US2191743A - Classifier mechanism - Google Patents

Description

4 Sheets-Shet 1 INVENTOR fiY/fl/PZFJ scarr,

ATTORNEY.

c. H. SCOTT QLASSIFIER MECHANISM Filed Jan. 26, 1938.

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Feb. 27, 1940.

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flHmHu HHHL Feb. 27, 1940. c. H. SCOTT CLASSIFIER MECHANISM Filed Jan. 26, 1.938 4 Sheets -Sheet 2' TNVE'NTOR,

Feb. 27, 1940. c. H. SCOTT 2,191,743

GLASSIFIER MECHANISM Filed Jan. 26, 1938 4 SheetS -Sheet 5 I is: In 6-2. in,

ATTORNEY.

Feb. 21, 1940. c.H.SOTT -2,191.143

CLASSIFIER MECHANISM lilod Jan. 26. 1938 4 Sheets-Sheet 4 Ha e Q m V INVENTOR. I

- Cf/fi/PZFJ 19.60077;

' ATTORNEY.

Patented Feb. 27, 1940 UNITED' STATES PATENT OFFICE CLASSIFIER. MECHANISM Charles H. Scott, Westport, Conn, assignor to The Dorr Company, Inc., New York, N. Y., a cor-- poration of Delaware ApplicationJanuary 26,,1938, SerialNo. 186,942

20 Claims. (01. 19s' 224 10 tially'submerged sloping bottom or deck of the tank.'

In the layout of ordinary classifiers the maximum depth of the bath is usually fixed by the degree of classification "to be attained so that a 15 critical limit for the slopev of the deck and the required depth of the bath determine the requisite length of the machine to get the rake product to be discharged in emergence, and consequently' depending upon the required depth of submergence such length may become'excessive, and the machine unwieldy, heavy, and expensive in first cost, operation and space requirements. The critical slope of the tank in turn depends upon the back' flow or "slippage of-the material 3.5 being raked upwardly along the deck; because the permissible retrograde flow of the burden of 7 each raking blade must be compatible with a requirement for' fair raking and conveying efli- I ciencyn t 30 Accordingly, the invention contemplates 'the design of a steep-slope classifier in which the degree of slope may be chosen independent of potential back flow or slippage of the material; in which maximum raking and conveying em- 35 ciency is attained within a minimum of classifier length; and in which the rake product is ele vated to a desired point of delivery within a restricted space and Without impairing the quality of separationintended to 'be obtained by the 40 classifier.

Therefore, one object of the invention is the design 'of an efiicient steep-slope classifier.

This object is attained broadly by intercepting and detaining or preventing retrogression of the 45 individual piles of solids or burden engaged by raking blades during the period of their release from the raking blades incident to each elevated and non-raking or idle return movement thereof by;the employment of interceptor plane face 50 portions having a general extent at right angles or perpendicular to-the plane of the sloping deck or bottom of the tank; 7

In one manifestation ofthe invention, this is realized through the coaction and kinematic 55 coordination of a set or sequence of reciprocable,

spaced, solids-raking blades with a corresponding set of solids intercepting and detaining gates or stopper blades, the coaction being that at the end of a raking stroke the detaining gates orstoppers descend directly in front of andsufliciently close to the raking blades to intercept and holdthe respective piles or loads of solids then engaged by each individual raking blade just long enough to allow for the return rearward elevated movement of the raking blades. The raking blades then descend directlyin front of the detaining gate or stopper blade to engage a new load of solids thus held ready for itby the stopper, whereupon the stopper blades rise so that the next vphase in the cycle of stepwise procession or progression of the solids may be effected by the raking blades. Novel features lie in the character of the raking diagram and the control mechanism for I carrying them out.

Accordingly, and "aside from the principle of stopper blade action, the invention also has to do with an improved rake actuating mechanism for carrying out a suitable and desirable diagram of the raking cycle and which is particularly suited in view of the action of the stopper blades. More in particular, this raking diagram is characterized by a steep or perpendicular descent at the end of the elevatedreturnstroke of the rake, relative to the sloping tank bottom.

