Abstract:
A convection barrier for a freezer is disclosed. The convection barrier may include a foil having at least one opening therein, storage and transport means for storing and moving the foil so as to transport the at least one opening to a desired position allowing access through the at least one opening to the interior of the freezer at the desired position and tensioning means for continuously keeping the foil in a tensioned state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to European Patent Application No. 08160042.1, filed Jul. 9, 2008, the entire contents of which are herein incorporated by reference in their entirety. 
       FIELD 
       [0002]    Embodiments of a convection barrier are described herein. In particular, embodiments of a convection barrier having a foil, storage and transport means and tensioning means are provided. More particularly, the convection barrier embodiments disclosed herein may be used in connection with a freezer. 
       BACKGROUND 
       [0003]    In clinical studies a wide variety of assays can be carried out to answer questions related to diagnosis (e.g., biomarker), treatment (e.g., efficacy of a drug) and prevention of diseases. 
         [0004]    Large sample collections of biological samples can be established, e.g., within the context of clinical studies. Such biological samples may include without limitation blood samples (e.g., whole blood, plasma, serum), urine samples, tissue samples, cells (e.g., cell lines, primary cell cultures), proteins, DNA, RNA (e.g., RNAi, mRNA), or antibodies. 
         [0005]    An automated facility for storing biological samples at −80° C. is used in the UK biobank and is described, for example, in the article “Designing and implementing a large-scale automated −80° C. archive,” by Justin M. Owen and Peter Woods, published in the International Journal of Epidemiology 2008; 37: i56-i61 (doi: 10.1093/ije/dym293). The store described therein comprises a system of drawers arranged in a manner so as to form a shelf, which allows robotic access to the biological samples whilst maintaining storage conditions. The drawers can be opened individually by the robot pulling the respective drawer outwards so as to allow access to the interior of the drawer where the biological samples are stored. 
         [0006]    However, this system has disadvantages. First, at its front surface each drawer is provided with a block made of styrene in a manner such that the styrene blocks of adjacently arranged drawers abut against one another. Upon opening an individual drawer by pulling the drawer outwardly, there is inherently the risk of an adjacently arranged drawer also being pulled out, even though not intended, thereby causing an unwanted temperature rise. Also, the total leakage of cold air is comparatively high because the system does not have a separate front door for closing the system. 
         [0007]    Cooling of a complete humidity controlled room for storing biological samples as described above to about −80° C. is generally feasible. However, standard handling devices, such as for example robots, usually do not work properly at such temperatures. Therefore, particularly for long-term storage of biological samples, specific −80° C. freezers are typically used. 
         [0008]    These specific freezers for long-term storage usually have a thermally insulating door which separates the environment outside the freezer (e.g., a −20° C. environment) from the −80° C. interior of the freezer. In a so-called “robotic store,” a plurality of such freezers is arranged as well as a robot for taking the samples out of each freezer. As mentioned above, the robot cannot be arranged in the −80° C. environment. Instead, the robot is arranged outside the freezers in the warmer −20° C. environment where it is capable of working properly. However, particularly with conventional upright standing freezers certain problems may arise in this configuration. First, upon having opened the door in order to allow the robot to access the interior of the freezer, the −80° C. cooled air flows out of the interior of the freezer while at the same time −20° C. air flows from the environment into the interior of the freezer, leading to a rise in temperature and humidity within the interior of the freezer. This is particularly the case because the door of the freezer usually must remain open for a considerable period of time until the desired one or more biological samples have been removed. Secondly, the flow of −80° C. air out of the freezer and −20° C. air into the freezer creates two effects: (i) a negative pressure that makes the door extremely difficult to open again until the negative pressure is equalized by inflowing air through the sealing of the door of the freezer, which usually takes a considerable period of time (e.g., up to 30 minutes); and (ii) the cooling down of the −20° C. air which is more humid than the −80° C. air results in formation of ice within the freezer, requiring defrosting of the freezer more often. 
         [0009]    It is therefore an object of the invention to overcome the aforementioned disadvantages and to provide suitable measures to avoid or at least greatly reduce the above-described scenarios. Also, loss of energy should be reduced to a minimum while at the same time frequent access to the stored biological samples should be possible. 
         [0010]    This object is achieved through the convection barrier embodiments disclosed herein and through a freezer comprising such convection barrier embodiments. 
