US3215418A

US3215418A - Heating apparatus

Info

Publication number: US3215418A
Application number: US144923A
Authority: US
Inventors: Jr John J Fannon
Original assignee: Hupp Corp
Current assignee: Hupp Corp
Priority date: 1961-10-13
Filing date: 1961-10-13
Publication date: 1965-11-02
Anticipated expiration: 1982-11-02

Description

Nov. 2, 1965 .1.1. FANNON, JR 3,215,418

Y l HEATING APPARATUS Filed oct. 15, 1961 2 sheets-sheet 1 Wn I T; I* O ii ATTORN EY Nov. 2, 1965 J. J. FANNON, JR 3,215,418

HEATING APPARATUS Filed Oct. 13, 1961 2 Sheets-Sheet 2 l Ihl/ INVENTOR John J. Fonnon,Jr.

ATTORNEY 6 United States Patent O 3,215,418 HEATING APPARATUS John J. Fannon, Jr., Grosse Pointe Park, Mich., assignor to Hupp Corporation, Cleveland, Ohio, a corporation of Ohio Filed Oct. 13, 1961, Ser. No. 144,923 4 Claims. (Cl. 263-8) The present invention relates to ovens, components thereof and more particularly to ovens and heating apparat-us for drying and curing fluid finishes or coatings applied to a base material which will be Iheated upon irradiation by infrared radiation. As used in this specification and the appended claims a fluid finish or coating means a material which contains a liquid and a residue which is applied to a surface of a .base material, usually metallic, with the residue either in solution or suspension in the liquid and from which the liquid may be volatilized by heating to leave the residue fixed to the surface of the base. While the drying of certain fluid nishes involves merely removal of the solvent and in all cases removal of the solvent is a major factor, it is only part of the process in paint baking. Most coatings are converted from liquid to solid partly by evaporation of solvent and partly fby a chemical reaction, such as polymerization or oxidation which takes place at high temperatures or is accelerated by heat. Therefore, the function of the oven is not only to remove the solvent, but to heat the coating to such a temperature as is required to cure the finish, and t0 maintain this temperature long enough for the necessary curing reaction to take place. The actual temperature required at the Work piece surface for optimum results depends on the composition of the coating, but for most organic finishes is in the range of 300 F. to 600 F. Too low a temperature at the work piece either prolongs the baking time required or results in a soft coat. Too high a temperature may burn off the finish or cause it to .be brittle or peeloff. A coated work piece as used herein means an article to which a fluid finish or coating has been applied to one or more entire surfaces thereof or to any portion or portions of said surface, as for example for protective, decorative and/or informative purposes and, depending upon the context may refer to such a work piece either before or after the liquid has been removed and the residue cured by heat. A Work piece may -be either a member of predetermined dimensions such as a sheet or of indefinite dimensions such as a strip fed from a roll.

It has been found that infrared radiant energy from high temperature sources impinging directly on the coated parts is a most effective and efficient means for baking various types of finishes, and, for high production, the heat concentration (B ttu. per square foot) must be kept as high as possible. Very high concentrations can be obtained by using gas-fired infrared generators. Electrically -generated infrared being of the near short WaveV vtype is reflected as a lighting and does not penetrate beyond the reflective surface of the -uncured coating. Gas generated infrared is immediately converted to heat at the instant of impingement upon the coating with little or noV reflection, due Vto the fact that gas infrared is of the far infrared of long wave length which is particularly effective to become absorbed at a high rate rather than reflected by the highly reflective moisture presenting surface of the uncured coating. From the viewpoint of long life of the generators, it has been found that gas burning infrared generators utilizing the principles described in United States Patent No. 2,775,294issued December 25, 1956 to Gunther Schwank, particularly with the improvements and modifications as described in my co-pending application Serial No. 50,421 filed August -1 8, 1960 for Heating Apparatus and Method, produce excellent results.

When sheets or strips of metal coated with fluid finish 3,215,418 Patented Nov. 2, 1965 ice containing solvents are passed through the infrared beams emitted by a series of such infrared generators, arranged so that their radiation beam is directed toward the coated surface, heat will be transferred to the coated surface very efliciently. The basic problem is that of removal of the solvent vapors While heating the Workpieces rapidly to la suitable temperature to cune the finish properly in a mini-Y mum length of time. While the apparatus and method of my aforesaid co-pending application produces a very good solution to this problem, a large volume of air is required to evacuate the volatiles and the energy potentially availf able in the combustible volatiles of the coating is not utilized.