Accordingly, it is a feature of the improved rake actuating mechanism as such that the up and down positioning movement of the raking structure is efiected by means of swingable track members journaled relative to the tank, each track member having individually and operatively associated therewith a rake suspension point or rather a track roller representing such asuspension point. More specifically," the actuation of such a rake suspension point is effected by way of a bell-crank-like member, one arm of which constitutes the swingable track, the other arm being actuated through cam control linkage from a drive shaft, the rotation of which'also produces the longitudinal reciprocating component movement of the raking cycle.,

An advantage isthat the provision of control cam means will impose upon the drive a minimum of load necessary for lifting andholding the rake in lifted position during the elevated return stroke of the structure. It is among the advantages that a, steep-slope classifier according to this invention combines with a rotarygrinding mill to make a compact closed circuit grinding system for metallurgical or other similar purposes, inasmuch as the steepslope construction of the classifier permits the point of rake discharge to be located close to and sufficiently high above the feed end of the mill to permit substantially direct gravitation thereto of recirculating load within a minimum of space and without the employment of auxiliary liftingdevices.

The invention possesses other objects, and features of advantage, some of which with the ,foregoing will be set forth in the following description.

for convenience, but they are intended to beas generic in their application to similar parts as the art will permit. In the accompanying drawings there has been illustrated the best'embodiment of the invention known to me, but such embodiment is to be regarded as typical only of many possible embodiments, and the invention isnot to be limited thereto.

Thenovel features considered characteristic of my invention areset-forth withz particularity in the appended' claims. The; inyentiontitself, how-- ever, both as to its organization anditsrnethod of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific'em bodiment when read in connection with the ac-,

companying drawings, in which: i H

vFig.1 is a plan view of a twin compartment classifier, each compartment equipped with solids f raking and solids intercepting bladed mechanism.

Fig. 2*is an end view taken upon Fig. 1.

Fig. 3 is an enlarged diagrammatic view-illustrating raking in a substantially triangular" diagram- Figs. 4- to '7 show 'variousoperatin'g phases of the solids conveying mechanism according to the invention.

Fig. 3 is a skeleton perspective view of the raking mechanism according to the invention;

Fig. 9 is an enlarg-ed detail of a connecting rod capable of automatic resilient telescoping foreshortening in the event of load obstruction or the like.

The classifier shown in Figs. 1 and Z is a twin compartment unit comprising the classifier com partments A and B. Each compartment is equipped with substantially the identical convey-ing mechanism according to the invention so that a description of one'com-partment and its mechanism will suffice.

The tank as more clearly illustrated in Fig; 4

has a sloping bottom ill or deck partially sub-j merged, side-walls l l, and an end wall I2 having an overflow Weir 83, a bath or solids suspension in the tank being indicated by the numeral M and the level of which is defined by the weir 53.

The mechanism as herein shown by' way of example comprises a rake structure consisting of a sequence of raking blades H5 having their ends fixed or welded to a pair of beams or stringers ll formed with an upper pair of hang? ers l9 and a lower pair of hangers 2i].

Cooperatively associated with the rake structure i5 is anvauxiliary bladed structure'or ln-' terceptor structure or stopper assembly 2i having interceptor faces substantially embraced by the rake structure 55 in a peculiar manner hereinaiter to be described. The auxiliary structure 2! has a sequence of interceptor or stopper blades 22 spaced at intervals which are substantially equal to those of the raking blades IS. The interceptor blades 22 have-brackets 23 whereby they In the following description and in the claims, parts will be identified by specific names are connected with a pair of beams or stringers f The auxiliary bladed structure H is arranged to operate substantially within the confines of the rake structure l5 in a" manner herein more clearly to be described.

There will now be described actuating mechanism whereby to effect the solids conveying reciprocating movement of the rake structure l5, as

well as actuating mechanism eiiecting up and down solids interceptingmovement of the auxiliary bladed structure 2!, and finallythere will be'describedmeans for driving and controlling both structures l5 and 2! in a desired functional coordination. v

The solids conveying cyclic movement of the raking structure i5 results from a horizontal and a vertical component movement given it by the actuating mechanism.

movement or up and down positioning movement is realized due to. swingable or supporting track members and upon which the upper and thelower The vertical component rakehangers respectively may operate by way of track rollers .27! and tic respectively. A track member 25 isfixed upon a rocker shaft 28 the-fulcrum portion of Whichiscperatively supported by wayof journals upon the sides of the classifier f Similarly a track member 25 has 33 fixed upon a rocker shaft-34 which has fixed. thereto a cam lever35 carrying a cam roller 35a normally engaging upon and controlled by a rotary cam member 35 having a relativel-yprotruding or outlying cam portion .3! and a relatively recessed or inlying cam portion 38. The cam member 36 -is fixed upon a main actuating shaft :39 journaled upon the classifier tank and havinga crank portion l-dfrorn which the horizontal component movement of the raking member is controlled, and which .is distinguishable from the vertical component-or up and down positioning movement of the raking member;

