US2658796A - Hot-spraying method and apparatus - Google Patents

Description

1953 w. KOPPERSCHMIDT 8,

. HOT-SPRAYING METHOD AND APPARATUS Filed April 27, 1950 2 Sheets-Sheet 1 w. KOPPERSCHMIDT HOT-SPRAYING METHOD AND APPARATUS Nov. 10, 1953 2 Sheets-Sheet Filed April 27, 1950 Fig. :5

Patented Nov. 10, 1953 a UNITED STATES OFFICE 2,658,796 Ho'T sPRAYING METHOD APPARATUS Wilhelm Koppcrs'chinidt;Hamburg;Germany 1 Application April 2'7, 1950, Seri'al No. 158,447

m that theheat required to rhelt or to change-the viscosityof the spray medium is imparted to the latter in several steps at several zones.

The '-apparatus requiredto perform the present hot-spraying orcoatingmethod comprises generally a tightlvclosable pre-heating or melting vessel having atbottom screen with thereabove arranged heatablepipe coil or grating, a recept'acle with a' filter beneath said vessel, circulating' and pressure-increasing means, a heatabl pipe @011, a spray nozzle arrangement within the melting vessel,- and heatable-niaterial feed hoses with attached heatable spray or coating devices. For the application of meltable', thermoplastic, oral iquid materials as spray mediums for corro -sion-resistant, insulating or the'ilike finishes or -coatings, provides} the present invention a method for melting or pre-heatingl material in a container 1 or vessel; for additional" .he'ating of pre hea'ted or niolten material within a receptacle beneath an interposed screen below the melting vessel; for continued heating of the'l'iquid material within a heated pipe coil; and finally -for hotk-eeping or additional heating within the feed linesrconsisting of pipe or hose, and the spray gun orspray-medium, applyingudevice. Actual melting of materialswhich are's'olid or paste like at normal temperatures, "takes'place within a melting vessel and is effected by continuous overspraying and over-splashing oil the solid lumps with'ialreacly molten and hot material kept in circulation; Heatingwithin the main heating zones and during the various'stepsbf the melting and pre-heating process is effected byindi- "rec t heating' Cleaning and rinsing of vessel, receptacle, pipes, hoses andbther devices used the process, is performed with acljeaning fluid by applying the same circulating I and control means as provided. by'lthis' invention for the process itselflan'd with without theassistance "of pressure means such as 'compressed airygases or the "like.

Methods andprocesses previously introduced, generally apply direct heatingm'ethods within a erlieible or the like by whichrelatively great temperature differencesare createdrbtween the heat imparting surfaces. and the material to be heatea'r-sueh concentrated heat causes uneven temperature, distribution "and 'o'verheats' thelmaterial stats which ractijs reason forhardenin'g,

c'arboniration; skin-formation and other troubles. One thothrhahd, is by such methods the heat- .ing period, nevertheless, relatively long.- Furthermore;areapparatus and equipment hitherto 'constructed-,"cothplicated, have low efficiency, and are "not foo1 proof.""They require considerable starting periodsa nd cause difiiculty during and after rest periods 'bychilled and congealed materialcontained in some parts of the apparatus, such"as 'pipes,valves, spray devices, etc.',which are not sufiiciently heated.

The'pr'esen't invention has as its main object to overcome the-disadvantages of" present heaters constructed for'the "purpose in viewand to provide'anapparatus which is simpler inoperation,

reliable inserv-ice, high in efiiciency and low ini'cost.

Another objectofthis invention is to increase the range of application of hot-spraying methodsto ihclude'spray materialswhich, due totheir inherent unfavorable properties, could not-be appliedheretofore because adequate spray equipmentwas not available.

"fOther- "objects and features of thisinvention wm banme apparent on hand of the following detailed descriptiomwhen taken in connection with the accompanying drawings which show diagrammatically some preferred embodiments of this invention and in i which:

Fig.1 shows afside elevation, partly section, ofia tnelting and heating apparatus for hotspraying;

Fig. 2 shows adiagrammatical section' of a spray "devicewithdouble-hose connection. for spray medium" and a single-hose connection for heating 'medium;

