US2483592A - Furnace shaft construction - Google Patents

Description

Filed Jim 6, 1948 C. W. NICHOLS ETAL FURNACE SHAFT CONSTRUCTION 2 Sheets-Sheet l I NVENTORS. CHARLES W. NICHOLS.

, osHuA GREENSPAN.

By UMJL,

ATTORNEYS.

Get, 4, 1949., c. w. NICHOLS Ema.

FURNACE SHAFT CONSTRUCTION 2 SI ieets-Sheet 2 Filed Jan. 6, 1948 N; m L m V fi M m m mNR m W M 5% E H i M MJU c w hollow shafts used in such furnaces.

Patented Oct. 4, 1949 UNI TED STATES PATENT OFFICE v a FURNACE snrm'r eossmvcnosii Charles W. Nichols, West"0range,and-Joshua Greenspan, .Nutley, N. Jgas'si'g'nors tozNichols Engineering & Research Gorporation -New York, N. Y., a corporation of Delaware Application January 6, 1948',Serial 1 10.772

8 Claims. 1 This invention relates to roasting furnaces, and more particularly to'the construction of rotatabl Roasting furnaces ofthis character customarily are composed of a plurality of superposed roasting hearthswhich are contained within a cylindricalhousing and which are normally provided with a central rotatable hollow shaft having hollow rabble arms attached' radially thereto. The shaft has an inner passage through which cooling air is circulated to inner passages in the rabble arms, returning through outer passages in the rabble arms to an outer passage Within the shaft. Shafts as used heretoforein'such constructions have been made in sections, each of which has comprised a single casting, including integrally the inner and outer tubular members thereof. These members usually are interconnected by means of a plurality'of integral-webs. This integral construction'has various disadvantages, as

'will be pointed out hereinafter.

-I n accordance with the present invention a construction is provided having a hollow rotatable shaft comprising separate inner and outer tubular members which, if desired, may be formed of dissimilar metals andjwhich accomplish certain additional advantages, to appear more fully hereinafter.

Various other objects, features and advantages of our invention will be' apparent from the detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings arefor purposes of illustration only and are not intended as a definition of the limits of the invention, reference for this latter purpose being had to the appended claims; Inthe drawings: p r V a Fig. 1 is a sectional front elevation of a typical portion of a roasting furnace of a type in which our invention canbe used, the section being taken substantially alongthe vertical axis thereof;

Fig. 2 is a horizontalsectional view of a rotat able furnace shaft embodying our invention, the section being taken substantially on line 22 of Fig. 1;

Y Fig. 3 is an enlarged side elevation,in section with parts broken away, of the shaft shown in Fig.2;

Fig. 4; is a fragmentary'enlarged detailedview in section of two portions of an inner tubular section showing a severance of said portions and a seal therebetween; j 1

Fig. 5 is an enlarged detailed top. view-oi a 2 pair or cooperating fingers and lugs upon the inner andouter shafts prior" to forming's'ame for therecep-tioncfaconnectinglmember;

Fig. 6 is a top view 'of'the fingers'shownin Fig. 5. with a connecting member "shown in section "thereb'etwe'en; and-* f Fig. '7 is a. side elevation, partly'in section and with parts broken- 'away fof the fingers and connecting member shown in Fig; 6.

In the furnace shown in Fig. 1, a plurality of vertically .spac'ed-iand substantially circular hearths'are provided-as'at-JO, H and I2. These hearths are surrounded and-supported in aconventional manneribyza substantially cylindrical furnace Wall 132 A'rotatable'shaft l4 is'mounted vertically at .lthe" center of the hearth's. To the shaft are attacheda pluralityiof'rabble arms Ilia, 151),: 15c? and.- *l5d 3having attached thereto depending te'eth .16 :somouhted as gradually. to .move the chargeradia'lly. of the hearths as the rabble arms'slowly rotate? shaftfll lxnormally consists of a plurality of superposed .;tubular'.. members, :each having, an .outel. tubular f'section" and an'inner tubular section, the latter-conducting: coolingfair tothe rabble1arms" 'as.labove mentioned. 'It is, of course, possible toiemployionly a single tubularmember.

