US2201729A - Degreasing metal and like nonabsorbent articles - Google Patents

Description

N. R. HOOD May 21, 1940.

DEGREASING METAL AND LIKE NONABSORBENT ARTICLES Filed Jan. 9, 1939 2 Sheets-Sheet l INVENTOR.

NORMAN ROY HOOD A TTORNEY.

N. R. HOOD May 21, 1940.

DEGREASING METAL AND LIKE NONABSORBENT ARTICLES Filed Jan. 9, 1939 2 Sheets-Sheet 2 INVENTOR.

NO RMAN ROY HOOD .&m

A TTORNEY.

Patented May 21, 1940 UNITED STATES z,z01,1 2a

PATENT OFFICE DEGREASING METAL AND LIKE NONABSORBENT ARTHLES Application January 9, 193i), Serial No. 249,885 In Great Britain January 12, 1938 3 Claims.

This invention relates to improvements in degreasing metal and like nonabsorbent articles by means of a volatile solvent.

Many proposals have been made for degreasing 5 metal and like nonabsorbent articles by treating them with a volatile solvent in vapour and/or liquid form, and such proposals have included treatments with jets of liquid. To purify such solvent it is usual to set up a circulation through various compartments, in which vaporization and recondensation of the solvent are included. Where jetting is employed a relatively large volume of solvent is required which cannot be kept free of suspended solids without a rate of circulation which is unnecessarily high so far as a liquor bath and vapour treatment are concerned. On the other hand, for satisfactory operation, it is essential to keep the amount of suspended solids in the liquid as low as possible since the main purpose of the jetting is to remove adherent solids. Further, where the jetting is interposed between a hot liquor treatment and a vapour treatment it is an advantage to be able to use cold liquor since the goods are thereby cooled and the subsequent vapor treatment rendered more effective.

It is an object of the present invention to provide a process for degreasing metal and like nonabsorbent articles in which the articles are subjected to jets of solid-free solvent. It is a further object of the invention to provide a process in which the jetting solvent is maintained free of suspended solids without the necessity of distilling it. It isa still further object of this invention to maintain the jetting solvent free from suspended solids without the necessity of having a high distillation rate in the vapour compartment. It is yet another object of my invention to provide apparatus for carrying out such processes. Further objects of the invention will appear hereinafter. These objects are accomplished by the following invention.

I have found that these objects can be achieved in a process for degreasing metal and like nonabsorbent articles with a. volatile grease solvent involving a jetting treatment as well as a vapour and if desired, a liquor bath treatment by supplying solvent to the jetting mechanism from a separate supply of solvent, returning at least a part of the solvent from the jetting compartment to that supply after subjecting it to cetrifugal action sufllciently intense to remove material in almost colloidal suspension therein, and returning 5 the remainder (if any) of the solvent from the jetting compartment to the said supply of solvent after distilling it.

Suitable apparatus for carrying out this step of the process comprises a stock tank for clean solvent, a second tank to receive solvent from 5 the jetting compartment, means for distilling part of the solvent in the second tank and for returning the distillate to the first tank, means whereby the remainder of the liquid in the second tank can be delivered to a centrifuge and thence to the first tank, and means for jetting liquid from that tank on to the goods being treated.

In one form of my invention in which goods are subjected to a jetting treatment between an immersion in liquid solvent and a vapour treatment, the apparatus comprises a compartment for hot liquid solvent and a compartment in which a solvent vapour zone can be set up, the two being joined above the liquor level and vapour level respectively by a tunnel-like enclosure sealed from direct communication with the atmosphere by bailles at either end dipping into the liquor and vapour compartments respectively, a carrier being provided for conveying articles through the apparatus. Solvent is arranged to overflow from the liquor compartment to the vaporizing compartment, condensate from which is returned to the former; a continuous circulation of solvent is thus set up between the two compartments. Sprays or jets in the tunnel-like enclosure are supplied with solvent from an external store tank, and a collecting device is provided in the lower part of the enclosure to receive solvent from the sprays and deliver it to a second store tank. The purification of jetting 35 solvent is accomplished in accordance with the invention by providing for solvent from the second tank to be returned to the first tank via a centrifuge and preferably a still is also provided to which part of the jetting solvent can be dl verted for purification thereby maintaining the grease content of the jetting solvent at a sufficiently low value without distilling the whole of it after each passage through the jetting chamber.