'Figs'B to 8 show various modifications of heatable double hose andmultiple-hose connections to suitable spray devices, whereby the hoses serve-invarious ways as feed and return lines for spray and-heating mediums. "Referringnow to'Fig, 1, the heating apparatus here represented "has a pre-heating vessel I with removable but tightly closable cover 2-, a screen bottom B'which may be plane, conical, onspherica'lupor downward. The vessel I hasan' extensionbenefatl'r-screen bottom 3 forming arecept'acle 4f with-filterscreen 5 into which material flowswhich hasbeenmolten and pre-heated in vessel 3.*"=Receptacle 4 is in connection with a circulating and-'pres s'ure-boosting pump, for-example, a*-ge' arpumpi'through pipeline 6. Anotherypipedine 3 leadsfrom pump '1 to a pipe 'coil 9, surroundingpre-heating vessel I. At its other end connects pipe coil 9 to a line lflwith inserted shut-off valve H which terminates in a coupling or joint serving as connecting means for a feed hose of a spray device l2 (Fig. 2). A

' series of spray nozzles 53 are suitably distributed around the upper inside portion of vessel I from which jets of hot medium may be directed to impinge upon the solid or paste-like material deposited within said vessel. Nozzles It can be brought in operative connection either with a pipe line l4 which in turn joins the above mentioned feed line IQ through a shut-off valve or, through a line is with inserted shut-off valve H, to a line l8 terminating in a coupling or 10111'6 to which a return hose of spray device l2 (Fig. 2) is to be connected. Thus the spray nozzles It may be brought in connection either with the feed line l8 or with the return line [8 of the spray device for reason to be described later. Line in, leading to pipe coil 9, may be operatively connected through line IS with inserted shut-off valve and line 6 to the receptacle 4 with filter 5. Connecting line I 9 may be brought into operative connection with return line [8 of spray device [2 (Fig. 2) through line 2i with shut-off valve 22. A heating coil 23 is arranged within the bottom portion of vessel l in spaced relation to screen bottom 3 through which coil a heating medium such as hot oil, derived from preheater 3D, or pro-heated spray medium, branched oil from the spray medium pipes, or steam may be passed; or which may be heated electrically; and on which cold, solid or paste-like spray medium 24 is placed when the apparatus is charged. In this manner the charge is kept away from the screen bottom 3 and thus cannot clog the latter, but may be heated and molten readily when operation starts or when a new charge is introduced. Screen 3 may be plane or spherical toward top or bottom, as has already been mentioned, just as conditions make it desirable. A suitable heatable grating may also be used 1nstead of heating coil 23. Basket-like screens or guards 25 are arranged around the inner side walls of vessel l which extend downward to the screen bottom 3, adjoining receptacle 4, to facili tate downward flow of material molten away from the solids 24, and at the same time permit heated spray mediums, which enter the vessel through nozzles E3, to circulate freely around said solids by action of circulating and pressure-boosting pump I. Pro-heating and molting vessel l is surrounded by heat conducting material 26 such as graphite, aluminum chips, asbestos mixture, or other heat-conducting and heat-distributing material, into which electric heating elements 2'! or steam or hot oil coils are embedded whose heating capacity may be regulated or adjusted by suitable switches or control devices. Vessel l, receptacle 4 with filter 5, the circulating and pressure-boosting pump 1, and the connecting lines with shut-cit valves and adjusting means are accommodated within a container 28 having heat-insulated walls. Within this container are also arranged one or more heating chambers 29 with suitable heating means 30 such as electric elements, steam coils, or coils for hot gases or hot liquids, as for example, glycerin, oil, etc. The heating chambers 29 are connected to measuring and control means 32, 33 and to a pressure gas or other heating source through a pipe line 3|; to a circulating pump 19; and to a pipe line 34 with shut-off valve 35 leading to couplings or joints to be connected to hoses of spray device l2 (Fig. 2). A branch line leads from pipe line 34 to heating coil or grating 23.

In the embodiment of this invention as shown in Fig. 1 serves one heating chamber 29 by means of its heating fluid circulated by pump 19, to supply heat to heating coil 23 above screen bottom 3 and into the heated double-hose lines indicated in Figs. 2 to 8; and the other heating chamber 29, for the purpose of heating, a protective gas or a pressure ga to be used in the spray device I2 (Fig. 2) as will be described later.

Shut-off valves and control means as well as the circulating and boosting pump 1 are provided with heat preserving and heating means to shorten the starting period of the apparatus and to prevent that heated and therefore liquid material chills and congeals within these elements which otherwise would clog and cause trouble. In some cases it may be advisable to heat container 28 in which above elements are accommodated at times completely or partly, for which reason the drive motors of circulating and boosting pump 1 and'circulating pump 79 have preferably to be shielded from the heat or be installed outside of container 28. The temperature within container 28 is preferably maintained within suitable limits by thermostatic regulators.