1A chargestofbetroastedlis introduced; into the ,furnace at itstopgpassingsuccessivelydownward under the::influen"ce' of gravity and the Push .of..the;rabble:arriis through acentra'l openingto hearth-1| I, Ithence through-peripheral openings ;l8t,o? hearth I land then out the. central opening .19 to similar lower :hearthsior to a final passage. 1 The structure and.operation thus-far described are: .old .inthe iart,i;being; shown; for. example, in the patent to zDudleyBaird N 0-; 1,669,925; issued .May 15.19281. :;.c.,. g Y

:In the operati n of thistype of;furnace,* ithas been gfound thatmnder high temperature conditions parts of, *thegc entralishaft': sometimes are jfractured.- 1'Ihis-is due usually to unequal expansion of suchvpart's, Theregion of the furna'ceaboutthe outersurface of'the shaft reaches high temperatures-and the. outer tubular. sections expand both longitudinally andeircumferentially. The inner tubular sections'ontheot'h'er hand are cooled morethairsaid outer sections by the air circulating therein and do not reach the same hightemperature; This temperature diiferential results in an expansion 'diflerential wherein the outer tubular: sections lengthen relativet-to' said inner sections; j This-riplaces; the connecting ribs or webs lnder highstressxsometimes to suchan extent a's'to. producea 'fracturefthereof"or a frac- 3 ture of either the inner or outer tubular sections adjacent the juncture of the ribs therewith. Replacement of the shafts in prior construction has entailed considerable inconvenience and loss due to the shutting down of the furnace, and due to the fact that entire tubular members in many cases have to be replaced. Thus the fracture of a rib usually results in an item of substantial cost.

Moreover, the radially extending rabble arms are supported jointly by the inner and outer tubular sections. Thus a fracture of ribs results in a weakening of the support for the rabble arms and may cause them to twist relative to the supporting shaft due to loss of support of said inner members and due to the resistance of the material which is moved by said arms. Thus a twisting of the inner shaft may occur relative to the outer shaft. This twisting may be communicated to the unfractured ribs and damage them also.

Turning now to the novel features of our invention, Figs. 2 and 3 indicate that we have constructed the shaft I4 of separate parts which are associated in a novel manner. Outer tubular sections are shown as at 20, 2| and 22. Correspending inner tubular sections are shown as at v23, 24 and 25.

As above mentioned, each outer tubular section, such as 2I, will lengthen appreciably under the influence of heat by an amount greater than the lengthening of each cooler inner tubular section, such as 24. The sameis true concerning radial or diametric expansion. The latter is also sometimes referred to as circumferential expansion.

This expansion differential, in structures having integral ribs, has affected not only the ribs interconnecting the inner and outer sections but also has affected the alignment of the rabble arms. Referring. to Fig. 1, it will be seen that when an outer tubular section of the central shaft lengthens relative to an inner tubular section, the rabble arms, for example, lid and Ic, will be misaligned as by spreading apart whereby the proper clearances relative to the hearths will be destroyed.

Referring to Fig. 3, novel means are provided for compensating for the longitudinally greater expansion of each outer tubular section as comfrom the inner surface of the outer tubular section 2 I. This group is equal in number to fingers 26. The two co-acting fingers 26, 21, comprising each pair, are held in radial alignment and clamped tightly together, for example, by means of a stud and bolt device 28 as shown in detail in Fig. '7. This device comprises a stud 28a having a head which is adapted jointly to engage surfaces of the fingers 26, 21, and which cooperates with a bolt 28b. A suitable washer 280 can be used with bolt 2% to engage opposite surfaces of fingers 26, 21. The bore through which the shank of the stud 28a extends is formed preferably as shown in Fig. 6. As indicated in Fig. 5, the finger 26 is originally formed with a pointed extremity which extends into a corresponding recess originally formed in the finger 21. However, the adjacent faces of these fingers are in spaced relationship. A joint bore is formed as at 29 in the cooperating fingers.

It is preferable to form the joint bore 29 by a drilling operation. However, this bore can be formed in the casting. The shank of the stud 28a preferably is of slightly less diameter than the diameter of the joint bore 29 in order to permit, if necessary, diametric expansion of the inner tubular section.

The connecting member 28 for associating the cooperating fingers '26, 21, of course, can be in any suitable form, the stud and bolt device being only one structure for this purpose. Each finger connecting member holds each cooperating pair of fingers against relative longitudinal and angular movement but not against relative radial movement caused by expansion.

It has been found desirable to locate the cooperating sets of lugs adjacent the extremities of the inner and outer tubular sections. One of the reasons for this is to provide easy accessibility thereto for purposes of machining castings and for ease of assembly and disassembly. Thus a second group of outwardly extending lugs 30 is formed at the opposite extremity of the inner tubular section 24, which group cooperates with an equal number of inwardly extending lugs 3| upon the outer section.

