US2091182A - Apparatus for degreasing metal and like nonabsorbent articles by means of volatile solvents - Google Patents

Description

Aug. 24, 19

APPARATUS FOR DEGREASING METAL AND LIKE NONABSORBEITT J. A.'M. w. MITCHELL 2,091,182

ARTICLES BY MEANS OF VOLATILE SOLVENTS Filed April 4, 1935 INVENTOR.

Joseph Arlhur NusgravE Wuudcnck Him-1211.

ATTORNEY Patented Aug. 24, 1937 UNITED STATES- APPARATUS FOR DEGREASING METAL AND LIKE NONABSORBENT ARTICLES BY MEANS OF VOLATILE SOLVENTS Joseph Arthur Musgrave Woodcock Mitchell,

Runcorn, England, assignorto Imperial Chemical Industries Limited, a corporation of Great Britain Application April 4, 1935, Serial No. 14,705

In Great Britain April 5, 1934 4 4 Claims.

This invention relates to an improved apparatus for degreasing metal and other non-.absorbent articles by means of the vapour of volatile grease solvents.

5 Numerous proposals have been made for the ing chamber with means at the bottom for vaporizing liquid solvent to maintain a supply of vapour within the chamber, and with cooling surfaces in the upper portion to condense the solvent and thereby to prevent the escape of vapour from the apparatus. Usually these cooling surfaces are coils arranged inside and round the walls of the upper part of the degreaser. Due to the density of the vapours generally used for this process, no diificulty is experienced in controlling the height of the vapour by this construction.

95 In operating a plant of this kind, the cold metal articles to be treated are lowered into the solvent vapour which immediately condenses upon the articles and exerts asolvent action on the film of oil and grease. The solution of oil drains from the articles and falls into the bottom of the plant to be revaporized while fresh solvent is continually condensing and assisting in the solution and the washing away of the oil. Except in cases of exceptionally heavy contamination, or very light articles of large surface area, this action continues until the metal articles are left free from grease and oil but are covered with a film of the liquid solvent. To prevent contamination of the atmosphere and to avoid unnecessary loss of the solvent, this film is allowed to evaporate from the treated articles inside the degreaser. This is usually rendered possible by providing extra height in the upper portion of the degreasing chamber above the cooling surfaces, and after the degreasing the articles wet with solvent are raised into this upper portion when the film rapidly evaporates from the materials which have become warm during the degreasing, and the vapour drops by reason of its density into the lower portion of the degreaser.

It has also been proposed to provide degreasing apparatus used for this process with a set of coils which are actually in, or may readily be put in communication with the bottom portion of the degreasing chamber, and at-the conclusion of the degreasing operation to flow cooling water through these effecting condensation and thereby dropping the level of the vapour in the chamber. By this means the film of the solvent can evaporate from the degreased articles before they are removed from the chamber.

This method of operating is, however, time consuming and is also wasteful of solvent,,in that there are periodical surges out of the plant, of air fully saturated with solvent vapour.

It is an object of the present invention to provide an apparatus in which this waste may be to a great extent, if not completely obviated, and at the same time to dispense with the extra height of the plant necessary to accommodate the degreased articles during drying by the first mentioned method. 7

According to the present invention a degreasing apparatus of the type utilizing a controlled volume of solvent vapour is provided with two or more chambers adapted to contain a volume of solvent vapour, the said chambers being in communication at the top to allow a flow of gas or vapour from one to another, and fitted with means in the lower portion whereby the level of vapour in each chamber may be lowered or permitted to rise to'the normal level 'at the top of the chamber. Such means may be so interconnected that when the vapour level is being lowered in one chamber it is being allowed to rise in another.

