Abstract:
Apparatus is described for loading or unloading a vessel, say a flask, on to or from a selected position on a support arranged to oscillate substantially in a plane. The apparatus includes a transporter in the form of a robotic arm having a gripper unit for gripping the flask. A mechanism, preferably a flexible restraint mechanism, is arranged to accommodate lost movement between the transporter and the support when the gripper unit releases or grips the flask to load it on to or unload it from the support respectively.

Description:
BACKGROUND TO THE INVENTION  
       [0001]     The present invention relates to apparatus and methods for loading and unloading cell culture vessels and the like (eg, Erlenmayer flasks) on to or off an oscillating support such as found in a cell culture system incubator.  
         [0002]     For use in incubators, platform shakers are often used, providing one or more trays or shelves on which cell culture vessels can be placed within the incubator, the trays or shelves being capable of being independently shaken in an oscillating manner.  
         [0003]     In our EP application no. 04254885.9 we describe an incubator, for example for a cell culture system, the incubator being arranged to handle a plurality of vessels and including a rotatable support defining a plurality of support locations for vessels at predefined positions around an upright axis and being rotatable around the upright axis to move the vessels between a number of positions about the axis; a drive transmission system for connecting the support to a drive motor, whereby the support can be rotated to a desired position for loading or unloading of a vessel to or from a respective support location; and a drive mechanism operable to move each support location eccentrically about an axis independently of the rotation of the support about the upright axis, whereby vessels disposed on the support can be shaken.  
         [0004]     It is desirable to avoid starting and stopping the shaking/oscillation of the vessel support(s) in an incubator of such a type, or of other common type, where the or each support holds a number of vessels which are shaken together. In this context, the term ‘oscillation’ includes orbital motion as well as reciprocal motion in a single dimension. Not only does frequent starting and stopping reduce the actual time spent shaking the contents of all the vessels on the support unpredictably, ie. especially those which otherwise are not being unloaded or unloaded, but it also adds wear to the driving mechanism.  
       SUMMARY OF THE INVENTION  
       [0005]     According to the present invention there is provided for loading or unloading a vessel on to or from a selected position on a support arranged to oscillate substantially in a plane, the apparatus including  
         [0006]     a transporter having a gripping mechanism for gripping a vessel to hold the vessel; and  
         [0007]     a mechanism arranged to accommodate lost movement between the transporter and the support when the gripping mechanism releases or grips the vessel to load it on to or unload it from the support respectively as said support oscillates.  
         [0008]     Such an apparatus allows vessels to be loaded and unloaded without stopping the oscillation of the support (or the supports if there are multiple supports oscillating together, eg. driven by the same drive mechanism).  
         [0009]     The mechanism arranged to accommodate lost movement between the transporter and the support is preferably mounted on the support at the selected position and may be a flexible restraint mechanism. Such a flexible restraint mechanism may include a plurality of spring elements disposed to surround the support to engage and hold a vessel when it has been loaded on to the support. The flexible restraint mechanism is preferably arranged to hold the lower end of a vessel.  
         [0010]     Alternatively or additionally, the mechanism arranged to accommodate lost movement between the transporter and the support may include a mounting plate on the support arranged to support a vessel directly, the mounting plate being flexibly mounted for limited movement substantially parallel with the planar oscillating movement of the support. Preferably a means for holding the mounting plate in fixed position during loading or unloading of a vessel is provided.  
         [0011]     The mechanism arranged to accommodate lost movement between the transporter and the support may alternatively be mounted on the transporter, preferably on the gripping mechanism.  
         [0012]     The gripping mechanism may be arranged to synchronise at least partially with the oscillatory movement of the support during loading or unloading.  
         [0013]     Preferably the transporter includes a robot with a robotic arm carrying the gripping mechanism.  
