US2835485A - Grate bar for sintering machine - Google Patents

Description

May 20, 1958 F. c. WOODY 2,835,485.

GRATE BAR FOR SINTERING MAHINE Filed Dec. 15, 1955 2 Sheets-Sheet 1 May 20, 1958 F. c. WOODY GRATE BAR FOR SINTERING MACHINE 2 Sheets-Sheet Filed Dec. 15, 1955 \NN \NNI INVENTOR.

FPEQ c. Waaa BY ATTO/P/I/[V United States Patent GRATE BAR FUR SENTERING MAQHINE Fred C. Woody, Garfield Heights, Ohio, assignor to National Malleable and Steel (Tastings Company, Cleveland, @hio, a corporation of @ln'o Application December 15, 1955, Serial No. 553,323

7 Claims. (Cl. 266-41) This invention relates to sintering machines, and more particularly to a finger type grate bar therefor.

In sintering machines of the usual type there is an endless conveyor made up of a series of pallets on which grate bars are mounted. During operation of the machine, the conveyor carries the pallets to the discharge end where the pallets travel downwardly and the sintered material resting on top of the grate bed is discharged. The pallets then travel along a lower track back to the feeding end where they are lifted up by the conveyor to the upper level again to repeat the process. During the aforementioned travel along the lower track of the conveyor, the pallets are in an upside-down position. With the pallets in the latter position, some means must be provided to maintain the grate bars in assembled relationship with the pallets.

In United States Patent No. 2,322,873, issued June 29, 1943, to Wilson H. Moriarty, there is shown a finger type grate bar construction in which each bar has a pair of downwardly extending retaining lugs on the underside thereof. These lugs are disposed near the central portion of the bar, and are adapted to underlie centrally disposed stops on the pallets. Accordingly, as the pallets drop to upside-down position, the lugs on the grate bars engage the stops on the pallets, thus preventing the bars from falling out of assembled relationship with the pallets.

It has been found that in service the outer ends of the type of grate bar shown in the aforementioned patent have a tendency to warp upwardly, probably due to the repeated heating and cooling of the bars during sintering operations. This warpage of the bars is undesirable for various reasons, one being the resulting uneven surface of the grate bed. in addition, the warped outer ends of the bars sometimes become so positioned that they overlap adiacent bars, thus leaving gaps in the grate bed adjacent its outer edges. The lateral edges of the grate bars adjacent these gaps burn out and deteriorate much faster than the remaining portions of the bars, due to the increased passage of hot gases through these openings and also due to the abrasive wear caused by the sintered material dropping down through these gaps. Consequently, the bars do not wear uniformly throughout their full length and have to be replaced prematurely. Moreover, the material dropping down through the gaps in the grate is lost during the sintering process and creates an untidy state in the area surrounding the sintering machine. Furthermore, the sintered material lost from the grate causes increased wear on the circulating fan and duct system.

It is, therefore, a general object of the invention to provide a novel grate bar construction in which the bars do not warp in service.

Another object of the invention is to provide a grate bar in which the outer ends thereof will remain in a substantially horizontal position regardless of the length of time the bar is used in service.

A further object of the invention is to provide a finger type grate bar and associated pallet construction for a sintering machine, in which means is provided on the bar to eliminate the tendency of the outer ends of the bars to warp vertically away from the top surfaces of the pallet;

A more specific object of the invention is to provide a rate bar having a plurality of spaced anti-Warping ribs extending downwardly from its underside throughout substantially the entire longitudinal extent of the bar.

A still further object of the invention is to provide a finger type grate bar having anti-warping ribs thereon and adapted for use with a pallet construction, for a sintering machine, comprising a plurality of spaced transversely extending supporting portions.

Other objects and advantages of the invention will be apparent from the following description taken in conjunction with the drawings, in which:

Fig. 1 is a diagrammatic view of a sintering machine, showing the path of travel of the pallets therein.