Some completely closed cleaning fluid reservoirs 36 and 31 and a pressure vessel 38 are mounted directly adjacent to container 28. Pressure vessel 38 is in connection with cleaning fiuid reservoirs 36, 3'! through lines 39, 40 with inserted shut-oil valves 4|, 42. Furthermore pressure vessel 38 has connection with intake line 6 of circulating and boosting pump 1 through line 43 with inserted check valve 44. Check valve 44 admits cleaning fluid into line B only under pressure and prevents return flow. Cleaning fluid reservoir 36 is in connection with shutofi valve 46 through line 45 and cleaning fluid reservoir 31 with shut-off valve 48 through a line 4?. Both shut-off valves 46, 48 join with their opposite ends line 6 which in turn is in connection with circulating and boosting pump 1, as already mentioned above. Thus, the cleaning fluid reservoirs may be brought in operative connection with the pump at option. Pressure vessel 38 may be operatively connected to a compressed air source through a line 49 with inserted shut-off valve 50. Operative connection mayv also be established between pro-heating and melting vessel l and a compressed air or pressure gas source through line 5| with inserted three-way valve 52 and control and measuring instruments 53, 54. As has already been mentioned, can cover 2 of vessel I be pressuretightly closed. The closing means 55 of cover 2 may be preferably interlocked with three-way valve 52 in such a manner that the cover cannot be lifted sooner than the operative connection with the compressed air or pressure gas source is interrupted and vessel l, through three-way valve 52 and check valve 56, is vented to the open air or a pressure equalization vessel. Check valve 55, installed within vessel I, prevents accidental entrance of hot spray medium or fuming particles thereof into line 5! at the moment of a sudden opening of three-way valve 52. A pressure-relief valve 82 in cover 2 prevents excessive pressures within vessel l. The closing means 55 may be of the safety-type so they brake if sudden explosive pressures should develop within the vessel.

A gage 8|, indicates the pressure of spray medium in line [0 leading toward spray device [2 (Fig. 2) which is the working or spraying pressure. 1 z'Ihermocouplesa. or other. itemperature achecking meansare installed at. .variousapoints along the circulating path of the. beating medium as well as. along the path of the .hot. spray medium; heating. 0011', and hot gases; to .actuate temperature .controls. and quantity -measuring instruments, andv permit supervision otallphases of the melting process. Aline 51 with-inserted pressure relief valve 58 connectsasuction-nand pressure side of circulating-pump l sothatin .case of excessive pressure within .the-sprayme- -mediums which are not solidwhen cold, by subjecting the latter tohigher hydraulic self-pressure orfby applying compressed .hot gases to producethe spray. Spray device l2 comprises a spray chamber 59 withaax ially rslidable nozzle needleBU and nozzle 6|; Aheatingschamber 62 for hot air or hot gases is: arranged around-the front portion of chamber 59 and the :hotgases supplied under pressure to chamber GLmay, completelyor in part, be applied to atomize the spray medium issuing-from the nozzle or to form a protective gaseous jacket-aroundsthe spray jet. Spray chamber 59: has connection with the-heatingapparatus (Fig. 1) through spray medium feed -1ine 55 which is surrounded by a jackethose 66 consisting of pressureand .heatn'esisting material, such as certain .rubber grades,-and through whose Jacket space .61. spray medium which has not beenejected through the nozzle, is returned to theheater. Another single hose or a doublehose is connected to hose coupling 63 and serves to feed. or toLcirtzulate hot compressed air or heated fluid from heating apparatus Fig. 1.

In the spray device according to Fig. 3 serves a hose 95 connected to coupling. 69 as feed line for hot spray medium. .Another innerhose 65 is accommodated within those 66,, joining .the sprayer at 68, through which hot compressed .air or gas is passed serving toheat spray chamber 59, or toatomize spraymedium, or to form a protective jacket.

In. the modification of a spray device shown in Fig. i serves the same double hose "65,166 to supply hot in spray medium and hot compressed air or gases to the sprayer, whereby hot spray medium passes through the inner hos.65 and the heating gases through the jacket. space" 61 between inner hose65 and jackethose 65.

In another modification shown inFig; 5, it will be noted that besides the double hose B5," 66 similar to the one shown in Fig. '4 and joining at 63, 69, anadditional single hose 10 is joined to the sprayer at 65. In this"arrange'ment serves the inner hose 65 to feed spray. medium and the jacket hose 6B in cooperationwith single hose l0, serve for circulation of heating mediumsuch as hot oil, hotair or the like. The circulating direction within single hose 'Hla'nd jacket'hose 66 may be so chosen that either unidirectional or counter directional flow of the 'twomediums; that is heating medium" and spray medium; results in the double hose 65, 66.