Contrary to thel principles of the invention of my aforesaid co-pending application, the present invention contemplates the provision of a substantially oxygen free atmospheric blanket overlying the coated work pieces while they are irradiated through the blanket to cure their coating. This blanket is most easily and effectively achieved in accord with this invention by positioning the gas burning infrared generator banks closely adjacent, in the order of two to three inches, the path of work piece movement through the oven and providing a sub-atmospheric pressure fat the sides of the bank of generators. With this arrange ment, the products of combustion of the generators ilovv over the surface of the work pieces toward the sides of the generator bank and form a substantially oxygen free blanket over the work pieces. When such a blanket is formed the combustible volatiles in the Work piece coating, upon evaporation, immediately enter the substantially oxygen free blanket. These volatilized particles have a relatively high velocity in `the direction nornal to the coated work piece surface, that is toward the radiant Wall of the generator bank. The particles of the products of combustion forming the substantially oxygen free blanket have a relatively low velocity in a path generally parallel to the Work piecev coated surface. As a result, the volatile particles are prevented from igniting adjacent the Work piece coated surface and pass through the blanket toward the radiant Wall of the generator bank. The generator bank is supplied with an amount of primary air slightly in excess of that required for complete combstion of the gaseous fuel. As a result, when the combustible volatiles approach the radiant wall of the generator bank, they ignite and combine with the slightly excess oxygen in the primary air. The burning volatiles in this ymanner produces vadditional infrared radiation which in part is directed directly toward the work piece and in part toward the radiant Wall of the generator bank. This burning of the vola'- tiles thus increases the normal operating temperature of the generator bank radiant Wall,- improves its efliciency and augments the radiation from it tovvard the Work pieces thus increasing the overall efliciency of the oven and eliminating the combustible volatiles as an explosive hazard.

The primary object of the' present invention is to provide an improved apparatus for curing coated work pieces by which the coated Work pieces IareY blanketd with a substantially oxygen free atmosphere While subjected to infrared irradiation to heat the work piece and its coating to the curing temperature of the coating to prevent igniti'on of the combustible volatiles in the coating at the coated Work piece surface during the coating curing and by which the combustible volatiles are burned under controlled conditions in a position to augment the heating effect of the source of infrared radiation.

l More particularly it is an object of this invention to provide an improved apparatus for curing coated work pieces in which the coated work piece is irradiated with infrared radiation from a gas burning infrared generator through a substantially oxygen free workpiece blanketing atmosphere composed of the products of combustion from such generator.

A further object of this invention is to provide an improved method of and apparatus for curing coated work pices by infrared irradiation of the work pieces from a gas burning infrared generator source in which combustion of the combustible volatiles in the coating is precluded adjacent the work piece by a blanketing substantially oxygen free atmosphere composed of combustion products from the infrared source and is effected adjacent the infrared source t augment the heating action of such source.

A further object of this invention is to provide an im- Iproved -apparatus for curing work piece coatings by infrared irradiation in which the work piece is blanketed by a substantially oxygen free atmosphere during its radiation to preclude combustion of the combustible volatiles in the coating adjacent the work piece coated surface.

A further object of this invention is to provide an irnproved apparatus for and method of curing work piece coatings by infrared irradiation in which the combustible coating solvents are burned in a position to provide infrared radiant energy for heating of the work pieces to thereby increase efficiency and eliminate the hazard of explosion of the combustible volatiles.

A further object of this invention is to provide apparatus for drying coated work pieces by irradiation with infrared radiation from a source at a temperature in the order of 1650 F. to 2300 F. through an atmosphere having a sufficiently low oxygen content that ignition of volatilized solvents close to the work pieces is precluded.

More specifically, it is an object of this invention to provide a gas burning infrared generator type drying apparatu-s of improved construction wherein cooling air is evacuated from the apparatus over the generator housing structure to thereby cool said structure and wherein products of combustion are evacuated from between the generators and the work pieces to thereby maintain a low oxygen atmosphere therebetween.

A further important object of this invention is to provide an improved gas burning infrared generator equipped drying oven in which the radiant face of the radiant generators is located a distance from the work pieces such that a low oxygen atmosphere is maintained therebetween whereby combustion of volatiles will take place only at said radiant face.

