US2997287A - Furnace pallets - Google Patents

Description

Aug. 22, 1961 F. J. BORON 2,997,287

FURNACE PALLETS Filed Feb. 24, 1960 3 Sheets-Sheet 1 III N FRANK J. BoRoN Fi l-:55.

Aug. 22, 1961 F. J. BORON FURNACE PALLETS 3 Sheets-Sheet 2 Filed Feb. 24, 1960 Aug. 22, 1961 F. J. BORON 2,997,287

FURNACE PALLETS Filed Feb. 24, 1960 s Sheets-Sheet a A Q 0 :9 q Q JNVENTOR. s BERANK J. BORON tates 2397,28? Patented Aug. 22, 1961 2,997,287 FURNACE PALLETS Frank J. Boron, Elyria, Ohio, assignor to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Filed Feb. 24, 1960, Ser. No. 10,593 2 Claims. (Cl. 26621) This invention relates to the construction of a furnace pallet of the kind which is used to convey material-inprocess through a furnace where the material is fired.

The fundamental function of a furnace pallet is to convey raw material through a furnace incidental to firing the material to place the same in a more advanced stage of process. It is common practice to mix the raw material with coal and place this material on the hearth portion of the pallet. Usually the pallet is equipped with rollers or other carrying means for moving the pallet through the furnace. Ordinarily the pallet travels beneath a firing hood where open flames are directed upon the top of the bed of material, starting the material to burn, and the pallet is moved over a series of wind boxes which sustain burning until a sinter bed is formed.

The pallet includes a base on which the hearth is mounted, and the base also has side members equipped with side plates which are disposed in vertical planes to confine the material. In most instances the front and rear edges closely abut the edges of the side plates of other pallets moving through the furnace, which is to say that a series of pallets are moved through the furnace substantially in end-to-end relationships. Previously the side plates have been made of heavily ribbed cast iron, but in recent years as higher and higher temperatures are used it has been found that the side plates become overheated. Thus, as the pallet travels beneath the firing hood of the furnace, the upper or free edge of the side plate becomes very hot and tends to expand while the lower edge, which is secured to the movable pallet base, is much cooler and resists expansion. This temperature differential when sufliciently large, is believed to cause forging in the upper edge of the side plate. Thus, compressive forces are developed in the top edge portion of the side plate and tension forces are developed in the other portions of the side plate, and these forces may reach such a magnitude as to exceed the elastic limit of the materials of which the side plates are composed. In such instances the upper edge of the side plate may be non-elastically deformed or, in effect, preshortened. Subsequently, whenever the plate is cooled, as during the travel of the pallet on the return side of the sintering machine, the stresses are reversed, causing the cycling action known as thermal fatigue. Cracking and distortion of the side plate result.

A problem related to that described immediately above is excessive growth. The high temperatures encountered in such ore-processing furnaces cause the stress levels in the upper portions of the side plates to exceed the yield point stress for the material of which the side plates are composed. Consequently the heated portions of the side plate experience a very high rate of growth and expand to such an extent that warpage due to hindered expansion is the usual result. Thus, the overall problem is differential temperature, leading to cracking due to thermal fatigue, accompanied by a high rate of growth.

Some of those working on this problem have proposed that the problem be solved by resorting to expensive grades of alloys such as heat-resistant alloy steels, but it is found nevertheless that the tops of the side plates still burn and crack rather severely. In an endeavor to solve this situation which still arose when having resort to heat-resistant alloy side plates, it has been proposed to machine off the severely burned top edges, and associate a replacement part therewith, but this approach to the problem requires taking the related pallet out of the line of production and does not remedy the cracking and distortion of the plate.

Accordingly, it was suggested that the problem be approached by placing a separte bafile plate at the top edge of the side plate so that flash or top radiant heat would not bring up the top surface at a more accelerated rate and cause cracking. However, such baffles have not been effective to prevent such differential heating and in some cases fell off the side plates.

