US3529362A

US3529362A - Insert for freeze-drying apparatus

Info

Publication number: US3529362A
Application number: US715035A
Authority: US
Inventors: Hanns Eilenberg
Original assignee: Leybold Heraeus Verwaltung GmbH
Current assignee: Leybold Heraeus Verwaltung GmbH
Priority date: 1967-03-21
Filing date: 1968-03-21
Publication date: 1970-09-22
Anticipated expiration: 1987-09-22
Also published as: FR1557391A; CH459071A; NL6803879A; GB1221833A; NL152974B; BE712397A

Description

Sept 22, 1970 y Y H. EILENBERG 3,529,362

INSERT FOR FREEZE-'DRYING APPARATUS Filed March 21, 1968 F/gl 2F 2 l EVACUUM PUMP INVENTOR Hanns Ellenberg ATTORNEYS United States Patent man Filed Mar. 21, 1968, Ser. No. 715,035 Claims priority, applicatitsni (germany, Mar. 21, 1967,

6 Int. c1. Fzsb i3/30, 25/18 U.S. Cl. 34--237 7 Claims ABSTRACT OF THE DISCLOSURE In a container for use in bulk material freeze-drying apparatus, a supporting means having a wedge-shaped cross section is provided for supporting the material to be dried. The supporting means is Water-vapor-permeable and extends along the length of the container, thereby forming a channel for drawing off water vapor from the material being dried. The supporting means is so positioned in the container that the narrower end of its wedge-shaped cross section lies along the bottom of the container and the wider end reaches at least to the top of the surface of the material being dried. By this construction water vapor can easily and advantageously be extracted from the material being dried.

BACKGROUND OF THE INVENTION The present invention relates to a container for use in freeze-drying apparatus and more particularly for the drying of bulk materials.

' In containers used for freeze-drying processes, it is important to provide means for drawing off water vapor from the material being dried so as to facilitate the drying process. Such means have heretofore been provided but have proven relatively ineffective, particularly in cases where thick layers of material are involved. In such cases, the freeze-drying operation is made diicult by the lack of sutiicient exposed surface of the material being dried. It is highly desirable to have as much of the surface of the material being dried exposed as possible in order to facilitate the drying process. Applicant makes use of this principle by providing means in the freeze-drying container which define channels or vents through the material being dried. By so doing, drying conditions are greatly enhanced. Moreover, water vapor released from the material being dried can more easily be drawn off by means of such vents, particularly where fine-grained bulk materials are concerned. Thus the freeze-drying process as a whole is considerably improved.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide an improved, relatively simple and yet more effective means for facilitating the drying of bulk materials in a freezedrying container.

It is also an object of this invention to provide a better means for drawing water vapor olf from bulk materials being dried in a freeze-drying process.

In brief, the present invention proposes to provide a support means having an element which extends along the length of a container used n freeze-drying operations. The support means element is water-vapor-perrneable and serves as a venting element for Water vapor drawn from the drying material. More particularly, the venting element has a wedge-shaped cross section and is so disposed in the container that the narrower end portion of the wedge-shaped cross section rests on the bottom of the container and the wider portion of the Wedge-shaped cross section extends vertically at least to the level of the 3,529,362 Patented Sept. 22, 1970 ICC upper surface of the material to be dried. By thus positioning the venting member within the material to be dried, openings in the venting element can advantageously be placed at that level where the ice-cotaining core of the material being dried is disposed during the freezedrying operation. Moreover, the wedge-shaped configuration of the venting element advantageously provides a means for reaching water vapors trapped in the upper reaches (with reference to the bottom or base of the container) of the material being dried. The sloping sides of the venting element facilitate the collecting of water from the relatively thick material at the bottom of the container. Thus, the venting element, in elfect, provides a means or channel by which water vapor is drawn from the material being dried. The angle between the sides of the Wedge-shaped venting member can be relatively narrow so that the volume, hence the load capacity, of the container is not unnecessarily reduced.

In another form of the present invention, the venting element is a good heat conductor and is in heat-conducting contact with the bottom and/ or wall surfaces of the container. In addition to drawing water vapor from the material being dried, heat can be transferred to the material to facilitate the drying operation. In such an arrangement, the venting element is formed as a perforated or sievelike material with good heat-conducting property. The use of suitable sintered, screened or sponge-like materials is, however, also possible. The particular material used would depend on the ability of such material to draw off water vapor extracted from the material being dried equally as well as perforated or sieve-like materials.

In yet another form of the present invention, the venting element is constructed as a separable element so that it may be removed as a unit from the container, as desired. lIt has also been found advantageaus to provide partitioned portions within the container and a venting element within each portion; venting elements in adjacent partitioned portions being`connected to one another.

BRIIEAF lDESCRIPTION OF THE lDRAWINGS FIG. l is a longitudinal sectional View taken generally along the plane dened by line 1-1 of FIG. 2, showing a container having a venting element according to the present invention.

FIG. 2 is a cross-sectional view of the container taken generally along the plane defined by reference line 2 2. of FIG. l and arranged within a schematically shown environmental control device.

