Abstract:
A pressure and vacuum valve manifold system such as may be used, for example, to actuate pneumatic bladders controlling airflow in a forced air HVAC system to provide zone climate control. The valves are individually operable to connect a respective individual bladder to pressure or to vacuum. Two manifolds can be mated and commonly fed pressure and vacuum. The two manifolds can be of identical construction. One manifold chamber from each can be connected into a single large pressure manifold, and another manifold chamber from each can be connected into a single large vacuum manifold. Such connections can be made with fittings which also serve as pressure and vacuum relief valves, respectively. The valve plungers are arranged in a grid, enabling a simple X-Y two-motor servo system to actuate all the valves, one at a time. The valves may be arranged such that the valves of one manifold are one half increment offset from the valves of the other manifold, enabling a single actuator having two actuator fingers to operate only a single manifold&#39;s valve at a time.

Description:
RELATED APPLICATIONS  
       [0001]     This application is related to application Ser. No. 10/750,709, titled Valve Manifold for HVAC Zone Control, filed Jan. 2, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field of the Invention  
         [0003]     This invention relates generally to HVAC (heating, ventilation, and air conditioning) systems, and more specifically to a valve manifold mechanism for operating duct airflow control bladders.  
         [0004]     2. Background Art  
         [0005]      FIG. 1  is a block diagram of a typical forced air system. The existing central HVAC unit  10  is typically comprised of a return air plenum  11 , a blower  12 , a furnace  13 , an optional heat exchanger for air conditioning  14 , and a conditioned air plenum  15 . The configuration shown is called “down flow” because the air flows down. Other possible configurations include “up flow” and “horizontal flow”. A network of air duct trunks  16  and air duct branches  17  connect from the conditioned air plenum  15  to each air vent  18  in room A, room B, and room C. Each air vent is covered by an air grill  31 . Although only three rooms are represented in  FIG. 1 , the invention is designed for larger houses with many rooms and at least one air vent in each room. The conditioned air forced into each room is typically returned to the central HVAC unit  10  through one or more common return air vents  19  located in central areas. Air flows through the air return duct  20  into the return plenum  11 .  
         [0006]     The existing thermostat  21  is connected by a multi-conductor cable  73  to the existing HVAC controller  22  that switches power to the blower, furnace and air conditioner. The existing thermostat  21  commands the blower and furnace or blower and air conditioner to provide conditioned air to cause the temperature at the thermostat to move toward the temperature set at the existing thermostat  21 .  
         [0007]      FIG. 1  is only representative of many possible configurations of forced air HVAC systems found in existing houses. For example, the air conditioner can be replaced by a heat pump that can provide both heating and cooling, eliminating the furnace. In some climates, a heat pump is used in combination with a furnace. The present invention can accommodate the different configurations found in most existing houses.  
         [0008]     Pneumatic and hydraulic valve systems are well known in a variety of industries. Most valve systems comprise only a single valve which is actuated to control the flow of a single fluid under pressure or vacuum. Most valve systems are, essentially, binary switches, such as a pneumatic valve which selectively fully couples or fully decouples a tire inflation chuck from an air pressure source such as a pressurized tank. Other valve systems provide a more analog control, such as a hydraulic control valve which enables a heavy equipment operator to provide a variety of pressures or flows of hydraulic fluid from a (single pressure) high pressure supply pump to a hydraulic ram actuating an articulating bucket or other such component. Still other valve systems include a battery of plural valves, each controlling the flow of a respective individual fluid, such as a multi-beverage fountain dispenser from which a consumer can retrieve any of a variety of soft drinks from respective ones of a variety of nozzles. In this latter instance, the individual valves not only control the flow of their respective soft drink syrups, but they are each also coupled to a common carbonated water supply.  
         [0009]     What is not available, however, is a valve manifold which enables individual valves to be operated to each independently select between two or more fluid flows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The invention will be understood more fully from the detailed description given below and from the accompanying drawings of embodiments of the invention which, however, should not be taken to limit the invention to the specific embodiments described, but are for explanation and understanding only.  
         [0011]      FIG. 1  shows a typical forced air residential HVAC system.  
         [0012]      FIG. 2  shows the present invention installed in the HVAC system illustrated in  FIG. 1 .  
         [0013]      FIG. 3  shows, in cross-section, one air valve of a plurality of servo-controlled air valves according to embodiments of this invention.  
         [0014]      FIG. 4  shows two blocks of air valves and a connecting air-feed tee according to embodiments of this invention.  
         [0015]      FIG. 5  shows one embodiment of a valve servo according to this invention.  
         [0016]      FIG. 6  shows the valve servo positioned over one of the air valves.  
         [0017]      FIG. 7  shows one embodiment of the position servo.  
         [0018]      FIG. 8  shows one embodiment of the air pump enclosure and its mounting system.  
         [0019]      FIG. 9  shows one embodiment of the pressure and vacuum relief valves.  
         [0020]      FIG. 10  shows the control processor printed circuit board mounted in the main enclosure according to one embodiment of this invention.  
         [0021]      FIG. 11  shows another embodiment of a valve block or manifold.  
         [0022]      FIG. 12  shows a cutaway view of the manifold of  FIG. 11 .  
         [0023]      FIG. 13  shows one embodiment of a manifold cover.  
         [0024]      FIG. 14  shows a manifold assembly including the manifold of  FIG. 11  and the manifold cover of  FIG. 13 .  
         [0025]      FIG. 15  shows another embodiment of a valve plunger according to this invention, suitable for use with the manifold assembly of  FIG. 14 .  
         [0026]      FIG. 16  shows another embodiment of a pressure relief valve.  
         [0027]      FIG. 17  shows the pressure relief valve in cutaway.  
         [0028]      FIG. 18  shows another embodiment of a vacuum relief valve.  
         [0029]      FIG. 19  shows the vacuum relief valve in cutaway.  
         [0030]      FIGS. 20 and 21  shows a completed valve assembly according to another embodiment of this invention.  
         [0031]      FIGS. 22 and 23  show a cross-section view of the actuator moving a manifold valve to the in and out positions, respectively, in accordance with one embodiment of the invention.  
         [0032]      FIGS. 24 and 25  show a cross-section view of the actuator moving a manifold valve to the in and out positions, respectively, in accordance with another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0033]     Overview of the System  
         [0034]      FIG. 2  is a block diagram of the present invention installed in an existing forced air HVAC system as shown in  FIG. 1 . The airflow through each vent is controlled by an airtight bladder  30  mounted behind the air grill  31  covering the air vent  18 . The bladder is either substantially inflated or deflated while the blower  12  is forcing air through the air duct  17 . A small air tube  32  (˜0.25″ OD) is pulled through the existing air ducts to connect each bladder to one air valve of a plurality of servo controlled air valves  40  mounted on the side of the conditioned air plenum  15 . There is one air valve for each bladder. A small air pump in air pump enclosure  50  provides a source of low-pressure (˜1 psi) compressed air and vacuum at a rate of ˜1.5 cubic feet per minute. The pressure air tube  51  connects the pressurized air to the air valves  40 . The vacuum air tube  52  connects the vacuum to the air valves  40 . The air pump enclosure  50  also contains a 5V power supply and control circuit for the air pump. The AC power cord  54  connects the system to 110V AC power. The power and control cable  55  connect the 5V power supply to the control processor and servo controlled air valves and connect the control processor  60  to the circuit that controls the air pump. The control processor  60  controls the air valve servos  40  to set each air valve to one of two positions. The first position connects the compressed air to the air tube so that the bladder inflates. The second position connects the vacuum to the air tube so that the bladder deflates.  
