WO2010134953A1 - Modular freeze drying system - Google Patents

Abstract

A freeze drying system and methods are provided that incorporate a vacuum pump system, a vapor condenser, interconnection components, vacuum valves, and a controller. Multiple sample containers can be introduced to the system at separate times and for different processing profiles. The system is particularly well suited for consumer use in the home. The sample containers can be similar to those used to store food, such as leftovers, in a residential freezer.

Description

MODULAR FREEZE DRYING SYSTEM

[0001] This application claims the benefit of U.S. Provisional Application No. 61/179,270, entitled "Modular Freeze Drying System," filed May 18, 2009, the contents of which are hereby incorporated by reference.

BACKGROUND OFTHE INVENTION

[0002] The present invention relates to a lyophilization (freeze drying) system for the processing of food and non-food items. More particularly, the invention provides a lyophilization system in which multiple containers containing items to be freeze dried can be introduced at separate times and for different processing profiles. The system is particularly well suited for consumer use in the home.

[0003] Lyophilization (hereinafter referred to by its more common name, freeze drying) has been around for centuries. Natives in the South American Andes preserved foods by leaving it high in the mountains for long periods. The weather was cold enough to freeze the items and over enough time cause the ice to sublime.

[0004] The modern version of freeze drying was established early in the 20th century and was commercialized in the 1930s resulting in the advent of freeze dried coffee. With coffee and other foods, freeze drying has shown itself to have significant advantages over other food storage techniques.

[0005] Requirements for a modern freeze drying system are fairly straightforward. However, standard components able to meet the requirements tend to be expensive. In cases of integration, as in the case of small laboratory systems, the relatively small and specialized market as well as the need for high precision operations do not provide typical economies of scale. [0006] Anyone familiar with traditional freeze drying systems will appreciate that innovation would require significant investment without a likely payback. Further, for these standard systems and their relatively small specialty markets, existing components are sufficient to accomplish the goal. This is not the case for larger markets, such as the consumer marketplace.

[0007] It would be advantageous to provide a modular freeze drying system (MFDS) that improves system performance over prior art designs. It would be further advantageous to provide such a system that is significantly more cost effective than prior art systems. It would be still further advantageous to provide an MFDS that, as a result of improved system performance and relatively low cost, is amenable to consumer use and use in other large scale markets.

[0008] The present invention provides apparatus and methods having the aforementioned and other advantages.

SUMMARY OF THE INVENTION

[0009] The present invention provides a freeze drying system that includes a vacuum pump. A plurality of ports are coupled to the vacuum pump. A connector is associated with each port. Each connector is adapted to couple vacuum from the associated port to a vacuum container. A vacuum valve associated with each port selectively controls vacuum at the port. A controller controls the vacuum valves to allow vacuum to be selectively applied to vacuum containers via the ports.

[0010] A vacuum container can be connected to one of the ports. One or more sensors can be arranged to sense one or more parameters in the vacuum container. The controller is coupled to monitor the sensor(s) and control the application of vacuum to the container in response to said parameters). The parameter(s) can comprise, for example, at least one of moisture, temperature, weight and vacuum.

[0011] In a preferred embodiment, the pump is a peristaltic pump. A second pump can be used to provide initial evacuation prior to engagement of the peristaltic pump.

[0012] The vacuum container can comprise a sealable storage container suitable for freezing portions of food in a home freezer. In an illustrated embodiment, the vacuum container includes an integrated valve to enable coupling of the container directly to its associated port. The integrated valve can comprise, for example, a solenoid electronically controlled by the controller. The vacuum container can also include means for enabling a processing state of the container to be monitored.

[0013] A vapor condenser can be coupled between the vacuum pump and the ports. Each port can include an interface for coupling the port to a vacuum container. The interface can be adapted to allow for various container sizes and shapes to mate therewith and enable a vacuum to be reached. [0014] A sensor can be associated with at least one of the ports and coupled to the controller. In such an embodiment, the controller is responsive to the sensor for detecting the presence of a vacuum container at the associated port. A user interface can be associated with the controller, such that the controller is responsive to user input entered via the user interface to control the vacuum valves. In this manner, samples to which vacuum is applied can be processed according to a sample specific scheme as directed by the user.

[0015] A plurality of vacuum containers can be provided for connection to different ones of the ports. Sensor means associated with the controller can be provided for detecting the coupling of an additional container to one of said ports. In such an embodiment, the controller is responsive to the sensor means for (1) actuating said vacuum pump if it is not already running, (2) closing the vacuum valves associated with the containers previously connected to ports, (3) opening the vacuum valve associated with the additional container, and (4) opening the vacuum valves associated with the containers previously connected to ports after the vacuum level of the additional container has reached a predetermined value.

[0016] A method is provided for freeze drying samples of food or the like. In accordance with the method, a vacuum pump is provided. The vacuum pump is coupled to a plurality of ports. Each port is adapted to couple vacuum from the vacuum pump to an associated vacuum container. A plurality of vacuum valves is arranged to allow the isolation of individual ports from the other ports. The valves are controlled to selectively provide isolation in order to allow the coupling and decoupling of vacuum containers to and from the ports and/or to individually control the processing of samples to be freeze dried within the vacuum containers.

[0017] The valves can be controlled to isolate the pump from the ports while the samples continue to be processed. Parameters within the vacuum containers can be monitored during processing of the samples. The processing of the samples can be controlled in response to these parameters.

[0018] A removable element can be provided to facilitate the capture of ice that is accumulated during the processing of the samples. The removable element can be removed to dispose of the ice.

[0019] In practicing the method of the invention, various different steps can be taken. These include, for example, placing a sample to be freeze dried into a sealable storage container. This container can then be placed into a freezer. The container may then be removed from the freezer after the sample is frozen. The container, with the frozen sample therein, can then be coupled to one of the ports. A vacuum can then be drawn in the container to freeze dry the frozen sample.

