  communicates with a source of pressurized air, such as a closed chamber part of a cylinder located on a side of a piston or diaphragm which is longitudinally movable in the cylinder in response to forces exerted on the piston by a linear actuator. 
         [0082]    Wave generator apparatus  44  includes a wave generator controller  44 A for issuing electrical command signals to pressure pulse generator  45  and other components of the wave generator apparatus. Wave generator controller  44 A is preferably a computer, microprocessor, or programmable logic controller (PLC), and preferably communicates with or is optionally replaced by a computer  52  of inflation control apparatus  27 . 
         [0083]    The magnitude of the negative air pulses need not be any greater than the maximum intended inflation pressure of any air bladder cell  22 . For example, if the intended maximum inflation pressure of any of air bladder cells  22 - 1  through  22 - 6  is 1 psi, the negative pulse-generating capability of pressure pulse generator  45  should be sufficient to draw all of the air from an air bladder cell  22 , e.g., about 1.38 cubic feet, within a pre-determined maximum time limit, e.g., 10 seconds. In actuality, the exhaustion rate of pressure pulse generator  45  may be less, since some modes of operation of the invention envision only a fractional reduction of the pressure in an air bladder cell  22  from a quiescent value, e.g., one-half. 
         [0084]    According to the invention, after a negative pressure pulse has been applied to an air bladder cell  22 , the air pressure in that cell may be changed to a quiescent or bias valve different than pressure at the beginning of the pulse, but is typically restored to the original bias pressure valve. In either case, a single pressure pulse generator  45  within wave generator  44  may be used in conjunction with pulse selector valve array  47  to route negative or positive pulses of air pressure to selected air bladder cells  22 . Thus, as shown in  FIGS. 1 and 2 , pressure pulse generator  45  has a single outlet port  46  which is connected through a manifold  48  and pressure pulse selector valves  49  of valve array  47  to second, lower inlet port tubes  41  of selectable Y-tube couplers  40 . Each pulse selector valve  49 , which may be a simple on/off gate valve, is controlled by electrical signals issued by wave generator controller  44 A. 
         [0085]    Referring to  FIG. 1 , it may be seen that mattress inflation control apparatus  27  includes an electronic control module  51  for adjusting the static or quiescent inflation pressure levels of air bladder cells  22  to values which provide comfortable support to a person lying on the upper surface  28  of air mattress  20 , and for controlling functions of wave generator  44 . 
         [0086]    As shown in  FIG. 1 , electronic control module  51  preferably includes a computer  52  or a similar programmable electronic component such as a microprocessor or programmable logic controller (PLC) which emits through an interface module  53  command signals for actuating various components of the apparatus  27 , such as compressor  30 , cell inflation selector valves  37  and optionally pulse selector valves  49 . Computer  52  may also receives through interface module  53  various feedback signals such as valve configuration and compressor outlet pressure from a pressure transducer  54 , etc. 
         [0087]    Depending upon whether mattress system  10  is to be configured as a relatively inexpensive, relaxation-inducing system, or a precision therapeutic system for use in hospitals and similar locations, the system  10  may include less or more complexity and cost-increasing components. For example, while a low-cost soliton traveling wave mattress  20  intended for recreational or relaxation purposes according to the present invention would not require body support-force sensors, embodiments of the invention intended for use in hospital environments would desirably include a force sensor array that used at least one force sensor associated with each air bladder cell of the mattress, to monitor reaction support forces exerted by the air bladder cells on the body of a patient. 
         [0088]      FIG. 2B  illustrates a modification  10 B of the traveling wave air mattress  10  according to the present invention. As shown in  FIG. 2B , each of the air bladder cells  22 B of modified air mattress  20 B has in addition to inlet port  43  a second inlet port  43 B for connection directly to a separate pulse selector valve  49 . This construction eliminates a requirement for Y-tube couplers  40 , since each cell pulse selector valve  37  may be connected directly to a separate bladder cell inflation port  43 B. However, the embodiment which employs Y-couplers as shown in  FIGS. 1 and 2A  is preferred, because it minimizes the number of tubes connected to mattress  20 . 
         [0089]      FIG. 3A  is a timing diagram showing a typical pattern of variation of air pressure in individual transverse rows of air bladder cells  22  of the basic, relaxational embodiment of soliton traveling wave air mattress system  10  shown in  FIGS. 1 and 2A . Referring to  FIG. 3A , mattress inflation control apparatus  27  is first directed by computer  52  to switch on electrical power to drive motor  55  of air compressor  30 . By employing command signals issued from computer  52  through interface module  53  to air bladder cell selector valves  37 , individual air bladder cells  22 - 1 ,  22 - 2 ,  22 - 3 ,  22 - 4 ,  22 - 5  and  22 - 6  may be inflated to pre-determined air pressure values monitored by compressor pressure transducer  54 . As shown in  FIG. 7B , the initial quiescent or bias values of pressure to which individual air bladder cells  22  are inflated need not all be the same. 
         [0090]    After the individual air bladder cells  22 - 1  through  22 - 6  have been inflated to pre-determined quiescent values, command signals may be initiated by computer  52  and issued through interface module  53  and a wave generator controller  44 A to initiate operation of wave generator  44 . For example, a first step in the operation of wave generator  44  would be to actuate a first pressure pulse selector valve  49  of pressure pulse generator  45  to thus provide an air flow path between outlet port  46  of pressure pulse generator  45  through lower inlet port tube  41 - 1  of Y-tube coupler  40 - 1  to air inlet port  43 - 1  of first air bladder cell  22 - 1 . 
         [0091]    Next, as shown in line  1  of  FIG. 3A , pressure pulse generator  45  is powered on at a time T 1  in response to a command signal from computer  52 . As may be understood by referring to  FIG. 10 , applying power to pressure pulse generator  45  causes a solenoid, pneumatic actuator cylinder or stepper motor-driven linear actuator to move a diaphragm or piston  183  in a closed cylinder  180  which has on a first active side  188  of the piston  183  a port  146  connected through a pulse selector valve  215  of pulse selector valve array  47  to the second, lower inlet port tube  41 - 1  of Y-junction coupler  40 - 1  connected to inflation port  43 - 1  of air bladder cell  22 - 1 . Pressure pulse generator  45  may also have located on a second, down-stroke side  181  of piston  183  a second, storage chamber  61 , which may be optionally connected through air-tight fittings and an optional valve to a pneumatic accumulator  62 . 
         [0092]    As shown in  FIG. 3A , a first air pressure pulse  63 - 1  emitted by pressure pulse generator  45  and conducted to a first air bladder cell  22 - 1  has generally an amplitude which varies as a function of time as the negative half of a sine wave. However, the shape of air pressure pulse  63  may optionally be varied under computer control to approximate that of a rectangle, trapezoid, triangle, or other such shape. 
         [0093]    The magnitude of air pressure pulse  63  is variable under computer control to a desired value, but typically would be about half or less than the maximum quiescent or bias pressure level in a given air bladder cell or group of air bladder cells. For example, for a quiescent air pressure level of 1 psi in a cell  22  of mattress  20 , the amplitude of air pressure pulse  63  would typically be about 0.5 psi or less. 
         [0094]    As shown in  FIG. 3A , first air pressure pulse  63 - 1  is a negative-going pulse that temporarily reduces the air pressure in air bladder cell  22 - 1 . It is envisioned that for use of mattress  20  in hospital beds or other such therapeutic applications, the pulse of air pressure produced by pressure pulse generator  45  would typically be negative, to thus temporarily reduce the reaction force exerted on a patient&#39;s body by a particular air bladder cell  22  or a group of air bladder cells  22 . However, as shown in  FIG. 3B , the pulse generator  45  can be configured and commanded to alternatively produce positive-going pressure pulses  64 , for applications such as relaxational uses of mattress  20 . 
         [0095]    The period of pulse  63  may be adjusted to any suitable value under computer control. Thus, the time interval between the beginning, T 1  and the end, T 2  of pressure pulse  63  shown in line  1  of  FIG. 3A  can be any desired value, e.g., several seconds to several minutes or longer. 
         [0096]    Referring now to the graph in line  2  of  FIG. 3A , it may be seen that pulse generator  45  is used to apply a second air pressure pulse  63 - 2  in a sequence of air pressure pulses to a second air bladder cell  22 - 2  at a programmable time T 3 . Beginning time T 3  of second pulse  63 - 2  may be coincident with the end of pulse  63 - 1 , or delayed to occur at any desired programmable time period later than T 2 , e.g., 1 second, several seconds, or longer. In exactly the same manner, successive air pressure pulses  63 - 3 ,  63 - 4 ,  63 - 5 , and  63 - 6  may be applied to air bladder cells  22 - 3 ,  22 - 4 ,  22 - 5  and  22 - 6 , which cells are located progressively further towards the foot-end of air mattress  20  from the head-end air bladder cell  22 - 1 . 
         [0097]    As shown in graphs in lines  1 - 6  of  FIG. 3A , a negative pressure wave is produced in a continuous sequence of air bladder cells  22 - 1  through  22 - 6  to thus produce a soliton traveling wave of reduction in support force for the body of a person supported by air mattress  20 . However, it should be understood that characteristics of the traveling pressure wave produced by pressure pulse generator  45  of pressure wave generator  44  and hence characteristics of soliton traveling body force support waves may readily be modified in real time by suitably programming computer  52 . For example, referring to  FIGS. 2A and 9 , the traveling pressure wave may be programmed to skip over selected air bladder cells, such as even cells  22 - 2 ,  22 - 4 , by not applying negative pressure pulses to those cells. In fact, apparatus  10  may be programmed to produce sequences of air pressure pulses which travel in any arbitrary path between air bladder cells  22 . 
         [0098]    As may be readily understood by viewing  FIG. 3B , the pressure pulses produced by pressure pulse generator  45  may optionally be positive-going ( 64 - 1  through  64 - 6 ) rather than negative-going, provided the quiescent pressure levels of air bladder cells  22  are initially adjusted to values less than maximum inflation levels. 
         [0099]    Also, pressure wave generator  44  may optionally be directed by computer  52  to produce overlapping pressure pulses, parts of which are applied simultaneously to more than two cells or zones of cells to thus produce an overlapping soliton body support-force wave. For example, referring to  FIG. 3A , the initiation time T 3  of a of second air pressure pulse  63 - 2  may occur between beginning and ending times T 1  and T 2  of first air pressure pulse  63 - 1 , to thus produce a composite soliton traveling support wave pulse which begins at T 1  and ends at T 4 , and is longer than the individual pulses shown in  FIG. 3A . 
         [0100]    As shown by the dashed lines in  FIGS. 3A and 3B , the pulse generator  45  may be programmed to cause some or all of the air bladder cells  22  that have received a pulse of air pressure variation to retain the pressure level in the cell at its maximum changed value, or at a value intermediate between the initial quiescent level and the maximum changed level. 
         [0101]    Pressure wave generator  44  may also be directed by computer  52  to produce two or more traveling support force waves which travel simultaneously on the upper surface  28  of mattress  20 . Thus, for example, by programming computer  52  to direct wave generator  44  to sequentially apply air pressure pulses to longitudinally descending and ascending pairs of air bladder cells, a first soliton traveling wave of support force may be launched on upper surface  28  an air mattress  20 , which travels from the head-end to the foot-end of the mattress, and a second soliton traveling wave of support force launched simultaneously, which travels from the foot-end to the head-end of the mattress. The foregoing pair of simultaneous traveling soliton support waves may be produced by simultaneously applying pulses of air pressure to the following pairs of cells; ( 22 - 1  and  22 - 6 ), ( 22 - 2  and  22 - 5 ), ( 22 - 3  and  22 - 4 ), ( 22 - 3  and  22 - 4 ), ( 22 - 2  and  22 - 5 ), and ( 22 - 1  and  22 - 6 ). 
         [0102]      FIG. 4  illustrates a second modification  20 C of air mattress  20  shown in  FIGS. 1 and 2A , which has a series of six longitudinally arranged, transversely disposed rows, each having 2 side-by-side air bladder cells  22 C, for a total of 12 air bladder cells. 
         [0103]      FIG. 5  illustrates another modification  20 D of air mattress  20  shown in  FIGS. 1 and 2A , which has six transversely disposed rows of 4 side-by-side air bladder cells  22 D, for a total of 24 air bladder cells. 
         [0104]    As discussed above, the soliton traveling wave air mattress apparatus according to the present invention may be programmed to launch pairs of soliton support force waves which travel simultaneously in opposite directions on the upper surface of the air mattress. From this discussion, it will be readily understood that pressure wave generator  44  may be directed by computer  52  to produce laterally moving soliton traveling support force waves on the surface of an air mattress having multiple columns of air bladder cells, such as the mattresses shown in  FIGS. 4 and 5 . Moreover, it will be readily understood that according to the present invention, two or more traveling soliton support waves may be simultaneously launched on the mattresses having multiple columns, and these waves can include simultaneously existing pairs of longitudinally traveling waves, laterally traveling waves, or combinations of simultaneous longitudinally and laterally traveling waves. 
         [0105]    As shown in  FIG. 1 , wave generator apparatus  44  may be used as an accessory with an existing air mattress apparatus which includes a multi-cell air mattress  20  and an associated inflation control apparatus  27 , by interconnecting the wave generator apparatus to the inflation control apparatus using Y-couplers  40 . In this accessorized configuration, computer  51  of inflation controls module  51  can provide a signal to wave generator controller  44 A indicating when adjustment of quiescent air pressures in air bladder cells  22  has been achieved by the inflation control apparatus  27 , whereupon pulse pressure sequences causing soliton traveling wave support force waves may be initiated by pressure pulse generator  45 . 
         [0106]      FIGS. 6 and 7A  illustrate an embodiment  110  of a soliton traveling wave air mattress according to the present invention, which is a modification of the basic embodiment  10  and is suitable for use in hospitals, nursing homes and similar facilities. 
         [0107]    As shown in  FIGS. 6 and 7A , modified soliton traveling wave apparatus  110  includes a mattress  120  which may be similar in construction to the basic mattress embodiment  20  shown in  FIG. 1  and described above. For ease of explanation, the mattress shown in  FIGS. 6 and 7  is shown to have 6 transversely disposed, non-subdivided air bladder cells. However, mattress  120  actually includes a rectangular matrix of air bladder cells  122  as shown in  FIGS. 4 and 5 , rather then a single column of transversely disposed rows of air bladder cells, which enables air pressure and hence body support forces to vary only in a single, longitudinal head-to-toe direction. 
         [0108]    According to the invention, air mattress  120  intended for use in hospitals would have as shown in  FIG. 4  at least two and preferably three, four, or more separate laterally disposed columnar zones of air bladder cells, as shown in  FIG. 5 . 
         [0109]    As shown in  FIGS. 5, 6 and 7A , an example air mattress  120  has six different transversely disposed, longitudinally ordered zones which span the head-to-toe length of the mattress. Each of the six transversely disposed rows of air bladder cells  122  is partitioned into four rectangular air bladder cells, each of which is hermetically isolated from all other air bladder cells. 
         [0110]    Thus, in the example embodiment of air mattress  120  shown in  FIGS. 5 and 6 , there is a rectangular matrix array of 24 rectangularly-shaped air bladder cells  122 - 1  through  122 - 24 , each of which is hermetically isolated from all of the other air bladder cells in the array. This construction enables each of the air bladder cells  122 - 1  through  122 - 24  to be separately inflated and deflated to individually adjustable bias or quiescent levels. 
         [0111]    Apparatus  110  also has an inflation control apparatus  127  and a pressure wave generator  144  that enables air pressure pulses to be applied to individual air bladder cells  122  or groups of cells, in any desired combination and sequence. 
         [0112]    Preferably, as shown in  FIG. 6 , traveling wave air mattress  110  includes a force sensor array  170 . Force sensor array  170  is comprised of a group of individual flexible surface reaction force sensors  171 - 1  through  171 - 24 , each of which is fastened in vertical alignment with a separate one of air bladder cells  122 - 1  through  122 - 24 . Each sensor  171 - 1  through  171 - 24  is a two-terminal device which has a first output terminal  172 - 1 - 172 - 24  that is connected to an individual lead wire  173 - 1  through  173 - 24 . Each sensor  171  also has a second output terminal  174 - 1 - 174 - 24  which is connected to an individual lead wire  175 - 1  though  175 - 24 . Alternatively, the sensors  171 - 1  through  171 - 24  may be interconnected in an X-Y matrix, using 6 row-connector lead wires  176 - 1  through  176 - 6 , and 4 column-connector lead wires  177 - 1  through  177 - 4 . In either arrangement, the lead wires are used to connect sensors  171  to a sensor interface module  176  of inflation control apparatus  127 . 
         [0113]    Sensors  171 - 1  through  171 - 24  of sensor array  170  are used to monitor reaction support forces exerted on various parts of the body of a person supported by air bladder cells  122 - 1  through  122 - 24  of traveling wave air mattress  120 . 
         [0114]    Monitoring of reaction support forces exerted on a patient&#39;s body is performed when a patient first lies down on mattress  120 , and the air bladder cells  122 - 1  through  122 - 24  are inflated to quiescent or bias values which provide comfortable support to the patient; ideally by reducing reaction support forces which are above a certain desired maximum by reducing air pressure in some cells and increasing air pressure in other cells. 
         [0115]    At a pre-determined time after initial adjustment of quiescent air pressure levels in air bladder cells  122 - 1  through  122 - 24 , computer  152  of inflation control apparatus  127  generates pre-determined patterns of pressure pulses which when applied to the air bladder cells, result in production of soliton traveling waves of patient body-support forces that travel on the upper surface  28  of the mattress. 
         [0116]    The magnitude, shape, timing and other characteristics of air pressure pulses generated by pressure pulse generator  145  may in general be similar to those of the pulses described above for the basic embodiment  10  of the traveling wave air mattress. However, since the air bladder cells  122 - 1  through  122 - 24  of air mattress  120  have distinct laterally separated as well as longitudinally separated locations, traveling pressure waves and hence traveling soliton body support-force variation waves can be directed laterally and obliquely as well as longitudinally on the surface of the mattress. Moreover, as will be explained in detail below, surface reaction force sensor array  170  of air mattress apparatus  110  may be used to calculate in real time paths for reaction force support waves which can minimize long-term large-magnitude reaction forces which might be exerted on a patient&#39;s body, and thus further aid in preventing formation of decubitus sores. 
         [0117]    An example of calculating a beneficial path of a traveling pressure support wave in response to reaction force measurements using sensor array  170  may be understood by referring to  FIG. 8  and Table 1. 
         [0118]      FIG. 8  is a diagrammatic upper plan view of a two-column by six row modification or part of air mattress  120 . As shown in  FIG. 5 , there are twelve air bladder cells  122 - 1  through  122 - 12 , each of which has attached to and in vertical alignment therewith a separate one of an array of surface reaction force sensors  171 - 1  through  171 - 12 , which are used to produce a pressure map of surface reaction forces exerted on a patient&#39;s body. Hypothetical example values of measured patient body support reaction forces are listed in Table 1. As shown in  FIG. 8 , a surface reaction force gradient vector is constructed using the pressure/force map values of Table 1. The tail end of the gradient vector is located in air bladder cell number  122 - 1 , since the highest surface reaction force, 1.5 kilopascals (kPa) was measured by sensor  171 - 1  in cell  122 - 1 . 
         [0119]    The second highest reaction force of 1.4 kPa was measured in cell number  122 - 4 , so the first segment of the gradient vector V is directed from cell  122 - 1  to cell  122 - 4 . 
         [0120]    The third highest reaction force of 1.3 kPa was measured in cell number  122 - 7 , so the second segment of gradient vector V is directed from cell  122 - 4  to cell  122 - 7 . 
         [0121]    The fourth highest reaction force of 1.1 kPa was measured in cell number  122 - 12 , so the third segment of gradient force vector V is directed from cell  122 - 7  to cell  122 - 12 . 
         [0122]    According to the invention the segmented gradient force vector V measured and calculated as above is used to direct computer  52  to generate a pressure reduction wave which is applied consecutively to air bladder cells  122 - 1 ,  122 - 4 ,  122 - 7  and  122 - 12 , thus producing a soliton traveling surface support reaction force reduction wave which follows the measured reaction force gradient. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 CELL NUMBER 
                 MAX REACTION FORCE, kPa 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                 1.5 
               