       SUMMARY 
       [0011]    Disclosed herein are embodiments of a convection barrier. Some embodiments of the convection barrier are particularly well-suited for use in a freezer. Exemplary embodiments of the convection barrier may include a foil having at least one opening therein, storage and transport means for storing and moving the foil to transport the at least one opening to a desired position to allow access through the at least one opening to the interior of the freezer at the desired position and tensioning means for continuously keeping the foil in a tensioned state. 
         [0012]    In some embodiments, the foil may cover the opening to the interior of the freezer so that no cold air (e.g., −80° C.) may flow out of the interior of the freezer or that only small amounts of cold air may flow out of the freezer when the freezer door is open. However, it must be possible to access a desired sample or samples stored in the interior of the freezer. In some embodiments, this can be achieved by allowing access (e.g., by a robot) to a desired one or more samples through an opening or openings provided in the foil. According to some embodiments, because a sample may be stored at any location in the interior of the freezer, the opening must be movable to the position where the respective sample is located or stored. To move the one or openings, some embodiments of the convection barrier may include storage and transport means for storing and transporting the foil so that the opening in the foil can be moved to the position and stored in this position to allow access to a sample through the opening. To avoid jamming of the foil and in order to keep the air cold (e.g., −80° C.) within the interior of the freezer, tensioning means are provided for keeping the foil in a tensioned state during storing and transporting. Thus, outflow of cold air (e.g., −80° C.) out of the interior of the freezer and backflow of warmer air (e.g., −20° C.) from the environment into the interior of the freezer is prevented or at least greatly reduced. Accordingly, the above-described disadvantages of temperature rise in the interior of the freezer and negative pressure making the door extremely difficult to open are prevented or at least greatly reduced by the convection barrier embodiments disclosed herein. 
         [0013]    In some embodiments of the convection barrier, the storage and transport means may comprise two reels to which the opposite ends of the foil are mounted and between which the foil extends. Some embodiments of the convection barrier may also include a drive for rotating the reels so as to wind up or unwind the foil from the respective reel to transport the at least one opening to the desired position. 
         [0014]    Some embodiments of the convection barrier may comprise a frame having at least one opening, the frame being insertable into the foil at a location between the ends of the foil such that the at least one opening of the frame for allowing access to the interior of the freezer can be transported to any desired position. According to some embodiments, the frame may be rigid and stable to reliably position the opening at a desired location so as to allow access (e.g., by a robot) to the interior of the freezer through the at least one opening. 
         [0015]    In some embodiments of the convection barrier, the drive may comprise a motor connected to one of the at least two reels, and the tensioning means may comprise a return spring connected to the other one of the at least two reels for continuously keeping the foil in a tensioned state. In exemplary embodiments, that reel to which the motor is connected may be driven by the motor while the other reel is acted upon by the return spring so that the foil is always kept in a tensioned state. This configuration is advantageous because it allows various additional embodiments to be conceived, as discussed below. 
         [0016]    In some embodiments, the drive may further comprise a belt engaging both of the two reels, and the return spring may be a spring having a low spring rate. Since the belt already provides for synchronization of the two reels, i.e., the reels are driven with the same speed, the return spring must only have a low spring rate in order to keep the foil in a tensioned state. While the outer diameter of the respective reel with the foil wound around it continuously changes during movement of the foil, the return spring maintains the foil in a tensioned state. 
         [0017]    In some embodiments, the return spring may be a spring having a high spring rate. Particularly in the case where there is no mechanical connection between the two reels (e.g., by means of the aforementioned belt), it is advantageous that the spring has a high spring rate in order to make sure that the foil is always kept in a tensioned state. 
         [0018]    One example of a return spring having a high spring rate includes without limitation a torsion spring. In some embodiments, the torsion spring can be arranged within a hollow reel to achieve the advantages of the convection barrier according to some embodiments of the invention. 
         [0019]    In some embodiments of the convection barrier, the drive and the tensioning means may comprise two motors. Some embodiments may include one of the two motors being connected to one of the two reels and the other motor being connected to the other one of the at least two reels. The convection barrier may also, according to some embodiments, comprise a control unit for operating the two motors in an asynchronous manner so as to continuously keep the foil in a tensioned state. In some embodiments, the control unit may have two functions: First, it may control the speed of the reels, depending on whether the reel is winding the foil up or unwinding the foil, depending on how much of the foil is still wound around the respective reel. The control unit may also function, according to some embodiments, to drive the two motors in an asynchronous manner so as to make sure that the foil is always kept in a tensioned state. In this embodiment, one of the two motors may act in a manner similar to the aforementioned mechanical return spring, depending on the direction of movement of the foil. 