         [0014]     The invention also includes a method of loading or unloading a vessel on to or from a selected position on a support oscillating substantially in a plane, using a transporter having a gripping mechanism for gripping a vessel to hold the vessel, the method comprising  
         [0015]     in the case of loading, engaging the vessel with a mechanism arranged to accommodate lost movement between the transporter and the support and thereafter releasing the vessel from the gripping mechanism whereby the vessel is released on to the support; and,  
         [0016]     in the case of unloading, gripping the vessel by the gripping mechanism to remove the vessel from the support, the movement of the gripper mechanism relative to the support being accommodated by the mechanism to accommodate lost movement between the transporter and the support. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     Two examples of apparatus according to the present invention will now be described in reference to the accompanying drawings, in which:  
         [0018]      FIGS. 1A &amp; 1B  are plan and side views respectively of an incubator as described in our EP application no.  04254885 . 9 ;  
         [0019]      FIG. 2  is a perspective view of a part of an incubator flask support;  
         [0020]      FIG. 3  is perspective view of part of a second support; and  
         [0021]      FIG. 4  is a perspective view similar to  FIG. 2 , but additionally showing a gripping mechanism. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     The incubator  1  shown in the drawing includes a housing  4  in order to enable a controlled environment to be maintained and adjusted. The incubator housing  4  includes a slidable access panel or door  41  through which a transporter in the form of a robotic arm  2  with a gripper unit  20  may be extended to load/unload culture vessels (Erlenmayer flasks)  50 . On the opposite side, the housing has an operator access door  42 . The robotic arm  2  is shown, in  FIG. 1 , in both a top  2 A and a bottom  2 B position to show the range of vertical movement possible. For simplicity further details of the housing of the incubator are not shown in the drawings. The griper unit is shown in more detail in  FIG. 4  as described below.  
         [0023]     The incubator  1  includes a plurality of rotatable supports  10  in the form of pairs of rotatable rings  11 ′,  11 ″ defining, around their common axis, a series of support locations  12  for the culture vessels or flasks  50  in what is, effectively, a carousel  3 . The vessels or flasks  50  may be of different sizes as shown on the different supports  10 .  
         [0024]     The plural inner rings  11 ′ are fixed for movement together as are the plural outer rings  11 ″. Upright frame elements  31  extend between adjacent rings  11 ′,  11 ″ to support one above another for movement together. The lowest support  10  includes a bearing  32  which allows the inner ring  11 ′ to rotate within the outer ring  11 ″, carrying with it the rings disposed above it. A first drive shaft  33  is driven through a transmission  34  by a motor  35  to rotate the inner set of rings  11 ′ of the carousel  3  for loading/unloading of culture vessels or flasks  50 . A second, tubular, drive shaft  39  surrounds the first drive shaft  33  and is driven through a transmission  37  by a motor  36  to rotate the outer set of rings  11 ″ of the carousel  3  for loading/unloading of culture vessels or flasks  50 . The drive shafts  39  and  33  are supported on respective bearings  39 ′,  33 ′ on upper and lower supporting bracket members  38 ,  38 ′ respectively.  
         [0025]     A bellows type flexible seal  43  seals the bottom of the housing  4  allowing the drive mechanisms and motors to be disposed in a separate, lower housing  5  disposed below and supporting the incubator  4 . This separation simplifies the task of maintaining the required conditions within the incubator  1 .  
         [0026]     To shake or vibrate culture vessels or flasks  50  disposed on the supports  10  in the carousel  3 , a drive motor  60  is connected via a pulley  61  to a drive belt  62  which is also passed around eccentrically mounted pulleys  63 ,  64  fixed on the underside of the top member  51  of the lower housing  5  and having respective eccentrics  65 , 66  attached to the upper support bracket member  38  to support the flask supports  10  for eccentric movement relative to the incubator housing  4  under the action of the motor  60 .  
