Abstract:
A refrigeration unit is provided with a manually operated fresh air vent made up of a cap assembly and a handle assembly which move together in a linear/axial direction. The handle assembly is rotatable to change the position of the fresh air vent. The fresh air vent controls both the providing of fresh air to the circulating air in the trailer and the exhausting of a portion of the circulating air. The evaporator fan is run continuously when the air vent is open to prevent the build up of gases produced by the perishable cargo.

Description:
BACKGROUND OF THE INVENTION 
   Trailer refrigeration units are controlled by a microprocessor which receives inputs indicating the temperature, humidity, etc. in the conditioned space and controls the refrigeration system responsive to the inputs. Additionally, the microprocessor records the inputs such that the history of the load during the trip is recorded. Accordingly, it is possible to determine when and why a load is spoiled, thawed or the like. Perishable cargo such as fruit, vegetables and flowers produce, and are affected by, gases. Ethylene, for example, is produced in the ripening of bananas and its presence promotes ripening while respiration of the “live” cargo produces carbon dioxide and requires oxygen. It is therefore preferable to introduce some fresh air with the recirculating air, where perishable cargo is present, if spoilage or premature ripening of the load is to be avoided. 
   In a trailer, the load normally occupies much of the available space such that the flow paths for the conditioned air are located in the space between the load and the trailer ceiling, walls, floor, and the channels defined by the pallets on which the load sits. To minimize the wastage of conditioned space, only the expansion device, the evaporator, the evaporator fan, necessary ducting and sensors are located in the conditioned space. The rest of the refrigeration unit and its controls are located on the exterior of the trailer and are powered by an external power supply such as a diesel engine or the unit may be connected to the electric grid. 
   SUMMARY OF THE INVENTION 
   In the present invention a manually operated fresh air vent is provided to introduce some ambient/fresh air into the air circulating in the trailer and to exhaust some air from the trailer such as is done to provide some fresh air in commercial buildings. When the evaporator fan is running and the fresh air vent is open, the pressure differential across the evaporator fan is used to draw in fresh air and to exhaust stale air. The fresh air vent of the present invention has an open position, a closed position and one, or more, intermediate positions. 
   It is an object of this invention to discretely position a manually actuated vent. 
   It is another object of this invention to selectively provide a continuous supply of fresh air to a perishable cargo. 
   It is a further object of this invention to provide a manually actuated vent which requires no mechanical calibration. These objects, and others as will become apparent hereinafter, are accomplished by the present invention. 
   Basically, a refrigeration unit is provided with a manually operated fresh air vent made up of a cap assembly and a handle assembly which move together in a linear/axial direction. The handle assembly is rotatable to change the position of the fresh air vent. The fresh air vent controls both the providing of fresh air to the circulating air in the trailer and the exhausting of a portion of the circulating air. The evaporator fan is run continuously when the air vent is open to prevent the build up of gases produced by the perishable cargo. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the present invention, reference should now be made to the following detailed description thereof taken in conjunction with the accompanying drawings wherein: 
       FIG. 1  is a simplified schematic diagram of a trailer and its refrigeration unit; 
       FIG. 2  is a simplified schematic representation of the fresh air vent structure; 
       FIG. 3  is a pictorial view of the assembled fresh air vent structure; 
       FIG. 3A  is an enlarged view of the indicia in  FIG. 3 ; 
       FIG. 4  is a pictorial view of the cap and handle assemblies; 
       FIG. 5  is a partially cutaway view of the fresh air vent structure of  FIG. 3  in the closed position; 
       FIG. 6  is a partially cutaway view of the  FIG. 5  structure in its open position; 
       FIG. 7  is a partially cutaway view of modified fresh air vent structure in the closed position; and 
       FIG. 8  is a partially cutaway view of a portion of the  FIG. 7  structure in the open position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In  FIG. 1 , the numeral  10  generally designates a refrigeration unit which is mounted on a trailer  12 . Insulation  11  and  13  line the pod portion of unit  10  and trailer  12 , respectively, and separates the portions of refrigeration unit  10  which are located in trailer  12  from the portions located external to the conditioned area. Refrigeration unit  10  includes a fluid circuit serially including compressor  14 , discharge line  16 , condenser  18 , expansion device  20 , evaporator  22  and suction line  24 . Compressor  14  is driven by diesel engine  15  under the control of microprocessor  100  responsive to inputs from sensors  102  which includes sensors for temperature, pressure, etc. Evaporator  22 , evaporator fan  22 - 1  and a portion of evaporator fan drive shaft  22 - 2  are located within trailer  12  and the expansion device  20  can be within trailer  12  or just outside. Microprocessor  100  controls both compressor  14  and diesel engine  15 . Diesel engine  15  directly drives compressor  14  and is connected via pulleys, P, and a belt, B, to drive shaft  22 - 2  for driving condenser fan  18 - 1  and evaporator fan  22 - 1 , respectively. When evaporator fan  22 - 1  is driven it causes conditioned air from evaporator  22  to be distributed through trailer  12  and return air to be delivered back to evaporator  22 . Diesel engine  15  is also connected via a pulley, P, and a belt, B, to alternator  26  which can then supply electric power, as required, to unit  10 . 
