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 The present applications claims the benefit of U.S. Provisional Patent Application Ser. No. 60/053,999, entitled “Alternating Pressure Valve System,” filed on Jul. 28, 1997 and is a Continuation-in-Part of U.S. patent application Ser. No. 09/123,621 entitled “Alternating Pressure Valve System,” filed on Jul. 28, 1998.
 The present invention is generally related to an alternating pressure valve system for supplying fluid to an alternating pressure air mattress.
 Air mattress systems help prevent “bed sores” from developing in patients who are confined to laying on a mattress for long periods of time. The skin “interface pressure” tends to be much less because the patient is supported by a greater area than on a conventional mattress, so the blood supply to the skin is much improved. This therapy is further improved by the technique of “alternating pressure”, whereby the alternate air sacks of the mattress are inflated to a different pressure. The goal is to reduce the support pressure at half of the air sacks, while supporting the patient on the other half of the air sacks which are inflated. After a period of time, the configuration of deflated and inflated air sacks is switched, which means the patient is never supported at one place for an extended period of time. The alternating therapy allows for the skin that was under pressure to recover, have increased blood flow through the skin, and allows air to dry the skin, all of which helps to prevent skin ulcers.
 There are many alternating air pressure systems on the market today. Many of these systems are very complex and expensive. Typically, one half of the air sacks are inflated by a blower. After a period of time, solenoid valves open to release the pressure and air is then blown into the other half of the air sacks with its solenoid valves shut. Again after a period of time, the solenoid valves open to release the pressure and the first half of the air sacks are reinflated.
 The alternating pressure systems are typically complex and fairly expensive. What is needed therefore is an inexpensive simple alternating pressure system which alternates air in the different halves of the air sacks. What is also needed is an alternating pressure system that allows for alternating pressure while allowing for air flow in all the air sacks of the mattress.
 The present invention accomplishes the objectives of alternating pressure by the use of a motor-driven rotor valve within a valve assembly.
 The valve assembly as constructed has many important features. First, the valve is in the air discharge path from the blower, but prior to the mattress. Second, the valve has one inlet port to receive blower air, and two outlet ports to send the air on to the mattress through hoses. Third, the valve has a rotor with a wedge-shaped section that forms a type of shutter when positioned over a port leading to the mattress, thereby restricting the air flow through that port only. Fourth, the wedge feature can be positioned between the ports so as to restrict neither one, the mattress then being inflated to that same pressure over the entire surface. This mode is sometimes desired. Fifth, the rotor and wedge turn within a cylindrical cavity, but without touching the wall. Sixth, the rotor is supported by and rotated by a gearmotor shaft. Seventh, the rotor is positioned optically by means of light sensors. Eighth, the gearmotor is a DC motor and driven by a H-bridge circuit to allow reversing at the end of each cycle. Ninth, the cycle time in the preferred embodiment is about 3 minutes. And, tenth, the transit time (during which the rotor moves through about 120 degrees) is about 4 seconds.
 The understanding of the present invention will and the various aspects thereof will be facilitated by reference to the accompanying drawing figures, submitted for illustration only and not to limit the scope of the invention, where similar reference numerals are used for similar elements in the respective drawings, on which;
 The present invention provides an alternating pressure valve system for controlling the supply of fluid to an alternating pressure mattress. As used herein, like reference numerals will designate similar elements in the various embodiments of the present invention. Referring now to
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 A cable
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 Inside the rotor valve cylinder is a rotor valve
 The bottom of the valve is a bottom circular plate
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 Finally, when the rotor valve is rotated +60 degrees from the air intake axis the left air outlet
 The following describes the alternating pressure (“AP”) control circuit of the present invention:
 1. AP Switch and APsel Signal
 The AP switch, when pressed, charges a 0.1 μF capacitor through a 10K resistor for debounce, then the signal is cleaned up with an HC-14 inverter (U9), and finally toggled by an HC73 flip-flop (U8), The Q-bar output is “anded” in an HC08 AND gate (U10), with a signal from another HC08 AND gate (U12) that is high only when the blower is running, and MAX INFLATE is OFF. The resulting signal from the AND gate is named AP ENABLE, which means “OK to run the AP system”. AP operation is canceled when the system is in STANDBY or MAX INFLATE mode. AP function will resume, if previously activated, upon cancellation of MAX INFLATE.
