Abstract:
A valve assembly for an air mattress having a common actuator on a manifold between opposed supply and exhaust valves moving the valves along actuating axes. The system includes a plurality of actuator/valve combinations for different portions of the air mattress. A pulsating valve is provided which includes a housing having therein supply and exhaust valves each directly controlled by supply and exhaust solenoids.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This application is a divisional of U.S. application Ser. No. 09/093,303, filed Jun. 9, 1998, which claims the benefit of U.S. provisional application Ser. No. 60/056,763, filed Aug. 25, 1997, both of which are incorporated by reference. 
    
    
     The present invention relates generally to a control valve system for air mattress or air cushion support surfaces and more specifically to a control valve system for air mattresses or support surfaces having a plurality of individually controllable chambers, for example, hospital beds. 
     Other cushion pressure control designs, which use one valve to isolate the cushion from a manifold, with either pressure or vacuum then applied to the manifold, cannot simultaneously increase the inflation of one cushion while exhausting from another. This means that adjusting the cushions in response to patient movement or changes in bed position takes longer, resulting in reduced comfort and possibly a less effective therapy. Also, this type of design cannot be used for the most effective type of patient rotation systems, which increase the pressure in one rotation cushion while simultaneously decreasing the pressure in another. 
     Other designs may use multiple valves with independent actuators to achieve the desired control conditions. This requires control wiring and space for each actuator. Also this does not insure that only one of the valves per pair is actuated at one time. 
     Bed cushions are typically inflated to pressures between ½ psi and 1 psi (25.9 and 51.7 mmHg). At these low pressures, the size of the flow opening in the valve must be relatively large in order to pass an adequate volume of air to inflate or deflate the cushion in a reasonable amount of time. 
     Existing valves which have large flow openings either have very large actuators, or are “pilot operated”. A pilot-operated valve uses a small actuator such as a solenoid to create a condition that causes a larger valve section to open. An example of this would be to use a solenoid to open a tiny valve which allows pressurized air to flow through into a chamber where it actuates a larger valve by pressing against a diaphragm. This type of pilot-operated valve generally requires that the minimum air pressure be 3 psi (155.1 mmHg) or higher, in order to create enough force to actuate the larger valve. The types of pressurized air sources that are most desirable for hospital bed cushions (high-flow low-pressure blowers) do not generally create a high enough pressure to actuate a pilot-operated valve unless the pilot device is very large. 
     Existing direct acting valves typically use electrical solenoids to operate a valve with a small opening. Since these valves are typically designed for higher pressures encountered in industrial and commercial applications, the valve openings are small. 
     The force acting against the operator for a direct-acting valve is typically equal to the pressure the valve is sealing against multiplied by the cross-sectional sealing area of the valve (F=P×A). In an industrial valve, this force might be 100 psi (5171.5 mmHg); if a valve had a cross-sectional sealing area of 0.20 inch (0.51 cm) (a practical area for the flows and pressures required by a hospital bed), the force to be overcome by the actuator would be 20 lbs (9.07 kg). However, in a hospital bed, the pressure would be on the order of 1 psi (51.7 mmHg), for a total force of only 0.2 lb (0.091 kg). 
     Because it is impractical to consider using a solenoid developing 20 lbs. (9.07 kg) of force due to the physical size and high electrical power consumption in high pressure industrial applications, these valves are generally designed with flow openings (valve orifices) having a cross-sectional area of on the order of 0.01 square inch (0.065 cm 2 ). This size opening is too small for the flow rates required at the lower pressures found in a hospital bed system. 
     Another limitation of prior art valve control structures is the ability to provide proportional flow control. 
     The valve seat and valve disk can be designed to be either flat, round or with varying amounts of taper. With a flat valve seat, a small amount of movement from the actuator causes a significant increase in flow through the valve. This type of seat and disk design is most useful when it is desirable to inflate a cushion as quickly as possible, or when it is desirable to create a pressure “pulse” with the sudden opening of the valve to high flow conditions. 