In accordance with one form of the present invention, it has been found that the problem of cracking and distortion in furnace pallet side plates can be minimized by casting these plates so as to have a uniformly sinusoidal vertical section manifest in spaced arcuate n'bs which extend parallel to the upper and lower edges of the side plates. The ribs will be spaced by concave grooves and inasmuch as the side plates are of uniform cross-section, at least in the main central areas, a rib on the outside of the side plate will be directly opposite a groove on the inside of a side plate and vice versa. Additionally the upper edge of the side plate is formed with vertically extending slots afiording air gaps which permit at least a limited degree of thermally induced growth to occur to thereby minimize the development of stresses and warpage due to hindered expansion. This specific con struction represents the primary object of the present invention. Another object of the present invention is to associate the side plate with an auxiliary supporting member, the latter being the part which is secured to the side member of the pallet base. Accordingly, if and when the main side plate becomes unduly distorted or cracked after a prolonged period of use, this can be removed and an entirely new side plate substituted therefor. It will be recognized that a supply of the main side plates can be maintained and substitutes made as required.

The side plates of one form of the present invention can be visualized as a uniformly top-to-bottom corrugated construction accounting for a great deal of strength in the plane required, and ribs of non-uniform section as heretofore proposed to strengthen the side plates are eliminated enabling the present side plates to expand and contract Without any restricting ribs. Moreover, the ribs on the inside face of the side plate in the construction of the present invention effectively baffies the air and serves to introduce the air into the sinter bed.

In certain sintering operations, such as in the sintering of taconite, wherein quite high temperatures and resultantly large differential temperatures between the top and bottom edges of the side plates are developed, it may be desirable to utilize a side plate construction which permits greater thermal expansion and which affords greater resistance to the development of stresses between the top and bottom portions of the side plate than the side plate construction as outlined hereinabove.

In accordance with another aspect of this invention a side plate is constructed so as to utilize a series of unitary slabs or sections, each of which is separate from one another along the entire height of each section. By reason of such sectional construction no distortion or crack-inducing stresses are transmitted between the individaul sections regardless of the temperatures encountered. The individual sections are of relatively narrow Width in cross section so as to be of a flexible nature, are generally rectangular in overall configuration, and are formed with a corrugated inner surface which serves to break up and deflect an air blast into the material to be sintered as hereinabove described. Additionally, a bar or rod is loosely retained in position alongside the outer surfaces of the individual slabs or sections for the purpose of preventing excess distortion of the side plate sections by affording a shear at each vertically extending edge of the sections. Preferably, the sections are formed so as to be attachable directly to the base of the pallet rather than to an auxiliary supporting member. It is yet another object of this invention to construct a sectional side plate as above described.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred embodiments of the present invention and the principles thereof and which is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

In the drawings:

FIG. 1 is a fragmentary end elevation view, partly in section, illustrating aspects of a furnace pallet constructed with side plates in accordance with one form of the present invention;

FIG. 2 is a top plan view, partly broken away, of a pallet which can be utilized with the side plates of the present invention;

FIG. 3 is an end elevation view of a side plate of the present invention;

FIG. 4 is a side elevation view taken on the lines 4-4 of FIG. 3',

FIG. 5 is a bottom plan view of the side plate illustrated in FIG. 4;

FIG. 6 is an end view of the auxiliary or supporting plate shown in FIG. 7;

FIG. 7 is a side elevation View of the auxiliary supporting plate that may be used in association with the side plates;

FIG. 8 is a bottom view of the auxiliary or supporting plate shown in FIG. 7;

FIG. 9 is a side elevational view of another embodi ment of a furnace pallet side plate constructed in accordance with this invention;

FIG. 10 is an end elevational view of the side plate illustrated in FIG. 9; and

FIG. 11 is a fragmentary detail view illustrating the manner in which a rod is retained alongside the sectional side plate illustrated in FIG. 9.

One form of the present invention is illustrated in FIG. 1 as embodied in an otherwise known pallet frame and support construction, which assembly is illustrated generally by the reference numeral 10. With reference to both FIG. 1 and FIG. 2 it is seen that the pallet assembly 10 includes a pallet base 11. The pallet base 11 may be cast as a unitary member and includes side frame members 12 and 13 interconnected by support ribs 15. As illustrated in FIG. 1, the side frame member 13 includes an upwardly projecting flange 36 formed with a stepped construction for facilitating the mounting of a pallet side plate thereon. The side frame member 12 is likewise formed with an upwardly projecting flange like the flange 36 illustrated in FIG. 1. The ribs 15 afford a support for a plurality of grate bars 16.