         [0035]     A wireless thermometer  70  is placed in each room in the house. All thermometers transmit, on a shared radio frequency of 433 MHz, packets of digital information that encode 32-bit digital messages. A digital message includes a unique thermometer identification number, the temperature, and command data. Two or more thermometers can transmit at the same time, causing errors in the data. To detect errors, the 32-bit digital message is encoded twice in the packet. The radio receiver  71  decodes the messages from all the thermometers  70 , discards packets that have errors, and generates messages that are communicated by serial data link  72  to the control processor  60 . The radio receiver  71  can be located away from the shielding effects of the HVAC equipment if necessary, to ensure reception from all thermometers.  
         [0036]     The control processor  60  is connected to the existing HVAC controller  22  by the existing HVAC controller connection  74 . The control processor  60  interface circuit uses the same signals as the existing thermostat  21  to control the HVAC equipment. The existing thermostat connection  73  is also connected to the control processor  60  interface circuit that includes a manual two position switch. In the first switch position, the HVAC controller  22  is connected to the control processor  60 . In the second switch position, the HVAC controller is connected to the existing thermostat  21 . The existing thermostat  21  is retained as a backup temperature control system.  
         [0037]     The control processor  60  controls the HVAC equipment and the airflow to each room according to the temperature reported for each room and according to an independent temperature schedule for each room. The temperature schedules specify a heat-when-below-temperature and a cool-when-above-temperature for each minute of a 24-hour day. A different temperature schedule can be specified for each day for each room. These temperature schedules are specified by the occupants using an interface program operating on a standard PDA (personal data assistant)  80 . PDAs are available from several manufacturers such as Palm. The interface program provides graphical screens and popup menus that simplify the specification of the temperature schedules and the assignment of schedules to rooms for the days of the week and for other special dates. The PDA  80  includes a standard infrared communications interface called IrDA that is used to communicate with the control processor  60 . The IrDA link  81  is mounted in the most convenient air vent  18 , behind its air grill  31 . The IrDA link  81  has an infrared transmitter and receiver mounted so that it can communicate with the PDA  80  using infrared signals though the air grill. The IrDA link  81  is connected to the control processor  60  by the link connection  82  that is pulled through the air duct with the air tube to that air vent. After changes are made to the temperature schedules, the PDA  80  is pointed toward the IrDA link  81  and the standard IrDA protocol is used to exchange information between the PDA  80  and the control processor  60 .  
         [0038]     The IrDA link  81  also has an audio alarm and light that are controlled by the control processor  60 . The control processor can sound the alarm and flash the light to get the attention of the house occupants if the zone control system needs maintenance. The PDA  80  is used to communicate with the control processor  60  to determine specific maintenance needs.  
         [0039]     The present invention can set the bladders so that all of the airflow goes to a single air vent, thereby conditioning the air in a single room. This could cause excessive air velocity and noise at the air vent and possibly damage the HVAC equipment. This is solved by connecting a bypass air duct  90  between the conditioned air plenum  15  and the return air plenum  11 . A bladder  91  is installed in the bypass  90  and its air tube is connected to an air valve  40  so that the control processor can enable or disable the bypass. The bypass provides a path for the excess airflow and storage for conditioned air. The control processor  60  is interfaced to a temperature sensor  61  located inside the conditioned air plenum  15 . The control processor monitors the conditioned air temperature to ensure that the temperature in the plenum  15  does not go above a preset temperature when heating or below a preset temperature when cooling, and ensures that the blower continues to run until all of the heating or cooling has been transferred to the rooms. This is important when bypass is used and only a portion of the heating or cooling capacity is needed, so the furnace or air conditioner is turned on only for a short time. Some existing HVAC equipment has two or more heating or cooling speeds or capacities. When present, the control processor  60  controls the speed control and selects the speed based on the number of air vents open. This capability can eliminate the need for the bypass  90 .  
         [0040]     A pressure sensor  62  is mounted inside the conditioned air plenum  15  and interfaced to the control processor  60 . The plenum pressure as a function of different bladder settings is used to deduce the airflow capacity of each air vent in the system and to predict the plenum pressure for any combination of air valve settings. The airflow to each room and the time spent heating or cooling each room is used to provide a relative measure of the energy used to condition each room. This information is reported to the house occupants via the PDA  80 .  
         [0041]     This brief description of the components of the present invention installed in an existing residential HVAC system provides an understanding of how independent temperature schedules are applied to each room in the house, and the improvements provided by the present invention. The following discloses the details of each of the components and how the components work together to proved the claimed features.  
         [0042]     Servo Controlled Air Valves  
         [0043]      FIG. 3  shows several views of one air valve of a plurality of servo controlled air valves  40 . One embodiment has two valve blocks made of plastic using injection molding. Each valve block is approximately 1″×2″×7″ and contains valve cylinders for 12 valves.  
         [0044]      FIG. 3A  is a cross section view of one valve block  501  sectioned through one of the valve cylinders  502 . Each valve cylinder is 0.375″ in diameter and approximately 1.875″ deep. Each valve cylinder has three holes (˜0.188″) that connect the cylinder to the pressure cavity  503 , the valve header  504  (shown in cross section), and the vacuum cavity  505 . The valve header  504  connects the air tube  32  (shown in full view) to the valve cylinder and provides one side of the pressure and vacuum cavities in the valve block. The valve header is made of plastic using injection molding and is glued to the valve block to form airtight seals. The air tube  32  is press fit into the air tube hole  506  in the valve header. The inside of the air tube hole has a one-way compression edge  507  making it difficult to pull the air tube from the header after it has been inserted. The valve block is mounted on a side of the conditioned air plenum  15  so that the portion of valve header  504  connecting to the air tube is inside the plenum and the portion of the valve header sealing the pressure and vacuum cavities and the valve block  501  are outside the plenum.  
         [0045]      FIG. 3C  is a perspective view of the valve slide  510  and  FIG. 3D  is a top view of the same valve slide. The valve slide has grooves for O-ring  511  and O-ring  512 . The valve slide has a valve lever  514  that protrudes above the valve plate  515 . The valve lever is used to move the valve slide inside the valve cylinder.  
         [0046]      FIG. 3A  and  FIG. 3B  represent the same air valve in two different positions. The valve slide  510  (shown in full view) fits snugly inside the valve cylinder  502  so that the O-rings seal the cavities formed by the cylinder wall and the valve slide. The slide valve has two resting positions, the pressure position  520  shown in  FIG. 3B  and the vacuum position  521  shown in  FIG. 3A . The air pump  50  is turned on only when the valves are in one of these two positions. The air pump is off while the valves are moved. Referring to  FIG. 3B , when the slide valve is in the pressure position  520 , O-ring  511  seals the vacuum cavity and the valve cylinder from the air tube. The cavity formed between O-ring  511  and O-ring  512  connects the pressure cavity to the air tube so pressurized air will flow through the air tube to inflate the bladder. O-ring  512  seals the valve cylinder from the outside air. Referring to  FIG. 3A , when the slide valve is in the vacuum position  521 , the vacuum cavity is connected to the air tube and O-ring  511  seals the vacuum cavity from the pressure cavity. The bladder is deflated as air flows through the air tube towards the vacuum created by the air pump. O-ring  511  and O-ring  512  seal the pressure cavity from the air tube and outside air. The valve slide is moved to either the pressure position  520  or the vacuum position  521  by a servo that engages the valve lever  514 .  