A further object of this invention is to provide a drying oven apparatus wherein radiant generators of the tile type 'are so located relative to a conveyor carrying work pieces therethrough that an atmosphere is established and maintained adjacent the work pieces of suiiiciently low oxygen content to preclude combustion of volatiles and wherein a pre-mixed gaseous fuel is supplied to said radiant generators which contains sufficient oxygen to completely burn the fuel which is supplied thereto and containing only suicient excess oxygen to effect complete combustion of the volatilized solvents released from the work pieces as such volatiles approach the radiant faces of the generator.

These and other objects of this invention will become more fully apparent by reference to the appended claims and as the following detailed description proceeds in reference to the accompanying drawings wherein:

FIGURE 1 is a side elevational view, partially in section, of an oven embodying and operable in accord with the principles of the present invention;

FIGURE 2 is a top plan View of the 4oven of FIGURE A1; and

FIGURE 3 is a sectional view substantially along the line 3-3 of FIGURE 1.

Referring now to the drawings in detail and particularly to FIGURES 1 and 2I the oven 10 :of the present in- Avention comprises -a longitudinal elongated housing 12 having four sections 14, 16, 18 and 20 arranged in end to end relation. Work pieces, usually in the form of flat sheets, are fed through the open sections 14, 16, 18 and 20 by a conveyor 22 comprising a plurality of heat re- Cil sistant cables 24 extending in a continuous path defined by

guide rollers

26, 28, 30 and 32 fixed to the

shafts

34, 36, 38 and 40 respectively. One of the shafts 34-40, such as shaft 38, is motor driven by a motor (not shown) to cause the cables 24 to continuously feed about the rollers 26-32. The work pieces to be fed through the oven 10 are placed on the inlet end -of the conveyor 22 above the rollers 26 manually or by any suitable automatic means and are fed along the forward run of the conveyor 22 between

rollers

26 and 28 to the discharge end of the conveyor 22 above rollers 28 from which they are removed by suitable means such as a further conveyor.

Disposed within each of the housing sections 14, 16, 18 and 20 above the forward runner of the conveyor 22 between the

rollers

26 and 28 is a bank of gas burning infrared generators 42. Each bank of infrared generators preferably comprises twenty longitudinally extending parallel rows of infrared generators 44, there being preferably three infrared generators in each row in each section of the housing. The generators 44 of the central fourteen rows in each :section are supplied with premixed gaseous fuel and air sufficient for complete combustion of the gaseous fuel through a common manifold structure such as indicated at 46 in FIGURE 3, the three front rows of infrared generators of all four housing sections 1420 are preferably fed through a common manifold structure such as indicated at 48 and the three rearmost rows of infrared generators 44 are preferably fed from a common manifold such as indicated at 50 for all four sections of the housing, as is fully disclosed and described in my aforesaid co-pending application.

As is best shown in FIGURE 3, the housing sections 14-20 each comprise a plurality of metallic uprights 52 each of channel shape cross section interconnected by longitudinally extending

metallic frame members

54, 56, 58 and 60 each of channel shape cross section and by transversely extending frame members (not shown). The sides of the housing sections are closed by sheet

metal cover plates

62 and 64 secured to the uprights 52.

The infrared generators 44, which as indicated above are preferably of one of they improved reected heat resistant constructions disclosed in my aforesaid co-pending application, are mounted within -a frame structure 66 which is supported by transversely extending support bars 68 which in turn are adjustably suspended by tie bolts 70 from the longitudinally extending channel shaped

frame members

58 and 60. The bolts 70 are adjusted so that the radiant bottom wall 72 defined by the coplanar radiant faces of the infrared generators 44 is parallel to the top surface of conveyor 22 and spaced from the top coated surface 74 of the coated Work pieces 76 carried by conveyor 22 a dist-ance in the order of two to three inches. Each of the banks of generators thus produces a generally rectangular downwardly directed beam of infrared radiation which is intercepted by the work pieces as they are 'moved by the conveyor through the oven 10.

