The present invention relates to a ventilator, and in particular to a ventilator for assuring an effective prevention of air exchange between a freeze dryer and an area with uncontrolled air quality, irrespective of the process status of the freeze dryer.

Freeze drying is a process that removes from a product water in the form of ice. In the freeze drying process, the product is frozen and, under vacuum, the ice sublimes and the vapour flows towards a condenser. Ice subsequently condensed on the condenser can be removed in a later stage.. Freeze drying is particularly useful in the pharmaceutical industry, as the integrity of the products is preserved during the freeze drying process and product stability can be guaranteed over relatively long periods of time.

Freeze dryers thus typically incorporate a pressure vessel having a freeze drying chamber for receiving a plurality of containers or vials containing the product to be freeze dried. The chamber usually includes a number of shelves, each of which can be raised and lowered within the chamber. 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.

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 that forms, with the chamber, 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, or a dual vial pack per shelf. The loading mechanism is subsequently withdrawn and the shelf raised to enable another shelf to be moved into position for loading. Once loading has been completed, the slot door is 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 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.

During the freeze drying process, it is important that the product is completely frozen prior to the drying steps. To accelerate the freezing process, it is known to refrigerate the shelves of the freeze dryer, typically by passing a heat exchange medium, such as silicone oil, through cavities formed in the shelves. Due to buoyancy effects, during the loading of cold shelves relatively cold air will leave the freeze dryer from the bottom of the slot door, and is replaced by relatively warm air from the clean room environment, which enters the freeze dryer through the top of the slot door. This is only acceptable if the clean room environment matches the desired ambient condition within the freeze dryer, which can be expensive and, in practice, difficult to achieve. Consequently, it is usual practice for the chamber to be periodically sterilised to remove contaminants that have entered the chamber within the relatively warm air entering the chamber during loading. The enforced "shut down" of the freeze dryer during sterilisation reduces the productivity of the freeze dryer, and increases maintenance costs. It is an aim of at least the preferred embodiment of the present invention to seek to solve these and other problems.

In one aspect, the present invention provides a ventilator for passing a controlled air stream across a slot opening to a chamber of a freeze dryer, the ventilator comprising a cabinet locatable on or relative to the chamber such that the cabinet is located over the opening, the cabinet having an aperture providing access to the opening; a mechanism for selectively closing the aperture; a fan for generating the air stream within the cabinet; and a filter for filtering particulates from the air stream.

The ventilator can thus provide a localised, controlled air flow across the opening such that only air from this controlled air stream enters the chamber through the opening. The flow of clean air through the cabinet also prevents also ingress of lower classified air into the cabinet and therefore also the freeze dryer. As a result, the level of contamination of the chamber is reduced, which can enable the frequency of sterilisation of the chamber to be reduced, improving productivity of the chamber. The provision of the aperture enables automated loading and unloading of the chamber to be performed whilst the cabinet is in situ over the opening. The cabinet can be conveniently mounted on the chamber so that it is located over the opening, with the aperture being located opposite the opening to enable the chamber to be accessed through the aperture.

The ventilator is suitable for use with any chamber where thermosyphoning problems are encountered. As the ventilator is particularly suitable for use with a freeze dryer, in another aspect the present invention provides a freeze dryer comprising a chamber, a slot formed in the chamber for providing access to the chamber, a moveable slot door for selectively exposing the slot, and a ventilator for passing a controlled air stream across the exposed slot, the ventilator comprising a cabinet located over the slot door, the cabinet having an aperture providing access to the slot to enable the freeze dryer to be loaded and unloaded through the cabinet, means for selectively closing the aperture, a fan for generating the air stream within the cabinet, and a filter for filtering particulates from the air stream before it passes across the slot door.

The slot door of a freeze dryer tends to be relatively heavy. By providing a mechanism for selectively closing the aperture in the cabinet, the slot door can be kept open during the entire loading and unloading sequences, which may take several hours, with the aperture being selectively opened and closed as required. The aperture may be conveniently closed by one or more doors, each having a respective mechanism for moving the door in a direction transverse to the aperture. These doors can be formed from lighter material than the slot door of the freeze dryer, and so opening and closing of these doors can take a shorter time than the opening and closing of the slot door, thereby shortening the time taken to perform the loading and unloading sequences.

Preferred features of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a ventilator cabinet mounted to a freeze dryer;

Figure 2 is a similar schematic view to Figure 1 , including a loading mechanism for loading vials into the freeze dryer;

Figure 3 is a front view of the ventilator mounted on the freeze dryer; and

Figure 4 is a side, cross-sectional view of the ventilator mounted on the freeze dryer.

With reference to the figures, a freeze dryer 10 comprises a chamber 12 having a slot 13 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 13 can be closed by a slot door 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.

A ventilator 16 is provided for passing a controlled air stream across the slot 13 of the chamber 12. In this embodiment, the ventilator 16 is mounted on to the front wall of the chamber 12, for example, by bolting the ventilator 16 on to a stainless steel bezel 18 provided on the front wall. Where the slot is formed in the main door of the freeze dryer, the ventilator may be mounted directly on to the door. Alternatively, the ventilator may be a floor standing unit, or may be mounted to the ceiling 20 of the external room.

The ventilator 16 comprises a cabinet 22 defined, at least in part, by a front wall 24, (at least partially open) top wall 26, and two side walls 28. When the ventilator 16 is mounted on the chamber 12, the cabinet 22 is located over the slot door 30 of the chamber 12, as shown in Figure 4. The bottom of the cabinet 22 is open.

