US2845720A - Oven duct and duct inlet means - Google Patents

Description

Aug. 5, 1958 D. J. LOWE OVEN DUCT AND DUCT INLET MEANS 4 Sheets-Sheet 1 Filed July 13, 1955 INVENTOR. DONALD J. L0 WE AT ORNEYS- h 5, 1958 D. J. LOWE OVEN DUCT AND DUCT INLET MEANS 4 Sheets-Sheet 2 'Filed July 15, 1955 INVENTOR, DOA/ALB J. LOWE LWJMIL ATTORNEYS.

Aug. 5, 1958 D. J. LowE OVEN DUCT AND DUCT INLET MEANS Filed July 13, 1955 I 18 26 I I IIIIIIIIIIIIIIIIIIII lllllllllfll,I Il1IIlllllllllflllllllllllll llI! 4 Sheets-Sheet 5 INVENTOR. DONALD J. LOWE BY 7 MY KM ATTO/ZA/EYJ- g- 5, 1958 I D. J. L-OWE 2,845,720

OVEN DUCT AND DUCT INLET MEANS Filed July 13, 1955 INVENTOR. DONALD J. LOWE By. M v AT' QNEXS 4 Sheets-Sheet 4 OVEN DUCT AND DUCT INLET MEANS Donald James Lowe, Northfieid Center, Ohio, assignor to Young Brothers Company, Cleveland, Ohio, a corporation of Michigan Application July 13, 1955, Serial No. 521,662

8 Claims. (Ql. 34-150) This invention relates as indicated to a novel oven duct, and more particularly to a duct inlet for introducing hot gases to a heat processing oven having a wicket type conveyor extending therethrough.

Wicket type conveyors for drying lithographed metal sheets, for example, are well known in the art, one form being illustrated and described in Patent No. 2,668,366 to C. A. Barnett, Heat Processing Apparatus. Wicket type conveyors passing through such ovens ordinarily comprise two parallel continuous conveyor chains traveling in upper and lower courses. Upstanding wickets with appropriate work supporting brackets are carried between the traveling chains and are adapted to support large flat lithographed metal sheets and the like thereon for proper uniform drying of the lithographed coating. There is at the present time a considerable effort being made in the industry to increase the productivity of such ovens by operating the conveyors at higher and higher rates of speed. It will be appreciated, however, that the work must be brought up to proper temperature and maintained at such temperature for a sufiicient length of time to obtain the desired effect, and it has consequently become important to introduce the hot drying gases to the oven in larger and larger volumes per unit of time. The work is ordinarily cooled immediately prior to delivery of the same at the unloading end of the oven, and this, of course, means that the conveyor and wickets will again require to be brought up to temperature when they have returned to the loading end of the oven. If the hot gas inflow is insufiicient adjacent the loading end of the oven, the lower portion of the work-pieces will become heated much more rapidly than their uper portions, and this may cause warping, wrinkles in the finish, and various other blemishes. On the other hand, it is not practical to heat such incoming gases to too high a temperature or the work will be damaged. Uneven distribution of the incoming heated gases may also result in scorching of the sheets and melting of the tin plating. Once the work-pieces have been raised to the desired temperature, they may be maintained at such temperature during the remainder of their passage through the oven without a great deal of difiiculty and without the necessity of employing such large volumes of heated air and other gases.

In order to conserve plant space it is often desired that the heated gases be delivered to the oven at one side only thereof. It becomes a very difiicult problem, how ever, when introducing such a large gas flow to the oven at one side only thereof, properly to regulate such flow to admit the gases to the oven uniformly both transversely of the oven and longitudinally thereof. It is important that their admission should be uniform since otherwise there may be a tendency to flutter the work on the supporting wickets with consequent sheet markings and to form hot spots and cold spots, resulting in uneven treatment of the work. The heated gases will ordinarily be introduced directly beneath the upper course of the conveyor and will rise past the upstanding wickets and work- 2 ,845,726 Patented Aug. 5, 1958 2 pieces resting thereagainst to be withdrawn from the upper portion of the oven for reheating and recirculation.

It is accordingly a principal object of my invention to provide a novel gas inlet means for wicket type conveyor ovens and the like capable of distributing large volume gas flow uniformly both transversely and longitudinally of such oven to shorten the time required to bring the conveyor and work to peak temperature.

Another object is to provide such oven duct means adapted to receive a large volume of gas laterally of the oven and to divide such flow, directing a portion thereof upstream in the oven, a portion downstream, and a portion intermediate for uniform rapid heating of the work through a considerable longitudinal extent of the oven adjacent the loading end of the latter.