6 .JEhe, spray device. shown. in.-.Fig.; J6. has .-,pro- .visions for the-connection- .of two double=hose lines 6 5.; 66-, .whereby. preferably. the .innen-hoses E35 serve aswfeedrandi-returnaline. for hot spray medium, and the. outer or iacket 151056576 6. fonthe passage of heating- :medium. Her-ebyLnalso, either .uni directionalor counter-directional flow of the mediums may bev chosen depending on which-method is most suitable for a certain application.

.-According to-Fig. 7 1s a .suitablenumber. of from-two. to -four. zsingle hose .lines- 65,. 65 72., 13 inserted'into a protective jackethosellc. .One hose-.55 servesas feed line for hot spray medium. When-two 110.8%;65, asindicatedinFig. 7, are applied, serves one as deedand the other as return. line for spray medium between-heating apparatus Fig. 1 and-spray.- device 12. lHose; .;12 serves in cooperation .withi iacket space 611 of jacket hose H for circulation of hot oil orohot gases. forthepurpose of heating. spraymedium withintheiline and .inthe spray device.. .A fur ther =hose-l3 maybe added to serve ascsupply line for hot. compressed air or gas, used-to im-- prove atomiaationof the spray orto. form aprotective gas jacket around-the spray. -It.has been found advisablato .comb-i-nethe-hoses65 into a double hose :as shown-in- Fig. 4. severalfeet before joined to thesprayer, in order to enhance the movability. of thesetup.

. A-line'system of: threeto five single. hoses is packed in heat-insulating. material -14. within a protective-metal hosen'lfi in an arrangement indicated in Fig. 8. The single. hosescserve as feed, or as feed and return lines, for hot spray "medium and heating medium, and in addition .for supply of compressed air orgases needed for atomization or. spray :jet. protection. The single hoses preferably emerge-fromthe protective hose 75 several feet before joined to the sprayer l2 and are at thesamepoint combined into double hoses leading to the sprayer inthe samemanner as shown inFig. 6.

i The inner hoses according to.Figs. 2 to 8. are

preferably of the.flexibleametal-type whereas theouter or=jacket hoses, according to Figs. 2 to '7;v consist of heat-insulating material such as artificial. rubber, fabrics, or .the .likeand are surrounded: by. a. pressure-resisting covering. "The. jacket hose according toFig. 8 needs only to. confine and protectthe insulating material 74 and may be accordingly constructed. Forhotspraying by selfrpressure according .to the present invention, hav'ethe. inner hoses to.withstand temperaturesi of about-400. degrees centigrade and pressures up to 4000 lb. p.,sq. in., depending. on. kind' of. medium applied.

" iThe term thermoplastic materials asapplied throughout the description of .thisinve'ntion is intended to include allasuch. materials "which, by increase of temperature, either change their viscosity or convert .from a solid into a liquid state. of varying viscosity." In applying material,'such as"bitumen; synthetics, or the like as spray. niediumfor protective coatings against chemical" deterioration or as insulation, with the apparatus of the present; invention, the gene ally "soli'd material'lumps 24' are. placed on heatingcoil or grating23 inpreeheating vessel 1, cover 2 is tightly closed, and electric,"steam, or fiuid heating'.means 2"! turned on to' melt the material. The screensorguards 25 arou'ndthe inner wall of the preheating vessel assure, thereby free downward flow of" molten sprayr medium through screen bottom? and into receptacle 4 which is also electrically, steamor liquid-heated 7 device I2 (Figs. 2 to 8).

