US2917297A

US2917297A - Atmosphere furnace

Info

Publication number: US2917297A
Application number: US596236A
Authority: US
Inventors: Henry W Schramm; Warren H Tollefsrud; Alfred G Parkes
Original assignee: Surface Combustion Corp
Current assignee: Surface Combustion Corp
Priority date: 1956-07-06
Filing date: 1956-07-06
Publication date: 1959-12-15
Anticipated expiration: 1976-12-15

Description

Dec. 15, 1959 H. w. scHRAMM ETAL 2,917,297

ATMOSPHERE FURNACE 2 Sheets-Sheet 1 Filed July 6, 1956 Dec. 15, 1959 H. w, SCHRAMM ETAL 2,917,297

ATMOSPHERE F'URNACEv Filed July 6, 1956 2 Sheets-Sheet 2 faz Lea \6/ 68j n INVENTORS #EA/ey d Sammy/n By 042254/ H. EnH-'sean v made very dificult.

United States Patent C)y ATMOSPHERE FURNACE Henry W. Schramm, Warren H. Tollefsrud, and Alfred G. Parkes, Toledo, Ohio, assgnors to Surface Combustion Corporation, Toledo, hio, a corporation of Ohio Application July 6, 1956, Serial No. 596,236

8 Claims. (Cl. 263-21) through.

Although oscillating and vibratory conveyors have been v`used in furnaces for a number of years, the use of such lconveyors in furnaces containing atmosphere gases has not been practically accomplished. This is principally due to the difliculty in maintaining a satisfactory atmosphere in the furnace, and more particularly due to the thermosiphon effect in that portion of the charge end opening below the conveyor, wherethrough atmospheric air enters the furnace to contaminate the atmosphere and the work.

With the constant or intermittent conveyor motion, the problem of sealing the underside of the conveyor is A furnace and entry seal structure therefor have been devised which, by effectively sealing the furnace opening below the conveyor, substantially eliminates the thermosiphon effect noted and thus allows practical maintenance of the desired furnace atmosphere.

For further consideration of what is novel and the invention refer to the drawing, the following specification, and claims.

'In the drawing:

Figure 1 is an elevational, cross-sectional view on line v11 of Figure 2 of a furnace embodying the invention,

v Figure 2 is a cross-sectional view on line 2-2 of the furnace of Figure 1,

Figure 3 is a detailed, cross-sectional view of a portion of the apparatus of Figure 1,

Figure 4 is a detailed, cross-sectional view on line 4-4 of Figure 5 of another portion of the apparatus'of Figure l,

Figure 5 is a partially sectional end view of the apparatus of Figure 4, and j l Figure 6 is a view of an alternate of the apparatus of Figure 4.

The furnace 11 of Figures 1 and 2 comprises a heating chamber 12 defined by

refractory walls

13, 14, 15 and 16 supported on suitable beams 17. A movable conveyor or trough 18 extends through an opening 20'in wall 14. The. conveyor 18 is movably supported by rods 21 having rings22 into which projections 23, attached to conveyor 18, extend. Outside the furnace, the rods 21 support the vconveyor by means of cylinders 24 and mountings 25.

The rods are supported by a fabricated beam 26 comprising two channels 27 and a plate 28 which are mounted on casing 29 of wall 13. Each rod 21 extends through an elongated hole 30 in refractory wall 13, through a refractory fiber packing 31, through a ball 32 and socket 33, and through spring 34. The latter is confined between

members

35 and 36 and is held down by nuts 37 on threaded portion 38 of rod 21.` This arrangement permits the conveyor 18 to freely move to and fro in a direction parallel to the longitudinal axis of the furnace and still maintain a gas tight construction. The use of the springs permits yand also the work on the conveyor.

tubes.

"ice

the weight of the conveyor to be more evenly distributed among the rods 21 than would otherwise be possible.

Chamber 12 is heated by means of two U-shaped radiant tubes 40 and a W-shaped radiant tube 41. The U-shaped tubes are horizontally disposed on each side of conveyor 18 with the firing leg 42 placed below the conveyor and the exhaust leg 43 above it. The tiring leg is equipped with a burner 44 and the exhaust leg with an eductor 45. W-shaped tube 41 is disposed at the end of conveyor 18 and has a burner 46 and eductor 47. This arrangement of the radiant tubes permits a maximum heat input with a minimum space requirement.

