US2926008A - Vertical oven - Google Patents

Description

c. H. BARNETT E L 2,926,008

Feb. 23, 1960 VERTICAL OVEN 3 Sheets-Sheet 1 Filed April 12. 1956 INVENTORj CHARLES H. 36RNETT, y JOjEPI-I M. BEYVL A TTOIWVCYJ Feb. 23, 1960 c. Hv BARNETT T ,9

VERTICAL OVEN Fil ed April 12, 1956 3 Sheets-Sheet 2 cgl cncll .1 ":3 t: :J cal INVFNTORS i BY Q; ,Q, h' l l ATTOIQNEYJ- Feb. 23, 1960 c. H. BARNETT ETAL 2,926,008

VERTICAL OVEN Filed April 12, 1956 3 Sheets-Sheet 3 IN VEN TOR5.

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1.) TTOR/VE Y5- United States 2,926,008 VERTICAL OVEN This invention relates as indicated to a novel vertical oven structure, and more particularly to a core baking oven of the general type shown and described in Barnett et a1. Patent 1,934,904, for example.

Ovens of the type disclosed in such aforesaid patent have provenvery successful in the trade and are now widely used for the baking of foundry cores and the like. A chain conveyor having two parallel vertically disposed courses is loaded with cores at one side of the oven, and such cores are then carried upwardly through a heating zone and then downwardly through a cooling zone before being-unloaded from the opposite side of the oven. -Heated air and other gases are forced from a central plenum chamber transversely of such rising course of the conveyor, and these rise to the top of the oven where a portion is drawn off and the remainder pulled downwardly to the combustion chamber for reheating and recirculation.

In order to increase production, ovens of this general type have been made higher and higher until some of them are now as much as 80 feet high. With this increasing height, certain problems have become accentuated. If the heated air which is forced from the central plenum chamber into the region of the oven through which the ascending course of the conveyor passes must then rise to the top of the oven before being pulled back down to the heating unit, it is found relatively diflicult to do so as the height of the oven increases, and more and more powerful blowers are required. Moreover, once such heated air and gases are thus blown across the ascending course of the conveyor (and the cores transported thereby), such air and gases thereafter merely rise upwardly to the top of the oven without sufficient turbulence to transfer the amount of heat to such cores of which they are theoretically capable.

In order to increase production, there is a continuing tendency on the part of the oven operators to drive the conveyors at greater speeds and correspondingly to increase the oven temperatures. Possibilities in this direction are, however, severely limited by the fact that the core binders are adversely affected if local temperatures reach too high a level. Thus, in the case of the common linseed oil binder, the cores will become burned if subjected to too high temperature and in the case of the more recently adopted resin binders, the strength thereof decreases if, once set, they are further subjected to high temperatures. These problems, of course, arise principally with regard to relatively small or thin core portions such as fins and the like which will be fully baked well in advance of the main body of the core. It is essential that these relatively thin and fragile portions of the core should not be overheated during the further baking of the body of the core. Of course, the use of relatively high baking temperatures is also expensive and should be avoided for economic reasons when possible.

It is accordingly an important object of our invention Patented Feb. 23, 19 60 to provide an improved oven construction affording a greater degree of turbulence and air flow transversely of the rising course of the conveyor.

Another object is to provide such oven which will be of increased efficiency in operation and accordingly capable of greater productivity without increase in operating temperature above safe levels.

Still another object is to provide such ovens including means for return of a portion of the heating air from the ascending course of the conveyor to the heating means without the necessity of passing through the upper part of the oven.

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 draw ing 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 shows an embodiment of our invention in vertical elevation;

Fig. 2 is another elevational view taken at right angles to Fig. 1; and

Fig. 3 is an enlarged fragmentary view in vertical section showing the construction of the plenum chamber and associated conduits.

Referring now more particularly to such drawing, the oven there illustrated is set within a pit 1 so that the adjacent floor level 2 will be at the proper elevation for loading and unloading the work supporting trays 3 carried by chain conveyor 4. As shown in Fig. 1, the loading side 5 is at the left and the unloading side 6 at the right, the left-hand conveyor course as viewed in Fig. 1 ascending and the right-hand course descending. The upper end of the conveyor passes about large sprocket wheels 7, and its lower end about appropriate guide means.

In the embodiment illustrated, the combustion chamher 8 of the heating means is located internally of the air heater housing H within the oven but the entire heater may optionally be located externally of the oven, if desired. As best shown in Fig. 3, air is drawn into such heater at 9 slightly above loading portal 5 and thereby providing negative pressure effective to prevent outflow of hot gases which would cause discomfort to the workers. The heated air and gases of combustion are withdrawn through duct 10 through action of blower 11 and delivered to plenum chamber 12 through duct 13 a little above the vertical mid-point of such chamber. The hot gases escape from such plenum chamber through damper controlled outlets 14 so that such hot gases flow trans versely of the ascending conveyor course with a turbulent wiping action across the green cores supported on the conveyor trays.

The basic construction described above is generally similar to that of Barnett et a1. Patent 1,934,904 and a stack 15 is similarly provided for withdrawal of a portion of the hot gases which rise to the top of the tower. Provision is also made for cooling the work on the descending course above unloading portal 6 by introduction of cooling air forced into supply boot 16 by fan 17. Having served its purpose, and to prevent such cooling air from being blown out at the unloading portal 6, lateral exhaust ducts 18 and 19 are connected through exhaust fan 20 to stack 21.

