Abstract:
A storage apparatus has an annular array of stacked item storage formations, and an epicyclic selector arrangement for extracting items from the array, with a temporary storage unit.

Description:
PRIORITY CLAIM 
     This application claims priority to British Application GB 1208215.2, filed May 10, 2012 and to British Application GB 1210564.9, filed Jun. 14, 2012. 
     BACKGROUND AND SUMMARY 
     The present invention is concerned with a storage apparatus in which a plurality of individual items are stored and can be selectively accessed as required. In particular, the present invention is concerned with a storage apparatus in which chemical or biological samples are stored in a temperature controlled, sealed environment, and can be selectively deposited in, and removed from, the storage apparatus. 
     By “temperature controlled environment” we mean both environments below ambient (e.g. low temperature storage) and above ambient (e.g. incubators). 
     It is known to provide storage for chemical or biological samples. Such storage facilities are designed to store chemical or biological samples for long periods of time. In order to avoid degradation, such samples are stored at very low temperatures-typically in the order of minus 20 degrees down to minus 80 degrees Celsius and even lower. It is desirable to minimise the amount of space such storage facilities use, because laboratory space is often at a premium. Also, refrigeration to such temperatures uses energy, and because it is desirable to store many such samples, they are usually stored in a high density arrangement to minimise volume, and therefore maximise energy efficiency. The downside of high density storage is that it makes access to a single sample problematic, particularly if it lies in the centre of the storage arrangement. Access to a single sample requires movement of the surrounding samples, which may necessitate bringing them into a higher temperature environment, which is undesirable. 
     Some known devices utilise a Cartesian (XYZ) robot system to select individual items from a high density array. In such systems the robot is positioned within a cold zone. Typically such a zone will be at minus 20 degrees Celsius. Groups of samples can be extracted from the storage chamber (at, say, minus 80 degrees Celsius) via a simple mechanism individual items can then be selected and moved to ambient for examination. It is difficult to access an individual sample without exposing the surrounding samples to higher temperatures (either minus 20 degrees or ambient). Disadvantageously, placing the robot in a cold zone means that not only does the robot have to function in such an environment, it becomes difficult to service. It also means that the cold storage container has to be large, which is inefficient as energy must be expended keeping the robot at a low temperature, as well as the samples. 
     What is required is a storage apparatus which can pick an individual item from a high density container whilst minimising the exposure time of the surrounding items to higher temperatures. What is also required is a picking arrangement which takes up minimal space so it can be placed in the cold zone. 
     It will be noted that these requirements are apparent in any system where a plurality of items are stored at high density in a controlled environment, when exposure to ambient conditions may be hazardous to the integrity of the item. For example, this may be “clean” storage, storage in an inert gas, or “hot” storage such as an incubator instead of cold storage. 
     It is an aim of the present invention to provide a storage apparatus which can externally pick individual items from high density storage whilst minimising the exposure of the surrounding items to high temperatures, thus overcoming, or at least mitigating, the disadvantages of the prior art. 
     According to a first aspect of the present invention there is provided a storage apparatus comprising an array of item storage formations, a first member rotatable with respect to the array about a first axis, a selector mounted on the first member, the selector being rotatable with respect to the first member about a second axis, parallel to and offset from the first axis, the selector comprising an item transfer conduit offset from the second axis, in which the first member and the second member are configured for rotation about the first and second axes respectively to selectively align the item transfer conduit with one of the array of item storage formations to extract the item from the array. 
     By “transfer conduit” we mean a passage, conduit, bore or orifice through which items can pass. 
     Advantageously, the provision of such a system using an epicyclic selector provides fast access to an annular array of item storage formations. The fact that the first member and the selector are rotatable to position the transfer conduit makes them easier to seal against a tank wall. The epicyclic mechanism is also very compact compared to traditional Cartesian systems, which require a lot of space, and in particular extend outside the workspace (for mounting and actuating the rails or racks). 
     Preferably a temporary storage unit, or “catcher”, is mounted proximate the selector, the temporary storage unit defining a plurality of chambers for temporary storage of items. The temporary storage unit is preferably in communication with the transfer conduit on the opposite side of the selector to the tank, and is movably mounted relative to the selector to place the transfer conduit in communication with an individual one of the plurality of chambers. Advantageously, should the items stored in the volume be vertically stacked (i.e. parallel to the axes), the items on top of an item of interest can be extracted and stored in the temporary storage unit before the item of interest is extracted. The temporarily stored items can then be returned to the array. 
