US2025690A - Classifier - Google Patents

Description

Dec. 24, 1935. c. K. MCARTHUR CLASSIFIER 2 Sheets-Sheet 1 Filed Oct. 12, 1932 W Y RW.M m R m C. M A K C.Y B

Dec. 24, 1935.

c. K. MOARTHUR 2,025,690

CLASSIFIER Eiled Oct. 12, 1932 2 Sheets-Sheet 2 c. K. MC ARTHUR BY W Gland.

ATTORNEY always submerged during operation may be short- Patented Dec. 24, 1935 CLASSIFIER Charles'K. McArthur, Denver, 0010., assignor to The Dorr Company, Inc., New York, N. Y., a corporation of Delaware Application October 112, 1932, Serial No. 637,392 In Chile May 27, 1932 6 Claims.

This invention pertains to classifiers of the oscillating or reciprocating raking blade type. More particularly, it relates to the 'blade construction thereof, and the manner in which the blades are mounted.

The object of the invention is to improve the operation and emciency of classifiers. To this end it is the aim of this invention to eliminate a certain type or degree of agitation from the classifier bathor pool, .which has been found to be undesirable.

The nature of the invention resides in preventing, as far as practicable, harmful agitation in the classifier pool or bath. There are two types of agitation which I have found to be detrimental to classification, if they are excessive, and they are agitation in a horizontal direction and in a vertical or longitudinal direction. The raking blades set up longitudinal agitation while the beams which support the blades set up horizontal agitation. Therefore, this invention comprises diminishing the area of these surfaces.

It has been discovered that shorter blades may be used in certain zones of the classifier than in others. For instance, those blades. which are ened to reduce the agitation of thebath caused thereby without diminishing their classifying action. In fact, by shortening them, their classifying action is improved. But this is not true of those blades which are not submerged or of those which are alternately submerged in and emerged expense of fabricating each blade with a different height from its adjacent blades, it is proposed herein to form adjacent groups of blades with different heights so it will not be necessary to make so many diiferent sizes of blades.

The group of blades lyingin the zone of emerg ence from the, classifier bath are of full height and so are the group of blades coacting with the non-submerged part of the classifier deck for both groups are depended upon for raking capacity and this cannot be interfered with.

However, the effectiveness of this lessening of blade-height toward the overflow end of the classifier can be supplemented by eliminating-as far as possible all horizontal surfaces from the blades and their supporting elements .or stringers. Heretofore, the stringers have usually been formed of angle iron which presents horizontal surfaces to the classifier bath. Such surfaces slap the liquid of the bath with the consequent undue. displacement of the liquid and this has been found to be harmful or detrimental to efficient classification. Therefore, I desire to use stringers which present to the liquid, vertical edges-only, during oscillation of the blades.

The invention possesses other objects and features of advantage, some of which, with the 10,

accompanying'drawings which are shown in an 15 illustrative sense and not a limiting one. In the drawings, Figure 1 is a vertical sectional view through a classifier of the oscillating rake blade I type; Figure 2 is a set elevation showing the manner of mounting the raking blades; Figure 3 is a plan view of the device of Figure 2 while Figure 4 is a partially prespective view showing the blades and the manner of mounting them.

Except for the blades and their mounting, Figure 1 shows a standard classifier of the well known Dorr type having a tank I for containing a bath II ofpulp .to be classified. l2 indicates the inclined deck of the classifier, l3 the infiuent launder therefor, M the sand discharge or upper end and I5 the overflow end for the fines. I6 represents the inclined deeper end of the classifier tank; I! indicates the liquid level of the pulp in the classifier. l8 represents the raking blade while l9 represents their linear supports. The supports l9 are provided with hangers and 2| as is usual. Operating on the hangers is a usual group of mechanisms M for causing the blades to be oscillated in the usual D-path. 22 represents that part of the inclined classifier deck l2 which extends upwardly above the liquid level I! of the classifier bath l l As this invention relates to the blades and their 4 method of mounting, the foregoing paragraph is merely descriptive of a usual classifier with only enough parts identified to-understand their relationship and the points of invention described hereinafter. In a usual classifier the blades l8 are ordinarily mounted on or depend from a pair of channel irons or bars 23 having right angles or substantially horizontal flanges 24. The blades are normally secured to the bottom horizontal fianges by clips 25. But thefianges 24present rather broad substantially horizontal surfaces to the blades and their channel irons 23 are caused to oscillate by their driving mechanism M' and follow a path substantially D -shaped with the D set over on its face. That is, tl ,e upstroke is substantially parallel to the inclined deck 12 while the return or downward stroke is substantially semi-circular. On the return stroke, it can be seen that horizontal surfaces tend to slap the liquid and set up undesirable eddies and other forms of harmful agitation.

