US2582462A

US2582462A - Process for atmospheric control

Info

Publication number: US2582462A
Application number: US762047A
Authority: US
Inventors: Jewett F Schrumn
Original assignee: Metals and Controls Corp
Current assignee: Metals and Controls Corp
Priority date: 1943-09-10
Filing date: 1947-07-19
Publication date: 1952-01-15
Anticipated expiration: 1969-01-15

Description

Jan. 15, 1952 J. F. SCHRUMN PROCESS FOR ATMOSPHERIC CONTROL 2 SHEETS-SHEET l Original Filed Sept. 10

FIGI.

Jan. 15, 1952 J. F. SCHRUMN PROCESS FOR ATMOSPHERIC CONTROL 2 SI IEETSSl'iEET 2 Original Filed Sept. 10, 1943 F'IG 6.

Patented Jan. 15, 1952 iROGEfi S: 11393 ,ATMOSEHERIC :GDNEIRQ'LV.

Jewe'tt" F; Sehrumm, Reno; New, assignor' to Metals 85- Cbntrols Corporation;

Attleboro;

Mass-., a. corporation of Massachusetts 9rig-inalcaglll lication September 19,11943, Serial: No; 501,153; Divided andithisiamllication-lllly- 19., 1941; "Serial No. 162,047

4 Claims; (01. 263-52) "This'invention relates to a" process for atmos= pheric control, and withregard to certain more specific features to" processes for; reactionor treating -'-in':cham'bers; including furnaces,-.ylehrs and the like;

'This application isapdiizision'ofmy copendin ap'plicationt'serialNo. 501 ;7 53, filed .Septenibjer 10.; I943 issuedas Patent'-2;430,19-1, November 4; I947.

Amongthe several ofbj ects of thein-vention may be enoted the" provision of an atmospheric LCQIItlO'l foriurnacesxand other reaction chambers which allows articles to be introduced and removed fi'pm said apparatus iwithout upsetting the dc: sited atmosphericlcontrolg theprovision oifgprocesses ofithe class described which positirelymaim pl tication :of which rabe indicated inithe fellow his claims;

In the accompanying drawings; in whichqis illustrated-woof various possible embodiments of-ztheinvention;

Fig; :1 isza plan view-of theinvention;

Fig. 2.1 is :a isidenelevation drawn to thewsam scaleias Fig; ;1';;

- Fig. '3 is anhorizontai-l section :taken on line3-3 ofi'i :2;:but.on anzenlarged scale;

' Fig: 4 is ai-verticaltsectien takenon'line-fi-l' of Fig. 3, being on said enlarged scale;

Fig:.i5' is aiidiag rammatic longitudinal lsectional View :on' areducedssca'le. illustrating a mod'ifica-- tionaandi certain principles of operation ofthe invention;

. Fig; 6 is a diagr-ammatic vertical section-viewed from. the left of Fig; 5zant1 illustrating certain operating characteristics;

Fig: Visa view-similar to Fig. 6 illustrating certain operating characterlstics oi" certain prior art; and;

*8 is a side elevation-illustrating the central partof a heating chamber oi' this"it-1ven t'ion.

Similar reference characters indicate come and thereafter-.1

spending parts throughout the several views: or the drawings:

An' atmospheric"heat treatingf furnace, which furnishes "an example of one i application ofthe invention; is one in which articles are either placed-in; or'passedthrough, the furnace and electrically or otherwise heated" in the" presence of a 'blanketingmassof a reducing (non-oxidiz ing) atmosphere (gas). The purposeof ythisis to bring'thearticles *up to a desired heat-treating temperature and at the" same time to avoid oxidation-such-a-s would occur if the articles were heatedin an atmosphere or oxidiz ng as such as air: Generally" (and; such" an example is, used herein), the" work' is' sent through the furnace on a continuously endless belt. This, (if-course, implies the necessityuforan inlet'and an outlet to the furnace forvintroducin ;and.11:emoving the Work; Theireducingigas, such as for example partially burned ,hfluel gas; is introduced. in sub stantlal volume atsome mid-point of the fure mace .and allowed to run out at theinlet and out? let. At the inlet and outletiteis generallycollectecl by some :type of loiitake, burned and disposed-of to the outside atmosphere:

Itha's always been the purpose-completely to mufile the articles the vreduci-ng: aseous at? mosphereas long as they areat an oxidizing temperature; -;-and, .-usually ifiri 'somentime thesebefone capin cfromtheifurnacefinlets or outlets; tendedtmrise fmmithe zhoiitomxof the furnace. Oxidiz ingairtookuitsxplacer andmrept back into the funnacealongits hottomiiior a distance great enough" often" to reach articles of high enough temperature to oxidize them. This difficulty has- F hasf-been to provide anofitak-e just above their let or outlet tasthe case "marbei with a flame curtain pilayingii'om below '-and'-arising into the upwardx-offtake: 'I'l-irougli this flame curtain the articles passed in entering and a leaving the fur nacebut "it wasfound that the passing articles oxidation. The :gas supply to-the curtain was. also wasteful; 'will be furthereluc'iciated' 3 later, in connection with the drawings. Furthermore, none of the prior solutions adequately prevents the unstable conditions that always occur at an entrance or exit under drafty, variablepressure, or similar surrounding conditions.