and in which the temperature of the molten material is further raised. The spray medium then passes the filter screens 5 and enters line 6 leading toward circulating and pressure-boosting pump 1. The level of molten spray medium. rises, reaches finally screen bottom 3 and comes in contact with still solid lumps on heating coil 23, and accelerates in coaction with the latter the melting process. The circulating and pressure-boosting pump i presses liquid spray medium through line 8 into pipe coil 9 wherein heat-- ing means 2? cause a further increase in tem perature of the spray medium to a suitable working value which may be as high as 500 degrees centigrade and above. The melting process of solid or paste-like material within pre-heating vessel I, can be further accelerated, after enough liquid material has accumulated within receptacle 4, by applying circulating pump '5 to pump spray medium, whose temperature has been raised to working temperature within pipe coil 9, into line It and adjoining line Ilito be issued through nozzles I3. Thus, hot material is splashed over the still solid lumps with the effect of greater heat penetration and faster meltin Having now sufficient working-hot spray medium within the apparatus, some of it may be diverted for spray application by opening shutoiT valve I i and admitting it through the adjoining hose coupling into feed lines E 3, E5 of spray Spray nozzles 53 within pre-heating vessel I may be connec'ed to the spray medium return line I8 by opening shut-oft valve i! in which case, however, the tempera.- ture of the spray medium issuing from the nozzles I3 is somewhat lower in account of losses within the hoses leading to and from the spray device I2. During continuous operation of the setup is steady melting of solid material, resting on heating coil or grating 23 within pre-heating vessel I, preferably effected by spraying and oversplashing with hot material through nozzles I3. Thus, it is possible to begin spraying operation after a relatively short starting period and to melt-down practically only such quantities of spray medium as actually are used-up by spraying; This fact offers the advantage that relatively small and light equipment will suifice for substantial quantities of material to be dispersed, because the rate of melting-down depends to a great extent on the amount and temperature of liquid material ejected from nozzles I3 onto the solid material.

When applying only a spray medium feed line between heating apparatus Fig. l and spray device I2, shut-off valve II is opened and the pressure regulated with regulating valve E5 to a value, corresponding to anamount which can be consumed by spray device I2. Only a small portion of liquid spray medium is thereby diverted into the feed line, whereas the greater part is kept in circulation through line I4 and ejected through nozzles I3 by action of circulating and pressure-boosting pump 7. When material is worked with, which is not solid when cold, the circulating and ejecting action of pump I may be stopped by opening a shunt line through valve 80. Spray medium, pre-heated in vessel I may instead be pressed by compressed air or gas into pipe coil 9, to undergo further heatingup to reach working temperature, and hence, after opening of shut-off valve II, directly into the feed line of the spray device. If material, which is not solid when cold, is to be sprayed under self-pressure, remains valve 8|] closed and circulating and pressure-boosting pump I presses material, emerging from receptacle 4, through pipe line 6 under high pressure into pipe coil 9 from where it enters through shut-oil valve II into feed line 65 (Figs. 2 to 8) of spray device !2, and, when a return line is applied, returns through such line, reentering the heating apparatus through pipe line I8, after valve 22 has been opened, progressing to the inlet side of circulating pump 1 and, after having passed the same, is pumped into pipe coil 9 where it regains temperature and repeats the circulation thereafter as just described. It is advisable not to operate spray nozzles I3 when working with material which is not solid when cold and so heat only smaller amounts at a time which can be readily sprayed out within short periods. Spray medium fed into the spray device but not sprayed out returns through lines 61 or 65 to heating apparatus Fig. 1 and enters, after shutoff valve I'Ihas been opened, into line It leading toward nozzles I3 whereby supply to said nozzles through line It may be interrupted by closing shut-oil valve I5. However, if it is desirable not to operate spray nozzles I3, such fed-back spray medium may also be deviated into lines 2|, I9 and 6 toward the suction side of circulating and pressure-boosting pump I if shut-01f valve 22 is opened.

Double or multiple hoses serve generally to pass hot spray medium between heating apparatus Fig. 1 and spray device I2 in such a manner that spray medium either flows in an inner ho se, where it is protected against heatdissipation by a surrounding jacket hose through which heating medium is circulated, or that the spray medium flows in the jacket hose and the heat dissipated is replenished by the heating medium flowing in the inner line. When two hoses 65 for feed and return of hot spray medium are applied, it has been found advisable to also construct the return line as a heatable double hose to prevent congelation of back-fed medium. Heating of the hoses may be accomplished by hot liquids or hot compressed gases such as compressed air, whereby a fraction of the circulating hot gases may be ejected from the spray around spray nozzle 6| to improve atomization of the spray or to form a protective gaseous jacket around the issuing jet. If spray mediums have to be applied which can stand the high temperatures necessary for their spraying only for very limited periods, a method applicable with a spray device according to Fig. 5 is used whereby the hot spray medium, when leaving pipe coil 9, has yet a safe temperature but has not attained its working temperature and on passing through hose B5 is subjected to the heating effect of heating medium with higher temperatures circulating in the surrounding jacket hose 66. Thereby is the circulating path of the heating medium, through jacket space 61 and single hose I0 either uni-directional or counterdirectional with the spray medium to be further heated. Thus, the temperature-sensitive spray medium attains its proper spray temperature not sooner than shortly before it is ejected into the spray. Temperature and the rate of flow of the heating medium, which is circulated by pump I9, has to be closely adjusted and held to calculable values depending on the length of the hoses, the temperature rise to be effected, and the rate of flow of the spray medium. The above method is recommended, when a temperature-sensitive spray medium will stand the most favorablehot-spl'tl temperature, at which it also has the--proper viscosity-,--for*only very-short periods without harmful effects. Besides hoe liquids-y also hot-air or =hot -gases-maybe used for -hose heating withgood'resultsw When applying hose heating-mean s; it is always advisable to provide --a feed and -return line for heating mediums such as air, gas or liquids. Theappli cation of gaseous heating means 'in the' apparatus of the present description, requires-the: connection of -heating' chamber 29 toa com pressed air or pressure gas source and suitable control and measuring instrumentsw When compressedand heated air or the like circulated forthe purposeof-hose-heating; it gives' the" advantage that a fraction ofit may simultane t ouslybe usedin the spray'devicepropento assist.-

