Abstract:
A freeze dryer comprises a chamber having a rectangular slot through which vials are inserted into the chamber. An assembly for loading and/or unloading the chamber comprises a transfer bar extending across the slot. The bar is pivotally attached at each end to first and second flat springs, each spring being wound on a respective rotatably mounted spool located proximate the slot. Drive means are provided for synchronously rotating the spools to effect movement of the bar into or out from the chamber and for selectively rotating the spools to raise or lower the bar.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an assembly for loading and/or unloading a freeze dryer or the like. 
     BACKGROUND OF THE INVENTION 
     Freeze dryers typically incorporate a pressure vessel having a freeze drying chamber for receiving a plurality of containers or vials typically containing sterile material to be freeze dried. Access to the chamber for automated loading and removal of vials is through a rectangular opening, or slot, formed in a wall or in the main door of the chamber. The slot is closed by a slot door which, with the chamber, forms a vacuum seal around the slot. 
     To enable vials to be inserted into the chamber, the slot door is vertically raised relative to the slot by moving the slot door along guide tracks. A loading mechanism provided opposite the slot door pushes vials from a conveyor on to a shelf of the chamber. The vials may be loaded row by row on to a shelf, a number of rows at a time, or a complete shelf full at a time. The loading mechanism is subsequently withdrawn and the slot door closed to enable the contents of the vials to be freeze dried. The vials can be subsequently removed from the chamber, typically in the same manner (row by row or shelf by shelf) as they were loaded into the chamber, using an unloading mechanism. 
     Pharmaceutical freeze dryers are usually at least partially housed in a clean room, with the loading and unloading mechanism being located in a sterile environment, for example an isolator, adjacent the clean room environment. The size of these loading and unloading mechanisms can contribute greatly to the overall size of the foot-print of the freeze dryer. As the cost of maintaining the sterile environment generally increases with size, conventional loading and unloading mechanisms, typically requiring around 2 m 2  and 1 m 2  of floor space respectively, can significantly increase running costs. Whilst locating part of these mechanisms outside of the isolator can assist in reducing the size of the foot-print within the isolator, parts moving into the sterile environment from outside would require sealing, using a bellows or the like, to maintain sterile conditions within the isolator. Furthermore, those parts of an unloading mechanism which are permanently housed within the chamber, such as a push bar for pushing the vials back on to the conveyor, must be able to withstand conditions prevailing within the chamber during use of the freeze dryer. 
     SUMMARY OF THE INVENTION 
     An embodiment of the present invention is to provide a mechanism for loading and/or unloading a freeze dryer which can significantly reduce the size of the overall foot-print of the freeze dryer and which can be readily incorporated within a sterile environment. 
     In a first aspect, the present invention provides an assembly for loading vials into and/or unloading vials from a chamber of a freeze dryer or the like, the assembly comprising a transfer bar for engaging vials to effect movement thereof, and means for moving the bar, characterised in that the moving means comprises first and second pairs of coils of elongate resilient members, means for connecting the coils to the transfer bar such that the transfer bar is pivotally attached at each end thereof to a respective pair of coils, and drive means for synchronously unwinding the coils to effect lateral movement of the bar and for selectively winding or unwinding one of the coils of each pair relative to the other to raise the bar. 
     The invention can thus provide a compact assembly for unloading vials from, or both loading vials into and subsequently unloading the vials from the same side of, a chamber of a freeze dryer. As the assembly can be readily incorporated within a sterile environment of, for example, an isolator, the use of bellows or other such mechanisms can be eliminated. Furthermore, enabling the freeze dryer to be both loaded and unloaded using apparatus provided on one side only of the dryer can significantly reduce the overall size of the foot-print of the freeze dryer. 
     The drive means preferably comprises means for rotating synchronously each pair of coils to effect lateral movement of the bar, and means for selectively effecting relative rotational movement between the coils of each pair to raise the bar. For example, each coil may be wound on a respective spool, with the drive means being arranged to rotate the spools to move the bar. The coils are preferably retained on the spools by a plurality of rollers extending about the spools, which rollers can further serve to guide the spools as they are unwound to effect movement of the bar. Further guide means may be provided in the form of slots located on either side of the transfer bar, the free end of each coil being located within a respective slot. These slots may be fixed, or may be at least partially selectively moveable between deployed and stowed positions. For example, parts of the slots within the chamber may be retracted when the transfer bar has been withdrawn from the chamber to enable a shelf of the dryer to be raised or lowered, for example, to enable another shelf to be loaded or unloaded as required. 