Referring now more particularly to the drawings, there is indicated at numeral I the muiiie 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 the furnace. It is to be understood that the muffle compartment of the furnace I is provided with suitable electric or other heating means and also with a suitable inlet 6 (Fig. 8) for the mufiling or the reducing gas which is to form the mufiling 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 I is indicated the entrance portion of the furnace and at 9 the outlet or exit portion. From these extend outside tunnel-like hoods I I, carrying interior spaced fins I3. These interiorly finned hoods substantially guard the entrance 'I 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 I3 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 II form a part of the invention alone, or in combination with the parts subsequently to be described, nevertheless these bailled tunnels may be eliminated and the features to be described hereinafter will still be op erative 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 offtake slits I5 communicating downwardly with crosswise manifolds I I. These manifolds IT in turn communicate with vertical flues I9 controlled by dampers 2I. 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 mufile 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 I5.

As indicated in Figs. 3 and 4, each opening I5 substantially spansthe wire belt 5. Small pilotlight gas nozzles 23 just outside of the slits I5 serve to keep the descending cascading mass of mufile gas ignited. It will be appreciated that ignition does not proceed back into the furnace I, for lack of oxygen therein. Oxygen required for igniting the descending gas at the slits I5 is provided by outside air entering the tunnels II. This air creeps in gradually without undue disturbance in view of the baffles I3. It will be 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 alternativewithout the tunnels II, 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 I! and the flue I9 causes said gas to descend at the inlet I and outlet 9 to cascadedown into the inlet slits I5. 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 evenas 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 indi cated 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 the furnace. Since minimization of air entry was a desired end, this waste of gas was resorted to. The present invention avoids it and only enough gas is used to flll the furnace so as 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 theresulting 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 out' let 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 outlet 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 nonheated 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 ambient temperature, above or below ambient temperature, and comprising gas or gases for various treating purposes such as oxidizing, reducing, and other chemical reactions. The term includes the term controlled atmosphere, which often denotes a reducing atmosphere at elevated temperature.

A special atmosphere may include simply poisonous non-combustible gases which would require no ignition of the descending curtain part at the opening l5. 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.

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 processes 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. The process of controlling the atmosphere in a work-treating chamber which has an opening for introducing or removing work, comprising continuously introducing into the chamber a gas other than air for treating work in the chamber, and continuously drawing off the gas from within the chamber in such manner as to provide an air-excluding curtain consisting substantially only of said gas flowing across the opening while maintaining the chamber filled with said gas.

2. The process of controlling the atmosphere in a work-treating chamber which has a generally vertical opening for introducing or removing work, comprising continuously introducing into the chamber a gas other than air for treating work in the chamber, and continuously withdrawing said gas from within the chamber in such manner as to provide an air-excluding uninterrupted curtain consisting substantially only of said gas flowing downward across the opening tain consisting substantially only of said gas extending completely across the opening by maintaining a subatmospheric pressure in an oiftake extending completely across the bottom of the opening, while maintaining the furnace filled with said gas.

4. The process of controlling the atmosphere in a work-treating furnace having a generally vertical opening for introduction or removal of work, comprising continuously introducing into the furnace a combustible reducing gas, continuously withdrawing said gas from within the furnace downward across the full width of the opening to provide a downwardly flowing airexcluding curtain consisting substantially only of said gas extending completely across the opening by maintaining a subatmospheric pressure in an offtake extending completely across the bottom of the opening, while maintaining the furnace filled with said gas, and igniting the curtain of gas to provide a flame curtain.

JEWETT F. SCHRUMN.

REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 549,235 Gatche Nov. 5, 1895 1,725,129 Carpenter et al. Aug. 20, 1929 1,808,721 Hayes June 2, 1931 2,064,532 Gilbert Dec. 15, 1936 2,175,922 Scott Oct. 10, 1939 2,192,191 Hayes Mar. 5, 1940 2,222,809 Curran Nov. 26, 1940 2,430,191 Schrumn Nov. 4, 1947