US3001508A

US3001508A - Molten material coating furnace

Info

Publication number: US3001508A
Application number: US754875A
Authority: US
Inventors: Ernest F Elliott
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-08-13
Filing date: 1958-08-13
Publication date: 1961-09-26
Anticipated expiration: 1978-09-26

Description

Sept. 26, 1961 E. F. ELLIOTT MOLTEN MATERIAL COATING FURNACE 2 Sheets-Sheet l Filed Aug. 13, 1958 www Q NW Nvww. mm..

sept. 26, 1961 E. F. ELLIOTT 3,001,508

MOLTEN MATERIAL COATING FURNACE Filed Aug. 13, 1958 2 Sheets-Sheet 2 S Q N a N N Y Y QW NN NN m N0@ N 3,001,508 ML'IEN MATERIAL 4CA'I'ING FURNACE Ernest F. Elliott, Rte. 1, Houghton Lake, Mich. Filed Aug. 13, 1958, Ser. No. 754,875 1l Claims. (Cl. 118-417) This invention relates to furnaces and, in particular, coating `articles with molten material, such as molten glass, in order to prevent the surface oxidation of the article by so protecting it.

One object of this invention is to provide a tilting furnace for coating rollable articles, such as steel billets, with molten material, such as glass or other silicate compounds wherein means is provided for rocking the furnace so as to roll the articles in and through a bath of molten material and at the same time advance the articles, by such rolling, through the furnace.

Another object is to provide a tilting furnace of the foregoing character wherein the tilting motion of the furnace can be regulated in such a manner as to adapt it to the proper heating of a wide range of different sizes of rollable articles to be coated, and also to facilitate the discharge of the steel billets or other articles from the furnace.

Another object is to provide a tilting furnace of the foregoing character wherein the rolling of the billets from one end of the furnace to the other is made use of to discharge the billets at the outlet end of the furnace by making use of their momentum to cause them to climb up a ramp and over a barrier at the end of the furnace while at the same time preventing the bath of molten material from spilling over the same barrier.

Another object is to provide a tilting furnace of the foregoing character wherein the bottom of the furnace is so shaped as to contain only a shallow pool or bath of molten material, thereby leaving the major part of the rollable articles, such as steel billets, projecting above the surface of the bath :and exposed to the heat of the furnace, thereby enabling the articles to be heated much more rapidly than when the billets are immersed in the bath, thus obtaining a more rapid production of coated articles than in prior molten material coating furnaces.

Another object is to provide a tilting furnace of the foregoing character wherein the billets or other rollable articles are heated by spaced multiple burners disposed along at least one side of the furnace so as to enable the precise adjustment of the rates or heating required for different compositions and types of steels and complex alloys.

Another object is to provide a tilting furnace of the foregoing character wherein the rollable articles to be coated are preheated prior to their being inserted in the molten material bath, preferably by heat reaching the articles from the furnace, such as in an antechamber or recuperator, so as to prevent the congealing of the coating upon the otherwise relatively cool billet as well as reducing the time required for heating the billet in the main chamber of the furnace itself.

Another object is to provide a modified tilting furnace generally of the foregoing character but additionally providing transverse fulcrum ridges on the oor of the furnace to enable the rolling of billets of non-circular cross-section, the fulcrum ridges assisting the billets in tumbling over them as the furnace tilts, and preventing mere sliding of the billets and consequently avoiding the incomplete coating of the billets.

Other objects and advantages of the invention will become apparent during the course of the following description of the accompanying drawings, wherein:

FIGURE l is a diagrammatic central longitudinal section through a tilting molten article coating furnace, ac-

3,001,5@8 Patented Sept. 26, 1961 cording to one form of the invention, wherein the furnace rocks upon rollers disposed between arcuate races; together with an electro-hydraulic circuit for tilting the furnace;

FIGURE 2 is a horizontal section taken along the line 2 2 in FIGURE l;

FIGURE 3 is a diagrammatic central longitudinal section through a modified tilting molten article coating furnace wherein the furnace rocks upon a pivot shaft, with the reciprocatory fluid motors and circuit omitted; and

FIGURE 4 is a fragmentary longitudinal section through a portion of the furnace iioor of a further modied tilting molten material coating furnace particularly adapted for the coating of articles of non-circular crosssection.