         [0020]    Possible materials for the foil may include without limitation, polytetrafluoroethylene or a mesh, e.g., a glass mesh, coated with polytetrafluoroethylene. Polytetrafluoroethylene is readily available on the market and is capable of fulfilling the requirements with regard to the operational demands, in particular with respect to temperature, mechanical stress and durability. 
         [0021]    As already mentioned above, embodiments of the convection barrier may be used in connection with a freezer. In some embodiments, the freezer may comprise a housing and a door. In some embodiments, the housing may have an opening allowing access to the interior of the freezer through the opening when the door of the freezer is open. Embodiments of the freezer preferably further comprise a convection barrier as described above. The convection barrier may be arranged, according to some embodiments, such that the opening allowing access to the interior of the freezer is covered by the foil. 
         [0022]    In one particularly advantageous embodiment of the freezer, one or more motors, or a belt, of the convection barrier may be mounted to the freezer outside its housing. This is advantageous because the motor or motors work well in the environment outside the freezer, e.g., in a −20° C. environment, while this is not the case in the environment in the interior of the freezer, e.g., in a −80° C. environment. Also, maintenance of these components is possible in the environment outside the freezer (e.g., −20° C.). 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0023]    Further advantageous aspects of the invention will become apparent from the following description of embodiments of the convection barrier with the aid of the Figures  1 - 15 . 
           [0024]      FIG. 1  shows a cross-sectional side view of a freezer in accordance with some embodiments of the invention with an embodiment of the convection barrier according to the some embodiments of invention mounted thereto. 
           [0025]      FIG. 2  shows a front view of an embodiment of the convection barrier according to the invention. 
           [0026]      FIG. 3  shows the upper reel of the convection barrier to which the foil is mounted according to some embodiments of the invention. 
           [0027]      FIG. 4  shows the lower reel of the convection barrier to which the foil is mounted according to some embodiments of the invention. 
           [0028]      FIG. 5  shows a perspective view of an embodiment of the freezer according to the invention with an embodiment of the convection barrier according to the invention mounted thereto. 
           [0029]      FIG. 6  shows the detail VI of  FIG. 5  in an enlarged view. 
           [0030]      FIG. 7  shows the detail VII of  FIG. 5  in an enlarged view. 
           [0031]      FIG. 8  shows the detail VIII of  FIG. 5  in an enlarged view, partially broken away. 
           [0032]      FIG. 9  shows the detail IX of  FIG. 5  in an enlarged view, partially broken away. 
           [0033]      FIG. 10  shows a perspective view of an embodiment of the freezer according to the invention with an embodiment of the convection barrier according to the invention mounted thereto. 
           [0034]      FIG. 11  shows the detail XI of  FIG. 10  in an enlarged view. 
           [0035]      FIG. 12  shows the detail XII of  FIG. 10  in an enlarged view. 
           [0036]      FIG. 13  shows a perspective view of an embodiment of the freezer according to the invention with an embodiment of the convection barrier according to the invention mounted thereto. 
           [0037]      FIG. 14  shows detail XIV of  FIG. 13  in an enlarged view. 
           [0038]      FIG. 15  show detail XV of  FIG. 13  in an enlarged view. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]      FIG. 1  shows a cross-sectional side view of a freezer  1  according to the invention with a convection barrier  2  mounted thereto, with the door of the freezer  1  not being shown in  FIG. 1  for the sake of simplicity. Freezer  1  comprises a housing  10  having an opening  11  at the front side of the freezer (in  FIG. 1  on the right hand side). A plurality of compartments  13  are arranged in the interior  12  of freezer  1 . In the third compartment from the bottom, a drawer  3  is represented by way of example which carries a plurality of trays  30  in which, e.g., microtubes (not shown), may be arranged in which the samples are stored. Convection barrier  2  comprises a foil  20 , the two opposite ends of which are mounted to two elongate reels, an upper reel  21  and a lower reel  22 , so that the foil extends therebetween. Convection barrier  2  is mounted to freezer  1  such that foil  20  of convection barrier  2  covers the opening  11  of freezer  1  so that the flowing out of cold air (e.g., −80° C. air) from the interior  12  of freezer  1  is prevented or is at least greatly reduced. As can be seen in  FIG. 1 , in order to get access to the respective drawer  3  carrying the tray  30  with the desired sample, a frame  23  comprising one or more openings  230  (see  FIG. 2 ) is inserted in the foil at a location between the two ends of the foil  20  such, that the one or more openings  230  allow access to drawer  3  carrying the tray  30  with the desired sample. 