     As the amount of taper is increased on the valve seat and disk, a smaller change in flow is created for a given movement of the actuator. This makes it possible to control the rate of flow through the valve by controlling the positioning of the actuator. This characteristic is particularly useful in “low air loss” cushions, where air is continuously exiting the cushion through a fixed or variable size orifice. A valve with proportioning characteristics can be actuated to where it just provides sufficient air flow to balance against the loss of air from the cushion. As an alternative, the proportioning valve can be used on the discharge side of the cushion to create a variable size orifice to control the rate of discharge from the cushion. 
     Another use for the proportional flow control characteristics is to control rotation of the patient on the air cushion support surface. Studies have shown that a slow rotation created by simultaneously inflating one cushion while deflating another cushion is preferable to rapid rotation. 
     When an on/off type of valve is used to inflate or deflate a cushion, the delay time between sensing that the desired pressure has been reached and the time the valve is closed can cause “overshoot” that requires additional correction and adjustment. 
     A proportional valve can be opened to a full flow position initially to achieve a high rate of flow; then as the desired pressure is approached, the valve can be changed to a partial flow position to reduce or to eliminate the overshoot condition as the pressure sensor and bed controls detect the desired pressure being approached. 
     Proportional opening of valves will result in smoother initial inflation, avoiding pressure peaks or shock waves that may cause patient discomfort. Controlled proportional opening and closing of valves can also reduce the mechanical and air flow noise caused by valves which suddenly open and close. 
     In controlling the surface pressures of a multiple zone, bed conditions often arise that make it desirable that some cushions receive a higher rate of air flow than others. This may occur because one cushion has a higher volume than others, because the patient weight shifts from one cushion or set of cushions to another, or because of an operating mode change in the bed (for example, by going into a patient rotation mode). 
     With on/off valves, this can only be achieved by turning the valves on and off at different rates. Such a method of operation can cause uneven inflation, pressure surges, additional noise, and longer response times to achieve the desired cushion inflation rates. 
     In some circumstances, it is desirable to inflate some zones (e.g., side bolsters, head supports, and rotational cushions) to significantly higher pressures than other zones. This is often accomplished by increasing the pressure levels in the pressure supply manifold to serve the requirements of these “hyperinflated zones”. With valves having proportional control characteristics, it is possible to maintain accurate inflation control to the lower pressure zones by reducing the amount these valves open while the pressure manifold is in a hyperinflation state. 
     In other cases, the air supply may be limited for certain operational modes. For example, it may be desirable to inflate one or more cushion zones very quickly. If a less critical zone requires pressure at the same time, it may “rob” available air from the system, affecting the performance of the bed in meeting the requirements of the zone needing rapid inflation. Using a proportional valve allows the bed control system to restrict the opening of the less critical valves to allocate available air to the more critical locations. 
     This air apportioning capability can allow the use of small air sources, which require less electrical power, generate less noise, and occupy less space. 
     In the air cushion environment, an economic and effective actuator has not been found to proportionally position the valve. Solenoid control has been used for the on/off style control valves. Thus, the systems have not taken advantage of the tapered valve body and valve seat. 
     A control of an air mattress or cushion according to the present invention provides a unique proportional control valve. The system includes a manifold having at least a supply port, one exhaust port, and one outlet port connected to a chamber in the manifold. A supply valve and an exhaust valve are on the manifold having coaxial actuating axes and connected to the supply and exhaust ports respectively. A common actuator is on the manifold between the supply and exhaust valves so as to move the supply and exhaust valves along their actuating axes. The actuator is a linear actuator having first and second ends spaced from adjacent valve stems of the supply and exhaust valves in the neutral position of the actuator. The linear actuator preferably includes an electric motor. The actuator and valve stems are electrically isolated from each other and complete a circuit when engaged. This provides electrical feedback information. The valve bodies are molded from electrically insulated material. 
