US2669445A - Heat-treating apparatus - Google Patents

Description

Feb. 16, 1954 H, LC OFT 2,669,445

' HEAT-TREATING APPARATUS Filed Feb. 15. 1950 3 Sheets-Sheet 1 IN V EN T03.

1441726? H H04 Cf-EOFT 1954 w. H. HOLCROFT HEAT-TREATING APPARATUS Filed Feb. 13, 1950 3 Sheets-Sheet 2 WAA 72-7? H. #04 CREW? Patented Feb. 16, 1954 HEAT-TREATING APPARATUS Walter H. Holcroft, Detroit, Mich., assignor to Holcroft & Company, Detroit, Mich., a corporation of Michigan Application February 13, 1950, Serial N 0. 143,909

Claims.

This invention relates to heat treating apparatus of the type having an atmosphere controlled furnace and having quenching means associated with the furnace.

It is an object of this invention to provide relatively simple heat treating apparatus capable of being readily operated with a minimum amount of attention on the part of personnel, and also being of a design which enables installation in a relatively small space at a minimum cost. In accordance with this invention all of the various operations may be automatically carried out in their proper sequence, and the furnace, as well as the associated quenching tank, may be supported at floor level, rendering it unnecessary to provide pits for subfloor installations.

It is another object of this invention to provide improved relatively simple means for introducing the articles to be heated into and for removing the same from the furnace. Briefly the furnace has a single opening in one wall, and the hearth of the furnace is in the form of a work supporting carriage movable into and out of the furnace through said opening.

Still another object of this invention is to provide a work supporting platform operating in conjunction with the carriage to deposit the work or articles to be treated on the carriage in the outermost position of the latter and also operable to lift the articles off of the carriage after the articles are withdrawn from the furnace by the carriage.

It is a further object of this invention to provide a work supporting platform of the above type which serves as an elevator to lower the articles into and remove the same from a quenching tank supported beneath the platform.

It is a still further feature of this invention to provide improved burners arranged and operated to assure maintaining a uniform temperature within the heating chamber of the furnace.

In addition to the above this invention provides an arrangement wherein the exhaust from the burners induces a flow of air upwardly in heat conducting relation to an outer wall of the furnace to cool the latter wall.

The foregoing as well as other objects will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a sectional view taken on the line II of Figure 2;

Figure 2 is a sectional view taken substantially on the plane indicated by the line 2-2 of Figure 1;

Figure 3 is a sectional view taken on the line 3--3 of Figure 1; and

Figure 4 is a sectional view taken on the line 4-4 of Figure 1.

The heat treating apparatus selected herein for the purpose of illustrating the present invention is particularly adapted for use in heat treating articles while supported by suitable trays not shown herein. Upon reference to Figures 1 to 3 inclusive of the drawings, it will be noted that the numeral I0 designates a furnace having walls formed of a high heat resistant refractory material and cooperating to form a heating chamber I I within the furnace. One wall I2 of the furnace is formed with an opening I3 therethrough intermediate the top and bottom furnace walls I4 and I5 respectively. The opening I3 is of sufficient size to enable trays supporting the work to be heat treated to be introduced into and removed from the heating chamber II.

The interior of the chamber II is heated to the desired temperature by a plurality of radiant type burners I6 supported within the chamber II below the access opening I3. In Figure 2 of the drawings, three burners I6 are shown, although it will be understood that the number of burners may be varied to suit different requirements. As shown in the specific embodiment of the invention selected herein for the purpose of illustration, the burners are spaced equal distances from each other lengthwise of the heating chamber l I, and respectively project through openings formed in the side wall I! of the furnace.

The burners I6 are identical in construction, and a description of one will suflice for all. As shown particularly in Figure 1 of the drawings, the burner comprises an inner tube I 8: formed of a high heat resistant material and an outer tube I9 also formed of a heat resistant material. The internal diameter of the outer tube I9 is substantially greater than the external diameter of the inner tube I8, and the two tubes are supported in concentric relationship to provide an annular passage 29 therebetween.

The outer tube is supported on the bottom wall I5 of the furnace by laterally spaced refractory blocks 2|, and the inner tube I8 is supported at its inner end by a spacer 22 located at the inner end of the outer tube I9. The outer end of the tube I9 projects through an opening 23 in the wall I! of the furnace, and the inner end extends to a position immediately adjacent the opposite wall I2 of the furnace. It will be noted from Figure l of the drawings that the outer end of the tube I9 is open to the atmosphere, and

the inner end of this tube is closed by a wall 24.