     The connecting means preferably comprises first and second connecting members each attached to a respective end of the transfer bar and extending substantially orthogonal to the transfer bar, with a first coil of each pair being attached to a connecting member via a first linking member, and a second coil of each pair being attached to a connecting member via a second linking member. Each first coil is preferably rigidly attached to a respective first linking member, with each first linking member being pivotally attached to a respective connecting member. Each second coil is preferably rigidly attached to a respective second linking member, each second linking member being pivotally attached to a respective connecting member via a respective arm pivotally attached to both the second linking member and the connecting member. This can enable the second coils to be wound or unwound relative to the first coils to effect raising of the bar. 
     A surface of the transfer bar preferably has a first shoulder for stabilising vials engaged thereby during loading of the chamber, and a second shoulder for stabilising vials engaged thereby during unloading of the chamber. 
     Each elongate member preferably comprises a resilient band, for example a flat spring. 
     In a second aspect, the present invention provides a freeze dryer comprising a chamber and an assembly as aforementioned for loading vials into and/or removing vials from the chamber, preferably through a slot provided in a wall of the chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred features of the present invention will now be described with reference to the accompanying drawings, in which: 
         FIG. 1  is a plan view of a first embodiment of a freeze dryer; 
         FIGS. 2(   a ) and ( b ) illustrate respective arrangements of vials prepared for loading into the freeze dryer of  FIG. 1 ; 
         FIG. 3  is a perspective view of part of an assembly for loading vials into and/or unloading vials from the freeze dryer of  FIG. 1 ; 
         FIG. 4  is a cross-section through part of an assembly for loading vials into and/or unloading vials from the freeze dryer of  FIG. 1 , with the transfer bar in a lowered position; 
         FIG. 5  is a top view of the part of the assembly shown in  FIG. 4 , with the transfer bar in a raised position; 
         FIG. 6  is the same perspective view of  FIG. 3 , showing the guide members  82  in a deployed position; 
         FIGS. 7(   a ) to ( d ) are side views of the transfer bar of the assembly in respective different positions during the loading and unloading of vials from the freeze dryer; 
         FIGS. 8(   a ) to ( i ) are a sequence of perspective views of the assembly during the unloading of vials from the freeze dryer; and 
         FIG. 9  is a plan view of a second embodiment of a freeze dryer. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , a freeze dryer  10  comprises a chamber  12  (extending orthogonally relative to the plane of  FIG. 1 ) having a slot (not shown) formed in the front wall of the chamber  12  to enable vials to be loaded on to and unloaded from a shelf  14  in the chamber  12 . The slot can be closed by a slot door  16  moveable relative to the chamber  12 . The chamber  12  includes a number of shelves  14 , each of which can be raised and lowered within the chamber  12  using a shelf location mechanism (not shown). To load the shelves, the shelves are initially collapsed in the lower portion of the chamber, and the uppermost shelf is first moved into a loading position. After that shelf has been loaded, the mechanism automatically raises the loaded shelf to enable the next shelf to be moved to the loading position. This moving sequence continues until the chamber loading has been completed. To unload the chamber, the loading sequence is reversed, with the lowermost shelf being unloaded first. 
     An assembly for loading and unloading the chamber  12  is formed from several modules supported by a supporting frame located in an isolator cabinet  18 . The assembly enables automated loading of the freeze dryer  10  with vials received from a filling machine, and automated unloading of those vials from the freeze dryer for subsequent conveyance to a capping machine. 
     The supporting frame is bolted to the frame of the freeze dryer  10 , and to the floor of the isolator. The supporting frame is formed from strong stainless steel plates. Within the isolator  18 , the external surfaces of the supporting frame and the modules of the assembly for loading and unloading the chamber are designed so as to be readily accessible for cleaning and sterilising in situ using, for example, vaporised hydrogen peroxide. 
     The modules of the assembly for loading and unloading the chamber  12  will now be described. 
     An in-feed conveyor  20  collects the vials coming from a filling machine (not shown) located outside the isolator and conveys the vials to an in-feed star wheel  22  mounted on the supporting frame. Appropriate guiding ensures a smooth transition between the in-feed conveyor  20  and the in-feed star wheel  22  with correct feeding of the in-feed star wheel  22 . For small vials subject to tipping, a mechanical reject system may be provided upstream from the in-feed star wheel  22  to reject fallen vials. The in-feed conveyor  20  is driven by a motor located beneath the supporting frame. 
