US1792074A - Heat-treating furnace - Google Patents

Description

Feb. 10, 1931. R. COCHRAN 1,192,074

HEAT TREATING FURNACE Filed Oct. 5. 1928 2 Sheets-Sheet- 1 [1v VEN Tara.-

RS. CULT/{RAN ATTURNE Feb. 10, R a CQCHRAN HEAT TREATING FURNACE Filed Oct. 3. 1928 2 Sheets-Sheet 2 INVENT'DR; CUC'HRAN' ATTORNEY Patented Feb. 10, 1931 UNITED STATES PATENT OFFICE 4 RAID]? SMYTH COCHRAN, OF TOLEDO, OHIO, ASSIGNOR TO THE SURFACE COMBUSTION ('20., INCORPORATED, OF TOLEDO, OHIO, A CORPORATION OF NEW YORK HEAT-TREATING FURNACE Application filed October 3, 1928. Serial No. 310,031.

This invention relates'to furnaces for heattreating relatively flat objects such as sheet steel and has among its objects to provide an interfingered conveyer of such form and construction that the sheet resting on the conveyer can be heated on its under side by gases of combustion from burners firing crosswise of the direction of travel of the sheets and to provide ways and means for preventing the unsupported side edges of the sheet from sagging.

The above and other objects of the invention will more fully appear from the detailed description taken in connection with the accompanyingdrawings forming part of this specification. r I

.Referring to the drawings:

i Fig. 1 is a side elevation of a portion ofa heat-treating furnace embodying my improvements, parts being broken away to more fully show the construction;

Fig; '2 is a more orflless diagrammatic sectional lan view on a reduced scale of the lower portlon of the furnace shown in Fig. 1

Fig. 3 isa-- transverse vertical section through the furnace shown in Flg. 1;

Fig. 4 is a fragmentary vertical/ section on an enlarged scale of the constructlon shown in Fig. 3;

Fig. 5' is a fragmentary plan viewshowmg the relative position assumed by the adjacent relatively movable conveyer bars when they are in such position that the burden of the work or sheets is about to be transferred from one set of bars to the other; and

Fig. 6 is a side elevation of one of the elements forming part of each conveyer bar.

The furnace is of tunnel form with substantially continuous side walls 10and roof 11' and with end openings E through which the material to be heat-treated is advanced to'and from'the furnace'chamber. A horizontally extending series of openings in the sidewalls allow for the positioning of gas burners 12 and 12 of any approved type but preferably of a type adapted to burn explo-.

v 'sive gaseous mixtures. There is no stack, the

spntiproducts of combustion finding egress through the end openings E.

Thel'hearth of the furnace is a conveyer which consistsof two sets of longitudinally drawings, the set of bars 13 is elevated, that is to say in sheet supporting position, a sheet being indicated at S. It will be understood that when in such sheet-supporting position; the bars are advancing, that is they are moving longitudinally within the furnace-chamher in the direction from intake to discharge.- After the advancing bars 13 have carried the sheets forward through a predetermined distance, the relative vertical movement between the two sets brings the bars to a level with the bars 14.1 The bars '13 then descend and the bars 14 take the bur-den ofthe sheets. The bars 13, whenthey have come to a relatively lower position, recede, and after recession rise again to take the burden of the sheets and to carry them again forward. The cyclic motion of the two sets of bars is identical. I

Each of the bars 13 and 14 is relatively high as compared with its width and each bar is provided with a longitudinally extending series oftransversely extending similar ports or openings13' and 14: respectively. The ports or bars 13 are in alinementv as are also the ports of bars 14 and the height and length of the ports of each set of bars are preferably such that regardless of the relav tive position between the two sets of bars, there may be an open passage through the ports from one side ofthe furnace to. the other. For convenience of description the series of communicating ports may be termed a bank of ports. Each bank of ports has its gas burner 12 (12') the burner. being so positionedas'to fire ina direction through the ports from one side of the furnace toward the other. The burners in one wall are staggered with respect to the burners in the opposite wall andhence the hot gases flow in opposite directions through adjacent port banks. During relative vertical reciprocation between the two sets of bars 13 and 14, the under side of the sheet S above the relatively lower set of bars will be exposed to the direct action of the hot gases. As shown in Fig. 4, some of the hot gases flow through the ports of the relatively lower bars and some flow over the tops thereof as a consequence of which the tops of the lowered bars Will'become thoroughly heated. As a consequence of i being thoroughly .heated while out of contact with the sheets, cold spots on the sheets will not be formed when the bars again take the burden of the sheets.