         [0047]      FIG. 3E  shows an end view of a valve slide as positioned when in a valve cylinder. The valve lever  514  and valve plate  515  are constrained from rotating about the valve cylinder axis by a slot  516  in the valve constraint  513 . The valve constraint has a slot  516  for each valve slide.  FIG. 3A  also shows a side view of the valve plate  515  and the valve constraint  513 .  
         [0048]      FIG. 4  shows several views of the two valve blocks  601  and  602  and air-feed tee  603 .  
         [0049]      FIG. 4A  is a cross-section view through the axis of the valve cylinders of valve block  601  and valve block  602  positioned so that the valve slides  510  (shown in full view) are interleaved. Interleaving minimizes the spacing between valve slides and aligns the valve levers  514  so the valve servo can move the valve slides in valve blocks  601  and  602 . Some of the valve slides are shown in the pressure position and the others are shown in the vacuum position. The valve constraint  513  has  24  slots  516  that engage the  24  valve slide plates to prevent rotation of the valve slides about the valve cylinder axis. The ends of the valve blocks  601  and  602  have passageways from the pressure and vacuum cavities to the air-feed tee  603 . O-rings  606  seal the connections between the air-feed tee and these passageways.  
         [0050]      FIG. 4B  is an end cross-section view through the section line shown in  FIG. 4A  of the passageways in the valve blocks  601  and  602  to the pressure cavities  503  and vacuum cavities  505 . The air-feed tee  603  is shown in full view. Four O-rings  606  seal the air-feed tee to the valve blocks. The air-feed tee has a vacuum connection  604  that connects to the vacuum air tube  52  and a pressure connection  605  that connects to the pressure air tube  51 . The valve levers  514  protrude beyond the surface of the valve blocks.  
         [0051]      FIG. 4D  is a top view of the air-feed tee  603  and o-rings  606  in isolation from the valve blocks.  FIG. 4C  is a cross-section view (through the section line shown in  FIG. 4E ) of the air-feed tee and the vacuum connection  604 .  FIG. 4E  is a front view of the air-feed tee in isolation.  FIG. 4F  is a cross-section view (through the section line shown in  FIG. 4D ) of the air-feed tee through the center of the passageways connecting to the pressure and vacuum cavities.  
         [0052]      FIG. 3F  is a cross section view of one valve block  501  sectioned through one of the valve cylinders  502 . Each valve cylinder has dimensions similar to valve cylinder  502  in  FIG. 3A , in one embodiment of the invention. Each valve cylinder has three holes that connect the cylinder to the pressure cavity  503 , a valve header  506 , and the vacuum cavity  505 . The valve header, as in the case of the embodiment illustrated in  FIG. 3A , connects an air tube to the valve cylinder and provides one side of the pressure and vacuum cavities in the valve block. In one embodiment of the invention, the valve block is mounted on a side of the conditioned air plenum  15  so that the portion of valve header connecting to the air tube is inside the plenum and the portion of the valve header sealing the pressure and vacuum cavities and the valve block  501  are outside the plenum.  
         [0053]      FIG. 3H  is a perspective view of a valve slide, or valve plunger,  510  in one embodiment of the invention, and  FIG. 31  is a top view of the same valve slide. The valve slide includes a shaft having a first and second seal at each end. The first seal has grooves for O-ring  511  and the second seal grooves for O-ring  512 . In one embodiment, the outer diameter of the shaft is less than the outer diameter of the seals. The valve slide  510  has two actuator surfaces, referenced as push tab  525  and pull tab  526  in  FIGS. 3F-3J , that each protrudes above a platform  533  of slide  510 . As illustrated, the actuator surface comprises a rectangular flange extending substantially normal from the platform of the valve guide in a plane substantially perpendicular to the cylinder axis. An actuator pushes and pulls on the respective push and pull tabs to move the valve slide inside the valve cylinder, as described further below. In an alternative embodiment of the invention, a single tab may be utilized, wherein the actuator pushes and pulls on separate or different sides of the same tab to move the valve slide in different directions inside the valve cylinder. It should be appreciated that while the actuator surfaces are rectangular shapes as illustrated, other shapes, e.g., square, trapezoidal, etc., are contemplated in other embodiments.  
         [0054]      FIG. 3F  and  FIG. 3G  represent the same air valve in two different positions. The valve slide  510  (shown in full view) fits snugly inside the valve cylinder  502  so that the O-rings seal the cavities formed by the cylinder wall and the valve slide. The valve slide has two resting positions, the pressure position  520  shown in  FIG. 3B  and the vacuum position  521  shown in  FIG. 3F . The air pump  50  is turned on only when the valves are in one of these two positions. The air pump is off while the valves are moved. Referring to  FIG. 3G , when the valve slide is in the pressure position  520 , O-ring  511  seals the vacuum cavity and the valve cylinder from the air tube. The cavity formed between O-ring  511  and O-ring  512  connects the pressure cavity to the air tube so pressurized air will flow through the air tube to inflate the bladder. O-ring  512  seals the valve cylinder from the outside air. Referring to  FIG. 3F , when the valve slide is in the vacuum position  521 , the vacuum cavity is connected to the air tube and O-ring  511  seals the vacuum cavity from the pressure cavity. The bladder is deflated as air flows through the air tube towards the vacuum created by the air pump. O-ring  511  and O-ring  512  seal the pressure cavity from the air tube and outside air. The valve slide is moved to either the pressure position  520  or the vacuum position  521  by a servo that engages the push and pull tabs  525  and  526 .  
         [0055]     In one embodiment of the invention, valve slide  510  comprises rails  530  under the left and right edges of the platform formed by valve slide  510 . A bump  527  is provided on each rail that mates with a correspondingly shaped detent  529  in the pressure position  520  or detent  528  in the vacuum position  521 . In one embodiment, the bump  527  is formed at the end of rail  530  directly beneath pull tab  526 . The bump causes the valve slide to remain seated in either pressure position  520  or vacuum position  521 . The seating of the bump into the detents acts to lock the valve slide in position while air pump  50  is turned on and pressurized air flows through the air tube to either inflate or deflate the bladder. It is appreciated that the bump may be formed anywhere along rail  530 , as long as it mates with a corresponding detent in valve constraint  513  when in the pressure and vacuum positions. Moreover, it is appreciated that one or more bumps may be positioned on the constraint  513 , and corresponding detents notched in rail  530 , to seat and lock the valve slide in position, in one embodiment of the invention.  
         [0056]      FIG. 3J  shows an end view of a valve slide as positioned when in a valve cylinder. The valve tabs and valve slide rails  530  are constrained from rotating about the valve cylinder axis by a slot  516  in the valve guide plate, or valve constraint,  513 . The valve constraint has a slot  516  for each valve slide. By virtue of valve slide comprising a platform and rails  530  on each longitudinal edge of the platform, the valve slide is constrained from rotating, shifting, or bending about the valve cylinder axis. Rails  530  act as guides within slot  516  to further prevent valve slide  510  from rotating, bending or shifting about the valve cylinder axis as the valve slide is moved inside the valve cylinder. In this manner, the valve slide moves in only one dimension inside valve cylinder.  
