Abstract:
A refrigeration container is provided with a manually operated fresh air vent with a position sensor which provides a signal to the microprocessor based controller indicative of the position of the fresh air vent. The fresh air vent controls both the providing of fresh air to the circulating air in the container and the exhausting 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 
     Container 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. It is therefore necessary 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 container, the load normally occupies all of the available space such that the flow paths for the conditioned air are located in the floor, ceiling and walls of the container and are often at least partially defined by the load. 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 container and are powered by an external power supply. 
     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 container and to exhaust some air from the container such as is done to provide some fresh air in commercial buildings. When the temperature setting is above freezing, or another temperature indicative of a perishable load, the condenser fan is run continuously independent of the operation of the refrigeration system when the fresh air vent is open. The fresh air vent position sensor of the present invention continuously senses the position of the fresh air vent in the refrigeration container unit. The microprocessor based controller of the refrigeration container unit automatically records the time and position of the fresh air vent as well as the evaporator fan speed. In a preferred embodiment, mechanically keyed tangs transfer mechanical movement of the fresh air door to a rotary electronic sensor such as a sealed Hall effect sensor. The rotary electronic sensor has a output voltage proportional to its mechanical position and its output voltage is used by the controller to determine the position of the fresh air vent door. Relative to the fresh air vent, the microprocessor stores the manual vent position change, the trip start vent position, the power on vent position and the midnight or other periodic logging of the vent position. 
     It is an object of this invention to monitor the opening, closing and position of 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 sensor which cannot be improperly assembled as to its position and requires no mechanical calibration. These objects, and others as will become apparent hereinafter, are accomplished by the present invention. 
     Basically, a refrigeration container is provided with a manually operated fresh air vent with a position sensor which provides a signal to the microprocessor based controller indicative of the position of the fresh air vent. The fresh air vent controls both the providing of fresh air to the circulating air in the container 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 container 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. 4 is an exploded view of the fresh air vent structure of FIG. 3; 
     FIG. 5 is an enlarged view of a portion of the FIG. 4 structure partially assembled; and 
     FIG. 6 is an enlarged view of a portion of the FIG. 4 structure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, the numeral  10  generally designates a refrigeration unit which is mounted in a recess on a container  12 . Insulation  13  lines container  12  and separates the portions of refrigeration unit  10  which are located in container  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 motor  15  under the control of microprocessor  100  responsive to inputs from sensors  102  which includes sensors for temperature, humidity, etc. The expansion device  20 , evaporator  22 , evaporator fan  22 - 1  and evaporator fan motor  22 - 2  are located within container  12 . Evaporator fan motor  22 - 2  operates under the control of microprocessor  100  and causes conditioned air from evaporator  22  to be distributed through container  12  and return air to be delivered back to evaporator  22 . Although evaporator fan motor  22 - 2  is controlled by microprocessor  100 , it is not powered by microprocessor  100  but, rather by a generator, or the like, as is conventional. To the extent that structure is illustrated in FIG.  1  and described it is generally conventional. 
     FIG. 2 is a more detailed depiction of a portion of the FIG. 1 system adding details of the fresh air vent structure which is collectively labeled  30 . As will be described in detail below, air vent structure  30  includes a pair of valves which control two restricted flow paths,  30 - 1  and  30 - 2 , between the interior of refrigeration unit  10  and the surrounding atmosphere. Restricted flow paths  30 - 1  and  30 - 2  are illustrated as open. As noted with respect to FIG. 1, evaporator fan motor  22 - 2  operates under the control of microprocessor  100  and causes conditioned air from evaporator  22  to be distributed through container  12  and to be delivered back to evaporator  22 . If the container  12  contains a perishable cargo that produces gas(es) the air circulating in the container will contain the gas(es). 
