US3278022A

US3278022A - Concrete mix declassifier apparatus and method

Info

Publication number: US3278022A
Authority: US
Inventors: John A Moeschler
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-01-08
Filing date: 1962-01-08
Publication date: 1966-10-11
Anticipated expiration: 1983-10-11

Description

Oct. 11, 1966 J. A. MOESCHLER 3,278,022

CONCRETE MIX DECLASSIFIER APPARATUS AND METHOD Filed Jan. 8, 1962 5 Sheets-Sheet 1 @EZAV INVENTOR. /-'/54 Ja /v A, MOESCA/LEQ 2 p76. @A/Ey J. A. MOESCHLER 3,278,022

Oct. 11, 1966 CONCRETE MIX DECLASSIFIER APPARATUS AND'METHOD 0d. 11, 1966 J. A. MOESCHLER 3,278,022

CONCRETE MIX DECLASSIFIER APPARATUS AND METHOD Filed Jan. 8, 1962 5 Sheets-Sheet 5 IIIII Oct. 11, 1966 J. A. MOESCHLER 3,278,022

CONCRETE MIX DEGLASSIFIER APPARATUS AND METHOD 5 Sheets-Sheet 4 Filed Jan. 8, 1962 H qmimw INVENTOR.

Ja /V A. Mafsm/z 58 Q ,/7 ./VEV

Oct. 11, 1966 J. A. MOESCHLER 3,278,022

CONCRETE MIX DECLASSIFIER APPARATUS AND METHOD Filed Jan. 8, 1962 \ix 9 /56 /s'e 5 Sheets-Sheet 5 .SZUQQV EMPTY INVENTOR. Ja /v A. M05504 5e 76 A; BY

I I {i 3,278,022 CONCRETE MEX DECLASSIFIER APPARATUS AND METHOD John A. Moeschler, 2995 Sepulveda, Los Angeles, Calif. Filed Jan. 8, 1962, Ser. No. 164,847 36 Claims. (Cl. 209-2) This invention relates to declassification of fluent mixtures and more particularly to unique apparatus and method for treating concrete mix for the purpose of separating the principal constituents incident to salvaging the sand and aggregate and collecting the cement constituent as slurry for subsequent withdrawal and disposal in any suitable manner.

During recent years there has been a rapidly expanding market for prepared concrete mix blended to desired specifications at a central mixing plant and mixed while being transported in transit mixers to the place of use of the mix. Such transit mixers utilize rotary drums mounted on heavy duty trucks. Mixing is completed prior to arrival at the place of use, the drum being maintained in operation until arrival at which time the drum is operated to discharge its contents into forms. Not infrequently it occurs that, upon arrival, the mix cannot be delivered for various reasons. If that particular mix cannot be re-dispatched to another user promptly, the operator must dispose of his load to safeguard the transit mixer from damage and to avoid scraping the mix which soon deteriorates below permissable specification values.

Disposal of the mix and cleansing of the transit mixer under such circumstances as mentioned above, as Well as flushing the mixer after use, has created very serious and vexatious problems, to leave unmentioned the economic loss involved in handling and discarding large volumes of unusable mix. Additionally, dump sits cap able of receiving the large volumes of ever accumulating waste mix are becoming increasingly difiicult to find and are located increasing distances from the operating bases of transit mixers.

Previous attempts have been made to solve these problems by the use of water to wash away the cement constituent of the mix with a view of salvaging the sand and aggregate. However, such proposals merely aggravate the problem because of the large quantites of water required and because public officials object strenuously to attempts to dispose of the cement-carrying water through sewers, drainage ditches, streams, etc. For example, it attempts are made to dispose of such water by seepage into wasteland, the wasteland soon becomes clogged with setting cement. It is not feasible to drain the water into pipe lines, sewer systems or the like dumpways because the cement gravitates out and obstructs the drainage passageways.

The foregoing and other serious problems attending the operation of transit mix facilities are resolved in a simple, highly efiicacious and satisfactory manner by the present invention utilizing concrete mix declassification apparatus of a fully self-contained nature utilizing water in a closed circuit and lacking need for drainage facilities of any character. Essentially the method of declassifying and salvaging reusable constituents of the mix involves treating the mix in excess water in a manner causing the fines to go into suspension as the cleasned sand and aggregate undergo processing to separate them for discharge into independent storage receivers while the water ladened with fines is skimmed off and conveyed into settling tanks where the cement gravitates and collects as slurry permitting the clean water to be skimmed away for reuse in the washing mix. The clean water returns through and overflows from an auxiliary storage tank so that United States Patent adequate clean water remains available at all times to flush the transit mixer equipment without in any way interfering with water levels in either the declassifier and particularly in the cement-settling tank.

Other important features of the method and apparatus include provision for storing excess water from the closed water circuit until it is again needed to maintain optimum level conditions in the closed circuit. This makes it possible to operate with uniform and desirable water operating levels in the declassifier and in the settling tanks respectively despite the presence of widely varying quantities of mix and slurry in the apparatus. It also permits long continued operation without need for ever wasting Water to drainage facilities. Desirably, the excess storage tank is nested about the lower portion of the settling tank thereby making more efficient use of the site and simplifying the structural features of the apparatus. This arrangement also simplifies the transfer of fluids between the tanks as well as maintaining the desired opera-ting levels within the declassifier and the settling tank facilities.

Still greater flexibility is to be enjoyed by adding one or more extra settling tanks each of which may or may not include additional excess water storage tanks. If

the latter are not present, suitable provision may be made for draining excess water into a common storage tank. In either event the installation desirably includes suitable pump means for transferring water together with slurry from the bottom of the storage tank back into the recirculating cement-carrying water circuit, and preferably, directly into the settling tank. The means for transferring Water between the two tanks includes adjustable skimmer means by which clean water present in the settling tank may be transferred into the storage tank to facilitate withdrawal of cement slurry collected in the bottom of the settling tank.

The apparatus includes provision for removing collected slurry periodically, as once every twenty-four hours, for removal to a disposal dump or elsewhere. The means here provided for this purpose includes one or more suction conduits having inlets located at the bottom of the settling tank and discharging into suitable transport means, such as a tank truck.

The declassifier proper utilizes a rotating trommel into one end of which mix is to be declassified is discharged. The mix is agitated or tumbled within the trommel in excess quantities of a suspension liquid, as water, as the sand and fine particles pass through small openings in the trommel wall. The larger particles and aggregate remain inside the trommel and are lifted by special devices at the trommel outlet for discharge above the water level to a place of aggregate storage. The sand and the like fines are advanced by the trommel to a point of flow into a hoisting conveyor discharging into a storage chamber for sand separate from that for the aggregate. The classifier also includes skimmer means for removing cement suspended in water for delivery to the settling tank.

As herein shown, a common prime mover is connected through suitable drive facilities to drive both the trommel, the water circulating pump and the separate conveyors for sand and aggregate, thereby avoiding the need for separate drive motors, controls and synchronizers.