         [0057]      FIG. 4G  is a cross-section view through the axis of the valve cylinders of valve block  601  and valve block  602  positioned so that the valve slides  510  (shown in full view) are interleaved, in accordance with one embodiment of the invention. Interleaving minimizes the spacing between valve slides and aligns the valve push and pull tabs  525 ,  526  so the valve servo can move the valve slides in valve blocks  601  and  602 . Some of the valve slides are shown in the pressure position and the others are shown in the vacuum position. The valve constraint  513  has  24  slots  516  that engage the  24  valve slide plates to prevent rotation of the valve slides about the valve cylinder axis. The slots  516  in block  601  are offset from the slots in block  602  to limit the travel of valve slides  510  such that, for example, the valve slides in block  601  are prevented by the constraints in block  602  from moving outside of valve cylinders in block  601 . Likewise, constraints in block  601  prevent valve slides in block  602  from moving outside the valve cylinders in block  602 . The ends of the valve blocks  601  and  602  have passageways from the pressure and vacuum cavities to the air-feed tee  603 .  
         [0058]      FIG. 5  is a perspective drawing of the valve servo  700 . The servo carriage  701  is made of injection molded plastic. The servo carriage is supported by the position threaded rod  702  and the slide rod  703 . In the preferred embodiment, the position threaded rod is ⅜″ in diameter and has 16 threads per inch. The servo carriage has a position threaded bearing  704  that engages the position threaded rod. The position threaded bearing may be a threaded hole machined in the valve carriage plastic, or may be a threaded metal cylinder press fit into a hole in the servo carriage. The fit between the position threaded rod and the position threaded bearing is loose so there is minimum friction as the threaded rod rotates to move the servo carriage. The interface between the threaded rod and the threaded bearing provides support and constraint for the servo carriage for all directions except rotation about the axis of the threaded rod. Rotation constraint is provided by the smooth slide rod  703  that engages the carriage guide  705 . The fit between the slide rod and the carriage guide is loose so there is minimum friction as the carriage is moved by rotation of the position threaded rod.  
         [0059]     The servo carriage has a bearing post  710  and a bearing plate  711  that support the two valve bearings  712 . The valve bearings are press fit into holes molded in the bearing post and bearing plate. The valve threaded rod  713  is a standard #8 sized screw with 32 threads per inch. The ends of the valve threaded rod are machined to fit the valve bearings so the rod can rotate with minimum friction and constrained so it can not move in any other way. The valve drive spur gear  714  is approximately 1″ in diameter and is fastened to the end of the valve threaded rod.  
         [0060]     The valve motor  720  is mounted on the bearing plate  711  by two screws  721  (one screw  721  is hidden by spur gear  714 ) that pass through the bearing plate into the end of the motor. The valve motor spur gear  722  is approximately 3/16″ in diameter and is fastened to the shaft of the valve motor. The valve motor is positioned so that the valve motor spur gear engages the valve drive spur gear. The valve motor operates on 5 volts DC using approximately 0.3 A. It rotates CW or CCW depending on the direction of current flow. The control processor  60  has an interface circuit that enables it to drive the valve motor CW or CCW at full power. The control is binary on or off. The valve motor, valve motor spur gear, and valve drive spur gear are chosen so that the valve threaded rod rotates approximately 1000 RPM when the valve motor is driven.  
         [0061]     The servo slider  730  has a slider threaded bearing  731  that engages the valve threaded rod  713 . The servo slider is supported by the valve threaded rod and is constrained by the threaded rod in all directions except rotation about the axis of the threaded rod. The servo slider passes through the slider slot  732  in the servo carriage. The slider slot constrains the servo slider so that as the valve threaded rod rotates, the servo slider can only move parallel to the axis of the slot and the axis of the valve threaded rod. The fit between the servo slider and the slider slot is loose to minimize friction as the slider moves.  
         [0062]     The bearing post  710  and bearing plate  711  also support the valve PCB (printed circuit board)  740 . The valve PCB connects to a 6-conductor flat flexible cable  706  that connects to the interface circuit of the control processor  60 . Two wires from the valve motor connect to PCB  740  and to two conductors in the flexible cable. The valve PCB supports the A-photo-interrupter  741  and the B-photo-interrupter  742 . The photo-interrupters are positioned so that A-slider tab  743  and B-slider tab  744  on the servo slider  730  pass through the photo-interrupters as the servo slider is moved by the valve motor and valve threaded rod. The photo-interrupters generate binary digital signals that encode three positions of the servo slider. These digital signals are connected to the control processor through the flexible cable and are used by the control processor when driving the valve motor to position the servo slider.  
         [0063]      FIG. 6  shows three views of the valve servo positioned over the valve blocks.  FIG. 6A  shows the valve blocks  601  and  602  in cross-section with the valve servo  700  positioned over one of the valve slides  510  in valve block  602 . The position of the valve servo is established by the position threaded rod  702 , position threaded rod bearing  704 , slide rod  703 , and carriage guide  705 . The servo slider  730  is shown in the center position  800 . A-slider finger  810  and B-slider finger  811  have about 1/16″ clearance from any of the valve levers  514  in either the pressure position  520  or the vacuum position  521 . Both valve sliders are shown in the vacuum position. The A-photo-interrupter  741  and the B-photo-interrupter  742  are positioned so that neither the A-slider tab  743  nor the B-slider tab  744  interrupt the light path in the photo-interrupters when the servo slider is in the center position  800 . This is the only position where both photo-interrupters are uninterrupted.  
         [0064]      FIG. 6B  shows the servo slider in the B-position  801  corresponding to the pressure position  520  of the valve slide. In this position, the B-slider tab  744  interrupts the A-photo-interrupter  741  while the light path of the B-photo-interrupter is uninterrupted. When moving from the center position  800  to the B-position, both photo-interrupters are interrupted by the B-slider tab. To move the valve to the B-position, the control processor drives the valve motor until the light path of the B-photo-interrupter is uninterrupted. To return to the center position  800 , the valve motor direction is reversed and driven until both photo-interrupters are uninterrupted.  
         [0065]      FIG. 6C  shows the servo slider in the A-position  802  corresponding to the vacuum position  521  of the valve slide. In this position, the A-slider tab  743  interrupts the B-photo-interrupter  742  while the light path of the A-photo-interrupter  741  is uninterrupted. When moving from the center position  800  to the A-position, both photo-interrupters are interrupted by the A-slider tab. To move the valve to the A-position, the control processor drives the valve motor until the light path of the A-photo-interrupter is uninterrupted. To return to the center position  800 , the motor direction is reversed and driven until both photo-interrupters are uninterrupted.  
         [0066]     When the control processor begins operation, the position of the valve servo is unknown, and must be initialized. The valve servo is initialized first by testing the signals from the A- and B-photo-interrupters. If both are uninterrupted, then the valve servo is in the center position  800  and properly initialized. Any other combination of signals from the photo-interrupters represents one of two possible positions.  
         [0067]     If both photo-interrupters are interrupted, then either the A-slider tab  743  or the B-slider tab  744  is interrupting the light paths. For this case, the servo slider is driven towards the B-position  801  until the B-photo-interrupter becomes uninterrupted. The servo slider either is in the B-position or is just right of the center position. After a pause for the valve motor to come to a stop, the servo slider is driven towards the B-position again. If the A-photo-interrupter becomes uninterrupted within a short time, the servo slider is in the center position, and the valve servo is initialized. If the A-photo-interrupter remains interrupted, then the servo slider is jammed in the B-position and must be driven towards the A-position until both photo-interrupters are uninterrupted.  
         [0068]     If initially only the A-photo-interrupter is interrupted, then the servo slider either is in the B-position  801  or is slightly right of the center position. The servo slider is driven towards the B-position and if the A-photo-interrupter becomes uninterrupted within a short time, the servo slider is in the center position, and the valve servo is initialized. If the A-photo-interrupter remains interrupted, then the servo slider is jammed in the B-position and must be driven towards the A-position until both photo-interrupters are uninterrupted.  