     FIG. 2  is a more detailed depiction of a portion of the  FIG. 1  system adding details of the actuation of the fresh air vent structure which is collectively labeled  28 . Fresh air vent structure  28  is made up of cap assembly  30  and handle assembly  40 . As will be described in detail below, tubes or ducts  22 - 6  and  22 - 7 , respectively, extend from points upstream and downstream, respectively, of evaporator fan  22 - 1  to points near to the grille of refrigeration unit  10 . Caps consisting of larger tubes  31  and  32 , respectively, with blanked ends and slots  31 - 1  and  32 - 1 , respectively, for openings are placed over the ends of ducts  22 - 6  and  22 - 7 , respectively. Caps  31  and  32  are connected by webbing  33  such that they move axially as a unit. The cap assembly  30  is made up of caps  31  and  32  and webbing  33  which are, preferably, made as, or assembled as, a single unit which is secured to handle assembly  40 . When handle assembly  40  is pulled to the right, as illustrated in  FIG. 2 , cap assembly  30  moves also from its closed position allowing the slots  31 - 1  and  32 - 1  in the cap assembly  30  to be in fluid communication with ducts  22 - 6  and  22 - 7 , respectively, to allow fresh air into, and stale air out of the trailer  12 . With handle assembly  40  pulled to the right, it is then rotated to the desired setting indicated by the indicia, shown in  FIG. 3A , and allowed to move to the left under the spring bias. Depending upon the rotary position of the handle assembly  40 , cap assembly  30  may be open, closed or partially open. 
   The evaporator fan  22 - 1  is located in opening  22 - 3   a  of fan housing  22 - 3  and when operating coacts therewith to separate chamber  224  from chamber  22 - 5  such that chamber  224  is at evaporator fan suction pressure and chamber  22 - 5  is at evaporator fan discharge pressure. Note that both chambers  224  and  22 - 5  are downstream of evaporator  22 . The first flow path defined by duct  22 - 6  connects to the return air path just upstream of evaporator fan  22 - 1  and, when cap  31  is in its open position, permits some fresh air to enter chamber  22 - 4 . The supplying of a portion of atmospheric air through duct  22 - 6  is possible because the pressure in chamber  22 - 4  is less than ambient pressure. The second flow path defined by duct  22 - 7  connects to the return air path just downstream of evaporator fan  22 - 1  and fan housing  22 - 3  and, when cap  32  is in its open position, permits a portion of return air to be discharged into the atmosphere since chamber  22 - 5  is at fan discharge pressure which is above ambient. 
   The degree and duration of opening of caps  31  and  32  together with the speed of evaporator fan  22 - 1  determine the amount of air being exhausted and supplied. Microprocessor  100  is connected to and controls evaporator fan  22 - 1  through diesel  15  via belt B and pulleys P. The evaporator fan, must be run in order to produce the necessary pressure differential for drawing in fresh air and exhausting stale air. 
   Referring specifically to  FIG. 3  which clearly shows duct  22 - 7  extending downwardly, it will be noted that because duct  22 - 7  is not straight, as depicted in  FIG. 2 , caps  31  and  32  are reversed from their  FIG. 2  positions. Referring to  FIGS. 3–6 , it will be noted that caps  31  and  32  have circumferentially extending slots defining ports  31 - 1  and  32 - 1 , respectively. Ports  31 - 1  and  32 - 1  are approximately 180° in extent and have a width nominally equal to the stroke of caps  31  and  32 , respectively. Cap assembly  30  and handle assembly  40  are secured together and are supported by welded bracket  50  which is secured to refrigeration unit  10 . Referring specifically to  FIGS. 3 and 3A , it will be noted that indicia are located on cap  31  which indicate the position of the cap assembly  30  relative to the rotary position of the handle assembly  40 . Specifically, handle assembly positions indicating “open”, “50%”, and “closed” as to the cap assembly  30  are illustrated. 
