US2493754A - Apparatus for coating sheet metal articles - Google Patents

Description

Jan. 10, 1950 M. l. DoRFAN 2,493,754

APPARATUS FOR COATING SHEET METAL ARTICLES Original Filed June 2, 1943 ZSheets-Sheet 1 MJ? l.

I l l l l INVENTOR '(702 ro/v l. Do/eFQ/v.

BWM

Jan. l0, 1950 M. DORFAN APPARATUS Foa coATING SHEET METAL ARTICLES 2 Sheets-Sheet 2 Original FiledV June 2, 1943 INVENTOR Molero/v I. Dole/CHN,

"ATTORNEY Piuma Ju. 10,1950

APPARATUS FOR OOATING SHEET METAL ARTICLES Morton I. Dorian; Pittsburgh, Pa., assignor to Koppen Company, Ine., Pittsburgh, Pa., a oorpontion o! Pennsylvania AOrig-Inni application June 2, 1943, Serial No. 489,347. Divided and this application June 4,

1945, Serial No. 597,418

9 Claims.

The invention relates to the coating of articles or structures with materials which have quick air-hardening characteristics, as for example, bituminous base materials and some forms of paints, enamels and lacquers. The articles or structures may, for example, be plain or corrugated sheet metal such as used for rooting and siding, and valleys, gutters and the like formed of sheet metal, and pipes and structural shapes; and when the coating materials are those having bituminous bases, they may be coal tar and other pitches, asphalt and the like, either alone or mixed with each other, and preferably including suitable modifying plasticizers. -.\`Although not so limited in all of its aspects,

the invention will be described in its applica-y bility to the coating of sheet-like articles with heated bituminous base materials.

In providing such articles with such coatings it is diflicult rapidly and economically to form the coating of uniform thickness throughout, which it is highly desirable to do. Not only is there an economic waste of the coating material which covers a portion of an article in excess of the desired minimum coating thickness, but a substantial excess thickness of coating over portions of articles is attended by objectionable results in the use of the articles. For example, when such coated articles are subjected in use to abnormal high temperatures, the excessthickness portions of the coatings may objectionably flow, and when subjected to abnormal low temperatures they may crack. Also, variations in the thickness of coating may result in objectionable variations in the appearance of coated articles, and, when several sheets are overlapped at points of their connection to each other or to a supporting structural element, difficulties arise in making the connections when the coatings are too thick.

The object of this invention is to provide an apparatus for coating articles of the character explained with a bituminous base material, whereby the coating will be of substantially uniform thickness throughout the entire coated surface thereof, and whereby the coating operation may be effected rapidly and economically.

In the practice of the invention in its applicability to the coating of sheet metal with a bituminous base material, sheets of steel are lmmersed in a bath of coating material which is heated to a liquid state in a container. The sheets are maintained in the bath until they are heated to a substantially uniform temperature from the -top to the bottom thereof, preferably the temperature of the bath, and thereafter they 2 are slowly elevated from the coating material at a gradually decelerated rate of movement which is varied according to the coating material and the desired thickness of coating.

vAbove the heated bath of coating material the temperature of the radiant and air-convected heat thereof, into which the sheets or other arti- 1 cles are withdrawn and to which they are subjected, gradually diminishes upwardly, and the upper portions of the sheets are exposed tojsuch heat for a longer time than are theirlower portions. I have found that by gradually decelerating the rate of withdrawal of the sheets the excess coating material adhering to their upper portions Hows downwardly on the surfaces of the sheets and into the bath of coating material I in such a manner that the coating adhering to -the sheets is of substantially uniform thickness throughout. The gradually decelerating rate of movement, the gradually decreasing temperature of the atmosphere into which the sheets are withdrawn from the bath and the gradual hardening of the coating on the sheets as they rise above the bath are the factors which are coordinated and which cooperate to produce a uniform thickness of coating throughout.