Other important features of the invention include means for draining excess water from the sand and aggregate storage bins as well as from the entire site surrounding the apparatus into a sump. The latter is provided with automatic suction pump means operable to remove water and cement slurry for delivery back into the settling tank Whenever the level rises to a selected high point.

The control equipment for the apparatus includes a master control arranged to be activated by a transit mixer as it moves into and out of position to discharge mix into the classifier. In other words, the movement of the truck into dumping position automatically energizes the system to start the water-circulating pump as well as the trommel and conveyors thereby conditioning the apparatus to receive mix prior to the actual discharge of the latter into the apparatus. Manual control means readily accessible to the truck operator at the discharge end of the mixer drum enables the operator to direct flushing water from the auxiliary water tank into the mixer drum from a position in which he can easily observe flushing operations going on within the drum. After the drum has been operated to discharge its contents into the declassifier additional flush Water may be used if desired for further and thorough cleansing of the drum.

To assure complete processing of each load of mix, there is provided timer controlled relay mechanism forming part of the control circuit and operating to maintain the apparatus in operation for a predetermined period fully adequate to treat the contents of a single transit mixer thereby avoiding the possibility of cement settling out in trommel housing or the conduits of the closed water circuit. Once this period has elapsed the clock automatically discontinues operation of the apparatus until the control circuit is manually re-energized or automatically re-energized by the arrival of the next mixer. Other time delay mechanism functions following shut-off of the apparatus proper to transfer settlings from the holding tank to the main settling tank thereby to maintain the entire apparatus, except the settling tank, free of cement.

Accordingly it is a primary object of the present invention to provide novel apparatus and methods of treating a fluent mixture containing buoyant and nonbuoyant constituents, as for example concrete mix and the like, and effective to separate the mixture into its constituents utilizing a liquid vehicle as water in a closed circuit to suspend and convey the lighter constitutents into settling chamber means.

Another object of the invention is the provision of apparatus for treating concrete mix to salvage the sand and aggregate while cleansing away the cement and collecting the latter separately as slurry.

Another object of the invention is the provision of an automatically operating process and apparatus for treating concrete mix ex editiously a it discharges from transit mixers and collecting the cement constituent as slurry for subsequent withdrawal and removal to a place of disposal.

Another object of the invention is the provision of an apparatus for declassifying concrete mix and delivering the sand and aggregate as separate clean constituents while removing the cement from the presence of sand and aggregate while suspended in cleansing water.

Another object of the invention is the provision of compact, rugged apparatus for declassifying concrete mix while being agitated within an excess quantity of water maintained captive in a closed circuit and including provision for separating collected cement by Stratification from the recirculating water.

Another object of the invention is the provision of means for flooding flushing water in a closed circuit in intimate contact with concrete mix to float away the cement constituent for subsequent collection as slurry in settling tank means forming part of the closed circuit.

Another object of the invention is the provision of automatic apparatus for declassifying concrete mix without need for an operating attendant and arranged to be activated automatically as a transit mixer arrives at the apparatus and continuing in operation for a sufficient period after the mixer pulls away to assure processing of the mix, the apparatus remaining inactive but in instant readiness to resume operation upon the arrival of the next transit truck in need of servicing.

Another object of the invention is the provision of self-contained apparatus for declassifying concrete mix utilizing a captive supply of water and requiring no overflow connections to drainage or sewer facilities.

Another object of the invention is the provision of a concrete mix declassifier utilizing a single moving part to process the mix and to feed the separated constituents into separate discharge facilities for conveying each sepparated constituent away from the declassifier.

Another object is the provision of a mix declassifier having a collection sump for drainage of the entire site area for a cement mix declassifier selectively operable by either manual or automatic means to receive all drainage from the site area and to transfer this drainage, including settlings, into a settling tank where solids collect by Stratification leaving clean water.

Another object is the provision of a cement mix declassifier arranged to be energized and de-energized as required to separate out cement and featuring time controlled means for operating the apparatus for a predetermined period following the end of a normal operating shift for the purpose of collecting all posslble particles of cement from the entire apparatus into the cement settling tank.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawlugs to which they relate.

Referring now to the drawings in which a preferred embodiment of the invention is illustrated.

FIGURE 1 is a top plan view of the apparatus of this invention and including a schematic representation of the control circuit therefor;

FIGURE 2 is a fragmentary vertical section view on an enlarged scale taken along broken line 2-2 on FIG- URE l and showing typical water levels during normal declassifying operation;

FIGURE 3 is a transverse horizontal sectional view centrally of the declassifier on an enlarged scale;

FIGURE 4 is a fragmentary side elevational view of the declassifier on an enlarged scale with parts broken away, the view being taken from the left hand side of the declassifier as it appears in FIGURE 2;

FIGURE 5 is an elevational view of the discharge end of the declassifier with parts broken away;

FIGURE 6 is a transverse vertical sectional view on a smaller scale and taken along line 6-6 on FIGURE FIGURE 7 is a fragmentary vertical sectional view on a reduced scale taken through the discharge end of the declassifier and along line 7-7 on FIGURE 3;

FIGURE 8 is a fragmentary cross-sectional view on an enlarged scale taken along line 8-8 on FIGURE 3 and showing details of the declassifier water skimmer;

FIGURE 9 is a fragmentary horizontal sectional view on a reduced scale taken along line 99 on FIGURE 3;

FIGURE 10 is a fragmentary vertical sectional view on an enlarged scale taken through the bottom of the stand elevator; and

FIGURES ll, 12 and 13 are schematic representations of the settling tank facilities showing the direction of flow and the levels in various parts of these tanks during typical different operating conditions,

The apparatus generally Referring more particularly to FIGURES 1 and 2, there is shown somewhat schematically one preferred embodiment of a concrete mix declassifying facility embodying this invention and designated generally 10. This facility comprises the declassifier proper 11, a pair of

clarifier tanks

12, 13, an auxiliary water tank 14, a sand storage bin 15, an aggregate storage bin 16, a drainage sump 17 and a truck-operated main control switch 18. As best appears from FIGURE 1, control switch 18 is arranged to be closed by contact with the rear wheels 19 of a transit mixer 20 as this mixer backs into dumping position with respect to the mix receiving hopper 22 of declassifier 11. The closing of switch 18 in this manner is effective on control relays of the electrical jecting downwardly from the underside of manifold 87 is a suction hood 90 having a horizontally disposed screened inlet 91 along its underside and best shown in FIGURES 6 and 8. Also, as here shown, manifold 87 is provided with a series of inlet orifices 92 through which the cement-laden water is sucked by pump 85. Water carrying cement in suspension flows into collection trough 89 through slots 93 (FIGURE 6) opening through the side wall of housing 25 close to but below the normal water level in the declassifier. The cement and water mixture issuing from the discharge side of pump 85 is carried to

clarifiers

12, 13 in a manner which will be described presently.

T he clarifying system.