     The supply and exhaust valve each include a body having a first outlet connected to a respective port of the manifold, an inlet, and a valve seat having an inlet and an outlet side. A valve element on the outlet side of the seat includes a stem extending therefrom through the valve seat to be engaged at its first end by the actuator. A spring biases the valve onto the valve seat. The valve seat and the first outlet of the valve have generally an orthogonal axis. The valve body has a second outlet on the outlet side of the valve seat. The outlet port of the manifold is the second outlet of one of the valves. The second outlet of the other valve is plugged. The valve element and the valve seat include tapered portions. The valve element has a first tapered portion that defines a first rate of change of the size of valve opening and lower than the rate of change of a second tapered portion. The valve element includes a shoulder portion extending radially from the tapered portion. The valve seat has a cross-sectional area in the order of 0.10 to 0.40 square inch (0.065 to 0.26 cm 2 ). 
     A second end of the actuator extending from the valve element is one of the seats of the spring. The first end of the actuator extends through and is guided by an aperture in the valve body. The second end of the aperture is received in a guide in the housing. The guide also forms a second stop for the spring. The guide on the housing is either in the outlet port or on the plug of the respective valve housing. 
     The manifold includes a first and a second portion joined together to form the chamber connecting the valve ports. The first portion includes a flange to which the actuator is mounted. The exhaust and supply valves are mounted to the first portion. 
     To control a plurality of air cushions, the manifold includes a plurality of chambers, each chamber having a supply and exhaust valve mounted to a supply and exhaust port of each of the chambers. The supply valves have a common supply plenum connected in its inlet. The supply valves and the supply plenum are formed as an integral structure. The exhaust valves also include an integral common supply plenum. The supply plenum may include a divider partitioning the plenum into two supply plenums. Electrical controls are mounted on the manifold and are connected to the actuators for each pair of valves. The electrical controls include a plurality of pressure sensors, each connected to a respective chamber. A pressure sensor is also connected to the supply plenum. 
     A unique pulsating valve is provided and is used in a system with the control valve for an air mattress with a plurality of bladders. 
     The pulsating valve includes a supply chamber, exhaust chamber and plenum in a housing. A supply valve and exhaust valve in the housing connect the supply and exhaust chambers, respectively, to the plenum. Supply and exhaust solenoids are connected to and control the supply and exhaust valves. The valves are in and the solenoids are mounted to an interior housing and are covered by an exterior housing. The exterior housing defines the chambers with the interior housing. The housing includes at least one supply port, one exhaust port, and an outlet port and may include additionally a supply outlet. 
     The solenoids include a coil and a core in a casing, and the valves are connected to a first end of the core through a first aperture in the casing. The casing includes a second aperture opposed a second end of the core. The core is substantially hollow along its length. A resilient stop is provided between the casing and the second end of the core to act as a shock absorber. A resilient element is placed between the solenoid and interior housing also to provide isolation and vibration absorption. Vibration dampening mounts connect the housing to a support surface. 
     A valve assembly for an air mattress having a plurality of bladders includes a supply inlet, a first valve connected to the supply inlet, and at least one outlet to be connected to a first bladder for pulsating air signals to the first bladder. A second valve is provided connected to the supply inlet and least one outlet is to be connected to a second bladder for inflating and deflating the second bladder. The first valve has a supply outlet and the second valve is connected to the supply outlet of the first valve. The second valve includes a linear actuator for positioning the valve and the first valve includes a solenoid for operating the valve. The first valve produces pulses in the range of 1-25 Hertz. 
