Freeze-drying method and device

Abstract

The invention relates to a freeze-drying device comprising: an evaporation chamber (5) comprising heating means (15, 16), a condensing chamber (10) communicating with the said evaporation chamber, the said evaporation chamber (5) and the said condensing chamber (10) being mounted secured to one another about an axle (30) capable of rotating, characterized in that the device further comprises: a products inlet and outlet (1, 8) which are connected to the said evaporation chamber (5) by flexible connectors, the products inlet and outlet (1, 8) being mounted fixedly with respect to the evaporation chamber, and a motor (12) driving the said axle (30) on itself with the following back-and-forth movement: a first movement driving the said axle (30) in a first direction of rotation with an angle of rotation (1) of between 5 and 90, and a second movement driving the said axle (30) in a second direction of rotation, opposite to the first angle of rotation, with an angle of rotation (2) of between 5 and 90.

Claims

1. Freeze-drying device comprising: an evaporation chamber (5) comprising means (15, 16) of heating said evaporation chamber (5) that are configured to sublimate the water contained in the frozen products intended to be placed in the evaporation chamber (5), a condensing chamber (10) communicating with said evaporation chamber, and comprising means (17, 18) of cooling said condensing chamber (10) that are configured to transform the vapor coming from said evaporation chamber (5) into ice, said evaporation chamber (5) and said condensing chamber (10) being mounted secured to one another about a rotatable axle (30), characterized in that the device further comprises: a products inlet and outlet (1, 8) connected to the evaporation chamber (5) by flexible connectors, the products inlet and outlet (1, 8) being mounted fixedly with respect to the evaporation chamber, and a motor (12) driving said axle (30) about itself with the following back-and-forth movement: a first movement driving said axle (30) in a first direction of rotation with an angle of rotation (1) between 5 and 90; and a second movement driving said axle (30) in a second direction of rotation, opposite to the first angle of rotation, with an angle of rotation (2) between 5 and 90.

2. The freeze-drying device according to claim 1, characterized in that said evaporation chamber (5) comprises compartments formed by partitions (40) extending over only a portion of the height of said evaporation chamber (5) said motor (12) driving said axle (30) about itself according to a third movement with an angle of rotation of between 90 and 180, said third movement being coupled to an inclined position of said evaporation chamber (5) so as to move the products by gravity between two consecutive compartments.

3. The freeze-drying device according to claim 2, characterized in that said inlet (1) comprises a loading chamber (41) partitioned by two locks (2a 2b), and in that said outlet (8) comprises an unloading chamber (42) partitioned by two locks (9a, 9b).

4. The freeze-drying device according to claim 3, characterized in that the opening of said lock (2b) separating said inlet (1) from said evaporation chamber (5) and the opening of said lock (9a) separating said outlet (8) from said evaporation chamber (5) are synchronized with said third movement of said motor (12).

5. The freeze-drying device according to claim 2, characterized in that it comprises two condensing chambers (10a, 10b) connected to said evaporation chamber (5) by two different airlocks (4a, 4b), a first condensing chamber (10a) being connected to said evaporation chamber (5) by opening the first airlock (4a) and closing the second airlock (4b) so as to use said first condensing chamber (10a) to trap vapor coming from said evaporation chamber (5), a second condensing chamber (10b) then being regenerated during use of said first condensing chamber (10a) and vice versa.

6. The freeze-drying device according to claim 5, characterized in that it comprises two vacuum pumps (6a, 6b), a first vacuum pump (6a) connected to said first condensing chamber (10a) and a second vacuum pump (6b) connected to said second condensing chamber (10b).

7. The freeze-drying device according to claim 2, characterized in that said evaporation chamber (5) is inclined between said inlet (1) and said outlet (8).

8. The freeze-drying device according to claim 2, characterized in that the partitions (40) of said evaporation chamber (5) have two different shapes mounted alternately in the evaporation chamber (5), the two shapes having axially offset openings (39) intended for the passage between two compartments of the product to be freeze-dried.