Other objects of the invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

Fig. 1 is a side elevational view of a wicket type conveyor oven adjacent the loading end thereof;

Fig. 2 is a top plan view of such end portion of the oven;

Fig. 3 is a plan view of my novel duct means partly broken away along the'line 33 on Fig. 4;

Fig. 4 is an elevational view of such duct means taken on the line 44 on Fig. 3;

Fig. 5 is a fragmentary detail view on an enlarged scale taken on the line 55 on Fig. 3;

Fig. 6 is a vertical transverse section taken on the line 66 on Fig. 4;

Fig. 7 is a fragmentary detail view of a flange connection taken on the line 77 on Fig. 3; and

Fig. 8 is a top plan view of my new duct means corresponding to Fig. 3 but on a smaller scale and showing the complete upper surface of the same.

Now referring more particularly to Figs. 1 and 2 of the drawing, the duct means of my invention is adapted to be installed in a wicket type conveyor oven which may comprise a long insulated chamber 1 with a conveyor extending therethrough having an upper course 2 and a lower course 3, such conveyor being driven by electric motor 4 through sprockets 5.

Immediately adjacent the loading end of the oven where work-pieces are to be placed upon the conveyor, an overhead exhaust duct 6 is provided connected to fan housing 7 and stack 8 whereby ventilation is afforded.

A large gas-fired air heater 9 is mounted on top of the Oven and connected with blower housing 10 leading to duct 11 extending downwardly laterally of the oven. The lower end of such duct connects laterally with the rectangular inlet 12 of my new duct means 13 indicated generally in Fig. l and in greater detail in Figs. 3 and 4.

Referring now also to Figs. 6-8 inclusive of the drawing, my new duct means comprises a rectangular boxlike sheet metal compartment 14 extending the width of the oven and divided into upper and lower compartments by means of horizontal shelf or deck 15. The entrance to the lower compartment may be one and one-half times the area of that of the upper comparttudinally of the oven in this central region 17. Such louvers are preferably formed of elongated sheet metal elements 13 of general U-shape cross-section as well known in the art. Reinforcing rods 19 rigidify the structure and a Wide cross-channel 29 may be included to afford clearance for conveyor chain supporting means.

The lower portion of compartment 14 is divided into two equal chambers by a vertical partition 21 so that the air flow entering from inlet duct 12 is similarly divided. In each such chamber, series of baffies 22 and 23 are arranged diagonally to divert the air flow at right angles and deliver the same to the sheet metal extensions 24 and 25 respectively. Such baffles will desirably be formed of curved sheet metal elements shaped to provide passages therebetween affording uniform volume and velocity of air movement into the sheet metal extensions 24 and 25. The gases pass through expanded metal diifusing screens 2:; and 27 where entering such extensions 24 and 25, the fioors of the latter being inclined upwardly toward their respective ends longitudinally of the oven to maintain substantially uniform pressure therewithin despite gradual escape of the gases upwardly through the upper surfaces which are louvered transversely of the oven as best shown in Fig. 8. Such transversely louvered surfaces 28 and 29 are likewise preferably formed of U-shape channel members rigidified by rods welded thereto and providing elongated parallel restricted orifices therebetween for upward escape of gases into the oven immediately beneath the upper courses 2 of the conveyor. It will accordingly be seen that my oven inlet means is divided into three principal sections, the centermost receiving air directly from duct 12 transversely of the oven and the louvered openings extending longitudinally of the oven also being arranged transversely of the direction of air flow. The two end extensions 24 and 25 receive gases diverted into them by curved baffles 22 and 23 and have their louvered openings arranged transversely of the oven but nevertheless also transversely of the direction of air flow where delivered to the oven.

For purposes of obtaining a good seal, asbestos strips such as 36 may desirably be interposed between opposed duct flanges such as 31 and 32, such construction also tending to reduce transmission of vibration and noise.

Employing the oven inlet means for hot air and gases above described, I am enabled to introduce extremely large volumes into the oven in order to bring the work up to the desired temperature at an early stage in its passage through the oven, greatly increasing the productivity of the latter. It will be appreciated that when the conveyor is receiving and delivering approximately 150 lithographed metal sheets per minute, about 25 tons of metal will require to be raised to the desired tempsrature in a single hour. The over-all length of my new inlet may be varied as desired, depending upon the size of the oven and the speed of conveyor travel, but in a typical installation such duct may extend a distance of about feet longitudinally of the oven and an individual work-piece may be carried ther over by the conveyor during a two-minute period. The over-all length of the duct longitudinally of the oven will preferably be about three times the corresponding length of the duct entrance 12. The sloping floors or bottoms of the three principal portions of the duct together with the transverse arrangement of the louvers through which the heated air and gases are delivered ensures a proper and uniform distribution of the flow so that the thin lithographed sheets carried by the conveyor will not be caused to flutter or be unevenly heated. The two endrnost sections 24 and may have upper orifice areas substantially the same size as that of the central region 17.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any 4 of the following claims or the equivalent of such be employed.