The placement of the U-shaped tubes with their firing and exhaust legs respectively located above and below conveyor 18 and parallel thereto affords maximum and uniform heat transfer therefrom to the work.

The heat is thereby concentrated near the bottom of the furnace since the tiring leg of a radiant tube lis the hotter leg, the majority of the combustion occurring in it. This allows more heat to be conveyed to the bottom of the conveyor which transmits the heat to the work by radiation and conduction. This is especially important where small parts are heat treated which are piled several inches deep on the conveyor. The upper pieces of this layer are easily heated by radiation from the upper portion of the furnace chamber but the pieces that are lower in the layer cannot be heated by this radiation and thus depend on the conveyor itself for much of the heat. It is therefore important that the conveyor receive adequtae heat which is accomplished with the aforesaid arrangement.

The tiring leg of the radiant tube is also close to chute 54 which transmits more heat thereto. It is desirable to maintain the chute at a high temperature to reduce the black body effect which this end of the furnace is subjected to from the cold area outside the furnace with which the chute is connected. This has a substantial effect in reducing the temperature of the discharge end of the chamber By this placement of tubes 40, more heat is transferred to the chute and the black body effect is maintained at a minimum. The W-shaped radiant tube 41 is also placed at the discharge end to overcome the effect and maintain a more even temperature longitudinally in the furnace chamber. This tube could also be placed horizontally below the roof of the chamber or be vreplaced by two U-shaped radiant U-shaped radiant tubes are generally not as efficient in shorter lengths and it is therefore preferable to use the W-shaped radiant tube at this end of the furnace.

Conveyor 18 is actuated by an arm 48, pivoted at 50, and moved by a cam 51 which is rotated through a gear reducer 55 by a motor 56. A spring 52 maintains arm 48 securely against the cam 51 and thrusts conveyor 18 forward to be abruptly stopped by bumper 53, inertia of the work causing the work to slide forward on the conveyor. When the work reaches the end of conveyor 18, it falls down chute 54 to a quench tank, conveyor, or other means of disposal. The rate of travel of the work on the conveyor can be regulated by the speed of cam 51, the tension of spring 52, and the design of cam 51.

Bumper 53 is slideable on rails 101 and is maintained in position by springs 102 attached to rod 103 at their outerv ends. The rod is secured to vertical beam 104 and may be adjusted therewith to adjust the position of bumper 53 on. the rails 101 which further regulates the rate of travel of the work on the conveyor. vA spring and rod arrangement is located on both sides of bumper' mixturefrom being formed with the air. prevent the influx of air below the conveyor, the only 'aiiixed thereto.

pressed and the lower the conveyor 18 will be. Opening 2i) must be large enough to assuresuliicient clearance of the conveyor at its heaviest loads in order not to dampen the effect of the oscillating mechanism. With this situation, a substantial 'gap will be present between therbottom of the conveyor andthe adjacent portion'of wall 14 deiining the lowerportion of opening 20 when the conveyor is lightly loaded. The location of the gap'permits a substantial influx of air into chamber 12 rsince, although the chamber contains atmosphere gas under pre..- sure from inlets 57, the gas is at lower pressure in this portion of the chamber, due to a thermosiphon action, resulting in a constant outow of gas between the upper side of conveyor 18 and the portion of wall 14 dening the upper portion of opening 20. The outflow of gas is no problem, if not excessive, since it can be continually ignited and burned to prevent a dangerouslyexplosive However, to

remedy is to provide a substantially gas tight seal. This -is vditiicult to accomplish, since the conveyor issubstantially constantly subject to oscillating motion and is further subject to a varying vertical level due to a varying load therein.

The seal of Figures 4 and 5 has been particularly devised to meet this problem. Accordingly, a plate 61, attached to casing 62has an L-shaped projection 63 An asbestos gasket 64 is provided between this plate and casing and extends close to conveyor l1%entirely around opening 20 to further provide a sealing Velfect.