9. The freeze-drying device according to claim 2, characterized in that said motor (12) is configured to drive said axle (30) according to a fourth movement complementary with said three movements, said fourth movement driving said axle (30) in a direction opposite to the direction of the third movement with an angle of rotation (4) of between 90 and 180 so as to move the products between two consecutive compartments of said evaporation chamber (5).

10. The freeze-drying device according to claim 1, characterized in that the evaporation chamber is disposed laterally relative to the condensing chamber(s).

11. The freeze-drying device according to claim 1, characterized in that said evaporation chamber (5) includes a double outer wall, said heating means (15, 16) being configured to move a heat transfer fluid in a space formed between the two walls of said evaporation chamber (5).

12. The freeze-drying device according to claim 1, characterized in that said flexible connectors have a plurality of stainless steel coils.

13. A freeze-drying method implemented by a device according to claim 1, the method comprising the steps of: filling said evaporation chamber (5) with products, frozen or not, by opening said products inlet (1), when the products are not frozen, cooling the evaporation chamber by the cooling means until the products are frozen, once the products are frozen, placing the evaporation chamber (5) and the condensing chamber (10) under a vacuum, heating said evaporation chamber (5) by said heating means (15, 16) until obtaining sublimation of the water contained in the frozen products contained in said evaporation chamber (5), cooling said condensing chamber (10) by cooling means (17, 18) so as to trap the vapor entering into said condensing chamber (10), agitation of said evaporation chamber (5) and of said condensing chamber (10) by rotation of said axle (30) about itself in two repeated complementary movements throughout the sublimation time: a first movement driving said axle (30) in a first direction of rotation with an angle of rotation (1) of less than 180; and a second movement driving said axle (30) in a second direction, opposite to the first direction of rotation, with an angle of rotation (2) of less than 180, and extraction of the products from said evaporation chamber (5).

14. The freeze-drying method implemented by a device according to claim 2, the method comprising the steps of: filling the evaporation chamber with products, frozen or not, by opening the products inlet, when the products are not frozen, cooling the evaporation chamber until the products are frozen, placing the evaporation chamber (5) and the condensing chamber (10) under a vacuum, heating said evaporation chamber (5) by said heating means (15, 16, 31) until obtaining sublimation of the water contained in the frozen products contained in said compartments of said evaporation chamber (5), cooling said condensing chamber (10) by said cooling means (17, 18) so as to solidify the vapor entering into said condensing chamber (10), agitation of said evaporation chamber (5) by rotation of said axle (30) about itself in two repeated complementary movements throughout the length of stay in each compartment; a first movement driving said axle (30) in a first direction of rotation with an angle of rotation (1) between 5 and 90, a second movement driving said axle (30) in a second direction, opposite to the first direction of rotation, with an angle of rotation (2) of between 5 and 90, displacement of the products between two consecutive compartments by displacement of said axel (30) according to a third movement with an angle of rotation (3) of between 90 and 180, said third movement being coupled to an inclined position of the evaporation chamber (5), and extraction of the products from said evaporation chamber (5).

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The way to implement the invention as well as the advantages deriving therefrom will be clearly seen from the description of the following embodiment, supported by the appended figures in which:

(2) FIG. 1 is a schematic structural representation of a freeze-drying device according to a first embodiment of the invention;

(3) FIGS. 2a, 2b and 2c are sectional views of the position of a partition relative to the evaporation chamber in four different positions of the freeze-drying device of FIG. 1;

(4) FIG. 3 is a schematic structural representation of a freeze-drying device according to a second embodiment of the invention;

(5) FIGS. 4a to 4d are sectional views of the position of a partition relative to the evaporation chamber in four different positions of the freeze-drying device of FIG. 3;

(6) FIG. 5 is a schematic structural representation of a freeze-drying device according to a third embodiment of the invention; and

(7) FIGS. 6a to 6e are sectional views of the position of two consecutive partitions relative to the evaporation chamber in five different positions of the freeze-drying device of FIG. 5.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

