Heat exchange – Heating and cooling – Heating and cooling of the same material
Patent
1989-04-14
1991-12-10
Wayner, William E.
Heat exchange
Heating and cooling
Heating and cooling of the same material
62 492, 62320, 839155, F25C 502, F25B 2900
Patent
active
050709356
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a cooling chamber cooled by liquid nitrogen (LN.sub.2) and swept with gaseous nitrogen (GN.sub.2) and intended for producing thin, particularly ultra-thin, sections for microscopic and electron microscopic examination.
According to the current state of the art, LN.sub.2 cooled and GN.sub.2 swept or GN.sub.2 filled cooling chambers are preferably used in the field of cryo-ultramicrotomy for electron microscope examination of viscoplastic anti-adhesive or biomedical objects, instead of the previously used cooling cartridges or cryostat systems (cf. H. SITTE, Instrumentation for Cryosectioning, in: "Electron Microscopy 1982, Vol. 1, 10th Int. Congress on Electron Microscopy, Hamburg, pp. 9 to 18; H. SITTE and K. NEUMANN, Ultramicrotomes and appliances for ultramicrotomy, Geratetechnik--Funktion--Zubehor, in: G. SCHIMMEL and W. VOGELL: A collection of methods for electron microscopy, contribution 1.1.2, Wiss. Verl. GmbH, Stuttgart 11, 1984, 1 to 248, particularly pp. 69 to 91; C. REICHERT AG, A-1170Vienna. Catalogue 1.K.-FC 4 D-D 4/84, FC 4 D Low Temperature Cutting System according to SITTE, 1984; C. REICHERT AG, A-1170 Vienna, Catalogue 1.K.-CRYO PREP. E-8/86, Cry preparation for superior EM investigation, 1986). With the currently preferred FC 4 D system of REICHERT AG in A-1170 Vienna, a cutting space in which a frozen object and a knife are located is an open topped sheet aluminum box which is directly cooled by LN.sub.2. For this purpose, having regard to the available space with an ultramicrotome, there are on the right and left two intercommunicating sheet aluminum tanks ("a twin tank system") to accommodate about 1 liter of LN.sub.2 and these are connected to the cutting chamber. This arrangement (twin tanks with cutting chamber) makes it possible to achieve minimal temperatures which come very close to the boiling point of LN.sub.2 (-196.degree. C.), and also make it possible to work with an open cutting room ("open top work") without the risk of ice deposits in the object knife area. This situation owes much to a strong GN.sub.2 current which is constantly being vaporized from the LN.sub.2 which is used as the cryogenic medium and which is partially deflected by baffle plates to the bottom of the cutting chamber. In this way, the cutting chamber is swept from the bottom upwards by a stream of cold, dry GN.sub.2 which on the one hand cools the object and the knife and also supports therefor, while on the other it prevents the ingress of humid room air into the cutting chamber. Since with regard to the heat and cold sensitivity of the ultramicrotome mechanism, it is also necessary to avoid frost deposits as well as cold surfaces on the outside of the tank system, the system described is enclosed by an insulating layer of foamed synthetic plastic (e.g. foamed polystyrene or polyurethane) and finally a chamber wall which is thermostatically heated to room temperature and which consists of a readily heat conductive material (e.g. cast aluminum) (see inter alia H. SITTE, K. NEUMANN, H. KLEBER and H. HASSIG, Cooling Chamber for Holding Objects Requiring Work, Particularly Biological Objects, German Patent Application No. 29 06 153 C 2 of Feb. 17, 1979). Such a chamber wall not only prevents frost forming, which cannot be avoided after prolonged use even with a relatively thick layer of insulation, but at the same time it warms the GN.sub.2 flowing over the outside walls up to temperature levels which no longer have a disturbing influence on the sensitive ultramicrotome mechanism. The chamber wall is, via a resilient interlining, fixed on an assembly element (e.g. a dovetail joint), by means of which it can be mounted on the knife support of the microtome or ultramicrotome. The assembly element carries a baseplate for the cutter holder in a rigid metallic connection. In contrast, the object is now generally fixed on a bridge-like carrier element which is mounted on a preparation carrying arm of the microtome or ultramicrotome and plunges down into the cu
REFERENCES:
patent: 4284894 (1981-08-01), Sitte et al.
patent: 4489569 (1984-12-01), Sitte
Hassig Helmut
Neumann Klaus
Sitte Hellmuth
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