To coat the sheets or other articles,'they are preferably positioned vertically in a pair of dipping racks which are suspended above a coating tank. Provision is made for elevating onerack from the tank while another is simultaneously lowered into it, and, while the articles on the loaded rack are held in the heated coating material to cause them to be heated to a substantially luniform temperaturefrom the top to the bottom thereof, coated articles are removed from the elevated rack and uncoated articles placed on it for the subsequent cycle of operation.

The invention will be further explained with reference to the accompanying drawings which diagrammatically illustrate the preferred form of apparatus for practicing it, and which is nowin commercial use. In the drawings Fig. 1 is a vertical sectional view through a coating tank and heater showing one rack positioned in the tank and another above it, combined with an elevation of mechanism for elevating and lowering the racks; Fig. 2 a plan view of the apparatus shown in Fig. l; and Fig. 3 an enlarged front view of a suspension pulley for the racks.

As shown particularly in Fig. 1, a body of coating material I is placed in a tank 2 which may be formed of steel and is surrounded by a. casing 3 which is spaced from the sides and b0twam tom ci' the tank to form vertical andhorisontal passages for the flow of gases for heatingthe coating .material and maintaining it at the deaired temperature. Near the top of the tank andcasing there are conduits l and 5 i'or receiving and discharging heating gases.A The preferred form of the heating apparatus is disclosed in my Patent No. 2,365,336, issued DecemberlB, 1944, to

which reference may be made for further details of its construction and operation. To circulate l the heated coating material and thereby facilitate' its maintenance at a substantially uniform porting plain or corrugated sheets Il in verticalV position suitably spaced laterally from each other to permit ready contact of their surfaces with coating'material. The preferred form of rack is shown in detail in my Patent No. 2,344,855,

issued March 21, 1944, to which reference may be made.

For lowering a loaded rack into the tankof coating material and for simultaneously elevatingl the other rack from it at a gradually decelerated rate of movement, cables I2 and I3 are preferably attached at their upper ends to the larger diameter portions of conical drums I 5 and I6, respectively, which are attached to and adapted to be rotated by a horizontal drive shaft I1. The

face of each of these drums is provided with a spiral groove for receiving the cable that is attached to the drum, the spiral being in opposite directions when the drums are positioned as it will move vertically and have no lateral movevnient such as would take place if its supporting cable extended directly downwardly from the drum, each cable extends over an idler pulley spaced horizontally from the drum and suspended by a short iiexible member 2l 4which serves as a swivel to permit the yoke 22 of the idler to rotate on a vertical axis. The upper end of each swivel member 2l may be attached to a frame 23 .positioned at oneside of each drum. Shaft I1 may be driven by a constant'speed motor 25 through a speed changer 26 whose driven element may be connected to the shaft I1 by a belt or chain 21.

By way of example, but not of limitation, I will explain in detail the procedure whic I have ble for providing corrugated sheet steel of 22 United States standard gauge and twelve feet in length with a plasticized coating of pitch, the coating being of substantially uniform thickness throughout the length of the sheets. The coating material used is what is commonly known as water gas pitch to which there is added a suitable modifying plasticizer. This coating material is heated to a temperature of about 375 F., at which it is maintained. The sheets being loaded in racks lIl and I I in the manner explained above, each,

rack is maintained in its lower position so that the sheets are totally immersed in the bath of coating material for about four minutes. Thereafter, the rack containing the immersed sheets is'withdrawn at a gradually decelerated rate of movement, the deceleration being from an initial rate of fteen feetto ailnal'rateofonefoct per minute.

I have found that the decelerated rate of vanand accordingly drums I5 and Itare conical, as shown, and rotated at a uniform .angular velocity. To similarly coat shorter'sheets ofthe ma- Ierial stated above, I have foundthat the nal rate of withdrawal should be approximately one foot per minute and that the initial rate should be vsubstantially that 'given in the following table:

hol

Lengt Initialspeed sheatinleet l5 inieet mimper The rate of 'withdrawal may be varied by speed changer 26 which is preferably driven by a synchronousuniform speed motor.

The example of coating procedure explained above is that used for sheets intended for service in a temperate zone. are to be used in hotter climates, less modifying plasticizer should be added to the coating material, and if they are to be used in colder climates more modifying plasticizer should be added.