(8) FIG. 1 illustrates a freeze-drying device comprising an evaporation chamber 5 and a condensing chamber 10. An inlet 1 in the form of a hopper is connected to the evaporation chamber 5 by means of a flexible connector. The hopper is further equipped with a first lock 2 so as to add products to be freeze-dried when the lock 2 is open. An outlet 8 in the form of a hopper is also connected to the evaporation chamber 5 by means of a flexible connector. The hopper is further equipped with a second lock 9 so as to extract freeze-dried products when the lock 9 is opened. The locks 2 and 9 also make it possible to guarantee the seal and sterility of the chambers 5, 10. For example, locks 2, 9 of the Agilent Technologies or Gericke brands can be used. As a variant, the invention can be implemented with a single inlet/outlet performing both functions of adding and extracting products.

(9) The evaporation chamber 5 and the condensing chamber 10 are disposed in the extension of one another and independent of each other, i.e. the two chambers form two axially offset spaces. As a variant, the condensing chamber 10 can be disposed around the evaporation chamber 5, so that the two chambers are concentric in this case.

(10) The evaporation chamber 5 has a double outer wall in which a heat transfer fluid circulates to heat the evaporation chamber 5. Preferably, the internal surface of the evaporation chamber 5 has a mirror-finished so as to favor the sliding of the load as well as to minimize the angle of slope.

(11) The heat transfer fluid is heated by an external device connected to the double wall by a fluid inlet 15 and a fluid outlet 16. A steam inlet 31 is also connected to the evaporation chamber 5 in order to sterilize the evaporation chamber 5.

(12) Said heating means 15, 16 make it possible to sublimate frozen products disposed in the evaporation chamber. As a variant, the heat transfer fluid can be heated by a heat exchanger coupled to an external heat source.

(13) The products can be added in frozen form through the inlet 1. As a variant, the products can be frozen directly in the evaporation chamber 5. In this embodiment, the products are added at ambient temperature and the heat transfer fluid circulating in the outer double wall is cooled to a very low temperature, for example on the order of 60 C., so as to produce the freezing of the products prior to the evaporation step. Freezing can also be done in the inlet 1. For example, the freezing can be achieved directly in pellets by means of a gravity drip falling in a nitrogen stream.

(14) The condensing chamber 10 is connected to the evaporation chamber 5 via an airlock 4. The airlock 4 is configured to allow the vapor to pass between the evaporation chamber 5 and the condensing chamber 10. Furthermore, the airlock 4 can include a screen or filter allowing the vapor to pass while retaining the particles of product that could be carried along by the water vapor. Preferably, the filter is made of Gore-Tex, registered trademark.

(15) The condensing chamber 10 includes an ice trap 11 with the shape of a coiled tube in which a heat transfer fluid circulates, for example liquid nitrogen. The heat transfer fluid is produced by an external device and flows into the tube through an inlet 17 to an outlet 18. As a variant, the heat transfer fluid can be cooled by a heat exchanger coupled to an external source of cold.

(16) The cooling means 17, 18 are implemented when the airlock 4 is open and the vapor penetrates into the condensing chamber. The vapor than freezes on the tube of the ice trap 11. The number of coils and the cross-section of the tube forming the ice trap 11 are determined as a function of the quantity of vapor to be recovered.

(17) A steam intake 32 is also connected to the condensing chamber 10 in order to sterilize the condensing 10 and evaporation chambers prior to starting the freeze-drying process per se. To do this, in a step prior to freeze-drying, the airlock 4 is opened and the steam is added to the two chambers 5, 10.

(18) During the process itself, the steam injected by the steam injection nozzle 32 causes the melting of the ice on the ice trap 11. A drain 33 extracts the vapor injected for evaporating the ice contained in the condensing chamber 10 as well as the steam generated for the sterilization.

(19) The condensing chamber 10 is also connected to a vacuum pump 6 by means of a pipe fitted with a valve 7 Said vacuum pump 6 is configured to evacuate the condensing chamber 10 and the evaporation chamber 5 when the airlock 4 is opened. When the vacuum is created in said two chambers, the valve 7 is kept open and the vacuum is preserved by the condensation of the vapor onto the ice trap 11.