In accordance with conventional practice wheel assemblies are attached to the opposite ends of the pallet base 11 so that a series of pallets may be transported through a processing furnace on a horizontal track or guide of one sort or another. Thus, as illustrated in FIG. 1 a pallet end member 17 is attached to the side frame member 13 as by a bolt 18. A wheel assembly 19 is journalled for rotation within a depending portion of the pallet end member 17. Also in accordance with conventional practice, a seal bar may be connected to the pallet base 11 as by a pin 21.

The side members 12 and 13 of the pallet base have side plates removably secured thereto, and these side plates extend upward so as to confine the material-inprocess to the hearth portion of the pallet. The free edges of the side plates are disposed well above the plane of the hearth, and this plane is illustrated in legend by FIG. 1. While the side plate constructed in accordance with the present invention can be represented by a one-piece casting directly mounted on the related side members 12 and 13, I prefer for the utmost assurance to resort to a two-piece construction comprising a main side plate and an auxiliary or supporting member which is a member interposed between the lower edge of the side plate and side member of the pallet base. Thus, referring to FIG. 1, side plates as 30 of identical construction in each instance are mounted on the pallet so as to be disposed in generally vertical planes. These side plates have substantially the same length as the side members 12 and 13, and this length is the length E designated in FIG. 2.

Each main side plate 30 is a one-piece member along the length of the pallet and is preferably cast of a heatresistant alloy, and is so cast as to be uniformly sinusoidal in section at least in the main central area between the upper and lower edges 30U and 30L, FIGS. 1 and 3. In other words, the main side place 39 of the pres ent invention can be visualized as having a corrugated appearance both in section and in end view, and this construction is manifested in a plurality of arcuate convex ribs 30R that are spaced by a corresponding member of concave grooves 306 if viewed as a left or right hand side face. As will be apparent from FIG. 1, a rib 30R on the outside face of the side plate is directly opposite a groove 30G on the inside side of the plate.

The upper edge 30U of each side plate 30 terminates in a half rib effect at the inside face or a half groove appearance at the outside face, and in contrast to this the lower marginal inside face portion of each side plate 30 is straightened so as to afford a generally rectangular attaching flange 30F. Each such attaching flange 30F is afforded in order that the side plate can be removably secured to a side plate supporting member in an advantageous relationship now to be described.

Thus, an auxiliary or supporting plate 35 is associated with each side plate 30 and these supporting plates have the same length as the side plates 30. As will be observed in FIG. 1, the side members 12 and 13 of the pallet base are formed with mounting flanges 36, and these flanges have Z-shaped shoulders as 368 which provide flat horizontal upper and lower surfaces 36U and 36L respectively, FIG. 1.

The lower marginal portions of each auxiliary plate 35 have an outer face which is configured complemental to the Z-shaped shoulders 368 so as to have, as shown in FIG. 6, a flat lower face 40, a flat upper face 41 and an interconnecting beveled or sloped face 43. Such complemental construction enables the supporting plates to be set in abutting relation on the parts 36 of the side members 12 and 13 as shown in FIG. 1, and the dimensions are such that the outer face 35F of each supporting member lies in the plane of the outer face 12F or 13F, FIG. 1, of the pallet side member 12 or 13, as the case may be.

The auxiliary supporting plates 35 are held in position on the support members 12 and 13 by fastening pins 45 which project through suitable openings in the pallet ends and support members, FIG. 1.

Each support plate 35 is preferably formed with at least one arcuate rib and groove 35R and 35G, FIG. 1, in the portion immediately above the flat outer face 358. This rib is in the nature of that explained above in connection with the side plates 30, that is, the rib 35R on one face is directly opposite a groove 35G on the opposite face, and the thickness of the rib 35R is uniform for the full extent thereof.

Each support plate 35 is provided with an upwardly directly elongated flange 50 in the position immediately above the rib 35R and its associated groove 35G. Each such flange is horizontally offset as particularly illustrated in FIGS. 1 and 6 and such offsetting affords a horizontal shoulder 51 and an annularly right facing surface 52, FIG. 6. The elongated shoulder or channel thus afforded is so dimensioned in relation to the flange 35F of the related side plate 30 that a side plate 30 can be set on the auxiliary plate 35 with its lower edge 30L, FIG. 1, spaced slightly above the opposing shoulder 51 of the plate 35 when the two are secured together. The width of the shoulder 51 in each support plate 35 is the same as the width of the lower edge 30L of the related side plate and consequently when the parts are joined together as shown in FIG. 1, the inside face 55 of the side plate attaching flange 30F is co-planar with the inside face portion 56 of the related support member 35.

