US1992964A - Centrifugal basket construction - Google Patents

Description

Patented 5, 1935 states when rarest was I Western States Machine Eompazoy, halt City, iii-ah, a corporation oi t'ltah Application February 25, i933, serial No, Gdfidl This invention relates to baskets for centrifugal separators oi the type. used in the manufacture of sugar, starch and various chemicals and is intended to provide a construction of basket that shall be free from faults inherent in the type or construction that has previously been known and used in such centriiugals.

According to the practice heretofore followed a perforated metallic sheet of appropriate length and thickness was rolled into cylindrical form and its abutting edges were fastened together by means of butt straps. The perforations in the sheet extended close to the top and bottom edges and were arranged in circumferential perforated areas separated by intermediate circumferential areas that were left imperforate for the reception of external reenforcing hoops. Said abutting ends were fastened together by a series of vertically spaced butt straps which were curved strips of sheet material as thick,- or thicker than the basket wall overlapping the perforated areas for several inches on each side of the joint or crack in the basket wall. These straps were se- 4 cured to the wall by multiple rivets passed 25 through perforations in their ends that were in registry with corresponding perforations in the basket wall. To balance the basket, it was necessary to apply two additional sets of similar straps 12c degrees from the butt straps and res,- tened to the basket also by rivets.

The top and bottom elements of the basket were then applied to the corresponding edges of the. basket wall in lappedrelation thereto and were .fastened to it by bolts, pins or rivets. The

35, reeniorcing hoops passed between the individual straps of each row of butt straps.

For many years the baskets in use have been.

of this type of construction, although it was recognized that their operation in service was attended by a very considerable waste of material being treated. Notmnly were thebaskets subiect to leakage around the top and bottom edges of their filter linings, but miles the sugar being centrifuged was subjected to excessive applicapicks up the scum) the loss'of sugar averages seven pounds for each pound of hot water applied; Moreover, imperfect drainage prolongs tion of wash water there would be found rings (or. ere-rs) Q the purging period, that is, the centrifugal extraction of the original syrup or liquor with which the grains were mixed, and makes the washing operation longer and more difiicult.

' After careful study or" andexperiment with 5 centrifugals in attempting to learn the causes of these troubles, I have discovered that the large percentage of waste involved in the operation of such centrifugal baskets was due to,several faulty features of construction, whose disadvan- 1o tages have been entirely overlooked heretofore. The importance of uniform drainage throughout the whole perforated area of the basket wall has not been appreciated or, if it has been, no

basket construction has been provided to secure :15 that advantage. In the first place, the use of butt straps and counterbalance straps, as well as the use of overlapping flanges forming top and bottom riveted joint connections with the basket wall, has resulted in doubling the thickness of the basket wall at such locations with the consequence thattlie depth or radial length of the outlet perforations in the double thickness areas was alsodoubied. Careful tests have shown-me that these longer outlet perforations tend to gum up or accumulate sticky material until their dis "charge capacity is very greatly reduced. In addition to this, some of the holes are closed by the attaching rivets. Therefore, substantial areas ofthe basket wall will have less than half so the freedom of drainage that equal areas in other parts of the basket have. The result is that after purging and moderate washing there will befound. discolored streaks and patches of sugar, which are highly objectionable asisuch sugar is of inferior grade. .Oh the other hand, if these discolored areas are washed out by suficient washing the portions 0! the sugar wall having freer drainage become excessively washed, involving excessive wastage, which is I also highly uneconomical and objectionable.-

'{By means of the construction hereinafter described I have eliminated perforated areas of double thickness of basket. walland have also eliminated the'use of fastening rivets which have 5 been used for fastening overlapped perforated members together and which necessarily close a considerable number of such perforations and have thereby secured, for the first time in this art, a perforated centrifugal basket for sugar cenia'iiugals and the like, which have uniformly. spaced outlet periorations of uniform depth 61- radial length so that all portions of the perforatedareaofthebasketwallpossessequaldrain- I age facilities, thereby avoiding the occurrence 56 tion of washwater, largely reducing previous wastage. Moreover, by reason of the equ l and free drainage thus secured, the purging can be accomplished'more perfectly and more quickly than before, which of itself aids in dispensing with the use of considerable quantities of wash water, since much of the scum is carried off by the freely flowing liquor or syrup extracted in the first portion of the runbefore the wash spray is applied.

top and bottom edges of the basket filter linings is avoided by spacing the top and bottom rows of perforations a substantial distance from the top and bottom elements, thereby providing a smooth unbroken surface of sufficient extent to form an adequate support for the salvage edged linings with which these smooth unbroken top and bottom margins or selvage areas of the hasket wall form an effective seal permitting the use'of linings that are slightly shorter in verticalheight than the vertical distance between the top and bottom elements next to the basket wall. Besides providing aperfect sealing seat for the top and bottomedges of the these smoothunbrokenselvage areas serve to prolong the life of the fine linings, since in being crowded tightly against the top and bottom in the effort toprevent leakage of material at those points they become bent and crumpled at their edges under pressure exerted by the discharger I plow, which is a prolific source of damage to. the linings. Moreover, the selvage margin areas of the basket wall afford a much stronger and more reliable joint with the top and bottom elements of the basket than was obtained by previous constructions;

.Theseand other features of theinvention will.