The horizontal component movement of the raking member is controlled by the crank por tion 45 through a connecting rod ii which piv-.

otally connected as at 2-2- with the rake member" i5 by way: of arm portions 43 fixed upon a transverse bar or rod 45 which rigidly interconnects the hanger portions 19 of the rakernember I 5.

The main actuating shaft 39 is herein shown,

to be driven by a set of gears' i5 and 55..

The auxiliary bladed structure or solids interceptor member 2| has its one end portion supported through a link 41 from abell crank 48 fulcrumedat 49 and having arms 50 and 50a.

correspondingly, the lower section of the auxiliary bladed member 2'! is'suspended through a v link Elfroma bell crank'lever 52 fulcrumed at 53 upon the classifier tank and consisting of arms 54 and-55.

A reach rod 56 interconnects the free endportions of arms 50;; and 55 of respective bell crank levers All .and 52. A link rod 51 connects the bell crank lever with a rock ing lever 58 fixed upon a rocking shaft 59 which in turn has fixed upon it a cam lever 60 carrying a cam roller 6| normally engaging upon the cam member 36. -The two cam portions 3'! and 38 are substantially complementary portions of the initial raking position. Raking blades are shown cam member 36. The active or peripheral cam faces of the cam portions 31 and 38 constitute an outlying arc portion of a relatively larger diameter 31a and an inlying arc portion of a relatively I smaller diameter 38a respectively, and there are transitional portions or steps or shoulders 31b and 38b respectively between-the active cam portions.

The'cyclic movement of the raking member l5 or what is known as the rake diagram is shown in Fig. 3 to be in the nature of a substantially triangular path 62 comprising a rectilinear branch 63 parallel to the bottom of the classifier tank and which corresponds to the solids raking stroke of the movement, an ascending branch 64 corresponding to the non-raking return stroke,

and a branch 65 which represents a direct or steep drop or perpendicular descent with respect to the tank bottom of the raking blades from their highest or final non-raking position to their in this diagram in various raking, as well as in non-raking positions.

The various operating positions of the mechanism controlling the raking movement are shown in Figs. 4,5, 6, and '7'.

Fig. 6 shows the highest non-raking position of the raking member l5, and which is kinematically defined by a position of the cam member 36 when the cam roller a. has reached the end of the protruding cam portion 31 and is about to drop down the step or shoulder 31b onto the face of the recessed cam portion 38. Accordingly, at this time through arm 33 and rods 32 and 30 the swingable tracks 25 and Nero held in their highest angular position, and the track rollers of the rake hangers I9 and 20 in turn are held in their highest position upon the tracks due to the then position of the crank and connecting rod 4| controlling the position of the rake member I 5 in a horizontal sense.

Subsequently the cam roller 35a drops onto the recessed 'cam'portion 38 which movement corresponds to the branch 65 of the raking diagram of Fig. 3. This causes the swingable track members 25, 26 to dropand thereby to establish 7 the beginning of the raking stroke a phase of which'is shown in Fig. '7. The lowered position of the rake member during the raking stroke is maintained as long as the cam roller 35a engages the rotating recessed cam portion 38 while concurrent rotation of the crank 40 through connecting rod 4| pulls the rake through its solids conveying stroke according to branch 63 of the rake diagram (Fig. 3).

Towards the end of this raking stroke the rotation of the'cam member will compel the cam roller 35a to mount up the cam shoulder 38b onto the protruding cam portion 31 thus causing the. tracks: 25, 26- to be swung upwardly as the track rollers 21 and 21a of the rake hangers reach the inner ends of their tracks proximate the pivotal or fulcrum point thereof. The tracks are held in their upper position by the protruding cam portion 31 during the further rotation of the cam member 36 and concurrently with such cam rotation the crank '43 through connecting rod will cause therake member IE to be moved towards the outer end of the then raised tracks 25, 26 which movement corresponds to the inclined ascending branch 64 of the raking diagram (Fig. 3).