The inner face of each furnace side wall is provided with a longitudinally extending in cut or reentrant portion from a point adjacent the burners to a point above the highest level of the conveyer bars. For convenience ofv description one of these incuts is indicated level in. the opposite side wall is a burner (15) adapted to discharge fresh combustion products above the conveyer members and towards the wall in which the burners 12 (12) are positioned. The combustion products discharged from burners 12 (12) set up an entraining effect in front of the entrance to the port banks. Due to this entraining effect, the combustion products from the opposite burners 15 15) after striking the wall wherein the burners 12 (12) are positioned tend to be drawn through the port banks into which the burners 12 (12) fire. The hot gases from burners 12 (12) are therefore tempered by the relatively cooler entrained combustion products with a consequent more uniform temperature from one side to the other of the conveyer. The spent gases leaving the port banks tend to mix with the fresh hot combustion gases from the upper adjacent burners and therefore also temper them.

The top surface of the conveyer bars is preferably undulating in the direction of-the length of the bars as indicated by numeral 16, the undulations of the respective bars of a given set being in transverse alinement. By providing an undulatory sheet-supporting surface on the bars, the sheets tend to assume a corresponding undulatory form while supported on the bars. As is well known, a corrugated or undulatory sheet offers more resistance to bending on a line at right angles to the coi'rugations than a flat sheet. The advantage of imparting an undulatorv form to the sheets as they pass through the furnace chamber will be readily appreciated from the following description. If an unsupported side portion of the sheet S should sag there is danger of such portion becoming wedged between the bars as for example by projecting into a port opening 13 (14) adjacent the bar on which the sheet is supported or by wiping the side of the adjacent bar as the burden of the sheet is transferred from one set of bars to another. By giving an undulatory or corrugated form to the sheets any tendency of the sheets to sag and become wedged between the bars will be effectually prevented since the surface of corrugated form offers resistance to bending as will now be readily understood.

Another important result. obtained by stiffcning the sheets as aforesaid is that lateral displacement of the sheets on the bars is prevented; For example, if the sheet were not stiffened and an unsupported side portion thereof should sag and abut an adjacent relatively movable bar, said bar would tend to push or pull thesheetas the case may be and thus cause sliding movement of the sheet on the supporting bar s. Such sliding movement tends to scratch the sheets and thus to injure them for certain classes of work. The un- 'dulations in thctop surface of the bars therefore serve "a's' mean s for preventing relative lateral sliding movement between the sheets and the supporting bars.-

The undulations in one set of bars are so arranged with respect to those in the other set that when both sets are in a common plane,that is when the burden of the work or sheets is being transferred from one of said sets to the other,-the undulations of one set will be transversely alined with the undulations in the other set as illustrated'in Fig. 5. By arranging the undulations as aforesaid, repeated flexing of the sheet is prevented as it is transferred from one set of bars to the other. Relative sliding movement between the sheet and the conveyor bars is therefore prevented with consequent elimination of any tendency of scratching of the sheet due to such movement.

Each bar 13 (14:) is a composite structure and comprises a longitudinally extending base rail 17 (17) on which is mounted'a series of individual refractory rectangular blocks 18, the ports 13 (14) being formed one in each block as clearly shown in Fig. 6. The adjacent ends of the blocks are preferably of tongue and groove construction as indicated at 1 9 in Fig. 5. The top surface of the blocks is undulatory and forms the undulatory surface already referred to and may be capped by a metal cap 20 as indicated in Fig. 4. It is preferred to provide heat-insulating material between the rails and blocks as indicated at 21, the blocks and insulation being maintained against lateral displacement with respect to its' bar in an} suitable manner as by being seated in a U- shaped saddle 22 which is secured to the rail 17. In order to reduce, to a minimum any 35 rups 27 and 27', respectively, in the bottom the adjacent bars 13 and 14, there is-pro- 'vided in one side of the bars a longitudinally extending and laterally projecting friction member 23 composed of a refractory material. This member may be inset into the blocks 18 as shown.

The two sets of bars 13 and 14 may be supported for relative movement in any suitable manner. In the construction shown, the bars 13 and 14 are supported on a series of cross beams generally indicated by numerals 24 and 25 .respectively. In order to provide the necessary clearance between one set of rails and the cross'beams for the other set of rails, there is provided spacer blocks for supporting the rails in a plane above their supporting beams. The spacer blocks between the cross beams 24 and their rails 17 are indicated' at 24 and between the cross beams 25 and their rails 17' at 25'. As shown the blocks are short pieces, one for each rail andof the same cross section as the cross beams on which they rest. At intervals between the cross beams 24 and 25 are shorter cross beams 24 and 25 which terminate short of the side walls of the furnace chamber. The number of cross beams will of course depend on the length of the furnace.