     The in-feed star wheel  22  serves to position the vials received from the in-feed conveyor on to a pusher conveyor  24 . The in-feed star wheel  22  and the pusher conveyor  24  are driven by respective servomotors located beneath the supporting frame. The rotational speed of the in-feed star wheel  22  can be synchronised with the speed of the pusher conveyor  24 . Control of the starting, acceleration, deceleration and stopping of the in-feed star wheel  22  relative to the pusher conveyor  24  can be used to convey the required number of vials on to the pusher conveyor  24  and to control the pitch of those vials. 
     A loading pusher  26  pushes vials from the pusher conveyor  24  on to an accumulation table  28 . As shown in  FIG. 2(   a ), the movement of the in-feed star wheel  22  and pusher conveyor  24  can be controlled so that each row of vials accumulated on the pusher conveyor is laterally displaced from the previous row by an amount equal to one half of the vial width. This can enable close packing of the rows of vials on the accumulation table  28 . As shown in  FIG. 2(   b ), when loading two separate vial packs on a wide shelf  14  the in-feed star wheel  22  can form in the rows of vials a gap in the middle of the row of width equivalent to the width of a shelf guide  30 . With reference to  FIG. 1 , the loading pusher  26  comprises a pusher bar  32  and a motorised actuating mechanism  34  connected to the pusher bar  32  for moving the pusher bar  32  towards the chamber  12  to push a row of vials on to the accumulation table  28  and for subsequently retracting the pusher bar  32  to enable another row of vials to be accumulated. For cold shelf loading, the pusher bar  32  may be provided with a mechanism for actuating a safety bar  36  that prevents vials from falling as they are pushed on to the accumulation table  28 . 
     The accumulation table  28  is a fixed plate located adjacent the pusher conveyor  24  and forms part of a bridge plate module which enables vials to be transferred from the pusher conveyor  24  on to the shelf  14  to be loaded. The bridge plate module further includes a bridge plate  38  and an intermediate plate  40 . 
     As shown in  FIG. 3 , the intermediate plate  40  is located within the freeze dryer chamber  12  at the same level as the loading position for the shelves  14 , and can be automatically moved horizontally away from a filled, or emptied, shelf  14  at the loading position to enable that shelf to be raised, or lowered, within the chamber  12 . The shelves may be provided with means, such as dowels or the like, which engage corresponding holes or recesses in the intermediate plate  40  to ensure accurate horizontal alignment between a shelf  14  and the intermediate plate  40  as a shelf is maneuvered into the loading position. 
     The bridge plate  38  is located between the accumulation table  28  and the intermediate plate  40 . The bridge plate  38  can be rotated from the stowed, raised position shown in  FIG. 3  relative to the accumulation table  28  and the intermediate plate  40  so that part of the bridge plate  38  extends into the chamber  12  through the slot to enable the bridge plate  38  to register and align horizontally both with the intermediate plate  40  within the chamber  12  and with the accumulation table  28  outside the chamber  12 . The bridge plate  38  and intermediate plate  40  have profiled edges that mate together as the bridge plate is rotated into location with the intermediate plate  40 . A mechanism for rotating the bridge plate  38  and moving horizontally the intermediate plate  40  is located beneath the bridge plate  38 . Rotation of the bridge plate  38  back to the raised position can enable the slot door  16  to be closed. 
       FIG. 3  also shows a transfer bar  42  of the assembly, which, in the embodiment shown in  FIG. 1 , serves to unload the chamber  12 . The transfer bar  42  extends substantially the width of a shelf  14 , and is connected at each end to a reel assembly  44  for effecting movement of the transfer bar  42  into and out from the chamber  12 , and for raising and lowering the transfer bar  42 . Each reel assembly  44  comprises two stainless steel spring upper and lower ribbons  46 ,  48 . Each upper (as shown in  FIG. 4 ) ribbon  46  is wound around an upper drum  50 , and each lower ribbon  48  is wound around a lower drum  52 , the upper and lower drums  50 ,  52  of each reel assembly  44  being co-axial. With reference also to  FIG. 5 , the ribbons  46 ,  48  are retained on the drums by rollers  54  extending about the drums  50 ,  52  and depending from a mounting plate  56  connected to a drive shaft  58  by a fixing member  60 . 
     The free ends of the ribbons  46 ,  48  of each reel assembly  44  are connected to the transfer bar  42  via a connecting member  62  attached to the transfer bar  42  and extending substantially orthogonal therefrom. The free end of the lower ribbon  48  is rigidly attached to a first linking member  64 , the first linking member  64  being pivotally attached to the connecting member  62  via pivot  66 . The free end of the upper ribbon  46  is rigidly attached to a second linking member  68 . The second linking member  68  is pivotally attached to a linking arm  70  via pivot  72 , the linking arm being in turn pivotally attached to the connecting member  62  via pivot  74 . 