- Therefore, this invention has been made to overcome and prevent such undesirable agitation by eliminating from that part of the blade supports which are submerged in a classifier bath as much as possible of any flat or substantially horizontal surfaces. The horizontal surfaces are not troublesome in that part'of the blade supporting channel bars which are located above the liquid level, so it is preferred to retain such construction in that part of the classifier. But in that part of the classifier blade supports which is submerged, it is desired to form the blade supports or stringers 26 of vertical, flat plates, which have a minimum of angular or horizontal extensions or flanges thereon, so that during mcillation the stringers 26 only present edges 21 to the classifier bath. These stringers 26 are secured to and form a linear continuation of the channel bars 23 to which they may be secured by any suitable means such as by fish plates 28. The blades l8 may be secured to the stringers 26 in any suitable way but preferably by being inserted in notches 29 formed in the stringer plate 26. The top edge of the blades are inserted into the notches 29 and are held therein by some means such as welding.

Another feature of the blade construction is to have the blades or teeth l8 of different depths or heights. The ideal would be to have the blades of full height from the zone of blade emergence from the bath I I upwardly to the sand discharge end IL: But from the zone of blade emergence downwardly to the deep or inclined end of the classifier, the blades should be progressivelylessened as to height. However, it is expensive to make so many blades each of different heights, so a happy medium is struck by having groups of blades with each group of blades of different heights. One group is represented by 30 and another group by 3|. Although only two such groups have been described, it is to be understood that they are representative for more groups of different height blades may be used if desired.

Thus theinven'tion .resides in graduating the depth of the classifier blades from a maximum just beneath the pulp level to a minimum at the overflow end of the classifier, and, in a method of mounting and securing the blades to their stringers, with both of these points contributing to a unitary result of improved classification.

From an inspection of Fig. 1 it will be noted that there is a series'of transversely extending blades of shortest height arranged in a longitudinally spaced relationship at and along the lower end of the flat plate stringer sections of the inclined rake structure, that there is a series of transversely extending blades of greatest height arranged in longitudinally spaced relationship at, along and also depending from the under side of the structural extension at the upper end of the rake structure, and that there is a series of transversely extending blades. of intermediate height arranged in longitudinally spaced relationship along an intermediate portion of the 2,025,690 This can be understood when it is considered that rake structure and more particularly an intermediate portion provided by the flat plate stringer sections that are submerged, whereby the series of blades of shortest height and the-series of blades of intermediate height are in the sub- 5 merged section of the classifier. The several blades of any one series are of the same height in the embodiment illustrated. It will also be seen that the bottom transverse edges of the blades of each set or series lie in a common relatively longitudinally extending but inclined plane, and in such a manner that the plane for the set of transverse blades of greatest height is positioned nearest to the sloping bottom, so that the plane for the transverse blades of 15 the set of least height is furthest from the sloping bottom, and so that any plane common to a set of blades of'intermediate height, lies in respect to said bottom, in a position intermediate the said planes which are positioned nearest and 20 I the notches of the fiat plate stringer sections are all of the same depth, whereby the bottom edge portion of the series of blades of different heights 25 become positioned with respect to each other as above pointed out.

In this embodiment it is also noted that the connnection betweenthe longitudinal flat plates or stringers and the transverse blades are to form 30 substantially simple intersections of the respective planes of the stringers and the blades carried thereby.

A classifier manufacturer is faced with the requirement of increasing the raking capacity of the blades, and yet if he does this, he will get ex-. cessive agitation in the classifier bath. So this invention is based on the discoverythat by making the blades shallower in the overflow end of the classifier and gradually deepening them until 40 their maximum depth is reached just before emerging from the classifier bath or pool, the full advantage of deeper rakes is retained for increasing their raking capacity while. avoiding the usual disadvantage of deeper blades interfer 4! ing with the settling or classification. That is, increased raking capacity is had where it is needed while excessive raking capacity is avoided where it is not needed or would otherwise give a harmful increase of agitation in the overflow 50 zone of the classifier bath. And what has been said about blade depth applies equally. to the avoidance of broad substantially horizontal surfaces in the overflow zone of the classifier bath.

It is desired to minimize vertical agitation due ment of the invention has been shown and de- 60 scribed for illustrative purposes because obviously. many changes of details and of construction are possible without departing from the spirit of this invention, as for instance, the stringer plate 26 can be extended the whole length of the classi- 6 her, if desired, so that there are no channel members or bars 23. In the same way the blades can he graduated as to height in any desired manner or degree so long as the shallower blades are in the deep end of the classifier and the taller blades are in the discharge end. However, the construction shown is the preferred one.