[0020] The coupling of a vacuum container to one of the ports can comprise a series of steps. These may include, for example, actuating the vacuum pump if it is not already running. Vacuum valves associated with the containers previously connected to ports are then closed. A vacuum valve associated with the additional container is opened. The vacuum valves associated with the containers previously connected to ports are re-opened after the vacuum level of the additional container has reached a predetermined value.

BRIEFDESCRIPTION OFTHE DRAWINGS

[0021] Figure 1 is a graph illustrating the "triple point" of water;

[0022] Figure 2 is a block diagram illustrating a conventional prior art freeze drying system;

[0023] Figure 3 is a block diagram illustrating a conventional prior art laboratory freeze drying system;

[0024] Figure 4 is a block diagram of a freeze drying system in accordance with the present invention;

[0025] Figure 5 is an illustration of a clamping mechanism for a vacuum chamber in accordance with the invention, wherein Figure 5a shows an open position and Figure 5b shows a closed position;

[0026] Figure 6 is a perspective illustration of an example container and lid that can be used in accordance with the invention;

[0027] Figure 7 is a cross-sectional view of an example container that can be used in accordance with the invention;

[0028] Figure 8a is a top view of an example container that can be used in accordance with the invention, wherein sensors are provided for monitoring parameters of the freeze drying process;

[0029] Figure 8b is a cross-sectional view of the container shown in Figure 8a;

[0030] Figure 9 is a diagram illustrating a condenser for a freeze drying system having a removable element designed to capture the condensed ice and to allow for its easy clearing; and

[0031] Figure 10 illustrates an example peristaltic pump head that can be used in a freeze drying system in accordance with the invention. DETAILED DESCRIPTION OFTHE INVENTION

[0032] Lyophilization, or freeze drying, has been used for processing food for storage and other applications for many years. First identified as being used by Andean natives hundreds of years ago, it takes advantage of a process of removing water from frozen items. Sublimation - changing from the solid phase (i.e., frozen) to vapor phase without going through the liquid phase - is key to the process because it effectively removes most, if not all, of the water from an item while minimizing the negative effects that may result from other removal techniques like dehydration.

[0033] Modern freeze dry systems rely on the same fundamental principal of removing the water from frozen items. The freeze drying process (hereinafter "process") relies primarily on sublimation although some additional techniques are used to further reduce water content of the sample. Unlike the Andean natives who did not have a lot of time to allow for natural sublimation (and little choice), modern freeze dry systems greatly accelerate the sublimation by placing a frozen item to be freeze dried under a vacuum. The vacuum is set at a point well below the "triple point" of water, at which all three phases (ice, water and vapor) can exist simultaneously. The triple point is illustrated in graph form in Figure 1 for a typical water vapor pressure charge. The triple point 101 of water is nominally 0°C (32° F) and 4.6 mmHg (0.24 inHg).

[0034] A typical prior art freeze drying system is shown in Figure 2. This system includes three primary components: vacuum chamber 201, vapor condenser 202 and a vacuum pump 203. These are connected either by proximity (i.e., in the same space) or via some plumbing means 204 (e.g., piping, a channel or a combination) to allow for vacuum pump 203 to evacuate chamber 201. Typically, a fourth component is provided in the form of some type of controller 205 to manage the overall interactions - if nothing more than turning on and off the other power components. The item to be processed is placed in chamber 201. It is assumed for explanation purposes that the sample is frozen prior to placement into chamber 201 , but it is clear that the system may also include a means for freezing the sample as a part of its overall processing. For the purposes of this description, the word "sample" will be used to describe the item(s) be processed but will be understood to include food, biological specimens or other items or sets of items.

[0035] The vacuum level required in chamber 201 is typically less than 1 Torr (mmHg) in order to effect reliable sublimation while the sample remains frozen. In some applications, the vacuum required is significantly lower, in the range of 0.01 Torr. It is well understood that vacuum levels may vary but are considered generally for the purposes of this description. This presents a challenge for a typical freeze drying system in that most systems are built with chambers that are large and require substantial vacuum power in order to properly evacuate the chamber while the sample remains sufficiently frozen to allow sublimation.

[0036] The vapor condenser 202 is used to capture the water molecules being sublimated from whatever sample is being processed and to prevent those water molecules from entering the vacuum pump. Those familiar with freeze drying will readily understand that vapor condenser 202 can be eliminated completely in many installations. Should one rely on a system like a steam ejector to provide the necessary vacuum, for example, there is no concern over sublimated water vapor interfering with a pump so it can be removed as a part of the vacuum system.

[0037] In this arrangement, it would be obvious that the sublimation starts on the outer surface(s) of the sample. Depending on the structure of the sample, this can lead to the middle part of the sample retaining water because of the difficulty of water vapor escaping the already dried portions of the sample. To overcome this issue, most freeze drying system rely on a "secondary drying" step involving warming the sample to a temperature sufficient to allow the water remaining inside to overcome the barrier caused by the already dried outer sections. [0038] Large systems, which typically use a multiplicity of shelves on which to place samples, will provide a means to warm the samples to enable secondary drying. Examples of such means include an ability to warm the shelves on which samples rest or exposing samples to a radiant heat source. Smaller systems such as those used in laboratory systems that handle small individual samples will rely on ambient temperatures outside the chamber to provide the warming necessary for secondary drying.

[0039] Unlike larger systems, which include vacuum chamber volumes ranging from a few cubic feet to thousands of cubic feet, smaller laboratory type systems rely on much smaller chambers. Some larger systems consist of multiple chambers being connected to a central vacuum system, with each chamber being sufficiently large to allow for multiple samples or shelves of samples to be incorporated. Laboratory systems like the prior art system shown in Figure 3 also offer added flexibility by allowing multiple small chambers 301 (e.g., glass vacuum bottles), each holding a single or small number of samples, to be connected to the system at 302 to allow for simultaneous processing of various samples. These incorporate a simple connection to the small chamber, typically via a rubber stopper 303 arrangement to seal the chamber opening and a valve means 304 to manually isolate the vacuum chamber connection from the rest of the system until the chamber is in place and the freeze drying process is ready to begin.