     Preferably the temporary storage unit is mounted for concentric rotation with the selector, and in which each of the plurality of chambers is disposed at the same distance from the second axis as the transfer conduit. This allows quick access to each of the chambers, and permits the item at the top of the stack to be quickly deposited in the catcher through the transfer conduit. 
     Preferably the chambers in the temporary storage unit are closed at one end by the selector when not in communication with the transfer conduit. Advantageously, this circumvents the need to provide some kind of clamp or catch to hold them in place. Each item will sit in its chamber until the chamber passes over the transfer conduit, at which point it may drop back into the array. 
     Preferably a low pressure source is used in fluid communication with the item transfer conduit to selectively suck items into the item transfer conduit from the array. The low pressure source is provided on the other side of the temporary storage unit to the selector such that the low pressure source selectively sucks items through the transfer conduit into the chamber in fluid communication with the transfer conduit. Advantageously, this means that mechanical engagement with each item or sample is not required. The fact that the system “sucks” the items from the volume also prevents the introduction of heat to the items by conduction, and instead surrounds them in cold air. 
     Because the low pressure source removes air from the volume, an aperture is provided to feed replacement air into the chamber. This air may be ambient (and then cooled by the cooling system of the tank) or pre-cooled using a refrigeration unit. 
     Preferably, the transfer conduit in the selector comprises an inlet seal, which seal bears against the array (or an array plate) of item storage formations. The seal preferably comprises an annular member rotatably (preferably spherically) mounted within the inlet. This allows the seal to better conform to, and form a substantially airtight seal with, the array plate. Preferably the seal forms a spherical joint with the selector, preferably via a part spherical surface engaging the inlet for this purpose. 
     Preferably an insulation layer is provided in the lid, and the temporary storage unit is positioned on the array side of the insulation layer. Preferably the first member comprises a first part of the insulation layer, and the temporary storage unit comprises a second part of the insulation layer, which first and second parts are adjacent to form a substantially contiguous insulation layer. 
     Advantageously, this keeps the temporarily stored items in the cold zone. 
     Turning to the array, it preferably comprises a plurality of elongate conduits parallel to the first and second axes, the selector being configured to selectively place each of the elongate conduits in communication with the transfer conduit or passage. The plurality of elongate conduits may be provided within pipes. Preferably the items are configured for axial sliding motion within the conduits or pipes. Samples can be “stacked” in the pipes. In order to maximise the available range of the system, preferably the array is annular about the first axis. 
     Preferably the array is annular about the first axis. 
     Preferably there is provided a plurality of items in the form of containers configured for axial sliding motion within the conduits. 
     Preferably the first member is rotatably mounted in a circular receiving formation of the tank, preferably in the tank lid or top plate. An annular running seal may be provided between the circular receiving formation and the first member. 
     The first member preferably comprises a layer of insulation material, which layer of insulation material defines a plurality of slits or recesses defined at least partially therethrough and facing the array. Because the layer of insulation is subject to a high temperature gradient (20 degrees ambient to minus 80 degrees inside the tank), thermally induced strains will try to develop, which could induce bending stresses in the first member. The slits allow the insulation to deform in small sections, reducing the bending stresses. 
     Preferably a separate access chamber is provided for the insertion and removal of items into and out of the array. This allows the picking mechanism to be sealed. Preferably the access chamber is in communication with a loading conduit which can be selectively placed in communication with the item receiving formation. Preferably the loading conduit forms part of the array. This allows the apparatus to load and unload items within its normal range of movement. 
     According to a second aspect of the invention there is provided a method of extracting an item from a storage apparatus comprising the steps of providing an array of items within a storage apparatus, providing a first member rotatable with respect to the array about a first axis, providing a selector rotatable with respect to the first member about a second axis, parallel to and offset from the first axis, the selector comprising an item transfer conduit, rotating the first member and the second member about the first and second axes respectively to align the item transfer conduit with an item to be extracted, using the selector to extract the item from the array. 
     As with the first aspect, the method uses an epicyclic selector to provide fast access to an annular array of item storage formations. The fact that the first member and the selector are rotated to position the item receiving formation makes them easier to seal against a tank wall. 
     Preferably the method further comprises the step of providing a low pressure source, using the low pressure source to suck the item into the item transfer conduit. 