    
    
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a multiple cushion mattress in which proportional and pulsing valves of the present invention can be used; 
     FIG. 2 is an exploded view of a proportional valve incorporating the principles of the present invention; 
     FIG. 3 is a top cut-away view of the assembled proportional valve of FIG. 2 according to the principles of the present invention; 
     FIG. 4 is a side cut-away view of the assembled proportion valve of FIG. 3; 
     FIG. 4A is a cut-away of valve and manifold of FIG. 4; 
     FIG. 5 is a schematic of a pulsating valve according to the principles of the present invention; 
     FIG. 6 is an exploded view of a pulsating valve according to the principles of the present invention; 
     FIG. 7 is a side view of the assembly pulsating valve of FIG. 6; 
     FIG. 8 is an end cut-away view of the pulsating valve of FIG. 7; and 
     FIG. 9 is a cross-sectional view of a solenoid incorporating the principles of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As illustrated in FIG. 1, a mattress assembly  10  in which the valves of the present invention are to be used is illustrated. A pair of rotational cushions  22  is located in the bottom and run the longitudinal axis of the mattress assembly  10 . The rotational cushions  22  are selectively inflated and deflated to control the rotation therapy of a patient located on the mattress. A pair of identical proportional valves  28  and  30  is provided in the mattress and is to be discussed with respect to FIGS. 2-4. The lower cushion structure includes a lower head cushion  32  and lower body cushions  34  and  36 . Support surface bladder  38  is located on top of the cushions  32 ,  34 , and  36  and includes a head cushion  40 , a chest cushion  42 , a seat cushion  44 , and a foot cushion  46 . Support cushions  40 ,  44 , and  46  include an inner bladder section  48  and another bladder section  50  and  51  which are controllable from an air supply source. Air enters the mattress assembly  10  from a blower through inlet  54  coupled to a pulsating or a percussion/vibration valve  56  to be discussed in detail with respect to FIGS. 5-9. The air supply inlet  54  is also coupled to proportional valves  28  and  30  via hoses  58  and  60  respectively. Alternatively, a T-fitting could be used. 
     The mattress assembly further includes width extension cushions  74 ,  76 ,  78 , and  80  which are positioned outside the exterior of the mattress walls. The extension cushions  74 ,  76 ,  78 , and  80  are coupled together and to a select valve  82  which selectively connects the extension cushions to exhaust or via hose  104  to the proportional control valve  28 . The rotational bladders  22  are coupled to valves  28  and  30  by lines  88  and  90 . The lower body cushions  34  and  36  include internal bladders  94  and  96 , respectively, which are each coupled to a supply line  92  of the valve  30 . The external cushions  34  and  36  are coupled to outlets of valves  28  and  30  via lines  98  and  100 , respectively. 
     The central section  48  of the head support cushion  90  is coupled to an outlet of valve  28  by line  102 . Opposite sections  50  and  51  of the head support surface cushions are coupled to valves  28  and  30  by lines  104  and  106 , respectively. The chest support surface cushion  42  is coupled to valve  28  by line  108 . The chest support surface cushion includes internal bladders  110 ,  112 , and  114 . Bladder  110  is coupled to a first outlet of the pulsating valve  56  by line  116 ; bladder  112  is coupled to valve  156  by line  118 ; and bladder  114  is coupled to valve  56  via line  120 . 
     Side portions  50  and  51  of the seat support section  44  are coupled to valves  28  and  30  via lines  104  and  106 , respectively. The central portion of the seat support cushion  44  is coupled to valve  30  by line  122 . Opposite side sections  50  and  51  of the foot support cushions  46  are coupled by supply lines  104  and  106  to valves  28  and  30 , respectively. The central section  48  of the foot support cushion  46  is coupled to the valve  30  by supply line  124 . 
     Further details of the mattress  110  are disclosed in U.S. application Ser. No. 08/917,145, entitled “Mattress Assembly”, the disclosure of which is incorporated herein by reference. This mattress structure is but one of many structures of which the improved valves of the present invention are used. The valves to be described may be used with other cushions or air mattress structures. 
     Details of the proportional valves  28  and  30  will be described with respect to FIGS. 2,  3 , and  4 . The proportional valve includes a manifold  200  having a first manifold portion  202  and a second manifold portion  204  joined together by fasteners  206  through matching openings  208 . A gasket (not shown) is positioned between the first and second manifold portions. The first manifold portion  202  includes a flange  210  having actuator apertures  212 . The first manifold portion  202  also includes a plurality of apertures  214  for the supply valves,  216  for the exhaust valves, and  218  for the pressure sensor of the individual manifold chambers. 
