US2152076A - High temperature shaft or roll - Google Patents

Description

Mai-ch 28, 1939. P. s. MENOUGH HIGH TEMPERATURE S HAFT 0R ROLL Filed July 15, 1936 Patented Mar. 28, 1939 PATENT orFicE "HIGH TEMPERATURE SHAFT R ROLL I a Paul S. Menough, Pittsburgh, Pa., assignor to Michiana Products Corporation, Michigan City, Ind., a corporation of Indiana Application July 15, 1936, Serial No. 90,754 I 6 Claims.

, Thisinvention relates-to shafts or rolls for use under high temperature conditions and more particularly for use in high temperature furnaces. I One of the objectsof the invention is the provision of a new and improved high temperature shaft or roll that is formed from sections provided with novel means for connecting the sections together.

Another object of the invention is the provision of a new and improved furnace shaft having a cast central portion and having end portions welded thereto by a weld that is so arranged that only portions of the weld extend in the direction of rotation of the shaft or roll whereby the parts willbe more nearly permanently connected together.

A still further object of the invention is the provision of a new and improved furnace shaft having a centrifugally cast central portion, provided with reduced end portions attached theretg by welds arranged at an angle to the direction; of travel of the shaft whereby the welds will more firmly hold the parts together and reinforce the carrying capacity of the shaft. A further'object of the invention is the provision of a new and improved sectional furnace shaft having novel means for connecting the sections together, that is inexpensive to manufacture, strong, rugged, emcient in use, and. that is not likely to become bent, distorted, broken, or the parts become disconnected. while in operation.

Other and further objects and advantages of the invention, will appear from the following description taken in connection with the accompanying drawing, in which Fig. 1 is a vertical section of a furnace, shown in dotted lines, showing the invention in position therein, with parts in' section and parts broken Fig. 2 is a section on the line 2 -2 of Fig. 1

Fig. 3 is a front elevation of a modified form of the shaft, with parts in section and parts broken away;

Fig. 4 is an elevation of one end of the central section of the shaft of Fig.3 before the assembled;

Fig. 5 is an, end elevation thereof Fig. 6 is an elevation of an end portion of a modified form of shaft, with parts broken away 50 and parts in section; 1 v

Fig. 'lis a vertical section of the end section of the shaft shown in Fig. 6, with parts broken away;

- Fig. 8 is an elevation of the central portion of tlieshaft'shownin Fig. 6, with parts broken away;

55 and shaft is (cl. ass-cl Fig. 9 is an elevation of a carbonizing retort, with parts in section and parts-broken-away.

It is common practice to employ a plurality of rotating shafts which form conveyors for transferring material through the furnace while the 5 same is being heat treated.

More or lessdifficulty has been experienced in .the use of these shafts due to the intense heat to which they aresubjected in certain types of fur-. naces. The qualifications for; the shafts are 10 rather exacting. They must have sufflcient strength under high temperatures so that they will not bend, break or become distorted while in use. They must besymmetrical, strong and durable, and free from defects in their construction. 15

The present invention has for its principal object, the provision of shafts of superior quality.

' This is accomplished by centrifugally casting the central portion of the same from heat resisting alloys, and by securing the end portions to the 20 central portion in a novel manner.

These shafts have been made by casting metal in conventional stationary molds. Numerous weaknesses have developed in'castings so made. It is very difllcult to hold a heavy core in the center of the mold while molten steel is being poured around it. If the core does not remain in the center of the mold,tlie walls of the casting willnot be uniform in thickness. This means that the metal in the walls will freeze or solidify at 80 different rates,- As molten metal solidifies, it

; shrinks. Consequently, the lighter sections of the wall, as they freeze first, will draw molten metal from the heavier sections to compensate for this liquid shrinkage. This will cause shrinkage voids.

or at least'porosity to be formed in the heavier wall sections whichfreeze last. Also, the low melting segregates will migrate to the portion of the casting which is the last to freeze and there will be present in these heavy. sections not only 40 shrinkage cavities, but also, in the same locality, a concentration of segregates. Moreover these shrinkage voids and their accompanying segreations will be buried in the middle of the wall and cannot be detected by any surface inspection.

side. This will cause the casting to warp.

exaggerated in chromenickel steel castings are automatically corrected by making such castings centrifugally. The wall thickness is determined by centrifugal force and is uniform in all portions of a centrifugal casting. This means there will be no heavy sections, the casting will freeze uniformly and there=will be no shrinkage, no concentration of segregation s, and no warpage.