In view of the fact that the cooperating fingers upon the tubular sections are locked against relative axial or longitudinal movement by virtue of their clamping or connecting members, it is desirable to sever the inner tubular section preferably at the mid-point thereof as at 24a (Figs. 3 and 4). The severance or weakening line 24a preferably is cast in each inner section to facilitate the subdivision thereof into two subsections. The fracture normally is made as by a hammer and chisel prior to assembly of the shaft. However, it is possible to allow the fracture to occur automatically when the shaft and furnace are in operation. Thus when the outer tubular section 2 I becomes greater in length than the inner tubular section 24, the two halves of the latter will separate. Thus after fracture at 24a there will be no resistance by the inner section to the expansion of the outer section. A seal is provided at the point of fracture of said inner section 24 by means of, for example, a metal ring member or collar 32 preferably of a resilient nature which tends to expand to seal the fracture as indicated in Fig. 4, whereby the air flowing through section 24 will not escape. The ring member 32 is sometimes referred to as the expansion ring and preferably fits within a suitable internal groove 33 formed upon the inner surface of the tubular section 24. Such an expansion ring can be easily moved into position in a contracted condition. When released, it will expand into said groove and into a desired sealing position.

The rabble arms, such as I5a, I50, are disposed near the extremities of the tubular sections 2|, 24 and therefore near the cooperating groups of fingers or lugs 26, 21 and 30, 3|, respectively. Because of their proximity to their respective groups of cooperating fingers, no appreciable expansion differential can occur which will misalign said arms. That is, the distance between rabble arms I51; and the cooperating fingers 26, 21 is 'sufficiently small so'that any expansion differential between tubular'sections 2| and 24 will not disturb the alignment of said arms relative to arms I5c to an undesirabledegree.

The association of the inner tubular sections :23 and 125 with.ltheir: respective:'lduterttubular sections Zfltand 22" is effected by means identical .tothose described for tubular sections "2| and --24.- .1For example,'section 22, by-meansof fingers .34. thereon,isnassociated with'isection 25 upon 1' fastened flanges 21a, 22aland-byvirtue of the proximityof fingers 26, 2l--and 34, 35. *In operatiomwhenithe furnace shaft is heated within the furnace, the outer tubular sections will be heated to agreater extent than the inner tubular sections and hence will expand both radially and longitudinally to a greater. extent than the inner tubular sections. The relatively .greater radial expansion is accommodated by virtue of the factfthat the fingers on the .outer sections can move radially away from the fingers on the inner sections. And the relatively greater longitudinal expansion is accommodated by the axial separation 'of 'each inner tubular section into two subsections.

Instead of locking the opposite extremities of correspondinginner and outer tubular sections against relative longitudinal movement and splitting the inner tubular section as at Ma, it is desirable under some circumstances to clamp together only one extremity of corresponding -in ner and outer tubular sections and to employ at the opposite extremity a studand shank arrangement as indicated in brokenlines in Fig: 7 which will so associate the cooperatingfingers that relative rotation will be prevented but some relative longitudinal motion can occur. Such a stud and bolt device is indicated at 28d and differs from the one originally described in that the shank or the stud is longer than that of stud 28a. If the inner and outer tubular sections are associated in this manner, it is desirable for each such section to have but one set of rabble arms thereupon and this set preferably should be mounted adjacent the tightly held extremities of said sections, namely, in proximity to the extremity which is locked against relative axial movement.

There are thus provided novel means for associating the inner and outer tubular sections of a rotatable furnace shaft. The means are very simple in construction and are inexpensive to manufacture and rugged in construction. The novel means eliminates almost entirely the possibility of furnace breakdown due to fracture of ribs or fingers which interconnect said inner and outer tubular sections. Moreover, it assures the maintenance of a proper alignment between rabble arms mounted on the shaft and enables the inner tubular sections to provide a driving torque to the rabble arms without the disadvantages which normally accompany an expansion differential between inner and outer tubular sections. The connecting members for holding in radial alignment cooperating fingers upon said sections insure the transmittal of a proper torque to the inner tubular sections whereby relative angular movement therebetween is prevented.

Although the invention has been described in c'ennectiomvithai-ii preferred-examples it is to be expres'sly-un e'rs'tobd' th'at the invention is not limited theret'o. For example-instead of forming a severance li as 'at -24d, upon each inner tubular section possible originally to form each inne' sectlon in two 'separate subsections 2 7 I In thecopendihg application--of Charles W. Nichols Ser. -No' '65l, 537, filed- March 2,1946, certain' alternative constructions are disclosed and certain featur" of the'present invention are claimed, .I' 1. 1; 1.1: 'ITLQL. I... L -:.i It will be understood by those skilled in the art, after! uiiderStanding' the invention,- that various. changes and modificati'ons' may be made without departing 'from the spirit and scope of -.the invention, 'and it is intended therefore in the appended claims to cover 11 such changes and modifications. l 1 What is claimed as new and-' is desired to be secured byLLettersPatent is: 1 I

-- 1. Acombination"of'parts for use in a furnace of a type having rabble arms carried bya central shaft comprising'an'inner' shaft, a plurality of outwardly extendingflugssecure'd to said inner shaft, an outer surrounding shaft having inner wall surfaces spaced from said inner shaft, a like plurality of inwardly extending lugs secured to the inner wall surfacesof-"said outer shaft, anda like plurality of members for connecting corresponding lugs upon said inner and outer shafts for holding same "in radial aligmnent.