Referring to the drawings in detail, FIGURE l shows diagrammatically a tilting molten material coating furnace, generally designated 10, according to one form of the invention as operated by pressure iluid, such as hydraulic pressure fluid, supplied to it from a pressure-Huid supply circuit, generally designated 12. The furnace 10 is mounted on and supported by a bed 14 adapted to rest on the oor or foundation 16 and havingan upstanding elongated arcuate lower race 18 provided with an upper concave arcuate cylindrical race surface 20 having upstanding abutments or stops 22 and 24 at its opposite ends for limiting the to `and fro rolling of elongated supporting rollers 26 engaged by the convex arcuate cylindrical surface 28 of the elongated upper race 30. Resting upon the substantially at upper surface 32 of the upper race 30 is a baseplate 34 from which the upper race 30, in effect, depends. Secured to and depending from the opposite ends of the base plate 314 are operating connection brackets 36 and 38 and upon it rests the tilting furnace unit 40, subsequently to be described.

Pivotally secured at 42 and 44 (FIGURE 1) to the brackets 36 and 38 are yokes 46 and 48 to which the outer ends of piston rods 50 and 52 are bolted or othenwise secured. The piston rods 50 and 52 at their inner ends carry

piston heads

54 and 56 reciprocable in

cylinders

58 and 60 provided at their opposite ends with

service ports

62, 64 and 66, 68 respectively. The rearward ends of the

cylinders

58 and 60 carry ears 7 0 and 72 by which they are pivotally mounted upon pivot pins 74 and 76 secured to brackets 78 and 80 projecting horizontally toward one another from supports 82 and 84 respectively resting upon and rising from the iloor or foundation 16. The piston rods 50, 52,

piston heads

54, 56 and

cylinders

58, 60 together with their immediate connections, constitute reciprocable iluid pressure motors, generally designated 86 and 88 respectively.

The reciprocable fluid pressure motors 86 and 88 (FIG- URE l) are supplied with pressure fluid .from the pressure fluid supply circuit 12, in this instance shown `as a hydraulic circuit, through

pipes

90, 92 and 94, 96 leading respectively from the

service ports

62, 64 and 66, 68 to rotary control valves or reversing valves 98 and 100 respectively. Each of the control valves 98 and 100 has a rotary valve member 102 or 104 provided with operating

arms

103 or 105 and rotatably mounted in a hollow

cylindrical casing

106 or 108. The casing 106 has

service ports

110 and 112 connected to the

pipes

90 and 92 and also pressure fluid supply and

discharge ports

114 and 116, whereas the similar control valve 100 has similarly-arranged

service ports

118 and 120 connected respectively to the

pipes

94 and 96 and also pressure Huid supply and discharge ports 122 and 124 respectively.

The rotary valve members 102 and 104 are provided With

upper elbow passageways

126 and 128 and

lower elbow passageways

130 and 132 with their outlets arranged at the four points of a cross to communicate with the previously-mentioned

casing ports

110, 112, 114, 116

of the control valve 98 and to the similarly-arranged

ports

118, 120, 122, 124 of the control valve 108. The discharge ports 116 and 124 of the casings 106 and 10S are connected to

discharge pipes

134 and 136 leading toV a suitable fluid reservoir or tank (not shown), whereas the pressure

fluid supply ports

114 and 122 are connected by

pipes

138 and 146 to the discharge side of a conventional constant delivery pump, generally designated 142, and having a suction pipe 144 leading from the previouslymentioned hydraulic uid reservoirA (not shown) to the suction side of the pump 142.