 2. Sensor Signals
 The two sensors on the AP circuit board are positioned to face the back of the rotor, which has four reflective spots on it. The sensors each emit an infrared light, and have transistors that conduct when the light is returned by the presence of a reflector. The sensors are at two different radii, as are the reflective spots. The relationship between sensors and reflectors are such that the three parking positions of the rotor conform to three of the four binary combinations. The de-coding of the binary sensor data is performed by a HC139 on the AP unit's PCB. The output signals are buffered by an HC04, on the same board. These signals from the AP valve assembly are buffered by HC14 Schmidtt trigger invertors, so the resulting output is high when the sensor isn't illuminated. A “low” output is considered to mean that the rotor is in position over its sensor. There can be only one sensor output “low” at a time,
 The position signals are named. SenA “low” means the rotor is covering one of the ports, called port
 3. Trigger
 The trigger signal changes state when the rotor moves over or away from one of the 60 degree limit sensors. Signals SenA and SenC are “ANDED” to derive Trig. When these signals are both high, this means that the rotor is not over either port. The use of a 74HC08 AND gate provides a “low” output whenever the rotor moves so that it covers either port. This signal is inverted and delayed to allow data to settle at another I.C. This delayed signal is again inverted, so it also goes “low” when the turning rotor arrives over either port. Trig is used to initiate the timing sequence, which in effect disables the motor until the timer completes its cycle. Trig is also used to clock in the data that sets the motor terminal polarity. The operation is: Position signal SenC goes low, then the rotor moves from port
 4. Timer
 The timer signal is the output from the HC221, section B. This signal is combined into the motor drive signal (see below).
 5. Motor Drive Signal
 The electric motor is disabled or enabled by this signal. This signal is a logical combination of APsel, SenB, and Timer. SenB and APsel are “ORED” together so that when AP is turned off (APsel goes low) the motor will turn the rotor until the center position sensor (SenB) goes low. These two low signals result in a low output, “ANDED” with the Timer signal, that shuts off power to the motor by disconnecting the ground connection.
 AP Mode, Sequence of Events
 1. Initial—system running in normal mode; non-MAX INFLATE.
 2. AP Key pressed Debounced output goes low.
 3. FF “a” toggles. Output “Q” goes low, illuminating AP system LED.
 4. FF “a” output “Q bar” goes high. This is “ANDED” with U5-4; high when MAX INFLATE is off “ANDED” output goes high; signal name is “AP enable”.
 5. “AP enable” connects to U5-11, the reset of one-shot section “b”. With reset removed, this one-shot timer is ready to start.
 6. “AP enable” is “Ored” with “SenB” (the signal from the mid position rotor sensor). “SenB” is low because the rotor is parked over it.
 Currently, the AP circuit provides for 4 seconds of movement of the rotor valve from one side to the other, and then three minutes of no rotor valve movement until the rotor valve reverses to the other side. The three minute timing is currently preferred, however other timing from 0 seconds (constantly reversing pressure) to about five minutes of no valve movement is recommended for use depending on the patient's needs and condition. As would be recognized by a person skilled in the art, other timing sequences could also be used.
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 Other designs are also within the scope of this embodiment. For example, the pressure sensors could be placed anywhere along the air outlet pathway and could be placed within the air sacks themselves. Instead of using connectors
 The embodiment of
 While several particular embodiments of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. For example, different materials could be used in the different parts of the assembly. A microprocessor could be used to receive the signals from the detectors and then control the speed of the blower, the position of the rotor valve, and the duration of the rotor valve at any of the detected positions or detected pressures. Accordingly, it is not intended that the invention be limited except by the following claims.