US3289879A - Desiccators - Google Patents

Description

Dec. 6, 196 6 c, H WILLIAMS 3,289,879

DESICCATORS Filed Jan. 26, 1965 3,289,879 DESICCATGRS Claude Hubert Williams, Chalfont St. Peter, England, assignor to Jencons (Scientific) Limited, Hertfordshire, England, a British company Filed Jan. 26, 1965, Ser. No. 428,145 Claims priority, application Great Britain, Jan. 27, 1964, 3,362/ 64 1 Claim. (Cl. 220-46) This invention relates to desiccators which are particularly, although not exclusively, used for drying materials nnder vacuum in laboratories.

The conventional desiccator consists of a deep round bowl, often frusto-conical in shape, having a broad flange formed around the upper part, the flange having a finely ground plane upper surface. The cover consists of a deeply domed, roughly hemi-spherical, part having a similar broad flange formed around its base to mate with the flange on the bowl. The flange of the cover is also carefully ground on its under side to a plane surface. In use the bowl is charged with the material or objects to be dried and the cover is then placed on the bowl so that the two plane flange surfaces are in contact, a layer of grease being placed between the two surfaces. There is a vacuum connection at the top of the cover and when a vacuum is applied the external atmospheric pressure forces the two flanges into firm contact to provide, with the aid of the film of grease, a vacuum-tight joint.

This conventional type of desiccator has numerous disadvantages. Firstly, it is necessary to produce the finely ground plane surfaces on the two flanges and this is a comparatively slow and costly operation. Furthermore, the ground surfaces have to be carefully protected from chipping or other damage which can impair the vacuum seal. If the desiccator has been under vacuum for a considerable time the cover may be very difficult to remove because the two plane surfaces are in such tight and intimate contact, and if an attempt is made to introduce a tool between the surfaces to prise them apart damage may very easily occur. The broad, projecting flanges are, of course, easily subject to damage, for example, by having pieces broken out of them while in store or while being loaded or unloaded.

When loading the desiccator it is, of course, essential to ensure that no particles of grit or other foreign matter are picked up by the greased flange surfaces and extremely careful handling is, therefore, necessary.

The principal object of the invention is to avoid these difficulties by eliminating the ground flanges on the desiccator bowl and its cover.

According to the invention, a desiccator comprises a bowl and a cover having corresponding annular joint surfaces, one of the surfaces being provided with a circular' groove and the other being provided around its outer periphery with a shallow projecting stepped portion, and a ring seal, such as an O-ring, in the groove.

Preferably the groove is tapered so that the mouth is wider than the bottom thereof.

The bowl of the desiccator may also be provided with a substantially semi-circular groove around its outer periphery, in which a second resilient ring is disposed, to protect the desiccator from damage due to striking other hard objects.

In order that the invention may be clearly understood and readily put to practical use, one embodiment there- United States Patent "ice of will now be described, by way of example, with reference to the single figure of the accompany drawing.

Referring to the drawing, which shows only a part of a desiccator with the upper portion of the bowl and the lower portion of the cover in section, the bowl has a wall 11 which is considerably thickened at the upper portion 12. The thickened wall portion 12 has a fiat upper annular surface 13, and contained in the upper surface 13 is a groove 14 which is of tapered form, that is to say, the mouth of the groove is wider than the bottom thereof. Seated in this groove is a ring seal or O-ring 15 which is preferably of such cross-sectional diameter that when placed in the groove 14 it seats itself in the mouth of the groove and cannot settle in the bottom thereof.

The cover of the desiccator, which may be of the usual deeply domed shape with a vacuum connection at its top, has a wall 16 of appropriate thickness and a thickened portion 17 around its opening, the wall portion 17 terminating in an annular lower face 18 which is provided around its periphery with a shallow projecting stepped portion 19.

As shown in the drawing, the bowl and the cover are slightly separated, but it will be evident that when the cover is pressed down on to the bowl, and more especially when vacuum is subsequently applied, the cover will descend on to the bowl until the outer surface of the stepped portion 19 is in contact with the upper surface 13 of the bowl, and as the bowl is pressed into position the seal 15 is forced more deeply into the groove 14. At the same time, the upper portion of the ring seal 15 is flattened to conform to the surface 18. Thus the seal, when compressed, will have three flattened portions formed around it, two of them mating with the walls of the groove 14 and the third conforming to the surface 18. This provides an extremely effective vacuum seal which remains completely vacuum tight for long periods. On the other hand, as soon as the vacuum is released, the natural resilience of the seal 15 tends to push the cover upwardly and, in any case, since the upper surface 13 and the outer surface of the step 19 are not greased, it is a very easy matter to separate the cover from the bowl. The necessity to force the cover away from the bowl is entirely avoided so that objects or powders contained in the desiccator bowl are not rattled about or upset in the process.

In addition it should be noted that the provision of the stepped portion 19 ensures that the cover, when in contact with the surface 13 of the bowl, flattens the O evenly, and overcomes any tendency of the cover to compress the O ring unevenly if the latter was softer in certain parts.

Further advantages derived from the invention are that, since there are no greased surfaces, the possibility of picking up grit or other foreign matter on the sealing surfaces is virtually eliminated, and that the sealing ring itself may easily be replaced from time to time.

As a further protection for the desiccator, either when in store with other glassware or with hard metal apparatus, or when in use on the laboratory bench, it is protected against accidental damage by the provision of a further resilient ring 20, held in a part-circular peripheral groove. The ring 20 may conveniently be a ring seal similar to the seal 15 but of a larger size. A further ring similar to the ring 20 may also be provided in the cover, or if desired in both bowl and cover.

I claim:

A desiccator to be evacuated of air comprising a bowl and a cover having cooperiing annular flanges, one of References Cited by the Examiner ifii ifiii rii ii er iii iiil i iiiiiiii gfii gie irl UNITED STATES PATENTS said groove and projecting above the surface of said 1759176 5/1930 Voorhees 2151OO'5 flange, the other flange being provided around its outer 5 2751123 6/1956 KPhles et a1 220 550 periphery with a projecting stepped portion for abutting with the surface of said one flange when said desiccator is evacuated, said stepped portion being of such a height as to limit the deformation of said O-ring whereby said THERON CONDON Prlmary Exammer' O-ring is evenly compressed between said other flange and 10 LOUIS MANCENE, JAMES MARBERT,

said tapered Walls to form an airtight seal. xami e s.

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