US2162741A - Grate bar - Google Patents

Description

June 20, 193 v w. H. MORIARTY 2,162,741

GRATE BAR Filed June 12, 1936 2 Sheets-Sheet 1 l/Vl' son HMorz'ar Clam E M ATTORN EY June 20, 1939. w. H. MORIARTY 2,152,741

GRATE BAR Filed June 12, 1936 2 Sheets-Sheet 2 A-l. l-

.INVENTOR Wzlson EMrarzariy B ATTORNEY Patented June 20, 1939 UNITED STATES PATENT OFFICE GRATE nan of Ohio Application June 12, 1936, Serial No. 84,815

12 Claims.

This invention relates to grate bars for sintering machines, and more particularly to an improved construction thereof.

In sintering machines of the usual type there is an endless conveyor made up of a series of pallets on which the grates are mounted. This conveyor carries the unsintered ore beneath a furnace where the combustible material mixed with the ore is ignited by the flame from the burners. The pallets then pass to the discharge end where the sintered ore is dumped. After the pallets have been emptied of their hot bed of ore they travel downward and along a lower track back to the feeding end where they are lifted by suitable means to the upper level again to repeat the process.

The ore supporting surface of the pallet comprises a plurality of grate bars formed with openings through which passes a mixture of air and hot gases from the furnace. A down draft is created by a suction fan or similar means and the above mixture in passing through the burning material pulls the flames into contact with the grate bars and, combined with the effect of the hot ore on the grates, raises the temperature of the bar to such a degree as to form a coating or scale of iron oxide on the surfaces thereof.

It has been customary to form the elongated openings in the grate bars of equal width 30 throughout in a manner such that the sides of the holes at the supporting surface of the bar were equally spaced and parallel. The side walls of the openings then taper downwardly and outwardly toward the bottom of the bar to enlarge the openings gradually, so as to prevent the ore from clogging these openings during the sintering, process. It was also customary to vary the thickness of the bar so that it is progressively decreased towards its lateral edges, thereby making the lateral edge portions of much less thickness than the central portion.

Considerable difficulty has been experienced with the above grate bar construction during a s ntering process due to the fact that, the por- 5 tions of the openings lying adjacent the lateral edges of the bar become greatly enlarged while the central grate bar portion showed little enlargement. This is called "burning out" of the bars. The enlargement of the openings was not 50 uniform so that while the central portion was still capable of usefulness this non-uniformity resulted in some bars having to be replaced due to the edge portions wearing away prematurely. In the usual construction of grate bars of the 55 type with which this invention is conoemed there is a reinforcing rib on the under side of the bar along its longitudinal center line, resulting in solid central portion through which the gases cannot pass. Usually, grate bars are constructed so that when they are assembled on a pallet 5 there is clearance between adjacent bars which provides an air passage along the adjacent edges thereof. Thus there were formed, between centers of adjacent grate bars, air passages of unequal areas that increased toward the edges of 10 the bars. As a result, a greater volume of hot gases, which tend to follow the path of least resistance, passed through the grate nearer the edges of the grate bars than to the center line thereof. It has been found that fine particles 15 of ore are carried by the down draft and these particles have an abrasive action that wears away the walls of the openings and causes the aforesaid enlargement thereof. Since the blast of air in following the path of least resistance 20 passes through the bars near their lateral edges, it follows that the greatest wear will occur at these points. Any iron oxide present on the bars will be rapidly flaked oil by the above abrasive action, thus exposing new surfaces for oxidation. 25 Furthermore, if a new bar is placed between two worn bars, there will be a still greater tendency for the gases to pass over the new bar, which has holes not yet enlarged from use, thus causing a greater proportion of the gases to cut across the lateral edges. I have found that this action results in more rapid wear of both the old and new bars. In addition, this concentration of the hot flames and gases makes the grate bars hotter at these lateral points, causing more rapid oxidation.

The principal object of my invention comprises a novel construction for uniformly distributing the air and gases over the grate surface of a sintering machine and includes a grate bar in which the openings are restricted at points where, heretofore, greatest wear has occurred. Another object is to provide a construction by which the rate of wear during the sintering operation is materially reduced. More specifically, a the invention contemplates a grate bar construe! tion in which the openings are of less width at the edges of the bar than at the center portions thereof. Moreover, the walls of the openings are formed in substantially vertical planes for a short 0 distance from the top surface of the grate bar before flaring downwardly and outwardly, so as to provide additional metal to resist abrasion and maintain, as long as possible, the original shape of the openings at the ore supporting surface of the bar. I also form these flaring walls such that the rate at which the openings enlarge, due to similar amounts of wear will be substantially uniform at all points longitudinally of the openings.