     Further, the following steps are preferably part of the method providing a temporary storage unit, using the selector to extract multiple items from the array, temporarily storing the multiple items in the temporary storage unit, returning at least one of the multiple items to the array using the selector. 
     According to a third aspect of the invention, there is provided a suction apparatus for a storage apparatus comprising a conduit for the passage or storage of items, the conduit having an inlet, which suction apparatus comprises a seal member comprising a convex outer surface bearing against the conduit inlet to permit articulation of the seal member in use. Preferably, the convex outer surface is part spherical. The conduit may be provided with a part spherical concave formation to receive the seal member. Advantageously, this configuration allows the seal to better conform to the surface around orifices in an array in which items or samples may be stored, and thereby effect a better seal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An example storage apparatus in accordance with the present invention will now be described with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic section view of a first storage apparatus in accordance with the present invention; 
         FIG. 2  is a detailed schematic section view of a part of the storage apparatus of  FIG. 1 ; 
         FIG. 3  is a schematic plan view of a part of the storage apparatus of  FIG. 1 ; 
         FIG. 4  is a schematic side section view through the line IV-IV in  FIG. 3 ; 
         FIG. 5   a  is a schematic plan view, similar to  FIG. 3   a  but in a different position; 
         FIG. 5   b  is a schematic plan view similar to  FIGS. 5 and 5   a  but in a further different position; 
         FIG. 6   a  is a schematic plan view of a part of the storage apparatus of  FIG. 1 ; 
         FIG. 6   b  is a schematic plan view similar to  FIG. 6   a  in a different position; 
         FIG. 7  is a schematic section view through line VII-VII in  FIG. 6   a;    
         FIG. 8  is a perspective view of a second storage apparatus in accordance with the present invention, 
         FIG. 9  is a section view of the storage apparatus of  FIG. 8  through line IX-IX; 
         FIG. 10  is a perspective view of a part of the storage apparatus of  FIG. 8 ; 
         FIG. 11  is an exploded perspective view of the part of the storage apparatus of  FIG. 10 ; 
         FIG. 12  is a plan view of the part of the storage apparatus of  FIG. 10 ; 
         FIG. 13  is a side view of the part of the storage apparatus of  FIG. 10 ; 
         FIG. 14  is a side section view of the part of the storage apparatus of  FIG. 10  along the line XIV-XIV in  FIG. 12 ; 
         FIG. 14   a  is a detail view of a part of  FIG. 14 ; 
         FIG. 14   b  is a detail view akin to that of  FIG. 14   a , in a different configuration; 
         FIG. 15  is an exploded perspective view of a part of the storage apparatus of  FIG. 8 ; 
         FIG. 16   a  is a first side view of a part of the storage apparatus of  FIG. 8 ; 
         FIG. 16   b  is a second side view of the part of  FIG. 16   a;    
         FIG. 16   c  is a section view of the  FIG. 16   a  along lines C-C; and, 
         FIG. 17  is a section view of a third storage apparatus in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 1 , there is provided a storage apparatus  100  in accordance with the present invention. The storage apparatus  100  generally comprises a refrigerated tank  102 , a picking apparatus  104 , an access system  106 , and a refrigeration unit  108 . 
     The refrigerated tank  102  comprises a base  110  and an annular insulated side wall  112  in the form of a cylinder about a central axis  114 . The side wall  112  terminates in an annular shoulder  116  at an upper end, on which an array plate  118  sits. 
     The array plate  118  comprises a plurality of through bores arranged in an annular array formation about the axis  114 . Each of the through bores has a sample tube  120  installed therein, depending from the plate  118  such that each tube extends into the tank  102 . 
     Turning to  FIG. 2 , a series of three sample tubes  120  are shown in section. As can be seen, each example tube  120  contains sufficient space for the stacking of a plurality of sample containers  122  which are generally cylindrical in shape. It will be noted that each of the sample tubes  120  does not extend all the way to the base  110 , but instead stops short by a distance less than the length of a single sample container  122 , as shown in  FIG. 2 . This allows air to be replaced in each tube  120  when a sample is sucked out (described below), and also ensures that the position of the tubes  120  is determined by their alignment with the array plate  118 , to ensure they are all at the same level. The lack of contact with the bottom of the base  110  also insulates the sample tubes  120  and therefore the majority of the samples  120 . 
     Turning back to  FIG. 1 , an annular clamping ring  123  is placed over the periphery of the array plate  118  as shown in  FIG. 1  so as to secure it against the shoulder  116 . 