The nature of the invention may be further 11- lustrated by the following description of one form of apparatus constructed in accordance therewith. This comprises a metal tank with cooling coils fitted round the upper portion of the walls to control the height of the solvent vapour and prevent its escape from the tank. A supply of solvent vapour is conveniently maintainedby boiling liquid solvent in the bottom of the tank. To provide the separate vapour degreasing chambers partitions are fitted in the tank extending below. the level of the boiling liquid solvent at the bottom and above the level of the solvent vapour, as determined by the cooling coils, at the top. By this means the vapour degreasing spaces are separated except at the top where the gas communication one with another may be provided for bya space left between the top of the partition and the top of the tank. In this construction the partitions should extend only a very short distance above the vapour level.- The means for lowering the vapour level in the separate chambers formed by the partition, is provided by coils arranged in the lower portion of each chamber above the level of the liquid solvent and fitted with a source of cooling water which can be admitted to the coils when it is desired to lower the vapour level and cut off when the level is to be raised. The coils must obviously be so arranged that a suitable space to permit the treatment of oods of the desired size is left between them and the communications atthe top of the chambers. It will also be apparent that the amount of cooling water passed through the coils must be sufficient to condense all the vapour being evolved from the solvent in the bottom of the chamber in question.

If desired, the cooling water may. be introduced through a three-Way cock, the delivery pipes of which are connected to adjacent chambers. this manner it is possible to ensure by one action the lowering of the vapour in one chamber during the rise of the vapour in the next chamber.

For supporting the goods to be degreased it is convenient to fit in each degreasing chamber a perforated plate above the coils at the bottom. The goods may either rest directly on this plate or may, in the case of a number of small pieces, be carried in a basket resting on the plate.

A simplified form of apparatus of the above type is illustrated diagrammatically in the accompanying drawing, Figure 1 being a section and Figure 2 a plan of the apparatus which may be constructed of any suitable metal such as galvanized steel plate.

In the drawing, I represents an outer casing provided with a bottom 2 and holding a volume of volatile liquid grease solvent 3. Two degreasing chambers 4 and 5 are formed by the partition 6 joining opposite walls of the casing I and extending below the surface of the liquid solvent 3 in the bottom of the casing. The partition may also be joined to the bottom 2 of the casing, but I find it preferable to leave an opening 1 below the liquor level to permit free movement of the liquid solvent between the bottom portions of each degreasing chamber. To maintain a supply of solvent vapour in the degreasing chambers, heating means are provided for the liquor in the bottom of the casing. In the present case the gas burners l4, l5 are used, although it will be obvious that any other suitably arranged source of heat could be used, e. g. electric heaters or steam coils. In the upper portion of each of the chambers are the condensing coils 8, 9, having suitable connections for the supply and escape of cooling water and arranged round the walls of each chamber at such a height that the level of the solvent vapour does not rise above the top of the partition 6 when the coils are in use. Between the top of the partition 6 andthe top of the casing l is space in permitting the free flow of gaseous fluid between the chambers 4 and 5, even when the apparatus is provided with a cover which is not shown in the drawing. In the lower part of each degreasing chamber the condensing coils II, 12 are fixed at a height slightly above the liquor level, and in accordance with the preferred form of the invention the cooling water is supplied to these coils through the three-way cock l3 which enables the lower condensing coils in the one chamber to be put out of use with the same action that brings the lower coils in the other chamber into action. At a short distance above the lower coils perforated plates l6 and l! areprovided on which to rest the goods being treated. Run-offcocks for liquid solvent and cleaning doors for the removal of solid matter- 75- and sludge from the bottom of the casing may also be provided but are not shown in the drawing.

In working the apparatus it is first charged with a volume. of volatile grease solvent, for example trichlorethylene, sufficient to seal the passage under the partition and to provide the requisite volume of solvent vapour to fill the degreasing chambers. Cooling water is turned on to the upper coils 8 and 9 and the supply to both' these sets of coils is maintained throughout the working period. The three-way cock I3 is turned on supplying cooling water to one set of the lower coils, say to the coils II in the chamber 4, and then the gas burners are lit. When the solvent in the bottom of the apparatus is boiling freely, the vapour rises in the chamber 5 to the level of the coils 9, while in chamber 4 its rise is stopped by the coils II. A charge of greasy material to be cleansed is now placed on the perforated plate l6 and the three-way cock l3 turned so that the supply of cooling water is cut off from the coils II and allowed to flow through the coils I2. This permits the gradual rise of solvent vapour in the chamber 4 up to the level of the coils 8, while in chamber 5 the solvent vapour drops until its level reaches the coils [2. The volume of air saturated with solvent vapour which originally occupied chamber 4 is thus displaced by the rise of the concentrated solvent vapour and largely passes over into chamher 5 to occupy the space previously filled with the solvent vapour.