The cross beams 24 and 25 extend through the side walls of the furnace chamber, the walls being provided with arched'openings 26 for that purpose. The outer ends of the beams 24 and 25 are seated in individual stirof each of which is a knife edge bearing 28 on which-the beams rest. Each stirrup is secured to the lower end of an upright hanger 29 (29') the upper end of which is pivotally connected to crank arm 30 (30) secured to a shaft 31 (31); These shafts are suitably secured in theupper ends of upright standards 32 which also serve as buckstays for the furnace walls.

Fixed to each shaft 31 (31) is crank arm 34 (34') and connecting these arms is a link 35 (35). To the end of one of the crank arms 30 is also connected a pitman 36 which leads to operating mechanism to be presently described. Aflixed to one of the shafts 31 is a crank arm 37 and connected with this arm is a pitman 38. The lower end of the pitman 38 connects with onearm 39 of 'a bell crank lever rotatably secured on a suitably supported shaft 40. The other arm 41 of said bell crank carries a roller which rides on a cam 42 fixedly secured to a power shaft 43 which'is driven in any suitable manner, not shown. The lower end of pitman 36 connects with one arm 44 of a bell crank rotatably secured to a suitably supported shaft 45.. The other arm 46 of the bell crank carries a roller which rides on the previously mentioned cam 42 at a point diametrically opposite the roller bars 13 and 14 as will now be readily under stood. 1

The means for imparting, relative horizon tal movement between the sheet supporting bars 13 and 14 will now be described. Rotatably secured on the shaft 40 is a lever thelower end 47 of which carries aroller which rides on a cam 48 which is fixedly secured to the shaft 43. Connected to the upper end 47 a of said lever is a pitman 49 which connects with-a pin on a standard 50 which is secured to cross beam 24. Anchored to the standard 50 is a cable 51 at the other end of which is a weight 52, the cable running over-a pulley 53. .The weight serves to hold the roller on lever arm 47 against its cam 48 and thus to cause i the one set of sheet-supporting bars 13 to return after having been moved in one direction by the cam 48 "ecured to the cross beam 25 for the other set of sheet-supporting bars 14 is a standard 54 corresponding to the standard 50. Se-

cured to the standard'54 is a pitman 55 the other end of which is secured to one arni 56 of a lever which is rotatably mounted on the I shaft 45. Projecting from the lever is an' arm 57 having a roller which rides on the cam 48, the rollers on arms 57 and 47 engaging the cam 48 at diametrically opposite points. An

chored to the lever arm 56 is a cable 58 at the other end of Which is a weight 59, the cable passing over pulleys 60an'd 61. The weight serves to hold the roller on arm 57 against its cam 48 and thus to cause the other set of sheet-supporting bars 14 to return after having been moved in onedirection by the cam 48. The weight of the mechanism supported by the hangers 29 (29) serves to hold the rollers on the lever arm 41 (46) in engagement with the cam 42 as will be readily appreciated.- Other mechanism for imparting relative horizontal and vertical motions to the sheet-supporting bars may be employed.

Another important. feature of the invention is the arrangement for maintaining cool the under side of the conveyor mechanism and for preventing ingress of air through the wall openings through which the cross beams 24 and 25 extend. The bottom or floor of the furnace is indicated at 62 and is considerably below the cross beams 24, 25, 24 and 25*. Where the cross beams 24 and 25 project through the furnace chamberwalls. the furnace floor is extended laterally as indicated by numeral 63. Walls 64 extend from the floor portion 63 above-the level of the arch 26 at the top of the opening through which the cross beams 24 and 25project laterally of the furnace chamber side walls 10. In the bottom of the floor is shown a drain 65 and in the walls 64 are an overflow pipe 66 and a furnace chamber is adapted to be filled with water to 1 level which is above the top of said side openings of which the arch 26 forms the top and through which the cross beams 24 and 25 project. The said openings are therefore sealed against the entry of air into the furnace chamber there being no other openings in the furnace chamber walls through which air may enter. The level of the water is" such that all of the cross beams which support the rails 17 and'17 will be immersed in the water and therefore kept cool.

The cam or power mechanism Ir ay be p0- sitioned in a compartment 68 outside of the furnace chamber as shown. For simplicity of showing, I have shown the power mechanism for imparting horizontal and vertical movement to the conveyer as at one side only of the furnace but it will be understood that such mechanism may be duplicated at the other side of the furnace or appropriate connections for that purpose made with the single cam mechanism shown.