     The second manifold portion  204  has a plurality of chambers  222  which align with the supply and exhaust apertures  214  and  216  of the first manifold section  202 . A sensing area  224  aligns with apertures  218  for pressure sensor nipple  220 . The actuators  226  are mounted in actuator aperture  212  of flange  210  of the first manifold portion  202  by fasteners  228  through aligned openings  230  on mounting bracket  232  and flange  210 . 
     The actuator  226  is a linear actuator having a pair of opposite extending arms  234  and  236 . Preferably, the actuator  226  is a stepper motor turning a threaded bushing that causes a threaded shaft to move in either of two directions, depending upon the rotational direction of the motor. Preferably, the shaft includes arms  234  and  236  which include splines to prevent rotation of the threadable shaft. The stepper motor is designed to provide precise control of the amount of rotation and can be rotated in increments of one step or microsteps. The rate of stepping or the number of steps can be controlled by motor drive controls. This control of the rating stepping and the number of stepping provides precise control of the movement of the valve actuator arms  234  and  236  to provide the precise control of the valve and therefore the air flow control. The movement of the actuator is linear in the order of 0.001 inch (0.00254 cm) per step on the motor, for example. Servomotors or other electrical or pneumatic motors in a closed loop system with pressure sensors could be used. 
     The stepper motor of the linear actuator  226  uses a gear ratio affect to multiply the actuation force supplied to the valves relative to the amount of power applied to the drive motor. Thus, an actuator  26  with a power consumption of 3-5 watts can be used instead of a solenoid or other actuators with power consumptions of 10-30 watts. With the six pairs of valve structure illustrated in FIGS. 3 and 4, this is a considerable savings in power. An example of a stepper motor is Model Z26561-12-004 from Haydon Switch and Instrument, Inc. 
     The gear ratio on the actuators also provides a mechanical lock for the actuator at a fixed position if power is removed from the actuator. The gears oppose and resist movement from a restoring spring of the valves to be discussed. 
     Supply valves  238  and exhaust valves  240  are also mounted to the first manifold portion  202 . The supply valves  238  and the exhaust valves  240  are identical except for the areas to be noted. They each include a plenum  242 . The supply element  242  includes at one end a supply connector  244  which is connected to a source and a plug  246  at the other end. For the exhaust valve  240 , both ends of the plenum  242  may be opened or one end selectively plugged. It should also be noted that the plenum  242  may be divided into two plenums by providing a partition in the plenum and by including a supply connector  244  at each end of the plenum. 
     Also, connected to each of the plenums  242  are a plurality of valve bodies  248 . Six valve bodies are illustrated. The plenum  242  and the valve bodies  248  are formed as a single piece and preferably are a molded piece of electrically insulated material. The supply valves  238 , the exhaust valves  240 , and the plenums  242  are mounted to the first manifold portion  202  by a plurality of hold downs  250  of fastener  252 . Hold downs  250  have radius surfaces  254  to engage adjacent surfaces of the valve bodies  248 . In the preferred embodiment, three hold downs  250  are used for each of the integral valve/plenum structure, each engaging a pair of valve bodies  248 . Less or more than three may be used. It should be noted that the hold downs  250  are not shown in FIGS. 3 and 4. 
     Referring to FIGS. 4 and 4A, the valve body  248  has a valve seat  256  which is connected to the inlet or plenum  244  on one side and connected to a pair of outlets  258  and  260  on the other side. The outlet  258  is received in and connected to apertures  214  and  216  of the first manifold portion  202 , thereby connecting the other side of the valve seat to chamber  222 . The second outlet  260  of the exhaust valve is blocked by a plug  262 . The second outlet  260  of the supply valve includes an outlet connector  264 . A hose connector  266  is secured to the outlet connector  264  by a staple  268  to form thereby a quick disconnect. Although the supply valve&#39;s second outlet  260  is shown as the output of the manifold, alternatively the exhaust valve&#39;s second outlet  260  may be the output of the manifold in chamber  222 . 