[0040] As one can readily appreciate, while existing systems operate as one would expect, they lack flexibility and ease-of-use that would be required to move the capability for freeze drying into a consumer-level or other high volume marketplace. The MFDS techniques, methods and apparatus described herein not only address these issues but do so in novel ways that can also be incorporated into larger systems should the inherent advantages be important. [0041] An example implementation of a MFDS in accordance with the invention is shown in Figure 4. This implementation provides a modular system and related components. As such, the system can be configured to meet user requirements.

[0042] The MFDS shown in Figure 4 has a core system 401 ("Core") that consists of a vacuum pump system 403, a vapor condenser (Condenser) 402 and interconnecting means 406 to allow for flow sufficient to provide a vacuum. Each element of the Core has its own modularity and opportunities for control, operation and modification. One or more valves 407 are used in the MFDS to enhance the modularity by allowing various portions of the system to be connected to the Core 401, isolated from other elements, or isolated within the Core 401 to enable repair, maintenance or replacement of individual components. For example, the pump can be isolated from the system for maintenance or repair while the system is still in operation. A user interface and control means ("controller") 408 is also provided for the system. The controller is described hereinafter and is integral to the entire system.

[0043] In a departure from prior art freeze drying systems, the MFDS of the present invention relies on one or more small chambers 404 to contain the samples. This is contrary to the typical arrangement in that instead of having a single large chamber, each of which that will contain many samples, the inventive MFDS uses a multiplicity of chambers, each of which contains a single (or a small number) of samples. Not only does this provide a means for processing smaller batches; it also allows for independent processing of disparate samples. Each of these chambers will be mounted to the system via a hardware interface 405, which provides a means to connect the container such that processing can be undertaken. The physical interface 405 connection is preferably provided via a clamping mechanism 501 or a set of clamping mechanisms as shown in Figure 5 (Figure 5a shows an open position example, and Figure 5b shows a closed position example). The clamping could alternatively (or supplementally) be provided by the vacuum drawn via the vacuum pump system. In this case, the container can be sealed to the interface without any specific mechanical clamping mechanism. Alternatively, the interface can be implemented by magnetic, electromagnetic or other electrically or electronically controlled means. While it is possible to rely on a container-to-interface edge for sealing, the preferred embodiment will include a material gasket 502 to allow for positive sealing for the vacuum. This is an important distinction from small, laboratory freeze drying systems that simply rely on a resilient stopper (e.g., rubber or cork) to provide the physical interface.

[0044] Each of the smaller chambers 404 provided in accordance with the present invention (referred to here as "containers") will provide an independent space for the independent processing of enclosed samples. These are connected to the other components of the MFDS system via interconnecting means 406 provided either via the container interface or via alternative connections already part of the container with a mating connection at the point of container mounting.

[0045] A key element of the present invention is that each container is connected to the system in a means that allows for independent control by the system controller. Unlike smaller laboratory systems which include manual valves to allow a connection to be sealed when not being used, the MFDS uses a system of automatically controlled valves that not only seal unused connections but to also provide a controlled means to manage the introduction and removal of containers from the system.

[0046] While the specific size and shape of the container 404 is not important as long as it meets the interface requirements of the MFDS and can withstand the vacuum and temperature requirements of the MFDS, one may consider such a container as being similar to a standard commercial kitchen food container. Constructed of metal (e.g., aluminum or stainless steel) or high strength plastic (e.g., acrylic) or glass, the container is designed to allow it to be used for the purposes of freezing the sample as well. For example, when the sample is ready for freezing it is placed in a container, sealed with a separate compatible lid that is not unlike a common food storage lid (e.g., Tupperware® or Rubbermaid®) and placed in a freezer. An example is illustrated in Figure 6, with a container 404 being mated with removable lid 601. After sufficient time to ensure the sample is frozen, the container's lid is removed and the container is connected to the MFDS via the interface 405. The lid can be cleaned for its next use or can be disposed of if intended to be disposable.

[0047] Various enhancements are easily envisioned for the container. Among these are specific ridges, grips and other mechanical elements to enhance ease of use. These may also be used to enable the container to be used as a standard food storage container when not being used as part of the MFDS. Moreover, specific mechanical elements may be included to insure proper alignment, direction or to otherwise comply with specific features or functions of the interface. Further, the container may include certain mechanical design elements to enhance sublimation and temperature control. For example, the container may incorporate ridges or spikes that protrude into the sample to increase thermal conductivity useful during the processing, particularly during secondary drying.

[0048] Container 404 can hold another internal container to effect processing. In this case, one can envision a specific container used for freezing that fits inside the container 404 for processing. This may be beneficial if the internal container provides some additional benefit (e.g., shape, portion size). Moreover, the internal container may include a perforated platform or other structure that allows for more surface area to be exposed to the vacuum for sublimation by raising the sample above the bottom of the outer container 404. Similarly, the internal container may also hold a separate container in which the sample is placed.

[0049] Further, the design of the container may be such that it is in fact a multi-part design to enhance temperature conduction or insulation. For example, as the cross-sectional view of the container shows in Figure 7, the container may be constructed of two layers of material, one layer 702 inside the other 701, with a gap 703 between the two layers. Should the gap 703 be evacuated, the container would act like vacuum bottle and insulate an enclosed sample. Alternatively, the gap 703 may be filled with a material like those used in synthetic ice packs to provide more control over the rate of warming of the sample. Still another alternative is to fill the gap 703 with a material that can be warmed during the process, particularly during secondary warming, to assist with sample processing. This can be done in combination with a warming circuit in order to initiate warming a specified by the Controller. Such a warming circuit may be part of any sensor connection scheme.