               
                   
                 2 
                 1.0 
               
               
                   
                 3 
                 0.9 
               
               
                   
                 4 
                 1.4 
               
               
                   
                 5 
                 0.8 
               
               
                   
                 6 
                 0.8 
               
               
                   
                 7 
                 1.3 
               
               
                   
                 8 
                 0.9 
               
               
                   
                 9 
                 0.9 
               
               
                   
                 10 
                 0.9 
               
               
                   
                 11 
                 1.0 
               
               
                   
                 12 
                 1.1 
               
               
                   
                   
               
             
          
         
       
     
         [0123]      FIG. 9  illustrates an example of a pressure pulse wave  163  which is applied by wave generator apparatus  144  to traveling wave air mattress  120  along the path of a gradient vector V calculated by computer  152  from reaction forces exerted on a patient&#39;s body and measured by sensors  171 . 
         [0124]    As shown in  FIG. 9 , traveling pressure pulse ware  163  is created by applying a first pulse  163 A of negative pressure created by pressure pulse generator  145  to air bladder cell  122 - 1  between times T 1  and T 2 . At a time T 3  following T 1  which optionally precedes T 2 , a second pulse of negative pressure  163 B is applied to air bladder  122 - 4  and continued until T 4 . In an exactly analogous fashion, a third negative air pressure pulse  163 C is applied to air bladder cell  7  between times T 5  and T 6 , and a fourth and final negative air pressure pulse  163 D is applied to air bladder cell  122 - 12  between times T 7  and T 8 . 
         [0125]    As can readily be envisioned by referring to  FIGS. 6-9 , the sequence of four negative air pressure pulses  163 A,  163 B,  163 C and  163 D applied to air bladder cells  122 - 1 ,  122 - 4 ,  122 - 7  and  122 - 12 , respectively, creates a soliton traveling wave of patient body support-force reduction. As described above, the air bladder cell air pressure reduction soliton traveling wave is directed to follow the patient reaction support force gradient vector. Accordingly, by temporarily reducing the inflation pressure of air bladder cells which are exerting the greatest support force concentrations on a patient&#39;s body, these forces, which could cause decubitus sores if left unabated for long periods of time, will be substantially reduced for time periods proportional to the product of the length of pressure reduction pulse  163  and the number of times per day that the traveling pressure pulse wave cycle is repeated. 
         [0126]    In general, during the generation of a soliton traveling body support-force variation wave by a sequence of pressure reduction pulses applied to air bladder cells  122 , pressures exerted on a patient&#39;s body by other air bladder cells, in contrast to total support forces, may increase, since the total support-forces are proportional to the fixed weight of a patient supported by the mattress and hence are constant over time intervals. Moreover, the soliton traveling wave of support-force reduction, or patient movement may shift the distribution of body reaction support-forces at the end of a soliton traveling wave cycle. For the foregoing reasons, sensor array  170  would desirably be used to continuously monitor body support reaction forces over the entire surface of mattress  120 , to thus determine whether an initially measured force gradient has shifted location, whereupon successive cycles of soliton traveling support force reduction may be propagated along the paths of newly determined body support-force gradient vectors. 
         [0127]      FIG. 10  is a partly diagrammatic view of pressure wave generator  144 , which may be substantially similar in construction to pressure wave generator  44 . 
         [0128]    As shown in  FIG. 10 , pressure wave generator  144  includes a pressure pulse generator  145  that has a longitudinally elongated, hollow circular cross-section cylinder  180  which has disposed through its length a coaxial cylindrical inner bore  181 . Bore  181  is sealed at a first, head-end of cylinder  180  by a transversely disposed circular disk-shaped cylinder head  182 , which has disposed through its thickness dimension an air passageway which comprises an outlet port  146 . 
         [0129]    As shown in  FIG. 10 , bore  181  of pressure wave generator cylinder  180  has therewithin a circular disk-shaped piston  183 . Piston  183  has an outer wall surface  184  which longitudinally slidably contacts in a hermetic seal the inner cylindrical wall surface  185  of cylinder  180 . 
         [0130]    As shown in  FIG. 10 , that side of cylinder bore  181  located between a head-end transverse surface  186  of piston  183  and the inner surface  187  of cylinder head  182  forms a cylindrically-shaped, head-space active chamber  188  which is positively pressurizable by longitudinal motion of the piston  183  towards the cylinder head  182 , and negatively pressurizable by longitudinal motion of the piston towards the transverse base or end wall  189  of cylinder  180 . 
         [0131]    As shown in  FIG. 10 , piston  183  of pressure pulse generator  145  has extending longitudinally away from base end surface  190  of the piston a tubular drive shaft  191  which extends longitudinally outwards of lower transverse annular base or end wall  189  of cylinder  180 . 
         [0132]    Pressure pulse generator  145  includes a force actuator  192  to drive piston drive shaft  191  and piston  183  longitudinally rearward within cylinder  180  to thereby produce within active chamber  188  of the cylinder a negative pressure pulse. Force actuator  192  also has the capability of moving piston drive shaft  191  forward within bore  181  of cylinder  180  to thus restore piston  183  to its original longitudinal location within bore  181  of cylinder  180 . Thus, if piston drive shaft  191  is pivotably joined to piston  183 , force actuator  192  may consist of a rotary motor coupled to the outer end  193  of piston drive shaft  191  by an eccentric coupler such as a crank. However, in a preferred embodiment of pressure pulse generator  144 , force actuator  192  has a different design and construction which provides more control of the characteristics of pressure pulses produced by movement of piston  183  in cylinder  180 . 
         [0133]    Thus, as shown in  FIG. 10 , piston drive shaft  191  of pressure pulse generator  145  has a hollow tubular construction which includes an elongated circular cross-section bore  194  that extends through the outer, rear transverse annular end wall  195  of the piston drive shaft. The piston drive shaft  191  has fixed within the lower end of bore  194  thereof a cylindrically-shaped follower or jack screw nut  195  which has through its thickness dimension a coaxial threaded bore  196 . Bore  196  of follower or jack screw nut  195  receives threadingly therein an elongated threaded lead-screw or jack-screw  197  which is rotatably driven by a stepper motor  198 . 
         [0134]    Stepper motor  198  receives drive signals from a stepper motor drive electronic module  199  of a wave generator controller  144 A which receives command signals from computer  152 . This construction of the pressure wave force actuator facilitates repositioning the rest position of piston  183  within cylinder bore  181  to a rearward or retracted position, so that the piston drive shaft  191  and piston  183  can be extended forward to produce positive pressure pulses in outlet port  146 , followed at the end of a pulse by retraction to a rearward quiescent position which reduces pressure in an air bladder cell to its quiescent pressure value. 
         [0135]    Preferably, as shown in  FIG. 10 , pressure pulse generator  145  includes optional components which enable it to introduce negative or positive air pressure pulses into individually selectable air bladder cells  122  that may be initially inflated to different quiescent pressures, and restore the inflation level to the initial quiescent pressure level at the end of a pressure pulse. Thus, as shown in  FIG. 10 , outlet port  146  of pressure pulse generator  145  is connected through a cylinder isolation valve  200  through a tubular connector fitting  201  to the inlet port  202  of a pulse selector valve array manifold  203 . Cylinder isolation valve  200  has a value actuator control input terminal lead  215  which is connected to a command signal output terminal of wave generator controller  144 A. 
         [0136]    The pressure pulse generator  145  includes a cell pressure sampling pressure transducer  204  which has a pressure probe  205  that communicates with a hollow cylindrical bore space  206  of tubular fitting  201  that is located between pulse selector valve array manifold  203  and cylinder isolation valve  200 . Cell pressure transducer  204  has an output terminal lead  207  which is connected to wave generator controller  144 A, which has a command signal output terminal that is connected to stepper motor electronic drive module  199 . Wave generator controller  144 A. is also connected to a signal input interface port of computer  152 , to provide coordination between the computer and wave generator controller. 
         [0137]    As shown in  FIG. 10 , pressure pulse generator  145  also has a pulse generator cylinder pressure sampling transducer  208  which has a pressure probe  209  that communicates with active chamber head space  188  of bore  181  of cylinder  180 . Cylinder pressure sampling transducer  208  has an output terminal lead  210  which is connected to a signal input interface port of wave generator controller  144 A. 
         [0138]    As is also shown in  FIG. 10 , pressure pulse generator  145  has a cylinder bleed valve  211  which has an inlet port  212  that communicates with active chamber  188  of cylinder  181 , an outlet port  213  which communicates with the atmosphere, and an electrical valve actuation control input terminal lead  214  which is connected to a command signal output interface terminal of wave generator controller  144 A. 
         [0139]    Optionally, as shown in  FIG. 10 , pulse generator may include a manifold isolation valve  216  between tubular fitting  201  and pulse selector manifold  203 . 
         [0140]    Operation of pressure pulse generator  145  constructed and configured as shown in  FIG. 10  is as follows. 
         [0141]    First, computer  152  issues a command which is transmitted through wave generator controller  144 A to open a selected one of pulse selector valves  149  that is connected to a selected air bladder cell  122  which is to receive a pulse of air pressure, and to open optional manifold isolation valve  216 . 
         [0142]    Second, cell pressure sampling transducer  204  is used to measure the value of quiescent air pressure in the selected air bladder cell  122 . 
         [0143]    Third, cylinder air pressure sampling transducer  208  is used to measure cylinder air pressure in active chamber  188  of cylinder  180 . 
         [0144]    Fourth, the difference in air pressures measured by air bladder cell pressure transducer  204 , and cylinder air pressure measured by cylinder air pressure transducer  208  is computed by wave generator controller  144 A or computer  152 . If the measured air pressure in cylinder active chamber  188  is less than the quiescent air pressure in a selected air bladder cell  122 , a command signal is issued to stepper motor controller  199  which causes piston drive shaft  191  and piston  183  to be extended forward within cylinder  180  to increase air pressure in active chamber  188  of the cylinder until it is equal to the quiescent air pressure in the selected air bladder cell  122 . 
         [0145]    For example, piston  183  may be extended forward in cylinder bore  181  from position  3  to position  2  in  FIG. 10 . This longitudinal position of piston  183 , where the pressures in cylinder  180  and a selected air bladder cell  122  are equalized, is defined as a first home position for the piston, prior to production of a pulse of pressurized by air pressure pulse generator  145 , and introduction of the pulse of pressurized air into a selected air bladder cell  122 . Cylinder bleed valve  211  may also receive command signals from wave generator controller  144 A to enable air flow between cylinder chamber  188  and the atmosphere, to thus facilitate pressure equalization. 
         [0146]    Fifth, as shown in  FIG. 10 , cylinder isolation valve  200  is opened in response to a command signal issued through waves generator controller  144 A by computer  152 , which also causes a command signal to issue to stepper motor driver  199 . If the command signal from computer  152  is to reduce air pressure in a selected air bladder cell  122  by producing a negative pressure pulse, piston  183  is retracted to a position such as positions  3 ,  4  or  5 . If the command signal from computer  152  is to increase pressure in a selected air bladder cell  122 , piston  183  is extended forward to a longitudinal location such as position  1  in  FIG. 10 . In either case, cylinder isolation valve  200  and optional manifold isolation valve  216  remain open during the initial movement of piston  183 . 
         [0147]    Sixth, at a predetermined time at which a pulse of air pressure into an air bladder cell is to be terminated, piston  183  is commanded to move in a direction opposite to its direction at the beginning of an air pressure pulse. For example, if the air pressure in a selected air bladder cell is to be restored to the value which it had at the beginning of a pressure pulse, piston  183  would be returned to the initial home position, such as location  2  in  FIG. 10 . However, if it is desired to return the air pressure in a selected air bladder cell  122  to a new quiescent value different from an original quiescent value, piston  183  is moved to a different location at the end of a pressure-pulse cycle. 
         [0148]    Seventh, at a predetermined time period after piston  183  has ceased movement at the end of a pressure pulse cycle, pulse selector valve  149 , optional manifold isolation valve  216 , and cylinder isolation valve  200  are closed in response to command signals received from wave generator controller  144 A. 
         [0149]    As shown in  FIG. 10 , the output port of each pulse selector valve  149  is coupled to the inlet port  143  of an air bladder cell  122  through the input tube  141  and a Y-coupler  140  which also has an input tube  139  which is coupled to an inflation control apparatus  127  that is used to initially inflate the air bladder cells to initial quiescent pressure values which provide comfortable support to a patient. However, pressure pulse generator  145  may optionally be used to inflate and deflate air bladder cells  122  to initial quiescent pressure values prior to initiation of the seven-step wave generation process described above. 