An inverted U-shaped member 65 is slideably fitted between the plate 61 and the vertical leg of projection 63. The member 65 is designed to gas-tightly contact the underside of conveyor 18 by means of k'lever arms 66. The lever arms are pivoted at their central portions by bolts 67 in holders 68-which may be'attached to the ends of projection 63 or some other fixed support. The'ends of the lever arms closer to the furnace then contact member '65 either directly or through rods 70 placed therebetween and welded to the member. The outer ends of the arms are provided with counterweights 71 attached by hangers 72. rThe weight of counterweights 71 is determined by the force needed to maintain 4an effective seal between member 65 and the underside ot conveyor 18. However, the weight should not be so large as to dampen the movement of the conveyor. ltA will be vseen lthen, that due to the counterweights, member 65 will always remain in contact with the conveyor despite any vertical movement of it due to a change in the load. The member will be restrained from horizontal movement with the conveyor by means of the plate y61 and the vertical leg of projection 63.

Acover 73 is preferably attached to thesides of conveyor 18 and another member 74, similar to member 65, is placed in contact therewith. This member is prevented from horizontal movement by angle iron 75 and the upper portion of plate 61, the former being held in spaced relationship with the latter by bolts 76.

Plates

61 and 62 are attached to frame 77, by bolts (not shown), which is welded to casing 7S of Wall 14. By the use or" this upper seal, for which no counterweights'are necessary, a constant opening is maintained between cover 7-3 and the horizontal portion of conveyor 18 or between the latter and an asbestos curtain 80 attached to cover 73 by strip 84.

A manifold pipe S1 is located at the outer edge of cover 73 with ports S2 directed downwardly. The pipe contains air under pressure which is emitted from the ports to mix with the combustible atmosphere gas that escapes from the opening. This mixture then is ignited by pilot 83 and burns closel to the opening, affording an elective deterrent to air entering the opening. With the conventional seals, no air jets are provided with the result that the combustible atmosphere gas slowly mixes *with the outside air to produce a longer, lazy ame.

`the "dame, between the ame and the horizontal portion of conveyor 13. The air from pipe S1 not only causes burning of the atmosphere gas closer to the opening but also forces the resulting llame to travel closer to the horizontal portion of conveyor 1S. These two factors prevent substantially any air or products of combustion from entering the opening. Pipe 81 and pilot 83 are omitted from Figure 5 for greater clarity of illustration.

An alternate seal is shown in Figure 6. Here a similar lower .seal is provided with the exception that arm 66 maintains member 65 against conveyor 18 by means of a spring 91 rather than by counterweight 71. In the upper portion ofthe opening,

asbestos curtains

92, ,3 and 94 are provided between plates v'61 and 62, frame 77, and cover 95, the cover and plates being attached to the frame by bolts 96. This arrangement is more simple but allows the opening between the curtains and the horizontal portion of conveyor 18 to vary as the conveyor moves upand down due to a change in the load it carries. Thisresults in anunnecessarily large opening when the conveyor is fully loaded which tends'to allow air to enter the furnace chamber.

The above examples are the best modes known of carrying out the invention, the scope of which is intended to be limited only by the depending claims.

We claim:

1. A furnace comprising: wall means deninga charnber; Van elongated conveyor extendng through an opening in said wall means and at least part lway through said chamber; a U-shaped radiant tube located horizontally in said chamber with the tiring leg located below the exhaust leg, said legs being parallel to said conveyor, the exhaust'leg being above said conveyor and the firng leg being below said conveyor; and sealing means between at least a portionof said wall means surroundingsaid opening and said conveyor.

2. A furnace comprising: wall means defining a'chamber; an'elongated conveyor extending through'an opening in said wall means and at least partway through said chamber; a dscharge chute located under the discharge end of the conveyor and connected to an area outside the furnace through a wall thereof; a U-shaped radiant tube located horizontally in said chamber with the firing leg located below the exhaust leg, said legs being parallel to said conveyor, the exhaust leg being above said conveyor and the tiring leg being below said conveyor; a second radiant tube located in a vertical plane adjacent the discharge end of sad conveyor; and sealing means between at least a portion of said wall'means surrounding said opening and said conveyor.