This form of my invention will now be more particularly described with reference to the accompanying diagrams in which:

Figure 1 represents a plan of a suitable apparatus for carrying out my invention, and

Figure 2 represents a sectional elevation of the apparatus along the line 2-2 of Figure 1.

To avoid confusion in Figure 2 parts 20, l8, l9 and 24 of Figure 1 have been omitted.

In these diagrams apparatus I has a liquor compartment 2, a vapour compartment 4, a tunnel-like enclosure 3 connecting the two above liquor level and a vapour level respectively and drying compartment 6 between the vapour compartment and the exit. Depending partitions 5, 5, one in each of compartments 2 and 4 seal the in ner portion of the apparatus against loss of spray from compartment 3, and endless conveyor 7 conveys goods in turn through compartments 2. 3, 4 and 6.

The level of solvent in compartment 2 is fixed by overflow pipe 8 connecting the upper part of compartment 2 with the lower part of vapour compartment 4, pipe 8 being shaped that a liquid seal is formed therein and vapour cannot enter liquor compartment 2 via that pipe. In the upper part of the vapour compartment are peripheral condensing coils 9, 9 below which are collecting troughs connected by pipe iii to the lower part of compartment 2. Solvent circulation can thus be set up from liquor compartment 2 through pipe 8 to the vapourizing compartment 4 where thesolvent is vaporized by heating means not shown, to be condensed on coils 9 and returned as clean solvent to compartment 2 via pipe 10. Liquor in compartment 2 can be heated by means not shown, escape of vapour being prevented by condensing coils 21.

Jettin compartment 3 is provided near the end in communication with compartment 2 with a plurality of sprays or jets indicated at l4 which may be movable or fixed, but in either case are adapted to deliver solvent on to every part of the surface of the goods moved through the compartment on conveyor 7. Sprays l4 are connected with tank ll through pipes 12 and pump l3. The base of compartment 3 is formed as a tray l5 connected through pipe IE to a second tank ll below the level of the tray. Solvent can thus flow under gravity from tray l5 to tank ll. In accordance with my invention tank I1 is connected to tank I l by pipe 20 through pump 18 and centrifuge l9 which is preferably of the totally enclosed type. Pipe 25 is also provided through which solvent overflowing from tank II can be returned to tank l'l. Tank ll is also connected by valved pipe 2i to still 22 water separator 23 and cooler 24. Solvent can thus be tapped off from tank I! to be distilled and returned to tank ll via pipe 26.

Drying compartment 6 has lateral cooling coils (not shown) by means of which vapours can be condensed and returned to the sump of compartment 4.

In using this apparatus, the cooling liquid is supplied to coils 9, vaporization of solvent is set up in compartment 4, and pumps I3 and I8 and centrifuge l9 are put into operation. As the goods are passed through the apparatus attached to conveyor 1 they are immersed first in thehot liquor in compartment 2 where they received a preliminary wash serving to remove the grosser contamination and to loosen the remainder. The goods are then drawn out of the liquor and while travelling to compartment 3 are drained; immediately on entering compartment 3 they are subjected to the action of a high velocity solvent spray delivered from tank ll via pump I3. Since no solvent can enter tank II which has not been either distilled in still 22 or centrifuged in centrifuge l9, this spray will be free of suspended mat ter, and substantially complete removal of solids adhering to the goods can be attained. In addition the goods are cooled by the cold spray. As the goods move out of the sprays they will be further drained and will then pass through vapour compartment 4 where vapour condenses on them removing the last traces of grease, and out of the apparatus through drying compartment 6 where adherent solvent evaporates from the goods since having traversed vapour compartment 4, they are then in a warm condition. The solvent thus vaporized will be condensed on the cooling coils in compartment 6 and returned to compartment 4,