         [0150]    With this optional configuration, pulse selector valves  149  perform a dual function, initially adjusting quiescent pressure levels in individual air bladder cells  122 , and subsequently introducing a sequence of pressure pulses into the air bladder cells to create a traveling support force wave. Thus, with this optional configuration, the requirement for a separate inflation control apparatus  127  and Y-couplers  140  is eliminated, and each pulse selector valve  149  is connected directly to the port  143  of an air bladder cell  122 . 
         [0151]    The pressure pulse generator  145  of the pressure wave generator  144  described above requires a piston/cylinder displacement volume at least as large as the maximum volume of air which is intended to be simultaneously input to or removed from one or more air bladder cells  22  or  122  Consequently, pressure pulse generator  145  is ideally suited for use with air mattresses having a relatively large number e.g., 12 to 24 or more, of relatively small air bladder cells. However, for air mattresses which have a relatively small number, e.g., 4 to 6 of relatively large air bladder cells, the displacement requirements for single piston stroke deflation or inflation of one or more air bladder cells may require that the displacement volume and hence size of cylinder  180  of air pulse generator be undesirably large for some applications. 
         [0152]    For example, for an air mattresses  20  of the type shown in  FIG. 1  which has 6 air bladder cells  22  which have a semi-cylindrical shape when inflated to a normal bias pressure of 14.7 lbs./in 2  (101.3 kPascals), i.e., 1 atmosphere, a diameter of 13 inches and a lateral length of 3 feet, the volume of each air bladder cell would be about 1.276 cubic feet. Therefore, the volume of cylinder  180  of air pulse generator  185  shown in  FIG. 10  would need to be 1.276 cubic feet or larger, if operation of the pulse generator required complete deflation or re-inflation of a single air bladder cell  22  with a single stroke of piston  183  within cylinder  180 . An embodiment of a wave generator of the present invention which is useful for creating traveling support force waves in air mattresses having relatively large air bladder cells is shown in  FIGS. 11A and 11B . 
         [0153]    As shown in  FIGS. 11A and 11B , an embodiment of wave generator  244  useful for deflating and re-inflating air bladder cells  22  of a relatively large air mattress  20  of the type shown in  FIG. 1  has an air pulse generator  245  that includes an air pump  280  which has a vacuum inlet port  281  and a pressure output port  282 . An example of a suitable type of air pump  280  for use in the present application is a linear air pump which uses a magnet moving in response to time varying electromagnetic force fields produced by an alternating current to drive a piston in a reciprocating motion within a cylinder. Such pumps are described in further detail in “Mechanisms And Mechanical Devices Sourcebook.” 5 th  Edition by Neil Sclater, McGraw-Hill, New York 2011, page 374. 
         [0154]    As can be envisioned by referring to  FIGS. 11A and 11B , when a piston (not shown) moves inwardly within a cylinder (not shown) of air pump  280  in response to an attractive electromagnetic force, a negative pressure occurs in pump inlet port  281 , which may draw air through the inlet port  281  and past an inlet flapper valve  284  into the head-space  285  between the piston  286  and the inlet port. During this first, inlet part of the air pump cycle, negative pressure within head space  285  of air pump  280  also draws an outlet flapper valve  288  inwardly to a closed position which seals off communication between the pump head-space and outlet port  282 . 
         [0155]    Conversely, when the piston moves outwardly in response to a repulsive electromagnetic force, a positive pressure pulse is produced in head space  285  of cylinder  283 . The positive pressure closes input flapper valve  284  and opens output flapper valve  287 , through which a pulse of air at positive pressure is expelled through outlet port  282  of the air pump. 
         [0156]    From the foregoing description, it can be readily understood that powering air pump  280  with alternating current at a 60 Hz line frequency results in 60 pulses per second of negative air pressure occurring in inlet port  281  of the pump, and positive pulses of air pressure occurring in outlet port  282  at the same frequency but shifted 180 degrees in phase from the negative air pulses at inlet port  281 . 
         [0157]    As shown in  FIGS. 11A and 11B , soliton traveling wave generator  244  includes a pressure pulse routing assembly  290  comprised of routing valves and air conduits which are interconnected between linear air pump  280  of air pulse generator  245 , and pulse selector valves  249  on pulse selector manifold  246 . Pressure-pulse routing assembly  290  connects negative air pressure inlet port  281  of air pump  280  to a selected air bladder cell  22  during the initial, negative-going part of a negative pressure pulse applied to an air bladder cell, and connects the air bladder cell to positive pressure at outlet port  282  of the pump during the final, positive-going part of a negative pressure pulse. 
         [0158]    As is also shown in  FIGS. 11A and 11B , pressure-pulse routing assembly  290  includes three 2-way or diverter-type valves which are all similar in construction and function. Thus, as shown in  FIGS. 11A and 11B , wave generator apparatus  244  includes a first, pump inlet router valve  291  which has an output port  292  that is connected to inlet port  281  of pump  280  by a tubular pressure-tight tube  293 . Pump inlet router valve  291  has a first, upper selector-manifold inlet port  294  which is connected to a second, selector manifold router valve  311 . Selector manifold router valve  311  is connected to inlet port  246  of manifold  248  by a tubular pressure-tight tube  297 . Pump inlet router valve  291  also has a second, supply-air inlet port  298 . 
         [0159]    Also shown in  FIGS. 11A and 11B , pump inlet router valve  291  has an internal valve plate  299  which is pivotably movable by a solenoid actuator  300  in response to an electrical control signal input to an input terminal  301  of the actuator, which is connected by an electrical wire to a first valve control output port  302  of wave generator controller  244 A. 
         [0160]    Referring still to  FIGS. 11A and 11B , it may be seen that valve plate  299  has a first pivotable position in which the valve plate is pivoted counterclockwise to block air flow to supply-air inlet port  298 , and to permit air flow between selector manifold inlet port  294  and outlet port  292  of the valve. In this position, negative air pressure pulses at inlet port  281  of pump  280  are transmitted through pump inlet router valve  291 , through selector manifold router valve  311 , and through a pulse selector valve  249  of pulse selector manifold  248  to a selected air bladder cell  22 , thus enabling air to be withdrawn from the air bladder cell through the port  43  of the air bladder cell, which is connected to the selector valve during the first, negative going part of a negative pressure pulse produced by air pump  280 . 
         [0161]    Since, as pointed out above, the air pump  280  produces a sequence of pressure pulses at a line frequency rate, e.g., 60 Hz, a negative pressure pulse selected by wave generator controller  244 A to have a length of 1 second, for example, will actually consist of 1 second long pulse modulated at 60 Hz, i.e., a one-second long train of 60 pulses. 
         [0162]    As shown in  FIG. 11A , air flow from a selected air bladder cell  22  and pulse selector valve  249  is routed through selector manifold router valve  311 . Pulse selector manifold router valve  311  has a common outlet port  312  which is connected by a hermetically sealed coupling to input port  246  of pulse selector manifold  248 . Pulse selector manifold router valve has a first, upper outlet port  313  which is connected to upper inlet port  294  of pump inlet router valve  201  by a tubular pressure-tight coupler  314 . Pulse selector manifold router valve  311  also has a second, lower outlet port  315 . 
         [0163]    As shown in  FIGS. 11A and 11B , pulse selector manifold router valve  311  has an internal valve plate  319  which is pivotably moveable by a solenoid actuator  320  in response to an electrical control signal input to an input terminal  321  of the actuator which is connected by an electrical wire to a second valve control output port  322  of wave generator controller  244 A. 
         [0164]    As shown in  FIGS. 11A and 11B , valve plate  319  has a first pivotable position in which the valve plate is pivoted clockwise to block air flow between lower output pulse selector manifold port  246  and lower port  315  of pulse selector manifold router valve  311 . As shown in  FIG. 11A , with valve plate  319  in this position, there is an unobstructed air flow path between manifold output port  246 , through valve  311  to input port  294  of pump inlet valve  291 , and thence into inlet port  281  of pump  280 , 
         [0165]    Referring to  FIG. 11A , it may be seen that pulse routing assembly  290  of wave generator  244  includes a third, pump outlet router valve  331  which has an inlet port  332  that is connected to outlet port  282  of pump  280  by a tubular pressure-tight tube  333 . Pump outlet router valve  331  has a first, upper outlet port  334  which is connected by a tubular pressure-tight tube  335  to the lower inlet port  315  of pulse selector manifold router valve  311 . Pump outlet router valve  331  also has a second, lower exhaust outlet port  336 . 
         [0166]    As shown in  FIGS. 11A and 11B , pump outlet router valve  331  has an internal valve plate  339  which is pivotably moveable by a solenoid actuator  340  in response to an electrical control signal input to an input terminal  341  of the actuator, which is connected by an electrical wire to a third valve controller output port  342  of wave generator controller  244 A. 
         [0167]    As also shown in  FIGS. 11A and 11B , valve plate  339  has a first pivotable position in which the valve plate is pivoted clockwise to block air flow between outlet port  282  of pump  280  and lower input port  315  of pulse selector manifold router valve  311 . In this position, there is an unobstructed air flow path between pump outlet port  282  and lower outlet port  336  of pump outlet router valve  331 . 
         [0168]    As indicated by the arrow-headed lines in  FIG. 11A , with the three router valves  291 ,  311  and  331  configured as shown in  FIG. 11A  and described above, operation of pump  280  causes air to be withdrawn from a selected air bladder cell  22  into pump inlet  281  and discharged from pump outlet port  282  through output port  336  of pump outlet router valve  331 . 
         [0169]    Outlet port  336  of pump outlet router valve  331  may optionally open directly to the atmosphere. Preferably, however, as shown in  FIGS. 11A and 11B , outlet port  336  is connected to a first port  341  of a three-way tubular Y-junction or T-junction coupler  340 . A second port  342  of coupler  340  is coupled through a tube  344  to lower input port  298  of pump inlet router valve  291 . A third port of coupler  340  is coupled through a tube  345  to the inlet port  246  of a pneumatic accumulator or receiver  347 . Thus, as shown in  FIG. 11A , during the initial, negative-going half of a negative air pressure pulse applied to an air bladder cell  22  to withdraw air and reduce the inflation pressure of the cell, withdrawn air is routed into accumulator  347 . Optionally, accumulator  347  may consist of one or more separate air bladder cells which are similar in construction to the individual air bladder cells  22  of air mattress  20 . The additional air bladder cells which are used as an accumulator may be located remotely from the air mattress or optionally at either or both the foot end and head end of the mattress. 
         [0170]      FIG. 11B  illustrates valve configuration and resulting air flow paths directed by wave generator controller  244 A during the second half of a negative pressure pulse, in which a volume of air is re-introduced into an air bladder cell  22  to thus partially or fully re-inflate the cell to a new or original quiescent value of pressure, respectively. 
         [0171]    As may be understood by referring to  FIG. 11B , a positive-going part of a pressure pulse applied to an air bladder cell  22  is created by directing air flow from outlet port  282  of pump  280  to inlet port  246  of pulse selector manifold  248 , and thence through a selected valve  249  to a selected air bladder cell  22 . Thus, as shown in  FIG. 11B , valve plate  339  of pump outlet router valve  331  receives a signal from wave generator controller  244 A to pivot to a position which allows air flow from pump outlet port  282  and through upper outlet port  334  of valve  331 , and thence through inlet port  315  of pulse selector manifold router valve  311 , through the port  312  of the manifold router valve, and finally through a selector valve  249  to a selected air bladder cell  22 . 
         [0172]    As shown in  FIG. 11B , during the positive-going part of an air pressure pulse to be delivered to an air bladder cell  22 , valve plate  319  of pulse selector manifold router valve  311  is positioned by a command signal from wave generator  244 A to block air flow through port  313  of valve  311 . As is also shown in  FIG. 11B , during the positive-going part of an air pressure pulse, valve plate  299  of pump inlet routing valve  291  is positioned by a command signal from wave generator  244 A to block air flow through port  294  of valve  291 . In this position, there is created an unobstructed air flow path for air which was pressurized in accumulator  347  during the negative-going part of an air pressure pulse, through pump inlet router valve  291  and thence into inlet port  281  of pump  280 . 
         [0173]    Referring to  FIGS. 11A and 11B , it may be seen that wave generator  244  preferably includes a pressure transducer  348  which communicates with inlet port  246  of pulse selector manifold  248 . With valve plate  319  of selector manifold router valve  311  in a clockwise, closed position as shown in  FIG. 11A , and valve plate  249  of pump inlet router valve  299  in a clockwise, closed position as shown in  FIG. 11B , opening a selector valve  249  connected to the port  243  of a selected air bladder call  222  results in equalization of pressure between the interior volume of the selected air bladder cell and the much smaller volume of a space located between the valve plate  249  and the input port  246  of the pulse selector manifold. Probe  349  of pressure transducer  348  communicates with this space and thus produces at an output terminal  350  of the transducer an electrical signal which is proportional to air pressure within a selected air bladder cell  222 , which signal is conducted by an electrical wire  351  to wave generator controller  244 A. 
         [0174]    Listed below is a typical sequence of operations of wave generator  244  and configurations of router valves  291 ,  311  and  331  during the various steps of pulse generator  245  in response to electrical control signals issued by wave generator controller  244 A to effect pre-programmed sequences of pressure pulse generation which result in soliton traveling support force waves on the surface of air mattress  20 . Table 2 following the operational sequence summary lists the configurations of router valves  291 ,  311  and  331  during the various steps of a pulse generation sequence. 
       Wave Generator Operation Sequence 
       [0000]    
       