     The cross-sectional area of the valve seat  256  is in the order of 0.20 square inch (1.29 cm 2 ) and may be in the range of 0.01 to 0.04 square inch (0.065 to 0.26 cm 2 ). This cross section provides the appropriate high flow volume at low pressure drops across the valve. Typical air flow is in the range of 5 to 45 cubic feet (141.6 to 1274.3 liters) per minute with pressure drops of 5 to 6 inches of water column (127.0 to 152.4 mmHg). 
     The valves further include a valve element  270  to be received on valve seat  256 . As shown in FIG. 4A, the valve element  270  includes a tapered portion  272  and a shoulder portion  274  extending radially from the tapered portion  272 . The tapered portion  272  includes a first taper  271 , a second greater taper  273 , and a third taper  275  greater than the second taper  273 . As the valve opens, the different tapers provide different rates of change of the size of the valve opening. By way of example only, the first taper is substantially zero for an axis distance of 0.015 inch (0.038 cm) and has a diameter smaller than the diameter of the valve seat. The second taper  273  is at 11° for an axial length of 0.044 inch (0.11 cm). The third taper  275  is at 45° for an axial length of 0.038 inch (0.097 cm). The shoulder  274  includes a taper  277  to make a more conformal sealing against the valve seat  256  when the valve is closed. For example, the taper  277  is at 50°. The taper angle of the valve seat  256  is greater than the tapered angle of the tapered portion  272  of the valve element. This allows the valve element to seat and seal better with less opportunity to stick to the seat. 
     The valve element  270  is mounted to a valve stem  276  in a recess  278 . A threaded bore  280  in a first end of the stem  276  receives a threaded portion of a tip  282 . One side of the valve stem  276  extends through the valve seat  256  and the plenum  242  and through an aperture  286  in the wall of the plenum  242 . The tip  282  is then screwed into the threaded port  280 . The aperture  286  acts as a guide and support for the one side of the stem  276 . The opening  286  is a few thousands of an inch (cm) larger in diameter than the valve stem  276 . Since the plenum  242  is not connected to the outlet for the bed cushions when the valve is closed, it is not essential that the opening  286  be air tight. If more capacity is needed, opening  286  may be sealed. 
     When both the supply valve  238  and the exhaust valve  240  are closed, and the actuator  226  is in its neutral position, the ends of the arms  234  and  236  of the actuator are evenly spaced from the tips  282  of the valve the stems  276 . The actuator  226  rotates in one or the other direction to extend one of the arms  234 ,  236  to engage the tips  282  of the valve stem  276  in opening  284  to open the respective valve. 
     Thus, in effect, the electrical actuator  226  in combination with location of the spring closed valves produces the effect of a three-way valve with a lap position. It does it without any pilot pressure and merely by the use of springs and electrical mechanical actuator. 
     The other end of the valve stem  276  includes a bore  288  to receive and be a stop for one end of a spring  290 . The plug  262  and the outlet connector  264  in the outlet  260  of the valve housing includes a bore  292  in a cylindrical section which receives the other end of the spring  290  and the end of the actuator  276 . The end of valve stem  276  rests in bore  292  for its total length of travel between its open and closed position. On the connector  264 , the cylindrical portion with bore  292  is suspended in the outlet  260  by support vanes  294 . The bore  292 , by receiving the other end of the valve stem  276 , provides a guide and support for the other end. Thus, the valve stem  276  is guided and supported on both of its ends. This improves the stability and alignment of the valve element  270  on the seat  256 . 
     As can be seen from FIG. 4, the valve seat  256  is coaxial with the outlet  260  and generally orthogonal to the outlet  258  which connects to the chamber  222 . It should also be noted that the actuator or valve stem  276  of the supply and exhaust valves are coaxial so as to be easily operated by a single actuator  226 . If the outlet  260  were placed orthogonal to the valve seat  256 , a separate support structure for the other end of the actuator  276  would have to be provided. If the outlet  258  to chamber  220  was coaxial to the valve seat  256 , it would include the appropriate guide  292 . 