     The refrigerated tank  102  further defines a series of cooling channels  124  proximate the side wall inner periphery, which are cooled by the refrigeration unit  108  in order to maintain the temperature within the tank at a low level, typically minus 80 degrees Celsius. The tank  102  defines a volume  126  which is kept at this controlled temperature. 
     The picking apparatus  104  comprises a first member in the form of a tank lid  126 . The tank lid  126 , shown in more detail in  FIG. 4 , comprises a first cylindrical layer of insulating material  128  and a circular top plate  130 , having a radius larger than the insulating material  128 , and therefore projecting radially outwardly therefrom. The top plate  130  and insulating material  128  define a central axis  132 . Offset from the central axis  132 , a through bore  134  is defined having an offset axis  136  in the centre thereof. 
     Within the through bore  134  there is provided a cylindrical selector  138 , as shown in  FIG. 4 . The selector  138 , like the lid  126  comprises a layer of insulating material  140  and a top plate  142 , each of equal diameter about the offset axis  136 . A passage  144  is defined through the insulating material and top plate  140 ,  142 , and is parallel to, but offset from, both the main axis  132  and the offset axis  136 . 
     A catcher  146  is provided, as shown in  FIGS. 6   a  to  7 . The catcher  146  is generally circular and defines a plurality of chambers  148  in the form of through axial bores. The chambers  148  are disposed at an equal radius in a circular fashion about the centre of the catcher  146 . 
     A suction apparatus  150  (not shown in  FIG. 1 ) is also shown in  FIG. 7  and comprises a suction hose  152  connected to a vacuum source  154 , so as to selectively apply a negative pressure to the suction hose  152 . The suction hose  152  is rotatably mounted on an arm  156 . 
     The picking apparatus  104  is assembled as follows. 
     The tank lid  126  is installed in the open end of the refrigerated tank  102  above the array plate  118 . The tank lid  126  is sealed against the side walls  112  with the use of a ring seal  150 . The lid  126  can be rotated about the main axis  132  (which is coincident with the axis  114  of the tank). The lid  126  can be driven in rotation about the main axis  132  by the use of a motor  152  (in a known manner, the details of which will not be described here). 
     The lid  126  can therefore be rotated, for example, from the position shown in  FIG. 5   a  to that shown in  FIG. 5   b.    
     The selector  138  is installed for rotation about the offset axis  136  within the through bore  134  of the lid  126 . The selector  138  can also be driven in rotation about the axis  136  by a motor  154 . As such, the passage  144  can be positioned over any one of the annular array of bores defined in the array plate  118  by combined rotation of the lid  126  and selector  138  to access any of the sample tubes  120 . 
     Referring to  FIG. 3 , a 90 degree sector of the array of sample tubes  120  is shown by way of example. The selector  138  can be driven in rotation independent to the lid  126  by the use of the motor  154 .  FIGS. 3 ,  5   a  and  5   b  each show the selector  138  is different positions about the offset axis  136 . 
     The catcher  146  is mounted above the selector  138  for concentric rotation about the offset axis  136 . In this way, any of the chambers  148  can be aligned with the passage  144  by driving the catcher  146  in rotation, relative to the selector  138  about the offset axis  136 . 
     The motor  154  is arranged to drive the catcher  146 . A clutch is provided to selectively form a load path between the catcher  146  and the selector  138 . Therefore the catcher  146  and the selector  138  can be driven together (when the clutch is engaged) to position the passage  144  over the desired tube  120 . The clutch can be disengaged to rotate the catcher  146  relative to the selector  138  to then place the required chamber  148  in communication with the passage  144 . 
     The arm  156  is rotatably fixed to the selector  138  such that the two rotate together either side of the catcher  146 . Therefore the suction hose  152  is always aligned with the passage  144 . One of the chambers  148  is therefore usually in fluid communication with both the suction hose  152  and the passage  144 . 
     Negative pressure can be selectively applied by the vacuum pump  154 , thus sucking the top sample  122  from the sample tube  120  through the passage  144  and into the chamber  148 . The catcher  146  can then be rotated to place another chamber  148  in communication with the passage  144 . As the catcher  146  is rotated, the negative pressure in the chamber  148  containing the sample rises, releasing the sample, but by the time the sample drops from the hose  152 , the bottom of the chamber  148  is sealed by the top of the selector  138 . The sample  122  is therefore temporarily stored in the catcher  146 . 