in atomization of the: spray-medium :or, "in hy -fl draulic self-pressure spraying, to form a protect-t tive gaseous jacket around the issuing anddis- 2 persingspray jet. tFor very close temperature control of spray medium within theihosesuheating elements may be arranged around the latten having automaticocontrol by thermostatsuand being: mechanicallyliprotected. to the: outsidervby a suitable covering.

Means are providedsin thenpresent apparatus. to introduce certain gases into: thersprayl medium by absorptions-under pressure... eForithi's purpose i vessel I: can be operatively connected to :aa corner. pressed airmor L pressureegas. sources with. control and measuring: means "53,154,: throughsline, 5i three-way valve 5211-and2a check valve 561 .Gasesi entering this-way into; :vesseLl will. be absorbed by thespray medium,=.-issuing in a finehotrspray 5 from nozzles 13,.to nan extent.:whioh depends-on: pressure andrtemperature. within the rvessel, and; t on the chemicaltconditionyof gases. andxspray; medium. 1 t Such: anti-intimate and; :perfect inter? mixture. of gases may-she advantageously applied in certain chemical transformingxprocessesuof; theispray medium; Furthermore. tfind the under pressure absorbed gasesofcertains chemical compounds to escape again under: normal ,pressur e. In the present process ,is, spray; medium,,,which has absorbed a ga esgunder. pressure, released. to normal pressures. thelniflmentcit issues fromnthel, spray nozzle, 61,, The so escaping gases improve dispersion of the'sp rayt or may ereate. a latherlike emulsion and spongy coatings sometimes desirable for insulation of surface or the'lik. If, however; thesurface to be-finishedhas 'to be smooth-and glossy; it is advisable to work Without: air pressure within-pre-heating vessel-l to pre vent the formation of airbubble'sr- The subdivision of theheatingrprocess ofthe spray medium within-the presentapparatusinto several steps and *Zonesofiersthe advantagethat only moderate temperature differencesprevail" between the spray medium to beheatedandthe contacting heat impartin'g surfacesgwherebv is assured that partial'overheating is not encoun-- tered and troubles such as carbonization, 'gela 'i tination, clogging," disintegration or the ?'like 1 are notlikely to 000111;,T11USBV8II extremely heatsensitive spray mcdiumspan'be applied with pe1 feet. results; Arran ement o fheater. coil 2331 113.? coil; 9; and, spray nozzles. 13in connection with circulating and pressure-boosting purnpJQaLlloW byproper operation very short starting periods 7 atthe beginning; and to quick recuperation after i subsequent new chargesyand' so assure"uninter'-' rupted service. i

The heating apparatus with-*all accessories as just described, results in a relatively smalleand light spray setup which may be moved. without difficulty evenmeans-'for heating 'spraymedium and keeping 'it hot-within connecting lines of any length and within the spray device 'permit's Test-periods of any duration and hot-spraying of otherwise unaccessible surfaces such as within small rooms; inner walls of containers and -boilers;-structural steel-works or the lik'eh The chamber Within container-23 which contains the pipe lines; shutoii valves; circulating and pressure-boosting means, is preferably 'filledcwith heat-conducting material such-as graphite or the like having" heat'- ing elements-- or h'eatin g'" coils embedded in it espeeially witliirr the vicinity of above named units; I By 'suchmeans they may be heated independently and-quickly 'du-r ing starting periods, to accelerate temperature rise and: may be 1 kept warm during restperiods to prevents-pray medium, entering through line 6, f-romchilling -and-clogging the passages. Suitable measuring instruments are installed and connected to outlet line I G, in order that temperature: and pressure of the spray=medium-on leaving the heating apparatus may be registered, and the heating means within the apparatus correspond continuously controlled and ingly be adjusted. It is optional to perform these adjustmentsmanually or automatically.