Th1. jetting liquor falling from the goods will he caught on tray l5 and flow under gravity through pipe it to tank ll. From here the liquor contaminat d with suspended solids and to some extent with dissolved grease, is circulated by pump 18 through centrifuge 19, where it is submitted to centrifugal action which removes solids even in almost colloidal suspension and thence back to tank ll now substantially free from nus-penned solids and ready for redelivery to Jets it. As degrcasing proceeds, grease from the goods will dissolve in the jetting liquor, but the same grease content can be kept at a low value by diverting part of the liquor to still 22, and returning it to tank ll via water separator 23 in which any water introduced into the solvent by the goods can be removed, and cooler 24. The amount so diverted can be regulated by the valve in pipe 2|.

With this apparatus the jetting liquid is maintained substantially free from suspended solids without distilling the whole of it after every passage through the jetting zone, and this is a considerable saving, since a still capable of distilling liquid at the rate at which it passes to the jets would be very large in comparison with the rest of the plant and would require large supplies of cooling water and steam or other source of heat. Moreover the liquid can more readily be kept cool and the jetting action thereby supplemented by a cooling action on the goods so that subsequent vapour treatment can be more eifective. The amount of dissolved matter in the jetting liquid does not increase rapidly since the majority of greasy and oily matter is removed from the goods in the liquor bath, and can readily be kept at a sufiiciently low value by diverting only a portion from the second tank to the still instead of passing it through the centrifuge. Thus while in a given plant liquor may be delivered to the jets at the rate of 1000 gallons per hour, the content of dissolved matter may be kept down by distilling solvent at the rate of only 200 gallons per hour.

It will be appreciated that my invention is capable of many variations, for example, the initial bath of solvent may be omitted, or it may be used cold; again a second liquor treatment may be given after the jetting treatment. Similarly arrangements may be made for removing water accumulating in condensate from the vapour compartment by inserting a water separator in the pipe leading from the collecting trough to the liquor compartment.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. Apparatus for the desreasing of articles comprising a bath of volatile solvent, a spraying device adapted to spray the articles with volatile solvent vapour, a collector below the spraying device adapted to collect the solvent after it has been sprayed over the articles, a storage tank adapted to take solvent from the collector, a conduit from the storage tank leading to a. centrifuge which is capable of removing material from the solvent which is in almost colloidal suspension therein, and conduit adapted to carry cleaned solvent from the centrifuge to a second tank, a second conduit. leading from the first tank to a still and a conduit adapted to carry the distilled solvent to the second tank, and means for delivering solvent from the second tank to the spraying device, said spraying device, collector, tanks, centrifuge, and conduits constituting an independent circuit for volatile solvent used for spraying; said chamber adapted to be filled with solvent vapor being provided with means to vaporize solvent and means to condense solvent vapor. a conduit for carrying solvent from the bath of volatile solvent to the means to vaporize solvent, and a conduit for carrying solvent from the means to condense solvent vapors to the bath of volatile solvent.

2. In a process for degreasing articles by subjecting them to three stages of treatment comprising a first stage bath of hot volatile liquid grease solvent, a second stage consisting of Jets of liquid grease solvent, and a third stage treatment with solvent vapor, the improvement which comprises maintaining the grease solvent in two separate circuits, one circuit comprising removing of hot liquid solvent from the first stage, vaporizing the same for use in the third stage, condensing the vapor after use and returning he condensate to the first stage; the second circuit comprising collecting the solvent from the second stage, submitting a portion to a centrifugal action suflicient to remove material in almost colloidal suspension therein, submitting the remainder of the solvent to distillation and returnin both portions of the thus purified solvent to the second stage.

3. The process as claimed in claim 2 in which at least one portion of the solvent from the sec-- 0nd stage is also passed through a water separator.

NORMAN ROY HOOD.

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