     The spring  290  provides force needed to close the valve and to press the valve element  270  on the valve seat  256  against any air leakage when the valve is closed. The location of the valve element on the outlet side of the valve seat allows any additional pressure placed on the cushion or mattress and being fed back to the inlet  260  to apply further pressure on the valve and maintain them closed. It also allows the use of a vacuum instead of an exhaust on the plenum  242  of the exhaust  240 . This will also further increase the closure of the valve. 
     The electrical control portion  296  is in a housing and secured to the second manifold portion  204  by fasteners  298 . The electrical controls include the appropriate electronics to operate the actuator based on commands and feedback or measured signals. The electronic control  296  includes a plurality of pressure sensors  300  connected by a hose  302  to the nipple  220 , one for each of the chambers  222 . An additional pressure sensor  304  to monitor the supply is connected by a hose  306  to nipple  308  in the supply plenum  242 . 
     Preferably, the valve shaft  276  is made of metal, and the valve housing and plenum is made of a molded dimensionally stable thermoplastic, for example, glass-filled nylon. To determine when one of the arms  234 ,  236  of the actuator engages one of the valve stems  276 , electrical slide connections  310  and  312  are mounted to, for example, the metal arm  236  of the actuator and the metal valve stems  276  as illustrated in FIG. 4 for the exhaust valve  240 . Since the valve housing and plenum are made of electrically insulated material, the arms  234  and  236  are electrically isolated from the valve stems  276 . The connection completes a circuit in the control electronics  296 . 
     By monitoring these connections, the control electronics  296  can determine just when the valve actuator arms touch the valve stem  276  to begin to open the valves. The controls can then use this information to establish a zero positioning for opening the valve element  270 . By counting pulses or steps into the stepper motor from this point forward, the controller can estimate the valve disposition and the orifice opening with great precision. With knowledge of the taper, the valve and the seat relative axial position, control and regulation may be performed. If space or cost is not a factor, additional encoders can be provided to the stepper motor and provide closed loop positioning control. 
     A cover  314  is secured to the second manifold portion  204  by fasteners  316  through aligned openings  318 . Fasteners  320  provided through openings  322  secure the manifold and all of the elements mounted thereto to a mattress or other support structure. The cross-sectional area of the valve seat  256  is in the order of 0.20 square inch (1.29 cm 2 ) and preferably in the range of 0.10 to 0.40 square inch (0.065 to 0.26 cm 2 ). 
     Although the schematic FIG. 2 has shown the valves  20  and  30  as part of the mattress, they may be separate and the connections may be made to the mattress. 
     A schematic for the pulsating valve  56  is illustrated in FIG.  5 . The valve housing  330  has a supply chamber  332 , an exhaust chamber  334  and a plenum  336 . The supply chamber  332  has an inlet  338  receiving pressure from connection  54  and a pair of outlets  340  and  342  connected to hoses  58  and  60 . The pressurized air flow from inlet  338  flows directly to the outlets  340  and  342  and is not controlled by the valve. This particular structure is for the unique mattress configuration. If the pulsating valve  56  is not used as the single connection to the exterior source or supply of pressurized air for a system, outlet ports  340  and  342  either may be eliminated or plugged. The exhaust chamber  334  is connected to atmosphere via exhaust port  344 . The plenum  336  includes outputs  346 ,  348 , and  350  connected to lines  116 ,  118 , and  120 , respectively. 
     A supply valve or solenoid  352  controls the opening of the port  354  connecting the supply chamber  332  to the plenum  336 . An exhaust valve or solenoid  356  controls the connection of the plenum  336  to the exhaust chamber  334  through port  358 . The ports  354  and  358  have an opening in the range of 0.20 to 0.50 square inch (1.29 to 3.23 cm 2 ) for the low operating pressures, for example, in the range of 1 to 2 psi (51.7 to 103.4 mmHg). The large opening allows use of larger solenoids. The valve structure and solenoids are capable of being operated to produce a percussion pulse in the range of 1-5 Hertz and a vibration pulse in the range of 6-25 Hertz. The electrical controller alternates energization of the supply solenoid  352  and the exhaust solenoid  356  to produce the air pressure pulses or impulses. 