(20) The inlet 1 and the outlet 8 of the inlet and outlet hoppers are connected to the evaporation chamber 5 by sterile flexible sleeves. Advantageously, the heating and cooling means of the two chambers 5, 10 as well as of the vacuum pump 6 are also connected to the respective chambers by flexible connectors. Preferably, the flexible connectors are produced from stainless steel in order to fulfill the sterility requirements. Advantageously the flexible connectors have coils so as to limit the strain-hardening of the stainless steel. As a variant, other materials can be used without changing the invention.

(21) The function of the flexible connectors is to connect a fixed external element, in this case the supply and discharge hoppers, to the chambers 5, 10 so as to ensure a connection of said elements with the chambers 5, 10 when said chambers are rotated about themselves by the motor 12. The flexural capacity of said connectors thus makes it possible to absorb the displacements of the chambers 5, 10 relative to the external elements. The length of the connectors is also chosen to ensure that the connection is maintained during rotation of the chambers 5, 10. For example, Stubli brand flexible connectors can be used.

(22) The two chambers 5, 10 are fixedly mounted on an axle 30. Preferably, the two chambers are cylindrical and the axle 30 passes through the center of the two flat faces of the cylinders so as to distribute the mass of the chambers 5, 10 uniformly around the axle 30. In FIG. 1, the axle 30 is connected and secured to the end of the condensing chamber 10, opposite to the end connected to the evaporation chamber 5.

(23) As a variant, the axle 30 can be connected and secured to the evaporation chamber 5. Furthermore, the axle 30 can be held, freely rotatable, by supports. The axle 30 is rotated by a motor 12

(24) According to the invention, two opposite rotational movements relative to their central axis are induced by the axle 30 driven by the motor 12 and are limited in amplitude so as to create a back-and-forth movement. FIG. 2 illustrates the positions of the axle 30 during said back-and-forth movement. In a first position, illustrated in FIG. 2a, the axle 30 is not rotated by the motor 12. A first movement of the motor 12, illustrated in FIG. 2b, drives the axle 30 about itself and consequently the evaporation and condensing chambers in a first direction of rotation with an angular displacement 1 of less than 180.

(25) A second movement of the motor 12, illustrated in FIG. 2c, drives the axle 30 about itself and consequently the evaporation and condensing chambers in a second direction of rotation, opposite to the first direction of rotation, with an angular displacement 2 substantially equal to the angular displacement of the first movement. The back-and-forth movement thus corresponds to an oscillation of the axle 30, i.e. a rotation of the axle 30 about itself in one direction then in the other. The axle 30 therefore does not make a complete rotation, thus limiting the risk of winding the flexible connectors connecting the external devices to the chambers 5, 10. On the contrary, the flexible connectors are configured to be deformed and absorb the displacements of the chambers 5, 10 during rotations so as to maintain a sealed and sterile connection.

(26) The rotational movements thus make it possible to avoid the clumping of products in the evaporation chamber 5 during freeze-drying while limiting the time of the freeze-drying process. Advantageously, the evaporation chamber 5 also includes baffles disposed inside the evaporation chamber 5.

(27) The baffles extend radially towards the interior of the evaporation chamber 5 and enable the mixing of the products during freeze-drying to be improved. For example, Palamatic plowshare mixers can be used.

(28) The axle 30 can be mounted horizontally relative to the cylindrical body of the chambers 5, 10. In this embodiment, the device advantageously includes means of pivoting the axle in the vertical plane allowing the products disposed in the evaporation chamber 5 to be guided towards the outlet 8 when the freeze-drying is completed.

(29) As a variant, the axle 30 can be mounted with a bias, i.e. tilted in the vertical plane so as to guide the products towards the outlet 8 during the freeze-drying process. In this embodiment, the outlet 8 is lower than the inlet 1 so as to use gravity to move the freeze-dried products towards the outlet 8.