3. A furnace comprising: wall means defining achamber; an oscillating conveyor extending through an `opening in said wall means and part way through saidchamber;`a pair'of U-shaped radiant tubes located horizontally in said chamber, each being parallel to, and on opposite sides of said conveyor, with one of the iringand exhaust legs of each radiant tube being located directly above the otherysaid legs being parallel to said conveyor, and one of said legs being above said conveyor and one being below said conveyor; a W-shaped radiant tube located adjacent to the discharge end of said conveyor and being in a plane perpendicular to the-path of work in said conveyor, the outer two legs of said W-shaped radiant tube extending through the roof of said chamber, with one of the outer legs being a tiring leg and the other of the outer legs being an exhaust leg; and sealing means between at least a portion of said wall means surrounding said opening and said conveyor.

4. A furnaceV comprising: wall means dening a cham ber; an oscillating conveyor extending through an opening in said wall means and atleast part way through said chamber; a series of substantially vertical rods connecting said conveyor to that portion of said wall means forming the roof of said chamber, said rods being supported by said roof through springs; a U-shaped radiant tube located horizontally in said chamber with one of the ring and exhaust legs located above the other, said` legs being parallel to said conveyor, and one of said legs being above said conveyor and one being below said conveyor; and sealing means between at least a portion of said wall means surrounding said opening and said conveyor.

5. A furnace comprising: wall means defining a chamber; an oscillating conveyor extending into said chamber through an opening in said wall means; a plurality of substantially vertically disposed rods whose lower ends are pivotally connected to said conveyor at spaced intervals, said rods extending upward through elongated holes in that portion of the wall means defining the roof of said chambers; a sealing box containing refractory ber surrounding that portion of each rod where it projects through the roof; a ring attached to the upper end of each rod above said sealing box; a socket attached to said box and surrounding that portion of each rod extending upwardly through, and adjacent to, said box; a semi-spherical member surrounding that portion of each rod immediately above said socket, said member cooperating with said socket; a spring located between said ring and said semi-spherical member, whereby all the weight of said conveyor is supported on said springs; and sealing means for sealing that portion of the opening below said conveyor.

6. In a furnace having a chamber and an oscillating conveyor extending through an opening in a wall of said chamber and having a substantially flat underside at the portion adjacent said opening, a seal located between the underside of said conveyor and the adjacent wall cornprising: an inverted, substantially U-shaped member; an

L-shaped projection whose horizontal leg is attached to the wall below said opening, said member being located in the volume dened by said projection and said wall, the vertical legs of said member contacting the vertical leg of said projection and the adjacent wall, and the horizontal leg of said member being adapted for contacting the underside of the conveyor; a horizontal lever arm pivoted at a middle portion, one end of which contacts said member; and a counter weight attached to the other end of said lever arm.

7. In a furnace having a chamber and an oscillating conveyor extending through an opening in a wall of said chamber and having a substantially iiat underside at the portion adjacent said opening, a seal located between the underside of said conveyor and the adjacent wall comprising: an inverted U-shaped member, whose intermediate portion is in a horizontal plane; an L-shaped projection whose horizontal leg is attached to the wall below said opening, said member being located in the volume defined by said projection and said wall, the vertical legs of said member contacting the vertical leg of said projection and the adjacent wall, and the horizontal portion of said member being adapted for contacting the underside of the conveyor; a horizontal lever arm pivoted at a middle portion, one end of which contacts said member; and means for maintaining a downward force on the other end of said lever arm suicient to maintain said member in contact with said conveyor.

8. In a furnace having a chamber and an oscillating conveyor extending through an opening in a wall of said chamber and having a substantially flat underside at the portion adjacent said opening, a seal located between the underside of said conveyor and the adjacent wall comprising; an L-shaped projection whose horizontal leg is attached to the wall below said opening; a sliding member located in the volume defined by said projection and said wall, said sliding member having opposed surfaces contacting the vertical leg of said projection and the adjacent wall, and having a surface being adapted for contacting the underside of the conveyor; a substantially horizontal lever arm pivoted at a middle portion, one end of which contacts said sliding member; and means for maintaining a downward force on the other end of said lever arm sulicient to maintain said member in contact with said conveyor.

References Cited in the iile of this patent UNITED STATES PATENTS 59,989 Evertson Nov. 27, 1866 586,910 McDonald July 20, 1897 655,513 Proctor Aug. 7, 1900 1,695,950 Carpenter Dec. 18, 1928 1,941,560 Lee Ian. 2, 1934 2,021,072 Machlet Nov. 12, 1935 2,093,381 Munford Sept. 14, 1937 1.671,655 Osterman et al. Mar. 9, 1954