         [0040]    One embodiment of convection barrier  2  according to the instant invention is shown in  FIG. 2 . In the embodiment shown in  FIG. 2 , outer frame  24 , foil  20 , and frame  23  carrying the one or more openings  230  (e.g., four openings) can be seen. Accordingly, columns (e.g., four) of drawers may be arranged in the interior of freezer  1 . In order to get access to the various compartments  13  in the interior  12  of freezer  1  where the respective drawer  3  carrying the tray  30  with the desired sample is arranged, frame  23  must be movable up and down in order to get to the respective location, as this is indicated by the arrows in  FIG. 2 . Frame  23  is preferably made from metal, e.g., aluminium, so as to reliably and stably position the openings  230  at the desired location in front of the respective drawer  3 . For proper functioning, foil  20  should be kept in a tensioned state. 
         [0041]      FIG. 3  shows the elongated upper reel  21  with the one end of foil  20  mounted thereto in an enlarged view, while  FIG. 4  shows the lower reel  22  with the opposite end of foil  20  mounted thereto. Through rotation of the upper and lower reels  21 ,  22  foil  20  can be wound up or unwound from the respective reel. This can be achieved in various ways, as explained in more detail below. 
         [0042]      FIG. 5  shows a perspective view of an embodiment of a freezer according to the instant invention comprising a specific embodiment of a convection barrier according to the invention. In this embodiment, like parts are assigned like reference signs but a letter “a” is added. Accordingly, freezer la comprises a housing  10   a  and a door  100   a  which is shown in its open position. Convection barrier  2   a  comprises an outer frame  24   a,  a foil  20   a  with a frame  23   a  carrying one or more openings  230   a.  Foil  20   a  extends between the two ends thereof which are mounted to elongate upper reel  21   a  and elongate lower reel  22   a,  respectively. A motor  25   a  drivingly engages an axle  210   a  which itself is connected to elongate upper reel  21   a  for rotatably driving upper reel  21   a.  A control unit  26   a  is provided for operating motor  25   a.  Lower elongate reel  22   a  is also connected to an axle  220   a.  Two belt pulleys  211   a  and  221   a  (see also  FIG. 6  and  FIG. 7 ) are mounted to axles  210   a  and  220   a,  respectively. An endless belt  27   a  is guided over belt pulleys  211   a  and  221   a  and engages the pulleys  211   a  and  221   a,  thus mechanically connecting axles  210   a  and  220   a.  Accordingly, as motor  25   a  rotatably drives axle  210   a  (and upper reel  21   a ) pulley  211   a  is also rotated and via belt  27   a  causes pulley  221   a  to rotate, thus rotating axle  220   a  (and lower reel  22   a ). Accordingly, upper and lower reels  21   a,    22   a  essentially rotate with the same speed. 
         [0043]      FIG. 6  shows detail VI of  FIG. 5  in an enlarged view. Although already shown in  FIG. 5 ,  FIG. 6  more clearly shows that motor  25   a  and control unit  26   a  as well as drive pulley  211   a  and belt  27   a  arranged on axle  210   a  are located outside the freezer, e.g., in the above-mentioned −20° C. environment where they work properly and can be maintained. The same holds true for drive pulley  221   a  arranged on axle  220   a,  as seen in greater detail in  FIG. 7 . 
         [0044]    In  FIG. 8  the detail VIII of  FIG. 5  is shown in an enlarged view and partially broken away. It can be seen how foil  20   a  enters beneath outer frame  24   a  and can be wound up or unwound from reel  21   a.    FIG. 9  shows the detail IX of  FIG. 5 , also partially broken away. From  FIG. 9  it can be seen that a torsion spring  28   a  arranged in the interior of reel  22   a,  which in some embodiments may be hollow. Torsion spring  28   a  is a weak spring which is always in a tensioned state, even when frame  23   a  carrying the openings  230   a  is in its lowermost position, so that foil  20   a  is always kept in a tensioned state. 