The clarifying system for separating cement from the water will now be described by the aid of FIGURES 2 and 11 to 13. The clarifier there shown comprises a pair of clarifier or settling tanks 100, 100' having conical bottoms. One clarifier is nested centrally within a holding or excess water tank 101 supported on legs 11 2. The holding tank also preferably has a conical bottom to facilitate removal of cement slurry collecting on its bottom. As here shown by way of illustration, clarifier 1% and holding tank 101 each have a capacity of 1500 gallons of water although it will be understood that this size is merely typical of a wide range of suitable sizes.

Extending vertically through each of the similar clarifiers is a suction pipe 103 closed at its top and having an expanded lower end provided with inlet openings 104. Desirably, tube 103 is Welded to the bottom of the tank and its upper end is rigidly connected through radial braces 105 with the rim of the tank. In consequence, the bail 106 provided at the top of pipe 103 provides a convenient means of attaching the hook of a lifting crane to the clarifier tank While assemblying or servicing the equipment.

Surrounding and welded to the top of conduit 103 is an overflow and a dirty water distributing cup 108 having a horizontal rim spaced slightly above the operating water level within the clarifier. Cement-laden water delivered into cup 108 overflows into the tank and is held confined within a large diameter annular skirt 109 secured to arms 105 extending downwardly into the water sufficiently to assure settling and Stratification of the cement content.

Clean Water is skimmed from the surface of the water in the clarifier by means of an annular skimmer trough 111 secured to the inner rim edge of clarifier 100 and having a horizontal disposed inner edge over which a thin film of water overflows for removal from the clarifier. The withdrawn water passes through conduit 112 into a clean water storage tank 14 having a capacity adequate to supply flushing water needed to thin mix being discharged from a transit truck as well as water to flush interior surfaces of the drum. Eighty gallons is found quite sufficient for these purposes although it will be understood a larger tank may be provided if desired.

From the foregoing it will be understood that clean water flowing into tank 14 is trapped there until the quan tity required for flushing is present. Any additional clean water overflows the lips of a skimmer 115 associated with reservoir 14 and passes through conduit 116 into a clean water return trough 118. This open-top trough is best shown in FIGURE 3, and normally conveys the clean water back into the inlet end of trommel 30 via the mix receiving hopper 22. As appears best from FIG- URE 4, hopper 22 has a perforated inner lining 120 for guiding the mix into trommel 30 through openings 45 in the declassifier end wall. The narrow space between hopper 22 and perforated wall 120 enables sand passing through the perforations to be by-passed around the trommel. Sand gravitating through plate 120 is guided through an opening 121 in the lower portion of end wall 42 and passes directly into the sand conveying portion of the declassifier for advance by helical pusher 53 directly to the sand elevator 63.

Referring back to FIGURE 2, it is pointed out that the inlet or the right-hand end of the clean water return trough 118 projects into holding tank 101 and has a low-height overflow lip 123. All overflow from this lip takes place into the holding tank and occurs only under certain conditions. Normally there is no ovenflow from lip 123 and all clean water entering trough 118 from skimmer pipe 116 returns to the inlet end of the trommel. At other times, and particularly when the recirculating pump is not operating, clean water entering trough 11115 from pipe 116 overflows lip 123 of trough 113 into holding tank 101. The circumstances under which this occurs will be explained in greater detail presently.

The clean water stored in tank 14 is always available to flush a mixer drum. For this purpose, the clean Water is withdrawn from tank 14 and passes through conduit 125 into a pump 126 (FIGURE 2). This pump is located adjacent the truck flushing station and is driven by a motor controlled by a manually operated starter mechanism 162 arranged for use by the truck operator while standing on the rear platform of the transit mixer 20 (FIGURE 1). The end of water conduit 125 is provided with a hose 127 for convenience in directing the clean water against the interior of the mixer drum. If the truck driver should wish to use clean water from the city water mains, he can do so by opening valve 128 (FIG- URE 2) and allow the city water to flow through hose 129 into the mixer. Normally, however, no city water is used but only the clean water derived from storage tank 14.

Holding tank 101 has a withdrawal pipe 132 having a suction inlet end opening int-o the bottom of the tank 101 and having its upper end connected to the suction inlet of transfer pump 163. The outlet of this pump discharges through a check valve 134 into a conduit 135 having branches discharging into the distributing cups 100 or 108' of the two clarifier tanks. 'Desirably, branches 1.35 are provided with

valves

136, 136 which can be adjusted as desired to pass water and slurry to either clarifier tank at the option of the operator.

Return pipe 135 is also employed to return water and fines from sump reservoir 17. To this end, a suction pipe 137 extends to the bottom of sump 17 and has its upper end connected with the inlet of sump pump 13 8. The discharge of this pump opens into distributing branches 135 through a check valve 139. Preferably, the motor driving the sump pump is subject to both manual control and to a conventional automatic level control which will be described later. Suffice it to say at this point that sump 17 receives drainings through drain pipe 140 extending from each of the

bins

15 and 16 as well as from the area generally around the described declassifier equipment. Accordingly, much of the contents of the sump includes both fine sand and cement which enters the sump along with drainage water. The sump pump is effective to transfer these by suction into conduit 135 and to deliver them into the dirty

water distributing cups

108, 108 in order that the solids may gravitate to the bottom of the clarifier tank permitting the residue clean water to return to the system for reuse.

A further and important feature of the clarifier is the provision of a vertically adjustable skimmer having its tubular shank adjustably supported through an O-ring seal in a socket 146 extending through the lower side wall of clarifier tank 100 and discharging into holding tank 101. Normally, the upper rim edge of skimmer 145 is positioned above the level of water in tank 100, the skimmer being held in this position by the O-rings or a suitable clamping device, not shown. Should it be desirable to withdraw clean water from clarifier 100, this is accomplished by adjusting skimmer 145 downwardly and reclamping it at the appropriate position. All water above the lips of skimmer 145 then overflows and passes through the shank of the skimmer into holding tank 101, as is desirable when removing collected slurry from the claricircuitry to initiate operation of the apparatus as will be described in greater detail below in connection with the mode of operation.

The declassifier Referring now more particularly to FIGURES 3 to 6, a description will be given of declassifier 11. The declassifier proper comprises a generally cylindrical outer housing having its axis extending generally horizontally and rigidly supported, as by legs 26. The upper half of housing 25 comprises a semicylindrical cover 27 hinged at 28 (FIGURE 2) to one edge of the lower half. Normally, cover 27 is closed but, when opened, full access is had to a cylindrical trommel 30 having its longitudinal center coaxial with that of housing 25.

Trommel 3% is provided with a multiplicity of openings 31 large enough to readily pass sand but restraining gravel and aggregate commonly present in concrete mix. The trommel includes a tubular shaft 33 supporting shaft stubs 34 at either end thereof and held assembled to main shaft 33 as by bolts 35. The outer ends of shafts 37 are journaled in cup-shaped bearing housings 37 provided about their rims with a flange useful in securing the bearing housing to end walls of housing 25, as by cap screws Bearing housing 34 at the inlet end of the trommel is preferably enclosed by a cover 39. A thick-walled rubber sealing diaphragm 40 is provided with a central opening smaller than shafts 34. to provide a sharp-edged sealing lip bearing against the shaft and effective to prevent water seepage into the bearing proper as well as the escape of grease from the bearing housing.