[0050] The container may be designed to incorporate one or more sensors as shown in Figures 8a and 8b. These sensors 801 may provide the ability to measure certain parameters in order to monitor the progress of the processing. Sensors used for this purpose may include moisture, temperature and/or weight sensors. Sensors like vacuum sensors and others may also be used to monitor system performance and status. Similarly, the container may include one element of a multi-element sensor arrangement that becomes viable when the container is connected to the mechanical interface 405. An example may be a sensor that measures moisture via electrical conductance and for which one part included in the container combines with another part in the interface in order to provide the sensor capability. Additionally, any sensor may provide indications on the container or may interface with some other element within the system in order to provide information for alarm conditions, processing status and the like.

[0051] The sensors 801 may be affixed to the container in any suitable manner, including direct integration into the container structure as illustrated in Figure 8b. The container may include a specific connection 802 (e.g., multi-pin plug or socket) to the sensors 801 that will be compatible with a mating connection to the controller at the time of meeting the interface. It will be understood that connection to sensors may include wireless, optical or other non-mechanical means.

[0052] The MFDS controller is responsible for managing and controlling all of the functions of the MFDS. The controller is designed to optimize the system performance as well as minimize potential energy usage. Input to the controller can come from a range of sensors and, based on the information received, generate various control signals. [0053] While other systems typically have a controller mechanism, the MFDS Controller is far more comprehensive in that it effectively controls the process in each container. This is done by monitoring the state of each container and its contents and controlling various components affecting the processing of the contents. Because of the system design, each container can easily have a processing scheme tailored to the specific sample in each container. Barring specific information about the sample, the controller will default to a standard program based on various parameters and, if available, sensor input.

[0054] The controller receives information from one or more sensors. Among the sensors being employed, vacuum sensors will keep the controller informed of the level of vacuum being held within the system as well as within each container or elsewhere in the system. This enables the controller to modulate the vacuum pump system to minimize wasted energy. When the vacuum measurements are within an acceptable range, the vacuum pump system can be turned off. This saves energy as well as saving valuable time between maintenance on the pump and other system components. When the vacuum measurements are outside the acceptable range, the vacuum pump system is turned on to bring the system back into an acceptable range.

[0055] In addition to having memory sufficient to recall operating instructions and parameters, the controller will preferably have enough memory to store information about the system and specific processing. As such, the controller will be able to present to the user various information about the status of the system, including performance metrics of one or more of the system components. Additionally, the controller will be able to recall for the user details of some or all samples processed. Such recall may include at least information about the timing of the processing and a unique identifier associated with each processing. In addition to providing information to a user, additional information will be available to a service technician or other who will have access to the information. Such information will require some means of access control to reduce the likelihood of inappropriate access and potential damage to the information. [0056] Vacuum systems can be designed to minimize leakage. As a practical matter, however, most such systems, and particularly those with removable connections, will have some leakage. The ability to moderate the operation of the vacuum pump system allows for flexibility in the case of leakage. Most likely, periodic cycling of the vacuum pump system will be able to retain adequate vacuum pressure while not requiring the pump to operate at all times. As will be seen, however, some pump designs are more conducive to short-term operations to overcome leakage and maintain vacuum within a tighter range.

[0057] Designing the controller to monitor vacuum pressure throughout the system will also provide a means to control the introduction and removal of containers from the system. For example, the system may have several containers already being processed - that is, under vacuum - and the user may wish to add a new container. The container is connected to the system via the interface and the controller is initialized for that container to start the process. In the laboratory systems, the initialization required is typically opening the valve at the mount of the container. This is sufficient if the vacuum pump system is always operating and the pump can quickly draw down the vacuum level of the new container. However, if the vacuum pump system is not engaged (as may be the case of the vacuum being within range) it may be temporarily shut down to save energy. While the containers are relatively small, the introduction of a container without having the vacuum pump system engaged could affect the other containers.

[0058] In one possible implementation of the present invention, when a new container is introduced to the system the controller will (1) engage the vacuum pump system if it is not already on, (2) shut off the valves of the other containers, and (3) open the valve for the new container. When the vacuum level of the new container is within an acceptable range, the other valves are opened and all of the containers will continue processing. This process can be initiated, for example, by a user coupling the new container to a free vacuum port, and then actuating the controller to take over via a user interface (e.g., by hitting a "go" button or the like). [0059] Upon getting the "go" signal, the controller will proceed to isolate all of the other containers so that the new container can be tested to confirm that a vacuum is successfully pulled. If successful, the vacuum valves for other containers are reopened and the vacuum continues for all of the containers currently being processed that require a vacuum to be maintained. In the event there is a failure in the new container (e.g., the container does not hold a vacuum due to a bad seal or improper seating) the new container is isolated again, an alert is given (e.g., a buzzer, display, or other indication to the user), and the vacuum valves for the other containers are reopened as appropriate so that the processing of the other containers can continue.

[0060] An advantage to this approach is that potential problems with new containers can be limited. Consider, for example, a case in which a new container does not sufficiently seal in order to hold the required vacuum. If that were introduced blindly into the system with other containers already under vacuum, samples already being processed could be set back in processing or lost altogether. Instead, in accordance with the invention, the controller is able to confirm the presence of a suitable seal prior to risking any negative impact on the other containers. Similarly, if a container were to be the source of a leak it can be identified and isolated. If each container includes vacuum pressure measurement capability, identification likely will come in the form of a multi-step process: (1) close all container valves, (2) measure container pressure for vacuum, (3) determine which container is losing vacuum, and (4) initiate an alert identifying the offending container.

[0061] If the vacuum pressure measurement capability exists only at a system- wide basis, the process is slightly different: (1) close all container valves, (2) open one container valve at a time for a sufficient period to determine if it is leaking, (3) cycle through each container until the offending one is identified and isolated. After correcting the problem or shutting off the valve for the offending unit, the rest of the container valves are opened to allow processing to continue. As before, upon identification, an alert is made to identify the offending container. Unlike prior art systems, adjustments can be made quickly due to the relatively small size of the containers and because achieving the required vacuum is much faster than in other systems.