Other objects and advantages of my invention will be in part apparent and in part pointed out in the following description of a preferred embodiment thereof, taken in conjunction with the attached drawings, in which:

Figure l is a plan view of a pallet showing a plurality of my improved grate bars in position, with one of the grate bars partly broken away to show the supporting surfaces of the pallet.

Figure 2 is a vertical sectional view taken on line 2-2 of Fig. 1.

Figure 3 is a side elevational view of one of my grate bars.

Figure 4 is an enlarged vertical sectional view taken on line 4-4 of Figure l, and

Figure 5 is an enlarged plan view of a portion of a grate bar.

Referring particularly to Figures 1 and 2 of the drawings, the pallet comprises a pair of longitudinal frame members I Joined by outer transverse members 2 and intermediate members 3. The members I are formed with upper grate bar supporting surfaces 2. The top surfaces 5 and 6 of members 2 and 2, respectively, are positioned slightly below surfaces 4 and these members may be provided intermediate the ends thereof with raised supporting portions 1 and 8, respectively. Grate bars 9 rest at each end on the surfaces 4 of the pallet and may or may not engage the surfaces I and 2, depending on whether or not the bars are cambered slightly in a direction such that the central portion thereof is higher than the ends. The grate bars are spaced apart on the pallet and. since they do not contact surfaces 5 and I5 throughout their longitudinal extent, an air slot is formed between the bars. Openings are provided in the longitudinal members l to receive pins ll entering recesses II in the grate bars to limit movement thereof away from the pallet. Extending upwardly and outwardly from members I are flanges l2 for the purpose of confining ore to the lateral extent of the pallet.

Each grate bar comprises a substantially horizontal ore supporting portion l3 and 9. depending rib M positioned substantially on the longitudinal center line of the bar. Openings l5 and i6 extend through the horizontal portion to permit passage of air and hot gases. It will be noted that the openings l8 extend nearer the lateral edge I! of the bar than do the openings it. Also the under side of the horizontal portion is cut away, as at II in line with the openings I, so as to leave only a small section of metal Is that is readily broken by the expansion and contraction of the grate bar, so as to divide the latter in a plurality of sections to reduce warpage of the bar in service. Each of openings I! have side walls extending a short distance vertically thereof. In like manner the openings II are formed with side walls 2|. These vertical side walls converge from the longitudinal central region of the grate bar toward the lateral edges ll thereof, thereby forming openings progressively decreasing in size toward said edges so that the combined area of the space between adjacent bars and the portions of the openings nearby is substantially the same as the area of the openings in the grate surface nearer the central portions of the bar. As a result the blast of air and hot gases is distributed more evenly over the entire grate surface and the latter is free of detrimental hot spots.

At the lower ends of surfaces 20 and 2|, the side walls of the openings l5 and I6 are tapered as at 22 and 23, respectively, so as to form a larger opening toward the bottom of the bar to prevent clogging of the holes by the material being sintered. In previous constructions these tapered portions of the holes started from the top surface of the grate bar, that is, the vertically extending walls 20 and 2| were omitted. By maintaining the walls vertical for a short distance before beginning the taper, considerably more metal must be worn away before reaching the sloping portions of the walls, at which point the rate of enlargement of the openings greatly increases.

I have also formed the under surfaces 24 of my grate bar so that they slope downwardly and outwardly, thereby increasing the thickness of the horizontal portion progressively toward the lateral edges. In this manner more metal is provided adjacent the space between the bars to withstand wear and for the absorption and dissi pation of heat, thereby additionally prolonging the period of usefulness of the bar. It will further be noted that the tapered surfaces 22 and 23 are at a uniform angle to a vertical plane through surfaces 20 and 2|, so that the rate at which the slots open, due to wear, is practically uniform throughout their length. I have found that an angle of approximately '7 degrees to the vertical gives very satisfactory results.

It will thus be seen that I have provided means for uniformly distributing the air and hot gases over the area of the grate surface by constructing the grate bars in a new and novel manner. Furthermore, the vertical contours of the openings have been constructed and arranged so as to overcome the disadvantages previously experienced, resulting in a substantial increase of the useful life of the grate bar.

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

What I claim is:

1. A grate bar for sintering machine having a plurality of transversely extending openings therein, said openings being narrower towards the lateral edges of said bar than at points nearer the center thereof.