The manner of supporting the trommel bearings removably on each semicircular end wall 42, 4-2 of housing 25 is best shown in FIGURES 3, 4 and 9. Each end Wall has an elongated notch 43 opening downwardly centrally of its upper edge. These notches are normally tightly closed by

removable closure plates

44, 45 located at the inlet and outlet ends, respectively, of housing 25. Closure plate 44- has large area cut-outs 46 (FIGURE 4) opening from hopper 22 into the inlet end of trommel 30, plate 44 being held detachably assembled to the end wall by cap screws 47. Cover plate 45 at the outlet end as here shown is provided with a mounting flange 49 having holes through which mounting cap screws 47 extend.

Referring again to FIGURE 3, it is pointed out that tubular shaft 33 is equipped with spokes 50 having their outer ends welded to a helical pusher 51 having its outer peripheral edge welded or suitably secured to the inner surface of the trommel. The ribbonlike helical pusher St is effective to advance the contents of the trommel progressively from its inlet to its outlet ends. Surrounding trommel 30 is a second helical pusher 53 held rigidly concentric with the trommel by spokes 54 securely welded to the exterior of the trommel at points preferably opposite inner spokes 50. Both pushers spiral in the same direction, the inner one being effective to advance mixed constituents along the interior of the trommel and the outer pusher 53 being effective to advance sand and the like passing through perforations 31 toward the outlet end of outer housing 25.

From the foregoing it will be recognized that the principal rotating component of the apparatus comprises trommel 30 which is so designed and supported that it can be assembled and disassembled from housing 25 expeditiously. For example, it is merely necessary to open cover 27 about hinge 2.8 and remove cap screws 47 holding

closure plates

44, 45 in place. This having been done, the trommel can be lifted bodily vertically from housing 25 for either servicing or replacement.

The simple structure provided for effectively sealing the opposite ends of the trommel are best shown in FIG- URE 3 and include suitable rings of bearing material 55 secured to the opposite flanged ends of the trommel, as by cap screws 57. The remote exposed faces of these rings are closely spaced to similar rings 58 secured to end walls 42 by screws 57. The spacing between the abutting faces of rings 56, 58 is considerably exaggerated in the drawing. If desired an apron strip of rubber suitably fixed to stationary ring 58 and bridging the inner edges of the pairs of sealing rings can be used to keep grit from entering between their interfaces.

Referring to FIGURES 3 to 6, it will be understood that the discharge end of trommel 30 is provided with elevator means for lifting the larger elements of aggregate through a discharge opening 48 into the inlet end of a gravity chute 52. Chute 52 is inclined downwardly and discharges onto a belt conveyor 55 discharging the aggregate into storage bin 16 and supported on legs 59. Of importance is the fact discharge opening 48 is located somewhat higher than the water level normally prevailing in the declassifier.

To elevate the aggregate and to discharge it through opening 48 into the chute there is provided a plurality of lifting blades 60 having their foremost edges rigidly secured to supporting arms 61. Arms 61 project generally tangentially from a supporting hub 62 carried by shaft 33 and their outer ends are preferably bolted or otherwise secured to the trommel shell. Preferably, the opposite radial ends of blades 60 are unobstructed in order that water may escape freely from the aggregate present on the blades as these are elevated above the water level in the trommel. To this end, the blades may be perforated. The inclination of the blades is such that as they come opposite outlet opening 48 the contents gravitate readily into chute 52 and thence onto conveyor belt 55 for trans port into storage bin 16.

Sand and fine material settling through openings 31 in the trommel are gradually advanced through the discharge end of the apparatus by helix 53 while being continually and repeatedly tumbled through the flushing water with which housing 25 is flooded. By the time the solids reach the end of the discharge housing they are thoroughly washed and free of cement. This clean sand is pushed into outlet opening 64 formed in the side wall of housing 25 and into the lower end of a screw conveyor 63 suitably supported in an inclined position. This conveyor is closed by a lower end cap 65 which includes a bearing block 66 (FIGURE 10) having a conical seat for the similarly shaped lower end 67 of the screw shaft the bearing so formed being lubricated by water.

The driving means for trommel 30, for each of the described conveyors and for the main water circulating pump will be best understood from FIGURES 3, 4 and 5, and comprises a three-phase electric motor 70. This motor is supported on a shelf 71 suitably secured to the end wall 42 of the main housing and is connected through suitable reduction gearing to a main drive sprocket 72 to drive a roller chain 73 meshing with sprocket teeth 74 integral with the outlet end of trommel 30.

The drive shaft for sprocket 72 also supports a sprocket 75 (FIGURE 4) over which is trained a drive chain 76. Chain 76 meshes with a sprocket 77 driving conveyor 63 through mitre gears, as well as with a sprocket 78 (FIG- URE 5) driving belt conveyor 55. It will be observed that chain 76 passes over an idler sprocket 79 to facilitate driving sprocket 78 in the appropriate direction to elevate the sand into storage bin 15.

Screw conveyor 63 is driven from its upper end by means of a shaft 80 supported along the exterior of this conveyor and connected by a chain belt 83 to a sprocket 82 (FIGURE 4) mounted on the upper end of the conveyor. Thus, it will be apparent from the foregoing that the major moving components of the apparatus are driven from a single main motor 70. Moreover, this same motor is used to drive the main water circulating pump 85 supported on shelf 71 and connected to motor 70 through a belt drive 86 (FIGURE 5).

The inlet of pump 85 includes an inlet manifold 87 disposed horizontally in a water trough 89 extending lengthwise along one side of declassifier housing 25. Proher. It will be noted that skimmer 145' for auxiliary clarifier 100 is similar in construction to the one just described but discharges into a conduit 148 discharging into the lower end of the single holding tank 1111. Likewise, the clean water skimmer 111 of the second clarifier passes through conduit 112' into the small storage tank 14 for. overflow and returns to the declassifier in the same manner as is the clean water derived from clarifier 100. The cement-laden water withdrawn from the declassifier by the main water circulating pump 85 is distributed to both receiving

cups

108 and 108 through a branched distributing conduit 149. No control valves are shown for these branches although such valves can be added thereby permitting either clarifier to be used to the exclusion of the other, a feature highly desirable to facilitate servicing or repair of the tanks.

Control system Referring now to FIGURE 1, the electrical control system for the described classifier will be described. Threephase power is supplied to the equipment through a normally closed master control switch 151 and a step-down transformer T providing 110 volt power to the various control components. All motors are operated from the three-phased 220 volt supply whereas all other components are operated from the hot bus 151 energized from the secondary of transformer T. It will therefore be recognized that all leads connected to bus 151 are energized at all times main switch 150 is closed.