(30) Moreover, because the freeze-drying process is particularly dependent on the differences in temperature and pressure, the chambers 5, 10 are preferably equipped with instruments such as temperature sensors 20, 24 and pressure sensor 21.

(31) Two sensors 20, 21 are disposed in the evaporation chamber 5 to monitor the temperature and pressure in the evaporation chamber 5. A third sensor 24 is disposed in the condensing chamber 10 to monitor the temperature of the condensing chamber 10. An operator can then follow the freeze-drying process by means of the sensors 20, 21, 24 and estimate the quantity of water eliminated from the products over time. Thus, it is possible to determine the exact moment for which a desired concentration of water is reached in order to stop the freeze-drying.

(32) To carry out freeze-drying by means of the previously described device, an operator opens the lock 2, while the lock 4, the valve 7 and the lock 9 are closed. Products to be freeze-dried are thus added into the evaporation chamber 5, for example previously frozen products. The lock 2 is then closed and the valve of the airlock 4 is opened to place the two chambers 5, 10 in communication.

(33) A vacuum is then produced by opening the valve 7 and actuating the vacuum pump 6. When the vacuum is created, the vacuum is essentially maintained by the condensation of the vapor on the ice 11. The next step consists of carrying out the sublimation of the water contained in the frozen products. To do this, the frozen products are heated by actuating the heating means 15, 16 of the evaporation chamber 5 and actuating cooling means 17, 18 of the condensing chamber 10. For example, the temperature of the products in the evaporation chamber 5 is shifted from 30 C. to 25 C. under a vacuum of 6.1 hPa.

(34) The water from the frozen products is then sublimated and penetrates into the condensing chamber 10 in vapor form where it is frozen and trapped in the condensing chamber 10 by the ice trap 11 the temperature whereof is preferably between 50 C. and 60 C. For example, the screen or membrane, preferably made of Gore-Tex, at the airlock 4 can prevent the dispersal of product particles if the evaporation speed is high.

(35) During this time, the motor 12 rotates the axle 30 about itself in the two movements previously described. Said movements are repeated alternately throughout the time of sublimation. For example, the motor can be a brushless electric motor. Preferably, the motor is an electric motor having a plurality of operating positions for which the magnetic field of the stator corresponds to an angular position of the rotor. Instead of moving the magnetic field of the stator circularly to drive the electric motor in a circular movement, the invention proposes to use the motor to perform a back-and-forth movement. For example, an electric motor that has four pairs of poles is conventionally rotated by successively supplying the consecutive pairs of poles: the first pole pair, the second pole pair, the third pole pair, the fourth pole pair, the first pole pair, etc. The back-and-forth movement can be generated by supplying the first pole pair, then the second pole pair, then the first pole pair, then the fourth pole pair, then the first pole pair, then the second pole pair, etc.

(36) To reduce the weight born by the rotor of the motor, the evaporation 5 and condensing 10 chambers can be mounted on wheels movable in the direction of rotation and configured to support the weight of the chambers.

(37) When the duration of freeze-drying is reached to obtain the desired concentration of water, the valve of the airlock 4 is closed and the heating means 15, 16 and cooling means 17, 18 are stopped. The lock 9 is opened and the freeze-dried products are extracted from the evaporation chamber 5 through the outlet 8. To extract the trapped ice in the condensing chamber 10 and sterilize the entire facility, steam is added to the condensing chamber 10 through the steam injection nozzles 31, 32 in order to melt the ice and sterilize the two chambers 5, 10. The steam thus contained in the two chambers 5, 10 is extracted through the drain 33 or through the outlet 8 when the product is extracted from the condensing chamber 10. To finish, the lock 9 is reclosed, the two chambers 5, 10 are cooled by means of the connectors 15-18 and a new freeze-drying can be performed.

(38) FIG. 3 illustrates a second embodiment wherein the evaporation chamber 5 includes partitions 40 extending over only a portion of the height of the evaporation chamber 5 forming compartments between said partitions 40.