     While it is desirable to remove the gas(es) produced by the cargo to retard ripening etc., its exhausting represents a loss in that it is at a temperature typically less than ambient and within a very narrow temperature range in order to maximize the quality of the load. However, since a perishable load such as flowers or produce, typically, is kept at about 40° F. which is about mid-range for normally encountered ambient temperatures, the temperature difference between the load and ambient does not present a serious energy loss in the practice of the present invention. Fresh air vent structure  30  is manually adjusted to simultaneously open or close the two restricted flow paths  30 - 1  and  30 - 2 . The evaporator fan  22 - 1  is located in opening  22 - 3   a  of fan deck  22 - 3  and when operating coacts therewith to separate chamber  22 - 4  from chamber  22 - 5  such that chamber  22 - 4  is at fan suction pressure and chamber  22 - 5  is at fan discharge pressure. Note that both chambers  22 - 4  and  22 - 5  are upstream of evaporator  22 . The first flow path  30 - 1  connects to the return air path just upstream of evaporator fan  22 - 1  and, when open, permits a selected portion of fresh air to enter chamber  22 - 4 . The supplying of a portion of atmospheric air through restricted flow path  30 - 1  is possible because the pressure in chamber  22 - 4  is less than ambient pressure. The second flow path  30 - 2  connects to the return air path just downstream of evaporator fan  22 - 1  and fan deck  22 - 3  and permits a selected 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 of opening of the valves of fresh air vent structure  30  coacts with the speed of evaporator fan  22 - 1  to determine the amount of air being exhausted and supplied. Microprocessor  100  is connected to and controls evaporator fan motor  22 - 2  and is connected to the position sensor  50  of fresh air vent structure  30  and is therefore capable of recording the supplying of fresh air during a trip. 
     Referring specifically to FIGS. 3 and 4, fresh air vent structure  30  includes a cover  40  which is typically made of metal. A threaded shaft  41  is suitably secured to cover  40  and extends axially outwardly therefrom. A circular recess  40 - 1  is formed in cover  40  and two radially spaced openings or ports  40 - 2  and  40 - 3  are formed in recess  40 - 1 . A pin  42  is secured in recess  40 - 1  radially outward of port  40 - 3 . Foam insulation  44  has a central opening  44 - 1  and two ports  44 - 2  and  44 - 3  which correspond to ports  40 - 2  and  40 - 3 , respectively. Door, or disc,  46  has a central opening  46 - 1  for receiving threaded shaft  41 . Door, or disc,  46  has two ports  46 - 2  and  46 - 3  which correspond to ports  44 - 2  and  44 - 3 , respectively, of foam insulation  44  which is secured to door  46  such that ports  44 - 2  and  44 - 3  are in registration with ports  46 - 2  and  46 - 3 , respectively. Door  46  has a pair of arcuate slots  46 - 4  and  46 - 5  for receiving pin  42 . Taken together slots  46 - 4  and  46 - 5  extend over approximately 90° with slot  46 - 4  having a lesser arcuate extent than slot  46 - 5 . 
     With pin  42  in either slot  46 - 4  or slot  46 - 5  and threaded shaft  41  extending through openings  44 - 1  and  46 - 1 , foam  44  and door  46  are secured to cover  40  by nut  48  threaded on shaft  41 . Rotation of foam  44  and door  46  as a unit produces a valving action as ports  44 - 2  and  46 - 2  are moved into and out of registration with port  40 - 2 . A corresponding valving action takes place as ports  44 - 3  and  46 - 3  are moved into and out of registration with port  40 - 3 . Pin  42  coacting with either slot  46 - 4  or slot  46 - 5  limits the rotary movement of door  46  with respect to cover  40 . Slot  46 - 4  controls the movement of door or disc  46  between closed and partially open whereas slot  46 - 5  controls the movement of door  46  between partially open and fully open. Tub  60  is typically made of plastic and has a peripheral flange  60 - 1  to permit the attachment of cover  40  thereto as by bolts or other suitable fasteners  62 . Tub  60  has a recess  60 - 2  formed therein and two spaced, raised portions  60 - 3  and  60 - 4 , respectively, extending outwardly from the bottom of recess  60 - 2 . The outer portion of raised portions  60 - 3  and  60 - 4  define grilled openings  60 - 3   a  and  60 - 4   a , respectively. When cover  40  is secured to tub  60  grilled openings  60 - 3   a  and  60 - 4   a  are in registration with ports  40 - 2  and  40 - 3 , respectively. 