   Taking  FIGS. 3 ,  5 , and  6  together, it will be noted that bracket  50  includes tubular portions  50 - 1  and  50 - 2 , to which tubes  22 - 6  and  22 - 7 , respectively, are secured by clamps  60 , and wall portion  50 - 3 . Wall portion  50 - 3  is located between tubular portions  50 - 1  and  50 - 2  and has an aperture  50 - 3   a  therein. Plastic sleeves  51  and  52  are located on tubular portions  50 - 1  and  50 - 2 , respectively. Closed cell neoprene gaskets, or other suitable resilient material,  34  and  35  line the blanked ends of caps  31  and  32 , respectively. As best shown in  FIG. 5 , gaskets  34  and  35  seal against the outer ends of tubular portions  50 - 1  and  50 - 2 , respectively, to close off air flow between the trailer  12  and the atmosphere. Sleeve  51  is located between tubular portion  50 - 1  and cap  31  to provide vibration isolation. Similarly, sleeve  52  is located between tubular portion  50 - 2  and cap  32 . 
   Handle assembly  40  is best shown in  FIGS. 4–6 . Handle assembly  40  includes a shaft  41  having a large diameter section  41 - 1  separated from intermediate diameter section  41 - 3  by shoulder  41 - 2  and having a threaded end portion  414 . A handle, H, is welded or otherwise suitably secured to the end of large diameter section  41 - 1 . In assembling handle assembly  40 , nylon washer  42  is located on the intermediate diameter section  41 - 3  and threaded end portion  41 - 4  is inserted through aperture  33 - 1  such that nylon washer  42  is located between shoulder  41 - 2  and webbing  33  of cap assembly  30 . Serially, a second nylon washer  43 , a stack of Belleville washers  44  which function as springs, bearing  45 , coil spring  46  and stainless steel tube  47  are located on the intermediate diameter section  41 - 3 . Bearing  45  is bolted to or otherwise suitably secured to bracket  50  and has a bore  45 - 1  through which one end of tube  47  passes to engage Belleville washers  44 . Bearing  45  has a frustoconical recess  45 - 2  for receiving one end of spring  46 . A spring retainer  47 - 1  is formed in one end of tube  47  for receiving the other end of spring  46 . Hex adapter  48  is threaded onto threaded portion  41 - 4  of shaft  41  and engages spring retainer  47 - 1  and thereby tube  47 . It should be clear that because tube  47  is located between hex adapter  48  and Belleville washers  44  the threading of hex adapter  4 . 8  on threaded portion  414  moves tube  47  to the left, as illustrated in  FIG. 5 , compressing both Belleville washers  44  and coil spring  46 . It should be noted that Belleville washers  44  are the only significantly resilient members between the left end of tube  47 , as illustrated, and shoulder  41 - 2  such that reducing the separation of the end of tube  47  and shoulder  41 - 2  by threading hex adapter  48  towards the left produces a bias acting on web  33 . The compressed Belleville washers  44  acting on washer  43  and tube  47  bias handle assembly  40  into engagement with cap assembly  30  such that they move as a unit in an axial direction. 
   Hex adapter  48  has a first bore  48 - 1  which is threaded for receiving set screw  54  to hold adapter  48  in place, a second bore  48 - 2  for receiving roll pin  55  which extends radially therefrom, and a threaded bore  48 - 3  for receiving bolt  56 . With specific reference to  FIGS. 4 and 5 , it will be noted that positioner or adapter  62  is located on hex adapter  48  in engagement with roll pin  55  and is located within and secured to bracket  64 . Bearing  45  and bracket  64  are bolted or otherwise suitably connected. Bolt  56  is threaded into threaded bore  68 - 1  of back bearing  68  and threaded bore  48 - 3  of hex adapter  48 . As best shown in  FIG. 4 , positioner or adapter  62  has a plurality of radially spaced recesses of varying axial extent  62 - 1 ,  62 - 2  and  62 - 3 , respectively, as illustrated. Roll pin  55  is illustrated in recess  62 - 1  which represents the closed position of fresh air vent  28 . If roll pin  55  is in recess  62 - 2 , cap assembly  30  will be in the 50% open position and if roll pin  55  is in recess  62 - 3 , cap assembly  30  will be in the full open position. 