The movement of the associated auxiliary bladed member 2| is a simple up and down movement and cam controlled through the cam roller 6|, and timed-to certain phases ofthe movement of the raking member I5, both movements being controlled by the identical cam member 36. As will be seen the cam. rollers 35a and GI are disposed at substantially diametrically opposedpoints of the cam member 36, so that they will alternately be engaged by the protruding cam portion 31 and the recessed cam portion 38 respectively. In other words, while the cam roller 35a--engages the protruding cam portion 31 the cam roller 6| will engage the recessed cam portion 38, and vice versa. Accordingly, the coordination and timing of the movements of the rake element and of the stopper blade element is such that at the end of a raking stroke the stopper blades 22 will descend in a sudden drop in front of and close to the raking blades IS; in other words, the stopper blades will descend when the raking blades have reached a point a in the raking diagram (Fig. 3), and they will thus intercept the loads held by the raking blades before the same rise away from the bottom and they will continue holding the loads to prevent their slippage until the raking blades have returned by way of point b in the raking diagram to the point e at which point each raking blade in turn will intercept a preceding load to permit the stopper blades to rise and in order to advance the load another step up the classifier slope to point a of the raking diagram.

With respect to' the up and down positioning movement of the longitudinally reciprocating rake structure IE, it will be understood that the path of this movement is substantially determined by the angular movement of the track members 25 and 26, which angular movements are herein shown to take place at the ends of the raking stroke. In other words, the track members are caused to swing upwardly when the track rollers 27 and 21a have reached the position proximate to the pivotal point of the tracks,

in which position the power required for'lifting the rake is a minimum, due to the shortness of the leverage of the tracks at that point. In this extreme upper angular position the tracks are held, due to the engagement of the. cam. roller the phase of the elevated return stroke no rake holding power is required from the drive mechanism. That is to say, as the track rollers then move towards the outer ends of the tracks in performing their elevated return movement, the

weight of the rake structure is intercepted as 35aup the arcuate cam face 39 so that during termined by a guide member 61 fixed upon the tank wall, and upon which guide member oper-' ates a guide roller 68 mounted on the stopper blade member 2|.

. In order to avoid injury or breakage in the machine from overstressing, it may be due for instance to jamming of the raking structure on account of congestion of solids'in the tank or of solids 'or the like getting caught between the raking and the stopper blades, or for any other reason, there is provided in this improved rake actuating mechanism a give or resiliency, and

which is herein shown to be realized in the special construction or a resiliently, contractable drive or connecting rod 4,! (seedetailed Fig. 9). Accordingly, this connecting rod M is of a telescoping nature and it has a fixed and limited maximum length of expansion during the raking stroke, but will resiliently foreshorten under compression. Accordingly, the example construction shown in the detailedFig. 9 comprises a cylindrical portion 69 and a plunger portion 18, both limited relative to each other with respect to the length of expansion by way of a block H and a plunger head '12. A closure piece I3 is slidable in the open-ended portion of the cylindrical portion 69, and it is adjustably fixed with respect to the plunger rod It by way of lock nuts ML Compression spring'lfi occupies the angular space between the plunger rod and the surrounding cylindrical portion and it is endwise confined between the block H and the sliding closure portion It. The head of the connecting rod is indicated'by the numeral 16, and it is the one that operatively connects with the crank 46] of the cam drive shaft 39, whereas the opposite end portion is indicated by the numeral 1'! and it is the one that attaches to the arms 43 that are fixed with respect to the rake hangers l9.

It will be seen that in order to obtainv the desired coaction of the two bladed members and their efficient cooperation, to wit of the raking member !5 and of the interceptor bladed memi 5 associated with it. It depends upon factors of operation and structure, for instance upon the degree of slope of the tank bottom, how many stopper blades should preferably be provided and in what locality. However, a particularly effective point for the location of a stopper blade is in the zone of emergence of the solids on the deck, because of the tendency of the backwash oi the liquid in this zone to drag solids about to emerge back into the bath.