(39) Preferably, because the evaporation chamber 5 is cylindrical, the partitions 40 extend radially relative to the evaporation chamber 5. The top of each partition 40 is provided with an opening 39 intended to allow the passage of products between two consecutive compartments. FIG. 4 shows a sample implementation of these partitions by the presence of an opening at the upper part of the partition 40.

(40) The device further comprises an inlet 1 connected to the evaporation chamber 5 by a loading chamber 41 so as to add products to be freeze-dried. To do this, the loading chamber 41 is partitioned by two locks 2a, 2b. Products are added to the loading chamber 41 from the inlet 1 when the first lock 2a is opened. The first lock 2a is then closed and the second lock 2b is opened so as to add the products into the evaporation chamber 5. The outlet 8 is also connected to the evaporation chamber 5 by means of an unloading chamber 42 also partitioned between two locks 9a, 9b.

(41) In this variant, the motor 12 induces at least three rotational movements of the axle 30 about itself, two of which movements are limited in amplitude so as to create a back-and-forth movement. In a first position, illustrated in FIG. 4a, the axle 30 is not rotated by the motor 12, the evaporation chamber 5 is upright. The opening 39 of the partition 40 is positioned on the upper part of the evaporation chamber 5 and the products are contained in the compartment delimited by the partition 40.

(42) A first movement of the motor 12, illustrated in FIG. 4b, drives the axle 30 about itself and in a first direction of rotation with an angular displacement 1 between 5 and 90. Said low amplitude rotation does not allow the products disposed in the compartment to migrate towards the adjacent compartments because the height of the partition 40 is sufficient to contain the products.

(43) A second movement of the motor 12, illustrated in FIG. 4c, drives the axle 30 about itself in a second direction of rotation, opposite to the first direction of rotation, with an angular displacement 2 substantially equal to the angular displacement of the first movement.

(44) Said low amplitude rotation does not allow the products disposed in the compartment to migrate towards the adjacent compartments because the height of the partition 40 is sufficient to contain the products. The back-and-forth movement thus corresponds to an oscillation of the axle 30, i.e. a rotation of the axle 30 about itself in one direction then in the other.

(45) A third movement of the motor 12, illustrated in FIG. 4d, drives the axle 30 about itself with an angle of rotation 3 between 90 and 180. This large amplitude motion is to allow the displacement of the products between two consecutive compartments because the opening 39 of the partition 40 is disposed downwards.

(46) The axle 30 can be disposed horizontally relative to the cylindrical body of the chambers 5, 10. In this embodiment, the device advantageously comprises means of pivoting the axle in the vertical plane in order to guide the products disposed in the evaporation chamber 5 between two consecutive compartments during the third movement. As a variant, the axle 30 can be mounted with a bias, i.e. inclined in the vertical plane, so as to guide the products against the partition 40 during the back-and-forth movement and between two consecutive compartments during the large amplitude movement.

(47) Preferably, the partitions 40 are produced from metal so as to conduct heat to the center of the evaporation chamber 5. Moreover, because the freeze-drying process is particularly dependent on temperature and pressure differences, the chambers 5, 10 are preferably equipped with instruments such as temperature 20, 24 and pressure 21 sensors.

(48) To carry out freeze-drying by means of the device previously described, an operator or a programmable logic controller opens the lock 2a and the compartment between the locks 2a and 2b is placed under a vacuum. When the vacuum is achieved, the lock 2b is opened and products to be freeze-dried are thus added to the first compartment of the evaporation chamber 5, for example products that were previously frozen. The lock 2b is then closed and the lock 2a is opened once the vacuum is established in the lock, so as to again add products into the loading chamber 41.

(49) The vacuum is initially produced by opening the valve 7 and actuating the vacuum pump 6. When the vacuum is created, the valve 7 remains open and the vacuum pump 6 continues to operate but the vacuum is essentially ensured by condensation of the vapor onto the trap 11.

(50) The next step consists of carrying out the sublimation of the water from the frozen products.

(51) To do this, the frozen products are heated by actuating the heating means 15, 16 of the evaporation chamber 5 and actuating cooling means 17, 18 of the condensing chamber 10.