         [0069]     If initially only the B-photo-interrupter is interrupted, then the servo slider either is in the A-position  802  or is slightly left of the center position. The servo slider is driven towards the A-position and if the B-photo-interrupter becomes uninterrupted within a short time, the servo slider is in the center position, and the valve servo is initialized. If the B-photo-interrupter remains interrupted, then the servo slider is jammed in the A-position and must be driven towards the B-position until both photo-interrupters are uninterrupted.  
         [0070]      FIG. 7  is a perspective drawing of the position servo  900  assembled with valve block  601  and valve block  602 . The position bearings  904  and  905  are press fit into holes in the motor bracket  902  and bearing bracket  903 . The position threaded rod  702  is machined to fit in the bearings and to constrain the threaded rod so that the only possible movement is rotation. The threaded rod is also machined so that the rotation cam  907  can be fastened to the end that protrudes beyond position bearing  905  and so that the position spur gear  906  can be fastened to the end that protrudes beyond position bearing  904 . The slide rod  703  is press fit into holes in the motor bracket and the bearing bracket. The bearing holes and the slide rod holes are positioned so that the position threaded rod and the slide rod are parallel to each other and to the valve blocks. The position threaded bearing  704  of the valve servo  700  engages the position threaded rod and the carriage guide  705  engages the slide rod  703 . The position motor  910  is attached with two screws  912  to the motor plate  911 , which is injection molded as part of the motor bracket  902 . The position motor is positioned so that the position worm gear  913  engages the position spur gear  906 .  
         [0071]     Motor bracket  902  is attached to the valve block using screws. The motor bracket has molded spacers in line with the screw holes so that when attached, the motor bracket is perpendicular to the valve blocks and spaced so that the servo slider can be positioned over the air valve closest to the motor bracket. Likewise bearing bracket  903  is attached to the valve blocks using screws  921 . The bearing bracket has molded spacers in line with the screw holes so that when attached, the bearing bracket is perpendicular to the valve blocks and spaced so that the servo slider can be positioned over the air valve closest to the bearing bracket. The bearing bracket has a cutout at the bottom center so that the pressure air tube  51  and the vacuum air tube  52  can be attached to the air-feed tee  603 . The combination of the motor bracket, bearing bracket, and valve bank  601  and  602  connected together with screws form a rigid structure that is mounted as a single unit.  
         [0072]     The position motor operates on 5 volts DC using approximately 0.5A. It rotates CW or CCW depending on the direction of current flow. The control processor  60  has an interface circuit that enables it to drive the position motor CW or CCW at full power. The control is binary on or off. The EOT (end of travel) photo-interrupter  930  is mounted on the bearing bracket  903  so that the carriage guide  705  interrupts the light path when the valve servo is positioned over the valve slide  510  closest to the bearing bracket. The binary digital signal from the EOT photo-interrupter is interfaced to control processor  60 . The rotation photo-interrupter  931  is mounted on the bearing bracket  903  and is positioned so that the rotation cam  907  interrupts the light path about 50% of the time as the position threaded rod rotates. For ½ of a rotation, the light path is interrupted and is uninterrupted for the other part of a rotation. The binary digital signal from the rotation photo-interrupter is interfaced to the control processor.  
         [0073]     When the control processor begins operation, the position of the valve servo carriage is unknown and must be initialized. If the EOT photo-interrupter is uninterrupted, the position servo is driven to move the valve servo carriage towards the bearing bracket until the EOT photo-interrupter&#39;s light path is interrupted by the carriage guide. The EOT photo-interrupter is positioned so that when the position motor stops, the servo slider  730  is positioned over the valve slide closest to the bearing bracket. If the EOT photo-interrupter is initially interrupted, the exact position of the valve servo carriage is not known. Therefore, the position servo is driven to move the valve servo away from the bearing bracket until the EOT photo-interrupter is uninterrupted. Then the position servo is driven to move the valve servo towards the bearing bracket until the EOT photo-interrupter is interrupted, just as if the EOT photo-interrupter was initially uninterrupted.  
         [0074]     After the valve and position servos are initially positioned, the control processor can set the air valves by controlling the position and valve motors. Beginning with the air valve closest to the bearing bracket, the control processor moves the servo slider to either the A-position or the B-position to set the valve slider to the pressure position or the vacuum position. Then the servo slider is returned to the center position. Then the position servo is driven to move the valve servo so it is positioned over the second air valve. The position threaded rod has 16 threads per inch and the valve slides are spaced ¼″ center to center. Therefore, four revolutions of the threaded rod move the valve servo a distance equal to the distance between adjacent valve slides. The control processor monitors the rotation photo-interrupter  931  while the position threaded rod rotates, counting the number of transitions from interrupted to uninterrupted. After four such transitions, the position motor is stopped. Then the valve servo is driven to set the next valve, and after returning to the center position, the position motor drives the position threaded rod for four more revolutions. This cycle is repeated until all 24 valves are set. The preferred embodiment of the servo controlled valves requires less then one minute to set the positions of all 24 air valves.  
         [0075]     After twenty-four air valves are set, the valve servo is positioned over the air valve closest to the motor bracket. The next time the valves are set, the position servo moves the valve servo toward the bearing bracket. The valve servo position is re-initialized by using the EOT photo-interrupter to set the position for the air valve closest to the bearing bracket. This ensures any errors in counting rotations are corrected every other cycle of setting air valves.  
         [0076]     Air Pump and Relief Valves  
         [0077]      FIG. 8  is a perspective view of the air pump enclosure  50  and its mounting system. The air pump  1020  has a vibrating armature that oscillates at the 60 Hz power line frequency. The preferred embodiment uses pump model  6025  from Thomas Pumps, Sheboygan, Wis. It produces noise that could be objectionable in some installations. The air pump is attached to the enclosure base  50 A by four shock absorbing mounting posts  1010 . The enclosure base is further isolated by using shock absorbing wall mounts  1011 . The enclosure base and enclosure cover  50 B are made of sound absorbing plastic to further isolate the noise. The enclosure cover has multiple small ventilation slots  1012 .  
         [0078]     The pump PCB (printed circuit board)  1001  and the 5V DC power supply  1002  are fastened to the enclosure base  50 A. The pump PCB has a standard optically isolated triac circuit that uses a 5V binary signal from the control processor  60  to control the 110V AC power to the air pump. The pump PCB also has terminals to connect the 110V AC power cord  54 , the AC supply to 5V power supply  1003 , the 5V power from the supply  1004 , and the controlled AC supply to the air pump  1005 . The 3-conductor power and control cable  55  connects to the pump PCB by connector  1006 .  
         [0079]     The pressure and vacuum produced by the air pump are unregulated. A pair of diaphragm relief valves  1000  made from injected molded plastic are use to limit the pressure and vacuum to about 1 psi. The relief valves are connected to the air pump by flexible air tubes  1007  to provide noise isolation. The relief valves connect to the pressure air tube  51  and the vacuum air tube  52 .  
         [0080]      FIG. 9  shows several views of the relief valves  1000 .  FIG. 9A  is a cross-section view through the section line shown in  FIG. 9C . The main valve structure  1100  is a cylinder made of injection molded plastic. A plate  1101  divides the cylinder into a pressure cavity  1102  and a vacuum cavity  1103 . The vacuum feed tube  1104  passes through pressure cavity and an air passage  1106  connects it to the vacuum cavity. Likewise, the pressure feed tube  1105  passes through the vacuum cavity and an air passage  1107  connects it to the pressure cavity. This arrangement enables the pressure feed tube  1105  and the vacuum feed tube  1104  to connect to the ports of the air pump with short and straight tubes.  
