US2430191A - Atmospheric control means - Google Patents

Description

Nov. 4, 1947. J. FQSCHRUMN I 2,439,191

' ATMOSPHERIC CONTROL MEANS v Filed. Sept. 10, 1943 2 Sheets-Sheet 1 Nov. 1947. I J. F} SCHRUMN 2,430,191

ATMOSPHERIC CONTROL MEANS Filed Sept, 10, 1945 2 Sheets-Sheet 2 j no.

w I l ,5 llll r Patented Nov. 4, 1947 UNITED STATES PATENT OFFICIE ATMO SPHERIC' CONTROL MEANS Application September 10, 1943, Serial No. 501,753

6 Claims. (Cl. 263-8) This invention relates to atmospheric control means, and with regard to certain more specificfeatures to such means for reaction or treating chambers including furnaces, lehrs and the like.

Among the several objects of the invention may be noted the provision of an atmospheric control for furnaces and other reaction chambers which allows articlesto be introduced and removed from said apparatus without upsetting the desired atmospheric control; the provision of apparatus of the class described which positively maintains atmospheric control in respect to articles passing through the treating chamber throughout their entire traverse; the provision of apparatus of this class which accomplishes the end with a substantial saving inthe materials which provide the controlling atmosphere; and the provision of ap- Daratus of the class described which is effective in drafty locations-of the furnace entrance or exit. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is illustrated one of variouspossible embodiments of the invention,

Fig- 1 is a plan view of the invention;

Fig. 2 is a side elevation drawn to the same scale as Fig. 1;

Fig. 3 is a horizontal section taken on line 3-3 of Fig. 2, but on an enlarged scale;

Fig. 4 is a vertical section taken. on line 4-4 of Fig. 3. being on said enlarged scale;

Fig. 5 is a diagrammatic longitudinal sectional view on a reduced scale illustrating a modification and certain principles of operation of the invention;

Fig. 6 is a diagrammatic vertical section viewed from the left of Fig. 5 and illustrating certain operating characteristics;

Fig. 7 is. a view similar to Fig. 6 illustrating certain operating characteristics of certain prior art, and,

Fig.8 is a side elevation illustrating the centralpart of a treating chamber of this invention.

Similar reference characters indicate corresponding partsthroughout the several views of the drawings.

An atmospheric heat-treating furnace, which furnishes an example of one application of the invention, is one: inwhich articles are either placed in, or passed through, the furnace and electrically or otherwise heated in the presence of a blanketing mass of a reducing (non-oxidizing) atmosphere (gas). Thepurpose of this is to bring the articles up to a desired heat-treating temperature and at the same time to avoid oxidation such as would occur if the articles were heated in an atmosphere of oxidizing gas such as air. Generally (and such an example is used herein) the articles aresent through the furnace on a continuously endless belt. This, of course, implies the necessityfor an inlet and an outlet to the furnace for introducing and removing the articles. The reducing gas, such as for example partially burned fuel gas, isintroduced in substantial volume at some mid-point of the furnace and allowed to run out at the inlet and outlet. At the inlet and outlet it is generally collected by some type of offtake, burned and disposed of to the outside atmosphere.

t has always been the purpose completely to muffle the articles in the reducing gaseous atmosphere as long as they are at an oxidizing temperature, and, usually forsome time therebefore and thereafter.

A prior difficulty wasthat the hot-gas, in escaping fromthe furnaceinlets or outlets, tended to rise from the bottom of the furnace. Oxidizing air took itsplace and-crept back into the furnace inlet or outlet (as the case may be) with a flamecurtain playing from below and arising into the upward offtake. Through thi flame curtain the articles passed in entering and leaving the furnace, but it was found that the passing articles themselves blocked off the flame curtain, leaving openings through which the oxidizing air could enter andcreep back into the furnace to cause oxidation. The gassupply to the curtain was also wasteful. All this'will be further elucidated later, in connection with the drawings. Furthermore, none of the prior solutions adequately prevents the unstable conditions that al-' ways occur at an entrance or exit under drafty, variable-pressure, orsimilar surrounding conditions.

To minimize ndii Referring now more particularly to the drawings, there is indicated at numeral l the muffle part of the furnace built upon a support 3 and through which passes an open-mesh belt 5. This belt supports the articles to be carried through th furnace. It is to be understood that the muffle compartment of the furnace I is provided with suitable electricor other heating means and also with a suitable inlet 6 (Fig. 8) for the muffling or the reducing gas which is to form the rnuiiiing ambient reducing atmosphere for the articles which are passing through on the belt 5. The heating elements, being known, are therefore not shown.