The present invention seeks to remedy these difficulties by the provision of shafts made in sections, the central or principal section being centrifugally cast, and the end section or sections being rigidly connected thereto by welding or the like. This central section, being centrifugally cast. will be symmetrical about its longitudinal axis; the best of the material will be on the 'sur- 1 face thereby adding materially to the strength and heat resisting property of the shaft; there will be no blow holes or defective parts in the surface of the rolls; the dross and lighter material will be on the inner surface; and the entire material. will be equally distributed about the axis of the shaft.

I have found that shafts made from heat resisting alloy, such as iron-chromium-nickel, give the best results when centrifugally cast, but due to the fact that the openings in the furnace walls through which the ends of the shafts extend, must be limited in area in order to prevent the escape of the furnace heat therethrough, it is common practice to reduce the ends of the shafts to extend through these openings- Since these shafts are tapered at the ends and the walls of the central portion are of such thickness that the axial opening is not of uniform diameter throughout the length of the'shaft, the

- means including welding. In order that thesethe separately east end portion are joined onlyv shaft, when centrifugally cast, must be made in sections. They are preferably made in three sections, the central portion only is centrifugally cast and the end sections are connected thereto by welds may resist both the torque of the operating mechanism and also support the load of the material that is being treated, the weld or welds are so arranged that they extend not only circumferentially around the shaft but also at an angle or angles to the direction of rotation.

This is considered an important feature of the invention. If the centrifugally cast barrel and by a circumferential weld, the bending movement of the shaft has a tendency to become a maximum on the weld. The reason for this is that when a single circumferential weld is employed one section is telescoped within the other and since any looseness whatever in the; joint will tend to permit the shaft to bend slightly at'l-C the joint, such bending will, of course, tend to disrupt the weld. It will be noted that such a butt weld, when it is at the top of the shaft will be in compression. A half revolution later when it '2 2,1t2,o7e'

rates, the thin side will shrink ahead of the thick imposed load. If the end sections are telescoped within the ends' of the central body section, it

would appear at first glance, that the same result as outlined above would be achieved, namely: a leverage which would act against the bending {load of the shaft. This, howeveizis not true. All the heat which reacts on the male'portion of this joint must come through the central shaft which encloses it. The heat conductivity of chromium nickel steel is very poor. Consequently, the end of the central or body section will get hotter than the inserted end of the end the bending load to be concentrated in a weaving stress on the weld itself;

This means that by extending these welds not only circumferentially, but also longitudinally, it

has been found that this weaving stress is effectually resisted.

Referring now to the drawing, the reference character 8 designates a furnace having the walls ii and i2 shown in dotted lines. These walls are provided with openings l3 and I4 through which the reduced ends l5 and I6 of a furnace shaft I! extend, as is usual in such constructions. A sprocket or the like 20 -on thereduced portions of the shaft is provided for operating the shaft in the usual manner.

It is common practice in heat treating furnaces to provide a plurality of parallel shafts or rolls extending transversely across the furnace and rotating the same by suitable mechanism to form a conveyor for transferring material that-is being treated through the furnace. Since the details of the furnace constitute no part of the present invention, it is not thought necessary to further illustrate .or describe the same.

. section and will. expand away from it, allowing Each of the shafts l1 comprises a central secchromium together shall be not less than and not more than 60%. This alloy is preferably centrifugally cast to-form the blank for the central section i8 of the shaft. The central sect on blank is cylindrical and may, if desired, be cast with ribs 22 thereon for splining material transporting disks to the shaft as is usual n such constructions. These ribs will materially reinforce the shaft.