It will be obvious that changes may be made in size, shape and arrangement of the Various parts without departing from the spirit of the invention and I wish therefore that the showing shall be taken in a sense diagrammatic.

\Vhatis claimed is:

1. In a heat-treating furnace, the combination of relatively movable sets of interdigitated work-supporting members for moving work through the furnace, ports extending crosswise through said members, burners positioned to direct hot combustion products through said ports, and means extending between said members below said ports for preventing flow of combustion products into a region below said members.

2. In a heat-treating furnace, the combination of interfingered members for moving work through the furnace, ports extending crosswise through said members, burners firing into the furnace through said ports, and means movable with said members for pre venting entry of atmospheric air into the furnace.

3. In a heat-treating furnace, the combination of two sets of longitudinally extending and interdigitated work-supporting members each set being movable, longitudinally spaced groups of ports extending crosswise through each of said sets in a manner to provide a continuously open flow path for combustion gases, and burners arranged to direct combustion gases through said ports, the burners being positioned in the opposite sidewalls of the furnace chamber in staggered relation whereby the flow of combustion gases through adjacent groups of ports is in opposite directions.

4. In a heat-treating furnace, the combination of movable members for moving work through the furnace, ports extending cross- 'wise through said members, opposed burners at different levels, the burners at the lower level firing into the furnace through said ports and the upper level burner firing over said members.

5. In a heat-treating furnace, the combination of relatively movable sets of interdigifated work-supporting members for moving work through the furnace, ports extending crosswise through said members, mutually opposed burners at different levels, the lower level burner firing into said ports and the upper level burner firing over said members in the opposite direction, and means for directing combustion products from the overfiring burner into the space initially traversed by the fresh combustion products from the burner which fires into said ports.

(5. In a heat-treating furnace,,the combina tion of relatively movable sets of interdigitated work-suppoizting members for moving work through the furnace, ports extending crosswise through said members, mutually opposed burners at diflerent levels, the lower level burners firing into said ports and the upper level burners firing over said members in the opposite direction, the furnace wall wherein the burner which fires into said ports is positioned being set back from the adjacent work-supporting'member to provide a space for the inflow of combustion products from above said members to the entrance to said ports.

7. In a heat-treating furnace, the combination of relatively movable sets of interdigitated work-supporting members for moving work through the furnace, ports extending crosswise through both of said sets, burners positioned to tire into the furnace through said ports, veach of said members comprising a longitudinally extending rail and a series of refractory blocks mounted on the rail, those blocks which are laterally alined with the burners being provided with ports as aforesaid.

8. In a heat-treating furnace, the combination of a work-supporting bend of longitudinally extending railsarranged side by side for. relative vertical and longitudinal movement, a passage extending transversely through said bed, and means for projecting heating gases into the furnace by way of said passage, the passage being formed by alined ports in said rails.

9. In a heat-treating furnace, the combination of a work-supporting bed of longitudinally extending rails arranged side by side for relative vertical and longitudinal movement, a plurality of passages extending transversely through said bed, burners firing into adjacent passages from opposite directions, each passage being formed by alined ports in said rails.

10. In a heat-treating furnace, the combination of a work-supporting bed of longitudinally extending rails arranged side by side for relative vertical and longitudinal movement, a passa e extending transversely throughsaid bed, a burner firing into said passage, and means tending to direct gases from the furnace chamber into the stream of burner gases entering said passage, said passage being formed by alined cross posts in said rails.

11. In combination, a heating chamber,

longitudinally extending interfingered members forming the hearth of said chamber, movable means on which said members are supported and means carried by said members below the top thereof to forma movable seal tending to prevent free in-flow of air into the chamber from below said members.

V 12. In combination, a heating chamber,

longitudinally extending interfingered mem- 2 bers forming the hearth of said chamber,

movable means on which said members are supported, and means projecting laterally from said member adjacent the bottom side thereof to form individual seals between adjacent members to prevent'free passage of lgases from one side to the other ofsaid memers.

13. A method ofpassing relatively thin metal sheets through a heating furnace in a manner to prevent the sheets from bending on lines running parallel with the direction of travel of the sheets comprisin imparting un dulatory form to the sheets during passage through the furnace, the undulations presenting a wave front transversely of the line of travel of the sheets.

1 A method of passing relatively thin metal sheets through a heating furnace in a manner to prevent the sheets from bending on 40 lines running parallel with the direction of travel of the sheets comprising supporting the sheets in such a manner that they as-' sume an undulatory form transversely of the line of travel of the sheets.

In testimony whereof I aflix my si ature.

, RALF SMYTH COG AN.

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