     The next sample may then be extracted from the tube  120  aligned with the passage  144 . This process may continue until a target sample is stored within the catcher  146 . All of the samples  122  which were above the target sample can be quickly deposited back into the tube  120  by indexing the catcher  146  to release them under gravity from the chambers  148  through the passage  144  and into the tube  120  with the vacuum pump  154  deactivated. The end result is that only the target sample container is isolated within the catcher  146 . 
     In an alternative method, instead of temporarily storing each sample  122  in the catcher until the target sample is extracted, the picking apparatus may be used to deposit each sample above the target sample into an alternative tube  120  as they are picked. The apparatus picks a sample, deposits in a spare tube, moves back to the target tube, picks a further sample, deposits the further sample in the spare tube and so on until the target sample is extracted. In a preferred method, the catcher would hold a cache of 5 to 10 samples before depositing them in the spare tube. In this manner, the samples above the target sample are held at a high temperature for the shortest time possible. 
     The entire picking apparatus  104  is enclosed by an enclosure  156  which keeps it in a controlled environment. It is not envisaged that the enclosure  156  is set at a similar temperature to the refrigerated tank  102 , however, the environment will be controlled so as to minimise external factors affecting the samples temporarily held within the catcher  146 . In particular, the humidity of the air inside the enclosure  156  is controlled to make sure it is dryer than ambient to minimise degradation of the samples  122  temporarily held within the catcher  146 . 
     The lid  126 , catcher  146  and selector  138  can be operated at high speed in order to make the time which the samples are spent therein and in the environment of the picking apparatus  104  minimal. The lid  126 , selector  138  and the catcher  146  all have rotary encoders mounted thereon (not shown) which measure their rotation and allow a control system to accurately position them over the target tube  120 . 
     In order to keep the picking apparatus  104  isolated from the ambient environment, the access system  106  is provided. The access system  106  comprises an enclosure  158  having an access door  160  for the insertion and removal of samples. Samples can be added or removed on an XY tray  162  which is arranged to be actuated in X and Y directions within the access system  106 . After loading the XY tray  162 , the enclosure  158  is sealed and purged with an inert gas to expel ambient air and water vapour through a vent  165 . 
     A loading conduit  164  is provided above the XY tray  162 . The XY tray  162  can be can be moved to place any of the samples held therein directly adjacent the end of the conduit  164 . As shown in  FIG. 1 , the loading conduit  164  is routed through the refrigerated tank  102  and to the base of the array plate  108  where it forms part of the array of orifices (as indicated in  FIG. 3 ). 
     In this way, a target sample  122  temporarily stored in the catcher  146  can be released into the conduit  164  and thereby the tray  162  for removal by an operator. Similarly, a sample within the tray  162  can be added to the tank  102  by using the conduit  164  to suck it into the catcher  146  in the same way as the samples are removed from the tubes  120 . The picking apparatus  104  and samples can therefore be retrieved and deposited within the access system  106  as required. This ensures that there is minimal transfer of air from the exterior of the apparatus to both the picking apparatus  104  and the refrigerated tank  102 . 
     Turning to  FIGS. 8 to 15 , a more detailed storage apparatus  1000  is shown, operating in a similar manner to the storage apparatus  100 . 
     With reference to  FIGS. 8 and 9 , the apparatus  1000  comprises a refrigerated tank  1002 , a picking apparatus  1104 , an access system  1006 , and a refrigeration unit  1008 . The general configuration and operation of the apparatus  1000  is the same as the apparatus  100 . 
     Specifically, the tank  1002  defines a main axis  1118  and contains a plurality of sample tubes  1010  disposed in an annular array about the axis  1118 . An array plate  1014  holds them in place. The tank  1002  comprises a tank base  1021 , sidewalls  1018  and a lid  1020 . 
     Turning to  FIGS. 10 to 15 , the picking apparatus  1104  is shown in more detail. 
     The picking apparatus  1104  comprises a top plate  1106  which can be installed on the apparatus  1000  via downwardly depending pins  1108 . The top plate  1106  defines a circular orifice  1107  with roller assemblies  1120  positioned about the circumference. 
     The tank lid  1020  comprises a layer of insulating material  1022  with a circular plate  1110  positioned thereon. As with the apparatus  100 , the tank lid  1020  comprises a selector  1024  for relative rotation, as will be described below. The selector  1024  also comprises a layer of insulating material  1026  with a circular plate  1126  thereon. 