I claim: I

1.. A classifying apparatus having a tank for holding a liquid-solids bath from which settle solids that are adapted to be removed upwardly along the sloping bottom of the tank, and having a rake structure movable in a cyclic operating path in a manner to effect the stepwise movement of said solids, and having rake reciprocating means for imparting longitudinally reciprocating movement to the rake structure, and having track means for the rake structure which track means are positionable to enable said rake structure to perform an upward forward solids raking stroke an elevated non-raking return stroke within its raking cycle; and furthermore having track positioning means operatively associated with said rake reciprocating means; characterized by the fact that the track means are provided upon and by a swingable arm having an axis stationary relative to the tank and controlled by said track track-means is. swung into its uppermostv angular position when the rake-structure is in the region proximate its most forward position. .7

3. Apparatus according to claim 1 wherein the operative arrangement of the track-positioning means with respectto the rake-actuating means: is such that the track-means is swung into the uppermost angular position when the rake-structure is in the region proximate its most forward position and when the track-engaging means of the rake-structure is in the position proximate the pivotal point of the track-means, and wherein the constructionof the track-positioning means is such that the track-means is held in the uppermost angular position during substantialiy the entire return stroke of the rake-structure and in the lowermost angular position during substantially the entire forwardraking stroke of the rake-structure and in a manner whereby the track-means thenparallels the inclined deck.

4:. Apparatus according to claim '1, in which the swingable track-means comprises, a swingable track member for lending support'to one section of the rake-structure and a similar track member for lending support to another section of the rake-structure longitudinally-spaced from the former section.

5. Apparatusaccording to claim 1, in which the swingable track-means comprises one pair of transversely spaced swingable track members for lending support to one section of the rakestructure. v

6. Apparatus according to claim 1, in. which the swingable track-means comprises a bellcrank-like member one arm of which provides a swingable track; 1 in which the track-positioning means comp-rises a link engaging the other arm of said bell-crank-like member; and in which said link is reciprocate'd through the action of a rotary cam member designed to efiect a relatively sudden rise and a relatively sudden drop of the track member at the respective ends of the raking stroke.

7. Apparatus according to claim 1, in which. the swingable track-means comprises longitudinally, spaced bell-crank-like members, each of which has an arm providing a swingabletrack and an arm serving as a swingable track-poshtioning arm and in which the track-positioning means comprises linkage connecting the free ends of said swingable track-positioning arms.

8. An apparatus according to claim lin which journals are provided stationary with respect to said inclined deck whereupon said swingable arms are pivotally supported so that the pivotal axis,

(lit

the rake-structure longitudinally back and forth along said swingable track-arms; and in which the track-positioning means are operated from said shaft functioning in timed relationship with respect to the rake-reciprocating means to swing saidarms and the tracks provided thereby, successivelyto the lower angular position in which the rake-structure derives support proper for the forward longitudinal raking stroke upwardly along said inclined deck, and into an upper angular position in which the rake-structure derives support for the elevated return stroke thereof 9. A classifier comprising a tank for receiving 1 and holding liquid and solids material to be side walls and a deep end wall extending upwardly from the sloping bottom, and an overflow weir provided in the region of the deep end thereof that determines the 'normaloperative level of the liquid within the tank; a drive shaft carried by journal means fixed in relation to the tank and provided with a main crank and witha 'cam means both of which are -movable with the shaft; a rake-structure having longitudinally spaced. transverselyextending blades and provided with track-engaging members through the medium'of which the rake-structure is reciprocally supported upon and carriedby tracks provided on the swingabletrack arms hereinafter referred to; lever constructions. of whichthe fulcrum portions derive support from journal members, normally fixed as to position with respect to the tank having swingable track arms providing the tracks upon which said track-engaging members rest and along which said track-engaging members .have forward and return reciprocatory movements and having link-actuated swingable track-positioning arms serving as the medium through which the swingable tracks are angularly positioned which said lever constructions are disposed at elevations such that the tracks are at all times essentially above the normal level of the liquid within said tank; a main connecting rod connected to and actuated by the main crank and having a pivoted driving connection with the rake-structure provided for successively imparting forward and return longitudinal reciprocating movements to the rakestructure incident to the operating of the drive shaft; and a track-positioning linkage actuated from said cam-means and having pivotal connections to the-free ends of the aforesaid linkactuated arms; said cam means being, constructed and arranged with respect to the main cran'k'so that as the apparatus functions said camemeans and the linkage actuated therefrom will through the medium of said link-actuated arms cause the swinging of the tracks from the lower angular positions therefor at a time when the trackengaging members of the rake-structure are near the pivotal axes for the track arms and will later cause a downwardswinging of the tracks to substantially the lowermost angular positions therefor and more particularly by the time the forward raking movement is about to take place.