Fig. 2 is an enlarged plan view of one of the pallets shown in Fig. 1, with a plurality of grate bars embodying the invention mounted thereon.

Fig. 3 is a vertical sectional view, taken generally on line 3-43 of Fig. 2, one of the transverse supporting walls of the pallet being removed to better illustrate the structure of the grate bar.

Fig. 4 is a vertical sectional view taken on line 44 of Fig. 2.

Fig. 5 is an enlarged end elevational view taken from the right of the grate bar shown in Fig. 4.

Fig. 6 is an enlarged vertical sectional View taken along line 6-6 of Fig. 4.

Fig. 7 is an enlarged horizontal sectional view taken along line 7--'7 of Fig. 4.

Fig. 8 is reduced scale vertical sectional view similar to Fig. 4 but showing a modification of the invention.

Fig. 9 is a reduced scale side elevational view of an existing grate bar showing the warpage that has been found to occur in service.

Referring to the drawings, there is shown the invention applied to a sintering machine of the usual type, but it will be understood that it may be applied to any machine in which sintering or like operations are carried on. The sintering machine comprises a series of pallets 10 mounted on an endless conveyor, as shown in Fig. l. The pallets 10 receive and discharge the material to be sintered. At the discharge end A of the machine, the pallets drop to an upside-down position and travel thus until the loading end B is reached, at which time they are raised to upright position.

Pallet it: comprises a generally rectangular frame 11 which extends transversely of the sintering machine. Frame 11, as shown in Figs 2 to 4, inclusive, comprises longitudinally extending spaced members or side walls 12 and 14 connected by transversely extending forward and rearward members or walls id16 and intermediate members or walls lid-18. Extending upwardly from walls 12 and i4 and integral therewith are portions 17 for confining the material being sintered. Each of walls 12 and 14 is provided with depending brackets 20 which may be reinforced upon the pallet frame by means of webs 22. Brackets 20 are adapted to receive means for moving the pallet upon the track of the sintering machine.

Mounted on pallet frame 11 for supporting the material to be 'sintered are a plurality of finger type gratebars comprising end bars 26 and intermediate bars 28. Each bar comprises an elongate body portion adapted to extend across the supporting members or Walls 16 and 18 of the pallet and rests thereon by engagement of correspondingly spaced under-surfaces of the body portion with the body or walls, as shown in Figs. 4 and 8. The bars are positioned to extend in the directionof travel of the pallet, thus permitting the use of a shorter bar and providing a more flexible grate for the sintering process. In the embodiment shown, spacing projections 30 are provided on both sides of bars 28 so that when the bars are assembled on the pallet, openings 32 are formed which permit the passage of air and hot' gases through the charge during sintering. It will be understood, of course, that projections 39 may be formed on only one side of body portions of the bars instead of both sides, as illustrated.

The underside of each of bars 28 is formed with a pair of downwardly extending retaining lugs 34 and 35 disposed near the central portion thereof. These lugs are spaced'from and underlie transversely extending stops 36' on intermediate walls 18 of the pallet frame and allow the bars to drop away from the pallet a predetermined amount when the latter is in the aforementioned upsidedown position. Stops 36 may be either secured to walls 18 or formed integrally therewith.

It will be observed that retaining lug 34 is spaced closer to'the underside of the opposing stop 36 than is lug 35. With this zurangement of the lugs and stops,

when the pallet drops to upside-down position in the operation of the sintering machine, lug 34 will be the first to engage the opposing stop 36 on wall 18 of the pallet-and arocking action of the bar will tend to occur.

The extent of rocking is limited by the subsequent engagement of lug 35 on the bar with its opposing stop on the pallet. This rocking of the grate surface during the discharge operation acts to effectively loosen the sintered material to permit it to drop away from the grate and. thus-maintain the air passages 32 clear.