Normally, the operation of the declassifier is controlled by the normally open master switch 18 having an actuating lever positioned to be engaged by rear wheel 19 of the transit truck 21) as it arrives at the proper dumping position with respect to receiving hopper 22 of the declassifier. As shown in FIGURE 1, the truck is approaching dumping position but has not actually arrived, and the parts are in the position occupied when the apparatus is not operating. Closure of switch 18 by the truck wheel supplies current to main relay 153, closing the armature of this relay downwardly. The closing of relay 153 supplies power to the stylus actuating solenoid 154 forming part of a continuously operating 24-hour recorder 155. In its open or de-energized position, relay 153 maintains a power supply through lead 156 to the solenoid of a conventional adjustable time delay relay 157 known to those skilled in the timer relay art as a normally-closed timer-opened relay of adjustable time delay capabilities. So long as the solenoid of this timer is energized, the solenoid energizes a clutch driven by a continuously energized synchronous motor and the latter is operable to open the right hand pair of contacts at the end of a preselected time period. Instantly that the clutch solenoid is de-energized, the right hand contacts revert to their normally closed position and remain there so long as the solenoid is de-energized and for a predetermined time after the solenoid is energized, whereupon the timer motor opens them and keeps them open until the solenoid is again de-energized. It is also pointed out that the two pairs of contacts of the relay are interlinked to operate together with one pair being closed when the other is open. Hence during a period of inactivity of the declassifier, all switches are in the position shown. Since control switch 18 is open, relay 153 remains closed upwardly to supply energy through lead 156 to the solenoid of timer 157. Under these conditions the timer motor acts to maintain the normally closed right hand pair of contacts open so that no power is supplied to the starting switch 170 for main motor 70. In this connection it will be understood that the control solenoid for starter 170 is normally grounded through a normally-closed reset button 171. The closing of the three-phase starter switch 170 will also be understood as closing a circuit through a fourth pair of contacts operating in known manner in a holding circuit energized by lead 159 to maintain the switch closed independently of timer 157 and until such 10 time as relay 153 is de-energized and effective to dis continue the supply of power to lead 159. When this occurs the holding coil for starter switch 170 is deenergized and the switch for motor opens.

The apparatus is thus seen to be placed in normal operation when switch 18 closes to close relay 153 downwardly with the result that motor 7 0 is operating to rotate trommel 31) as well as both sand conveyor 63 and aggregate conveyor 55. Main water circulating pump is also in operation to draw cement-laden water from the long trough 89 into hood 90 and conduit 88 and then conveyed through the pump and along conduits 149 to distributing cups 108 and 108' of the two clarifiers and 100'.

Meanwhile, the truck operator is standing at the rear of the truck and manipulates starter button 162 of the switch controlling the three-phase motor driving water pump 126. So long as this pump is operating, clean water can be withdrawn from the clean water supply reservoir 14 by way of ducts and delivered into the interior of the cement mixer drum through flexible hose 127. When the supply valve for the discharge side of this pump is closed, the water merely circulates within the pump. Normally, 50 to 60 gallons of water withdrawn from reservoir 14 suffices to wash down the interior of the drum and to thin out the mix appreciably. This mix is then discharged from the drum through the usual chute directly into declassifier receiving hopper 22. After the main contents of the drum have been discharged, additional water may be admitted to wash and cleanse the same thoroughly, the washings being discharged through the chute to hopper 22. The operator then punches control button 162 a second time to discontinue operation of pump 126.

At this time it is desirable to point out that even though 50, 60 or more gallons of water are withdrawn from reservoir 14, this does not affect the normal operating levels of the water in either the declassifier or clarifier tanks 1011, 100 for reasons which will be readily apparent from a consideration of FIGURE 2. So long as water is being withdrawn from tank 14 through conduit 12.5 the level in the tank will be below skimmer 115. Consequently, no water will be discharging through the skimmer into return trough 118. Owing to the relatively large size of the housing 11 compared to tank 14, the temporary cessation of return water flow will have substantially no effect on the level in the declassifier.

Referring more particularly to FIGURES 4 and 5, it is pointed out that the cement mix entering hopper 22 flows downwardly through openings 46 into the inlet end of the slowly rotating trommel 30. Some sand escapes through the perforated inner wall 121 of the hopper and falls through the water and through opening 121 in the front end wall of the main housing where it is picked up by the larger-diameter helical pusher 53 and advanced to the left as viewed in FIGURE 4 along with other sand toward the inlet 64 of sand conveyor 63. The main portion of the mix is advanced along the interior of the rotating trommel which lifts and tumbles the mix back upon itself as it is gradually advanced toward the discharge end by the smaller-diameter helical pusher 51. It is therefore evident that the mix is tumbled through the great excess of water filling the declassifier to the level generally indicated in FIGURE 4, or approximately at the level of the trommel axis. This repeated tumbling facilitates passage of the sand and smaller particles through the perforations in the trommel, as well as washing away the cement and like fines which, because of the described agitation, go into suspension in the water. This water continually overflows into trough 89 where it is picked up by water circulating pump 85 for transport into the distributing cups of the two clarifiers.

As the aggregate reaches the discharge end of the tromniel it is picked up by the inclined lifting paddles 60 which may be perforated to facilitate free drainage of water from the paddles as the aggregate is elevated above the water level for gravity discharge through chute 52 into aggregate conveyor 55.

From the foregoing it will be apparent that there is a continuous withdrawal of sand by conveyor 63, of aggregate via conveyor 55 and of water-suspended cement via pump 85 and distributing conduits 149. The sand is separated from the water as it is elevated toward the upper discharge end of conveyor 63 and falls substantially free of water into receiving pit 15. Similarly, aggregate, substantially free of water, discharges from the upper end of conveyor 55 into receiving bin 16 in the manner made clear by FIGURE 2. Any excess water drains from the bottom of these bins through conduit 140 into sump pit 17 along with any other water in the area surrounding the equipment.

Cement-laden water entering the clarifiers overflows from distributing

cups

108, 108 and is constrained to flow downwardly through the larger diameter skirts 109. While in this quiescent condition, the cement gravitates to the conical bottoms of the clarifiers, leaving the clean water to rise and overflow the inner lip of skimmers 111 for gravity return through ducts 112 into storage tank 14. If no water is being withdrawn from this tank, the level is controlled by skimmer 115, the water overflowing into the skimmer and thence into the underlying large diameter basin at the right-hand end of return trough 118. Normally, the clean water in trough 118 is below lip 123 with the result that the clean water flows back into the declassifier through the mix receiving hopper 22 (FIGURE 3).

Let it be assumed now that the first truck has dumped its contents into hopper 22 and that it has been driven away from the site to make room for a second truck when .it arrives. As the first truck leaves the dumping position, master switch 18 automatically opens thereby de-energizing the solenoid of relay 153. As this occurs the supply of current to the stylus actuating solenoid 154 is broken allowing stylus 175 to move to the left. So long as the truck was in unloading position, stylus 175 was held to the right thereby making a bump trace 176 on the recorder record sheet to indicate the time and duration of the trucks sojourn at the apparatus. This not only provides the main office with a written record of the operations but also serves to police the truck operators.