     Movement of the first and second linking members  68 ,  64  as the coils are unwound from the drums is guided by guide members  76 ,  78 ,  80 ,  82  located on each side of the transfer bar  42 . Each guide member comprises upper and lower slots, movement of the first linking member  68 , and thus the free end of the upper ribbon  46 , being guided by the upper slots and the movement of the second linking member  64 , and thus the free end of the lower ribbon  48 , being guided by the lower slots. Guide members  76  are attached to the sides of the accumulation table  28 , guide members  78  are attached to the sides of the bridge plate  38 , and guide members  80  are attached to the sides of the intermediate plate  40 . In this embodiment, guide members  82  are moveable between a stowed position, shown in  FIG. 3 , where they are spaced from the shelf  14  to allow the shelf  14  to be raised or lowered within the chamber  12 , and a deployed position, shown in  FIG. 6 , where the guide members  82  are co-linear with the guide members  80 . Alternatively, the guide members  82  may be fixed. The guide members  76 ,  78 ,  80  and  82  also serve to guide the rows of vials as they are loaded into, and unloaded from, the chamber  12 . 
     The drive shafts  58  of the reel assemblies  44  are connected to a common servomotor located beneath the supporting frame  18 . Each drive shaft  58  is connected directly to the upper drum  50  of the respective reel assembly  44 , the drums  50 ,  52  being configured such that rotation of the upper drum  50  causes both drums  50 ,  52  of the assembly  44  to be rotated synchronously. This enables the upper and lower ribbons  46 ,  48  to be simultaneously unwound from, or wound on to, the drums  50 ,  52  to move the transfer bar  42  into, or out from, the chamber  12  as required. The lower drum  52  can also be rotated independently from the upper drum, for example, by short stroke air cylinders provided beneath the supporting frame  18  or by servo motors, to effect lowering and raising of the transfer bar  42 . 
     The different positions that the transfer bar  42  can adopt are illustrated in  FIG. 7 . In the loading position shown in  FIG. 7(   a ), the transfer bar  42  is located in front of the rows of vials to enable a first abutment surface  84  to contact the first row of vials  86  and push the rows into the chamber  12 . In this position, a first shoulder  88  of the transfer bar  42  serves to prevent the first row of vials  86  from falling as the rows are pushed into the chamber  12 . In the transfer position shown in  FIG. 7(   b ), the lower ribbon  48  has been wound relative to the upper ribbon  46  to rotate the connecting member  62  anticlockwise (as shown in  FIG. 7)  about pivot  66  and thus cause the transfer bar  42  to rise to the transfer position. When in this raised position, the transfer bar  42  can be moved over the tops of the vials in the chamber  12  by unwinding synchronously the upper and lower ribbons  46 ,  48  of the reel assemblies  44 . In the unloading position shown in  FIG. 7(   c ), the lower ribbon  48  has been further wound relative to the upper ribbon  46  to further rotate the connecting member  62  anticlockwise about pivot  66  and thus lower the transfer bar  42 . In this position, a second abutment surface  90  of the transfer bar  42  contacts the last row of vials  87  in the chamber to pull the vials out from the chamber  12 , with a second shoulder  92  of the transfer bar  42  serving to prevent the last row of vials  87  from falling as the vials are withdrawn from the chamber  12 . In the last row unloading position shown in  FIG. 7(   d ), the transfer bar is returned to the position shown in  FIG. 7(   a ), save that a third abutment surface  94 , located on the opposite surface of the transfer bar  42  to the first abutment surface  84 , is brought into contact with the last row of vials  87  from the final shelf of the chamber  12  to be unloaded. 
     Returning now to  FIG. 1 , the assembly for loading and unloading the chamber  12  also includes an out-feed conveyor  96  for collecting vials from the pusher conveyor  24 . Appropriate guiding (not shown) ensures a smooth transition between these conveyors. The out-feed conveyor  96  is driven by an adjustable speed motor located beneath the supporting frame  18 . 
     A typical sequence for loading the chamber  12  using the assembly shown in  FIG. 1  will now be described. For cold shelf loading, a different loading sequence may be employed. 
     First, the slot door  16  is raised to allow vials to be inserted into the chamber  12  through the slot formed in the chamber wall. The bridge plate  38  is rotated from the raised position shown in  FIG. 3  to create a bridge between the accumulation table  28  and the freeze dryer intermediate plate  40 . When the first shelf  14  to be loaded has been located at the loading position, the intermediate plate  40  is docked to the shelf  14 , and the moveable guide members  82  are moved to the deployed position shown in  FIG. 6 . 