         1. Initialize System. 
         2. Receive command to begin wave. 
         3. Open selector valve  249  to select a first air bladder cell  22 . 
         4. Measure pressure in selected cell via pressure transducer  348  connected to inlet port  246  of selector manifold  248 . 
         5. Input pressure measurement value to wave generator controller  244 A. 
         6. Open pump inlet router valve  291 . 
         7. Turn vacuum/pressure pump  280  on to withdraw air from selected cell. 
         8. Leave pump  280  on until negative pressure-peak measured by transducer  348  and input to controller  244 A is achieved. 
         9. Close pump inlet router valve  291 . 
         10. Shut pump  280  off. 
         11. Allow time period equal to desired negative peak pressure dwell time period to elapse. 
         12. Open pump outlet router valve  331 . 
         13A. Turn pump on to input air into selected cell  22 . 
         13B. Open selector manifold router valve  311  to input air into selected cell  22 . 
         14. Leave pump on until pressure measured by transducer  348  increases to original or new desired bias level. 
         15A. Close selector manifold router valve  311 . 
         15B. Close pump outlet router valve  331 . 
         16. Shut pump off.
 
Repeat steps 3-16 for additional selected air bladder cells in a sequence required for a desired wave cycle.
 
         17. Repeat steps 1-16 for each additional wave cycle commanded by wave generator controller  244 A. 
       
     
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 VALVE 2, 
                 VALVE 3, 
               
               
                   
                   
                 VALVE 1, 
                 SELECTOR  
                 PUMP  
               
               
                   
                 SEQUENCE 
                 PUMP INLET 
                 MANIFOLD  
                 OUTLET 
               
               
                   
                 STEPS 
                 (291) 
                 (311) 
                 (331) 
               
               
                   
                   
               
             
             
               
                   
                 1-5 
                 Clockwise (CW), 
                 CW, Closed 
                 CW, Closed 
               
               
                   
                   
                 Closed 
                   
                   
               
               
                   
                 6-8 
                 Counterclockwise 
                 CW, Closed 
                 CW, Closed 
               
               
                   
                   
                 (CCW) 
                   
                   
               
               
                   
                   
                 Open 
                   
                   
               
               
                   
                  9-11 
                 CW, Closed 
                 CW, Closed 
                 CW, Closed 
               
               
                   
                 12-14 
                 CCW, Closed 
                 CCW, Open 
                 CCW, Open 
               
               
                   
                 15-16 
                 CW, Closed 
                 CW, Closed 
                 CW, Closed 
               
               
                   
                   
               
             
          
         
       