(52) For example, the temperature of the products in the evaporation chamber 5 is shifted from 30 C. to 25 C. under a vacuum of 6.1 hPa. The water from the frozen products is then sublimated and enters the condensing chamber 10 in vapor form where it is frozen and trapped in the condensing chamber 10 by the ice trap 11 the temperature whereof is preferably between 50 C. and 60 C. For example, the screen at the airlock 4 can prevent the dispersal of product particles if the evaporation speed is high.

(53) During this time, the motor 12 rotates the axle 30 in the three movements previously described. The two back-and-forth movements are repeated alternately during a first cycle. When the holding time of the products in the first compartment is reached, the motor 12 rotates the axle 30 in a third large-amplitude movement so as to move the products from the first compartment towards the second compartment. When the products have been transferred to the second compartment, the lock 2b is opened and new products are added to the first compartment according to the process previously described.

(54) When the freeze-drying time is reached to obtain the desired concentration of water and the first product has been moved between all of the compartments, the compartment between the locks 9a and 9b is under vacuum, the lock 9a is opened and the freeze-dried products are extracted from the evaporation chamber 5 through the unloading chamber 42. The lock 9a is then reclosed and the lock 9b is opened to extract the product through the outlet 8. In the same way as for the intake, the products are added to the lock under vacuum, then once the lock 9a is closed, the vacuum is broken and sterile nitrogen is used to return to atmospheric pressure before opening the lock 9b. Once the chamber 42 is emptied, the lock 9b is closed and a vacuum is reestablished in the chamber 42 while waiting for the next load.

(55) When all of the products have been freeze-dried, the valve of the airlock 4 is closed and the heating 15, 16 and cooling means 17, 18 are stopped. To extract the trapped ice in the condensing chamber 10, steam is added to the condensing chamber 10 through the steam injection nozzles 31, 32 in order to melt the ice and sterilize the two chambers 5, 10.

(56) The steam thus contained in the two chambers 5, 10 is extracted through the drain 33. To finish, the lock 9 is closed again and a new freeze-drying load can be carried out.

(57) FIG. 5 illustrates a third embodiment of the invention wherein two condensing chambers 10a, 10b are connected to the evaporation chamber 5 by two different airlocks 4a, 4b.

(58) The two condensing chambers 10a, 10b are substantially identical and each has an ice trap 11a, 11b supplied by cooling means 17a, 17b, 18a, 18b as described with the first embodiment of the invention. The utilization of two condensing chambers 10a, 10b makes it possible to regenerate one of the chambers while the other is functioning so as to extract the ice stored in water form. To do this, the first chamber 10a is connected to the chamber 5 by opening the airlock 4a while the second chamber 10b is not connected to the chamber 5 by closure of the airlock 4b. Water in ice form is trapped in the first chamber 10a during the freeze-drying process.

(59) When the ice trap 11a of the first chamber 10a is substantially full, the airlock 4b is opened, then the airlock 4a is closed so as to use the second chamber 10b to trap the water vapor. During use of the second chamber 10b, the first chamber 10a is depressurized, then steam is injected by the nozzle 32a so as to evacuate the water trapped in ice form. The first chamber 10a can then be reused when the ice trap 11b of the second chamber 10b is substantially full.

(60) Preferably, when the freeze-drying is carried out under vacuum, each recovery chamber 10a, 10b is connected to a vacuum pump 6a, 6b by means of a valve 7a, 7b. Thus, before opening the airlock 4a, 4b connecting a recovery chamber 10a, 10b to the evaporation chamber 5, the recovery chamber 10a, 10b is placed under vacuum.

(61) Furthermore, during regeneration of the ice trap 11a, 11b, the valve 7a, 7b is opened without actuating the respective vacuum pump 6a, 6b so as to depressurize the condensing chamber 10a, 10b. The injection of steam during regeneration of the condensing chamber 10a, 10b also makes it possible to sterilize said condensing chamber 10a, 10b.