10. A classifier as defined in and by claim 9, in which the lever constructions are longitudinally spaced and provide constantly parallel swingable tracks, and in' which the longitudinally spaced lever constructions include swingable track-positioning arms the free ends of which are connected by a, longitudinally extending link.

11. Classifying apparatus having an inclined deck; a reciprocable rake-structure having longitudinally spaced transversely extending raking blades movable in cyclic paths to effect longitudinal step by step movements of raked material upwardly and forwardly along'said inclined deck; a. stopper construction having longitudinally spaced transversely extending blades for intercepting material therebetween and common means for actuating in timed relationship said rake-structure and said stopper construction by imparting to the rake-structure forward longitudinal rakingstrokes and elevated non-raking rearward strokes and by imparting to the stopper construction downward movement when the rake-structure is in the region of the end of its forward stroke and'upward movement when the horizontally and' carrying a crank rake-structure-is in position to start a succeed- :ing forward raking stroke, guide means opera- Itively disposed between the inclined deck on the one hand and the stopper construction on the other hand'for guiding said stopper construction during the upward and downward movements thereof, said guide means being constructed so as' to support thestopper construction against movement in a rearward longitudinal direction but so as to permit yielding ofthe stopper construction in a forward longitudinal direction; said common means for actuating the rake-structure and the stopper construction embodyinga transversely extending shaft rotatably mounted in journals :fixed inrespect to the inclined deck; and a connecting rod comprising telescoping sections having compression spring means disposed between them for normally holding the telescoping sections in extended position effective to permit under abnormal conditions foreshortening of the connecting rod upon the rake-structure encountering an abnormal resistance during'a non-raking rearward stroke thereof with the one telescoping section being actuated from the free end of the crank while the other section is pivotally connected to a portion of the rake structure.

12. Classifying apparatus, comprising a tank having an inclined bottom normally'partially submerged, a raking blade structure having a series of raking bladessubstantially parallel to one another, means for moving said structure in, a substantially longitudinal closed path whereby the blades thereof convey burdens of settled solids stepwise upwardly to emergence along the inclined bottom on the forward stroke, but are out of burden conveying relationship on. the rearward stroke, means providing interceptor blade elements movable toward and away from the inclined bottom, and means for controlling such transverse movement of the interceptor. blade elements in timed relationship with respect to the operation of said raking blades, so as to intercept blade burdens substantially at the end ally functionally coordinated to and disposed and operative within a space defined by a pair of successive raking blades, said interceptor blade'element thus being individually confined between one raking blade forwardly and one raking blade rearwardly thereof.

13. Apparatus according to claim 12, in which said pair of successive rakingvblades has nonintersecting paths of travel.

14. Apparatus according to claim 12, in which said pair of successive raking blades has paths of travel which do not intersect and which are not intersected by the transverse paths of movement of the interceptor blade elements.

15. Apparatus according to claim'l2, in which the successive raking blades of said pair are spaced from one another a distance which is in excess of the raking stroke, the excess being substantially at least an amount corresponding to the aggregate thicknesses of a raking blade and of an interceptor blade element.

16. Apparatus according to claim 12, in which the interceptor blade elements are assembled and combined in a unitary bodily movable structure.

17.- Apparatusv according to claim 12, in which the interceptor blade elements reciprocate substantially in planes at right angles to the bottom and in'which the raking blades during the final phase of their downward movement have abrupt descent also in planes at right angles to the bottom.

' movement substantially at a time when the rake structure is in a position to start a succeeding forward raking stroke.

l9.'Apparatus according to claim 12, in which the interceptor blade elements are assembled in a unitary bodily movable structure, with the addition of guide means operatively disposed between the inclined bottomflon the one hand and said interceptor" blade structure on the other hand for guiding saidstructureduring'the up- Ward'anddownward movements thereof.

'20. .Apparatus according to claim 12, in which a series of'interceptor blade elements are combined in a unitary construction operatively mounted with respectto the tank in a manner toapermit a forward yielding movement thereof;

with the: addition of guiding means comprisinga inclined bottomland disposed so asto support the interceptor blade construction against movement in a rearward longitudinal direction; but so as pathdefining guide member fixed relative to the to permityieldingof'th'e construction ina forward longitudinaldirection;

I v CHARLES H. SCOTT.

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