     
         [0194]      FIGS. 12-24  illustrate the construction of a third embodiment of a soliton traveling wave air mattress apparatus  400  according to the present invention. As will be explained in detail, soliton traveling wave air mattress  400  has a modular construction which facilitates manufacture and use of a range of traveling wave air mattress apparatuses having different degrees of complexity, cost, and features suitable for use both in preventing the formation of bedsores, and for relaxation purposes. 
         [0195]    Referring to  FIG. 12 , modular soliton traveling wave air mattress apparatus  400  may be seen to include a wave generator module  401  and an air mattress module  402 . The air mattress module  402  includes an air mattress  403  comprised of an array of generally semi-cylindrically shaped, individually inflatable air bladder cells  404 , which are made of air impervious material such as thin vinyl plastic sheeting. An example embodiment of mattress  403 , which was found suitable for both health care and relaxational applications, consists of 20 laterally disposed tubes that were arranged in a side-by-side array, each of the tubes having a diameter of about 4 inches and a length of about 34 inches. Thus the mattress  403  had a length of about 80 inches and a width of about 34 inches, which is of a suitable size for placement on supporting surfaces such as a standard size bed mattress or a portable air mattress. 
         [0196]    As shown in  FIG. 12 , air mattress module  402  includes an air mattress interface module  405 . Air mattress interface module  405  has on an outlet side  406  thereof a row of twenty individual outlet ports  407 - 1  through  407 - 20  for pressurized air, which are connected through flexible tubes  408 - 1  through  408 - 20  to inlet ports  409 - 1  through  409 - 20  of air bladder cells  404 - 1  through  404 - 20 . 
         [0197]    As is also shown in  FIG. 12 , wave generator module  401  includes a wave sequence generator  410  which is connected through an elongated flexible 15-conductor cable  411  to  15  individual electrical port terminals  412  of an electrical interface port side  413  of air mattress interface module  405 . 
         [0198]    Referring still to  FIG. 12 , it may be seen that wave generator module  401  includes an air pressure pulse generator  414  which has an outlet port  415 . Air pressure outlet port  415  is connected through a single flexible air tube  416  to an inlet port  417  located on a side  418  of air mattress interface module  403 . 
         [0199]    As shown in  FIG. 12 , wave generator module  401  includes a control electronics module  419  which is connected to wave sequence generator module  410  and air pressure pulse generator  414 . Wave generator module  401  also includes a power supply  420  for converting 115-volt A.C. power input to the wave generator module  401  on a power cord  422  terminating in a power plug  421  plugged into a mains power source, into 12-volt D.C. power for operating control electronics module  419 , pressure pulse generator  414  and wave sequence generator  410 . 
         [0200]    In a preferred embodiment of soliton traveling wave apparatus  400 , wave generator module  410  may be located some distance from a bed, portable mattress, or other support on which air mattress  403  is placed, and connected to air mattress module  402  by single flexible cable  411  which contains insulated conductors operating at an electrical potential of no more than 12 volts D.C., and by a parallel flexible air tube  416 . Desirably, air mattress interface module  405  may be positioned near the foot-end of air mattress  403 , and connected to air bladder cells  404 - 1  through  404 - 20  of the air mattress by relatively short, flexible electrically insulating air tubes  408 - 1  through  408 - 20 . 
         [0201]      FIG. 13  illustrates in more detail the construction of wave generator module  401  of soliton traveling wave air apparatus  400 . 
         [0202]    As shown in  FIG. 13 , wave sequence generator  410  of wave generator module  401  has 10 electrical output terminals  423 - 1  through  423 - 10  and a common ground terminal  424 . Wave sequence generator  410  contains electronic circuitry which is powered by 12-volt D.C. power supplied to +12-volt and ground terminals  425 ,  426 , respectively, of the wave generator module from +12-volt and ground output terminals  427 ,  428  of D.C. power supply  420 . Wave sequence generator  410  emits sequentially on output terminals  423 - 1  through  423 - 10  thereof 12-volt square-wave like air bladder cell selector pulses  429 - 1  through  429 - 10 , as shown in  FIGS. 18 and 19 . As shown in  FIG. 13 , wave sequence generator  410  has an input control port  430  which is connected to an output control port  431  of control electronics module  419 . Control electronics module  419  has Mode and Frequency control input ports  432 ,  433  which may be connected to manually operable switches, or to a data port such as an RS 232 port or a USB port. 
         [0203]    In response to Mode and Frequency select control signals input to control electronics module  419  on input terminals  432  and  433  thereof, the frequency and sequencing pattern of bladder selector pulses  429  emitted on terminals  423 - 1  through  423 - 10  of the wave sequence generator  410  can be varied by a user of apparatus  400 . Thus, for example, a first, basic operating mode of apparatus  400  may consist of a first “downward” (head-to-foot) sequence of bladder selector pulses  429 - 1  through  429 - 10  emitted sequentially on terminals  423 - 1  through  423 - 10  of wave sequence generator  410 , as shown in line  1  of  FIG. 18 . 
         [0204]    As indicated by the numbers in parentheses in line  1  of  FIG. 18 , a second operating mode of wave sequence generator  410  may be selected which causes a second, “upward” sequence of bladder selector pulses  429  to be emitted sequentially in terminals  423 - 10  through  423 - 1  of wave sequence generator  410 . As will be described in detail below, wave sequence generator  410  desirably is controllable to output other sequential patterns of pulses  429 . 
         [0205]    According to the invention, wave sequence generator  410  is also controllable in response to signals input to frequency control port  433  of control electronics module  419  and conveyed to wave generator control port  430  to vary the repetition rate frequency of bladder selector pulses  429  emitted by the wave sequence generator. As will be explained in detail, a typical range of periods of bladder selector pulses  429 - 1  through  429 - 10  on the ten output terminals  423 - 1  through  423 - 10  of wave sequence generator  410  of apparatus  400  would be from about one to two seconds to about 1 to 10 minutes. Thus, the total time period for emitting a sequence of 10 equal length pulses  429 - 1  through  429 - 10  on terminals  423 - 1  through  423 - 10  of wave sequence generator  410  may vary over a typical range of about 10 to 20 seconds to 20 to 100 minutes. 
         [0206]    From the foregoing description of functions of wave sequence generator  410  and control electronics module  419 , those skilled in the art will recognize that those functions may be readily implemented by a suitably programmed microprocessor, micro controller, programmable logic controller (PLC) or similar programmable electronic controller device. In an example embodiment of the present invention which was tested, wave sequence generator  410  included a PIC model 16C58B Programmable Interrupt Controller, the ten output ports of which were connected to input terminals of ten transistor driver switches. As will be described in detail below, bladder selector pulses  429  on output terminals  423 - 1  through  423 - 10  of wave sequence generator  410  are used to actuate individual solenoid valves to an ON configuration for time periods based on the duration of the bladder selector pulses. Thus those skilled in the art will recognize that the current and voltage drive characteristics of wave sequence generator  410  are dependent on the number and electrical characteristics of the solenoid valves used in apparatus  400 . The example embodiment of the invention tested used 12-volt solenoid valves having a coil resistance of about 120 ohms. 
         [0207]    As shown in  FIG. 13 , output terminals  423 - 1  through  423 - 10  of wave sequence generator  410  are also connected to input ports  435 - 1  through  435 - 10  of control electronics module  419 . Control electronics module  419  includes electronic circuitry for processing bladder selector pulses  429  emitted from wave sequence generator  410  and input to input terminals  435 - 1  through  435 - 10  of the control electronics module, and for emitting valve control signals V 1 -V 7  on output terminals  436 - 1  through  436 - 7 , and solenoid valve drive signals SV 1 -SV 7  on output terminals  437 - 1  through  437 - 7 . As shown in  FIG. 13 , control electronics module  419  has a Deflation Pulse Width-adjust input port  438 , and an Inflation Pulse Width-adjust input port  439 . As is also shown in  FIG. 13 , control electronics module  419  may optionally have a pressure transducer signal input port  440 , a rapid-deflate command input port  441 , and a rapid-inflate command input port  442 . 
         [0208]    As may be understood by referring to  FIGS. 13 and 18 , control electronics module  419  produces on output ports thereof electrical control signals, in response to command and status signals input to various input ports of the module. As will be clear from the ensuing discussion of other functions of control electronics module  419 , the circuitry of that module may be implemented as a micro controller, microprocessor, or PLC. An embodiment of control electronics module  419  which was constructed to test various embodiments of a traveling wave air mattress apparatus  400  according to the present invention employed a combination of separate integrated circuit modules, relays, and semiconductor logic and driver components. 
         [0209]    Referring to  FIG. 13 , it may be seen that air pressure pulse generator module  414  of soliton traveling wave air mattress apparatus  400  according to the present invention includes a pressure/vacuum pump  444 , which has a vacuum inlet port  445 , and a pressure outlet port  446 . Vacuum inlet port  445  and pressure outlet port  446  are connected through an arrangement of valves V 1 -V 7  and coupling tubes to pressure/vacuum outlet port  415  of air pressure generator module  414  of wave generator module  401 , which is in turn connected through air inlet tube  416  to manifold inlet port  417  of air mattress interface module  405 , as shown in  FIG. 12 . 
         [0210]    As shown in  FIG. 13 , valves V 1 -V 7  of air pressure pulse generator  414  of wave generator module  401  may be identical, normally OFF (NO), two-way solenoid actuated air valves. Thus, for example, valve V 1 , reference description number  477 - 1  in  FIG. 13 , has a solenoid activator SV 1  ( 448 ) which has a ground return terminal  449 - 1  and a 12-volt actuation terminal  450 - 1 , which is connected to SV 1  drive terminal  437 - 1  of control electronics module  419 . A 12-volt signal level on solenoid valve drive terminal SV 1  ( 437 - 1 ) of control electronics module  419  actuates valve SV 1  to an ON position, in which air passes freely between first and second opposed ports  451 A,  451 B of the valve. Conversely, when the 12-volt actuating signal is removed from solenoid terminal SV 1 , valve V 1  returns to a closed, OFF position, in which air flow between the ports of the valve is blocked. Table 3 lists the valves V 1 -V 7  shown in  FIG. 13 , and identifies the function of each valve. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 ELEMENT 
                   
               
               
                   
                 VALVE 
                 NUMBER 
                 FUNCTION 
               
               
                   
                   
               
             
             
               
                   
                 V1 
                 447 
                 Manifold vacuum 
               
               
                   
                 V2 
                 453 
                 Manifold pressure 
               
               
                   
                 V3 
                 459 
                 Pump recirculate/bypass 
               
               
                   
                 V4 
                 465 
                 Pump vacuum inlet 
               
               
                   
                 V5 
                 471 
                 Pump exhaust to atmosphere 
               
               
                   
                 V6 
                 477 
                 Vacuum inlet from/exhaust to atmosphere 
               
               
                   
                 V7 
                 483 
                 Pressure regulator bypass 
               
               
                   
                   
               
             
          
         
       
     
         [0211]    As shown in  FIG. 13 , valves V 1 -V 7  (reference designation numbers  477 - 1 ,  453 ,  459 ,  465 ,  471 ,  477 ,  483 ) are interconnected through an arrangement of Tee-couplers and tubes between pressure/vacuum pump  444  and pressure/vacuum outlet port  415  of air pressure pulse generator  414 . The Tee-couplers include five couplers  489 ,  490 ,  491 ,  492 ,  493 . When an optional pressure transducer  494  is included in apparatus  400 , it is connected to pressure/vacuum outlet port  415  of wave generator module  401  through a sixth Tee-coupler  495 . 
         [0212]    Air pressure pulse generator  414  of wave generator module  401  is used to introduce pulses of air into individually selectable air bladder cells  404  of air mattress  403  (see  FIG. 12 ) in a manner which is described in detail below. The construction and functions of apparatus  400  which enable transmission of air pressure pulses to selected air bladder cells  404  may be best understood by referring to  FIG. 14  in addition to  FIGS. 12, 13, and 18 . 
         [0213]    As shown in  FIG. 14 , air mattress interface module  405  includes a distributor manifold  496  what has an inlet port  417  for pressurized air which is connected through a single flexible air tube  416  to air pressure pulse generator  414  of wave generator module  401 , as shown in  FIG. 12  and previously described. Distributor manifold  496  has a series, e.g., ten, of air outlet ports  497 - 1  through  497 - 10 . Each air outlet port  497  is connected through a flexible air tube to a first port  498  of a solenoid air bladder cell valve  499 . Each solenoid air bladder cell valve  499  is a normally OFF valve that permits passage of air between first port  498  and a second port  500  thereof, only when solenoid actuator  501  of the valve is actuated by a 12-volt signal impressed on input terminal  502 , and return terminal  503  of the solenoid is connected to a ground return through ground return conductor RTN 1  ( 504 ). 
         [0214]    As may be understood by referring to  FIGS. 12 and 13  in addition to  FIG. 14 , each solenoid drive terminal  502 - 1  through  502 - 10  of the solenoid valves  499 - 1  through  499 - 10  is connected through a separate insulated conductor  505 - 1  through  505 - 10  of interface cable  411  to a separate output terminal  423 - 1  through  423 - 10  of wave sequence generator module  410 . Also, common ground conductor line  504  of air mattress interface module  405  is connected through a separate conductor of cable  411  to ground return output terminal  424  of wave sequence generator  410 . 
         [0215]    From the foregoing description, it will be understood that when a 12-volt D.C. actuating signal is emitted from an output terminal, e.g.,  423 - 1  of wave sequence generator  410 , a corresponding air bladder cell valve, e.g.,  499 - 1  of air mattress interface module  405 , will be actuated to an ON configuration. In this ON configuration, there is pneumatic communication between second port  500  of the valve  499  and pressure/vacuum outlet port  415  of air pressure pulse generator  414  of wave generator module  401 . Thus, as shown in  FIG. 14 , air pressure pulses in pressure/vacuum outlet port  415  of air pressure pulse generator  414  are conducted to outlet port  501 - 1  of valve  499 - 1 , which may be connected to inlet port  409  of an individual air bladder cell  404 . 
         [0216]    Optionally, as shown in  FIG. 14 , the second port of an air bladder cell inflation valve  499  may be coupled to a pair of air bladder cells through a Tee-coupler  506 . Thus, as shown in  FIG. 14 , a first Tee-coupler  506 - 1  enables air pulses to be conveyed simultaneously to a pair of adjacent air bladder cells  404 - 1 ,  404 - 2 . With this arrangement, a 10-outlet port distributor manifold  490  and ten air bladder cell inflation valves  499  may be used to convey air pressure pulses to all 20 of the air bladder cells of a 20-cell air mattress. 
         [0217]    As may be understood by referring to  FIGS. 12, 13, and 14 , in response to electrical control signals input to air pressure pulse generator  414  from wave sequence generator  410  and control electronics module  419 , the air pressure pulse generator produces in pressure/vacuum outlet port  415  air pulses which are conveyed through air mattress interface module  405  to selected air bladder cells  404 - 1  through  404 - 20 . As shown in  FIG. 20 , each air pulse  510  consists of a negative differential pressure component beginning at time T 1  and ending at time T 2  of the pulse. The negative differential pressure component T 1 -T 2  here refers to a reduction of pressure at the inlet port  409  of an air bladder cell  404  that causes the air bladder cell to partially or fully deflate. 
         [0218]    In a first, active deflation mode of operation of pressure pulse generator  414 , pressure reduction component T 1 -T 2  of air pulse  510  is produced by actuating valves of apparatus  400  in a manner which connects the inlet port  409  of an air bladder cell  404  through valves and tubes to the vacuum or suction inlet port  445  of pressure/vacuum pump  444 . In a second, passive deflation mode of operation of air pressure pulse generator  414 , the deflation component T 1 -T 2  of air pulse  510  is produced by actuating valves of the apparatus  400  in a manner which creates a path for air under pressure in an air bladder to be exhausted to the atmosphere. 
         [0219]    As shown in  FIG. 20 , air pressure pulse  510  includes a second, re-inflation component during the time interval T 2 -T 3 . The re-inflation component T 2 -T 3  is produced by actuating valves of apparatus  400  in a manner which creates a pathway for pressurized air discharged from pressure outlet port  446  of pressure/vacuum pump  444  to the inlet port  409  of an air bladder cell  404 . 
         [0220]    Details of the operation of air pressure pulse generator  414  which are effective in producing a sequence of air-pressure pulses  510  of the type shown in  FIG. 20 , and conveying the pulses to an air mattress  403 , of the type shown in  FIG. 14  may be best understood by referring to  FIGS. 13 and 18 . 
         [0221]    As may be understood by referring to  FIGS. 13 and 18 , control electronics  419  contains circuitry which produces a sequence of control signals SV 1 -SV 7  for valves V 1 -V 7  upon receiving a bladder selector pulse  429  from any one of the ten output ports  423 - 1  through  423 - 10  of wave sequence generator  410 , which ports are connected to input ports  435 - 1  through  435 - 10  of control electronics module  419 . For example, as shown in  FIG. 18 , control electronics module  419  produces in response to the leading, positive-going edge of a first bladder selector pulse  429 - 1  on output in terminal  423 - 1  of wave sequence generator  410  the leading edge of a positive-going, Deflate pulse P 1 . As shown in  FIG. 18 , the duration (t 12 -t 11 ) of Deflate pulse P 1  is adjustable as indicated by the variable time location of the trailing edge of the pulse at t 12 . The duration of Deflate pulse P 1  may be adjusted by a signal on input control terminal  432  of control electronics module, for example, by varying the time constant of a monostable multivibrator, or ONE SHOT, triggered by the leading edge of a bladder selector pulse  429 - 1  at time t 11 . 
         [0222]    As shown in  FIGS. 13 and 18 , pulse V 1  is output on solenoid valve drive terminal SV 1  ( 437 - 1 ) to thus turn valve V 1  ON. As shown in  FIG. 18 , valve V 4  is also ON at the same time as valve V 1 , thus providing an air path between vacuum inlet port  445  of pump  444 , pressure/vacuum outlet port  415  of air pressure pulse generator  414 , pressure/vacuum inlet port  417  of the distributor manifold, air bladder cell valve  493 - 1 , and selected air bladder cell  404 - 1 . At the same time valve actuator drive signal SV 5  is also positive, thus enabling pressurized air discharged from pressure outlet port  446  of pressure/vacuum port to pass through pressure regulator  512  and exhausted into the atmosphere. 
         [0223]    Referring still to  FIGS. 13, 18, and 20 , it may be seen that the negative-going, trailing edge of Deflate pulse P 1  triggers the leading edge of an Inflate pulse P 2 . As shown in  FIG. 18 , the time location of the trailing edge of inflate pulse P 2  is also adjustable to thus adjust the duration of deflate pulse P 2 . As will be readily understood by those skilled in the art, P 2  may be generated by a second one-shot triggered by the trailing edge of deflate pulse P 1 . 
         [0224]    Referring to  FIG. 13 , it may be seen that when manifold vacuum valve V 1  is turned OFF at the end of Deflate pulse P 1 , manifold pressure valve V 2  is turned ON, thus providing an air path from pressure outlet port  446  of pressure/vacuum pump  444  to an air bladder cell, such as a selected air bladder cell  404 - 1 . As may also be understood by referring to  FIGS. 13 and 18 , during Inflate pulse P 2 , pump vacuum inlet valve V 4  and vacuum atmosphere vent valve V 6  are ON, providing inlet air to vacuum inlet port  445  of pressure/vacuum pump  444 . 
         [0225]    Optionally, an accumulator of the type shown as element  347  in  FIG. 11B  may be used in a hermetically sealed modification of air pulse generator  414  shown in  FIG. 13 . In this modification, the exhaust port outlet of pump exhaust vent valve V 5  ( 471 ) would be connected through an optional check valve to a first port of an accumulator, and the inlet/exhaust port of vacuum inlet valve V 6  ( 477 ) would be connected to a second port of the accumulator. 
         [0226]    Referring to  FIG. 18 , it may be seen that after the last pulse in a sequence of bladder selector wave pulses  429  has been emitted from wave sequence generator  410 , e.g., after a sequence of 10 or 20 pulses, apparatus  400  may selectably continue to cyclically output sequences of control pulse signals, or enter into a rest mode. As indicated by the solid lines at the right-hand side of  FIG. 18 , during a rest period of apparatus  400 , pump recirculate/bypass valve V 3  ( 459 ) may be turned on. Alternatively, as shown in dashed lines, a resting mode may be selected in which valves, V 4 ( 465 ), V 5  ( 471 ) and V 6 ( 477 ) are turned on to provide venting to the atmosphere of both vacuum inlet port  445  and pressure outlet port  446  of pressure/vacuum pump  444 . Using either of the foregoing rest modes eliminates the necessity for switching pressure/vacuum pump  444  on and off during operation of apparatus  400 .  FIG. 19  illustrates a second, passive deflation mode of operation of apparatus  400 . 
         [0227]    In the passive deflation mode, V 4  is closed and valves V 1  and V 6  are opened during the deflation component of an air pressure pulse, allowing pressurized air from an air bladder cell  404  to escape to the atmosphere through an open port of valve V 6 , rather than being connected to vacuum inlet port  445  of pressure/vacuum pump  444 . As will be explained below, the slower deflation rate of an air bladder cell in a passive deflation mode facilitates a novel and advantageous mode of operation of apparatus  400 . 
         [0228]    Table 4 summarizes the configuration of valves V 1 -V 6  for the above-described operational modes of wave generator module  401 . 
         [0000]    
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                   
                 REST 
                   
               
               
                   
                   
                   
                   
                 (RECIRCU- 
                 REST 
               
               
                   
                 ACTIVE 
                 PASSIVE 
                   
                 LATING 
                 (VENTING  
               
               
                   
                 DEFLATE 
                 DEFLATE 
                 INFLATE 
                 PUMP) 
                 PUMP) 
               
               
                 VALVE 
                 STATE 
                 STATE 
                 STATE 
                 STATE 
                 STATE 
               
               
                   
               
             
             
               
                 V1 
                 ON 
                 ON 
                 OFF 
                 OFF 
                 OFF 
               
               
                 V2 
                 OFF 
                 OFF 
                 ON 
                 OFF 
                 OFF 
               
               
                 V3 
                 OFF 
                 ON 
                 OFF 
                 ON 
                 OFF 
               
               
                 V4 
                 ON 
                 OFF 
                 ON 
                 OFF 
                 ON 
               
               
                 V5 
                 ON 
                 ON 
                 OFF 
                 OFF 
                 ON 
               
               
                 V6 
                 OFF 
                 ON 
                 ON 
                 ON 
                 ON 
               
               
                   
               
             
          
         
       
     
