Freeze dryer slot door actuator and method

Movement of a slot door of a freeze dryer is driven by a rack and pinion actuator. The actuator is easily sanitized and includes internal elements that are accessible to sanitizing sprays. The pinions are driven by pinion shafts that pass through a seal separating an aseptic area from a non-aseptic area where the drive train is positioned. Only rotary motion is transferred across the aseptic barrier, reducing the need for a bellows or sliding covers, which are difficult to sanitize.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for operating a slot door of a freeze dryer chamber or the like, and to a freeze dryer incorporating such an apparatus.

BACKGROUND OF THE INVENTION

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

Freeze dryers have a vacuum chamber for receiving a plurality of containers or vials containing the product to be freeze dried. The chamber usually includes a number of shelves, which can be raised and lowered within the chamber. To load the shelves, the shelves are initially moved to the lower portion of the chamber, with the uppermost shelf in a loading position. After that shelf has been loaded, the mechanism automatically raises the shelves to permit the next shelf to be moved to the loading position. The 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 product is through a rectangular opening, or slot, formed in a wall or in a main door of the chamber. A moveable slot door closes the slot. To permit vials of product to be inserted into the chamber, the slot door is vertically raised relative to the slot by moving the slot door along guide tracks.

Various techniques have been used in loading and unloading vials in the chamber. In one arrangement, a mechanism pushes vials onto a shelf in the chamber from a conveyor belt running parallel with the slot. The vials may be loaded from the conveyor belt row by row onto a shelf. Another loading technique utilizes a wheeled transfer cart that moves on rails. The transfer cart may carry an entire shelf of vials at a time, which may be pushed onto the shelf in the chamber in a single loading operation. After a shelf is completely loaded, the shelf is raised and another is moved into position for loading. Once loading has been completed, the slot door is lowered to close the slot and enable the chamber to be evacuated for subsequent freeze drying of the contents of the vials.

Several actuation mechanisms have been used to move the slot door of a freeze drying chamber between the open and closed positions. In one arrangement, one or more lead screws or ball screws are used to raise and lower the slot door in its guide tracks. The screws are arranged on either side of the slot door. In another arrangement, one or more pneumatic or hydraulic piston actuators are used to raise and lower the slot door.

The slot door and its actuation mechanism reside in a class100, or class A, sanitary clean room environment. In some applications, one or more of the loading and door actuation components, together with the chamber opening, may reside in an isolator that contains a sterile environment, the isolator allowing the room it is located in to have less stringent cleanliness requirements, such as class C.

The chamber, slot door and actuation mechanism must periodically be sanitized or sterilized to maintain the environment. Both screw-type and piston-type actuators include internal mechanisms that are not easily sanitized using direct chemical or steam sanitizing techniques. For example, ball screws contain ball bearings, ball recirculation tracks and internal ball grooves that cannot easily be sanitized without disassembly. Similarly, the threads of a lead screw and the cylinder rod, cylinder wall and piston of a hydraulic or pneumatic actuator are not easily accessed for sanitization.

To maintain the aseptic nature of the clean environment, those linear actuation mechanisms may be placed outside the clean environment. In that case, a link having a linear motion must traverse the barrier between the clean processing environment and the external, ambient environment. The barrier must therefore incorporate a moveable seal such as a flexible bellows or a sliding cover to permit movement while enclosing the sanitary environment. Both the bellows and the sliding covers have shortcomings. Bellows are difficult to sanitize manually because they present an internal geometry with numerous corrugations. That especially presents challenges in applications where sanitization is done by spraying. Sliding covers also present problems inasmuch as they move into and out of the sanitary environment and cannot be hermetically sealed.

There therefore remains a need for a slot door actuation method and apparatus with improved characteristics for maintaining a clean environment.

SUMMARY

The present disclosure addresses the needs described above by providing systems and methods relating to the operation of a slot door of a freeze drying chamber. One embodiment described herein is a freeze dryer system having an aseptic area and a non-aseptic area. The system includes a vacuum chamber and a slot door for providing access through an opening in the vacuum chamber by sliding between open and closed positions, the slot door being in the aseptic area in both the opened and closed positions. At least one gear rack is connected to the slot door, the gear rack being within the aseptic area of the system. For each gear rack, a pinion is engaged with the gear rack for driving the gear rack to move the slot door between the open and closed positions, the pinion being within the aseptic area.