By this arrangement, the products of combustion of the infrared generators 44 form a substantially oxygen free blanket over the top surface 74 of the work pieces 76 so that the combustible volatiles in the coating of the work piece 76 cannot ignite adjacent the top surface 74 of the work piece 76 but must pass through that substantially oxygen free atmospheric blanket to a position substantially adjacent or in contact with the bottom radiant wall 72 of the infrared generator bank before ,being ignited. For this purpose, as indicated above, the

Since a relatively low amount of volatile will be released in housing section 14 and a maximum amount of volatile will be released in one of the other housing sections, section 18 for example, the amount of excess air pre-mixed with the gaseous fuel of each of the generator banks in these housing sections must be controlled accordingly.

The incombustible products of combustion are evacuated in an air stream indicated by the arrows 78 flowing from atmosphere through the

inlet ports

80 and 82 formed through the

housing side walls

62 and 64, upwardly around each side of the generator bank between the support members 78 into -an exhaust manifold 84 extending over the entire length of all four housing sections 14, 16 18 and 20 and from which uid ow is established through an outlet conduit 86 by an exhaust blower 88 powered by a suitable electric motor 90 shown in FIGURE 2.

As is illustrated in FIGURE 1, pivotally

adjustable batiies

92, 94, 96 and 98 are provided within the exhaust manifold 84 to control the relative amount of air flowing through the

inlet parts

80 and 82 of the housing sections 14-20. This is essential to accommodate the varying amounts of volatiles which are released from the coating in each of the housing sections 14-20.

The radiant wall 72 dened by the radiant faces of generators 44 are of sufficient width transversely of the direction of movement of the work pieces that the beams of infrared radiant energy emitted therefrom are substantially equal to or greater than the m-aximum Width of the work pieces transversely of their direction of movement and are located directly above the path of work piece movement so that as a work piece 76 moves beneath the generators 44, the work piece 76 successively intercepts and is irradiated by the beams from the generator banks over its entire top surface exposed to the generators 44. The intensity of irradiation of the work pieces 76 and the energy absorbed by the work pieces 76 is sufficient to heat them to a temperature at which the liquid solvent in the coating will volatilize and the fluid finish applied to the surface of the work pieces and exposed to the radiant faces of the generators 44 will be cured. As explained above, the solvents used in the uid finishes which will normally be dried in this oven are highly combustible. As a cold work piece 76 passes beneath each generator bank it will be gradually heated. Initially little or no solvent will be vaporized. As the work piece 76 passes successively beneath each bank of generators in line, it will reach a temperature at which there is a maximum solvent vaporization. While the temper-ature of the Work piece will continue to increase so long as it is subjected to irradiation, the amount of solvent being vaporized will gradually decrease from the maximum until, as the work piece passes from the beam of the last generator bank in line, it is perfectly dry and its coating completely cured and no further solvent volatilization occurs. As the work piece 76 passes under the successive banks of generators 44 the ignition temperature of the volatilized solvent will be reached, in accordance with this invention by positioning the radiant faces of generators 44 but two to three inches from the forward one of conveyor 22 between

rollers

26 and 28 and by providing exhaust blower 88 which not only removes the products of combustion (CO and CO2) from Vthe heating area, but also prevents secondary air from communicating with the generators 44, a low oxygen atmospheric condition will exist between the radiant Wall 72 defined by generators 44 and the coated surface 74 of work pieces 76 carried by the endless conveyor 22. Therefore, because of this low or substantially oxygen free atmosphere, combustion of the combustible volatiles cannot be supported close to the work pieces. The volatilized combustible solvent rises through this low oxygen atmosphere until it 4reaches the radiant wall 72 defined by the generators 44 and at that point it comes in Contact with the excess oxygen in premixed gaseous fuel and air which has sufficient oxygen to Vsupport combustion of the volatilized solvents as well as the fuel at the face of the radiant generators 44. The solvent thus, in effect, adds fuel to the combustion process and in effect sustains and aids the irradiation effect of the radiant generators. The positioning of the tile faces in closely spaced relationship to the work pieces prevents external secondary air from entering into the combustion process so that the excess oxygen in the pre-mixed gaseous fuel and air is substantially the only source of oxidizing agent available to the combustible material. The exhaust blower 88 performs the function of withdrawing the products of combustion CO and CO2 from the work area of the drying apparatus. Because of the suction effect of the exhaust blower 88, the inlets and 82 do not provide additional oxygen for the combustion process. The total amount of pre-mixed fuel and air supplied to each radiant generator input manifold such as 46, 48 and 50 can be controlled by appropriate control valves. By properly regulating the baffles 92 and the pre-mixed fuel and air control valves, the amount of products of combustion which result from the combustion of the volatiles released from the work pieces as well as that lwhich results from combination of the pre-mixed fuel which products of combustion are evacuated from each section of heating area can be regulated so that all of the products of combustion will be uniformly evacuated from each section of heating area.