It will of course be recognized that the specific mode of association of the side plate and its supporting member 35, and the manner of attaching the support member 35 and the corresponding support for the pallet base construction, is accomplished with a minimum of projecting parts while still maintaining the assembled plates in a common vertical plane well evident in FIG. 1.

The side plates are rigidly united totheir supporting plates by turning down the nuts 60N on the bolts 60. The flanges 50 of the supporting plates 35 are provided with openings 67 for receiving the bolts 60, and it will be noted in FIG. 1 that the heads of the bolts are disposed at the inside faces of the attaching flange 30F of the side plate 30. Referring to FIG. 4 it will be noted that the openings 65 in the attaching flange of the side plate which receive the fastening bolts 60 are of oval or elongated form and the exposed outer forms of these openings are countersunk to receive the fillet head. Referring to FIG. 7, the openings 67 in the support plate are also of elongated oval form and such configurations of the openings 65 and 67 enable the plates 30 and 35 to expand differentially in longitudinal direction and may be necessitated by thermostresses as encountered in the use of the pallet.

As illustrated in FIGS. 1 and 4, the main side plate 30 is formed with a series of vertically extending slots 70 in the upper edge thereof. Preferably, these slots extend from the upper edge downwardly through the cross section of the side plate for about half of the height of the side plate. Thus, while each slot 70 intersects several of the upper ribs, the lower portion of the side plate includes inner and outer ribs which are continuous and uninterrupted by any slot as 70 along the entire length of the side plate. In this manner, the upper edge portion of the main side plate 30 may expand and contract freely in a longitudinal direction to thereby minimize the development of crack-producing stresses between the upper and lower edge portions of the side plate as a result of a differential temperature therebetWeen. Nevertheless, the resistance to bowing or flexing of the side plate, as obtained from the corrugated construction, is retained by reason of the lower ribs which extend uninterruptedly along the entire length of the side plate. The slots 70 can be formed in the side plate in any suitable manner. Thus, for example, the slots may be cut into the side plate by an abrasive saw, or in accordance with the presently preferred practice, may be cast in the side plate by use of shell molding equipment.

Thus, in accordance with the above-described embodiment of this invention a furnace pallet is so constructed as to incorporate corrugated side plates. This configuration of the side plates has three important aspects. First of all, the corrugated configuration affords parallel longitudinally extending ribs which resist any bending resulting from the charge carried on the pallet and which forces would tend to cause a deformation along a horizontal plane. Secondly, the ribs which are thus formed integral with the side plates obviate any need for additional reinforcing ribs and, because the uniform corrugated configuration imparts to the plates a substantially constant cross section, the desired strength may be obtained with a very light metal section which minimizes any tendency toward cracking or deformation resulting from unequal heating between the upper and lower parts of the side plates. Thirdly, the corrugations provide an irregular surface which tends to break up and deflect a flow of air into the material-in-process. This latter function of the corrugations is important because the normal tendency for the air which is blown into the sintering bed is to follow the path of least resistance down along the pallet side Walls. The corrugations break up such free flow of air and deflect air downwardly on to the sinter bed, and thereby promote better sintering of the material-in-process.

In FIGS. 9-11 there is illustrated another embodiment of a furnace pallet side plate constructed in accordance with this invention. In FIGS. 911 the side plate is indicated generally by the reference numeral 101 and comprises a plurality of generally rectangllanshaped and vertically elongated individual slats or sections 102. Each individual section 102 is substantially identical to every other individual section and includes a countersunk and sligtly horizontally elongated aperture 103 in the lower portion thereof. The lower portions of the individual sections which are formed with the apertures 103 also include a horizontally offset shoulder 104, as best viewed in FIG. 10, so as to be mountable directly on the side members 12 and 13 of the furnace pallet, as illustrated in FIG. 1, to form a flap joint with the upwardly projecting flanges thereof.