The inner end of the tube 53 is open, and terminates short of the wall 24 to provide communication between the annular passage and the interior of the tube 18. I'he outer end of the tube is projects outwardly beyond. the corresponding end-of the tube is, and communicates with a source 25 of fuel supply. In the present instance the fuel supplied to the inner tube I8 is in the form of a combustible mixture of gases which are burned within the inner tube It. The products of combustion issuing from the inner end of the tube 18 are caused to flow outwardly through the annular passage Edi, and are discharged through the open outer end of the tube 19. Inasmuch as the tubes extend practically from one wall of the heating chamber to the opposite wall, it follows that the interior of the chamber H is uniformly heated from wall to wall.

' The exhaust gases issuing from theouter end of the tube l9 are dischargedinto a stack 25 having a width approximating the length of the wall I? and spaced laterally outwardly from the wall Ii. The upper end of the stack communicates with the atmosphere beyond'the top of the furnace, and the lower end 21 or the stack projects for some distance below .the burners. .The inner wall. 2d of the stack. cooperates with. the wall it of the furnace to form a vertical. passage 25 having the lower end'3ll communicating with the atmosphere at a point spaced below the burners.

It will be noted that the outer end of the tube It! projects through the airpassageit into the stack 25 so'that the exhaust gases are discharged directly into the stack.

The upper .end ottbeairpassage 29 is open to the atmosphere immediately adjacent .the corresponding end of the stack26, so that exhaust gases flowing upwardly. through the stack induce the flow of air upwardly through the passage 29.

Air flowing upwardly through "the passage .23

absorbs heat from the adjacent wall of the furnace, and tends to maintain this wall relatively cool.

The work to be heat treatedisintroduced into and removed from the-heating chamber i l by a carriage 3| comprising laterally spaced racks 32. As shown in Figures 1 and 2 of the. drawings the racks 32 extend transversely of the :heating chamber H above the burners l6, and project out of the furnace l through the opening. it.

Referring now to Figure 3 of the drawings, it will be noted that the racks 32 are respectively supported withinthe heatingchamber on leterally spaced columns 33, and also on thebottom side 34 of the opening l3 in the manner shown in Figure 1 of the-drawings. Each. rack: comprises laterally spaced rails 35'connected-together by pins 3G extending between the rails and space from each other in the direction of length of the rails. The bottom. edges of therails-are bent laterally outwardly to provide flanges, and the flanges slidably engage plates 3'! respectively-secured to the upper endsrofthe-columns 33.

The above arrangement issuchiasv to permit sliding movement ofthe racks into and out of the heating chamber through the opening it. In the present instance the racks are moved as a unit by a pair of toothed wheels 33 located at the outer side of the furnace and secured to a drive shaft 39 irrpositionsto: respectively engage the racks. .The drive shaft38l is suitably journalled in bearings supported by the side wall 12 of the furnace, and is rotated in opposite directions by suitable driving mechanism 40 shown in Figure 2 of the drawings.

During the heating operation it is usually desired to maintain a nonoxidizing atmosphere within the heating chamber I, and accordingly, the opening I3 is normally closed by a door i2 suitably supported at the outer side of the wall viding a vestibule 50.

I2 and adapted to rest on the-top surfaces of the racks 32 when in its closed position. The door 42 is power operated, and for this purpose, the top of the door is connected to driving mechanism 43 by a flexible member 44. Also a nonoxidizing gas is introduced into the heating chamber ll through a conduit 45 at such a rate that the interiorof the chamber is flooded with the desired gas at all times, and any tendency for air to escape into the chamber around the dooris prevented.

The escape of air into the heating chamber l I when the door 42 is open is prevented by.pro-

The vestibule 5G is suitably supported at the outer side of. the wall 12 of the furnace directly opposite the opening: Iii, and provisionis made for flushing the vestibule with furnace atmosphere or some other suitable inertgas in order to maintain a nonoxidizing atmosphere therein. The inner side of the vestibule is provided with an opening 5! in registration with the opening l3, and one end 52 of the vestibule has an opening 53, as shownin Figure 2 of the drawings. The opening 53 enables the articles to be heat treated to be introduced into the vestibule, and is normallyclosed by a counterweighted door 54 shown in Figure 4. It will also be noted from Figures'2 and 4 of the drawings that a table 55 is suitably supported at the outer side of the door 54 in a position to support the article holding trays prior to introducing the same into. the vestibule 50.