The de-energization of relay 153 also discontinues the holding current to the holding coil of main starter 170 and .re-energizes the solenoid clutch of time 157. The continuously running motor of this timer energized through lead 1% operates to open the contacts to the solenoid of starting switch 170 to stop motor 70 after a selected period of time, such as five minutes. In consequence, main switch 170 remains closed for this preselected time period notwithstanding the de-energization of relay 153. This action is important because it maintains the declassifier in operation for a sufficient period to assure the removal of cement-laden water from the declassifier and the delivery of substantially all cement into the clarifiers before main water circulating pump 85 stops. Likewise, sand and gravel present in the declassifier is advanced into the discharge conveyors. Accordingly, the apparatus may remain inactive for prolonged periods without risk of cement taking a set and jamming the apparatus or forming a gradually increasing deposit layer.

In the latter connection it is pointed out that the interior surfaces of the declassifier and of the water circulator and even the clarifiers gradually become coated with a thin but effective protective layer of strongly adherent cement. This layer is strongly resistant to abrasion by the solids being handled and protects the equipment against rust and wear of the parts in contact with the sand and aggregate.

Should the next truck to be serviced arrive before the elapse of the five minute period determined by timer 157, the engagement of its rear wheel with master switch 18 serves to reactivate the apparatus without adverse etfect on timer 157. In other words, the expiration of the five minute period merely conditions this timer to activate starter switch immediately that the time solenoid is de-energized, its right hand pair of contacts then returning instantly to their normally closed position. The apparatus is placed in operation again to declassify the second load of mix in the same manner described above. Other trucks are serviced successively in the same manner. Quite frequently there is a protracted delay be tween truck flushing operations. In such cases, the described circuit operates automatically to transfer water and settlings from holding tank 101 into the clarifiers thereby maintaining the water in the holding tank clean and relatively free of settlings. This transfer takes place for a preselected period, such as five minutes, immediately following shut down of main motor 70. For this purpose there is provided a second timer identical in construction and mode of operation with timer 157. The solenoid clutch of timer 195 is energized through leads 1% and 197 as the left hand pair of contacts of timer 157 close at the end of the timing period of timer 157 provided relay 153 is de-energized. If manual switch 198 is then closed to the left as illustrated, power is supplied through

timers

157 and 195 via leads 1%, 197 and 194 to energize the solenoid of starter 189. Motor 133 for transfer pump 133 then operates to remove water and settlings through

pipes

132, 135 and to deliver them into the distributing cups of the two clarifiers. After the time period elapses, the contacts of timer 195 open to shut off the transfer pump. Should the operator wish to operate the transfer pump 133 at other times he may do so simply by closing switch 198 to the right to supply activating power to starter 189 from the hot bus 151. At the end of the operating period, switch 198 is restored to its left hand automatic operating position.

All separated cement stratifies in the bottom of

clarifiers

100, 1%, the depth of the collected cement or slurry gradually rising as the transit mixers dump their contents into the declassifier. As the cement collects, it will be apparent that there is need for storing water displaced by the cement. This is accomplished by the fact that the level of the water in apparatus 11 tends to rise until it reaches the level of overflow lip 123 of return trough 118. When this occurs, the excess clean water merely overflows into the underlying holding tank 1111. Initially, of course, holding tank 101 is empty and each of the clarifier tanks is filled with 1500 gallons of water and the declassifier is filled with water to its normal operating level.

Apparatus having this capacity is found fully adequate to service 12 to 15 transit trucks during a normal operating day and provides adequate storage capacity for all cement slurry separated from the trucks. This includes loads of cement which cannot be delivered as well as residue cement present in the trucks at the end of the operating period and required to be flushed away before the trucks can be placed in the garage. The described system can be easily and efficiently expanded to handle many more transit mixers during each shift simply by increasing the clarifier capacity either by enlarging the described clarifiers or by adding additional clarifiers. It also may be necessary or desirable to increase the capacity of the holding tank.

Operation 07 the sump pump Let it be assumed that drainage from the storage pits and the operation generally results in the water level in sump 17 to approach the top of the sump. This sump is preferably equipped with conventional automatic liquid level responsive electronic controls indicated at 179 and effective to control the starter switch for sump pump 138. In other words, the rise of water to an upper limit closes the starter switch to start the pump motor which then operates to withdraw water and cement settlings through suction pipe 137 for delivery through discharge 135 into the distributing cups of the clarifiers. As the water level falls to near the bottom of the sump, the lower electrode actuates the starter switch to discontinue the operation of the sump pump motor, all without attention of an operator.

Reconditioning f the clarifier and holding tanks At the end of a normal daytime operating period, the two clarifiers will contain a collection of slurry 185 to some level such as that indicated in FIGURE 11. Comparatively clean water and some cement in an amount approximating 500 gallons may also be present in holding tank 191. Further efficient operation of the apparatus necessitates removal of this slurry. This is done by the aid of a suitable slurry transport truck having powerful suction pump means adapted to be connected to the suction conduits 186 and 186' opening into the vertical suction pipes 103, 103' of the two clarifiers. Before the suction line valve is opened, the operator adjusts skimmer cups 145, 145 downwardly to withdraw clean water from above the slurry for storage in holding tank 101. Desirably, substantially all clean water remaining above the slurry is drained into the holding tank by the aid of the skimmers. The slurry is then sucked from the clarifiers into the tank truck for removal to a point of disposal. This operation is usually conducted during the night-time.

Normally, all truck have dumped their loads and have been flushed into the clarifier prior to the end of the usual shift at :00 ocloc-k and certainly not later than 6:00 p. m. in the normal course. To provide assurance that all water in the closed water circuit is thoroughly cleaned before the system is allowed to remain dormant through the night, there is preferably provided a periodic timer clock 190 (lower left corner of FIGURE 1) which remains energized at all times. This clock drives a cam 191 which closes a switch 192 arranged in parallel with master switch 18 and effective to operate the declassifier for a period once during each 24-hour period, such as one hour at the end of a normal day shift to recirculate the water through the clarifiers numerous times. This day-end flushing operation makes certain that all cement contents of the water has had an opportunity to settle out in the clarifiers before the system is allowed to remain dormant overnight. After about one hours time, cam 19 1 by-passes switch 192 to de-energize relay 153. The system continues to operate for the usual short period under the control of timer 157 following which transfer pump 13% is operated by timer "195 for a few minutes before the system automatically cuts off and remains de-energized unless manually activated by the atendant as it can be by operating the reset button 171 of master control starter 170.

It is therefore seen from the foregoing that the transfer pump 133 operates automatically for a short period immediately following each de-energization of main motor 70 to transfer the slurry from tank 101 to the clarifiers by way of conduit 132, pump 133, and conduit 135. The solid contents settle into the clarifiers as the clean Water overflows through the skimmer troughs into tank 14 and through skimmer 115 into trough 118. If the water is below lip 12-3 of trough 118, clean Water flows into the declassifier. But if the water level in trough 11 8 reaches the top of lip 123, it overflows into holding tank 101.

