US 2496054 A
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Jam 3L H0 c. N. HOYLER EWM BELL JAR VACUUM EVAPORATOR Filed July 27, 1945 ATTORNEY.
Patented Jan. 31," 1950 BELL-JAR VACUUM EvAroRA'roR Cyril N. Hoyler, Princeton, N. J., assgnor to Radio Corporation of America, a corporation of Delai Ware Application July 27, 1945, Serial No. 607,410
This invention relates to vacuum apparatus for the treatment of materials, and particularly to improvements in evaporators.
In the dehydration or concentration by evapo ration of certain materials, notably biological and pharmaceutical products, it is usually necessary or desirable to maintain the dome or cover of the evaporator at an elevated temperature in order to prevent the vaporous emanations of thel uid from condensing and. dropping back into the batch or onto the base or hot plate of the evaporator. To this end, it has been previously proposed to provide an auxiliary device such, forexample, as an externally mounted infra-red lamp, for heating the hood or other surface of the evaporator upon which the undesired condensation is likely to occur. Obviously, such auxiliary equipment adds to the cost and complicates the operation of the evaporator. Furthermore, the radiant heat supplied by the auxiliary heater may afect the comfort of the operator and the life of the rubber or other gasket employed in forming the air-tight seal about the hood or cover.
Accordingly, the principal object of the present invention is to obviate the foregoing objections to present day vacuum apparatus and, more specifically, to provide an improved dehydrator or evaporator wherein condensation is prevented without the use of any auxiliary heating equipment.
The foregoing and other objects are achieved in accordance with the invention by the provision of an external gasket or seal of novel construction and which permits the removable hood or other closure element of the evaporator to be mounted in direct heat transfer relation with the heated inner surface or base upon which the material to be treated is mounted.
Certain preferred details of construction together with other objects and advantages will be apparent and the invention itself will be best understood upon reference to the following speciiication and to the accompanying drawing where- Figure l is an elevational view, partly in section, of an evacuable chamber incorporating the invention, and
Figure 2 is a plan view, with the cover removed, of the device of Fig. l.
In the embodiment of the invention which has been selected for illustration, l designates, generally, an evacuable chamber comprising a heated metal platform or base 3 and a closure element or cover which, in the instant case, is in the form of a removable metal bel1-jar or hood. 5. Any
4 Claims. (Cl. 159-29) suitable means, such, for example, as an electrical resistance unit 'l which may be mounted on or in the base 3 is provided for heating the chamber l and hence the material to be treated therein. Where the material to be dehydrated comprises a drug in dosage quantities, the drug ampoules 9 may be contained in rack i I which is simply laid on the heated inner surface 3a of the base. The space within the chamber I is evacuated through a port I3 in the metal-base 3 and is connected to a suitable vacuum pump :grot shown) through a water cooled condenser Since the hood or cover 5 presents a relatively large surface to the ambient it is apparent that, unless the cover is heated, the vapors which emanate from the material being treated may condense upon its inner surface and drop back into the ampoules 9 or onto the heated innersurface of the base 3. As previously indicated, in order to prevent such undesired condensation, the present invention dictates the heating of the cover 5 with energy supplied by conduction from the heated base 3. Such a direct connection is made practical by the provision of a gasket-seal of novel construction arranged preferably on the exterior of the evacuable chamber I adjacent to and surrounding the said direct heat-exchange connection.
In carrying the invention into eiect the diameter of the base 3 is made substantially larger than the diameter of the hood or cover 5 and is preferably provided with a circumferential rim 3b so that there is a circular channel or groove 3c between the cover 5 and the rim 3b when the cover is closed. An endless piece of rubber or similar iexible pneumatic tubing l'i is preferably cemented as indicated at ila in the groove or channel 3c adjacent to the rim 3b. A circular projection i9 on the outer surface of the hood 5 is arranged preferably somewhat below the level of the rim 3c. Thus when the hood is brought down over the base 3 the circular projection i9 merely rests upon the flexible member l1 without collapsing it. However when the chamber I is put on the pump the pressure of the atmosphere upon the hood is transmitted through the projection lil to the gasket Il which is thereby partially collapsed or distorted and forms a vacuum tight seal about the said chamber. The pressure of the atmosphere on the hood 5 is carried by the base when the tubing l'! is collapsed sufliciently to cause the hood to become seated on the base in order to establish the desired direct heat conductive connection between the base and the hood 5. Since the weight of the hood 5 and the pressure of the atmosphere thereon is borne principally by the metal base 3, and not by the gasket alone, the yieldable member l'l may be used repeatedly without impairing its usefulness.
It will now be apparent that the present invention provides an improved evaporator and one wherein condensation of the vapors is prevented without the use of any expensive or troublesome auxiliary equipment.
What is claimed is:
1. Apparatus for the dehydration of materials comprising a base provided with an inner surface, means for heating said surface, a closure element having an inner surface normally exposed to the vapors from said material and upon which said vapors may condense in the absence of heat, said closure element being adapted to be moved into direct heat exchange relation with said heated surface whereby to heat said closure element and thereby prevent the condensation of said vapors thereon, a compressible gasket containing entrapped air supported exterior of the periphery of said closure element, and means on said closure element responsive to said movement of said closure element for applying a compression force to said gasket whereby to establish an air-tight seal about said surfaces.
2. The invention as set forth in claim 1 and wherein means are provided for evacuating said casing whereby said downward movement of said closure element and the formation of said airtight seal between said heated surface and said closure element results from the operation of said casing-evacuating means.
3. Apparatus for the dehydration 0f materials comprising a heatable base, means to heat said base, a removable hood having a lower open-end adapted to be seated on said base and having an inner surface normally exposed to hot vapors from said material and upon which said hot vapors may condense when said hood is cold, a projection on the outer surface of said hood adjacent to its said lower end, a pneumatic tube on said base about the outer periphery of said hood and upon which said projection is adapted to rest to (normally support said hood out of contact with the base, and means for evacuating air and moisture from the interior of the apparatus whereby atmospheric pressure upon said hood will cause it to move downwardly into direct heat transfer relationship with the base and cause said projection to compress said tube to form an air-tight seal between the hood and base.
4. Apparatus for the treatment of materials comprising a base, means for heating said base, a removable hood constituted of heat conductive material and having an open end adapted to be mounted upon said base with the edge of the hood in direct heat exchange relation with said base, a pneumatic tube on said base adjacent to the outer periphery of said hood, and a projection on the outer surface 0f said hood for engaging and compressing said pneumatic tube when said hood is mounted upon said base.
CYRIL N. HOYLER.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 499,486 Walter June 13, 1893 2,263,008 McRae Nov. 18, 1941 2,271,239 Vokes Jan. 27, 1942 2,302,253 Reichel et al Nov. 17, 19412 2,338,234 Dimmick Jan. 4, 1944 FOREIGN PATENTS Number Country Date 40,532 Australia Jan. 10, 1910