[0062] When it is necessary or desired to remove a container from the system, it cannot be simply pulled from the associated port. For one thing, the presence of a vacuum on the container may make it difficult, if not impossible, to disconnect the container from the port. Moreover, if one were successful in pulling the container from the port, this action could damage the samples in the other containers. Thus, when a container is to be removed it is preferable to isolate it from the rest of the containers. This can be accomplished via a user interface that allows the user to, e.g., actuate a "release" button that will cause the controller to vent the container to normalize the pressure to ambient, thereby allowing the container to be removed. The rest of the containers will continue to be processed as if the container being removed was never there.

[0063] Although not always necessary, the condenser serves a vital function in most freeze drying systems by capturing the water vapor that is sublimated from the sample. Because of the vacuum, ice from the frozen samples will sublimate directly into a vapor state. This vapor must be dealt with in some manner. Otherwise it could be reabsorbed by the sample, thereby negating the entire process, or the vapor will reach the vacuum pump where it may cause damage. Prior art systems relying on steam ejectors and other techniques will simply remove the water vapor by evacuation. In systems where pumps are used to provide the vacuum, it is important to deal with the water vapor as such pumps usually have difficulty in handling moisture. Some pumps are specifically designed to handle the vapor that will condense in the pump, but these pumps require special systems or additional maintenance and incur additional costs.

[0064] Most commonly, a condenser is situated such that any air that is evacuated from the vacuum chamber is passed through the condenser in order to remove water vapor prior to reaching the vacuum pump. The condenser function will most often be implemented in the form of a typical refrigeration cycle system with an expansion valve, evaporator and compressor. The function can, however, be implemented via a Peltier cooler, a Stirling cycle cooler, or with the use of dry ice. For the purposes of this description, a refrigeration cycle system is discussed.

[0065] In some cases, a refrigeration coil is used directly to condense the water vapor. In other cases the coil chills a surface that condenses the water vapor. The temperature of the condenser depends on the vacuum level required based on the water vapor pressure chart of Figure 1, but is nominally in the -30 to -40⁰C range. This very low temperature ensures that maximum vapor is trapped in the form of ice prior to reaching the vacuum pump and before it may be reabsorbed by the sample during secondary drying.

[0066] In those freeze drying systems using a vapor condenser, time is required after a processing run for the condensed ice to be removed. This is similar to the need to defrost older freezers and usually relies on melting the accumulated ice and catching the resultant water. A novel aspect of the MFDS of the present invention is that the condenser has a removable element. An example implementation is shown in Figure 9. In this figure, condenser coils 901 surround the removable element 902 which can receive flow from the containers via interconnecting means (inlet) 903. Flow is allowed to continue via outlet 904 to the vacuum pump system. A receiving sleeve 905 may or may not be used.

[0067] There are many configurations of the removable element 902, including open-ended, multi-part and other designs. Finally, it is clear that the orientation of the condenser may affect the specific design of the removable element. This removable element is designed to capture the condensed ice and to allow for its easy clearing. The need for ice elimination will vary depending on the water content of the samples and, like most systems, ice can be removed after samples have been processed.

[0068] In the configuration illustrated in Figure 9, the removable element 902 acts as a liner for the sleeve 905. The sleeve has the refrigeration coils 901 positioned therearound, and therefore gets very cold. By being very close (ideally, in contact) with the sleeve 905, the removable element 902 also gets very cold and provides a surface on which the water vapor flowing into the device from inlet 903 will condense and form ice. The ice will be deposited on and adhere to the inner wall surface of the removable element 902. As the ice builds up, it will require removal. One solution is to allow the ice to melt. A better solution is to remove the ice in its frozen state, which is not as messy as allowing it to melt. By removing the element 902 from the sleeve 905, disposal of the ice is facilitated (e.g., by allowing it to melt and pouring the resultant water out or by removing the ice itself from the element 902).

[0069] Another approach is to fabricate the removable element from a mesh such that it is not necessary to conduct cold temperatures from the sleeve 905, but instead will allow the ice to deposit on the sleeve itself and "grow into" the mesh. After sufficient ice is formed, the mesh (element 902) is removed, pulling the ice formation with it.

[0070] With either approach, and particularly for the mesh embodiment, it is advantageous to coat the interior of the sleeve with a non-stick coating. Such a coating can comprise, for example, a fluorinated polymer such as Teflon®.

[0071] In an alternate embodiment (not shown), the sleeve 905 is open at the bottom to allow the inlet 903 and outlet 904 connections to enter through the bottom. Such a configuration may be easier to manufacture and can simplify the alignment of the inlet and outlet ports with respect to the removable element 902.

[0072] The provision of the removable element 902 is further advantageous in that it provides various options to the user. For example, the user can remove the element 902 from the apparatus and then clean it of ice (e.g., by scraping or actively melting ice) and then replace it into the sleeve 905. Alternatively, the user can replace the element 902 with a second removable element, and then simply set the first one aside to melt at room temperature. The two removable elements can be used interchangeably, so that when one needs to be cleaned of ice, the other one is used in its place until it is time to clean that one of ice. [0073] Another way to clear the ice at the end of a cycle is for the condenser to continue operating but to be opened to the environment via a valve means 906. In this case, the built-up ice will simply sublime as it does in modern frost-free freezers. Alternatively, the ice can be allowed to melt and drain out of properly located valve. A heating element or radiation source can be provided to expedite such melting.

[0074] Since the MFDS of the present invention allows for continuous operation with containers being added or removed as they are independently completed, there is a requirement to allow for condensed ice to be removed during processing. Here again, the use of the controller and the ability to close the vacuum lines of each container proves beneficial. Alternatively, a single vacuum valve 907 can be closed at the condenser. When the condenser is full of ice the controller will close each container valve and release vacuum to the system allowing for easy removal of the condenser removable element 902. This removable element can then be cleared of the built-up ice and returned to the condenser unit. At that time, the controller will test the vacuum system to ensure that the entire condenser unit is sealed. If the system holds a suitable vacuum, thereby confirming the condenser unit has been properly reinstalled, the container valves are reopened and processing continues. If, however, the vacuum system shows inadequate vacuum, an alert will be provided and the user will be able to properly install the unit.