         [0045]      FIG. 10  shows a further embodiment of the freezer according to the invention comprising a specific embodiment of a convection barrier according to the invention. In this further embodiment, like parts are again assigned like reference signs but a letter “b” is added. Accordingly, freezer  1   b  comprises a housing  10   b  and a door  100   b  which is shown in its open position. Convection barrier  2   b  comprises an outer frame  24   b,  a foil  20   b  with a frame  23   b  carrying one or more openings  230   b.  Foil  20   b  extends between the two ends thereof which are mounted to elongate upper reel  21   b  and elongate lower reel  22   b,  respectively. A motor  25   b  drivingly engages an axle  210   b,  as can be seen in  FIG. 11  showing detail XI of  FIG. 10  in an enlarged view. Motor  25   b  is connected to elongate upper reel  21   b  for rotatably driving upper reel  21   b.  A control unit  26   b  is provided for operating motor  25   b.  In the interior of lower reel  22   b  which is embodied as a hollow reel, a torsion spring  28   b  is arranged. 
         [0046]    This can be seen more clearly in  FIG. 12  showing detail XII of  FIG. 10 , also partially broken away. From  FIG. 12  it can be seen that there is a torsion spring  28   b  arranged in the interior of reel  22   b,  which is embodied as a hollow reel. Torsion spring  28   b  is a weak spring which is always in a tensioned state, even when frame  23   b  carrying the one or more openings  230   b  is in its lowermost position, so that foil  20   b  is always kept in a tensioned state. 
         [0047]    As to the operation, it is essentially referred to the embodiment described above with respect to  FIGS. 5-9 , however, since there is no mechanical connection between the two reels via a belt, torsion spring  28   b  is a spring having a high spring rate. 
         [0048]      FIG. 13  shows a perspective view of still a further embodiment of a freezer according to the instant invention comprising a specific embodiment of a convection barrier according to the invention. In this embodiment like parts are assigned like reference signs but a letter “c” is added. Accordingly, freezer  1   c  comprises a housing  10   c  and a door  100   c  which is shown in its open position. Convection barrier  2   c  comprises an outer frame  24   c,  a foil  20   c  with a frame  23   c  carrying openings  230   c.  Foil  20   c  extends between the two ends thereof which are mounted to elongate upper reel  21   c  and elongate lower reel  22   c,  respectively. A motor  25   c  drivingly engages an axle  210   c,  as can be seen in  FIG. 14  showing detail XIV of  FIG. 13  in an enlarged view. Axle  210   c  is connected to elongate upper reel  21   c  for rotatably driving upper reel  21   c  with the aid of motor  25   c.  A control unit  26   c  is provided for operating motor  25   c.  Lower elongate reel  22   c  is also connected to an axle  220   c.  A further motor  28   c  drivingly engages an axle  220   c,  as can be seen in  FIG. 15  showing detail XV of  FIG. 13  in an enlarged view. Axle  220   c  is connected to lower reel  22   c  for rotatably driving lower reel  22   c  with the aid of motor  28   c.  Also, motor  28   c  is connected to control unit  26   c  (this connection not being shown in  FIGS. 13-15 ). Control unit  26   c  operates the two motors  25   c  and  28   c  in an asynchronous manner. Depending on the direction of winding foil  20   c,  one of the two motors  25   c,    28   c  acts as the driving motor while the other motor  28   c,    25   c  acts in a manner similar to the return spring. For example, as motor  25   c  acts as the driving motor and foil  20   c  is wound up onto upper reel  21   c,  then foil  20   c  is unwound from lower reel  22   c  and motor  28   c  acts as the return spring, thus continuously keeping foil  20   c  in a tensioned state. Or the other way round, as motor  28   c  acts as the driving motor and foil  20   c  is wound up onto lower reel  22   c,  then foil  20   c  is unwound from upper reel  21   c  and motor  25   c  acts as the return spring, thus continuously keeping foil  20   c  in a tensioned state. 
         [0049]    Finally, it is to be noted that many alternatives are conceivable, for example springs other than torsion springs can be used and the openings for gaining access to the interior of the freezer do not necessarily have to be provided in a frame. Also, it is to be noted that the convection barrier is a separate unit which can be adapted to the respective freezer to which it is to be mounted. Accordingly, the scope of protection is not intended to be limited by the described exemplary embodiments of the invention but rather is defined by the appended claims.