1 therefore particularly point out and distinctly claim as my invention:

1. In a heat processing oven having a wicket type conveyor extending therein in upper and lower parallel courses, said oven and conveyor having a loading end and an unloading end; hot gas supply means to said oven comprising a heater located above said oven, a duct extending downwardly from said heater laterally of said oven, a continuation of said duct extending horizontally into said oven on one side only; and a duct opening upwardly directly beneath said upper course adjacent said inlet end comprising a central rectangular box-like portion having top louvers which extend longitudinally of said over. and conveyor course, a horizontal shelf within said box-like portion dividing it into upper and lower compartments, the entrance to said lower compartment from said horizontal duct being approximately one and one-half times the size of that to said upper compartment, a pan above said shelf forming an upwardly inclined floor for said upper compartment from the entrance thereto transversely of said compartment, a vertical partition centrally dividing said lower compartment, a series of curved bafiles arranged in each of the resultant two chambers of said lower compartment respectively to direct gases entering from said horizontal duct in opposite directions longitudinally of said oven and conveyor; and extensions adapted to receive and distribute such gases at each end of the aforesaid central portion comprising lateral duct extensions from said respective chambers having upwardly inclined floors longtudinally of said oven and upper louvers extending transversely of said oven, each of the transversely louvered regions being contiguous to and of slightly less area than the intervening longitudinally louvered region.

2. In a heat processing oven having a wicket type conveyor extending therein in upper and lower parallel courses, said oven and conveyor having a loading end and an unloading end; hot gas supply means to said oven comprising an inlet duct extending laterally into said oven and having a duct to the interior of said oven opening upwardly beneath said upper conveyor course, said latter duct comprising a central rectangular box-like portion having top louvers which extend longitudinally of said oven and conveyor course, a horizontal shelf within said box-like portion dividing it into upper and lower compartments, a pan above said shelf forming an upwardly inclined floor for said upper compartment from the entrance thereto transversely of said compartment, a vertical partition centrally dividing said lower compartment, 21 series of curved baflles arranged in each of the resultant two chambers of said lower compartment respectively to direct gases entering from said inlet duct in opposite directions longitudinally of said oven and conveyor; and extensions adapted to receive and distribute such gases at each end of the aforesaid central portion comprising lateral duct extensions from said respective chambers having upwardly inclined floors longitudinally of said oven and upper louvers extending transversely of said oven, each transversely louvered region being contiguous to the intervening longitudinally louvered region.

3. Structure as defined in claim 2, including diffusion screens interposed between the series of bafiles and the entrances to the respective extensions.

4. In an oven having a conveyor extending therein in upper and lower parallel courses, said oven and conveyor having a loadin end and an unloading end; hot gas supply means to said oven comprising an inlet duct extending laterally into said oven and having a duct to the interior of said oven opening upwardly beneath said upper conveyor course, said latter duct comprising a central rectangular box-like portion having top louvers which extend longitudinally of said oven and conveyor course, a horizontal shelf within said box-like portion dividing it into upper and lower compartments, a pan above said shelf forming an upwardly inclined floor for said upper compartment from the entrance thereto transversely of said compartment, a vertical partition centrally dividing said lower compartment, a series of baflles arranged in each of the resultant two chambers of said lower compartment respectively to direct gases entering from said inlet duct in opposite directions longitudinally of said oven and conveyor; and extensions adapted to receive and distribute such gases at each end of the aforesaid central portion comprising lateral duct extensions from said respective chambers having upwardly inclined floors longitudinally of said oven and upper louvers extending transversely of said oven.

5. An oven duct having a central portion formed with louver slots therein extending longitudinally of the oven, respective end portions having louver slots therein which extend transversely of the oven, an inlet duct arranged to deliver gases to said central portion laterally of the oven, and flow diversion means arranged to divert a portion of the incoming gases to said respective end portions in directions longitudinally of said oven.

6. In an oven having a conveyor arranged horizontally longitudinally therein, gas inlet means comprising a central horizontal portion having louver slots therein which extend longitudinally of said oven and conveyor, respective horizontal end extension portions having louver slots therein extending transversely of said oven and conveyor, lateral duct means communicating with said central portion, a compartment vertically disposed relative to said central portion and separated therefrom but adapted to receive a part of the inflow from said duct means, and diversion means in said compartment operative to divert gas flow in opposite directions longitudinally of said oven to said respective transversely louvered end portions.

7. The inlet means of claim 6, including diffusion screens extending transversely of the oven interposed between said diversion means and said louver slots in said respective end portions.

8. In gas inlet means for ovens and the like, a central inlet port to said oven, an inlet port to said oven on each side of and separate from said central port, a supply duct leading laterally to said central port, a chamber vertically beneath said central port separated from direct communication with said central port but also in communication with said lateral supply duct, and bafiles in said chamber efiective to direct portions of the inflow thereto in opposite directions to said respective ports on each side of said central port.

References Cited in the file of this patent UNITED STATES PATENTS 2,568,695 Bailey Sept. 25, 1951

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