US2494541A - Vacuum drier with automatic capping device - Google Patents

Description

Jan. 17, 1950 H. K. BURR ET AL VACUUM DRIER WITH AUTOMATIC CAPPING DEVICE 2 Sheets-Sheet 1 Filed March 19, 1948 3mm H. K.BURR

B. MAKOWER 1 gm ATTORNEYS Jan. 17, 1950 BURR ET AL 2,494,541

VACUUM DRIER WITH AUTOMATIC CAPPING DEVICE Filed March 19, 1948 2 Sheets-Sheet 2 iv 25 30 3 L L5 2 H..K.BURR B MAKOWER X W. W

ATTORNEYS Patented Jan. 17, 1950 VACUUM DRIER WITH AUTOMATIC CAPPING DEVICE Horace K. Burr, San Pablo, and Benjamin Makower, Berkeley, Calif., assignors to the United States of America as represented by the Scoretary of Agriculture Application March 19, 1948, Serial No. 15,946

(Granted under the act of 'March 3, 1883. as amended April 30, 1928; 370 0. G. 757) Claims.

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described and claimed if patented in any country, may be manufactured and used by or.for the Government of the United States of America throughout the world for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a vacuum drying apparatus. It particularly relates to a vacuum drier employed in laboratories to desiccate heatsensitive substances that readily re-hydrate if exposed to the atmosphere.

In our apparatus, the samples to be dried are placed in closed vials which are inserted in the drier. When the vacuum is applied, the caps of the vials are automatically raised to expose the contents thereof to the rarified atmosphere; Moreover, when the desiccation is complete and the vacuum broken, the vials are automatically re-capped. Thus when they are removed from the drier, there is no danger of re-hydration due to absorption of the moisture in the air.

An object of this invention is to provide a novel vacuum drier having an automatic capping means.

Further objects and advantages will be obvious to those skilled in the art from the disclosure herein.

The drawing accompanying this specification illustrates apparatus in accordance with this invention.

Fig. 1 represents a longitudinal sectionof the drier.

Fig. 2 represents a plan view of the drier.

Fig. 3 represents an enlarged longitudinal section of a portion of the drier.

The apparatus and its functions are described as follows:

Base 2, preferably made of thermally insulating material, is a fiat, bored disc. On base 2 is electrical heating device 3, having wires 4 and 5 for. connection with a suitable source of electricity.

A copper metal plate 6 is positioned over heating device 3 and serves to transfer heat uniformly from the heating element to the interior of the drier. On plate 6 is a ring gasket l8 which supports glass bell jar l. The latter is preferably coated with aluminum or other metal so as to minimize loss of heat by radiation. If the bell jar is so coated, a window may be left free, to be used for observation of the contents of the drier.

Plate 6 is provided with a pipe, conduit or tube ll that connects with the interior of the drier.

This tube is ordinarily connected with a suitable source of vacuum.

An air drier may be placed in the pipe leading to the vacuum pump, so that, upon releasing the vacuum, dry air will be supplied to the desiccator.

On the upper surface of plate 6 is a metal plate 30 which is fitted with rings 25 which serve to receive and position vials 24. For supporting the vial caps there is provided a plate 29. This plate is provided with holes 28 and seats 21 adapted to receive and position vial caps 23. Plate 29 is prevented from turning by holes 2|, 22 into which fit pins i9 and 2B. These pins I9, 20 are attached to plate 30. The loose fit of these pins in the holes permits vertical movement of the plate. Plate 29 is adjustably fastened to bolt 1 by nuts 8 and 9. Bolt l passes through bore casing 28 and through collar 16. Collar I6 is fastened to plate which in turn is attached to bore casing 28. The fit of bolt l in collar is is sufiiciently loose so that the bolt can move in a vertical direction. Adjustably attached to bolt 1 by nuts [0 and H is bellows it. The seal between bellows l3 and bolt i must be vacuum tight. This bellows is preferably made of thin gauge metal or other flexible material.

Plate it is provided with port [5, to permit'free movement of air in and out of the bellows.