The principal novel features of our construction will best be understood through reference to Fig. 3 of the drawing which shows the plenum chamber 12 on an enlarged scale. As above explained, when the heated gases enter such plenum chamber through duct 13, the interior of such chamber is pressurized thereby and the hot gases escape through the usual damper controlled ports 14 into the portion of the oven enclosure 22 containing the ascending course of the conveyor 4. Similar ports may optionally be opened to admit hot gases from the plenum chamber into the part of the oven containing the upper portion of the descending course of the 'conveyor. The blower 11 which maintains a negative pressure on heater 8 thereby serves to draw a portion of the gases into recirculation duct 23 from the descending side of the oven at 24, such gases being reheated and delivered to duct 10 for return to the plenum chamber. We provide a plurality of ducts or conduits such as 25, 26, 2'7, 28 and 29, preferably of circular or oval cross-section, which pass completely through the plenum chamber and therefore connect the principal heating side of the oven with such recirculation duct 23. Consequently, a considerable portion of the heated gases which are forced from the plenum chamber through ports 14 first pass across the work supporting trays of the conveyor and then again How back'across such trays to conduits such as 25 for recirculation through duct 23, heater 8, blower 11, duct 13 and plenum chamber 12. The cores are, of course, relatively cool at this stage in their processing, and it is desirable to transfer as much heat thereto as quickly as possible by producing the turbulence and return flow as above described. A considerable portion of these gases are then recirculated to the heater without being required first to flow upwardly to the top of the oven and then to be pulled down to recirculation port 24. Consequently, the heated gases which are blown against the work in the upper portion of the conveyor travel are not diluted to an undesirable extent with the gases which had previously been blown against the work in the lower portion of the conveyor travel and which had become partially cooled and saturated.

A further advantage resides in the fact that there is less tendency for the heated air to escape downwardly and return prematurely to the heater or escape outwardly through the loading opening 5. Tubular ducts 25-29 which extend transversely of the plenum chamber not only serve as passages but also act as interior brace means and permit somewhat lighter construction.

It will thus be seen that we have provided a novel vertical conveyor oven for baking cores and the like having an endless conveyor with parallel vertical courses, one ascending and one descending, blowing ports operative to blow hot gases transversely of the ascending course and suction ports adjacent such blowing ports at the same side of the conveyor course effective to withdraw a substantial portion of such hot gases deflected from the oven wall at the other side of the conveyor course. The recirculating duct 23 draws gases both through the port 24 in its upper end and also through such conduits 2529. While such conduits will ordinarily be provided only through the lower portion of the plenum chamber 12, as shown, they may also be utilized in the upper portion under certain circumstances, in which case the adjacent ports 14 toward the descending course of the conveyor will ordinarily be closed by the usual dampers. Of course, all such ports and conduits are adapted to be damper controlled to regulate the flow therethrough in conventional manner. As best shown in Fig. 3, the ports 14 and the conduits 25-29 through the lower portion of the plenum chamber will ordinarily be arranged in alternate horizontal rows and the dampers may ordinarily be adjusted so that the areas of ports 14 will be appreciably smaller than the areas of the adjacent conduit orifices to ensure a relatively high velocity of the hot gases escaping from such ports and to facilitate exit of such gases on their return flow through such conduits.

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 of the following claims or the equivalent of such be employed.

We therefore particularly point out and distinctly claim as our invention:

1. In a vertical oven for baking cores and the like having an endless conveyor with parallel vertical courses, one ascending and one descending, enclosures for said parallel vertical courses, a generally central plenum chamber between 'said courses, heating and blowing means for supplying heated gases under pressure to said plenum chamber, said plenum chamber having a wall portion forming a part of said enclosures, ports in said wall of said plenum chamber affording gas flow from said plenum chamber transversely of said ascending conveyor course, and a recirculating duct adjacent the lower portion of said plenum chamber on the side toward said descending course adapted to receive a portion of the gases from such side of the oven for delivery to said heating and blowing means; the improvement comprising a plurality of conduits communicating directly with the enclosure for said ascending course and extending transversely through said plenum chamber and said wall and communicating with said recirculating duct.

2. The oven of claim 1 wherein said conduits thus extend across approximately the lower half of said plenum chamber only.

3. The oven of claim 1 wherein said conduits are of substantially circular cross-section further to assist in structurally rigidifying said plenum chamber and also to minimize interference with gas flow within said plenum chamber.

4. The oven of claim 1 wherein horizontal rows of said conduits alternate with horizontal rows of said ports.

5. The oven of claim 1 wherein said heating means is located within said oven beneath said plenum chamber, and conveyor loading and unloading ports are provided below the level of said heating means, said conduits serving to draw air to said recirculating duct and thereby reducing the tendency of heated gases to flow out the loading port.

6. In a vertical industrial oven having an endless conveyor with parallel ventical courses, one ascending and one descending, an enclosure for said parallel vertical courses, an elongated plenum chamber, said plenum chamber having a wall portion forming a part of said enclosure, blowing ports in said wall thereof adjacent said ascending course, and suction ports adjacent said blowing ports in the same wall of the plenum chamber ettective to withdraw a substantial portion of such hot gases deflected from the enclosure wall on the ascending side of the conveyor course.

7. The oven of claim 6 wherein said blowing ports alternate vertically with said suction ports.

8. The oven of claim 6 wherein said blowing and suction ports are located internally of said oven intermediate said courses.

9. The oven of claim 6 wherein a series of said blowing ports are arranged alternately with a series of said suction ports vertically of said oven, said blowing ports being substantially smaller than said suction ports.

References Cited in the file of this patent UNITED STATES PATENTS 715,070 Hiorth Dec. 2, 1902 1,513,161 Darrah Oct. 28, 1924 1,934,904 Barnett et al. Nov. 14, 1933 1,947,408 Eastman Feb. 13, 1934 2,022,593 Fuykers Nov. 26, 1935 2,110,352 Baker Mar. 8, 1938 FOREIGN PATENTS 651,388 Great Britain Mar. 14, 1951

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