With reference to Figure 2, the ventilator 16 is designed to remain in place over the slot door 30 when an assembly 32 is docked to the freeze dryer 10 for the automated loading of the freeze dryer 10 with vials, and for the subsequent automated unloading of those vials from the freeze dryer 10. In order to enable the assembly 32 to access the slot 13 of the chamber 12, the cabinet 22 includes an aperture 36 formed in the front wall 24 and positioned such that, when the ventilator 16 is mounted on the freeze dryer 10, the aperture 36 is located opposite to the slot 13 formed in the chamber 12, as shown in Figure 4.

The aperture 36 is selectively opened and closed by an aperture opening and closure mechanism indicated generally at 38 in Figure 4. With reference to Figure 3, this mechanism 38 includes three doors 40, 42, 44 which together fully close the aperture 36. Each door 40, 42, 44 can be individually lowered to expose a respective part of the aperture 36, and subsequently individually raised to close that part of the aperture 36, by an actuating mechanism 46. For example, each door 40, 42, 44 may be secured to and reciprocated between the lowered and raised positions by a piston rod of a cylinder of a respective hydraulic piston-cylinder unit mounted on the ventilator 16. Other mechanical devices, such as a motor driven toggle mechanism, screw or gear assemblies may be used instead of the piston-cylinder unit. Guide tracks 45 may be provided for guiding movement of each door as it is raised and lowered relative to the aperture 36.

As shown in Figure 4, the ventilator 16 includes a fan 48 and absolute filters for generating a controlled laminar air flow within the cabinet 22. In the illustrated embodiment, the fan 48 is located above the top wall 26 of the cabinet 22; as mentioned previously the top wall 26 is partially open to allow the air stream generated by the fan 48 to enter the cabinet 22, pass downwards through the cabinet 22 and across the slot door 30, and exit the cabinet 22 from the open bottom thereof. The controller may be provided for controlling parameters of the generated air stream, such as the pressure, speed, temperature and humidity of the air stream. A filter 50, for example, a HEPA filter, is provided above the cabinet 22 to filter any particulates or other contaminants from the generated air stream before it enters the cabinet 22.

In use, the ventilator 16 is mounted on the freeze dryer 10, with the aperture 36 closed by the mechanism 38. The loading assembly 32 is then brought forward to load vials into the chamber 12. Before either the slot door 30 is opened to expose the slot 13 or the mechanism 38 is actuated to expose the aperture 36, the fan 48 is started to generate a continuous, unidirectional air stream passing downwards through the cabinet 22, the open bottom of the cabinet 22 preventing the build-up of air pressure within the cabinet 22. Once the air stream has been fully established, the slot door 30 is raised, using an actuating mechanism indicated generally at 52 in Figure 4, to expose the slot 13. The actuating mechanism 52 may be provided by one or more hydraulic piston-cylinder units, the slot door 30 being attached to the or each piston so that the door is raised or lowered with movement of the or each piston. Again, other mechanical devices, such as a motor driven toggle mechanism, screw or gear assemblies may be used instead of the piston-cylinder unit. The air stream passing through the cabinet 22 across the exposed slot 13 prevents contaminants entering the chamber 12 from the external room, and ensures that if any air does enter the chamber 12, particularly when the shelves 14 of the freeze dryer 10 are cold, that air is of a controlled nature (pressure, contamination level, humidity, temperature, etc.).

When the assembly 32 is ready to load vials into the chamber 12, the mechanism 38 is actuated to lower one or more of the doors 40, 42, 44 as required to expose the aperture 36. For instance, when the left-hand side of a shelf 14 is to be loaded, only the doors 40 and 42 are lowered, and when the right-hand side of a shelf 14 is to be loaded, only the doors 42 and 44 are lowered. A bridge plate 60 or the like of the assembly 32 can then be inserted through the exposed part of the aperture 36 and the exposed slot 13 to dock with a shelf 14 of the freeze dryer 10 and allow vials to be pushed from the assembly 32 on to the shelf of the chamber 12. The assembly 32 may be provided with its own laminar air flow fan, which can further prevent contaminants from entering the chamber 12 from the assembly 32.

Once the shelf 14 has been loaded, the bridge plate 60 is withdrawn to enable the loaded shelf to be raised and another shelf to be positioned ready for loading. Whilst the bridge plate is removed from the cabinet 22 during a loading procedure, the relevant doors 40, 42, 44 are raised to close the aperture 36. However, due to the continuous passage of the air stream across the slot 13, it is not necessary to lower the slot door 30 to close the slot 13 until the chamber 12 has become fully loaded. As the doors 40, 42, 44 may be lighter than the slot door 30, the time taken to raise and lower these doors may be significantly shorter than the time taken to raise and lower the slot door 30, and this may markedly decrease the time taken to complete the loading procedure.

Following completion of the loading and the closure of the slot door 30, the fan 48 may be stopped and the ventilator 16 dismounted from the chamber 12. Alternatively, the ventilator 16 may be kept in place for use during the subsequent unloading of the vials from the chamber 12 following the completion of the freeze drying process. Similar to the loading procedure, before either the slot door 30 is opened to expose the slot 13 or the mechanism 38 is actuated to expose the aperture 36, the fan 48 is started to generate the air stream within the cabinet 22. Once the air stream has been fully established, the slot door 30 is raised using actuating mechanism 52 to expose the slot 13. The mechanism 38 can then be actuated to expose the aperture 36 as required to allow the vials to be unloaded through the cabinet 22.

In summary, a ventilator for controlling the local environment external to a slot of a freeze dryer is described. The ventilator comprises a cabinet located over the slot door of the freeze dryer, a front wall of the cabinet facing the freeze dryer. An aperture formed in the front wall allows access to the slot to enable the freeze dryer to be loaded and unloaded through the cabinet, the ventilator being provided with one or more doors for opening and closing the aperture as required. A fan generates a controlled air stream within the cabinet, the air stream passing across the slot door. Thus, when the slot door is raised to open the slot, only air from this controlled air stream enters the freeze dryer.