Abstract:
The invention relates to fresh air ventilation devices adapted for use with air conditioners (ACs) and/or heaters. In operation, the device supplements the recirculating air of the AC/heater with fresh air drawn from outside of the building.

Description:
FIELD OF THE INVENTION 
     The invention relates to fresh air ventilation devices adapted for use with air conditioners (ACs) and/or heaters. Particularly, the fresh air ventilation device, when in operation, draws outside air from the outside to supplement the recirculating air of the AC/heater with fresh air. 
     BACKGROUND OF THE INVENTION 
     In an AC unit, it is common to provide a main partition in the unit with the evaporator being on the room side (interior) of the partition and the condenser and compressor being on the outside. During operation, the room air is recirculated through the evaporator for cooling. In a heat pump heating unit, the operation is in reverse, i.e., the room side being the condenser and the outside being the evaporator. In certain operations, it is desirable to introduce fresh air from the outside to mix with the recirculating air. For certain specified applications, it may be necessary to provide fresh air at up to 150 cubic feet per minute (CFM). Existing units generally only provide about 50-70 CFM of fresh air, which may not meet building codes and standards. 
     In most prior art designs, the evaporator blower wheel brings in the fresh air through one or more openings in the main partition. These openings have been located in areas of convenience and are accordingly only marginally effective at drawing in fresh air. More specifically, in most single-motor AC units, the evaporator motor is typically mounted to the outside of the main partition and its shaft extends through a hole in the partition to the evaporator blower wheel which is enclosed in a scroll. When fresh air is desired, a vent door in the main partition is opened and a path is provided for air to flow by evaporator blower wheel suction. The incoming fresh air mixes with the recirculation air as it enters the front of the evaporator blower wheel through the recirculation air orifice. With such a configuration, the fresh air flow rate is substantially below current new building standards. Further, because the flow of fresh air through the fresh air vent is drawn by a relatively slight negative pressure created at the vent door by the evaporator blower wheel, the flow rate can be substantially influenced by other factors such as the condenser fan or by interior roomside static pressure. More specifically, if the condenser fan on the back side of the partition is on at the same time that the vent door is open, some of the air which would otherwise be drawn through the main partition as fresh air could be drawn by the condenser fan and passed through the condenser to the outside. Examples of prior AC and/or heating units having fresh air ventilation are disclosed in U.S. Pat. Nos. 4,524,588; 4,553,405; and 5,372,189; which are incorporated herein by references. 
     Therefore, there remains a need to improve the fresh air ventilation capacity of existing AC and/or heating units. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a fresh air ventilation device for providing fresh air to an air conditioning (AC) or heating unit. The device contains an independent fan for supplementing the blower(s) of the unit with fresh air. The device is designed for effectively moving air from the exterior of the unit to the interior to help condition the space. 
     Another object of the present invention is to provide a ventilation assembly containing a duct and a ventilation device. The ventilation assembly mounts on the AC or heating unit and contains a fan, and a duct extending from the exterior side of the unit, through the internal partition within the unit and to the self-contained indoor fan. The fan, when activated, blows the outside air into the room side of the unit, which is then mixed with the recirculating room air that is being blown through the unit. 
     It is a further object of the present invention to provide an AC or heating unit with a vent assembly for allowing outdoor ambient air to enter the indoor section of the unit. Preferably, the ventilation unit is mounted on the outside of the unit and provides an air intake that is independent of the unit&#39;s evaporator or condenser blower. 
     A still further object of the present invention is to provide an apparatus which is economical to manufacture and maintain, simple in construction, easy to operate and compact in size and number of parts. 
     Other objects of the present invention will be apparent from the following Description of the Preferred Embodiments and from the appended claims. 
     The preceding objects are achieved according to the preferred embodiment of the invention by the provision of an AC/heating unit which is divided by a partition into an indoor section and an outdoor section. The indoor section includes an indoor heat exchanger and means for circulating air within the space to be conditioned and the indoor section. The outdoor section includes an outdoor heat exchanger and means for circulating outdoor air through the outdoor section. The indoor section includes a fresh air ventilation device containing a fan for blowing fresh air into the indoor section. The intake of the device is connected to a duct that connects the device to a fresh air source, such as the exterior or the building or the outdoor section of the unit. The exhaust of the device is opened to the indoor section of the unit. In an embodiment, the fresh air ventilation device is mounted on the outside wall of the AC/heating unit through an opening in the indoor section of the unit. The duct connects to the device through the opening; and the device blows fresh air into the indoor section through the opening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an AC unit with the front cover removed. 
         FIG. 2  shows a top cut away view of the AC unit  10  taken along line A-A of  FIG. 1 . 