         [0081]     Referring to  FIG. 9A , a thin plastic diaphragm  1110  is glued to the rim of the relief valve structure  1100 . The diaphragm has a hole in the center that is covered by the pressure plug  1111 . As pressure increases in the pressure cavity  1102 , the diaphragm is pushed away from the plug and air leaks from the pressure cavity. The leak increases as the pressure increases so the pressure is regulated. A threaded stud  1112  is mounted in the center of the divider  1101 , and the pressure plug is threaded to match the stud. Turning the pressure plug CW or CCW decreases or increases the force between the plug and the diaphragm, thus adjusting the relief pressure. A thin plastic diaphragm  1120  is glued to the rim of the relief valve structure  1100 . The diaphragm has a hole in the center that is covered by the vacuum plug  1121 . As vacuum increases in the vacuum cavity  1103 , the diaphragm is pulled away from the plug and air leaks into the vacuum cavity. The leak increases as the vacuum increases so the vacuum is regulated. A threaded stud  1112  is mounted in the center of the divider  1101 , and the vacuum plug is threaded to match the stud. Turning the vacuum plug CW or CCW increases or decreases the force between the plug and the diaphragm, thus adjusting the relief pressure.  FIG. 9B  is a full end view of the cross-section view shown in  FIG. 9A .  
         [0082]      FIG. 9C  is a bottom view of the relief valves. The pressure air tube  51  connects to the pressure air feed  1105 B and the pressure air feed  1105 A connects to a flexible air tube  1007  that in turn connects to the pressure output of the air pump  1020 . The vacuum air tube  52  connects to the vacuum feed tube  1104 B and the vacuum feed tube  1104 A connects to a second flexible air tube  1007  that in turn connects to the vacuum input of the air pump.  
         [0083]      FIG. 9D  is a cross-section view through the section line shown in  FIG. 9B  of the pressure cavity  1102 . Air passage  1107  connects the pressure feed tube  1105  to the cavity. Air passage  1106  connects the vacuum feed tube  1104  to the vacuum cavity  1103 .  
         [0084]     System Installed on Plenum  
         [0085]      FIG. 10  is an exploded perspective view of the system components that are mounted on the conditioned air plenum  15 . The control processor  60  and interface circuits are built on a PCB (printed circuit board)  1700  approximately 5″×5″, which is mounted to the main enclosure base  1701 . The PCB includes the terminals and sockets used to connect the control processor signals to the servo controlled air valves  40 , the power and control connection  55 , the temperature sensor  61 , the pressure sensor  62 , the radio receiver connection  72 , the existing thermostat connection  73 , the existing HVAC controller connection  74 , the IrDA link connection  82 , the RS232 connection  1551 , and the remote connection  1550 . Side  1703  of the main enclosure base  1701  has access cutouts and restraining cable clamps  1702  for the power and control connection  55 , the radio connection  72 , the existing thermostat connection  73 , the existing HVAC controller connection  74 , the RS232 connection  1551 , and the remote connection  1550  (when used).  
         [0086]     The main enclosure base  1701  has a cutout sized and positioned to provide clearance for the valve header  504  on the valve block  601  and valve block  602 . The servo controlled air valve  40  as shown in  FIG. 7  is mounted to the main enclosure base  1701 . The main enclosure base also has cutouts for the pressure and temperature sensors to access the inside of the plenum and for the link connection  82  to pass from the plenum to its connector on the PCB  1700 . The PCB is mounted above the air valve blocks. Side  1703  also has cutouts for the pressure air tube  51  and vacuum air tube  52  connected to the air-feed tee.  
         [0087]     The main enclosure top  1710  fits to the base  1701  to form a complete enclosure. Vent slots  1711  in the main enclosure top provide ventilation. A cutout  1712  in the main enclosure top matches the location of switch  1405  on PCB  1700  so that when the main enclosure top is in position, the switch  1405  can be manually switched to either position.  
         [0088]     To install the present invention, a hole  1720  approximately 16″×16″ is cut in the side of the conditioned air plenum  15 . The hole provides access for the process used to pull the air tubes  32  and to provide access when attaching the air tubes. The material removed to form the hole is made into a cover  1730  for the hole by attaching framing straps  1722 ,  1723 ,  1724 , and  1725  to  1730 . The framing straps are made from 20-gauge sheet metal approximately 2″ wide. The mounting straps have mounting holes  1726  approximately every 4″ and ¼″ from each edge and have a thin layer of gasket material  1727  attached to one side. The straps are cut to length from a continuous roll, bent flat, and attached to the hole-material using sheet metal screws  1728  through the holes along the inside edge of the framing straps so that the framing straps extend approximately 1″ beyond all edges of the hole-material. For clarity, only the screws used with framing strap  1722  are shown.  
         [0089]     A rectangular hole is cut in the cover  1730  and is sized and positioned to match the cutouts in the bottom of the main enclosure base  1701  that provide clearance for the air valve headers and clearance for the pressure and temperature sensors and the link connection. The main enclosure base is fastened to the cover. After all connections from inside the plenum are made, the cover is attached to plenum using sheet metal screws through the holes along the outer edge of the framing straps. The gasket material on the mounting straps seals the mounting straps to the plenum and the cover  1730 . When a bypass  90  is installed, it is often convenient to connect the bypass duct to the conditioned air plenum  15  through a hole  1731  in the cover  1730 .  
         [0090]      FIG. 11  illustrates another embodiment of a valve block manifold  200  which is especially suitable for injection molded plastic manufacturing. The manifold includes a plurality of parallel valve cylinders  201  each including a bore  202 . The valve cylinders form a substantially air-tight floor of the manifold. The manifold further includes vertical exterior walls  203  which are coupled to the floor.  
         [0091]     A row of air tube connector cylinders  204  are coupled to respective ones of the valve cylinders, each including a bore  205  which is in communication with the bore of its corresponding valve cylinder. The air tube connector cylinders, together with a vertical interior wall  206 , divide the interior of the manifold into first and second separate manifold chambers  207 ,  208 . In some embodiments, the air tube connector cylinders extend slightly higher than the exterior and interior walls (obscuring the segments of the interior wall which are between adjacent pairs of air tube connector cylinders in the view illustrated).  
         [0092]     First and second manifold connector cylinders  209 ,  210  are coupled to the exterior wall and include bores  211 ,  212  coupled through the exterior wall into communication with the first and second manifold chambers, respectively. The manifold connector cylinders are used to couple two manifolds into a manifold pair (not shown).  
         [0093]     The manifold further includes first and second air supply connectors  213 ,  214  coupled to the exterior wall and having bores (not shown, and  215 , respectively) extending into the first and second manifold chambers, respectively. The valve cylinders include first and second vent holes  216 ,  217  coupling their valve bores (and, more to the point, their respective air tube connector cylinders) to the first and second manifold chambers, respectively. Finally, the manifold may optionally include holes  218  or other suitable means for attaching a manifold cover (not shown).  
         [0094]      FIG. 12  illustrates the manifold  200  with a cutaway for viewing the airflow communication between the valve bore  202 , air tube connector bore  205 , first manifold chamber vent  216 , first manifold chamber  207 , second manifold chamber vent  217 , and second manifold chamber  208 .  