' 2. A combination of'parts" for usein a furnace of a type having rabble arms'carriedby' a central shaft, comprising an inner shaft, a plurality" of outwardly extending fingers secured to saidinner shaft adjacent each extremity thereof,'an outer surrounding shaft having'the inner wall surfaces thereof spaced'from said inner shaft, a like plurality of inwardly extending fingers secured to the inner wall surfaces of said outer shaft adjacent theextremities-thereof, and alike plurality of finger interconnecting members for holding in alignment corresponding fingers upon said inner and outer shafts, said inner shaft being formed into two subsections intermediate the extremities thereof.

3. In apparatus of the class described, an inner tubular member, a plurality of outwardly extending fingers secured to said member, an outer tubular member surrounding said inner member, a like plurality of inwardly extending fingers secured to the inner surface of said outer member, and mechanism for holding in alignment corresponding fingers upon said inner and outer members.

4. A combination of parts for use in a furnace of a type having rabble arms carried by a central shaft, comprising an inner tubular member, a plurality of outwardly extending fingers secured to said member near each extremity thereof, an outer surrounding tubular member having inner wall surfaces spaced from said inner tubular member, a like plurality of inwardly extending fingers secured to said inner wall surfaces near the extremities of said outer tubular member, a like plurality of members for holding corresponding fingers upon said inner and outer tubular members in radial alignment, each of said inner tubular members being separated into two separate sub-sections intermediate the extremities thereof, said sub-sections being in abutting relation when there is no expansion differential between said inner and outer members but being subject to separation in response to a greater expansion of said outer member relative to said inner member, and a ring member mounted between said sections for sealing the region of separation therebetween.

5. A combination of parts for use in a furnace of a type having rabble arms carried by a central shaft, comprising an inner tubular section, a plurality of outwardly extending fingers secured to said section near each extremity thereof, an outer surrounding tubular section having inner wall surfaces spaced from said inner tubular section, a like plurality of inwardly extending fingers secured to said inner wall surfaces near the extremities of said outer tubular section, and a like plurality of members for holding corresponding fingers upon said inner and outer sections in radial alignment, said inner tubular member being separated into two separate sections intermediate the extremities thereof.

6. A combination of parts for use in a furnace of a type having rabble arms carried by a central shaft, comprising an inner tubular section, a plurality of outwardly extending lugs secured to said section, an outer surrounding tubular section having the inner wall surfaces thereof spaced from the inner tubular section, a like plurality of inwardly extending lugs secured to the inner wall surfaces of said outer tubular section,,and a like plurality of lug connecting members for holding each lug upon one section in cooperation with a corresponding lug upon the outer section, each connecting member being constructed and arranged to hold each pair of cooperating lugs against relative longitudinal and angular displacement.

'7. A combination of parts for use in a furnace of a type having rabble arms carried by a central shaft, comprising an inner shaft formed of tubular sections, a plurality of outwardly extending lugs secured to said sections near each extremity faces spaced from said inner shaft sections, a like plurality of inwardly extending lugs secured to the inner wall surfaces of said outer surrounding tubular sections, a like plurality of clamp members for clamping in alignment corresponding lugs upon said inner and outer tubular sections, means for securing together adjacent ends of said outer tubular sections, each of said inner tubular sections having a frangible portion formed circumferentially and intermediate the extremities thereof, and an expansible sealing ring mounted internally of each inner tubular section in alignment with each frangible portion. 7

8. A combination of parts for use in a furnac of a type having rabble arms carried by a central shaft, comprising an inner shaft formed of tubular sections, a plurality of outwardly extending lugs secured to said sections near each extremity thereof, an outer surrounding shaft also formed of tubular sections having their inner wall surfaces spaced from said inner shaft sections, a like plurality of inwardly extending lugs secured to the inner wall surfaces of said outer surrounding tubular sections, a like plurality of lug interconnecting members for holding in alignment corresponding lugs upon said inner and outer tubular sections, and means for securing together adjacent ends of said outer tubular sections.

CHARLES W. NICHOLS. JOSHUA GREENSPAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,464,396 Rowland Aug. 7, 1923 1,732,843 Halse Oct. 22, 1929 1,899,922 Black Mar. 7, 1933 2,332,387 Martin Oct. 19, 1943

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