- be particularly described in the following speck fication and'will be defined in the claims hereto annexed. In the accompanying drawing I have illustrated a preferred form embodying the principles of this invention, in which Fig. 1 isa side elevation, partly in central section, of my improved basket construction showing the basket'in its relation to: the surrounding curb or casing.

Fig. 2 is a detail showing in perspective on a larger scale the joint between the bottoms and the basket wall and illustrating the calibration of the bottom for the purpose of ascertaining the thickness of the sugar wall as the basketis beingloadedr' 2' a Fig. 3 is an enlarged detail. showing a vertical section through the upper portion of the basket wall and top.

. mg. ais a detail showing in when on as same scale as Fig. 3 the arrangement of perfora-' tions of the basket wall.

4 is an enlarged detail in plan of the abut ing ends "of the sheet forming the peripheral wall with their-uniting weldingfseam In'the practice of this invention I avoid double thickness of the perforated areahof the basket wall by elimination of the butt straps and counand of overlapping joints having outlet perforations by making the basket of integral consu-uction.:'the eby u ing uniform dcpth of the outlet perforations and distribution or spacing'Tof such t-the perforatedprea of'tfuev mama and rapid'drainageis-af construction and arrangement by which these important advantages are secured. The suspension shaft 1 of the centrifugal, according to usual practice, is provided at its lowerend with r a frusto-conical enlargement 2 and a downward extension 2 of reduced diameter for the purpose 7 of receiving the hub 6 concentric with the ra- Waste of material through leakage around the able to shorten the vertical depth of the peripheral ring '7'sufiiciently'to allow-this ring, when the basket gyrates, to swing over the top of the.

interior flange 20 bounding the central discharge opening in the bottom 20* of the curb or casing. This upward inclination of the spider 5-, with the corresponding-thickening of the hub and peripheral ring thereof, makes it possible to provide a collecting trough or ring for the bottom of the curb or casing of much -greater width than was practicable with previous constructions in this type of centrifugal without sacrifice of strength.

The perforated'basket wall 10 comprises a metallic sheet provided with uniformly spaced and dimensioned perforations throughout the whole perforated area of the basket, while at the same time providing at the top and bottom marginal portions of the basket wall selvages or imperiorate' areas 10 and 10 for the reception of my selvage edge lining or backing, which forms the. subject matter of -a companion application, and

prevents leakage of the material around the lin-- ings at the top and bottom edges thereof. Not onlyis the pitch or center to center distance from. one perforation to the next in the same row of perforations the same, but the pitch or distance from center to center of successive rows .of perforations is also uniform throughout and in consequence thereof there is uniform and equal drainage throughout the basket forthe escapevof the centrifugally extracted liquid. Furthermore, I

the radial depth of all perforations in the basket is uniform throughout, since there are no rows of butt straps secured to the basket wall and rivetsplugging a substantial number'of the perforations by reason of the construction that will now be explained.

The perforated sheet is rolled into cylindricalv form and its opposing ends" are cut of! true and even and bevelled at their edges, and are then drawn tightly together by circumferential clamps provided with draw bolts. These abutting endssheet 10, while the shell is held in cylin-' drical form, are then welded together throughoutthelemth of the seam from top to bottom, thus making an integral connection between. the two ends. The inside and the outside "of the welded seam are then .groundsmooth. v a

The top and bottom edges of the integral cylin vdrical sheet to'form the basket wall are then turned to form'a snug fit with the top and bot-- tdm'elements of the basket; the bottom is then forced into the inside of thebottom'edge until its outer'odgelies flush with the bottomedge of the top 12 isthen crowded Over the top edge against intervening vertical spacers and the top and bottom are then drawn together against the intervening spacers to secure exact parallelism as well as proper engagement with the edges of the basket-wall." When thus exactly positioned with reference to each other and to the basket wall, the top and bottom elements are. exactly 'equi-di'stant from each other all around the basket and a continuous welded seam is made between the bottom and top elements while they are held in that relation. In the case of a steel basket, the continuous welded seat at top and bottom will preferably be formed by arc welding. In case of bronze or similar alloys the welding is preferably done by oxy acetylene methodof welding.