     The circular plate  1110  comprises an upwardly projecting rim flange  1112  and six radially extending stiffening ribs  1114 . The plate defines a hub  1116  at a main axis  1118 . A centre shaft  1188  projects upwardly from the hub  1116  in-line with the main axis  1118 . The centre shaft  1118  is freely rotatable with respect to the plate  1110 . The plate  1110  defines a circular orifice  1122  offset from the main axis  1118 , the orifice  1122  defining an offset axis  1124  parallel with the main axis  1118 . 
     The circular plate  1126  of the selector  1024  in section is shown in  FIGS. 14   a  and  14   b , with its centre at the offset axis  1124  (NB the insulation material  1026  is not shown in  FIG. 14   a ).  FIGS. 14   a  and  14   b  are shown at different positions of the lid  1020  about the main axis  1118 , and the selector  1024  about the offset axis  1124 . The plate  1126  defines a flange  1127  at its periphery, spaced from the axis  1124 . A circular orifice  1128  is positioned at a single location on the periphery of the plate  1126 . The plate  1126  defines a hub  1130 . A bearing layer  1132  is provided, covering an upper face of the plate  1126 . 
     A sample transfer tube  1166  is provided, and shown in detail in  FIGS. 16   a  to  16   c . The tube  1166  is cylindrical in form about a tube axis  2000  and having a central axial through-passage  1168 . At one end, the tube  1166  defines a radial flange  1170 . The diameter of the tube  1166  is less than that of the orifice  1128  in the plate  1126 . 
     The tube  1166  comprises a mount  2002  defining the flange  1170  and extending into a tubular section  2010 . The mount  2002  is connected to a middle tube  2004  via fasteners  2006 . The middle tube  2004  is partly surrounded by a sleeve  2008  which also lies within the tubular section  2010  of the mount  2002 . A bottom tube  2012  is provided extending from the mount  2002  and middle tube  2004 , but axially movable relative thereto against a resilient member in the form of a compression spring  2014 . The provides the tube  1166  with a variable length. The bottom tube  2012  defines a concave axial spherical surface  2030  at its lower end. 
     At the free end of the bottom tube  2012 , a seal member  2016  is provided. The seal member is formed from a low friction wear-resistant material suitable for sliding on the array plate  1014  and also on the spherical surface  2030  of the bottom tube  2012  at low temperatures. PTFE materials such as Rulon (RTM) are suitable for such an application. The seal member defines a truncated spherical portion  2018  about the axis  2000 , the spherical portion defining a spherical outer surface  2020 . Below the spherical portion  2018 , a cylindrical portion  2022  is provided defining an annular recess  2024  and a bearing surface  2025 . 
     A retainer wire  2026  is provided in the recess  2024 , as can be seen in  FIG. 16   b , the retainer wire  2026  extends up to the bottom tube  2012  to attach thereto around pins  2028  for retaining the seal member  2016  during assembly and removal from the lid  1020 . 
     As such, when the seal member  2016  is assembled with the bottom tube  2012 , it can rotate about any transverse axis because the spherical surface  2020  bears on the spherical surface  2030  of the lower end of the bottom tube  2012 . Therefore the seal  2016  can articulate without causing an air gap between it and the bottom tube  2012 . 
     A drive shaft  1134  is provided having a first end  1136  and a second end  1138 . 
     Turning to  FIGS. 11 to 15 , a catcher  1142  is provided, being generally circular about the offset axis  1124 . The catcher  1142  comprises a hub  1144  connected to a rim  1146  by eight spokes  1148 . A plurality of axially oriented chambers  1150  are provided in the rim  1146 . The chambers  1150  are positioned at the same radius from the offset axis  1124  as the orifice  1128  in the plate  1126 . 
     The hub  1144  defines a central shaft  1152 . 
     A suction assembly  1154  is provided comprising a radial arm  1156  having a hub  1158  at a first end and extending to a vacuum nozzle  1160  at a second end. The vacuum nozzle  1160  is in fluid communication with a hose adaptor  1162  configured for attachment to a hose (not shown) connected to a vacuum pump  1164 . 
     The picking apparatus is assembled as follows. 
     The circular plate  1110  of the tank lid  1020  is installed for rotation about the main axis  1118  in the top plate  1106  such that the rim flange  1112  can freely run on the rollers  1120 . An annular seal (not visible) prevents any flow of fluid between the top plate  1106  and the periphery of the circular plate  1110 . 