While the particular concrete mix declassifier apparatus and method herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are in tended to the details of construction or design herein shown other than as defined in the appended claims.

I claim:

1. That method of recovering and salvaging useful constituents of concrete mix carried in the drum of a transit mix vehicle, which method comprises, discharging mix present in the transit mix drum along with flushing Water into a mix declassifying chamber, there agitating the mix and flushings in excess water maintained in circulation in a closed loop circuit between said declassifying chamber and a water clarifier chamber, circulating Water laden with cement from said declassifying chamber to said clarifier chamber until the mix is substantially cleansed of cement, discharging the retained solid matter present in the declassifying chamber to a storage chamber therefor located exteriorly of said declassifying chamber, maintaining a captive separate supply of clean flushing water in a return portion of said closed loop water circuit for use in flushing; mix from and washing the interior of a transit mix drum, and utilizing clean water from said captive supply of clean water for flushing and washing the drum of a transit mixer thereby substantially avoiding interfering with the water levels in said water clarifier and declassifying chambers.

2. The method defined in claim 1 characterized in the step of withdrawing excess water from said recirculating body of water into a holding chamber until such time as make-up Water is desired, and then returning makeup water to the water recirculating between said clarifier and declassifying chambers.

3. The method defined in claim 2 characterized in the step of separating the solid matter discharging from said declassifying chamber into separate streams of sand and aggregate, collecting drainage from cleansed sand and aggregate removed from said declassifying chamber and returning the drainage to the water recirculating between said declassifier and said clarifier.

4. The method defined in claim 1 characterized in the step of providing a plurality of clarifier chambers interconnected in said recirculating Water circuit.

5. The method defined in claim 1 characterized in the step of repeatedly tumbling said concrete mix in an excess of water in said declassifying chamber as the Water is being circulated through said mix enroute to said clarifier chamber.

6. The method defined in claim 1 characterized in the step of periodically withdrawing cement sludge from the bottom of said clarifier chamber for removal to a point of waste disposal and replacing the withdrawn sludge with water.

7. That method defined in claim 1 characterized in the step of utilizing movement of the transit mixer into position to discharge concrete mix into said declassifying chamber to operate control means to initiate circulation of water "between said declassifying, clarifier and auxiliary chambers, and continuing said water in circulation for a predetermined limited time and thereupon discontinuing said water circulation until the next transit mixer moves into position to dump concrete mix flushings into said declassifying chamber.

3. That method defined in claim 1 characterized in the steps of maintaining a separate storage chamber for excess and reserve clean water, and transferring water between said separate storage chamber and the remaining chambers in the direction and quantities necessary to maintain a desired operating level of water in each of said declassifying and clarifying chambers.

9. That method defined in claim 1 characterized in the step of withdrawing substantially clean water from the outer rim surface of the water in said clarifying chamber for return gravity flow to said declassifying chamber.

10. That method of flushing the drum of a transit mixer of concrete mix and of recovering sand and aggregate constituents of the mix for reuse which comprises recirculating a captive quantity of water between a declassifying chamber, a clarifier chamber and an auxiliary chamber located in a clean water return portion of said circuit and normally containing a supply of clean water for use in flushing mix into said declassifying chamber, utilizing water from said auxiliary chamber to facilitate cleaning and flushing said mixer drum of mix, discharging said flushing water and mix from the drum into said declassifying chamber, separating cement from said mix in said declassifying chamber by placing the cement in water suspension, circulating cement suspended in water from said declassifying chamber to said clarifier chamber, and skimming and returning relatively clean water from said clarifier chamber to said auxiliary chamber and to said declassifying chamber to replace water and suspended cement withdrawn from said declassifying chamber and to replace clean water withdrawn from said auxiliary chamber for use to flush said transit mixer drum.

11. The method defined in claim characterized in repeating the steps recited in claim 10 repeatedly to flush concrete mix from successive transit mixers utilizing Water from said captive supply of clean water to flush each drum clear of mix and repeatedly recirculating and reusing the same water to separate cement by suspension from the mix and then conveying the water-suspended cement into said clarifier chamber where the cement stratifies as cement sludge in the bottom of said clarifier chamber.

12. That method defined in claim 10 characterized in the step of automatically making a time record of the presence of a transit mixer in servicing position at the declassifying chamber.

16. That method defined in claim 10 characterized in that cement-laden water is delivered into the upper central portion of said clarifying chamber and caused to flow downwardly in a relatively quiescent large diameter column as its cement content gravitates and settles out in the bottom of said chamber.

1-4. That method defined in claim 10 characterized in the step of skimming cement-laden water from the top of said declassifying chamber and forcibly circulating the removed cement-laden water to a large area column of downwardly flowing confined body of water within said clarifying chamber.

15. Concrete mix declassifying apparatus for separating mix into its principal constituents and for salvaging certain of these constituents comprising, declassifying chamber for receiving and flooding concrete mix with quantities of excess water, said concrete mix declassifying chamber comprising an elongated housing having a concrete mix inlet at one end and an outlet means for cleansed solid particles at its other end and wherein both said inlet and outlet means include means for preventing water overflow from said housing, means for agitating said concrete mix in said declassifier chamber, clarifier tank means, means for withdrawing cement-laden water from said declassifying chamber and delivering the same into said clarifier tank means while the cement settles to the bottom of the latter, means for withdrawing substantially clean water from the top of said clarifier tank means and returning the same to said declassifying chamber, and power-driven conveyor means for removing and carrying to a point of delivery cleansed substantially cement-free solid constituents of concrete mix from said declassifying chamber admitted thereto through said inlet.

16. A concrete mix declassifier comprising an elongated tubular housing supported with its axis generally horizontal and having a mix receiving hopper at one end opening into the inlet end thereof and an aggregate discharge opening centrally of its opposite outlet end, rotary tubular trommel means extending lengthwise within said housing having its ends in communication respectively with said inlet and outlet, means for maintaining said housing flooded to .a predetermined level with recirculating water effective to suspend and carry away cement and including cement and water separator means supported independently of said tubular housing, means for conveying drained cleaned sand from the underside of said trommel means, and means for discharging cleaned aggregate through said aggregate discharge opening.

17. A declassifier as defined in claim 16 characterized in that said trommel means includes fluid-tight supporting bearings mounted at the opposite ends of said housing and effective to safeguard against the escape therepast of cement-laden water.

18. A declassifier as defined in claim 16 characterized in that said trommel means comprises a cylindrical body perforated to pass sand while retaining larger particles and aggregate, said body having blade means carried adjacent its interior surface and effective to advance mix materials toward said outlet end, and blade means carried exteriorly of said trommel body and close to the interior surface of said housing effective to advance separated sand into said sand conveying means.

19. A declassifier as defined in claim 18 characterized in that said housing includes a cover normally covering said trommel means, said trommel means including means detachably securing the same in said bearings, and said trommel means being removable as a unit through the opening provided by said cover when in open position.