         [0027]      FIG. 2  shows a modification of the system of  FIG. 1  (in accordance with the present invention) and, in particular, part of an incubator flask support  10  (as shown in  FIGS. 1A &amp; 1B ), which moves, in use, in an orbital motion to shake flasks mounted on it as described above. Each support  10  provides a plurality of support locations  12  for flasks  50  as seen in  FIGS. 1A &amp; 1B  (only one of which is shown in  FIG. 2 ). At each location  12  (only one of which is shown in  FIG. 2 ) a mounting plate  13  is provided on which the flask  50  is supported in use. Each mounting plate  13  is supported on the incubator support  10 , on each side, between retaining brackets  14  (only two of which are shown) fixed to the top surface of the support  10  and is allowed to move parallel to the plane of the support, against the action of springs  15  carried between posts  15 A &amp;  15 B on the support  10  and the mounting plate  13  to accommodate the oscillatory action of the support  10  and the lost motion arising therefrom between the support and the robotic arm  2  (not shown in  FIG. 2 ).  
         [0028]     The mounting plate  13  carries a spring type clip-in holder  16  by means of which a flask  50  can be held in place on the mounting plate, the flask being pushed on to the plate between the spring clips  16 A of the holder  16  and removable therefrom by lifting up between the clips under the controlled action of the gripper unit  20  of the robotic arm  2 .  
         [0029]     In order to allow a flask  50  to be loaded or unloaded, the mounting plate  13  can be held stationary above the support  10  (while the support continues to be oscillated) by means of an arm  17  on the mounting plate  13  which is clamped by a solenoid actuated clamp  18  when desired, the clamp being mounted and held stationary on a fixed, stationary, part of the incubator such as the housing or frame. An alternative, not shown, is for the robotic arm  2  to include a clamp or other mechanism to engage with the mounting plate  13  or a bracket or arm  17  attached to it to hold the mounting plate in fixed position.  
         [0030]      FIG. 3  shows an alternative construction for each support location  12  (only one of which is shown). The support location  12  has a flexible restraint mechanism in the form of three leaf-spring arms  19  arranged in a substantially triangular arrangement on the support  10  providing flexibility to accommodate loading or unloading of a flask, the arms flexing as a flask is loaded or unloaded by the gripper unit  20 . Preferably the gripper unit  20  tilts the flask  50  to ease loading or unloading. The leaf-spring arms are supported on fixed posts  28  and pre-loaded against abutments  29  to ensure sufficient clamping as soon as a flask is inserted between the arms.  
         [0031]     In an alternative construction, not shown, the examples of  FIGS. 2 and 3  can be combined, the spring clip holder  16  of  FIG. 2  being replaced by the spring-loaded arms  19  of  FIG. 3 .  
         [0032]     In a further development or modification as illustrated by the arrowed oscillatory paths A and B in  FIG. 4 , the movement of the gripper unit  20  can be synchronised to the oscillating motion of the support  10  during the loading or unloading process so that the motion of the gripper unit  20  to move the flask into or out of the support location is then a simple component of movement (in two dimensions parallel to the plane of the support  10 ) relative to the support, the gripper unit  20  also tilting the flask as required under the action of the robotic arm  2 . In practice, even with synchronism between the gripper unit  20  and the support  10 , complete synchronism may not be achieved, so that it remains necessary to compensate for any remaining lost movement as described above.  
         [0033]     The gripper unit  20  is mounted via a conventional robotic ‘wrist’ unit  24  on the end of the robotic arm  2 . The wrist  24  allows rotational movement of the gripper unit  20  about two orthogonal axes. The gripper unit includes a pair of translating jaws  21 , 22  movable under the action of a linear pneumatic drive motor mechanism  23  to open and close so as to grip or release the grip on a flask  50 . The motion of the gripper unit  20  can be matched to that of the flask before the gripper is lowered down on to the flask. This may be achieved by using, for example, an inductive sensor (not shown) to sense the motion of the support  10  and provide a signal to the controller of the robotic arm  2  to cause the motion of the end mounting the gripper unit  20  to move synchronously with the support. Allowance for signal processing time may need to be taken into account in order to avoid the movement of the gripper unit  20  being out of phase with that of the support  10 . In a typical case the oscillation of the support has an amplitude of about 25 mm.