     Referring specifically to FIGS. 4 and 6, Hall effect sensor  50  has a shaft  50 - 1  with a flat surface  50 - 1   a  such that shaft  50 - 1  has a D-shape in section. Sensor  50  is suitably secured in rectangular box  54  by nut  51  and washer  52 . Box  54  has flanges  54 - 1  which are suitably secured to cover  40  as by rivets  55 . U-shaped member  56  has a base portion  56 - 1  with an opening  56 - 1   a  therein having a flat portion  56 - 1   b  corresponding to flat surface  50 - 1   a  of shaft  50 - 1 . When shaft  50 - 1  is received in opening  56 - 1   a , U-shaped member  56  rotates with shaft  50 - 1 . Nut  58  secures U-shaped member  56  on shaft  50 - 1 . Arms  56 - 2  and  56 - 3  define tangs. Tangs  56 - 2  and  56 - 3  extend through arcuate slots  40 - 4  and  40 - 5 , respectively, in cover  40  so as to be freely movable with respect thereto, as best shown in FIG.  5 . Tangs  56 - 2  and  56 - 3  are received in openings  46 - 6  and  46 - 7 , respectively, of door  46 . 
     Shaft  50 - 1  of Hall effect sensor  50  has a rotational range of about 130° so that the 90° of the combined range of slots  46 - 4  and  46 - 5  is less than the rotational range of shaft  50 - 1 . In assembling air vent structure  30 , shaft portion  50 - 1 , threaded shaft portion  50 - 1 ′ and members  50 - 2  and  50 - 3  extend through bores  54 - 2  and  54 - 3  and a bore not illustrated such that sensor  50  is accurately located with respect to box  54 . Washer  52  is then placed on threaded shaft  50 - 1 ′ and nut  51  is threaded on shaft  50 - 1 ′ securing sensor  50  to box  54 . U-shaped member  56  is placed on shaft  50 - 1  with flat  50 - 1   a  and flat portion  56 - 1   b  coacting to angularly locate U-shaped member  56  with respect to shaft  50 - 1 . Nut  58  is then placed on shaft  50 - 1  to secure U-shaped member  56  thereon. Box  54  is riveted to cover  40  by rivets  55  as best shown in FIGS. 4 and 5. Hall effect sensor  50  has a plurality of leads  50 - 4 ,  50 - 5  and  50 - 6  which are located on one side of sensor  50 . Grommet  64  is located in opening  60 - 5  of tub  60 . Electrical connection  70  is connected to leads  50 - 4 ,  50 - 5  and  50 - 6  and passes through grommet  64 . The location of leads  50 - 4 ,  50 - 5  and  50 - 6  on one side of sensor  50 , the location of opening  60 - 5  on one side of tub  60  and the limited rotation of shaft  50 - 1  ensure proper assembly. 
     Tangs  56 - 2  and  56 - 3  are inserted through arcuate slots  40 - 4  and  40 - 5 , respectively. Cover  40  is secured to tub  60  by bolts  62 . Foam insulation  44  is secured to door  46  such that ports  44 - 2  and  44 - 3  are in registration with ports  46 - 2  and  46 - 3 , respectively. Foam insulation  44  and door  46  are selectively and changeably located on cover  40  in accordance with the amount of fresh and exhaust air desired. If the desired range is from closed to partially open, foam insulation and door  46  are placed such that threaded shaft  41  extends through openings  44 - 1  and  46 - 1 , tangs  56 - 2  and  56 - 3  are inserted in openings  46 - 6  and  46 - 7 , respectively, and pin  42  is inserted through slot  46 - 4 . Nut  48  is then threaded onto threaded shaft  41 . If the desired range is from partially open to fully open, the only difference would be locating pin  42  in slot  46 - 5 . Because the mechanical assembly is relatively accurate, the only calibration required is electronic. Specifically, upon assembly in place the signal is measured and set at zero. 