The freeze dryer system may further include at least one pinion drive shaft for driving the at least one pinion in a rotary motion, the at least one pinion drive shaft passing through a rotary seal separating the aseptic area of the system from the non-aseptic area. That arrangement may further include a drive means connected for rotating the drive shafts and pinions, the drive means being in the non-aseptic region of the system. The drive means may comprise first and second right angle drives coupled to respective pinion drive shafts; a shaft coupling the right angle drives for synchronous rotation; and a motor coupled for driving the right angle drives.

The freeze dryer system may further comprise an automated system for sanitizing at least the gear racks and pinions in the aseptic area. The system may deliver a cleaning agent such as vaporized hydrogen peroxide, bleach or steam. The slot door may be spaced apart from a wall of the vacuum chamber by an extension surrounding the opening in the vacuum chamber. The system may further include a loading mechanism positioned for loading product through the opening in the vacuum chamber, the loading mechanism being at least partially within the aseptic area. Guards may be positioned over the at least one gear rack and pinion, the guards being manually removable for sanitizing the gear and pinion.

Another embodiment disclosed herein is a method is for the operation of a slot door in an aseptic environment. A pinion drive shaft is sealed with a sanitary seal for keeping a pinion end of the drive shaft aseptic while a drive end of the drive shaft is not aseptic. At least the following elements are then sanitized: a pinion mounted on the pinion end of the pinion drive shaft, a gear rack attached to the slot door and in engagement with the pinion, and the slot door. The drive end of the drive shaft is then driven to rotate the pinion, drive the gear rack and operate the slot door.

The sanitizing step may further comprise spraying a sanitizing agent on the elements of the freeze drying chamber. The sanitizing agent may include vaporized hydrogen peroxide, a bleach agent or steam. The step of sealing may include applying a lip seal or a packing. The pinion drive shaft may be driven through a right angle drive mechanism.

Another embodiment is a freeze dryer system that comprises a vacuum chamber having a vacuum chamber opening for loading product into the vacuum chamber. A slot door is mounted for substantially linear movement between an open position for loading product through the vacuum chamber opening and a closed position for sealing the vacuum chamber opening. At least one gear rack is connected to the slot door. For each gear rack, a pinion is engaged with the gear rack for driving the gear rack to move the slot door between the open and closed positions.

The freeze dryer system may further include a loading mechanism positioned for loading product through the vacuum chamber opening. At least one guard may be positioned over the at least one gear rack and pinion, the guards being removable for sanitizing the gear rack and pinion. Each pinion may have an axis of rotation substantially perpendicular to a plane of the slot door.

DESCRIPTION OF THE INVENTION

The apparatus and method of the present invention overcome the problems inherent in the prior art by operating the slot door with a mechanism having exposed components that are easily sanitized using standard automated or manual techniques. The invention furthermore eliminates a need for a bellows or sliding cover by eliminating the need to traverse the sanitary barrier with an actuator having linear movement.

A vacuum chamber slot door and door operating mechanism100in accordance with the invention is illustrated inFIGS. 1A & 1B. The mechanism100provides access to a vacuum chamber opening130through which materials to be freeze dried are loaded into a vacuum chamber101. In the embodiment shown, the mechanism100is spaced away from a front wall of the vacuum chamber101by an extension210, as further described elsewhere in this disclosure with reference toFIGS. 2A and 2B.

The opening130is opened and closed by raising and lowering a slot door105, which is shown in an open position inFIG. 1Aand in a closed position inFIG. 1B. In the closed position, the slot door105contacts door seals132(FIG. 1A) to maintain a vacuum or positive pressure in the chamber.

A pair of door guides106on either side of the door105constrains the door for translation in a linear sliding motion between the open and closed positions. In addition, the guides restrain the door when the chamber is placed under positive pressure during sanitization or sterilization. In the illustrative figures, the door guide on the right side has been removed to more clearly show the underlying components. The slot door105, together with the actuation mechanism described below, are maintained in a sanitary environment so that the door may be opened and closed, and materials may be loaded and unloaded, without contaminating the materials.