When the solvent vapour rising in chamber 4 comes into contact with the cold charge of greasy material, it is condensed on the surface and the liquid thus formed dissolves the grease and flows off into the boiling liquid in the bottom to be revaporized for further use. Complete removal of the surface grease is thus effected in a very few minutes and while this is in progress in chamber 4 a fresh charge of greasy material is placed in chamber 5 as soon as the vapour level has dropped. When this has been done and dcgreasing has been completed in chamber 4, the cock I 3 is again turned to cut off the cooling water from the coils I2 and supply it to the coils II. This causes vapour to rise in chamber 5 and to drop in chamber 4 in which the freshly degreased warm goods quickly dry. They may then be removed and replaced by afresh charge of greasy material while degreasing is in progress in chamber 5. From this point the sequence of operations involving degreasing alternately in each chamber while goods are drying and being replaced in the other, is repeated until it becomes necessary to replace the liquid solvent by a fresh supply. This occurs when so much oil has been collected in the solvent solution that the boiling point is raised to an unduly high figure. When this occurs the oil solution is subjected to a. distillation process to recover clean solvent for re-use.

It will be observed that the above description and the attached drawing are illustrative of a very simple form of the invention. Considerable economies of solvent are, however, rendered possible by its use and the continuity of the operations enables a large output to be obtained from a single plant. At the same time it will be obvious that modifications and additions may be made by those-familiar with the art. For example, it mayibe found convenient to provide a cover for the degreasing chambers capable of covering any chamber in which degreasing is in progress and of being rapidly transferred from one chamber to another. There are also possible further economies to be brought about by partially or completely cutting off the vapour supply to the chamber in which the vapour level is being lowered, e. g. in the case of a plant in which the solvent is boiled by gas heaters the gas may be shut off or turned on at the same time that cooling water is turned on or shut oiT the lower condensing coils, and if desired, inter-locking taps may be provided to ensure this is done.

Also, it is obviously unnecessary that the apparatus should be confined to the provision of two degreasing chambers. Any number which are capable of being conveniently operated may be provided having regard to the incorporation of means whereby the vapour in one chamber is raised while it is simultaneously lowered in another. Provision may also be made for the supply of cooling water to be cut off from the upper condensing coils of a chamber at the same time that it is turned on to the lower coils in the same cham ber. Some further economy is thereby eiiected without departing from the invention.

I claim:

1. Apparatus for degreasing metal and other non-absorbent articles by means of the vapor of a volatile grease solvent comprising a plurality of compartments adapted to contain solvent vapor in which the articles, to be degreased may be 30 placed, means for supplying said compartments with solvent vapor, condenser means positioned in the lower portions of said compartments for in dividually controlling the level of solvent vapor in said compartments, and a communicating lower portions of said compartments for raising the solvent vapor level in one of said compartments and for simultaneously lowering the solvent vapor level in another of said compartments, and a communicating passageway between said compartments and near the upper portions thereof for flowing air from said one compartment to said other compartment.

3. Apparatus for degreasing metal and other non-absorbent articles by means of the vapor of volatile grease solvents which comprises a plurality of compartments adapted to contain solvent vapor, means for supplying said compartments with solvent vapor, condensers in the lower part of each of said compartments, means for supplying cooling fluid to said condensers, means for stopping the flow of cooling fluid to the condenser in one of said compartments when cooling fluid is supplied to the condenser in another of said compartments, and a passageway between said compartments and near the upper portions thereoffor flowing air from said one compartment to said other compartment.

.4. Apparatus for degreasing metal and other non-absorbent articles by means of the vapor of volatile grease solvents which comprises a plurality of compartments adapted to contain solvent vapor, means for supplying said compartments with solvent vapor, condensers in the upper portion of each compartment for maintaining an upper vapor level therein, condensers in the lower portion of each compartment for maintaining a lower vapor level therein, means for supplying cooling fluid and controlling the flow thereof to said condensers constructed and arranged to stop the supply of cooling fluid to the condenser 1 in the lower portion of one of said compartments when cooling fluid is admitted to the condenser in the lower portion of another of said compartments, and a communicating passageway between said compartments and near the upper portions thereof for flowing air from said one compartment to said other compartment.

JOSEPH ARTHUR MUSGRAVE WOODCOCK MITCHELL.

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