Patent Publication Number: US-8992293-B1

Title: Ventilator

Description:
TECHNICAL FIELD 
     This invention relates to pressure relief ventilators used on temperature controlled enclosures such as walk-in freezers and test chambers. 
     BACKGROUND OF THE INVENTION 
     Many temperature controlled commercial enclosed spaces need to be equipped with pressure relief ports or vents which are sometimes referred to as ventilators or ventilator ports. This is particularly true where the sealed space is subjected to temperature related gas volume variations that must be relieved. 
     Many of these enclosed spaces require that a positive air pressure differential to ambience be maintained. However there are spaces where no differential is required or desired. Passive ports are suitable for these enclosures. However existing passive pressure relief ports, meaning those without fans or blowers, have often permitted air migration where there is no significant pressure differential. With walk-in freezers this causes undesirable condensation and frosting. Frosting is a substantial problem that occurs as ambient warm air drawn into a low temperature chamber releases significant amounts of moisture relative to the change in dew point of the air at high and low temperatures. Air is drawn through the port after each door opening cycle as the warm air that entered the enclosure cools and contracts. If venting does not occur, a partial vacuum results which make it difficult to reopen the door. In extreme cases, the enclosures can even collapse. 
     A temperature rise in the enclosure between cooling cycles, and especially during a defrost cycle, creates a need to vent air to prevent pressure buildup. Again, failure to vent this pressure, with adequate relief capacity, can cause the chamber to rupture. 
     Passive pressure relief ports are in wide commercial use today. Large structures require the movement of a large amount of air to equalize the pressure between the inside and the outside of the enclosure. Existing vents can be either of a large size or a gang of small sized vents. This large amount of air carries with it a large amount of moisture. This moisture can condense almost immediately upon contact with the cold air and cold surfaces of the enclosure. If this occurs, a large ice block may form on the interior wall, which may eventually block the inflow of air through the port. This large ice block may also pose a potential danger to someone should it fall from the wall. 
     Accordingly, it is seen that a need exists for a passive pressure relief port, i.e. one that is not electrically powered by fans and baffles, yet which substantially prevents the formation of ice blocks within the enclosure. It thus is to be provision of such a pressure relief port that the present invention is primarily directed 
     SUMMARY OF THE INVENTION 
     In a preferred form of the invention a freezer ventilator comprises an air intake, a gang of air control valves, and a gang of air nozzles. Each air nozzle is associated with one air control valve. With this construction, the air nozzles accelerate an airstream there through to restricts the formation of ice adjacent the nozzle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a perspective view of a freezer ventilator that embodies principles of the invention in its preferred form, shown in a position mounted to a ceiling. 
         FIG. 2  is an exploded, perspective view of the freezer ventilator shown in  FIG. 1 . 
         FIG. 3  is a partial cross-sectional view of the freezer ventilator shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference next to the drawings, there is shown a ventilator  10  in a preferred form of the invention. The ventilator  10  is used with a temperature controlled enclosure, such as a freezer. The ventilator  10  includes a ventilator intake hood  11 , a pressure relief valve block  12 , and a nozzle plate  13 . 
     The intake hood  11  has a flared portion  15  having a series of intake holes  16  therein. A screen mesh  17  is positioned over the intake holes  16  to prevent insects and other foreign objects from entering the ventilator. 
     The pressure relief valve block  12  includes a gang or field of fourteen pressure relief valves  19  each positioned within a separate air channel  20 . Each pressure relief valve is the same as that depicted in U.S. Pat. No. 6,176,776, which is specifically incorporated herein. 
     The nozzle plate  13  includes a gang or field of fourteen nozzles  22 . Each nozzle  22  is aligned with an air channel  20  of relief valve block  12 . Each nozzle  22  defines an interior passage  23  which tapers inwardly as it extends outwardly along the direction of airflow indicated by the arrows in  FIG. 3 . 
     In use, air flows into the ventilator  10  by passing through intake holes  16  within the intake hood. This air is divided into multiple airstreams which pass through air channels  20  and pressure relief valves  19 , as described in more detail in U.S. Pat. No. 6,176,776. The multiple airstreams then pass into an enlarged portion of the channels  20  adjacent the nozzles  22 , and finally into the cooled enclosure through nozzles  22 . The enlarged portion of the channel  20  immediately before the narrowing nozzles  22  causes the airflow there through to accelerate through the nozzles  22 . 
     It has been discovered that with the addition of the nozzle the airflow or airstream into the cooled enclosure is accelerated as it passes through the nozzle. Hence, the airstream is expelled from the ventilator with a greater velocity than an airstream utilizing control valves alone. This increase in airstream velocity restricts the formation of ice upon the wall or ceiling adjacent the ventilator. As such, the moisture within the air freezes away from the wall, thereby creating small ice crystals that may be carried with the airstream to the refrigeration coils or other area where they will not accumulate in a harmful manner. Ice crystals captured upon the refrigeration coils may be expelled during normal defrost cycles of the refrigeration equipment. 
     It should be understood that any number of channels  20 , valves  19  and nozzles  22  may be utilized in practicing the invention. The number of such elements is dependent upon the volume of the desired airflow. It should also be understood that other types of valves and/or number of valves in relationship to the number of nozzles may be utilized as an alternative to that shown in the preferred embodiment. 
     It thus is seen that a ventilator is now provided which avoids the formation of an ice block upon the adjoining enclosure walls or ceiling. Though it has been described in detail in its preferred form, it should be realized that many modifications, additions and deletions may be made without departure from the spirit and scope of the invention as set forth in the following claims.