(62) Moreover, as illustrated in FIG. 6, the partitions 40a, 40b have two different shapes mounted alternately in the evaporation chamber 5. Preferably, because the evaporation chamber 5 is cylindrical, the partitions 40a, 40b extend radially relative to the evaporation chamber 5.

(63) Each partition 40a, 40b is disc-shaped, one portion of whichforming substantially one fourth of the discis removed in such a way as to form an opening 39a, 39b. Each opening 39a, 39b is intended to allow the passage of products between two consecutive compartments. The openings 39a, 39b of two consecutive partitions 40a, 40b are axially offset relative to the axis of revolution of the cylinder forming the evaporation chamber 5, as illustrated in FIG. 6a when the motor 12 is not rotating the evaporation chamber 5. The axial offset between the two openings 39a, 39b of two consecutive partitions 40a, 40b is substantially 90.

(64) In the same way as for the second embodiment, when the motor 12 imparts a back-and-forth movement of low amplitude, as illustrated in FIGS. 6b and 6c, the openings 39a, 39b of two partitions 40a, 40b are not positioned at the bottom of the evaporation chamber 5 and the products are contained in their respective compartments.

(65) A first large amplitude movement, illustrated in FIG. 6d induces an axial offset 3 of between 90 and 180 towards the right. The first opening 39a of the first partition 40a is disposed on the left side while the second opening 39b of the second partition 40b is disposed at the lower part of the evaporation chamber 5. The result is that the second partition 40b allows the passage of the product while the first partition 40a retains the products.

(66) A second large amplitude movement, illustrated in FIG. 6e, induces an axial offset 4 of between 90 and 180 towards the left. The first opening 39a of the first partition 40a is disposed at the lower part of the evaporation chamber 5 while the second opening 39b of the second partition 40b is disposed at the left side. The result is that the first partition 40a allows the passage of the product while the second partition 40a retains the products.

(67) These two large amplitude movements make it possible to manage the displacement of products between the compartments.

(68) Preferably, a large amplitude movement is synchronized with the opening of the locks 2b and 9a is intended to allow adding and extracting products from the evaporation chamber 5.

(69) The invention thus makes it possible to freeze-dry products disposed in bulk in the evaporation chamber 5, and continuously, i.e. without stopping the heating means 15, 16 and cooling means 17, 18 between two products to be freeze-dried.

(70) The energy consumption of the freeze-drying device of the invention is 20 to 40% lower than devices of the prior art for the same quantity of products.

(71) Furthermore, it is now possible to run faster cycles thanks to the improvement in heat transfers and materials, and with better control over the freeze-drying process by means of temperature sensors. Because the product is mixed, it is more homogeneous and the information collected by the sensors 20, 21, 24 enables better characterization of the product.

(72) The number of compartments is not limited. It makes it possible to establish the product output frequency. Since one of every two compartments is used so as not to have mixing in two consecutive compartments, the output frequency of the product is calculated in this way: if the holding time of the product is 10 hours, with 20 compartments one product load can be discharged every hour. With 40 compartments and a holding time of 10 hours, the discharge frequency can be reduced to every half-hour.

(73) The output frequency from the evaporator becomes a variable that depends on the number of compartments and the overall holding time in the evaporation chamber 5. The holding time of the product in the freeze dryer can also depend on other factors such as the size of the pellets or granules introduced, and the frequency of the agitation movement.

(74) The invention also makes it possible to freeze-dry products in a way that is automated and sterile because the operator has no physical connection to make at the inlet 1 and outlet 8 of the evaporation chamber 5. Moreover, the heating conditions between two successive compartments can be modified in order to improve the freeze-drying process.

(75) The invention has been implemented efficiently with one evaporation chamber 5 having a capacity between 0.01 and 1 m.sup.3. As a variant, freeze-drying can be done without placing the chambers 5, 10 under a vacuum by using the zeodration technique. In this way the vacuum pump 6 and the valve 7 can be eliminated. As a variant, the freeze-drying device can extract solvents other than water, for example alcohol.