I claim:

1. In a classifier wherein there is a tank that has a sloping bot om in operative relation with 79 respect to which there is employed an oscillating rake construction, and which tank has a liquid overflow leading therefrom whereby the level of liquid within the tank is maintained intermediate the ends of the rake so that the rake has a submerged portion and a non-submerged portion, and which classifier is characterized in that said rake construction thereof is provided as to the submerged s'ection thereof with stringers formed of flat plates extending vertically and relatively longitudinally with respect to said bottom and to which flat plates there are attached transversely extending bladesjn a manner to form substantially simple intersections of the respective planes of said plates and said blades, and as to the relatively non-submerged sections of said rake construction is provided with flanged structural shapes forming extensions of said flat stringer plates by being suitably connected thereto, and to which structural extensions there are secured transversely extending blades that extend downwardly from said structural extensions.

2. In a classifier wherein there is a tank that has a sloping bottom, mechanism providing an oscillating rake structure which has operative relationship with respect to said sloping bottom, and a liquid overflow whereby the level of liquid within the tank is maintained in such a manner that the rake structure has a submerged portion and a non-submerged portion, and which classifier is characterized in that said rake structure as to the submerged portion thereof has stringer sections provided by flat plates extending perpendicularly and relatively longitudinally with respect to said sloping bottom wherein edge pornected through the medium of connecting plates to said flat plates, and to the under side of the bottom flanges of which said structural extensions there are secured the upper portions of transversely extending blades that extend downwardly from said structural extensions.

3. A classifier having the usual tank with sloping bottom and a partially submerged oscillating rake construction, the rake of which is cooperatively related to said sloping bottom for conveying settled solids upwardly along said bottom to emerge discharge and for overflowing fines in suspension and is characterized in that the rake thereof comprises relatively longitudinally extending stringers to which there are secured in longitudinal spaced relationship three or more sets of transversely extending blades in which the blades of each set are all of the same height,

which sets of blades are arranged so that the blades of least height are at the lowermost submerged end portions of the rake stringers, so

\ that the blades of greatest heightare at the upper discharge end portions of the rake stringers, and so that the blades of intermediate height are located between said other two sets ofblades, the arrangement ofthe blades of each set being such that the lower transverse edge portions of the I several blades of a set terminate substantially in a common longitudinally inclined plane substantially parallel to the sloping bottom, therelative ,arrangement of said sets being such that said lower edge portions of each set project beyond those of the preceding lower set, said rake being positioned and operated in the tank so that during its-upward operating movement the plane of the blades of shortest length is furthest from the sloping bottom and so that the plane of the 5 blades of greatest height is nearest the sloping bottom.

4. In a classifier as defined in and by claim 1, a rake in which the transversely extending blades thereof are arranged in sets and so as to include at least three sets, in each of which sets the. blades are of the same height and which sets of blades are arranged so, that the blades of least height are at the submerged end of the rake, so that the blades of greatest height are nearer the discharge end of the plate, and so that the blades of intermediate height are located between the sets of greatest and least height, the arrangement of the blades of each set being such that the lower transverse edge portions of the several blades of the set lie in a common longitudinally extending but longitudinally inclined plane, said plate being positioned and operated in the tank so that during its forward upward operative movement the'plane of the blades of shortest length is furthest from the sloping bottom and the plane of the longest blades is nearest the sloping bottom, and so that the plane for all other sets of blades lies intermediate the first set of blades which are furthest from and nearest to the 80 sloping bottom.

5. In a classifier wherein there is a tank that has a sloping bottom mechanism providing an oscillating rake structure which has operative relationship with respect to said sloping bottom, 86 and a liquid overflow whereby the level of liquid within the tank is maintained in such a manner that the rake structure has a submerged portion and a non-submerged portion, which rake structure has an oscillating movement that includes a 40 downward component substantially perpendicui lar to the sloping bottom, and has stringer sections provided by vertically and relatively longibetween said longitudinal flat plates and said Iv transverse blades being of a type to form substantially simple intersections of the respective planes of said plates and saidblades, and wherein blades of different heights are employed in the submerged section of the rake, the arrangement of the blades relative to each other and to the tank bottom being such that blades of greater height follow blades of smaller height with increments progressing in consecutive order toward the upper portion of the rake structure, said rake structure being positionable and operable so that during its upward operating movement the lower edges of the blades of shorter height are further from the sloping bottom than the blades of greater height. H

6. 'A classifier arranged as to rake structure so I that there is avoided much of the harmful agitation which would otherwise be experienced in the classifier bath, comprising a tank formed with a sloping bottom and adapted to hold a bath of pulp to be classified, and a cyclicly oscillatable rake structure partially submergible in the classifier bath for raking upwardly alongthe ing flat plates, and a plurality of raking blades carried by said stringers transversely thereof, said blades being formed into a plurality of sets of blades, certain sets of blades being wholly below the water line and being formed of vertically extending flat' plates, the blades of any one submerged set being of substantially the same depth but the blades of the different sets in sub-'- mergence being of unequal depth with those of the least depth being in the deeper portion of the tank.

CHARLES K. MCARTHUR.

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