A gear rack110is fixed to a side of the slot door105. A similar gear rack is fixed to the opposite side of the slot door105and is not visible inFIGS. 1A & 1Bbeneath the guide106. The gear racks110may be fabricated from a non-corroding metal such as stainless steel or from a resin suitable for use in a sanitary or sterile environment. Each gear rack comprises a plurality of gear teeth. Each tooth may have a straight tapered shape for meshing with involute pinion teeth as described below.

The gear racks110move with the slot door105. As can be clearly seen in the figures, the gear racks110do not extend excessively beyond the top edge105A of the slot door105. The gear racks110are furthermore contained entirely within the aseptic environment, so no flexible bellows or sliding cover is necessary to transmit linear motion across the aseptic barrier.

Rotating pinion gears120,121mesh with the gear racks110located on the sides of the slot door, and drive the linear motion of the door. The pinions120,121have a plurality of teeth that may have an involute tooth profile to maximize efficiency in meshing with and driving the racks. In a preferred embodiment, one rack and pinion assembly is positioned on each side of the door. The rotary motion of the two pinions120,121is synchronized to assure even tracking of the door in its linear motion.

The pinions120,121and racks110are exposed within the aseptic area to provide access for spraying with a sanitizer solution. Unlike ball screws, lead screws, hydraulic or pneumatic cylinders and most other actuation mechanisms, the rack and pinion arrangement has no internal parts that are inaccessible without disassembly. The interface between the rotating pinion and linear rack may be left open for spray sanitization, either automated or manual. Alternatively, the components may be guarded against incidental contact, using guards that are easily removed for spray or steam sanitization. For example, the door guide106may incorporate quick removal and replacement features. The resulting assembly is easily sanitized or sterilized without major disassembly of the components.

The pinions120,121are driven by drive shafts coupled to the pinions at the rotational axes of the pinions. In the embodiment shown inFIGS. 1A & 1B, the pinions120,121are arranged with their axes of rotation perpendicular to the plane of the slot door105. Separate drive shafts drive the two pinions and are synchronized as described below. In an alternative embodiment (not shown), the two pinions rotate on a single axis of rotation that is parallel to the plane of the slot door105. In that embodiment, a single shaft may couple the two pinions.

A slot door nozzle or extension210is shown inFIGS. 2A & 2B, which illustrate side elevation and top views of the chamber, respectively. The extension210extends from a wall202of the chamber201to a bezel215that separates an aseptic area290from a non-aseptic area291(FIG. 2A) of the freeze drying system. The extension210surrounds the opening130(FIG. 1A) of the vacuum chamber201, and isolates the aseptic interior of the chamber from the non-aseptic area291.

The door operating mechanism100is mounted on an end of the extension210opposite the wall202of the chamber201, and operates the door105. The pinions120,121are driven by drive shafts170,171that pass through the bezel215. Drives177,178drive the drive shafts170,171from the shaft ends opposite the pinions120,121. At a location intermediate the pinion end and the drive end, the drive shafts170,171are sealed to the bezel215by a rotary seal such as a lip seal or a packing. Contaminants on the non-aseptic side291of the bezel215are thereby prevented from contaminating the aseptic side290.

A freeze dryer system300, including a vacuum chamber301and an aseptic region390, is shown inFIG. 3. The aseptic area390contains the slot door305and opening330of the vacuum chamber301, together with a loading mechanism including a conveyor377and a pusher386for pushing rows of vials onto shelves (not shown) in the chamber301. The loading mechanism is designed to facilitate automated or manual sanitization. The aseptic area390and the non-aseptic area391are separated by a bezel or barrier315. The bezel315is spaced apart from the chamber301by an extension331surrounding the opening330.

Gear racks310,311are mounted on either side of the slot door305to drive the door between the open position shown inFIG. 3and a closed position. The pinions320,321drive the racks310,311, respectively. The pinions are driven by a drive mechanism such as that described below with reference toFIG. 4. The drive mechanism includes a power drive shaft354that connects the mechanism to a motor (not shown). The drive mechanism is located on a non-aseptic side391of the bezel315and is therefore outside the aseptic area390. The racks310,311, pinions320,321and part of the pinion drive shafts (not shown) are exposed within the aseptic area390and are therefore easily sanitized by spraying. Guards (not shown) may cover those components within the aseptic area; if so, the guards are easily removable for manual sanitizing.