     Referring specifically to FIG. 6, the housing  330  includes an exterior housing  360  having a pair of end walls  362  and  364  screwed thereto by fasteners (not shown) through aligned opening  356 . Each end walls  362  and  364  includes a gasket  368 . A connector  370  is provided in supply outlet  340  and a connector  372  is provided in outlet  342  in an end wall  364 . They are secured by fasteners not shown. A mounting plate  374  connects outlet connectors  376  in the outlet ports  346 ,  348 , and  350  in the side wall of the housing  360 . The connectors  376  in combination with hose connectors  378  and staples  380  form a quick disconnect. 
     An interior housing  382  includes a top wall  384 , a first intermediate wall  386 , a second intermediate wall  388 , and a bottom wall  390 . It also includes a solid back wall  392 , a front face  394  having an opening area, a first side wall  396  having an opening area, and a solid side wall  398 . Interior wall  400  between intermediate walls  386  and  388  define the supply chamber  332  and exhaust chamber  334 . The second intermediate wall  388  and the bottom wall  390  define the plenum  336 . Apertures  404  in the first intermediate wall  386  and apertures  402  in the top wall  384  receive the body of the solenoid valves  352  and  356 . An O-ring  406  positions the body of the solenoids  352  and  356  in a recess or shoulder in aperture  402  in the top wall  384  and provides vibration isolation and maintains equal radial distance of solenoid to housing. Other noise reduction measures include a soft rubber, fabric or leather disc between the face of solenoids  352  and  356  and the solenoid mounting surface adjacent openings  404  in intermediate wall  386 . A strap  408  secures each of the solenoids  352  and  356  to the interior housing  82  by fasteners (not shown) through aligned fastener opening  410 . Valve seats  412  are provided in ports  354  and  358  in the intermediate wall  388  and mate with valve elements  414  mounted to plungers  416  of the solenoid valves  352  and  356  by fastener  418 . 
     The interior housing  382  and the solenoid valves  352  and  356  mounted thereon are slid into the exterior housing  360  with a gasket  420  on a portion of the front face  394  and secured thereto by the fasteners which secure the mounting plate  374  as well as three additional fasteners. This aligns the plenum  336  adjacent the outlets  346 ,  348 , and  350 . It also aligns the exhaust port  344  with respect to the exhaust chamber  334 . Since the interior housing  382  does not extend the full length of the exterior housing  360 , the area between the interior housing and exterior housing forms a continuation of the supply chamber  332  and connects the supply inlet  338  to the supply outlets  340  and  342 . 
     Preferably, the interior housing  382  is a cast aluminum block to operate as a heat sink for the solenoids  352  and  356 . Also, the valve seats  412  are preferably rubber while the valve elements  414  are also aluminum. Driver card  422  is mounted to the exterior housing  360  and covered by cover plate  424  shown in FIG.  8 . 
     Details of the solenoid are shown in FIG. 9 The solenoids include a casing  426  and a coil  428  in which the core  444  rides. The plunger  416  is press fit in a bore  442  with a magnetic core  444 . A nylon sleeve or bearing  430  separates the core  444  from the coil  428 . Because of the high frequency of operation, the standard brass sleeve or bushing is not used. Spring  436  rests in a bore  432  in core  444  and bore  434  in the top wall of the casing  426 . An O-ring  438  acts as a stop/shock absorber between the top wall of the casing  426  and the core  444 . An opening  440  is provided in the top wall exposing the cavity between the top of the core  444  and the bottom of the top wall of the casing  426 . It has been found that this vent is needed to prevent pressure/vacuum locking of the plunger. This substantially increases the speed or frequency capability of the solenoid. 
     As illustrated in FIG. 7, the exterior housing is mounted by a vibration dampening mount  446  to a surface  448  through extensions  450  of end walls  363  and  364 . 
     Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.