At numeral 1 is indicated the entrance portion of the furnace and at 9 the outlet or exit portion. From these extend outside tunnel-like hoods H, carrying interior spaced fins [3. These interiorly finned hoods substantially guard the entrance 1 and exit 9 from the effect of ambient atmospheric draft and pressure disturbances, so that the effects desired at the entrance I and exit 9 are not substantially disturbed. The fins I 3 have the effect of bringing about turbulence in any air that tends to enter through the tunnels and to destroy its entering motion in friction. That is, it breaks up streamline progress of air. toward the furnace opening. In addition, the tunnel itself forms a cover for the opening guarding it from the direct influence of outside cross currents.

It must be understood that, although the baffled entry guard tunnels ll form a part of the invention alone, or in combination with th parts subsequently to be described, nevertheles these bafiied tunnels may be eliminated and the features to be described hereinafter will still be operative on their own merits. These important features are as follows:

Just beneath the entrance I, also beneath the outlet 9, and below the moving belt are arranged laterally elongate gas oiftake slits 15 communicating downwardly with crosswise manifolds ll. These manifolds L1 in turn communicate with vertical fiues l9 controlled by dampers 2!. These flues rise to form stacks providing an induced draft, or they may pass to suitable suction apparatus for maintaining the desired draft. The important point is that the muflie gases from the furnace are drawn downward from their naturally elevated positions at the inlet and outlet, then through the belt 5 and down through the openings [5.

As indicated in Figs. 3 and 4, each opening 15 substantially spans the Wire belt 5. Small pilotlight gas nozzles 23 just outside of the slits l5 serve to keep the descending cascading mass of mufile gas ignited. It will be appreciated that ignition does not proceed back into the furnace l, for lack of oxygen therein. Oxygen required for igniting the descending gas at the slits i5 is pro-' vided by outside air entering the tunnels ll, This air creeps in gradually without undue disturbance in view of the bafiles l3. It will b understood that the same igniting effect is obtained from the outside air when the tunnels II are dispensed with, as is possible under quiet ambient atmospheric conditions.

In Figs. 5 and 6 is diagrammatically shown the entrance end of an alternative without the tunnels H, wherein like numerals designate like parts.

Operation is as follows:

The furnace I is heated and the reducing gas is introduced therein in quantity enough to displace the air therein and to flow towards its ends. This gas tends to rise. The induced draft effect through the manifold l1 and the flue [9 causes said gas to descend at the inlet 1 and outlet 9 to cascade down into the inlet slits l5, thus presenting a downwardly flowing curtain of gas. The outer surface of this downwardly flowing gas is ignited from the pilot burners 23, combustion being supported by adjacent outside air. The flame curtaining effect is diagrammatically indicated in Figs. 5 and 6 (Fig. 6 is a left-end view of Fig. 5) wherein it will be seen that no opening occurs through the curtain for entry of air a even as articles A pass.

In Fig. 7 is shown a diagram corresponding to Fig. 6 but representing the prior art. It shows what occurs with a rising flame curtain as heretofore used with a flue outlet 0 at the top of the furnace inlet or outlet and a rising flame curtain from a burner slot at the bottom. In this case, open regions 25 occur around passing articles A through which outside air proceeds back into the furnace. In addition, if a substantially large gas flow is not maintained, the gas, as it proceeds outward, lifts from the conveyor 5. This is due to its heated condition which makes it light. The spaces 25 afford passage for air into the specified space beneath the gas. It will be noted from Fig. 6 that the passages 25 are eliminated and from Fig. 5, that behind the curtain there can be no oxidizing air. It is all positively blocked off,

The invention not only completely blocks off all entry of air into the furnace and thus eliminates any possibility of oxidation of heated products therein, but also effects a substantial saving in the gas used. This is because, as indicated above, under the old condition air entry could be somewhat minimized by increasing the rate of gas flow so as to cause a greater sweeping action toward the inlet and outlet of th furnace. Since minimization of air entry was a desired end, this wasteof gas was resorted to. The present invention avoids it and only enough gas is used to maintain article coverage without the necessity for an excess to maintain the old higher pressure needed at the inlet and outlet.