It will be understood that the present heatingapparatus may be modified in construction and: arrangements of parts and inapplicatidn of means in various ways: without departing from" the scope of this invention: The apparatus is primarily devised for'hotrspraying' of thermoplastic materiala but: may also well be :used for materials whichrequireles's heating. In the latter caseneed the-'heatingmeans to be adjusted only for .moderate. ltemperatures.-- Heating coil 23 can-thereby be heatedwith hot spray-medium: by operatively connecting said coil manner to the uppermost: winding-of pipe'coil B.

If, howeverya short: starting period'With-quick temperature rlse: is essential; it i's prefer'abl'e' to heat coil 23 withhot-heating medium-derived from heatinglchamberwzfi; 'or by steam or electricity.

Cleaning-of theaapparatusafter it has been used for heating 1. of thermoplastic material for' some time or when changing from onespray medium to another -r-is, according to this invention,

performed an? easy manner-by 1 flushing with cleaning fluid as will now' be described:

Afterwhaving sprayed out all remnants of spray* medium fromwall pipes andefittings which willleaverbyunormal operation and after having drainedwtheremaining material from the lowerparts of containers and: pipe lines 1 through drain= T valve: 83,: cleahing fiuidfrom reservoir 36 ol -37 is admitted to "the system :by opening oneof the shut-off :valves '4'l, l2. "After a sufiic-i'ent amount of cleaningr. fluid has entere'd; va1ve-4-| or 62 is again: 'closedriand pressure. gas admitted into" pressure vessel 33 'through line '49 by opening" shute-off valve Elli- Cledhing fiuid-is therebypressed through lined-s and check valve 44 into i into all -containers; re- Manifold" pipeline 5' and, hence ceptacles, pipe lines, valve's'and hosesecirculation of cleaning fluid is effected by correspondingsmanipulation.1of valves and control means;

Preeheatingvessel A is ablysenhanced by P operation of pressure-boosting pump -l which to hard accessible places: The

rendered pressureless by correspondingly setting three-Way valve 52? Thezrcleaning -and flushing action is *consider- .c circulating and? passes cleaning":

11 fiuid through all lines and control means of ing'apparatus Fig. l as well as through the connecting hoses and spray device l2. fluid entering under pressure through filter screen and screen 3 from the bottom into pre-heater l removes residuals and rinses the screens thoroughly. After pressure vessel 38 has been emptied of cleaning fluid, compressed gas, admitted to the vessel as above mentioned, follows through line 43 and check valve 44 into line 6 and in turn from the bottom into pre-heater I where it agitates the cleaning fluid contained therein. Such agitation improves further the cleaning action on filter screen 5, receptacle 4, screen 3, heating coil 23 and pre-heating vessel l. After sufficient action of the first charge of cleaning fluid valve 50 is closed, the position of three-way valve 52 changed, and a return-line valve 46 or 48 opened whereby the soiled cleaning fluid is returned to reservoir 36 or 37 by action of compressed gas entering pre-heater i through line 5|. Most of the cleaning fluid contained in pipe lines and hoses is thus also returned. Remnants may be drained off at joints and suitably placed drain valves. The same flushing and cleaning procedure may be repeated by admitting another charge of. cleaning fluid into the system, but now from the other one of the reservoirs 36, 31 which stillcontains clean fluid. Each filling of cleaning fluid may be repeatedly used either for first rinse or for finish rinse according to its impurity. All flushing operations are performed with all containers and openings to the outside closed, in order that no dangerous gases can escape into the work room. This fact prevents health injuring and explosive fumes which usually form when cleaning fluids, which mostly have explosive character, evaporate into the atmosphere. .As evaporation of cleaning fluids usually take place already at relatively low temperatures, though their boiling points lie much higher, losses of cleaning fluid by evaporation are also prevented by flushing within a closed system. When the cleaning fluid has been substantially soiled and contains so much foreign matter that it is not suitable for further use, it may be drained from reservoirs 36, 3'! and the latter be filled with clean material.