By centrifugally casting the alloy, the heavier and consequently the tougherand stronger portions of'the alloy will be at the outer surface of the shaft or roll thereby adding materially to the strength of the shaft or roll in resisting bending or distortion thereof. By casting the ribs -22 on the surface of the shaft or roll the thickness of the metal of the shaft maybe reduced since the ribs will contain thebest and strongest portions of the metal, thereby adding materially to the resistance to bending ofthe shaft or roll. .7 i

The end sections 89 and 2| of the shaft or roll have reduced portions 15 and I6, each of which terminates at its inner end in a flared portion 23 which merges into a cylindrical portion 261 which is of such diameter that it may beinserted in one end of the central section I8. The

end sections after they have been inserted in the ends of the tubular central section, I, are secured in position by welding. The parts are so arranged that at least some of the welds extend in a direction at an angle to the direction of rotation of the shafts. This may be accomplished in any suitable manner.

In the form of the construction selected to illustrate one embodiment of the invention, which is by way of example only, the ends of the central section l8 are provided with slots 25 extending longitudinally of the section. These slots are of' any appropriate length, but, of course. do not extend inwardly beyond the inner ends of the cylindrical portion 24 of the end section. Any suitable number of these slots may be provided, two being shown for each end.

latter as thecentral section expands thereby' more or less relieving the welds from the stresses caused by this differential radial expansion.

After the parts are assembled, welds 27 and 28 are applied around the edges of thecentral section 3 and around the edges of the slots 25, respectively.

It will thus be seen that the welds 27 and 28 willnot only resist the torque of the operating mechanism, but the welds 28, which extend longitudinally of the central portion will resist any bending or radial movement of the end sections relative to the central section. These welds, in other words, will hold the end and central sections from relative rotation and will also retain them in co-axial relation.

The form of the construction shown in Fig. 3 differs from that just described in that the end sections 29 of the shaft 3| are of a slightly different construction from the corresponding ends l9 and 2| described above and the end portions of the middle section 52 are formed differently and are attached in a different manner. In this form of construction,.the central section 32 is preferably, though not necessarily,

centrifugally cast and its ends are of such a contour that the welds, for the mostpart, will extend at an angle to the direction in which the shaft is rotated.

In the form of the construction shown, the ends of the central portion 32 are scalloped, that is, triangular sections are, removed to form V- shaped'rece'sses 33 and tapered portions 50 ex-' tending about the ends of the section so that the edges at the end of the section will form a more or less zig-zag line around the section.

Each of the end sections 29 is provided with In fabricating the device, the end sections are inserted in the ends of the central section 32, and the tapered portions 30 bent down onto the flared portions 35. Their length is'such' as to leave a recess 39 between their ends and the enlarged portion 38. The recess 39'and the space .between the tapered portions ill may then be lined with welding material as shown at the left in Fig. 3.

In the modified form of the construction shown 'in Figs. 6, '7 and 8, the ends and central portions are so constructed that there is an interlocking connection between the same. By means of this arrangement, the welds are relieved of the torque action of the rotating mechanism. Such an arrangement is desirable for use in furnaces which require a high starting torque on the shafts.

In this form of construction, each end of the central section 4| may be provided with a plurality of projections or tongues 42 which may be spaced from each other a suitable distance as may be desired. These projections or tongues may be of any suitable shape. In the form shown, they are tapered outwardly and are adapted to engage. in corresponding tapered recesses #33 formed in the flared portions M of the end sections d of the furnace shaft 55. The end sections 435 may be, and preferably are, provided with integral'cylindrical portions 239 for telescoping the ends of the central or body portion ii and with radial flanges dB for limiting the lateral movement of the material as it passes through the furnace. The horizontal web 49 is provided with a plurality of openings 5i for receiving the weld as will presently appear.

When the parts are assembled, the projections or tongues on the flared portion M1 and on the central section M engage in the corresponding recesses, the projections or tongues 42 being bent inwardly to engage in the recesses 43. The parts are so constructed and arranged that the projections or tongues 42 are flush with the flared walls 4.4 and the meeting line of the parts constitutes a more or less zig-zag line around the end of the shaft.