From the foregoing it will be readily apparent to one skilled in the art that this invention provides infrared generators to cure the coating of coated work pieces which utilize the reflective properties of the work pieces to aid in the drying and curing the work piece coatings and additionally utilize the volatiles released from the work pieces as additional fuel for the radiant generators while eliminating the explosion hazard. 'Ilhese attributes of the present invention are particularly important because they permit a more eicient operation of radiant heat generators in ovens of this type than that which has heretofore been attainable.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristic thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. Apparatus for curing the coating of coated work pieces comprising a housing, an endless work piece support conveyor extending longitudinally through said housing, said housing having air inlet openings at each side of said conveyor to admit cooling air into said housing, at least one bank of gas burning infrared generators, means supporting said generator lbank in said housing above said endless conveyor in a position to irradiate work pieces carried by said conveyor, an outlet manifold in said housing disposed above said generators and forming a top closure for said housing, means for inducing flow of cooling air into said housing through said inlet openings upwardly along the side of said conveyor and said radiant generators bank and into said outlet manifold over the top of s-aid generator bank supporting means and out to atmosphere to thereby cool said apparatus and evacuate the combustion products from the space between said generator bank and said conveyor without supplying air to said space.

2. The apparatus of claim 1 wherein said generator bank has a radiant wall spaced from said conveyor a distance in the order of but two to three inches.

3. The apparatus of claim 1 together with at least one adjustable baffle in said outlet manifold for controlling 7 8 the distribution along said housing of the cooling air ad- 2,210,032 8/40 Hess 101--416 mitted thereinto. 2,220,928 11/40 Kienle et al 263-52 4. The apparatus of claim 3, wherein said housing is 2,268,987 1/ 42 Hess etal 34-23 X comprised of a plurality of sections and there are ad- 2,388,762 11/45 Powers 263-8 justable baes for controlling the admission of cooling 5 2,884,705 5/59 Flynn 117-46 X air into each of said housing sections. 3,015,479 1/ 62 Edberg et al 263-8 3,056,382 10/62 Glaser et al 117-46 References Cited by the Examiner UNITED STATES PATENTS CHARLES SUKALO, Primary Examiner. 793,365 V3/'05 Rupley 117 46 10 FREDERICK L. MATTESON, JR., JOHN I. CAMBY',

2,03 5,746 3/36 Hall 263-8 Examiners. T

Claims

1. APPARATUS FOR CURING THE COATING OF COATED WORK PIECES COMPRISING A HOUSING, AN ENDLESS WORK PIECE SUPPORT CONVEYOR EXTENDING LONGITUDINALLY THROUGH SAID HOUSING, SAID HOUSING HAVING AIR INLET OPENINGS AT EACH SIDE OF SAID CONVEYOR TO ADMIT COOLING AIR INTO SAID HOUSING, AT LEAST ONE BANK OF GAS BURNING INFRARED GENERATORS, MEANS SUPPORTING SAID GENERATOR BANK IN SAID HOUSING ABOVE SAID ENDLESS CONVEYOR IN A POSITION TO IRRADIATE WORK PIECES CARRIED BY SAID CONVEYOR, AN OUTLET MANIFOLD IN SAID HOUSING DISPOSED ABOVE SAID GENERATORS AND FORMING A TOP CLOSURE FOR SAID HOUSING, MEANS FOR INDUCING FLOW OF COOLING AIR INTO SAID HOUSING THROUGH SAID INLET OPENINGS UPWARDLY ALONG THE SIDE OF SAID CONVEYOR AND SAID RADIANT GENERATORS BANK AND INTO SAID OUTLET MANIFOLD OVER THE TOP OF SAID GENERATOR BANK SUPPORTING MEANS AND OUT TO ATMOSPHERE TO THEREBY COOL SAID APPARATUS AND EVACUATE THE COMBUSTION PRODUCTS FROM THE SPACE BETWEEN SAID GENERATOR BANK AND SAID CONVEYOR WITHOUT SUPPLYING AIR TO SAID SPACE.