[0075] Another variation of the condenser system is the inclusion of multiple condenser units. In this case, the controller would be able to switch between the units in order to allow one to be cleared or to deal with the detection of a vacuum leak. As with the single condenser design, clearing one of the multiple condenser units can be accomplished by removing the collection element, by opening a valve, thereby exposing it to the ambient environment and allowing sublimation of the collected ice, or by allowing the collected ice to melt and be drained out of the condenser unit.

[0076] At the heart of any freeze drying system is the vacuum capability. As described above, the required vacuum can be provided in a number of ways, each with advantages and disadvantages. Large systems have the benefit of using non-mechanical pump systems like steam ejectors. In addition to being energy inefficient, ejector systems used to reach the vacuum levels necessary for freeze drying are typically large multistage units. Most freeze drying systems rely on mechanical pumps of some type.

[0077] The challenge for any pump is the ability to achieve and to hold a vacuum sufficient to effect the freeze drying process. An additional requirement in a freeze drying apparatus is to achieve the vacuum quickly to ensure that sublimation occurs before the frozen sample begins to melt, which could damage the sample. For large chambers typical of standard systems, this can limit pump options significantly. Here again the MFDS design of the present invention, which relies on relatively small containers, enhances the options.

[0078] Low-cost pumps that are able to achieve the necessary vacuum level often rely on oil or some other working fluid ("oil-sealed") to help keep the pump sealed and be able to hold the vacuum. This may be acceptable when the pump is used to evacuate an air conditioning system, but without additional protections installed, oil-sealed pumps are incompatible with a system that may allow for oil mist to come into contact with samples, particularly food samples. Further, an oil-sealed pump requires maintenance, including keeping its oil reservoir full and periodically changing the oil.

[0079] An advantage in the design of the MFDS and its small containers is the ability to eliminate some of the evacuation speed requirements. At a fraction of the size of typical freeze drying chambers, containers can be sufficiently evacuated in a fraction of the time. As an example, an available prior art evacuation chamber may have a volume of approximately 7630 cubic inches (approximately 125 liters). A chamber of this size requires a pump with an evacuation rate of multiple liters per minute. For the sake of comparison, an example MFDS container volume is 400 cubic inches (approximately 6.5 liters) so lower evacuation rates are more acceptable. [0080] One pumping scheme that is particularly well suited for MFDS is a peristaltic pump. In a peristaltic pump system, which is a positive displacement pump most often used for supplying dosages in a metered, low volume manner, a flexible tube is compressed by a rotating roller (or set of rollers) thereby advancing the fluid (liquid or gas) through the pump. Typically considered in two parts, such a pump includes a drive means (typically an electric motor) that is used to drive the second component, the head. The peristaltic pump head, shown in Figure 10, is the mechanical element in which the pumping actually occurs. Passing through the pump head is a flexible tube 111 that is sufficiently flexible to allow for a peristaltic motion to be caused. This peristaltic motion within the tube is accomplished by the use of a rotor mechanism 112 compressing a portion of the tube against an opposing force, which in its simplest form is a fixed surface (e.g., wall 113). The rotor mechanism 112, which is connected to the drive means, is turned within the pump head. The rotor may be designed so as to provide an eccentricity that will compress one or more portions of the tube passing through it. This can be considered as a single or multiple lobe cam with the lobe effecting the peristaltic pumping action. In other embodiments, the rotor includes one ore more extensions 114 from the center. Those extensions will either contact the tube directly or will include a roller 115 or other element that will come into contact with the tube. A key goal is to minimize friction and other impediments to the rotational motion. As the rotor turns, the rollers compress the hose captured within the head thereby creating a vacuum.

[0081] Most peristaltic pumps are designed for relatively low volume applications. Because of this, they are not at all suited for applications like traditional freeze drying systems. It is only because of the MFDS design that the potential shortcomings of a peristaltic pump (e.g., low pumping volume and speed) are not a problem. Also, because of the design of peristaltic pumps, the noise produced is greatly reduced over that of standard rotary pumps. This can be important when a consumer wishes to use a system within the home rather than in an industrial or laboratory setting. [0082] Interestingly, an advantage of the peristaltic pump system is that it is not affected by water vapor that is sublimated from the sample. Should the vapor condenser fail or become impaired, the peristaltic pump will not be damaged by the water vapor. For example, the system can continue to operate even if the vapor condenser is temporarily isolated from the rest of the system so that it can be cleaned of ice. Further, MFDS is able to take advantage of the variable speed capability available to many peristaltic pumps that is not usually available to other types of pumps.

[0083] Several other advantages are presented with the use of a peristaltic pump to achieve the necessary vacuum. The pump's reliance on tubing, which can be a section of continuous tubing that is part of the rest of the system or a separate piece connected to the rest of the system, enables the pump to be easily cleaned by flushing a cleaning solution through the tube. This can be an important attribute in the rare instance that liquid or particles enter the vacuum system and cause contamination. Further, after periods of nonuse some systems can become contaminated with dust and in some cases mold. The use of a peristaltic pump allows the system to be cleaned without risk of damage to the pump.

[0084] By design, a peristaltic pump can be easily maintained by removing and replacing the tube segment used within the pump. In some systems, this may involve advancing a long tube through the pump such that a new segment of the tubing is now subject to the rotor and rollers. Otherwise, the tubing segment contained as a part of the pump system can be replaced. This tube advancement or replacement may require the removal or adjustment of the rotor mechanism so the tube can be installed. Adjustment of the rotor mechanism may include retraction of the extensions that include the rollers or allowing the extensions to be folded or disassembled while the rotor mechanism remains in place. In other implementations, the opposing surface may be removed in order to allow tube installation.