Since the drier is intended to be operated at pressures considerably lower than atmospheric, the apparatus must be properly constructed to prevent leaks. To this end, plate 6 must be tightly joined to bore casing 28, as by soldering or brazing to prevent leakage. Likewise plate it must be joinedto the bore casing 28 in such manner as to provide a vacuum-tight seal. This same precaution applies to the attachment of the lower 1 end of bellows 13 to plate ll, to the attachment of the upper end of bellows l3 to bolt 1, and to the attachment of pipe ll to plate 6.

The operation of the device is as follows:

Bell jar I is removed from the drier. Samples of material to be dried in vials 24, closed by caps 23, are inserted into rings 25 through holes 26. With the device open to the atmosphere, plate 29 is close to plate 30 whereby caps 23 remain in position to seal the contents of vials 24. When the operator is ready to start the drying operation, he places bell jar I over the surface of plate 5 and seats it on gasket l8. Pipe I1 is then connected to a source of vacuum such as a vacuum pump. If it is desired to hasten the drying by application of heat, wires 4 and 5 are connected to a suitable source of electricity. For control of temperature, heating element 3 may be equipped with an automatic thermostat to maintain the temperature at desired level. As

in it: Atmospheric air exerts. a diflerential of pressure through bore casing '28, port l and against the inner face of bellows it. This differential pressure causes expansion of bellows it which in turn forces bolt 1 upwardly thus lifting -ference in pressure between the chamber and the outer atmosphere to automatically raise the plate 29. Bolt 1 is equipped with a nut i2 which is capable of adjustment and which serves as a stop to limit the motion of bolt 1. After thedrying process is complete, dry air or other gas is admitted through tube I! to break the vacuum and to activate the automatic capping feature. As soon as the pressure inside bell jar i approaches atmospheric. pressure, bellows l2 con-I tracts to its normal size, lowering plate 28 and thus capping each ofthe vials 24. -The bell jar i can then be removed by the operator and the vials weighed or .otherwise treated without dangel of absorption ,of moisture from the atmosphere.

Fig. 3 represents an enlarged longitudinal section of a portion of the drier. This figure illustrates the position'of plate 29 and cap 23 when in raised position as caused by vacuum within bell jar I.

The device is capable of modification to widen its field of utility. Thus bolt"! may be lowered manually by conventional means such as an arm attached to bolt I and extending outside the vacuum chamber. Plate 29 may thereby be lowered to cap vials 24 before breaking the vacuum in the vessel. Caps 23 and vials 24 may be provided with flanges forming a seal tight to vacuum. In this manner the material in vials 24 may be removed from the drier and preserved without permitting contact with air or other gases. Such devices and mode of operation are well known in the art; being disclosed, for example, in Barr Patent 2,353,985, issued July 18, 1944.

Vials 24 are provided with an outer tapered surface at the upper end, at 24', to assist in providing a good seal-and to keep the caps 22 in place.

Having thus'described our invention, we claim:

1. A vacuum desiccator providing a desiccating chamber, means within the chamber for positioning a container for material to be desiccated, plate means within the chamber for supporting, raising and lowering a closure for said container, a conduit communicating with said chamber for application of vacuum, means responsive to difplate upon application of vacuum to said chamher, and to automatically permit said plate to lower when the vacuum is released.

2. The apparatus described in claim 1 in which the pressure responsive means comprises 9. diaphragm having one face exposed to the outer atmosphere and the opposite face exposed to the pressure within the chamber.

3. A vacuum desiccator comprising a base, a heater, and a cover providing a desiccating chamber, means mounted above the heater to position a container for material to be dried, means for raising and lowering a closure for said container comprising a plate having an opening to receive the upper open end of the container, a vertically movable bolt supporting said plate, a pressure response diaphragm attached at its center to said bolt, the diaphragm having its lower face exposedto atmospheric pressure and its upper face exposed to the pressure within the chamber. aconduit'communicating with said chamber for application of vacuum '4. A vacuum desiccator comprising a base, a cover providing a desiccating chamber, means for positioning a number of containers for material to be desiccated within the chamber, means for raising and lowering closure caps for said containers comprising a perforated plate having means adjacent each perforation to position a closure cap, aconduit communicating with said chamber for application of vacuum, means responsive to difierence in pressure between the chamber and the outer atmosphere to raise the perforated plate upon application of vacuum to REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'EN'IS Number Name Date 982,860 Peelle Jan. 31, 1911 2,315,865 McBean Apr. 6, 1943 2,353,985 Barr July 18, 1944

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