The application of several hose arrangements according to Figs. 2 to 8 makes the following spraying methods possible: The arrangements according to Figs. .2 to 4 are preferably applied when it is necessary to spray materials which are not solid in normal temperatures but have at the most a high viscosity, whereas the arrangements according to Figs. 5 to 8 serve best when working with spray mediums which are completely solid at normal temperatures. When Working according to a pure self-pressure spraying method under hydraulic self-pressure of between 70 and 400 lb. p. sq. in., without any compressed air or gas addition to the spray whatsoever, are the hot air or gases fed into heating chamber 62 of spray device 12 solely applied for heating or for formation of a protective gaseous jacket around the spray jet.

heat- Cleaning I 12 p centigrade to get spraying. 1

If electric hose heating is applied, the electric heating elements are preferably embedded within the thermo-insulatingmaterial l4 packed around all feed hoses within the protective jacket hose [5.

An arrangement according to Fig. 5 should be a most simple and suitable one for normal use when working with at present most costumary hot-spray mediums having working temperatures up to about 200 degrees centigrade. Whenusing very temperature-sensitive spray mediums,-

a suitable pre-calculated amount of heat, depending on length of'hoses and temperature required, may thereby, be imparted to the spray medium while the same passes through feed hose It will be understood that of the various hose arrangements shown, all may be alternately or interchangeably applied or other combination as described be used.

The spray medium may be dispersed either by application of only correspondingly high hy-' heat or hot fluid heat for heating of the several heating zones and accessories of the heating apparatus Fig. 1.

It is to be understood that the invention herewith described in connection with a preferred embodiment thereof, is susceptible of various modiflcations, of changes in arrangement and construction of parts, without departing from the principles. spirit and scope thereof and I do not wish to limit myself to a precise arrangement except as hereinafter claimed.

I claim:

1. In a melting and spraying apparatus for thermoplastic materials, a melting and preheating vessel; a screen-like bottom in said vessel; a grid for supporting said material in spaced relation above said bottom; a receptacle beneath said bottom; a pipe coil around said vessel; means for heating said grid, receptacle, and pipe coil; spray nozzles within said vessel; means effecting communication between said vessel, receptacle, pipe coil, and spray nozzles to form a closed system thereof; pressure inducing means in said system to eifect circulation of the molten material; and means connecting said system with a point of use for said molten material.

2. An apparatus as set forth in claim 1, in-- cluding a return conduit from said point of usefor the return of unused material to said system.

3. An apparatus as set forth in claim 1, including heat conducting material in which said vessel, receptacle, and pipe coil are embedded, heating means embedded in said heat conducting material, and means for controlling the heat.

ing a basket-like screen within said vessel, located.

in a suitable condition for" Hot air, hot gases, hot liquids or.

13 at some distance inside the walls of the vessel and extending downwardly to said screen bottom.

5. An apparatus as specified in claim 1, in which said circulating and pressure-inducing means comprises a high-pressure pump.

6. An apparatus as in claim 1, including a container for cleaning fluid conduit means connecting said container with said circulation system, and regulating means for said conduit means.

7. An apparatus as in claim 1, including a pressure-gas source, conduit means connecting said source with the circulation system, and regulating means for said conduit means.

8. In a process of melting a thermoplastic material and maintaining it in a hot condition suitable for spraying, by application of heat through conduction and radiation thereto, the improvement comprising the steps of applying an additional amount of heat to the unmelted material by spraying said material with part of the melted and heated material in a closed vessel *and introducing pressure gas in the melted material.

9. In a process of melting a thermoplastic material and maintaining it in a hot condition suitable for spraying, the steps comprising applying conductive and radiating heat to said material in a solid state in a closed vessel, conducting the material in a molten state from said vessel in a closed conduit system, applying additional heat to the material in said system, conducting a part of said molten material back to the unmelted material and spraying it onto said unmelted material, conducting another part of said molten material from said system to a point of use during further application of heat and returning to said system any unused part of the molten material conducted to said point of use.

WILHELM KOPPERSCHMIDT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 905,190 Ingersoll Dec. 1, 1908 1,378,637 Wall May 17, 1921 1,541,849 Reynolds June 16, 1925 1,694,806 Yale Dec. 11, 1928 1,778,551 Etnyre Oct. 14, 1930 1,821,292 Chase Sept. 1, 1931 1,865,556 Chase July 5, 1932 1,968,992 Conkling Aug. '7, 1934 1,993,973 McNeil Mar. 12, 1935 2,048,912 Ziska et a1 July 28, 1936 2,123,604 Johnson July 12, 1938 2,197,792 Erickson Apr. 23, 1940 2,300,083 Worthington Oct. 2'7, 1942 FOREIGN PATENTS Number Country Date 614,626 France Sept. 21, 1926

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