     The tank lid  1020  can be driven in rotation by an appropriately engaged first motor  1172  which drives the rim flange  1112 . 
     The sample transfer tube  1166  is installed within the orifice  1128  of the plate  1126  of the selector  1024  such that the flange  1170  abuts the top surface of the plate  1126 , flush with the bearing layer  1132 . The bearing surface  2025  of the seal  2016  can therefore run over the array plate  1014  to put the passage  1168  in selective communication with tubes  1010 . 
     The drive shaft  1134  is fixedly connected to the hub  1130  at the first end  1136 . The catcher is placed over the shaft  1134  and is connected thereto by a clutch arrangement  1174 , which will not be described in detail, but is configured to remotely engage and disengage the shaft  1134  with the hub  1144  of the catcher  1142 . 
     At the second end  1138  of the drive shaft  1134 , the hub  1158  of the suction assembly  1154  is fixedly attached, such that the selector  1024 , drive shaft  1134  and suction assembly  1154  all rotate together. The arm  1156  is oriented such that the vacuum nozzle  1160  is in-line with the passage  1168  of the sample transfer tube  1166 . 
     A second motor  1176  is arranged proximate the first motor  1172 , mounted to the top plate  1106  outside the periphery of the plate  1110  of the lid  1020 , such that the motor  1176  is static relative to the rotating lid  1020 . 
     A belt arm  1178  extends from the second motor  1176  to above the centre shaft  1188 , extending above the catcher  1142 . An output shaft  1180  of the motor  1176  has a pulley  1182  defined thereon. The centre shaft  1188  also has a pulley  1183  defined thereon. A belt tensioner  1184  is provided on the belt arm  1178 . A drive belt  1186  is provided to transfer torque from the pulley  1182  to the pulley  1183 , and is tensioned by the tensioner  1184 . As such, the motor can drive the centre shaft  1188  in rotation. 
     A first gear  1190  is also mounted to the centre shaft  1188 , and via an intermediate gear  1192  with a high friction periphery is arranged to drive the rim  1142  of the catcher  1142 . The second motor  1176  can thereby drive the catcher  1142 , the selector  1024  and the arm  1156  via shaft  1134  and the clutch arrangement  1174  (when engaged) in rotation about the offset axis  1124 . The fact that the drive from the second motor  1176  passes through a drive element in the form of pulley  1183  concentric with the tank lid  1020 , means that the motor can be mounted on the tank  1002  rather than on the moving lid  1020 . This reduces the power requirement of the first motor  1172 , and makes the system less complex. 
     In operation, the lid  1020  is rotated by the first motor  1172 . The catcher  1142  and selector  1024  are then rotated by the second motor  1176  to position the passage  1168  over a target sample tube  1010  in the array. The axial compliance and resilience of the tube  1166 , and the rotational degree of freedom of the seal  2016  mean that a good seal is always formed with the array plate orifices. 
     If required, the clutch arrangement  1174  is then disengaged and the catcher  1142  rotated to place an empty chamber  1150  between the vacuum nozzle  1160  and the passage  1168 . The vacuum pump  1164  can then be used to suck a sample into the chamber  1150 . The catcher  1142  is then indexed and the pump  1164  deactivated, such that another (empty) chamber  1150  can be aligned with the passage  1168 . A further sample can then be captured. 
     The samples in the catcher  1142  can be deposited back into the tank by indexing the catcher  1142  with the pump  1164  deactivated so they fall under gravity. 
     It will be understood that the various subsystems not specifically described with respect to the apparatus  1000  work in substantially the same manner as the apparatus  100 . 
     Turning to  FIG. 17 , a selector and catcher assembly of a further storage apparatus in accordance with the present invention is shown in section. The apparatus is similar to that of  FIGS. 8 to 16   c . The main difference is that the selector, and the part of the catcher which temporarily holds the samples is placed within the cold zone of the tank. 
     A tank lid  3020  comprises a layer of insulating material  3022  with a circular plate  3110  positioned thereon. The lid  3020  covers an array plate  3014  supporting a number of sample tubes  2120 . As per the apparatus  1000 , the array plate  3014  has a bore leading to a picking apparatus (not shown). 
     Unlike apparatus  1000 , instead of the selector being integrated within the thickness of the lid, and the catcher positioned above, a catcher  3142  is integrated within the thickness of the lid  3020 , and is arranged to rotate about an offset axis  3124 . The catcher  3142  is generally circular about the offset axis  3124 . 