         [0229]      FIGS. 20, 21A, and 21B  illustrate how soliton traveling wave air mattress apparatus  400  produces soliton traveling waves of body support forces on the surface of air mattress  403 . 
         [0230]    As shown in line  1  of  FIG. 21A , before apparatus  400  is powered on, an air mattress  403  of the type shown in  FIG. 12  having, for example, 20 air bladder cells  404  (only the first 10 are shown) may be in a deflated state. At time T 1 , a first pulse of air  510  (see  FIG. 20 ) is input to first air bladder cell  404 - 1  of the air mattress  403 . 
         [0231]    As shown in  FIG. 20  and has been described above, air pulse  510 - 1  has a first, deflation component beginning at time T 1  and ending at time T 2 . Since all of the air bladder cells  404  of air mattress  404  were presumed to be deflated, there will be no change in the contour of air bladder cell  404  during the period T 1 -T 2 . However, if any air bladder cell were partially deflated, it will be fully deflated by the deflation component of air pulse  510  during the period T 1  to T 2 . 
         [0232]    At time T 2 , the inflation component of air pulse  510 - 1  begins to inflate first air bladder cell  404 - 1 . The inflation component of air pulse  510 - 1  continues until time T 3 . The duration of inflation pulse component T 3 -T 2  of air pulse  510 , and the maximum inflation pressure, which is adjusted by adjusting pressure regulator  511 , are selected to inflate air bladder cell  404 - 1  to a pre-determined steady-state pressure PS, which causes the upper body support surface  512  of the air bladder cell to assume the generally semi-cylindrically shaped contour shown in line  2  of  FIG. 21A   
         [0233]    Referring to lines  3  through  10  of  FIG. 21A , it may be seen that successive air bladder cells  404 - 2  through  404 - 20  are sequentially selected and inflated by wave generator module  401 , resulting in a fully inflated air mattress  403  as shown in the last line of  FIG. 21A . 
         [0234]      FIG. 21B  illustrates how apparatus  400  produces a soliton traveling wave of body support force reduction on the upper surface  512  of air mattress  403 . 
         [0235]    As shown in  FIG. 21B , after a first cycle of 10 or 20 pulses emitted by wave sequence generator  410  to initialize an air mattress  403  to a fully inflated state as shown in the last line of  FIG. 21B , a second and successive cycles of wave sequence pulses are effective in producing a soliton traveling body support force reduction wave on the upper surface  512  of air mattress  403 . Thus, as shown in line  2  of  FIG. 21B , during the deflation period T 1 -T 2  of a first, head-end air bladder cell  404 - 1 , that air bladder cell is deflated to thus reduce the support force exerted by the air bladder cell on a body part. The duration of this deflation component T 1 -T 2  of the air pulse  510  may be adjusted to any suitable value, such as 1 to 5 minutes or longer. 
         [0236]    At time T 2  of a first deflation pulse, air bladder cell  404 - 1  is re-inflated to a pre-determined quiescent pressure, during the time interval T 2  to T 3 . The minimum duration of inflation component T 2  to T 3  of air pulse  510  is typically determined by how long it takes to inflate an individual air bladder cell  404  to a desired pressure, which for a relatively small pressure/vacuum pump having an outlet pressure of 36 PSI and an air flow rate of 5.5 lpm would be about 30 seconds to one minute. 
         [0237]    As shown in lines  3 - 11  of  FIG. 21B , sequentially deflating and re-inflating the remaining air bladder cells  404 - 2  through  404 - 10  or  404 - 20  of a 10 or 20 bladder mattress causes a soliton traveling wave of body support force reduction to progress from one end to the other end of air mattress  403 . For example, if the first air bladder cell  404 - 1  is located at the head-end of a bed, a traveling wave of body support force reduction  513  will be propagated from left to right a shown in  FIG. 21B , i.e., from the head-end to the foot-end of air mattress  403 . 
         [0238]    As may be understood by referring to  FIG. 21B , deflation of each air bladder cell  404  is initiated at the times T 1 ,—T 10  coinciding with the beginning of a sequence of air bladder selector pulses  429 - 1  through  429 - 10 , as shown in  FIG. 18 . At the end of each bladder selector pulse, the selected air bladder cell is left in a fully inflated state. Thus, at the time T 1 , coincident with a first bladder selector pulse  429 - 1 , air bladder cell  404 - 1  becomes deflated, and at the end of pulse  429 - 1 , is fully re-inflated. 
         [0239]    In a basic embodiment of the apparatus  400  according to the present invention shown in  FIGS. 12, 13, and 14 , a wave sequence generator  410  having ten output ports, and a distributor manifold having ten outlet air ports in a simplified, low-cost configuration, are used to control a 20-air bladder cell air mattress. This configuration also utilizes only ten air bladder cell valves  499  to minimize cost and complexity. 
         [0240]    As shown in  FIG. 14 , the ten-port wave sequence generator  410 , ten-port distributor manifold  490 , and ten air bladder cell valves  499  are enabled to control an air mattress  403  which has 20 air bladder cells  404 - 1  through  404 - 20 , by driving a pair of air bladder cells  404  from each distributor outlet port using a single air bladder cell valve  499  connected to each port.  FIG. 21C  illustrates generation of a soliton traveling body support force reduction wave in which adjacent pairs of air bladder cells  404  are sequentially deflated and re-inflated to produce a head-to-foot traveling body force support wave on an air mattress  403  having 20 air bladder cells  404 . 
         [0241]      FIGS. 13, 15, and 21D  illustrate a modification of apparatus  400  which uses a 10-output port wave sequence generator  410 , a 10-outlet port distributor manifold  490 , and 20 air bladder cell valves  499  to individually inflate and deflate 20 air bladder cells. As shown in  FIG. 15 , each of the 10 output ports  497 - 1  through  497 - 10  of ten-output port distributor manifold  490  is coupled through a Tee coupler  515 - 1  through  515 - 10  to a pair of air bladder cell valves  517 A- 517 B to a pair of air bladder cells  404 - 1 ,  404 - 2  through  404 - 19 ,  404 - 20 . Each air bladder cell valve  517 A has a solenoid actuator which has a 12-volt input terminal  519 A and a first ground return input terminal  520 A. Similarly, each second bank air bladder cell valve  517 B has a solenoid actuator which has a 12-volt input terminal  519 B and a second ground return input terminal  520 B. 
         [0242]    As shown in  FIGS. 13 and 15 , the 12-volt solenoid actuator input terminals  519 A,  519 B of each pair of air bladder cell valves  517 A,  517 B are connected to a single output terminal  423  of wave sequence generator  410  through a single insulated conductor  521  of cable  411 . The first ground return terminal  520 A of the solenoid actuator of each air bladder cell valve  517 A is connected to a first common return conductor RTN 1  ( 522 ). Also, the second ground return terminal  520 B of each air bladder cell valve  517 B is connected to a second common return conductor RNT 2  ( 523 ). 
         [0243]    As shown in  FIGS. 13 and 15 , RTN 1  and RTN 2  conductors are deployed from air mattress module  402  to control electronics module  419  of wave generator module  401 . As shown in  FIG. 13 , RTN 1  conductor  522  and RTN 2  conductor  523  are connected to the B and C contacts of a SPDT relay  525 . Relay  525  is driven by a toggle flip-flop FF 2  (not shown) in control electronics module  419 . As may be understood by referring to  FIG. 18 , toggle FF 2  is triggered alternately between SET and RESET states at the end of each 10 inflation pulses P 2 . With this arrangement, it will be understood that when power is first applied to control electronics module  419 , either RTN 1  line or RTN 2  line will be connected to ground through contacts of relay  525 . In this first position of relay  525 , a sequence of 10 pulses  429 - 1  through  429 - 10  will actuate air bladder cells valves  517 A- 1  through  517 - 10 , or  517 B- 1  through  517 B- 10 . After the 10th pulse  429 - 10  is input to control electronics module  419 , flip-flop FF 2  will be toggled to a different state as shown in the last line of  FIG. 18 . With the foregoing arrangement, a sequence of deflating and re-inflating only the 10 odd-number air bladder cells  404  of an air mattress  403  alternating with a sequence of deflating and re-inflating only even-number air bladder cells  404 , results in the generation of alternating odd and even head-to-toe body support force waves, as shown in  FIG. 21D . 
         [0244]      FIG. 16  illustrates another variation of the soliton traveling wave air mattress  400  according to the present invention. This variation employs a router manifold interposed between the distributor manifold and air bladder cells shown in  FIG. 15  and enables creating a non-alternating, consecutive sequence of air bladder cell deflation and re-inflation cycles in an air mattress  403  having 20 air bladder cells  404  using a ten-output port distributor manifold. 
         [0245]      FIG. 17  illustrates another variation of the apparatus  400  which uses a pair of 10 output port distributor manifold  490 A,  490 B, 20 air bladder cell valves, and a ten-output terminal wave sequence generator to produce soliton traveling body support force variation waves on an air mattress  403  having 20 air bladder cells, using the toggle flip-flop FF 2  as described above. 
         [0246]      FIG. 21E  illustrates the formation of a backward, foot-end towards head-end traveling body support force wave which may be generated using the traveling wave apparatus of  FIGS. 12-17 . 
         [0247]      FIG. 21F  illustrates another type of soliton body support force reduction wave which can be produced by the apparatus  400  according to the present invention, in which the operating mode of the wave sequence generator is selected to produce simultaneous up and down soliton traveling waves of pulses  429 . It should be noted that wave sequence generator  410  may be programmed to enable production of a virtually unlimited variety of wave sequences. Also, as shown in  FIG. 13 , control electronics module  419  optionally includes Rapid Inflate and Rapid Deflate input ports, which would be used to command wave generator module  410  to output inflate only or deflate only signals  429  simultaneously on all 10 output ports  423  of the wave generator module, and a command signal turn on pressure regulator bypass valve V 7  ( 483 ). 
         [0248]      FIGS. 22-24  illustrate a modification of traveling wave air mattress  400 . As may be understood by referring to  FIGS. 20 and 22 , the bladder selector pulses  429  output sequentially from wave sequence generator  410  are typically used to generate a pattern of deflation and re-inflation pulses  510  which travel sequentially from each air bladder cell  404  to the next adjacent cell, each pair of air bladder cells to the next adjacent pair, each odd air bladder cell to the next odd air bladder cell, and each even air bladder cell to the next even air bladder cell. However, it should be recognized that it may in some cases be desired to omit certain air bladder cells from the deflation/re-inflation sequence. For example, if certain bladder cells  404  of the air mattress are very lightly loaded, or simply not loaded at all because a short person is lying on the air mattress, it may be desired to skip the lightly loaded or unloaded air bladder cells, affording the possibility of decreasing the times between which loaded air bladder cells are pulsed. 
         [0249]    Therefore, apparatus  400  according to the present invention optionally includes elements which provide a novel and efficient means of monitoring average loading of individual air bladder cells, and utilizing that information to provide command signals to wave sequence generator module  410  to omit inputting air-pulse command signals  429  to air bladder cells  404  which are subjected to average weight load forces below a predetermined threshold value. 
         [0250]    The novel structure and method of periodically sensing minimum weight loads of individual air bladder cells  404 , and responding to the sensing of minimum loading by periodically omitting application of force-reducing deflation/inflation pulses to such cells may be best understood by referring to  FIGS. 13, 18, 19, 22, 23, and 24 . 
         [0251]    As shown in  FIG. 23 , when an air pressure pulse  510  is applied to an air bladder cell  404  that is subjected to a significant weight load of, for example, 5 to 10 pounds, that air bladder cell will deflate relatively rapidly to a pre-determined pressure PT at a time T.L., as indicated by the solid line in  FIG. 23 . 
         [0252]    On the other hand, an unloaded or lightly loaded air bladder cell will take longer until time TU to deflate, as indicated by the dashed line in  FIG. 23 . Consequently, by measuring the air pressure in pressure/vacuum outlet port  415  of air pulse generator by pressure transducer PT ( 485 ) at a time TL after the initiation of the deflation component of air pulse  510 , and determining that it has not yet been reduced below the threshold pressure PT, it can be concluded that there is little or no load on that particular air bladder cell. Accordingly, the wave sequence generator  410  may in this case be commanded by a signal from control electronics module  419  to skip issuing a square wave bladder selector pulse  424  signal to deflate that air bladder cell, during the next sequence of bladder selector pulses  429  emitted by the wave sequence generator. 
         [0253]    The time difference between loaded and unloaded reduction of inflation pressure crossing the PT threshold my be enhanced by utilizing the passive deflation mode described previously. Thus, as shown in  FIGS. 18 and 19 , flip-flop FF 2  may be toggled at the end of each 10 or 20 pulses  429  to thus switch between active and passive deflation modes as desired to thereby increase resolution in determination of the of differences in weight loading of the air bladder cells  404 . 
         [0254]      FIG. 24  illustrates a sequence of air bladder cell deflation/re-inflation pulses  510 , in which pulses to air bladder cells  2 ,  3 ,  5 , and  6  have been omitted because they have been determined in a previous sequence of deflation/inflation pulses to have been subjected to a time-average weight load below a predetermined value which is insufficient to result in those cells deflating to or below a threshold pressure PT on or before time TL. 
         [0255]    Those skilled in the art will recognize that the time sequences of air pressure pulses  63  shown in  FIGS. 3A and 3B , considered collectively, have a characteristic of soliton traveling waves, i.e., each sequence consists of a solitary traveling pressure wave having a constant amplitude. As has been described above, the sequence of air pressure pulses depicted in plots  1 - 6  of  FIG. 3A , when input into a series of air bladder cells, such as the one shown in  FIG. 7A , result in a traveling soliton wave of pressure variation in the air bladder cells, which in turn produces a soliton traveling wave of body support force variation, i.e., reduction, as depicted in  FIG. 21B . 