In accordance'with the invention, the underside of each of bars 28 is formed with a plurality of spaced, antiwarping means 38 extending downwardly from the elongated body portion of the bar. Means 38 comprises depending ribs or projections 40 disposed near the outer ends of the bar and rib 42 disposed at the central portion of the bar between retaining lugs 34 and 35. Outer ribs 40 in the embodiment shown have a general configurations in vertical cross-section of an inverted isosceles triangle, having its vertex rounded or arcuate in shape, as indicated at 44 (Fig. The side surfaces 46 of ribs 40 merge with and form plane continuations of the tapered side surfaces 48 of the grate bar proper. The ends of the ribs are also of roundedcontour and diverge upwardly to merge with the underside of the grate bar.

Central rib 42 extends between retaining lugs 34 and 35 on the underside of the bar and as best seen in Fig. 7, the sides 50 of the rib converge toward the vertical axis of the grate bar. In a vertical direction, sides 50 diverge upwardly and merge with sides 48 of the grate bar proper.

It has been found that the vertical dimension of strengthening ribs 40 and 42 should be at least as great as, and preferably a little greater, than the vertical dimension of the body portion of the grate bar proper. The reason for this relationship is that the ribs 40 and 42, as described, represent a substantial portion of the metal of the grate bar and as the bars are repeatedly heated and cooled during a continuous sintering process, ribs 40 and 42, being disposed well below the heating or sintering zone of the grate bed, are not subjected in any great degree to this constant variation in temperature. Furthermore, because of the downward convergence of the sides of the ribs, they are less subject to the effect of the hot air and gases passing through openings 32 in the grate bed. In addition, the convergence of the ends of outer ribs 40 likewise aids in eliminating the effect of the down draft and thus helps to maintain the ribs at a lower operating temperature.

It will be seen that the junctures of the ends of ribs 40 with the underside of the bar are disposed as close as practicably possible to the supporting walls 16 and 18 of the pallet to thus position a substantial portion of the metal of the grate bar below the heating zone of the grate bed. It will also be apparent that outer ribs 40 add to the proportionate weight of the outer ends of the bars, thereby tending to maintain the latter in engagement with the top surfaces of support walls 16 of the pallet when the latter is in upright position.

During the sintering process and consequent repeated heating and cooling of the bars, the ribs 40 and 42 will prohibit or substantially limit warping of the bars, as so frequently occurs in conventional finger type grate bars (Fig. 9). Thus, by preventing or limiting warpage, a substantially even grate surface is maintained and the bars tend to wear uniformly throughout their entire length. It will be understood therefore that the invention provides a longer wearing and more economical grate.

It will be apparent to those skilled in the art that the design of ribs 40 and 42 lends itself to the economical production of molds for casting the grate bars especially as concerns the drawing of the patterns during the molding process.

Retaining lugs 34 and 35 and ribs 40 on the bars are spaced from walls 16 and 18 on the pallet, as at 49 (Fig. 4) to provide for horizontal movement of the bars with respect to the pallet, or in a direction longitudinally of the bars. This movement additionally aids in breaking up the sintered material during discharge to maintain the air passages 32 clear. I

In assembling bars 28 on the pallet, each bar is lowered into space C adjacent the side of either wall 12 or 14 with retaining lugs 34, 35 and associated strengthening rib 42 between transverse walls 18 and outer strengthening ribs 40 between transverse walls 16. As the ends of stops 36 do not extend to side walls 12 and 14 of the pallet, there is no interference between lugs 34 and 35 and the stops in this position of the bar. The bar may then be moved transversely to the center of the pallet and the rest of bars 28 assembled in a like manner. The grate assembly is completed by adding one of bars 26 to each end of the pallet, as shown in Figs. 2 and 3, and inserting pins 50 through openings in side walls 12 and 14. It will be observed that a limited amount of vertical movement of end bars 26 with respect to the pallet is permitted by the looseness of the fit of pins 50 in the pallet. Relative movement of end bars 26 in a lengthwise direction is limited by depending projections 52 (Fig. 3) which are adapted to engage walls 1616 on the pallet frame.