[0085] Another advantage of the peristaltic pump is that it can also incorporate modularity. That is, as is done with some health care applications, one or more additional pump heads can be linked to the same pump motor. In MFDS, this can provide a redundant vacuum capability, a parallel channel or in some applications two levels of vacuum. That is, one pump head may be configured for higher volume, quicker evacuation to a specific level and the other may configured for slower evacuation to the ultimate vacuum level. In a parallel or multi-level configuration, heads may be engaged selectively (perhaps by a clutch-type mechanism) or have flow controlled by valve configurations being set by the controller.

[0086] Further, the use of peristaltic pump arrangement does not preclude a separate pump to be used as a forepump or coarse pump, which are often used to quickly reduce the over all vacuum to a level that can then be more easily handled by the main pump or to reduce the pressure difference between the input and output of the system pump. This can be another peristaltic pump or a different type of pump.

[0087] The following example implementation describes a preferred embodiment of the invention. In this implementation, up to four separate containers can contain samples for processing. Prior to processing, each container receives the sample to be processed and is sealed with a removable, flexible lid. The container with the sample is put into a freezer overnight.

[0088] Upon confirming the sample is sufficiently frozen, the flexible lid is removed and the container is installed into the MFDS. Installation includes coupling the container to an open interface to ensure a proper seal and designating the unit as installed at the controller. The coupling can, for example, consist of a male-to-female coupling with an 0-ring seal or the like that connects a lid placed on the container to a port of the MFDS, or a clamping arrangement using suitable gaskets. In addition to identifying the position of the container, the controller allows the user to identify the type of sample to be processed. This may, for example, include general food types (e.g., meat, vegetable) or more specific recipes (e.g., "Mom's casserole") for which a processing profile exists in the controller. [0089] The controller, now knowing the container is installed, engages the condenser to allow it to chill. This step can be done well in advance of installation of the container, but the condenser can reach the proper temperature very quickly. While the condenser is reaching the desired temperature, the controller confirms all vacuum valves not necessary for processing the installed container are closed and the vacuum pump system is engaged.

[0090] As the vacuum pump system starts to draw down the pressure internal to the system, the controller monitors to ensure there are no apparent leaks in vacuum valves or at the interface seal at the installed container. Should a leak be identified, the controller will determine if it requires immediate attention or if it can be circumvented by alternative interconnection routing. In either case, should a leak be identified an alert is provided to the user.

[0091] With no leaks indicated, the condenser and vacuum pump systems continue to achieve the desired levels. Upon reaching necessary levels, the vacuum valve at the interface for the container is opened and the processing begins. The processing follows a standard routine that is modified as input is received from sensors within the container.

[0092] The addition of a second or third container repeats the same steps, but with the condenser and vacuum pump system already engaged additional time will be saved.

[0093] At the conclusion of processing of a particular container, the controller notifies the user. When it is time to remove the container, the controller opens a valve and releases the vacuum on the container thereby making it easier to remove the container. The clamps are opened and the container is removed from the MFDS.

[0094] The processed sample is then removed from the container and stored in an appropriate storage container, such as a vacuum-sealed bag, that can be stored wherever desired. Alternatively, the removable lid is reinstalled on the container and the container and the sample are stored. [0095] Many variations are possible in accordance with the invention. One such variation is to package the MFDS in a manner much like a home appliance. This packaging may allow it to be installed under a kitchen counter as one may typically find an automatic dish washing machine or other appliance. Additionally, the packaging may present one or more finishes to match decor constraints. Such packaging may also allow for changing panels or other coverings in order to alter the appearance at any time.

[0096] Packaged as a home appliance, a further enhancement is the routing of ventilation air from the condenser unit or other components to warm one or more containers and thereby enhance secondary drying. This can reduce the need for (or eliminate altogether) additional circuitry or other accommodations to warm the sample beyond what can be done by exposure to ambient temperatures.

[0097] When packaged for installation or use in a home, a further enhancement of the system to enable easy maintenance is for the system or subsets of the system to be mounted on rails or rollers. This will enable easy access by allowing the system or subsystems to be pulled out of the packaging and then returned to the operating position when maintenance has been completed.

[0098] An alternative packaging design will allow various subsystems to be packaged differently and connected only via various plumbing and control means. For example, the subset of the system that includes the interface may be packaged such that it can be installed for easy access by the user and the remainder of the system may be packaged such that it can be hidden from the user's view. This can allow the unit take up less valuable mounting space.

[0099] While freeze drying requires the actual freezing of a sample, it is clear that this invention is also applicable to simple vacuum drying. That is, this invention may be used to enable drying of moist items that are not frozen. A simple example of this is the making of jerky and other dried food products. An enhancement may include specialized adapters. [0100] To aid the user- friendliness of an MFDS in accordance with the invention, a container may be automatically sensed, at which point a user will be automatically prompted for information about the sample contained in the container.

[0101] The controller can be enhanced to provide additional features to make MFDS more user-friendly. One enhancement is that it can be easily updated by a user. The MFDS controller can have the capability to update its firmware/software via any number of means, including a flash memory card or via a network connection. In addition to updating system functions, updating the controller can also lend to new and specific processing profiles based on new foods, food types, recipes and the like. This would be comparable to microwave ovens that include various preset parameters based on the type of food to be cooked, thawed or warmed.

[0102] As a further enhancement for the controller, using a network connection the controller can access an Internet site that may contain manufacturer provided or user-generated information allowing more customization of process profiles based on the specific food. Still further, when in communication with the Internet site the controller may provide various system performance parameters like hours of operation and subsystem performance in order to indicate when maintenance may be required. As an example, a controller may indicate that the system has been operating for 1000 hours, at which time a new container seal may be required. Assuming proper agreements are in place, a new container seal can be automatically delivered to the user for replacement.

[0103] A benefit of using the MFDS is the ability to store food for long periods without incurring additional energy, unlike a freezer. As such, an enhancement of the controller is to maintain a measure of energy consumption so that the user can be made aware of how much energy has been used and, by inference, how much energy is being saved over the usage of other appliances.