The side plate 101 is especially well adapted for use in quite high temperature sintering operations, such as the sintering. of taconite; and in this regard, the individual sections 102 are adapted to be mounted on the side members of the furnace pallet in approximately the same horizontally spaced relation as that illustrated in FIG. 9. By reason of the fact that each individual section is horizontally spaced from an adjacent individual section, no thermally induced stresses can be transmitted through the air gap defined therebetween. Thus, even though quite high temperature differentials should be developed between the upper and the lower portions of the side plate 101 during a sintering operation, the sectional construction of the side plate 101 effectively overcomes problems of cracking and deformation at the upper edge of the side plate encountered with furnace pallet side plates heretofore known. It may be noted that the uppermost portions of the sections 102 are slightly tapered as viewed in FIG. 9 to thereby allow greater expansion at the top edges of the sections. In a commercial embodiment of the side plate 101 illustrated in FIG. 9, wherein the overall height of the side plate is 15 inches, the individual sections are tapered so as to allow 4 inch of expansion at the top edge and of an inch expansion approximately 5-7 inches from the top edge.

In accordance with this invention rod means are mounted on the outer surface of the side plate 101 in a manner such as to enable the rod to aflord a shear force at the adjacent edges of the individual sections 102 to thereby minimize relative lateral distortion between the individual sections. As illustrated in FIGS. 10 and 11, each individual section 102 is formed with a pair of eyelets 105 and 10 6 adjacent the upper edge of the section. A rod or bar 107 is slidably disposed within the eyelets 105 and 106 to project from one vertical side of each section as shown in FIG. 11 to engage the next adjacent section, and in this manner the rod is secured to each section for lateral movement therewith in preventing lateral distortion relatively among the side plate sections at high temperature differentials. Pin means in the form of a pair of pins 108 and 109 are inserted through apertures formed in the rod 107. The pins 108 and 109 are bent over at their projecting ends and are engageable with a pair of adjacent eyelets 105 and 106 to thereby limit sliding movement of the rod 107 within the eyelets and retain the rod 107 therein. In this manner the rod 107 7 maintains the individual sections 102 in lateral alignment with one another so as to prevent relative lateral distortion therebetween and avoid any possibility of pellets slipping through the spacing between adjacent individual sections.

It is another feature of the embodiment of the side plate illustrated in FIGS. 9-11 that the inner surface 111 of each individual section 102 is corrugated, as best viewed in FIG, 10. The corrugations in the inner surface of the side plate serve to break up and deflect the down draft of air into the material to be sintered that is carried on the furnace pallet. Preferably, the space and height of the corrugations are related to the size of the pellets carried on the furnace pallet so that only half of the pallet can lodge in a corrugation. In this manner the pellets cannot become lost inside the corrugations; resultantly, substantially all of the pellets are sintered and very little scrappage is developed.

Additionaly, and as best illustrated in FIG. 10, each individual section 102 is of a relatively narrow width so as to facilitate heat transfer throughout the entire section and thereby minimize the development of thermal stresses due to diiferential temperatures being obtained in different portions of the section.

Hence, while I have illustrated and described the preferred embodiments of my invention, it is to be understood that these are capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. In a furnace pallet of the kind described which is to be subjected to high temperatures incidental to conveying material-in-process supported thereby through a furnace where said material is to be fired, means afiording a base for supporting a hearth and including spaced side members disposable in a horizontal attitude incidental to movement of the pallet through said furnace, a hearth supported by said base and on which said material is to be supported while being fired, and vertically oriented side plates secured to said side members to extend parallel thereto, said side plates extending vertically upward from said side members to have the upper edges thereof disposed well above the upper surface of said hearth to confine said material to said hearth when said base is in a horizontal attitude, each of said side plates comprising a plurality of generally rectangular shaped vertically elongated individual sections mounted on said side members so as to be horizontally spaced from one another, each of said individual sections having a corrugated inner surface for deflecting draft air toward said hearth, and means secured to each section for lateral movement therewith and projecting from one vertical side thereof to engage the next adjacent section horizontally alongside each side plate to prevent relative lateral distortion between adjacent individual side plate sections.

2. A pallet as defined in claim 1 wherein the lastnamed means are rod means, wherein each of said individual side plate sections is formed with an eyelet for sl-idably receiving said rod means therein and wherein pin means are attached to said rod means for abutting said eyelets and limiting sliding movement of said rod means within said eyelets.

References Cited in the file of this patent UNITED STATES PATENTS 114,336 Peckham May 2, 1871 527,382 Boal Oct. 9, 1894 1,373,620 Larson Apr. 5, 1921 2,710,747 Shea June 14, 1955 2,824,730 Boron Feb. 25, 1958

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