The purpose of the damper controls 2| is to accommodate the draft to various conditions. For example, more draft is required in the offtake at the front I of the furnace than at the rear 9, because the furnace is generally operated hotter at this end. This requires more suction draft effect to draw down the resulting lighter gases as they tend to emerge at the top of the furnace inlet.

-In Figs. 5 and 6 a sliding control door D is. used which may be adjusted to minimize the outlet or inlet area according to the size of the passing articles. It is to be understood that such doors may be applied at the inlet and out-- let 1 and 9 of Figs. 1-4. Such doors are old and the invention is operable independently of them.

It is to be understood that the invention is applicable to heated normalizing lehrs, as well as to furnaces per se, where such lehrs are used in association with an interior reducing atmosphere. It is also applicable to box-type furnaces and non-heated gas-treating compartments in general.

It is also to be understood that the elements of the invention are independently applicable to furnace inlets or outlets.

The term special atmosphere is used herein with the meaning often attributed to it in the art, namely, a gaseous atmosphere or vapor at sonous non-combustible gases which would require no ignition of the descending curtain part at the opening 15. It would also include gases used in other treating compartments, such as for gasing fruits where the present principles of producing a descending gas curtain are applicable.

Reference under rule 43 is made to applicants copending application entitled Process for atmospheric control, Serial No, 762,047, filed July 19, 1947, as a division of this application.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In apparatus of the class described, a tunnel having an opening, said tunnel having therein a special atmosphere approaching the opening and normally tending to rise, a downwardly located moving support moving with respect to the tunnel and through said opening and carrying along the bottom of the tunnel articles to be treated, a manifold providing an extended inlet adjacent and spanning said opening and below the path of the support, means for drawing said atmosphere down into said manifold and through said inlet, and means for igniting said atmosphere as it descends.

2. An atmospheric furnace having an opening and an article-supporting belt moving through said opening, a suction box having an inlet located beneath said belt, said inlet being crosswise of said opening and extending substantially across said belt, means for producing a subatmospheric pressure in said box to draw into said inlet atmosphere from the furnace, and a draft guard constituting a tunnel projecting beyond said opening and over said belt.

3. An atmospheric furnace having an opening and an article-supporting belt moving through said opening, a suction box having an inlet 1ocated beneath said belt crosswise of said opening, means for producing a subatmospheric pressure in said box to draw into said inlet atmosphere from the furnace, a draft guard constituting a tunnel projecting beyond said opening and over said belt, and spaced interior fins on said guard.

4. An atmospheric furnace having an opening and a reticulated article-supporting belt moving through said opening, and a draft guard constituting a tunnel projecting from said opening and over said belt, said tunnel having spaced interior fins.

5. In apparatus of the class described, a chamber having an opening for passage of articles therethrough, said chamber having a flow of a combustible atmosphere therein which tends to rise, a manifold providing an inlet located at the lower side of said opening, and means for drawing said atmosphere across said opening and downward into said inlet to form a downward cascading movement of the atmosphere at the opening, and means to ignite said atmosphere adjacent the outside of the opening to form a flame curtain.

6. In apparatus of the class described, an elongate, open-ended treating chamber, a reticulated conveyor adapted for travel along the bottom of said chamber for carrying articles to be treated therethrough, said chamber having an inlet for a special treating atmosphere which normally,

tends to rise and an offtake for said atmosphere adjacent each end of the chamber below the path of said conveyor, each offtake comprising a slit extending transversely of the chamber for substantially the full width of its open ends, and means for drawing off said atmosphere through said slits thereby to provide a downwardly flowing curtain of said atmosphere across both open ends of the chamber to exclude the outside atmosphere therefrom.

JEWETT F. SCI-IRUMN.

\ REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,233,474 Dreiffein Mar. 4, 1941 2,028,941 McIntyre Jan. 28, 1936 1,722,797 Jessup July 30, 1929 1,945,851 Freeland Feb. 6, 1934 1,463,923 Nelson Aug. 7, 1923 1,487,362 Rice Mar. 18, 1924 2,119,261 Andrews May 31, 1938 1,580,957 Chaffe et a1. Apr. 13, 1926 1,505,768 Dressler Aug. 19, 1924 1,099,276 Bauer June 9, 1914 923,092 Valentine May 25, 1909 2,408,434 Munn et a1. Oct. 1, 1946

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