         [0095]      FIG. 13  illustrates one embodiment of a manifold cover  220  such as may be used with the manifold of  FIG. 11 . The manifold cover includes holes  221  which mate with the air tube connector cylinders ( 204  of  FIG. 11 ). In embodiments in which the manifold of  FIG. 11  has air tube connector cylinders which extend higher than the interior and exterior walls, the holes  221  are sized to mate with the outer diameters of the air tube connector cylinders.  
         [0096]      FIG. 14  illustrates a manifold assembly  225  including a manifold  200  coupled in a substantially air-tight manner with a manifold cover  220 . The bores  205  of the air tube connectors are exposed. As illustrated, the air tube connector cylinders  204  may also extend through the holes in the manifold cover. Although a variety of sealing mechanisms may be employed, such as gaskets, in one embodiment the manifold cover is simply glued to the manifold at all contact points, such as the exterior walls, interior divider wall, and air tube connector cylinders. In another embodiment, the manifold cover is manufactured with adhesive tape around its edges. A non-stick covering initially protects the adhesive. When mating the manifold cover to the manifold, the non-stick covering is removed and the adhesive tape is pressed around the edges of the manifold and adhered to its exterior walls. In some embodiments, it may be desirable to provide a more secure retention by screwing the manifold cover to the manifold with screws (not shown) placed in the holes  222 .  
         [0097]      FIG. 15  illustrates one embodiment of a valve plunger  230  such as may be used in conjunction with the manifold assembly of  FIG. 14 . The plunger includes a shaft  231  which is equipped with first and second seal such as o-rings  232 ,  233 . In most embodiments (those in which a single-diameter valve cylinder bore ( 202  in  FIG. 11 ) is employed), the outer diameter of the shaft will be less than the outer diameter of the seals.  
         [0098]     The plunger further includes first and second actuator surfaces  234 ,  235  against which an actuator (not shown) can press to respectively insert and withdraw the valve plunger in the manifold.  
         [0099]      FIGS. 16 and 17  illustrate another embodiment of a pressure relief valve  240  such as may be employed with the manifold system, and which is easily and cheaply manufactured mainly using off-the-shelf components. The pressure relief valve is built upon a standard plastic T fitting  241  used for coupling plastic tubing to threaded pipe. The T fitting has coaxial barbed connectors  242 ,  243  and a perpendicular male threaded connector  244 . The bore  245  of the barbed connectors is in communication with the bore  246  of the threaded connector. The T fitting may optionally be modified by cutting or otherwise forming a suitably shaped seat  247  at the terminal end of the bore  246  to form an improved airtight fit with a check ball  248  which is larger than the bore  246 . In another embodiment, an o-ring is positioned to form an airtight seal with a check ball.  
         [0100]     A female threaded pipe cap fitting  249  is modified with one or more vent holes  250  which are, after the cap is threaded onto the T fitting, in airflow communication with the bore  246 . A spring  251  holds the check ball against the seat  247  under sufficient force to provide the desired pressure relief setting. This setting is grossly determined by the strength of the spring, and can be finely adjusted according to how far the cap is screwed onto the T fitting. In some embodiments, the cap end of the spring may be positively located by a screw or bolt  252  extending through the bottom of the cap. In some embodiments, the ball end of the spring may be positively located by an axial bore extending part way into the check ball. Alternatively, the ball end of the spring may be embedded directly in the check ball during manufacturing of the check ball. In another embodiment, an adhesive is used to attach the spring to the check ball and/or to the bottom of the cap. The check ball is not necessarily spherical in all embodiments.  
         [0101]     In operation, if the air pressure within the bore  246  becomes too great, the check ball will be forced away from the seat, and air will escape out the holes  250 .  
         [0102]      FIGS. 18 and 19  illustrate another embodiment of a vacuum relief valve  260  which is easily and cheaply made mostly from off-the-shelf components. The vacuum relief valve is built upon a plastic T fitting  261  such as is commonly used to connect plastic tubing to threaded pipe. The T fitting includes coaxial barbed connectors  262 ,  263  and a perpendicular female threaded connector  264 . The bore  265  of the coaxial connectors is in airflow communication with the bore  266  of the perpendicular connector.  
         [0103]     A commercially available plastic air compressor filter  267  includes a male threaded connector  268  which is screwed into the T fitting such that a bore  269  of the filter is in airflow communication with the bore  266 . The filter includes a removable cap  270  which is provided with holes  271  which are in airflow communication through a foam filter element  272  to the bore  269 . The filter includes stand-offs  273  originally intended to prevent the filter from coming into direct contact with the bore  269  (which would tend to force all flow through a relatively small volume of the filter immediately adjacent the bore, increasing the filter&#39;s flow resistance and reducing the time required between cleanings). The filter is modified with the addition of an insert  275  that divides the air filter cavity into two volumes, and supports an o-ring  277 . A check ball  274  is held against the o-ring by a spring  276 . In some embodiments, the cost of the insert can be reduced by providing it with a smooth surface against which the check ball mates, eliminating the need for an o-ring. In some embodiments, the original foam filter element is replaced by a filter element made from thinner material, so the filter element does not interfere with the check ball.  
         [0104]     In operation, if the vacuum within the bore becomes to strong, the external ambient pressure will force the check ball away from the seal, and air will flow into the bore  269 .  
         [0105]     In single-manifold embodiments, L fittings or even straight fittings, rather than T fittings, can be used in constructing the pressure and vacuum relief valves.  
         [0106]      FIGS. 20 and 21  illustrate the components of  FIGS. 11-19  assembled into a valve manifold assembly  280 . The assembly includes a pair of manifold assemblies  225 L,  225 R. The left manifold assembly  225 L is substantially as shown in  FIG. 14 , while the right manifold assembly  225 R is another unit of the same assembly, rotated 180° about an axis extending generally out of the page. The first manifold connector  209 L of the left manifold is coupled by the T fitting  241  of the pressure relief valve  240  to the second manifold connector  210 R of the right manifold. Because of the 180° rotation of the right manifold assembly, the second manifold connector provides airflow communication between the first manifold chamber ( 207  in  FIG. 11 ) of the left manifold assembly  225 L and the second manifold chamber ( 208  in  FIG. 11 ) of the right manifold assembly  225 R. Thus, the “left” manifold chambers are connected together into one large pressure chamber spanning both manifold assemblies. Similarly, the second manifold connector  210 L of the left manifold is coupled by the T fitting  261  of the vacuum relief valve  260  to the first manifold connector  209 R of the right manifold, providing airflow communication between the second manifold chamber of the left manifold assembly and the first manifold chamber of the right manifold assembly. Thus, the “right” manifold chambers are connected together into one large vacuum chamber spanning both manifold assemblies.  
         [0107]     Pressure is applied by the pump (not shown) to the “left” pressure chamber via connector  214 L. Air flows from the connector  214 L directly into the first manifold chamber ( 207 ) of the left manifold assembly, and through the pressure relief valve&#39;s T fitting  241  into the second manifold chamber ( 208 ) of the right manifold assembly.  
         [0108]     Vacuum is applied by the pump to the “right” vacuum chamber via connector  213 R. Air flows from the second manifold chamber ( 208 ) of the left manifold assembly, through the vacuum relief valve&#39;s T fitting  261  into the first manifold chamber ( 207 ) of the right manifold assembly, and out the connector  213 R.  
         [0109]     When a plunger in the left manifold assembly is in its leftmost, “IN” position, the air tube connector  205 L is in airflow communication with the second manifold chamber ( 208 ) of the left manifold assembly—the “left” chamber—and vacuum is applied to the air tube connector. When a plunger in the left manifold assembly is in its rightmost, “OUT” position, the air tube connector is in airflow communication with the first manifold chamber ( 207 ), and pressure is applied to the air tube connector.  