An important aspect of the novel grate bar is that it may be used with existing conventional pallets of the type comprising spaced transversely extending support walls, thus facilitating interchangeability of the bar with those used in present sintering machines.

In Fig. 8 there is shown a modification of the invention in which the retaining lugs 54 project inwardly toward the transverse center line of the bar instead of outwardly, as in the previous embodiment. In this connection the pallet frame of the modification comprises a single intermediate wall 56 with transverse stop means formed on both sides of the wall. The modified bar does not have a central strengthening rib as in the previous embodiment and outer anti-warping ribs 58 merge with retaining lugs 54 to form a unitary structure. The remainder of the bar and the pallet construction is similar to the first de scribed embodiment, and operation and assembly is practically identical therewith.

From the foregoing description and accompanying drawings, it will be readily understood that a novel finger type grate bar for a sintering machine or like device is provided comprising means on the underside of the bar which eliminates warping of the bar upwardly, away from the supporting surfaces of the pallet to thus provide a much longer wearing and more economical grate.

The terms and expressions which have been employed are used as terms of description and not of limitation and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. In a grate assembly, a pallet comprising a plurality of spaced supporting members, a grate bar having an elongate body portion adapted to extend across said supporting members and rest thereon by engagement of correspondingly spaced undersurfaces of said body portion with said members, said grate bar having longitudinally extending anti-warping ribs integral with the body portion and separated by said undersurfaces, said ribs projecting downwardly free of the members from the level of the undersurfaces for a distance substantially equal to the depth of the body portion to dispose the ribs below a work-heating zone of the grate assembly whereby they are maintained in a cooler and stronger state than said body portion.

2. The grate assembly of claim 1 wherein opposite side surfaces of the ribs extend away from said body portion in converging directions.

3. The grate assembly of claim 1 wherein opposite side surfaces and opposite end surfaces of the ribs extend away from said body portion in converging directions.

4. The grate assembly of claim 1 comprising downwardly-facing abutment means carried on certain of said members, and lugs positioned on certain of said ribs to extend underneath the abutment means in the normal upright position of said assembly, and the ribs have a depth at least equal to that of the body portion.

5. In a sintering machine having a heating or sintering zone, an endless conveyor extending thereunder comprising an upper track and a lower track, a pallet adapted to be carried by the conveyor along both tracks and comprising spaced parallel supporting members, abutment means carried on certain of said members, a grate bar having an elongate body portion adapted to extend across said supporting members and rest thereon by engagement of correspondingly spaced undersurfaces of said body portion with said members, said grate bar having anti-Warping ribs integral with the body portion and separated by said undersurfaces, in the upright position of said pallet along the upper track, said ribs projecting downwardly free of the members from the level of the undersurfaces for a distance substantially equal to the depth of the body portion to dispose the ribs sufficiently away from the top surface of the bar whereby the ribs are maintained in a cooler and stronger state than said body portion, the grate bar at said position of the pallet having lugs extending underneath the abutment means for support of the bar when the pallet is positioned upsidedown along the lower track.

6. The sintering machine of claim 5 wherein said lugs project from end portions of said ribs.

7. A grate bar for use on a pallet of a conveyor-type sintering machine comprising an elongate portion having spaced undersurfaces adapted to engage spaced portions of a pallet, ribs integral with the body portion and separated by said undersurfaces, said ribs projecting away from the body portion perpendicularly to the plane of the undersurfaces for a distance substantially equal to the depth of the body portion to dispose the ribs sufficiently away from the top surface of the bar whereby the ribs are maintained in a cooler and stronger state than the body portion during sintering operations.

References Cited in the file of this patent UNITED STATES PATENTS 1,633,931 Ellis June 28, 1927 1,912,886 Buckley June 6, 1933 2,322,873 Moriarty June 29, 1943

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