The outer ends of the valve operating arms 103 and 105 (FIGURE 1) are pivotally connected as at 146 and 148y (FIGURE l) toa reciprocatory operating or connecting rod 150 which inv turn is pivotally connected to the

armatures

152 and 154 of

solenoids

156 and 158 provided withv windings 160 and 162 respectively. The

armatures

152 and 154 and operating rod 150 are shown, for simplicity, as free fromconnecting links or similar mechanical devices which would compensate for the arc of swing of the pivot pins 146 and 148. The solenoid windings 168 and 162 at one end of each winding are connected by wires 164 and 166 to a first current supply line 168, whereas the-opposite ends of the solenoid windings 160 and 162 are connected by

wires

178 and 172 to one terminal each of switches 174 and 176 having swinging operating

arms

178 and 180 respectively equipped with

cam follower rollers

179 and 181 respectively. The remaining terminals of the switches 174 and 176 are connected by wires 182 and 184 to a second current supply line 186. The lirst and second current supply lines 168 and 186 are connected to an external source of electric current (not shown), -such as to the secondary winding of a step-down transformer (not shown), the primary winding of which is connected to conventional power current supply lines of higher voltage.

The

cam follower rollers

179 and 181 engage the periphery of a rotary valve timing cam 188 having a dwell portion190 and a raised portion 192. The latter successively engages and alternately operates the

arms

178 and 180 of the switches 174 and 176, thereby alternately energizing and de-energizing the solenoids 168 and 162 to shift the operating rod 158 in opposite directions as explained more fully below in connection with the operation of the invention. The cam 188 is keyed or otherwise drivingly secured to a shaft 194 (FIGURE l) to which is keyed or otherwise drivingly secured a worm wheel 196. Meshing with the worm wheel 196 is a worm 198 keyed or otherwise drivingly connected to the armature shaft 200 of an electric timing motor 282. The shafts 194 and 208 are journaled in conventional bearings (not shown) which are omitted to avoid lcomplicating the drawings. The switches 174 and 176 are preferably the so-called micro-switches and the motor 282 and cam 188 and their associated parts constitute a switch timing unit, generally designated 204.

The tilting furnace unit 40 is in the form of an approximately rectangular block structure of refractory blocks 206 (FIGURE l) forming the lower portion or substructure 208 of the furnace and cross blocks or slabs 210 forming the roof 212topped by insulating slabs 214. The substructure 208 is provided with an elongated central depression or recess 216 forming a reservoir for molten material, the recess 216 having a bottom surface or lloor 218 and inclined opposite end surfaces or

ramps

220 and 222. The entrance ramp 228 is preceded by a level horizontal inlet surface 224, whereas the exit ramp 222 is followed by a similar liat exit or discharge surface 226 followed by an inclined outlet surface 228. From FIGURES l and 3 it will be evident that the surfaces 224,

220, 218, 222, 226 and 228 collectively form a gui-def.

way for the rollable articles W, the surface 226 forming a hump between the two oppositely-

inclined ramps

222 and 228. The ceiling 210 is spaced abovethe floor 218; a sufficient distancel to provideV an elongated furnace cham,-

ber 230 with an inlet passageway 232 above the inlet surface 224 and an outlet passageway 234 above the outlet surface 226.

The inlet and

outlet passageways

232 and 234 are closed respectively by vertically-sliding

doors

236 and 238 operated to be raised and lowered by hand wheels 40 and 242 respectively through conventional mechanism (not shown). rl`he opposite sides of the furnace chamber 230 are closed by side walls 244 and 246 (FIGURE 2) composed of

refractory blocks

248 and 250 respectively spaced apart from one another a distance sufficient to conveniently handle the maximum length of workpiece W which is to be coated with molten material M inthe recess 216. Certain of the refractory blocks 248 are boredas at 252 to receive gas burners 254 interconnected by a manifold 256 which is capped at one end as at 258 and has its opposite end 268 connected to a suitable source of fuel gas (not shown). The furnace unit 40 is encased by a box-like housing or casing 262 of steel or other suitable ire-resisting material and the inlet and

outlet doors

236 and 238 are guided by

guide plates

264 and 266 spaced longitudinally away from but parallel to the end walls of the housing 262, so as to close the entrance and

discharge passageways

232 and 234 respectively.

The furnace 10 radjacent its

inlet passageway

2,32 is provided with an inlet platform 268 preceded by an inlet runway 270, and beyond its outlet passageway 2324 is also provided with a receiving platform 27.2 followed by a discharge. runway 274 (FIGURE 1). Arranged between the

platforms

272 and 274 is a conventional scraper, generally designated 276, the details of which are beyond the scope of the present invention and which removes excess molten coating material from the workpieces W and leaves them with the desired thickness of oxidationprotecting coating thereon. The floor 278 of the scraper 276 interconnects the

platforms

272 and 274. The platforms 268 and 272V are spaced slightly away from the [furnace end Iwalls of the housing 262 so as to provide clearance for the rocking or tilting of the molten material coating furnace during operation.