   Referring to  FIGS. 3–5 , fresh air vent  28  and cap assembly  30  and handle assembly  40  are in the closed position. The outer ends of tubular portions  50 - 1  and  50 - 2  engage gaskets  34  and  35 , respectively, in a valving action which prevents fluid communication between the atmosphere and the interior of trailer  12  via ducts  22 - 6  and  22 - 7 , respectively. Roll pin  55  is in recess  62 - 1  of bushing  62 . Belleville washers  44  and spring  46  are in their greatest extension permitted by hex adapter  48  at this time. Because handle H is rigidly connected to hex adapter  48 , when handle H is pulled outward it causes hex adapter  48  and tube  47  to move therewith as a unit. The Belleville washers  44  retain the same degree of bias because tube  47  maintains the same positioning with respect to Belleville washers  44  but spring  46  is compressed between bearing  45  and spring retainer  47 - 1  which moves towards bearing  45  permitting handle assembly  40  and the attached cap assembly  30  to move outward in an opening direction for the cap assembly  30 . By rotating handle H in accordance with the indicia on cap  32  illustrated in  FIG. 3A , upon release of handle H, roll pin  55  can be positioned to return to recess  62 - 1  to close the fresh air vent  28 , to recess  62 - 2  to put fresh air vent  28  in the half open position, or to recess  62 - 3  which is the fully open position of the fresh air vent  28  as shown in  FIG. 6 . 
   When handle H is pulled outward and rotated from the closed to the open position, the fresh air vent  28  will move from the closed position of  FIGS. 3–5  to the full open position of  FIG. 6  thereby opening cap assembly  30 . Because cap assembly  30  is secured to shaft  41 , outward movement of handle assembly  40  causes cap assembly  30  to move to the  FIG. 6  position, or to an intermediate open position, in which gaskets  34  and  35  are moved from their seating position on the ends of tubular portions  50 - 1 , and  50 - 2 , respectively, opening slots  31 - 1  and  32 - 1 , respectively. 
   With fan  22 - 1  running and cap assembly  30  in the open position of  FIG. 6 , chamber  224  is on the suction side of fan  22 - 1  and is therefore at less than ambient pressure. Accordingly, fresh air enters slot  31 - 1 , passes through tubular portion  50 - 1  and duct  22 - 6  into chamber  224  where the fresh air mixes with air circulating in the trailer  12 . The mixture of fresh and stale recirculating air is drawn from chamber  224  by fan  22 - 1  and is discharged into chamber  22 - 5  at a pressure which is greater than atmospheric. Accordingly, a mixture of stale recirculating air and a smaller amount of fresh air pass from chamber  22 - 5  into duct  22 - 7  serially passing through tubular portion  50 - 2  and slot  32 - 1  into the atmosphere. The remaining air delivered to chamber  22 - 5  by fan  22 - 1  circulates through trailer  12 . 
   The structure illustrated in  FIGS. 7 and 8  differs from the structure of  FIGS. 3–6  in that the cap structure  30  of  FIGS. 3–6  is made up of a plurality of parts  31 ,  32 ,  33  which are welded or otherwise suitably assembled. Cap structure  130  of  FIGS. 7 and 8  has portions  131 ,  132  and  133  made as a single piece of plastic or metal which has been molded or stamped out and caps  131  and  132  have slots  131 - 1  and  132 - 1  and are lined by gaskets  134  and  135 , respectively. Additionally,  FIGS. 7 and 8  make bracket  50 , the adapter  62 , bracket  64  and back bearing  68  of the  FIGS. 3–6  device as a single piece. Bracket  150  includes tubular portions  150 - 1  and  150 - 2  and wall portion  150 - 3  as well as positioner/adapter portion  150 - 4  which corresponds to adapter  62  and portion  150 - 5  which corresponds to bracket  64 . Sleeves  51  and  52  are eliminated. So the embodiment of  FIGS. 7 and 8  operates the same as the embodiment of  FIGS. 3–6  and differs only in the bracket, cap, adapter and back bearing structure with parts being combined. The modified structure has been numbered  100  higher except where combined parts had plural separate numbers. 
   In operation, refrigeration unit  10  will operate under the control of microprocessor  100  to maintain the conditions in trailer  12  within a desired narrow range and to provide a history of conditions in trailer  12 , as is conventional. The running of evaporator fan  22 - 1  when fresh air vent  28  is open permits the drawing in of fresh air into the recirculating air and exhausting some of the stale recirculating air. 
   Although preferred embodiments of the present invention have been illustrated and described, other changes will occur to those skilled in the art. For example, the Belleville washers may be replaced with wavy springs. Also, because the Belleville washers are used to provide a bias to hold the parts in contact such that they move as a unit, the location of the Belleville washers can be on either side of the webbing  33  since they need only be located between shoulder  41 - 2  and the end of spring  47 . It is therefore intended that the scope of the present invention is to be limited only by the scope of the appended claims.