     Vials from the filling line arrive on the in-feed conveyor  20 , which acts as a buffer. When a sensor detects that the number of vials in the buffer is sufficient, the in-feed star wheel  22  transports the required number of vials to the synchronized pusher conveyor  24 . This mechanism eliminates the linear errors caused by diametrical tolerance of the vials. The loading pusher  26  pushes the complete row of vials forward against the previous row of vials (if any) on the accumulation plate  28 , and pushes the whole pack forwards by the equivalent of one vial diameter. When sufficient rows of vials to fill a shelf  14  have been assembled, the loading pusher  26  pushes the pack clear of the accumulation plate  28  and the bridge plate  38  and positions the pack on the shelf  14 . Alternatively, for cold shelf filling, the vials may be pushed row by row from the pusher conveyor  24  directly on to the shelf  14 , or a number of rows of vials may be pushed at a time on to the shelf  14 . 
     After retraction of the loading pusher  26 , the moveable guide members  82  are raised, the intermediate plate  40  is undocked from the shelf  14  and the bridge plate  38  is rotated to enable the freeze dryer to position the next empty shelf for loading. While the shelf is being positioned the next rows of vials are being assembled. 
     The sequence is repeated until the last shelf to be loaded. When all of the shelves have been loaded with vials, the moveable guide members  82  are raised, the intermediate plate  40  is retracted, the bridge plate  38  is raised and the slot door  16  is closed. 
     A typical sequence for unloading the chamber  12  using the assembly shown in  FIG. 1  will now be described, with the movement of the bridge plate  38  and transfer bar  42  during unloading being illustrated in  FIGS. 8(   a ) to  8 ( i ), which, for simplicity, show only a single row of vials  87 . 
     First, the slot door  16  is raised to allow vials to be removed from the chamber  12  through the slot formed in the chamber wall. When the first shelf  14  to be unloaded has been located at the loading position, the moveable guide members  82  are moved to the deployed position, as shown in  FIG. 8(   a ). The bridge plate  38  is then rotated from the raised position shown in  FIG. 8(   a ) to the horizontal position shown in  FIG. 8(   b ) to create a bridge between the accumulation table  28  and the freeze dryer intermediate plate  40 , and the intermediate plate  40  is docked to the shelf  14 . 
     With the transfer bar in the raised position, as shown in  FIG. 8(   b ), the ribbons  46 ,  48  of each reel assembly  44  are synchronously unwound to move the vial pack beyond the final row of vials  87  as shown in  FIG. 8(   c ). The transfer bar  42  is then lowered to the unloading position as shown in  FIG. 8(   d ). The ribbons  46 ,  48  of each reel assembly  44  are then synchronously wound to cause the second abutment surface  90  of the transfer bar to contact vial row  87  to pull the vial pack from the chamber  12  towards the pusher conveyor  24 . 
     When the last row of vials reaches the pusher conveyor  24 , the transfer bar  42  is returned to the raised position shown in  FIG. 8(   a ). The moveable guide members  82  are raised, and the intermediate plate  40  is undocked to enable the freeze dryer to position the next shelf for unloading. 
     The cycle is repeated up to the final shelf to be unloaded. When the last row of vials from the vial pack remains on the accumulation table  28 , as shown in  FIG. 8(   e ), the transfer bar  42  is raised to the position shown in  FIG. 8(   f ), and moved towards the chamber  12  to the position shown in  FIG. 8(   g ) before the transfer bar  42  is lowered to the last row unloading position as shown in  FIG. 8(   h ). Finally, the ribbons  46 ,  48  of each reel assembly  44  are synchronously wound to push the last row  87  on to the pusher conveyor  24 , as shown in  FIG. 8(   i ). The moveable guide members  82  are raised, the intermediate plate  40  is retracted, the bridge plate  38  is raised and the slot door  16  is closed. 
     In the embodiment shown in  FIG. 1 , the transfer bar is used only to unload the vials from the chamber  12 . In a second embodiment shown in  FIG. 9 , the transfer bar  42  is also used to load the vials into the chamber  12 . In this embodiment, the motorised actuating mechanism  34  of the first embodiment is no longer required, as the pusher bar  32  is only required to have a short stroke sufficient to transfer a row of vials from the pusher conveyor  24  on to the accumulation table. The mechanism for moving the pusher bar  32  can now be conveniently accommodated beneath the supporting frame  18 . This can provide a further reduction in the size of the over-all footprint of the freeze dryer  10 . 
     While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the true spirit and scope of the present invention.