The moded tilting molten material coating furnace, generally designed 288, shown in FIGURE 3 has a tilting furnace unit 282 of similar construction to the tilting furnace unit `40, hence similar parts are similarly 'numbered with reference numerals. The furnace unit 282, however, is mounted upon a base structure 284 which is of I-beam construction and which is provided at its approximate mid-portion with an upper fulcrum bracket 286 which is pivotally connected to -a lower fulcrum bracket 288 by a fulcrum shaft 290, the lower fulcrum bracket 288 resting upon a bed 292 which in turn rests upon the floor or foundation 16. Secured to the underside of the base structure 284 near the opposite ends thereof are operating connection brackets 294 and 296 respectively carrying pivot pins or

shafts

298 and 300 to which the piston rods 50 and 52 of the hydraulic motors 86 and 88 (shown in FIGURE 1) are connected. The remainder of the apparatus below the bed 292 is similar to that shown in the lower half of FIGURE 1 and hence needs no further description. Upstanding stopr supports 302 and 304 are provided near the opposite ends of the base structure 284 and rest upon the bed 292, each being provided with a

stop screw

306 or 308 to adjustably limit the rocking action of the furnace unit 282.

In order to provide, where it is desired, for heating the workpieces or billets W prior to their entrance into the inlet passageway 232, the furnace unit 282 is provided with a recuperator 310 (FIGURE 3) which is in the form of a hollow vertical casing having an inlet opening 312 in the outer wall 314 thereof, the end wall of the housing 262 forming the inner end wall of the recuperator 3101, which has at the upper end thereof Va stack 316 with a heated-air discharge passageway 318 leading upwardly from the recuperator chamberv 320. A perforated platform 3221s mounted inthe recuperator chamber 320 enoteca Within the recuperator 310` and is supplied `with heat from the furnace chamber 230 through an` inclined supply passageway 324 (FIGURE 3). The furnace unit 282 is otherwise substantially similar to the furnace unit 40, except that the burners 326 are placed in bores '328 in the roof 212 and are directed downwardly as an. optional variation of the placing of the burners 254,V in horizontal positions, as shown in FIGURE 2.

The modified substructure 330 shown in fragmentary view in FIGURE 4 is similar in every respect to the substructure 2tlg of the furnace unit 40 shown in FIGURE l, with the exception of the fact that the bottom or floor 332 is provided at intervals with cross ribsridges or other transversely-disposed upward projections 334, thereby adapting the substructure 33t] of the furnace unit, generally designated `336, for the handling of workpieces V and U of non-circular cross-section. The workpieces V and U are shown to `be of hexagonal and square crosssection respectively but might be of any other noncircular cross-section which is not ordinarily rollable but which would normally slide along the furnaceiloor without becoming fully coated in response to tilting of the furnace, as explained below in the description of the operation of the invention. The cross ribs 334 break up the sliding action of the wonkpieces U and V which would otherwise occur during the tilting of the furnace unit 336, and cause them to tumble over the ribs or ridges 334 and thereby receive a coating of the molten material M on all sides thereof. p

In the operation of any form of the invention, the workpieces W of FIGURES l to 3 inclusive o1' the workpieces U and V of FIGURE 4 are preheated, if desired, either separately or in the recuperator 310 of FIGURE 3, so as to prevent their chilling and congealing the coating of molten glass or other molten materialcontained inthe recess 216 of the furnace unit 46, 2821er 336-respectively. If the workpieces are of circular cross-section so as to be fully rollable such as the Workpieces W in FIGURES l to 3 inclusive, after preheating they are either loaded into the furnace by suitable conventional tongs (not shown) or they :are rolled through and Ialong the entrance passageway 232 down the inlet ramp 22ilinto'the recess 216 where they become partly immersed in the `molten material M, such as molten glass, contained in the recess 216 and rendered molten and maintained in a molten condition by the iiames from the gas` lburnersZfi.