         FIG. 3  shows a front view of the AC unit. 
         FIG. 4  shows the parts of the fresh air ventilation device. 
         FIG. 5  shows the assembled fresh air ventilation device. 
         FIG. 6  shows the unit having a heater for preheating the air. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , there is shown an AC/heating unit  10  using the invention to advantage. Although the unit  10  is shown as a combination AC and heater unit which is mounted through a wall or window opening, it is understood that the inventive principle is applicable to other types of units, such as AC only, heater only, heat pump units and units which are not mounted in a wall or window opening. The air conditioner  10  can be controlled by accessing the control panel  16 . Additionally, the unit may be controlled by a variety of control mechanisms, including remotely mounted thermostatic controllers, handheld remote controllers or other means. In operation, recirculating air is drawn from the room through the front and/or the underside  12  and expelled back into the room through the exhaust  18  located at the front top. 
     Referring to  FIG. 2 , there is shown a top cut away view of the AC unit  10  taken along line A-A of  FIG. 1 . As is conventional, the unit  10  is generally divided into an indoor section  20  and an outdoor section  22  by a main bulkhead  24 . The bulkhead  24  functions as a barrier to prevent noise and outside air from entering the room to be cooled. In one mode of operation, air is prevented from flowing from the outdoor section  22  to the indoor section  20  such that all of the air being cooled is recirculation air from the room. A blower  26 , when activated, draws air from the room through the front underside  12 , directs the air through an evaporator  28 , and expels it through the exhaust  18 . The air is cooled as it passes through the evaporator  28  before being expelled through the exhaust. 
     The heat exchange transfer between the evaporator  28  and the condenser  30  is conventional. More specifically, a working fluid commonly referred to as a refrigerant goes through a thermal dynamic cycle. The refrigerant leaves the compressor  32  as a vapor at an elevated pressure and then condenses in the condenser  30 , resulting in the transfer of heat to the condenser  30 . This heat is removed by using a condenser fan  34  to pass air across the tubes and fins (not shown) of the condenser  30  for exit to the outside through the rear louvered wall  36  of the outside section  22 . The side  38  of rear louvered wall  36  also communicates with the outside, so that fresh air is drawn through the condenser  30  by the condenser fan  34 . 
     The high pressure refrigerant liquid passes from the condenser  30  through an expansion valve or capillary tube  40  where some of the refrigerant liquid flashes into vapor. The remaining fluid passes through a conduit  42  to the evaporator  28  where it vaporizes as a result of the relatively low pressure therein. The heat to support the vaporization is transferred from the air that is directed through the evaporator  28  by the blower  26 . The closed loop is completed by a conduit  44  that connects the relatively low pressure evaporator  28  to the compressor  32 . Both of the conduits  42  and  44  pass through small openings in the bulkhead  24 . Those skilled in the art will recognize that the AC unit  10  as described can be made to function as a heater by providing components that reverse the direction of flow of the refrigerant so that the functions of the condenser  30  and evaporator  28  are reversed. Accordingly, warm air would be blown into the room and the cooler air would be exhausted to the outside. The invention, however, as described in detail hereinafter, has particular advantage for operation as an air conditioner or heater. Henceforth, reference numeral  10  refers to an AC or heating unit. 
     Referring to  FIGS. 1-3 , in accordance with the present invention, a fresh air ventilation device  300  is provided with the unit  10 . In the illustrated embodiments, the device  300  is attached on the exterior of the unit  10  and is exposed to the indoor section  20  of the unit  10  through an opening  302  in a side wall of the unit  10 . The device  300  contains a fan  304  (shown in  FIGS. 4-5 ) for blowing fresh air into the indoor section  20 . The intake side of the fan  304  is connected to the outside of the unit  10  by a duct  306 . The duct  306  is attached on a first end  310  to the intake side of the fan  304 . The second end  308  of the duct  306  is connected to the outside of the unit  10 . The duct  306  is preferably routed through the main bulkhead  24  though an opening just large enough to allow the duct  306  to pass therethrough without compromising the integrity of the bulkhead  24 . The fresh air ventilation device  300  is attached to the side wall of the AC/heating unit  10  using fasteners, such as screws or bolts. 
     As further illustrated by  FIGS. 1 and 2 , the device  300  is positioned at the bottom of the front end of the unit  10 . In that location, the device  300  is inside the room and is accessible to the user for operation. In addition, the device  300  can be easily mounted to existing AC/heater units  10 . However, it should be appreciated that the device  300  can be configured to be mounted to other suitable locations of an AC/heater unit  10 , within the scope of the invention. 