     When fresh air vent structure  30  is assembled, box  54  containing Hall effect sensor will be located in the space between raised portions  60 - 3  and  60 - 4 , such that Hall effect sensor  30  is accurately located in fresh air vent structure  30 . With shaft  50 - 1  received in opening  56 - 1   a  and tangs  56 - 2  and  56 - 3  received in openings  46 - 6  and  46 - 7 , respectively, shaft  50 , U-shaped member  56  and door  46  move as a unit. Hall effect sensor  50  is connected to the microprocessor  100  through connector  70 . Connector  70  is located in container  12  but extends therefrom to provide a signal to microprocessor  100 . 
     Preferably, when cover  40  is secured to tub  60 , the space is filled with foam for insulation. It is believed that illustrating the foam will only obscure details. When foam does fill the space, box  54  serves to isolate the Hall effect sensor  50  from the foam but box  54  is secured in place by the foam. Grommet  64  provides a leak tight seal to prevent foam from leaking from tub  60 . 
     In operation, refrigeration unit  10  will operate under the control of microprocessor  100  to maintain the conditions within a desired narrow range and to provide a history of conditions in container  12 , as is conventional. Superimposed upon the automatic control of refrigeration unit  10  provided by microprocessor  100 , a manual override is provided by fresh air vent structure  30  by exhausting a portion of the return air circulating in the container  12  and supplying fresh/ambient air as make up air. It should be noted that fresh air vent structure  30  would only be operated to provide fresh air when container  12  has a perishable cargo which produces gas(es). Fresh air vent structure  30  is opened by rotating door  46  and foam  44  which is secured thereto so that they rotate as a unit. Rotation of door  46  is limited by pin  42  which only permits movement of door  46  through the arcs defined by slots  46 - 4  and  46 - 5 . Rotation of door  46  and foam  44  in an opening direction from a closed position when pin  42  is received in slot  46 - 4  or when pin  42  is in slot  46 - 5  at apposition corresponding to the minimal opening will bring ports  46 - 2  and  44 - 2  into, or increase, registration with port  40 - 2  which is always in registration with grilled opening  60 - 3   a . The path serially defined by grilled opening  60 - 3   a , port  40 - 2 , port  44 - 2  and port  46 - 2  corresponds to the restricted path  30 - 1  illustrated in FIG. 2 between the return air and atmosphere. The position of door  46  will define the degree of registration of ports  44 - 2  and  46 - 2  with port  40 - 2  and grilled opening  60 - 3   a . Rotation of door  46  and foam  44  in an opening direction from a closed or minimally open position will also bring ports  46 - 3  and  44 - 3  into registration with port  40 - 3  which is always in registration with grilled opening  60 - 4   a . The registration between ports  46 - 2  and  40 - 2  will be the same as the registration between ports  46 - 3  and  40 - 3 . The path serially defined by port  46 - 3 , port  44 - 3 , port  40 - 3  and grilled opening  60 - 4   a  corresponds to the restricted path  30 - 2  illustrated in FIG. 2 between ambient and the return air at fan discharge pressure for discharging a portion of the return air. 
     As door  46  is rotated to open or close fresh air vent structure  30  rotation of door  46  will be as a unit with U-shaped member  54  and shaft  50 - 1  of Hall effect sensor  50 . Rotation of shaft  50 - 1  of Hall effect sensor  50  produces an output voltage which is proportional to the mechanical position of shaft  50 - 1  and this information is used by microprocessor  100  to determine the position of door  46 . The position of door  46  determines the degree of opening and this information in combination with the speed of evaporator fan  22 - 1  permits the determining of the amount of fresh air being supplied as make up air. 
     From the foregoing it should be clear that the present invention permits the position of a fresh air vent to be sensed by an electronic position sensor and stored in a microprocessor  100 . 
     Although a preferred embodiment of the present invention has been illustrated and described, other changes will occur to those skilled in the art. It is therefore intended that the scope of the present invention is to be limited only by the scope of the appended claims.