Meanwhile, the furnace unit 4G, 282er 332"isstarted to rock by starting the timing motor 202 of the timing unit 204 (FIGURE l), causingtlie cam 188 to rotate on its shaft 194 and alternately presenting the raised portion '192 thereof to the

follower rollers

179 and 181 of the microewitches 174 and 176 respectively. This action alternately opens and closes the circuit through the microswitches 174 and 176, thereby alternately energizing the solenoids 16S and 162 and, as a result, causing their

armatures

152 and 154 and the connecting rod 156 to be reciprocated. As the rod 150 moves to and fro, it swings` the

valve arms

103 and 105 likewise to and fro, rotating the valve cores or

valve members

162 and 164 of the hydraulic control valves 98 and 10i) to and fro and alternately subjecting the service ports 62, I64 and 66, 63 to the reception of pressure fluid from the pump 142. As a result, the piston rods 519 and S2 and their respective piston heads 54 and 56 move back and forth in timed relationship with one another, rocking the base 32 through the connection brackets 36 and 38 (FIGURE l) or 294 and 296 (FIGURE 3). In either case, the furnace et) or 282 tilts back and forth, the former upon its rollers 26 between its upper and lower races Btl and 18, the latter on its falcrum shaft 29).

As the furnaces 4l) and 282 rock to and fro, the Workpieces W roll back and forth along the floor 218 in the molten bath M, so that their side surfaces are coated with a thin layer of lmolten glass, molten silicate material or other coating such as borax, salt or ceramic material. Sufficient space is left between the number of workpieces W loaded into the recess 216- and the length of the bed` 218 to permit rolling space at the opposite ends thereof. When the articles have been adequately coated, they are either rolled up the discharge incline or ramp 216 to the discharge surface 226 and down the outlet surface 228 or are handled by suitable conventional tongs (not shown) for the same purpose. The discharge coated workpieces are placed on the slightly inclined` discharge platform 272 where they roll down upon the discharge runway 27'4` and are subjected to 4a scarping or excess coating removal operation forming no part of the present invention but` provided for the purpose of preventing an excessively thick layer of the coating material remaining on the workpieces W.

The operation of the furnace unit 332 of FIGURE 4 is generally similar to that` of the furnace units 40 and 282 `already described, with the exception of the fact that the Workpieces U or V of non-circular cross-section are caused to tumble after sliding short distances by reason of the presence of the ribs or ridges 330. In this manner, a coating of the molten material is applied on all sides of the workpieces U or V in the same way as described above for the rollable workpieces W.

While the invention has been described above in connection with the coating of steel billets, it will be obvious that billets of any material requiring or making use of such a protective coating may also be treated in the furnace of the present invention. It will also be evident that the floor 218 of the furnace should have end spaces of sufficient length to enable the billets to be rolled for a distance not less than` oneV or one and one-half times the circumference of the billets being treated, so that the entire circumference of the billet will be fully coated, without leaving any uncoated gaps. The: coating of protective material should be as thin as possible, in order to enable the heat to penetrate through it most rapidly and most eiiiciently to the billet inside the coating, yet 'at the same time protect the billet surface from oxidation. The molten coating of protective material causes a more rapid absorption of heat by the billet because the continuously reforming molten film transfers heat from the hot gases to the billet material at a more rapid rate than could be obtained without the coating. As stated above, in the `objects of the invention, the billets are only partially submerged in the molten glass or other coating material, so as to leave the major portion thereof exposed to the furnace heat and accomplish the most rapid heating of the billets.

Since large billets are very heavy, they are'` conveniently handled, put into the furnace and taken out of the furnace by means of tongs attached to a crane. The problem of loading and unloading the furnace of course varies with the size and weight of the billets being coated, so that positive loading and unloading is preferred with larger billets and also with smaller billets where the self-unloading discharge ramp is found to be impractical. For most installations, some mechanism has to be provided to remove the billet from the furnace, such mechanisms being wellknovvn to those skilled in the art of furnaces and heat treatment, and are beyond the scope of the present invention.