FIG. 3 is a schematic and perspective view of the container having a venting member according to the invention as shown in FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring rst to FIG. 1, a longitudinal section of a generally rectangularly shaped container 1 is shown therein. The container 1 includes partition members 3 and, in addition, venting elements 2. Both members 3 and elements 2 serve as supporting means for any bulk materials introduced into the container 1 for freeze-drying. The venting elements 2 include perforations 7, as shown also in FIG. 3, for drawing off water vapor from the material being dried.

Referring now to FIG. 2, as shown therein, the venting elements 2 are centrally disposed with respect to the space between partition members 3 within the container 1. The venting elements 2 are wedge-shaped in cross section and include a narrow end 4 and a wider end 5. The narrow end 4 of the venting element 2 can be formed such that it covers the bottom of the container. The container may be arranged in a conventional environmental control device as shown schematically in FIG. 2. This device basically includes a vacuum chamber having an outlet to a vacuum pump, and a radiant heating element arranged within the chamber.

The venting elements 2 are so arranged that the narrower end 4 of each element 2, respectively, is at the bottom of the container 1. The wider end 5 of each venting element 2 is, correspondingly, vertically disposed with respect to the bottom of the container so that it extends above the top surface of the material in the container being freeze-dried.

Referred to FIG. 3, the venting elements 2, as shown therein, are connected to each other by spacers 6. The venting elements 2 are removably assembled to the container 1. The spacers 6 are used to hold the venting elements 2 in position when the material to be dried is poured into container 1. These spacers 6 are located under hocks which are cut out of the elements 2 in such a manner that the whole venting assembly is under spring load.

As previously discussed, venting element 2 is watervapor-permeable, being formed of a sieve-like or perforated material. It is also conceivable, however, that element 2 can be formed from sintered, screened or sponge-like materials provided such materials, as are used, are as effective as the preferred sieve-like or perforated materials. Another desirable characteristic of the element 2 is that it have good heat-conducting properties. Venting element 2 is positioned in container 1 in good heat-conducting contact with the bottom and/or side Walls thereof, so that, in addition to drawing water vapor from the material being dried, heat can be transferred to the material during the process to facilitate drying.

It Will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

I claim:

1. In a vessel for freeze-drying apparatus used for drying relatively fine-grained bulk materials, having provided along an inner surface thereof a water vapor venting channel, the improvement wherein said vessel comprises:

(a) a container;

(b) supporting means inserted in said container for supporting the materials to be dried;

(c) said supporting means having at least one watervapor-permeable venting element;

(d) said venting element having a wedge-shaped cross section and extending along the entire long dimension of the inner surface of said container;

(e) said venting element having the narrower end of said wedge-shaped cross section in contact with and extending along the bottom of said container;

(f) the wider end of said wedge-shaped cross section being at least at the upper surface of such material to be dried, thereby forming a channel in such material to be dried from whence water vapor may be extracted from the material during drying; and

(g) said container being open to the top with said upper wider end of said Wedge-shaped cross section being spaced from other inner surfaces of said container whereby material to be freeze dried may be inserted from the top of the container, and water vapor may be vented from said material to the top of the container as well as through said venting element.

2. A vessel as dened in claim 1 wherein said venting element is further defined as being a sieve-like member.

3. A vessel as dened in claim 2 wherein said venting element is formed of a good heat conductor and is in heatconducting contact With the bottom and/or side surfaces of said container.

4. A vessel as defined in claim 3 wherein said venting element is separably assembled to said vessel in consequence of which said venting element is removable therefrom as a structural unit.

5. A vessel as deiined in claim 1 wherein said supporting means further comprise:

(a) a plurality of wall members longitudinally extending in said vessel and forming partitioned portions therein;

(b) at least one of said venting elements being disposed in each of said partitoned portions; and

(c) means connecting said venting element in adjacent partitioned portions to each other.

6. Apparatus for freeze drying relatively fine-grained bulk materials, having provided along an inner surface thereof a water vapor venting channel, the improvement wherein said apparatus comprises:

(a) a container;

(e) said venting element having the narrower end of said wedge-shaped cross section in contact with and extending along vthe bottom of said container;

(f) the wider end of said wedge-shaped cross section being at least at the upper surface of such material to be dried, thereby forming a channel in such material to be dried from whence vapor may be extracted from the material during drying; and

(g) means for subjecting a frozen material within said container to a sub-atmospheric pressure and a temperature such that frozen liquids within the material are sublimated to a vapor which may be removed via said venting element.

7. A method of freezing a relatively fine-grained bulk material comprising, in combination:

(a) placing a frozen line-grained material within a container having a venting channel formed along one of its sides, which venting channel includes a pair of inclined walls which are in contact with the bottom of said container, and which are closely spaced from each other by a greater distance at the top of the container, said walls being vapor permeable and said venting element being open to the top for the passage of vapor therein,

(b) subjecting the material to a subatmospheric pressure at a temperature at which at least some of the components of said frozen material sublimate to form a vapor, and

(c) withdrawing said vapor through said wedge-shaped channel.

References Cited UNITED STATES PATENTS 1,149,548 8/1915 Rand 34-238 XR 1,349,458 8/1920 Johnson 34-238 3,401,468 9/1968 Eilenberg 34-237 FOREIGN PATENTS 1,135,831 8/1962 Germany.

FREDERICK L. MATTESON, JR., Primary Examiner H. B. RAMEY, Assistant Examiner