The hoops 13 are turned or machined inside to slightly smaller dimension than the periphery of the basket wall and are then heated and forced over the basket wall in proper spaced relationship insured by temporary spacers. These hoops are shrunk tightly on the basket wall by cooling and are held against accidental displacement by spot welding at intervals around the basket wall, as shown at 13 such spot welding preferably being made alternately on the top and bottom sides of the hoops. The bottom hoop is the last to be applied and after its application is integrally welded to the bottom marginal portion of the V basket wall by a continuous welding seam ex-.

tending entirely around the bottom. As the besket bottom has already been integrally united with the inside face of the lower edge portion of the basket wall by a continuous welding seam, asabove explained, this continuous welding of the bottom hoop forms, in efiect, a peripheral integral extension of the bottom member and there fore the shocks, caused by its impact against the surrounding wall oi the curb or casing as the basket gyrates or sways, are transmitted directly to the basket spindle and there is no danger of the hoop becoming loosened and dropping ofi, which occasionally happens with consequent -damage to the basket when the hoop is secured I in strength but which efiects a much more complete and satisfactory drainage than in the-case of previous constructions, and also makes provision for the elimination of leakage of material to be purged around the top and bottom edges and permitting the use of a collecting trough for the liquid oi any desired width instead of being restricted to the narrow widths heretofore necessitated by previous constructions. There are no rivets to shear or to clog drainage openings and no butt straps to impair complete ef iciency of drainage.

The outer portion 8 of the basket bottom 4. is provided with a series of accurately spaced gauging grooves or rings 4 so that the centrifugal operator or attendant guided accurately in loading the basket. These calibrating or gauging rings at will preierably be located an inch apart, the outer one of these being one inch, or unit of measurement, from the inside of the basket wall, so that if it is known that the inner ring of any given basket, for example, is 7 inches away from the basket rial 4 it is desired to load some parinches and correspondingly any other desired thickness may be indicated by similar manner, thus enabling the operator to load to any desired thickness of wall according to the material that is being purged. A further important advantage of the visible calibrating of the basket bottom is that it makes possible the accurate ascertainment of the amount of shrinkage in the thickness of the bottom portion of the sugar wall, thereby affording a check on excessive washing or leakage of material. When the material being cen triiuged is loaded into the basket it builds up into a vertical annular wall inside of the outside wall of the basket andnormally this walled up ring oi material is thicker at the bottom than at the middle and top portions and therefore should re ceive a slightly greater supply oi? wash fluid than the upper portions of the walled up ring receive. .Thereiore, by providing a calibrating means on the bottom the shrinkage can be checked up -for the purpose of determining precisely. how much more spraying is required over this area and also to detect'the fact of over-spraying which will cause excessive shrinkage and consequent waste. s

In actual practice I have made the imperiorate marginal portions 10 and 10 of the perioratedbasket wall at top and bottom approximately one-half inch in width, or a little wider than the diameter of the outlet perforations, although this dimension is not prescriptive. These smooth marginal or salvage areas the basket wall atford a smooth uninterrupted annular seat at top and bottom iormlng'a continuous sealing support for the upper and lower selvage edges of the basket filter linings. This is important because baskets, as previously constructed with the top and bottom rows of outlet perforations very close to the top and bottom elements of the basket, I have found are a prolific source of leakage of material at these points. Furthermore, in the attempt to lessen leakage it has been customary to endeavor to fit the finely perforated filter linings snugly between the top and bottom walls with the result that this fine lining has become curled up or distorted under the pressure of the discharger plow so that leakage oi material at both top and bottom occurs. en the above described marginal selvages are used, it is unnecessary to have the finely perforated filter lining fit snugly between the top and bottom of the basket and the 2 may be made slightly shorter than the vertical distance between top and bottom to allow for expansion and as the sealing at topand bottone is effected by the smooth contact of the selvage portion or" the outer lining or backing with these smooth salvage areas 0?": tr e basket wall, leakage presented and the life or duration of trifugals in operation. To get the fullest advantage of these imperiorate salv ge areas 1 have devised an improved basket iinug havin top and bottom sealing sel /ages, but such oved lining forms the subje t matter of and-Aer copending application filed by me.

By shortening the outer ring oi the bottom spider h compensating thickening of the ring, new baskets of this on in wide trough v diameter 2ok while 4 the collecting trough of the curb to an undesirable extent.

metallic sheet bent into cylindrical form with its abutting end edges integrally welded together and having uniformly spaced outlet openings, all of which are of equal radial depth throughout whereby equal and uniform drainage is afforded for the escape of the. centrifugally ex tracted liquid from the walled up material in the basket.

, 2; A centrifugal basket of the type described comprising a perforated peripheral wall of uniform thickness" throughout, thereby .providing outlet perforations of uniform depth radially of the basket, and top and bottom elements 'united therewith, the top and bottom rows of perforations being spaced a substantial distance from said top and bottom elements to leave a smooth unbroken annular selvage area of adequate width to form a smooth sealing contact with the subby providing a perforated wall of uniform thickness having outlet perforations of equal radial depth throughout, and top and bottom elements of appropriate form united to the top ,and bottom edge portions of said wall.

- 4. A centrifugal basket of the perforated wall type embracing a perforated cylindrical basket wall of uniform thickness throughout, comp ing a metallic sheet bent into cylindrical form with its end edges integrally united in abuttingrelationship, thereby providing. outlet perforations of equal depth uniformly spaced apart, top and bottom elements united thereto by continuous welding seams, and a series of vertically spaced external reenforcing hoops secured around the basket wall and held in fixed spaced relationship to each other by spot welding.

EUGENE RonERTs.

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