2. A grate bar for sintering machine having a plurality of transversely extending openings therein, the walls of said openings converging from points adjacent the center of said bar towards the lateral edges thereof.

3. A grate bar for sintering machine having a plurality of openings therein, the walls of each opening converging in one direction between the top and bottom edges of said bar and in another direction intermediate the lateral edges thereof.

4. In a device of the class described, a grate for sintering machines having an ore supporting surface and a plurality of slots and openings therethrough, said slots extending in one direction of said grate and said openings extending generally at right angles to said slots, the walls of said openings converging toward said slots so as to substantially equalize the area of the surface openings per unit of area of the grate over the extent of said grate.

5. In a device of the class described, a traveling grate for sintering machines comprising a series of grate bars each having a rib extending downwardly from the under side thereof, said bars being spaced apart to form an air slot therebetween, each grate bar being formed with openings each converging from adjacent said rib towards a point near the air slot between adjacent bars.

6. A grate bar having an upper ore supporting surface and a rib extending from the under side of said bar, the under surface of said bar, in a direction laterally of said rib, extending downwardly and outwardly away from said supporting surface, said bar having a plurality of irregularly shaped openings between said under and supporting surfaces.

7. A grate bar for sintering machine having a plurality of the side walls of each opening converging outwardly the under surface of said bar being tapered downwardly toward the lateral edge of the bar such that as the area of said openings Patent No. 2,1625'fhl.

CERTIFICATE OF CORRECTION.

of openings extending through said bar, the under surface of said bar extending downwardly and outwardly towards the lateral edges of the bar and forming portions of greater thickness nearer said lateral edges than at points adjacent the longitudinal central region of said bar.

10. In a device of the class described, a grate for sintering machines having an ore supporting surface, said grate comprising a plurality of ing surface, the under surface of each bar sloping downwardly and outwardly towards a pair of opposite sides of said bar and away from said supporting surface and forming portions of greater thickness nearer said sides than at points ad- Jacent the center of said bar.

12. A grate bar for sintering machines having an ore supporting surface, the under surface of said bar sloping downwardly and outwardly towards a pair of opposite sides thereof and away from said supporting surface and forming portions of greater thickness nearer said sides than at points adjacent the center of said bar.

WILSON H. MORIARTY.

June 26, 1939- WILSON H. MORIARTY.

. It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 3, first column, line 21, claim 7, before the article "the" insert the words and comma openings theroim; and that the said Letters Patent should be read with this correction therein that the same nay conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of September, A. D. 1959.

(Seal) Henry Van Arsdalo, Acting Commissioner of Patent s surface openings per unit of area of the grate over the extent of said grate.

5. In a device of the class described, a traveling grate for sintering machines comprising a series of grate bars each having a rib extending downwardly from the under side thereof, said bars being spaced apart to form an air slot therebetween, each grate bar being formed with openings each converging from adjacent said rib towards a point near the air slot between adjacent bars.

6. A grate bar having an upper ore supporting surface and a rib extending from the under side of said bar, the under surface of said bar, in a direction laterally of said rib, extending downwardly and outwardly away from said supporting surface, said bar having a plurality of irregularly shaped openings between said under and supporting surfaces.

7. A grate bar for sintering machine having a plurality of the side walls of each opening converging outwardly the under surface of said bar being tapered downwardly toward the lateral edge of the bar such that as the area of said openings Patent No. 2,1625'fhl.

CERTIFICATE OF CORRECTION.

of openings extending through said bar, the under surface of said bar extending downwardly and outwardly towards the lateral edges of the bar and forming portions of greater thickness nearer said lateral edges than at points adjacent the longitudinal central region of said bar.

10. In a device of the class described, a grate for sintering machines having an ore supporting surface, said grate comprising a plurality of ing surface, the under surface of each bar sloping downwardly and outwardly towards a pair of opposite sides of said bar and away from said supporting surface and forming portions of greater thickness nearer said sides than at points ad- Jacent the center of said bar.

12. A grate bar for sintering machines having an ore supporting surface, the under surface of said bar sloping downwardly and outwardly towards a pair of opposite sides thereof and away from said supporting surface and forming portions of greater thickness nearer said sides than at points adjacent the center of said bar.

WILSON H. MORIARTY.

June 26, 1939- WILSON H. MORIARTY.

. It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 3, first column, line 21, claim 7, before the article "the" insert the words and comma openings theroim; and that the said Letters Patent should be read with this correction therein that the same nay conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of September, A. D. 1959.

(Seal) Henry Van Arsdalo, Acting Commissioner of Patent s

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