Located within the vestibuletil directly cp posite the opening [3 is a platform 55. "The platform 561 extends transversely of. the racks '32 and comprises a plurality of rolls 51. As shown in Figure 2..the rolls" 5'! extend in the direction of length ofthe racks32 and are spacedfrom each other longitudinally ofthe platform. The opposite ends of the rollsS? are rotatably supported on side rails 58 of the platrorm,-and the rails. 55 are formed. with slots. 59. The slots 59 open through the top edges of the rails and are aligned with the racks? 32. V

The rolls 51 on the platform provide a. supporting surfaceforthearticles to beheat treated, and are normally-positioned by the platform with the work supporting surfaces elevated Withrespect to the work supporting surfaces of the racks 32. As shown in Figure 2 of thedrawings, the slots fidare locatedbetween adjacent rollers" 51 and provide clearance spaces for receivingthe racks 32 when the latter are moved out of the heating chamber II. In .this connection. it is pointed-out that the outer endsof the racks are supported in the outermost position of the racks by channels 30 supported by suitable, framework Bi at the outer side of the platform 56.

The platform 56 also serves asan elevator to lower the workinto and raise the same from a quenching tank 62. As shownjin Figure 1 of the drawings, the quenching tank 32 is supported at floor level directly below the p1atform 55,and vertical guides 63 are provided for guiding the platform into and out of the quenching tank. Inlthe present'instance the platformis operated by power means 64 shown in' Figure 4 as comprising a drive shaft 65 and a pair of sprockets 66. The drive shaft is iournalled on suitable frame structure at the top of the vestibule 50, and is suitably connected to reversible drive mechanism 61. The sprockets are respectively supported at opposite ends of the platform, and are connected to the latter ends by suitable chains 58. The above construction is such that rotation of the sprockets 66 in one direction lowers the platform into the quenching tank 62 and rotation of the sprockets E6 in the opposite direction raises the platform out of the tank 62.

The tank 62 is adapted to contain the desired quenching liquid, and in accordance with conventional practice, the liquid within the tank is circulated by a high volume pump designated generally by the reference character 69. This particular construction is of orthodox design, and is therefore not described in detail herein.

Operation Assuming that it is desired to introduce a tray containing articles to be heat treated into the furnace Ill, the Operator merely manually opens the door 5 1 to the vestibule 5d and moves the tray onto the platform 56. This operation is greatly facilitated by virtue of the rollers 55 and 51. The door 5a is then closed and a switch (not shown) in a suitable electric control system is closed to start a timer for the desired preset cycle. bule of substantially all oxygen, carbon dioxide and water vapor by displacement or reaction with the atmosphere gas entering the vestibule from the furnace chamber ll. At the conclusion of this time cycle the power means 43 is operated and the door 42 is raised. The driving means ti! is then placed in operation to move the racks 32 out of the heating chamber H through the opening I 3 in the furnace.

As the racks 32 are moved outwardly, they pass through the clearance spaces 59 beneath the tray or work supporting surface of the platform, and the latter is lowered by the power means 64 to deposit the articles or tray on the racks. The racks 32 together with the articles to be heated are then moved into the heating chamber I I, and the door 42 is closed. The heating cycle is then initiated, and the articles supported by the tray are heated to their proper temperature.

At the end of the heating cycle the door 42 is again opened by the driving mechanism 43, and the driving means to again moves the racks 32 to their outermost positions. It will be understood that the platform 55 is positioned below the elevation of the racks when the latter are moved outwardly to transfer the heated articles from the furnace into the vestibule 50. The platform as is then moved upwardly by the driving means 34 and the heated articles are transferred from the racks 32 to the platform 56. After this is accomplished the racks 32 are returned to their operative positions within the furnace chamber H, and the door 42 is closed.

After the door 42 is closed, the elevator 56 is moved downwardly by the driving means 64 to lower the tray containing the heated articles into the tank E2. The pump 69 in the tank circulates the quenching liquid around the articles in the usual manner, and upon completion of the quenching cycle, the platform 56 is again raised to its uppermost position shown in Figure 1 of the drawings. The operator then opens the door 54 and removes the heat treated articles from the vestibule 50.

All of the above operations are preferably This cycle is sufilcient to flush the vesti- 6 carried out in'se'quence by suitable electrically controlled mechanism including the proper timers. Such control panels are commonly used in this art, and form no part of the present invention.