From the data given in the example the coating According to the provisions ofthe patent statutes, I have explained the principle and mode of operation of my invention, and have illustrated and described what I now consider to beshown, but of the same pitch. yProperly to position each rack so that when lowered and elevated l. Apparatus for coating sheet-like articles with a substantially uniform thickness layer of v a bituminous base material comprising: a tank for containing the coating material, means for heating the coating material in the tank to a liquid state, a dipping rack arranged for supporting sheets in upright position, and a poweroperated means to move the rack into and out of the tank, the mechanism of the rack-elevating means being arranged for elevating'the rack at a gradually decelerated rate of movement. Q i

2. An apparatus for coating sheet-like articles with a substantially uniform thickness layer of a bituminous base comprising: a tank for containing the coated material, means for heating the coating material in the tank to a liquid state, a dipping rack arranged for supporting sheets in upright position, means `to move the rack into and out of the tank, rotary driven means for elevating the rack arranged to provide a decelerated rate of movement to withdraw the rack rom the tank and a speed changing gear on th driving means for varying the decelerated ra of movement.

drawal may be uniform'from beginningm and.'

and the thickness ,sosgrss 3. Apparatus for coating sheet-like articles with a substantially uniform thickness layer oi' bituminous base material comprising: a -tank for containing the coating material, means for heating the coating material in the tank to a liquid state, means for mixing the liquid to maintain a uniform temperature of the liquid in the tank, a dipping rack arranged for supporting sheets in upright position, power-operated means to move, the rack into and out of the tank, the mechanism of the rack-elevating means being arranged for elevating the rack at a' gradually decelerated rate of movement. v

4. Apparatus for coating sheet-like articles with a substantialLv uniform thickness layer of a quick air-hardening material, comprising a tank for containing the.coating material, a pair of A dipping racks suspended above said tank for receiving said articles in'vertical position, means for elevating a loaded rack from the tank at a decelerated rate of movement and for simultaneously lowering the other rack into the tank, and means for variably controlling the rate of elevating and lowering said racks.

'5. The apparatus combination deiined in claim 4 in which a heating means is applied to the alternately lowered into and elevated from said tank for heating material therein and circulating means are mounted on the tank to maintain the liquid in the tank at `a uniform temperature.

6. Apparatus for coating sheet-like arti-cles with a substantially ,uniform thickness layer of a bituminous basematerial, comprising a tank for containing the coating material, means for heating the coating material in the tank to a liquid state; a pair of dipping racks suspended above said tank for receiving said articles in vertical position, and means for elevating a loaded rack from the tank at a decelerated rate of movement and for simultaneously lowering the ,otherrackintothetank ing said articles in a vertical'position, a pair of substantially conical winding drums, a pair of cables, one end of each cable being attached tank, the elevation of each rack being'at a decelerated ratev of movement.

8. Apparatus for coating sheet-like articles with a substantially uniform thickness layer of a bituminous base material, comprising a tank for containing the coating material, means for heating the coating material in the tank to a liquid state, a pair of dipping racks for receiving said .articles in a vertical position, one of ther racks being within and the other being withdrawn from said tank, a horizontal shaft above said tank and lprovided with a pair of conical winding drums, a pair of cables attached at their upper ends'one to the larger diameter end of each of said drums and one to each of said racks, and means for driving said shaft lto rotate said drums to simultaneously move both of said racks whereby the racks are alternately lowered into and elevated from said tank, thel elevation of each rack being at a decelerated rate of movement.

4 9. An apparatus for coating sheet-like articles with a substantially uniform thicknessV layer of a bituminous base material comprising:

-a tank for containing the material; means for a decelerated rate of movement.

to the larger diameter end of each of said drums and the other endof each .to one oi.' said racks.I

andmeansforrotatingsaiddrumstosimmtansouslymovesaidrackswherebytheracksare MoRToN 1.

REFERENCES crrsn The following references are of record in the.

ille of this patent: y

. UNITED STATES PATENTS :mais

`Ciordon............ Sept. 2, 19M.4

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