         [0110]     Likewise, when a plunger in the right manifold assembly is in its rightmost, “IN” position, the air tube connector  205 R is in airflow communication with the first manifold chamber ( 207 ) of the right manifold assembly—the “left” chamber”—and vacuum is applied to the air tube connector. When a plunger in the right manifold assembly is in its leftmost, “OUT” position, the air tube connector is in airflow communication with the second manifold chamber ( 208 ), and pressure is applied to the air tube connector.  
         [0111]     Thus, the plunger positions can be characterized as: “left” provides vacuum, and “right” provides pressure. (Because the right manifold assembly is 180° rotated, it cannot be said that “in” nor “out” has a consistent meaning.)  
         [0112]     In one embodiment, as shown, the other two connectors (which would be  213  of the left manifold and  214  of the right manifold, if shown) may be removed, as they are not needed. In some such embodiments, their bore holes are then plugged; in other such embodiments, the bore holes are not formed at manufacturing time, and are formed for the connectors  214 L and  213 R at assembly time, avoiding the necessity of plugging any holes.  
         [0113]     In one embodiment, the T fittings of the relief valves are press fit into the manifold connector cylinders without the use of adhesives or other fastening methods. The press fit between the T fitting barbs and the insides of the cylinders provides a sufficiently airtight coupling, maintains proper spacing between the left and right manifold assemblies, and mechanically secures the components together as a single unit. In other embodiments, it may be desirable to use other fastening means.  
         [0114]      FIG. 22  illustrates, in cross-section view with various components removed for clarity, another embodiment of the valve actuator system  300  suitable for use with the valve manifold. Relative to  FIG. 20 , the assembly has been rotated 180 degrees about a longitudinal centerline (running generally from the top of the page to the bottom) and cut away such that only an uppermost valve assembly is visible (the top left valve in  FIG. 20 ). Note that, while  FIG. 20  illustrates the “back” side of the manifold assembly, or the side which is placed adjacent the plenum (not shown) to receive the air tubes which extend from the bladders (not shown),  FIG. 21  illustrates the “top” side of the manifold assembly.  
         [0115]     The manifold assembly includes a valve plunger  230  riding in a valve cylinder bore  202 . An outer edge  811 -O of a slider finger  811  of a servo slider  730  pushes on the first actuator surface  234  of the plunger until the first seal  232  is between the bore  205  and the vent  216 . This is the “IN” position. In this position, the bore  205  is in airflow communication (around the shaft of the plunger) with the vent  217 , coupling the air tube  32  to the “right” manifold chamber (remember that  FIG. 21  is flipped with respect to  FIG. 20 ) which will be placed under vacuum once all the plungers are in their correct positions. In this position, the first seal  232  also prevents airflow communication from the “left” manifold chamber via vent  216  both to the bore  205  and to the vent  217 .  
         [0116]      FIG. 23  illustrates, in cross-section, the inner edge  811 -I of the slider finger pushing on the second actuator surface  235  of the plunger  230  until the seal  232  is between the bore  205  and the vent  217 . This is the “OUT” position. In this position, the bore  205  is in airflow communication with the vent  216 , coupling the air tube  32  to the “left” manifold chamber which will be placed under pressure once all the plungers are in their correct positions. In this position, the seal  232  also prevents airflow communication from the “right” manifold chamber via vent  217  both to the bore  205  and to the vent  216 .  
         [0117]      FIG. 24  illustrates, in cross-section view with various components removed for clarity, another embodiment of the valve actuator system  300  suitable for use with the valve manifold. The manifold assembly includes a valve plunger  230  according to the embodiment described above and as illustrated in  FIGS. 3F-3J , riding in a valve cylinder bore  202 . An outer edge  811 -O of a slider finger  811  of a servo slider  730  pushes on the first actuator surface  234  of the plunger until the first seal  232  is between the bore  205  and the vent  216 . This is the “IN” position. In this position, the bore  205  is in airflow communication (around the shaft of the plunger) with the vent  217 , coupling the air tube  32  to the “right” manifold chamber which will be placed under vacuum once all the plungers are in their correct positions. In this position, the first seal  232  also prevents airflow communication from the “left” manifold chamber via vent  216  both to the bore  205  and to the vent  217 .  
         [0118]      FIG. 25  illustrates, in cross-section, the inner edge  811 -I of the slider finger pushing on the second actuator surface  235  of the plunger  230  until the seal  232  is between the bore  205  and the vent  217 . This is the “OUT” position. In this position, the bore  205  is in airflow communication with the vent  216 , coupling the air tube  32  to the “left” manifold chamber which will be placed under pressure once all the plungers are in their correct positions. In this position, the seal  232  also prevents airflow communication from the “right” manifold chamber via vent  217  both to the bore  205  and to the vent  216 .  
         [0119]     As described above, while the illustrated embodiment uses separate actuator surfaces  234 ,  235 , it is appreciated that a single actuator surface may be used in which the slider finger  811  of server slider  730  make contact with and pushes on different sides of the actuator surface to move the plunger to the IN or OUT position.  
         [0120]     Note that in the embodiment illustrated in  FIGS. 24 and 25 , the valve slide depicted in  FIGS. 3F-3J  is used. In this embodiment of the valve slide, the actuator surfaces  234  and  235  are square or rectangular dimension, as opposed to circular in dimension, as in the valve slide depicted in  FIG. 15 . The valve slide utilizing the rectangular actuator surface is advantageous, as when slide finger  811  of servo slider  730  makes offset contact with actuator surface  234  or  235 . Using the valve slide depicted in  FIG. 15 , the slide finger may make contact with an actuator surface at other than the center of the actuator surface which places offset forces on the valve slide, or may even cause the slide finger of server slider  730  to slip or slide past the actuator surface, causing a malfunction.  
       CONCLUSION  
       [0121]     While the invention has been described with reference to air pressure and vacuum, the skilled reader will readily appreciate that it may be adapted for use with other fluids such as water or hydraulic fluid. And while the invention has been described with respect to pressure and vacuum, the skilled reader will readily appreciate that it may be adapted for use with two different pressure levels, or two different vacuum levels. And while the invention has been described with reference to the same ambient—air—being provided under pressure and vacuum, two different fluid flows could be controlled with the two separate manifold chambers, such as air vacuum and water pressure, or salt water and fresh water, or Coke and Pepsi, or what have you. Furthermore, although the invention has been described with reference to embodiments which are suitable for use in relatively low pressure and low vacuum applications, such as the meager 1 psi or so believed necessary for operating pneumatic bladders, it could readily be practiced in much higher pressure environments and constructed of much higher strength materials than e.g. injection molded plastic.  
         [0122]     Although the valve system has been described as providing selective connection to one of two manifolds, it could be enhanced for use with three or more manifolds, albeit at the cost of a perhaps significantly increased manufacturing complexity for both the manifold and valve plunger components.  
         [0123]     When one component is said to be “adjacent” another component, it should not be interpreted to mean that there is absolutely nothing between the two components, only that they are in the order indicated. The various features illustrated in the figures may be combined in many ways, and should not be interpreted as though limited to the specific embodiments in which they were explained and shown. Those skilled in the art having the benefit of this disclosure will appreciate that many other variations from the foregoing description and drawings may be made within the scope of the present invention. Indeed, the invention is not limited to the details described above. Rather, it is the following claims including any amendments thereto that define the scope of the invention.