It will be noted that in this form of the construction, the parts of the shaft that abut are telescoped as in the previous constructions but the end sections are on the outside. The parts are held in position by welds 52 and 53 which extend along the abutting line of the two sections and in the recesses 5!, respectively.

In Fig.,9 is shown a.further modified form of construction. This form of construction is shown as applied to a retort which is adapted to be used for carbonizing and the like. Inthis form ofthe construction, the retort is in two sections, a body 54 and an end section 55. The end section 55 has one end 56 of substantially the same diameter as the body portion 54 and is provided with outwardly extending tongues 51 which may have tapered sides, as shown at 58, for engaging in correspondingly shaped recesses, or complementary recesses 59 formed in the line formed by the tongue and the recesses.

It will thus be seen that in all forms of construction there are certain or the welds that extend in a direction at an angle to the direction of'rotation of the shaft, that is, there are welded portions spaced longitudinally of the shaft or roll. 'Just what form or shape the weld-may have is immaterial so long as certain portions of it or certain welds extend at an angle to the direction of rotation or are spaced longitudinally of the shaft or roll, is all that is necessary.

The open end of the retort is adapted to extendthrougha corresponding opening in the furnace wall as is usual in such constructions. This end of the retort is provided with thickened portion forming a flange or ring to which the cover may be attached.

While I have disclosed the invention in the form'of shafts or rolls for use in heat treating furnaces, it is understood that rolls foruse in rolling mills for rolling -metal bars, sheets,

commercial iron, or rolls for use in manufacturing plate glass and the like, may be made by centrifugally casting the same, or at least the central sections thereof, and have the end sections comprising the journals attached by setrated welds or welds having portions arranged longitudinally of the shaft or roll, as indicated changes in size, shape, proportion and details of construction may be made without departing from the spirit'and scope of the appended claims.

I claim as my invention: 1. A conveyor shaft for heat treating fur naces comprising a central section centrifugally cast of high heat resisting material and end sections provided with reduced ends forming journals for said shaft; the end sections lapping the central sections and at least a part 7 of the lapping portion being telescopic, one of the lapped portions at each end of the shaft having open end recesses therein extending longitudinally of the shaft, and a weld extending along said recesses for connecting said sections together, said weld having portions thereof extending longitudinally of the shaft and other portions extending around said shaft in a circumferential direction.

2. A sectional tubular shaft for use in heat treating plants comprising a central section of heat resisting alloy, end sections each having portions telescoping the adjacent end of the central section and having a reduced portion constituting a journal for said shaft, and welds connecting said central and end portions together, said welds having portions extending longitudinally and other portions extending circumferentially of the shaft rigidly securing eachv end section to the central section.

3. A rotatable roll comprising a sectional tubular conveyor shaft of high heat resisting al loy having reduced end portions forming journals for said shaft, the central portion of said shaft being centrifugally cast from a heat resisting alloy, said sections having telescoping portions having interlocking projections on their adjacent ends connected together by welds, certain of which extend circumferentially of the shaft and others in a-direction longitudinally 10 of the shaft, the interlocking portions of said sections being flush on their outer surfaces.

4. A sectional tubular shaft for use inheat' treating. furnaces comprising a central section cast from a heat resisting alloy, end sections 15 each having a tapered portion merging into a including end sections anda central section of 30,

high heat resisting material, each end section having its outer end reduced and coaxial with the central section to. form Journals for said roll and its inner end, portion flared, the ends of said central section being complementally tapered and slotted to provide tongues, said tongues lapping the flared portion of the adjacent end section, and welds extending along the marginal edges of said tongues and securing said sections together.

6. A conveyor shaft for heat treating furnaces comprising a central section of high heat resisting material and end sections provided with reduced ends forming journals for said shaft, the end sections lapping the central section at each end of the central section-and at least a part of the lapping portions being telescopic, the portions of said shaft sections that are telescoped being welded together at intervals about their circumference at the inner and outer marginal portion of a zone the width of which is substantially the same as the length of the lapping. portions.

PAUL S. MENOUGH.

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