20. In combination with concrete mix declassifying apparatus, a cement and water separator comprising, a pair of partially nested large volume tanks having means for supporting the same in vertically spaced relation and free of material other than cement and water undergoing separation, said tanks each having downwardly converging bottoms, the upper one of said tanks being a cement and water clarifier having a vertically disposed tubular shroud having a connection for receiving incoming cement-laden water from said concrete mix declassifying apparatus and the lower tank being a clean water storage tank, said shroud confining said cement-laden water and requiring the same to flow downwardly slowly before escaping to the exterior of said shroud as the cement content continues to gravitate and collect in the bottom of said tank, skimmer means for withdrawing a film of clean water from the surface of the Water surrounding said shroud, and means for transferring water selectively in either direction between said tanks.

21. The combination defined in claim 20 characterized in that said water transferring means includes second water skimming means for transferring water by gravity directly from the upper tank to the lower tank down to a level adjacent the surface of collected cement slurry present in the lower portion of the upper tank.

22. The combination defined in claim 20 characterized in that said water transfer means includes pump means for transferring cement slurry from the bottom of the the lower tank to the upper portion of said tubular shroud in said upper tank whereby the cement con-tent separates out and settles to the bottom of the upper tank.

23. The combination defined in claim 22 characterized in the provision of suction conduit means for withdrawing slurry from the bottom of said upper tank as the overlying Water content of the tank aids in pressing the slurry toward the inlet of said suction conduit means.

24. The combination defined in claim 20 characterized in that said cement and water separator comprises a plurality of cement settling tanks in laterally spaced relation each normally flooded with water and each having downwardly converging bottom walls, each of said settling tanks having similar tubular shrouds for receiving cementladen water and similar skimmer means for withdrawing clean water from the water surface exteriorly of said shrouds.

25. The combination defined in claim 24 characterized in the provision of skimmer means in each of said settling tanks independent of said first mentioned skimmer means, said skimmer means being adjustable in height and each including connection means for withdrawing water from the portions of said settling tanks above the collected slurry and draining the withdrawn Water into the lower one of said nested tanks.

26. The combination defined in claim characterized in the provision of means including pump means for returning water from the lower one of said nested tanks selectively to the interior of the tubular shroud means of either of said settling tanks, said returned water including slurry settling out in the bottom of said lower tank.

27. In concrete mix declassifying apparatus of the type having mix declassifier means connected in a closed fluid circuit with clarifier tank means, that improvement which comprises means for maintaining separate predetermined water levels in said declassifier and in said clarifier tank despite changing quantities of mix and of cement slurry therein, said last mentioned means including first skimmer means for withdrawing cement-laden water from the surface of the water in said declassifier and delivering the same to said clarifier tank, second skimmer means for withdrawing clean water from the surface of the water in said clarifier tank and returning the same to said declassifier, an excess water storage tank, and means for draining excess water automatically from said closed circuit into said storage tank when the water level rises above a predetermined level in a part of said closed water circuit.

28. Declassifying apparatus as defined in claim 27 characterized in that said excess water storage tank underlies said clarifier tank means, and in that said means for draining excess water into said storage tank includes duct means extending horizontally between said storage tank and said declassifier and having an overflow lip overlying said storage tank and from which water overflows when the level in said declassifier rises above a desired operating level.

29. Declassifying apparatus as defined in claim 28 characterized in the provision of an auxiliary water storage tank located in said closed water circuit and including skimmer means for transferring clean water from the upper portion thereof into said duct means extending between said clarifier tank and said declassifier, and means for utilizing water from said auxiliary tank to add to concrete mix before the mix is delivered to said declassifier thereby to facilitate handling of said mix, said auxiliary water tank and the skimmer means thereof functioning to permit intermittent use of quantities of clean water from said closed water circuit without adversely afiecting the water level or flow conditions in said clarifier tank.

30. That method of cleansing and treating the residue from the interior surfaces of a transit mixer for fluent concrete mix which comprises, flushing the surfaces clean and flooding the discharge constituents with circulating captive water, suspending the cement constituents of the concrete mix in the captive water, removing the cementladen water to a settling zone and there allowing the cement to gravitate while withdrawing relatively clean water for reuse in cleansing discharge from transit mixers, utilizing the presence of transit mixers at a preselected mix discharge position to actuate control means for initiating cycling of the cleansing operation, and automatically discontinuing the cleansing operation a predetermined period after a transit mixer has pulled away from discharging position.

31. That method defined in claim 30 characterized in the additional steps of automatically making a record of each discharge and cleansing operation as an incident 18 to the movement of a transit mixer into and out of discharge position.

32. That method defined in claim 30 characterized in the additional steps of draining excess liquid from said recirculating water circuit into storage reservoir as cement slurry collects in the bottom of said settling zone and displaces water, and automatically transferring water and settlings from the bottom of said storage reservoir to said settling zone from time to time to keep said storage reservoir clean and available for the storage of excess clean water.

33. A concrete mix declassifier for separating the sand aggregate and cement constituents thereof from one another comprising an elongated tubular housing having a mix receiving hopper at one end, a trommel journaled generally horizontally lengthwise of said housing with one end positioned to receive mix from said hopper, means for flooding the lower portion of said housing and of said trommel with water, means carried by said trommel for advancing constituents of said mix along the trommel while tumbling them in said water, means carried by said trommel at the discharge end thereof for discharging aggregate from the end of said trommel, means for continuously lifting sand above the water level from the exterior of said trommel and discharging the same from said housing, and means for skimming cement-laden water from surface areas of thewater present in said housing and carrying away the cement constituent of the mix from said declassifier.

34. A concrete mix declassifier as defined in claim 33 characterized in that said housing includes an enlargement extending along one lateral side thereof opposite the water level, and water intake manifold means extendi-ng into the cement laden-water in said enlargement for carrying away a mixture of water and suspended cement.

35. A declassifier as defined in claim 33 characterized in that said trommel includes helical blades means projecting inwardly from the interior thereof to advance mix from said receiving end to said discharge end.

36. A declassifier as defined in claim 35 characterized in that said trommel includes second helical blade means secured thereto and spaced outwardly of its exterior and close to the interior surface of said housing to advance small constituents of said mix from said receiving end toward said discharge end.

References Cited by the Examiner UNITED STATES PATENTS Re. 22,652 6/1945 Reybold 210-256 458,823 9/1891 Cook 209-270 622,507 4/1899 Mason 209-270 686,263 11/ 1901 Conley 209-44 1,467,348 9/1923 Young 209-270 1,895,504 1/1933 Wuensch 209-1725 2,518,451 8/ 1950 Damon 209-423 2,530,676 11/1950 Berg 209-17 2,942,731 6/ 1960 Soldini 209-293 2,956,681 10/1960 Benson 209-464 2,983,378 5/1961 Hilkemeier 209-452 X FOREIGN PATENTS 5 47 5/ 1896 Denmark.

FRANK W. LUTTER, Primary Examiner.

ROBERT A. OLEARY, Examiner.