In the above operation it is to be noted that from the time of completion of heating the work on one tray in the heating chamber ll until another tray is introduced into the heating chamber, there is an elapsed time consisting of three basic phases which are:

1) Time required by quenching operation (controlled by a time clock in the electrical control system) (2) Time required to pull out a tray from the vestibule and introduce another tray into the vestibule; and

(3) Time required for flushing the vestibule (also controlled by a time clock in the electrical control system).

During the time no work is being heated in the heating chamber, the operating temperature is preferably automatically increased in order to store heat in the furnace lining. In other words during the elapsed time of quenching, loading, reloading and flushing, heat is stored in the furnace chamber walls. This stored heat is subsequently abstracted from the furnace walls, and serves to decrease the time required to heat the work introduced into the heating chamber on the next cycle of operation.

It will be noted from the foregoing that the heat treating apparatus as a whole is very simple and compact. It will further be noted that the design of the heat treating apparatus is such as to enable supporting the quenching tank at floor level, which greatly simplifies installation of the apparatus. Aside from the above, it will be seen that the heating means provided in the furnace is highly efficient, and assures maintaining a uniform temperature throughout the chamber l i.

What I claim as my invention is:

1. Work handling mechanism comprising a carriage supported for generally horizontal movement between first and second positions, means for moving said carriage between said positions, an operating station at the first position of said carriage, a platform positioned at the second position of said carriage and having a work supporting surface spaced above said carriage, said platform and carriage being formed to permit move ment of said carriage to its second position beneath the work supporting surface of said platform and enabling downward movement of said platform relative to said carriage in the second position of the latter, means for lowering said platform to transfer work from said platform to said carriage and for raising said platform to transfer work from said carriage to said platform, and a second operating station supported beneath the second position-of said carriage in a position adjacent said platform when the latter is thus lowered.

2. Work handling mechanism comprising a carriage supported for generally horizontal movement between first and second positions, means for moving said carriage between said positions, an operating station at the first position of said carriage, a platform positioned at the second position of said carriage and having a work supporting surface spaced above said carriage, said plat form having clearance openings permitting passage of said carriage to its second position beneath the work supporting surface of said platform and enabling downward movement of said 'platfonn' relative-tosaid' scarriagezin the: second position: of thezlatter, means for 'loweringvsaid transfer work from said carriage to .saidplatform, and a :second operating station supported 7 beneath the secondiposition'v of. :said carriage in a positionadjacent said platform when the latter=is .thuslowered.

3..The':structure as defined: in claim 2, said carriage comprising laterally spaced racks extending in the direction of;movement. thereof and said platform comprising rolls extending in the direction of length of said racks in offset' relation to the paths of movement of said racks.

1 4.: -Workhandling mechanism for use with heat treating apparatus having a furnace provided with aheating chamber and an access opening through one side wall, saidmechanism comprising a carriage supported for movement through the opening between" first and second positions respectively within and Without the chambe =means forthus moving said carriage, a platform positioned at the-second'position of saidcarriage andhaving a...work:- supporting surface spaced Y above :said carriage, said platform" having upwardly opening clearance spaces permitting passage of sa'id'carriage to its-.lecond position beneath' the work supporting surface of saidplattransfer'work from said carriage to' said platform,- and a quenching 'tank' supported beneath ;8 thesecond position of said carriage-in a position to receive said-platform andithe work'supported thereby when the platform isthus lowered.

5. The structure as defined in claim 4, in which said carriage 1 comprises laterally spaced racks extending in the direction of movement thereof, and in which said platform comprises rolls extending intthe. directionof length of said racks in offset relation tothe paths of movement of said racks.

.WALTER H. HOLCROFT.

:References Citedin the file of this patent UNITED STATES PATENTS Number Name Date 357,234 Sargent Feb. 8, 1887 671,989 .Diescher et al Apr. 16, 1901 1,168,313 Kenworthy Jan. 18, 1916 1,460,323 Hodges June 26, 1923 1,4689% Hogenson Sept. 25, 1925 1,531,407 Johnson Mar. 31, 1925 1,550,340 'Cannon Aug. 18, 1925 1,702,524 Schoonmaker et a1. Feb. 19, 1929 1,979,108 Ipsen Oct. 30, 1934 2,086,970 'Wilson July 13, 1937 2,223,603 Dal-rah Dec. 3, 1940 2,589,811 Holcr'oft Mar. 18, 1952 FQREIGN PATENTS Number Country Date 1,490 "Great Britain Jan. 31, 1887 29,326 Great Britain Dec. 20, 1912 380,761 Germany Sept. 11, 1923 639,716 Germany Dec, 12, 1936 649,816 France Sept. 10, 1928

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