While the modified furnace 280 of FIGURE 3 is shown as provided with a recuperator or Vpre-heater 316) attached to and rocking with lthe furnace, such construction is not obligatory, particularly when treating large billets. Under such circumstances, it is preferred to mount the preheater 310 in a stationary manner separate from the furnace so as not to rock with the furnace. Where, as shown in FIGURE 3, the preheater 310 is mounted to rock with the furnace, the stack 316 for the exhaust gases is arranged so that it slides -up `and `down within a fixed stack, passing out of the building.

7 v What I claim is:

1. A molten` material coating furnace for rollable articles comprising a base, a furnace support Vrockably mounted on said base, mechanism for rocking said support alternately in opposite directions in timed relationship relatively to said base, and an elongated furnace structure mounted on'said support and rockable therewith, the rocking axis of said support being disposed transversely to the length of said furnace structure, said furnace structure having therein 'an elongated chamber with a rollable article entrance and with an elongated molten material receptacle extending from said entrance along said charnber in the direction of rocking of said furnace support, said furnace structure including a mainly-horizontal generally-rectilinear rollable article guideway extending through said chamber lengthwise of said furnace structure, and means for supplying heat to said chamber to render and maintain molten the coating material in said receptacle.

2. A molten material coating furnace, according to claim 1, wherein said furnace structure guideway includes a downwardly inclined entrance ramp having an inclinedplane rollable article pathway extending from said entrance downwardly to said receptacle.

3. A molten material coating furnace, according to claim 1, wherein said furnace chamber has an inclined entrance ramp having an inclined-plane rollable article pathway extending downwardly from said entrance to one end of said receptacle and lan upwardly inclined exit ramp having an inclined-plane rollable article pathway extending upwardly from the opposite end of said receptacle to said exit.

4. A molten material coating furnace, according to claim 1, wherein said receptacle consists of an elongated depression in the door of said chamber and wherein said depression has an elongated substantially horizontal oor forming the intermediate portion of said rollable article guide'way at the bottom of said depression and extending from end to end thereof.

5. A molten material coating furnace, according to claim 1, wherein said furnace structure guideway includes an upwardly inclined exit ramp having an inclined-plane rollable article pathway extending from said receptacle upwardly to said exit.

6. A molten material coating furnace, according to claim 5, wherein said exit has a downwardly inclined discharge Vramp having an inclined-plane rollable article pathway extending downwardly from approximately the upper end of said exit ramp and forming a hump in cooperation therewith.

7. A molten'materialicoating furnace, according to claim 1, wherein said heating means includes a multiplicity of gas-fired burners disposed transversely of and directed into said chamber at locations spaced apart from one another along the length of said furnace chamber.

8. A molten material coating furnace, according to' claim 1, wherein said support rocking mechanism includes a fulcrum shaft supporting structure disposed between said support and said base and a fulcrum shaft mounted in said fulcrum shaft supporting structure with its pivot axis disposed transversely to the length of said furnace structure. A

9. A molten material coating furnace, according to claim l, wherein said receptacle has a floor therein with a multiplicity of transversely-disposed ridges disposed approximately parallel to the rocking axis of said support and spaced longitudinally apart from one anotherV along said hoor in the direction of rocking of said furnace structure and disposed transversely to said rollable article guideway.

10. A molten material coating furnace for rollable articles comprising a base, a furnace support rockably mounted on said base, mechanism for rocking said support relatively to said base, and a furnace structure mounted on said support and rockable therewith, said furnace structure having therein an elongated chamber with a rollable article entrance and with an elongated molten material receptacle extending from said entrance along said chamber in the direct-ion of rocking of said furnace support, and means for supplying heat to said chamber to render and maintain molten the coating material in said-receptacle, said rocking means including a reciprocatory fluid pressure motor having a cylinder element and a piston element reciprocable in said cylinder element, one of said elements being connected to said furnace support and the other element being connected to said base.

11. A molten material coating furnace, according to claim 10, wherein a uid pressure supply and control circuit is connected to said motor for reciprocating said piston element lin said cylinder element.

References Cited in the tile of this patent UNITED STATES PATENTS 2,036,902 Warlimont Apr. 7, 1936 2,346,442 McFeaters Apr. 11, 1944 2,700,624 Wagner et al Jan. 25, 1955 2,707,629 Kennedy May 3, 1955 2,832,700 Balestra Apr. 29, 1958