[0104] Another enhancement for the MFDS is the ability to provide specific information to the user about a particular sample that has been processed. Such information may include details about the process, date and a tracking number for later retrieval of specific information. Building on this enhancement is the potential of providing a print-out of the information, perhaps in the form of a label that can be readily attached to the container used to store the processed sample. In the case of incorporating a network connection, the controller may be able to transmit the information to another computer for storage, printing or directly to a printer.

[0105] A specific enhancement to the vapor condenser is the inclusion of various elements to increase the surface area used to condense water vapor. For example, the internal surface of the vapor condenser may include fins, spikes or other means to provide more chilled area on which to condense the water vapor.

[0106] Further enhancements to the vapor condenser include the ability to induce melting of collected ice and use of a pump to remove melted ice. This pump may be the same pump as that used for the vacuum system, a separate channel on the same pump system or a separate pump.

[0107] With respect to the vacuum pump system, it is understood that any drive mechanism may be employed to drive the pump head. Such drives may include non-electric motors or engines or even manually operated drive means. Additionally, gearing between the drive means and the pump head may be changed in order to accommodate special requirements or alternative drive means.

[0108] Enhancing the modularity of the MFDS is the ability to allow the controller to suspend processing for some period in order to remove, replace or maintain any element of the system. For example, if the vacuum pump requires maintenance, the valves controlling the vacuum connection to the containers will be closed in order to allow the vacuum pump to be removed, replaced and a suitable vacuum level achieved prior to reopening the container vacuum valves.

[0109] It is noted that the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and various modifications and adaptations are possible in view of the above teachings. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed herein, but that the invention include all embodiments falling within the scope of the appended claims.

Claims

What is claimed is:

1. A freeze drying system comprising: a vacuum pump; a plurality of ports coupled to said vacuum pump; a connector associated with each port, each connector being adapted to couple vacuum from the associated port to a vacuum container; a vacuum valve associated with each port for selectively controlling vacuum at the port; and a controller for controlling said vacuum valves to allow vacuum to be selectively applied to vacuum containers via said ports.

2. A freeze drying system in accordance with claim 1, further comprising: a vacuum container connected to one of said ports; and a sensor arranged to sense a parameter in said vacuum container; wherein said controller is coupled to monitor said sensor and control the application of vacuum to said container in response to said parameter.

3. A freeze drying system in accordance with claim 2 wherein said parameter comprises at least one of moisture, temperature, weight and vacuum.

4. A freeze drying system in accordance with claim 1 wherein said pump is a peristaltic pump.

5. A freeze drying system in accordance with claim 5 wherein a second pump is used to provide initial evacuation prior to engagement of the peristaltic pump.

6. A freeze drying system in accordance with claim 1, further comprising: a vacuum container connected to one of said ports; said vacuum container comprising a sealable storage container suitable for freezing portions of food in a home freezer.

7. A freeze drying system in accordance with claim 6 wherein said vacuum container includes an integrated valve to enable coupling of the container directly to its associated port.

8. A freeze drying system in accordance with claim 7 wherein said integrated valve comprises a solenoid electronically controlled by said controller.

9. A freeze drying system in accordance with claim 1, further comprising: a vacuum container connected to one of said ports; said vacuum container comprising means for enabling a processing state of the container to be monitored.

10. A freeze drying system in accordance with claim 1, further comprising a vapor condenser coupled between said vacuum pump and said ports.

11. A freeze drying system in accordance with claim 1 wherein: each port includes an interface for coupling the port to a vacuum container; and the interface is adapted to allow for various container sizes and shapes to mate therewith and enable a vacuum to be reached.

12. A freeze drying system in accordance with claim 1 further comprising: a sensor associated with at least one of said ports, said sensor being coupled to said controller; wherein said controller is responsive to said sensor for detecting the presence of a vacuum container at the associated port.

13. A freeze drying system in accordance with claim 1 further comprising: a user interface associated with said controller; wherein said controller is responsive to user input entered via said user interface to control said vacuum valves and thereby process samples to which said vacuum is applied according to a sample specific scheme.

14. A freeze drying system in accordance with claim 1, further comprising: a plurality of vacuum containers connected to different ones of said ports; sensor means associated with said controller for detecting the coupling of an additional container to one of said ports; said controller being responsive to said sensor means for:

(1) actuating said vacuum pump if it is not already running,

(2) closing the vacuum valves associated with the containers previously connected to ports,

(3) opening the vacuum valve associated with the additional container, and

(4) opening the vacuum valves associated with the containers previously connected to ports after the vacuum level of the additional container has reached a predetermined value.

15. A method for freeze drying samples of food or the like, comprising the steps of: providing a vacuum pump; coupling said vacuum pump to a plurality of ports each adapted to couple vacuum from the vacuum pump to an associated vacuum container; providing a plurality of vacuum valves arranged to allow the isolation of individual ports from the other ports; and controlling said valves to selectively provide said isolation in order to allow the coupling and decoupling of vacuum containers to and from said ports and to individually control the processing of samples to be freeze dried within the vacuum containers.

16. A method in accordance with claim 15 comprising: controlling said valves to isolate said pump from said ports while said samples continue to be processed.

17. A method in accordance with claim 15 comprising: monitoring parameters within said vacuum containers during processing of said samples; and controlling said processing in response to said parameters.

18. A method in accordance with claim 15 comprising: providing a removable element to facilitate the capture of ice that is accumulated during the processing of said samples; and removing said removable element to dispose of said ice.

19. A method in accordance with claim 15 comprising: placing a sample to be freeze dried into a sealable storage container; placing said container into a freezer; removing said container from said freezer after the sample is frozen; coupling said container with the frozen sample therein to one of said ports; and drawing a vacuum in said container to freeze dry the frozen sample.

20. A method in accordance with claim 15 wherein the coupling of a vacuum container to one of said ports comprises the steps of: actuating said vacuum pump if it is not already running; closing vacuum valves associated with the containers previously connected to ports; opening a vacuum valve associated with the additional container; and opening the vacuum valves associated with the containers previously connected to ports after the vacuum level of the additional container has reached a predetermined value.