The pinion drive shafts pass through the isolating bezel315that separates the aseptic area390from the non-aseptic mechanical area391containing the pinion drive mechanism. The seals sealing the drive shafts to the bezel maintain aseptic conditions on the pinion end of the shafts despite exposure of the drive end of the shaft to non-aseptic conditions.

An exemplary pinion drive mechanism assembly400is shown inFIG. 4. The pinions420,421are driven by drive shafts470,471, respectively. The drive shafts470,471pass through seals480,481in the bezel415, separating an aseptic area490from a non-aseptic mechanical area491. While the drive shafts are shown as separate elements from the pinions, the drive shafts may be integral with the pinions or may have a configuration different from that shown without departing from the scope of the present disclosure. The term “drive shaft,” as used herein, includes separate shafts470,471as shown, as well as any portion of the pinion or of any other component that rotates with the pinion, and that provides a sealing surface for the seals.

The drive shafts470,471are driven by right angle drives477,478, respectively. The right angle drives477,478are synchronized by a linking drive shaft450and are driven through a power drive shaft454by a motor455. The motor455, together with other components of the freeze drying system, may be controlled by a controller495.

The right angle drives477,478and the motor455each have internal components that are difficult or impossible to sanitize. Those components, however, are in the non-aseptic mechanical area491of the system, and are separated from the aseptic area490by the bezel415and seals480,481. In that way, those components may be utilized to drive the pinions, while only the easily sanitized pinions and racks are within the aseptic area490.

Other pinion drive mechanisms, including but not limited to chain drive systems, separate hydraulic or electric servo motors, and belt drive systems, may be used without departing from the scope of the disclosure. Those drive mechanisms preferably include a timing scheme to assure that the pinions rotate together. In the case of pinions rotating on a common axis parallel with the plane of the door, a common drive shaft may be used, eliminating the need for a more complicated timing mechanism.

A method500for operating a slot door of a freeze drying chamber in an aseptic environment in accordance with one embodiment of the invention is illustrated by the flow chart ofFIG. 5. The pinion drive shaft is sealed (step510) with a sanitary seal. The seal keeps the pinion end of the drive shaft aseptic while the drive end of the drive shaft may be exposed to a non-aseptic environment. The seal creates a barrier between the pinion drive shaft and a component separating the aseptic and non-aseptic environments, such as the bezel315shown inFIG. 3.

Elements in the aseptic area are then sanitized (step520). Those elements include the pinion end of the drive shaft, a pinion mounted on the pinion end of the drive shaft, a gear rack attached to the slot door and in engagement with the pinion, and the slot door. Those elements may be sanitized in an automated process wherein a sanitizing solution such as an isolator agent containing a vaporized hydrogen peroxide sterilant such as VHP® sterilant available from Steris Corporation of Mentor, Ohio, USA, is applied to the components in an isolator, or by applying a sanitizing agent such as bleach in a clean room environment. The open nature of a rack and pinion actuator facilitates the sanitizing process. In another embodiment, guards or guides installed over the rack and pinion actuator are manually removed before the sanitizing step. The sanitizing step may include manually applying a sanitizer, or exposing the components to a sanitizing gas or to steam, or irradiating the components.

The drive end of the drive shaft is then driven (step530) to rotate the pinion, drive the rack and operate the slot door. Because the pinion drive shaft is sealed with a sanitary seal, the drive mechanism assembly need not be sanitized.

Methods of the present invention may be controlled or performed in part by an industrial controller or computer495(FIG. 4). The computer includes a central processing unit (CPU) and memory interconnected through a bus with input and output devices such as a man-machine interface, a network interface and interfaces with the freeze drying system for purposes known in the art such as initiating motion and receiving sensor data.

The memory may include random access memory (RAM), read-only memory (ROM) and various moveable and fixed memory drives. The memory stores data used during execution of a program in the CPU, and may be used as a work area. The memory furthermore functions as a program memory for storing a program. The program may reside on computer-usable medium as computer readable instructions stored thereon for execution by the CPU or another processor to perform the previously disclosed methods.

The foregoing Detailed Description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Description of the Invention, but rather from the Claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention.