US2499493A - Apparatus for melting coating materials and the like - Google Patents

Description

-atomizing the hot. molten material:

Patented Mar. 7, `-1950 APPRA'TIITS FOR ME MTERIL'S AN LTING COTING D` THE LIKET RobertiCa Gould; .San Marino, Califn. assiglnorgby' me'sne; assignments, to Brogdex; Company-Pof mona, Calif., a. corporation. n

Thisfinvention relates to-iinprovements inap,- paratus for melting coatingl materials andthe like:I andiitlrelateszmore particularly toimprovements inA equipment; employed in. melting: and maintaining in the :molten state asupplyf of waxy material'to1 be used in .protectivelyf coating4 article such as-f-freslly fruits and vegetables.

In the. preparation of fruit and' vegetables for market; it is;commorn practiceto coatrthem with a protective l'm: of? wax-y or similar.v protective material in order' tomaint'ain; the.: fruitor vegettablel in good' marketable condition. Certain widelyemployedrr methods or applyingsuch av iilin coatinginvolue; the* use of apparatus for.v melting the* waxy.v material (e.g.) and.A then spraying or in orderf' to subdivide it. nelya. Typical" examples of' wax coating apparatus in common use for this pur- 'poseI are'- describedin.- detail' in. such patents: as

Skinner' l,830;297 Piercef1,940;269i and.z Burwick etal'. $364,946; Such apparatusfco'n'sists general- 1yr cfa supply. tank in which' the Wax is melted down andmaintainedin; hot'; highly fluid.' condition, and an adjacent chamber intowhich the liquid wax'is'sprayed as the articlesrtolbe coated are passe'dtherethrough andi are subjected tofthe action of revolving brushes.. A` ne spray: orfog of molten wax: is projected" intothe aforesaid chamber by a force-feed.'pumpoperating in con junctionI with a compressed air supply'for spray'- ingor atomizi'ng the liquid waxA feell byf the' pump. For meltingthewaxr andimaint'aining'the.molten wax suiciently' hot to= be highly fluid; there'. i's provided at' a location within-the tanlc and rela:-

tivel'y'close to the'bottomzthereot a-heatingrunit f intheform of 'a generallyfat coil extending' sub1- stantially'parallelto the ftan'kbottomzand consist? ingofa plurality of turns or, bendsf of metal tubing to which steam: under suitablel pressurey may be supplied; or which may enclosean` electrical re'.- sistance heating' element arranged to bef suitably connected` to-current supply mains.. As a: result of'thus forming and" positioning: the: heating unit, Whichmakes foruniiorrnr and otherwise generally advantageous heating effect, the. heating uniti as a; whole is, undery normali' operatingl conditions; alwaysrmore; or less deeply submerged in' the body of hot'moltenwax containedin the supplyftank;

Materials of.; the; general'. class-1 which. apparatus ofi the type,` here involved is; intendedv to handle melt at temperatures relativelylow'as'compared with: the; melting points: of; the.v common, metals1 so; that:` the; heating. conditions: are. not.v especially severe.. Alsoz, thee mannerA of. using the.y molten material doesi not ordinarily' render.- it; necessary orf desirable. that: a: supply of.' material; in. molten condition. bei kept' available. in'. more; than: rela.- tively: small quantity (fe.g.. onthe order of:y 5 toV 1'0 gallons) at; anyv given time. For: mostl purposes, therefore, it; is common and more. or lesszestabP lished practice to.y employ, 'in apparatus: ofv this type/a4 comparatively Lsmall rme1tin'g1tankioi rela.- tively light. andiL inexpensive construction,V made from: sheet metal, for"exampl`ewith1Welded seams or. joints; Moreover, particularly because of: the various: piping: and other connections' between the;` tank. interior: and; external elementsv of; the completey spraying' apparatus. it has. been; found inconvenient and impracticable to'- heat-'insulate the. tank; whose! walls: are therefore; exposed` to thefcoolin'gweiect oi"thezsurrounding:y atmosphere.

In. practice, theapp'aratus may. occasionally be idle for varying-.r lengths of time.; quitegenerally itfissliutY down. for overn'igl'ltv periods; When the shutdownf is to be" fora. substantialperiod; operaitionofatheheating coil is discontinued whereupon the-body of= moltencoatin'g materialfthenremaim ingxthe.. supply tank'. gradually cools',` .finally cooliingfi totv belowI itst melting pointandi congealngif the; shutdown period is sufcientlylong. InV the casef off-a'. waxy: coating` material` consisting: ofi' a mixture of ai. paralni and carnauba. waxes. for example-g. az. particularly: advantageous: type: of coating.T composition Widely used byf citrus fruit packers'l especially, such melting; point; may be on the: orderr of from. 1'70fi`toV 1.759

the liquid state;Y a.. body of. waxy' material of thisu type shrinks considerably'in'volumaoIten as much as: 20%. or: even more; and when. the solidified materiallis rez-melteda correspondingly great? increase in volumeioccurs. If.,` asimayv often happen,` there is; a considerable depth of` molten wax-f` in. the. supply tank when thev shutdownoccurs, and ifth'e.duration.of.y the shutdownlanclfj the atmospherictemperatures-:such asto cause congealing of`A the'. whole body.' ofi wax.J before opera.n tions` are' resumed, the.4 heating; unit; is left. eine beddedii'n solidV coatingfmateriafl;V 0r, if the shut'- dbw-n is? off shorter duration andvv the prevailing atmospheric temperature is higher',.it may beithat onlyfthe upper partoftheJbody of Waxiwlllcom pletelyf solidify to vform a thick' hardl crust; In either case', however; that' portion. ofl thefsupply tank .containing-:the heating.' unit. androccupi'edrby thawax', whether'the;waxzisssolidiedLthroughout they Whole. .or only' a; parti of; its depth,A sometimes becomes.y completely: isolated-l andrsealedv off 'from the-upperportionibyf anoverlying thick layer of hard,. solid; materal extending continuously.7 be.- tweeny the;- ta-nk. walls;v even.L thongl'rfA th'e` upper F. In". solidifyin'g surface distorted as a result of shrinkage strains underof this layer may be very irregular and gone by the material in congealing. When the heating coil is again placed in operation preparatory to resuming normal operation o the waxspraying apparatus, that part of the mass of solidified waxy material which is directly in contact with the coil or closest thereto is, of course, the first to be melted. Since, in melting, this part suddenly undergoes considerable expansion, and

t occur, and it does occur at least often enough -to constitute a source of substantial trouble and expense, not only because of the damage to the tank but, what may be more important, because of the time lost in forced shutdown by the plant employing the spraying apparatus. words, at least the major portion of the solidified mass may soften too slowly under the action of `the heating coil to permit the developed pressure .below said mass to force a vent opening through it for release of the melted material to the upper or exposed surface. Moreover, even if the mass or crust of congealed material does give way, it may sometimes do so almost explosively, with more or less disastrous results.

A primary object of therefore, is to overcome the above-mentioned diiculties by provision of means for ensuring that, concurrently with the initial heating and melting of congealed waxy material immediately adjacent the heating coil, there shall be formed a pressure relief passage or vent through the superincumbent main sealing body or crust of congealed material, whereby material liquefied by the heating coil in the initial or preliminary heating operation may flow to the upper side .of said body or crust, thus preventing develop- Vment of excessive pressure therebelow. Further vand more specific objects of the invention are to provide means of the general character stated which shall be relatively simple and inexpensive, ,yet dependably effective for the purpose intended; and which, in addition, is of such construction and arrangement as to require little or no .structural change or arrangement of other parts commonly associated with the heating coil in wax spraying or atomizing units as heretofore commonly constructed, as well as to afford maximum convenience in assembling and disassembling the component parts of such units.

In accordance with the principles of the invention, its general objective is achieved by the provision of heating means comprising a tubular heater oi suitable metal which encloses the steam or other sourcel of heat employed, located wholly in the lower part of the tank and hence, when the apparatus is operating, submerged in its entirety in the body of molten material in direct contact therewith; together with a metallic member, constituting a blow-hole former, which is in good heat-transmitting contact with the wall of said tubular heater, by integral metallic union or otherwise, whereby to ensure rapid transmission of heat units from the latter to said member. Such blow-hole forming member extends up- In other the present invention,

. Said riser, which is here shown f or loops lying in below that of the upper surface of any congealed body of coating material likely to be formed in the tank even ii, at the time of shutdown, the tank is lled to maximum capacity with molten coating material.

The objects, novel features and advantages of the invention will become further apparent from the following description, taken in .conjunction with the accompanying drawings which illus- `trate one desirable practical form of apparatus embodying the invention, it being understood that this specic embodiment is intended as illustrative only and not restrictive.

In the drawings,

Fig. 1 is a view in side elevation of the coating material supply tank, partly in section on the line I--I of Fig. 2;

Fig. 2 is a plan view of the apparatus with the tank cover removed; and

Fig. 3 is an enlarged cross-section of a detail taken on the line 3-3 of Fig. 2, looking in the direction of the arrows.

Referring to the drawings, the wax supply tank, indicated generally at I0, has side walls Il, bottom I2 and a removable cover I3. Mounted within the tank near its bottom is the tubular heater, here shown .as consisting of a at heating coil I4, which in this case is of the steam type and is generally serpentine in shape, having all its turns a plane substantially parallel to but spaced slightly above the bottom of the tank and from the side walls thereof. This coil is provided at opposite ends with unions I5 and I6 by which it is connected to steam supply and return lines II'm and I Ga, respectively, for easy removal from the tank for repairs or replacement. As shown, said lines extend directly through the tank wall at about the level of the coil for connection therewith. At a point on the upper surface of heating coil I4, this point being indicated generally in the drawings at I1, an internally threaded metal socket member I8, here shown as an ordinary nut, is secured in rm metallic union to the coil, as by welding indicated at I8a. This socket member receives and securely holds the threaded end of a metal riser I9, in this instance a solid rod, which is secrewed solidly thereinto and thus supported vertically within the tank. as of suiiicient length to project somewhat above the maximum level of melted wax, indicated at 20, normally maintained in the tank, should possess heattransmitting capacity ample to transmit heat from the coil I4 to congealed wax in contact with the riser, rapidly enough to melt that wax simultaneously with the melting effected by said coil. A riser composed of steel will serve the purpose, or if a metal having greater heat conductivity is used, such as brass, the same heat-transmitting eiect may be obtained with a riser of smaller diameter. With this arrangement, when heat is supplied to the heating coils in re-starting the equipment for operation after a shutdown, not only the wax immediately in contact with the .coil is melted, but also that in contact with vertical riser IS which receives and transmits heat by conduction from the coil on which it is mounted. In this manner, a small annular outlet or blow-hole is created around the riser in the body of congealed wax, so that the wax initially melted by the heating coil in the lower part of the tank can escape upwardly through the overlying mass of congealed wax. This prevents development of any substantial pressure due to exwardlywithin the tank to a level not substantially pansion of meltingV wax below the solid mass.

Removably mounting the heat-transmitting riser on the heating coil I4, especially when this is accomplished through use of the specic mounting means here shown and described, affords important practical advantages. Removability of the riser is desirable because other pieces of equipment included in the wax melting and spraying unit are customarily associated with the heating coil in the supply tank; and, due to the limited working space available in the tank, assembling the various component parts housed therein, or disassembling them as may sometimes be necessary, is much more easily accomplished if the riser is detachable from the coil. Utilizing as the mounting base a nut solidly Welded to the tubing of the coil is a convenient, inexpensive and particularly satisfactory way to hold the riser securely in good `metallic (heat-transmitting) engagement with the steam or electrically heated coil. In the present example, the other pieces of equipment contained in the tank as just mentioned includea force-feed device 2 I,acompressed air reservoir 22, an air header 23, all connected to spraying or atomizing air jets outside the tank, as well as the heat-sensitive element 25 of a thermo-control device (not shown) for regulating the amount of steam supplied to the heating coil I4. These parts are indicated in dotted lines only, and more or less diagrammatically, since they constitute no part of the present invention.'

It will be readily apparent that various other forms of heat-conductive risers, in rod or other form, can be employed to obtain the same or a suiciently similar result. For example, it is possible to form coil I4 with a loop rising vertically to the proper height from the lplane of the rest of the coil. However, especially where thinwalled steel tubing is used as is desirable, fabrication of a coil in such special form is somewhat difficult and relatively expensive. Again, coil I4 could be provided with a vertically extending branch in the form of a tubularr stub closed at its upper end and teed at its lower end into the coil itself to permit steam to ow into the tube directly. It is also possible to weld a vertical riser directly to the coil itself. Apparatus embodying these, as well as many other detailed changes and modifications, while still utilizing the essentials of the invention and realizing the benefits thereof in at least substantial degree, is to be understood as included within the scope of the invention as dened by the appended claims.

What is claimed is:

1. An apparatus for melting waxy materials which expand upon passing from solid to liquid statev which comprises, in combination with a tank: a substantially iiat heating coil within said tank adjacent the bottom thereof and virtually parallel thereto, an upwardly directed, threaded member secured to the coil, and a heat-conductive, blow-hole forming extension rod removably connected to the threaded member and extending upwardly to project substantially through a mass of waxy material congealed from the maximum volume of molten waxy material which the tank is arranged to contain.

2; In an apparatus, including a tank, for melting materials which expand upon passing from solid to liquid state, the provision of: a heating coil provided with a removable, blow-hole forming member, said heating coil being substantially at' and arranged to be positioned adjacent the bottom of a tank; an internally threaded member secured to the upper side of the heating coil by a fused metal connection; and a rod-like, heatconductive, blow-hole forming member removably screwed into the internally threaded member, said blow-hole forming member extending upwardly to project substantially through a mass of material congealed within said tank.

ROBERT C. GOULD.

REFERENCES CITED The following references are of record inthe le of tzhi's patent:

UNITED STATESy PATENTS Number Name Date 2,108,784 Stockdale Feb. 15, 1938 2,361,636 Koppel Oct. 31, 1944 Wollner Mar. 29, 1949

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