     The catcher  3142  comprises a circular drive gear  6000  having a plurality of fluid channels  6002  at its periphery. 
     Adjacent and below the drive gear  6000 , there is provided an insulation layer  6004  having a plurality of fluid channels  6006  corresponding to each of the channels  6002  in the drive gear  6000 . The insulation layer is arranged to fit within a circular orifice  6001  of the insulation  3022  such that a continuous insulation layer is formed across the top of the tank. 
     Adjacent the insulation layer  6004  on the opposite side to the drive gear  6000 , i.e. on the tank side of the insulation layer  6004 , a catcher body  6008  is provided having a plurality of axially oriented chambers  3150  at its periphery. Each chamber  3150  is in fluid communication with one of the fluid channels  6006  and the channels  6002 . The channels  6006  in the insulation  6004  are of a smaller diameter relative to the chambers  3150  in the catcher body  6008  so as to form a shoulder  6010 . Each chamber  3150  is dimensioned to hold a sample container  6012 , and the shoulder  6010  prevents sample containers from entering the channels  6006  when a negative pressure is applied to the channel  6002 . 
     The drive gear  6000 , insulation  6004  and catcher body  6008  are attached together and rotatable about the offset axis  3124 . The drive gear  6000  comprises an exposed gear formation  6014  for driving by an appropriate motor (not shown). 
     It will be noted that the thickness of the insulation layer  6004  extends within the thickness of the insulation  3022  of the lid  3020 . Therefore the catcher body  3008 , including the chambers  3150  in which the sample containers  6012  are temporarily stored are kept at the same temperature as the refrigerated container below. Effectively, the catcher has been moved into the cold zone to maintain the samples at a low temperature. 
     The selector  3024  comprises a flat plate  3126  having a bore  3116  containing a sprung seal  6016 . The sprung seal  6016  comprises two opposing seal members  6018 ,  6020  which are resiliently biased away from each other are each similar to the seal member  2016 . The upper seal member  6018  is resiliently biased towards the bottom of the catcher body  6008  in use, and the lower seal member  6020  is resiliently biased against the array plate  3014  in use. 
     A suction assembly  3154  is provided similar to that of the apparatus  1000 , comprising a radial arm  3156  having a hub  3158  at a first end and extending to a vacuum nozzle  3160  at a second end. The vacuum nozzle  3160  is in fluid communication with a hose adaptor  3162  configured for attachment to a hose (not shown) connected to a vacuum pump (not shown). 
     The suction assembly  3154  and the selector  3024  are connected by a shaft  6022 , which is rotatable about the offset axis  3124  and passes through the main axis of the catcher  3142 . The nozzle  3160  and the bore  3116  are always aligned. 
     A clutch  6024  is provided between the driven catcher  3142  and the shaft  6022 , such that as per the apparatus  1000 : 
     (i) the catcher  3142  can be driven in isolation (thus incrementally presenting a new chamber  3150  to the selector  3024 ) with the clutch  6024  disengaged, or; 
     (ii) the catcher  3142  can be driven with the selector  3024  and suction assembly  3154  to move over a new part of the array plate  3014  with the clutch  6024  engaged. 
     In operation, if a sample from one of the tubes  2120  is to be extracted, the lid  3020  is rotated about the main axis (not shown) and the drive gear  6000  of the catcher  3142  is driven in rotation about the offset axis  3124  with the clutch  6024  engaged until the bore  3116  is over the target tube. A negative pressure is applied at the adaptor  3162  to suck a sample into the chamber  3150 . The clutch  6024  is then disengaged and the catcher  3142  rotated (without moving the selector  3024 ) to expose an empty chamber  3150 . A further sample is then sucked into the chamber and the process repeated until the target sample can be retrieved. 
     The temporarily stored samples can then be returned to the tank. It will be noted that at all times the temporarily stored samples have been inside the cold zone. 
     Variations fall within the scope of the present invention. 
     The picking apparatus may be held at a temperature between ambient and the tank  102  (for example minus 20 degrees Celsius) to minimise degradation of the samples temporarily held therein. 
     The second motor  1176  may be mounted on top of the tank lid  1020 . Although increasing the inertia of the lid, this may increase the accuracy of positioning of the catcher and selector. 
     The storage container may contain high temperature environment. In this case, it is desirable to minimise the time at which the samples are kept at a lower temperature.