         [0256]    Another characteristic of a soliton traveling wave is that it maintains its amplitude and shape in spite of collisions with other soliton traveling waves. The lines labeled T 9 -T 2  of  FIG. 21F  illustrates that the soliton traveling waves of body support force in air mattresses according to the present invention also have this characteristic. Thus as shown in lines T 9 -T 2  of  FIG. 21F , a first soliton wave of traveling body support force traveling from left to right, e.g., from the head-end to the foot-end of an air mattress, collides with a second soliton wave of traveling body support force traveling from right to left, e.g., from the foot-end of a mattress towards the head-end, at time T 10 . At time T 1 , the downward and upward soliton pulses traveling waves have passed through each other without change. 
         [0257]      FIG. 25  illustrates a first modification  614  of the air pressure pulse generator component or module shown in  FIG. 13  and described above, which requires only five valves rather than the seven shown in  FIG. 13 . 
         [0258]    In modified air pressure pulse generator module  614 , air bladder cells  404  (see  FIG. 12 ) are initially inflated en masse, as follows. With valves V 1  ( 477 - 1 ), V 3  ( 459 ), and V 5  ( 471 ) in closed, OFF, positions, and valves V 6  ( 477 ) and V 2  ( 453 ) in open, ON positions, pressure/vacuum pump  444  is powered on. This action enables air to be drawn from the atmosphere through valve V 6  ( 477 ), vacuum inlet port  445  of pressure/vacuum pump  444 , expelled from outlet port  446  of the pressure/vacuum pump, and passed through valve V 2  ( 453 ) to air bladder cells  404 , e.g., the twenty air bladder cells  404 - 1  through  404 - 20  shown in  FIG. 12 . After a time period sufficient to inflate all twenty air bladder cells  404 - 1  through  404 - 20  to a desired quiescent air pressure valves V 6  ( 477 ) and V 2  ( 453 ) are actuated to an OFF position, and valve V 3  ( 459 ) is actuated to an ON position, enabling air to be circulated through V 3  and pressure/vacuum pump  444  during a rest interval. During this rest interval, pump  444  may be powered off or remain on. 
         [0259]    Following an initial rest interval after inflation of all air bladder cells  404 - 1  through  404 - 20 , a soliton traveling wave of air pressure and resulting traveling soliton body support force wave in air mattress module  403  may be initiated. A first step in initiating a traveling air pressure pulse wave consists of issuing a manifold selector valve opening signal  429  to a selected air bladder cell selector valve or valves, e.g., valve  499 - 1  connected to air bladder cells  404 - 1  and  401 - 2 , as shown in  FIG. 18 . Next, in response to control signals issued from control electronics module  419 , valve V 3  ( 459 ) is closed, and valves V 1  ( 477 - 1 ) and V 5  ( 471 ) are opened. As may be understood by referring to  FIG. 25 , this valve configuration enables air to be withdrawn from a selected air bladder cell or cells  404  through valve V 1  ( 477 - 1 ), vacuum inlet port  445  of pressure/vacuum pump  444 , through outlet port  446  of the pressure/vacuum pump, and through valve V 5  ( 471 ) to the atmosphere. 
         [0260]    The foregoing valve configuration in the initial, deflation part of an air bladder cell pressure pulse is maintained for a time interval sufficient to reduce air pressure in a selected air bladder cell or cells to a pre-determined value. 
         [0261]    At the end of a deflation period, valves V 1 , V 2 , V 3 , V 5 , and V 6  are actuated to the initial en masse inflation configuration described above. Since pressure/vacuum pump  444  need only have a capacity to fully deflate or re-inflate one or two air bladder cells in a period of, for example, one-half to two minutes, the time period for inflating a single air bladder cell with pressure/vacuum pump operating at full capacity would be about one-twentieth that required to fully inflate a fully-deflated air mattress  403  having twenty air bladder cells. Thus, the time required to re-inflate a single fully-deflated air bladder cell  404  would typically be about one-half to one minute versus ten to twenty minutes to fully inflate all twenty air bladder cells. 
         [0262]    At the end of an initial deflation/re-inflation air pulse cycle as described above, the apparatus may be programmed to enter a rest period of a selectable duration, such as the time interval between T 13  and T 21  shown in lines  1  and  2  of  FIG. 20 . During the rest period, valves V 1 , V 2 , V 3 , V 5 , and V 6  are configured as described above for the initial rest interval. 
         [0263]    After a pre-determined rest period, second and successive air pressure pulses may be applied to second and successive air bladder cells  404 , in the same manner as described above. 
         [0264]    It should be noted that modified pressure pulse generator  614  shown in  FIG. 25  draws in air from the atmosphere through the inlet port of valve V 6  ( 459 ) and exhausts air to the atmosphere through the outlet port of valve V 5  ( 471 ). 
         [0265]      FIG. 26  illustrates another modification of air pressure pulse generator  414  shown in  FIG. 13 , in which air cyclically exhausted from and inlet to air bladder cells is transmitted to and from one or more accumulators rather than to the atmosphere. In this modified, closed system, after an initial supply of air such as filtered air from the atmosphere is input to the apparatus to inflate all air bladder cells  404  and one or more accumulators, the air pressure pulse generator  714  may be isolated from external air inlet sources and exhaust locations. 
         [0266]    As shown in  FIG. 26 , second modified pressure generator module  714  has, in addition to the five valves of first modified pressure pulse generator  614 , two additional valves, V 4  ( 477 - 2 ) and V 7  ( 477 - 3 ). 
         [0267]    As may be understood from the description above of the initial en masse inflation of all air bladder cells of an air mattress, valve V 4  ( 477 - 2 ) may be actuated to an ON position to enable an initial volume of air to be drawn in from the atmosphere or other source to inflate all air bladder cells  404 , in a “rapid inflate” or en masse inflation mode. 
         [0268]    Similarly, it will be understood that valve V 7  ( 477 - 3 ) may be actuated to an ON position to exhaust air from all air bladder cells  404  to the atmosphere in a “rapid deflate” mode. However, cyclical deflation and re-inflation of selected air bladder cells by air pressure pulse generator  714  after all of the air bladder cells  404  of an air mattress have been inflated is performed in isolation from the atmosphere, as will now be described. 
         [0269]    Referring to  FIG. 26 , it may be seen that second modified pressure pulse generator  714  has in the lower, vacuum inlet arm thereof a valve V 4  ( 465 ) used to provide air from an external source such as the atmosphere to initially inflate all of the air bladder cells  404  of an air mattress  403 . As shown in  FIG. 26 , air pressure pulse generator  714  has in addition to external air inlet control valve V 4  ( 465 ), an additional air inlet valve V 6  ( 478 ). 
         [0270]    Air inlet valve V 6  ( 478 ) has an inlet port connected to a sealed interior space of a first accumulator, Accumulator  1 . According to the invention, Accumulator  1  may consist of one and preferably two additional air bladder cells  404 - 21 ,  404 - 22 , as may be understood by referring to  FIG. 27 . When two air bladder cells are used, they are connected in parallel by a tee-coupler. The foregoing air bladder cells may be positioned at the foot end of air mattress  403 . Optionally, since the length of air mattress  403  would typically be greater than that required for a patient, the two foot-end air bladder cells  404 - 19  and  404 - 20  could be used as Accumulator  1  air bladder cells. 
         [0271]    Referring still to  FIG. 26 , it may be seen that second modified air pressure pulse generator  714  has in the upper, pressure output arm thereof a valve V 7  ( 483 ) which is used to exhaust air withdrawn from all air bladder cells  404  of an air mattress  403  to the atmosphere, in a rapid deflation mode. 
         [0272]    As shown in  FIG. 26 , air pressure pulse generator  714  has in addition to external air exhaust valve V 7  ( 483 ), and additional air outlet valve V 5  ( 498 ). Air outlet valve V 5  ( 498 ) has an outlet port connected to the sealed interior space of a second accumulator, Accumulator  2 . According to the invention, Accumulator  2  may consist of one and preferably two air bladder cells  404  connected in parallel by a tee-coupler as has been described above for Accumulator  1 . 
         [0273]      FIG. 27  illustrates a third embodiment  814  of an air pressure pulse generator according to the present invention. As shown in  FIG. 27 , air pressure pulse generator  814  includes an accumulator interconnect Tee  499  which has a first port thereof connected to the outlet port of outlet valve V 5  ( 498 ), a second port connected to the inlet port of inlet valve V 6  ( 478 ), and a third, accumulator port. The third, accumulator port is connected to a single accumulator of the type described above, which consists of one and preferably two air bladder cells  404 - 21 ,  404 - 22  connected in parallel and located at the foot end of air mattress  403 , or in a separate location such as below a support surface for air mattress  403 . 
         [0274]    The novel configuration of air pressure pulse generator modules  714 ,  814  shown in  FIGS. 26 and 27  facilitates a novel Body Support Force Equalization Mode of operation of the air mattress inflation control apparatus shown in those figures, as will now be described. 
         [0275]    Referring to  FIG. 27 , after all air bladder cells  404  have been inflated to configure air mattress  403  for use, and after a person has lain down on the air mattress, a Body Support Force Equalization Mode may be entered before initiation of cyclical generation of soliton traveling air pressure waves as described above. The purpose of the Body Support Force Equalization Mode is to decrease large body support force concentration and imbalances to distribute body support force more equally. In other words, the result of utilizing the Body Support Force Equalization Mode according to the present invention is to adjust the air pressure in individual air bladder cells  404  to average bias levels which are more nearly equal to one another, before superimposing a soliton traveling force reducing pressure wave in a sequence of air bladder cells  404 . 
         [0276]    In the Body Support Force Equalization Mode according to the present invention, all air bladder cells  404  of an air mattress  403  are first inflated en masse to a pre-determined pressure level. 
         [0277]    Next, pressure/vacuum pump  444  is preferably turned off, and pump bypass valve V 3  ( 459 ) is turned on. Valves V 1  ( 477 - 1 ), V 2  ( 453 ), V 5  and V 6  ( 477 ) are also actuated to ON positions at this time. 
         [0278]    Next, sequence generator  410  receives a signal to output a sequence of selector valve control signals  429 - 1  through  429 - 10  or  429 - 20  to manifold selector valves  499 . 
         [0279]    When each individual manifold selector valve  499  is actuated to an ON position, air in a selected air bladder cell  404  that is pressurized above the pressure in control accumulators  1  and  2 , air flows into the accumulators, thus reducing body support force on a particular air bladder cell that is heavily loaded, as by a body protuberance. 
         [0280]    Conversely, if the air pressure in a selected air bladder cell is less than that in control accumulators  1  and  2 , air flows from the accumulators to that air bladder cell. This results in re-distribution of body support forces to more nearly equal values as the manifold valves are actuated sequentially to ON positions. 
         [0281]    After one or more repetitions of the manifold selector valve actuating sequence described above, cyclical traveling pressure waves are initiated by control electronics module  419 . In a preferred mode of operation, these pressure waves would have a smaller amplitude than that used without prior equalization of the different bias pressure levels in the air bladder cells by utilization of the Body Support Force Equalization Mode. The amplitude of the traveling pressure waves imposed on quiescent bias pressures in the air bladder cells is conveniently reduced by decreasing the duration of both deflation and re-inflation periods of a traveling air pressure pulse wave. Thus the traveling pressure wave may be speeded up without requiring an increase in the volumetric flow rate of pressure/vacuum pump  444 . 
         [0282]    The Body Support Force Equalization Mode described above may be initiated periodically, e.g., hourly, or optionally in response to sensed body weight redistributions above a pre-determined threshold value, which may be measured by an optional pressure or force sensor. 
         [0283]      FIG. 28  illustrates a modification of a basic embodiment of an air mattress according to the present invention shown in  2 A. Modified air mattress  503  shown in  FIG. 28  includes oval plan-view, annular ring-shaped parallel tubular air bladder cells  50  which are arranged in a concentric array. Each of air bladder cells  504  has an air inlet port  509  which protrudes downwardly from a lower surface of the air bladder cell. In this arrangement, air bladder cells  504 - 1  through  504 - 10  may receive sequential pulses of air pressure variation to thus produce an the upper surfaces of the air bladder cells a soliton traveling wave of body support force variation. This soliton traveling wave has an elliptical ring-shaped wave front that travels radially outwardly from the center of mattress  503  to the outer perimeter of the air mattress, which is coincident with the outer perimeter of outermost air bladder cell  504 - 10  when air pressure pulses are introduced to air bladder cells  504 - 1  through  504 - 10  in ascending order, and radially inwardly when the pulses are introduced into its air bladder cells in reverse order, i.e.,  504 - 10  through  504 - 1 . 
         [0284]      FIG. 29  illustrates a modification  523  of air mattress  503  shown in  FIG. 28 , in which oval ring-shaped air bladder cells  524  are segmented into four contiguous quadrant arc-shaped segments,  524 -A,  524 -B,  524 -C, and  524 -D. In this embodiment, soliton traveling waves of body support force may be caused to travel in circumferential directions on the surfaces of the air bladder cells, as well as in radial directions as have been described above for the air mattress  503  shown in  FIG. 28 . Thus, for example, pulses of air pressure variation may be sequentially applied first to one or more air bladder cells  524 A- 1  through  524 A- 10  in a first quadrant, e.g., the upper right-hand quadrant of air bladder cells shown in  FIG. 29 . Following introduction of first air pressure or pulses into air bladder cells  524 -A in the first quadrant of air mattress  523 , subsequent air pressure variation pulses may be introduced sequentially into air bladder cells located into quadrants B, C, and D, to thus produce a soliton traveling wave of body support force variation which travels in a clockwise sense on the upper surface of air mattress  523 . 
         [0285]    In an exactly analogous fashion, counterclockwise soliton traveling waves of body support force may be produced on the upper surface of air mattress  523  by introducing pulses of air pressure variation sequentially into air bladder cells  524  located in quadrants A, D, C, and B, respectively. 
         [0286]      FIGS. 30 and 31  illustrate circular air mattresses  603  and  623  which are exactly analogous in construction and function to oval air mattresses  503  and  523  described above, with the following single difference. Mattresses  603  and  623  are comprised of air bladder cells  604 ,  624  which have annular ring shapes that have a circular plan view rather than being oval-shaped. Thus air mattresses  603 ,  623  have an aspect ratio which is more suitable for matching the shape of a chair or wheel chair.