     Referring to  FIGS. 4-5 , a preferred embodiment of the device  300  is depicted. In this embodiment, the device  300  is essentially an enclosed container mounted on the unit  10  such that an operating side  400  of the container is mounted flush against the opening  302 . The operating side  400  has an opened face that is divided into two portions. The first (expel) portion  402  contains the fan  304 ; and the second (input) portion  404  is attached to the duct  306 . In a preferred embodiment, the second portion  404  contains a filter  406  for filtering the fresh air before it is propelled into the indoor section  20 . In this embodiment, the top side  408  of the device is removable to allow the filter  406  to be changed or cleaned. As illustrated in  FIG. 4 , the top side  408  is preferably screwed to a support member  410  with a knobbed screw  412 , which allows for quick and easy access to the filter  406 . The support member  410  has an upright section  418  which separates the input portion  404  from the expel portion  402 . The fan  304  is mounted within a receiving flange  420  at the end of the expel section  402  and is screwed to the upright section. Likewise, the filter  406  is received in a receiving flange  422  at the input section  404  of the device housing, and is set within the upright section of the support member  410 . The top section of the support member  410  is substantially perpendicular to the upright section  418 , and extends across the top of the device  300 . 
     With the top  408  in place, the housing of the device  300  operates as a plenum. The fan  304  pulls fresh air though the duct  306  from the outside of the unit  10 . The fresh air enters the plenum at the input portion  404 . The air passes through the filter  406 , through the plenum and out the expel portion  402  of the device  300 . The fan  304  propels the fresh air across the input side of the blower  26 . The blower  26  effectively mixes the fresh air it receives from the fan  304  with the room air it pulls in from the room, and forces that mixture across the evaporator  28  and into the room. That provides the desired increased amount of fresh air into the mixture which is cooled by the unit  10 . Although this arrangement is preferred, it should be apparent to one skilled in the art that other methods for removably attaching the top side  408  to the device  300  can be adapted for use with the present invention. The operating side  400  may contain flanges  414  having holes  416  therein to attach the device  300  to the AC/heating unit  10 . 
     The fan  304  of the device  300  is electrically connected to the unit fan controller and is designed to run whenever the unit indoor fan is operating. In another embodiment, a controller for controlling the speed of the fan (e.g., high, medium, low), and thus, the amount of fresh air being introduced into the indoor section  20  is connected to the apparatus. This allows a user, e.g. by turning a control knob on the controller, to adjust the amount of fresh air entering the room. In certain embodiments, the controller can be used to activate the fan  304  at certain times of the day by presetting the controller. It may also be possible to automatically activate the fan  304  based on the oxygen level in the room. In this embodiment, an oxygen sensor is placed in the room and is connected to the controller electrically or wirelessly. When the oxygen sensor drops below a preset level, the fan  304  is activated to draw fresh air into the indoor section  20  of the unit  10 . In another alternative embodiment of the invention, the device  300  can be configured to be automatically operated whenever the AC/heater unit  10  is operated, to provide a desired mixture of fresh air to recirculated room air. 
     In an additional embodiment, when the unit  10  is being utilized as a heater, it may be necessary to pre-heat the fresh air entering the unit  10  to prevent freezing of the unit  10  or freezing of other interior fixtures. In particular, ancillary hot water heating apparatus and/or room plumbing fixtures (e.g. evaporator  28 , condenser  30 , blowers  26 , etc.) and piping (e.g. conduits  42  and  44 , etc.) can freeze or crack if the fresh air is too cold. Thus, this is especially desirable for use with heaters where the fresh air entering the unit  10  can be significantly below the freezing temperature. In the embodiment of  FIG. 3 , a thermostat  50  is installed in the indoor section  20  of the unit  10 . As shown, the thermostat  50  is preferably located within the airstream from the indoor unit air. If the temperature drops below a set point, the thermostat activates a heating system  52  to preheat the fresh air before it enters the indoor section  20 . In the embodiment shown, an electric heater  52  can be located inside the unit  10  to heat the fresh air as it passes through the unit. 
     When the AC/heating unit  10  containing the fresh air ventilation device  300  is in use, the user can manually activate the device  300  manually or automatically. When activated, the device  300  draws air from the fresh air source and injects it into the indoor section  20  of the unit  10 . This allows the blower  26  to mix the fresh air with the recirculating air and improves the quality of the air exiting the AC/heating unit  10 . 
     Although certain presently preferred embodiments of the invention have been specifically described herein, it will be apparent to those skilled in the art to which the invention pertains that variations and modifications of the various embodiments shown and described herein may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention be limited only to the extent required by the appended claims and the applicable rules of law.