US3011414A

US3011414A - Method and apparatus for moving cementitious compositions

Info

Publication number: US3011414A
Application number: US694883A
Authority: US
Inventors: Herbert A Stein
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-11-06
Filing date: 1957-11-06
Publication date: 1961-12-05
Anticipated expiration: 1978-12-05

Description

H. A. STEIN 3,011,414

METHOD AND APPARATUS FOR MOVING CEMENTITIOUS COMPOSITIONS 4 Sheets-Sheet 1 Dec. 5, 1961 Filed Nov. 6, 1957 INVENTOR HERBERT A.STE|N 812W W ATTORNEY6 FIG. 1.

Dec. 5, 1961 H. A. STEIN 3,011,414

METHOD AND APPARATUS FOR MOVING CEMENTITIOUS COMPOSITIONS Filed Nov. 6, 1957 4 Sheets-Sheet 2 INVENTOR HEBERT A. STEIN 92 yw wm fww ATTORNEY S Dec. 5, 1961 METHOD AND APPARATUS FOR MOVING CEMENTITIOUS COMPOSITIONS Filed Nov. 6, 1957 H. A. STEIN 3,011,414

4 Sheets-Sheet 3 HERBERT A. STEIN ATTORNEYS 1951 ,H. A. STEIN 3,011,414

METHOD AND APPARATUS FOR MOVING CEMENTITIOUS COMPOSITIONS Filed Nov. 6, 1957 4 Sheets-Sheet 4 276 INVENTOR HEBERT A.STEIN ATTORNEYS 3,011,414 METHOD AND APPARATUS FOR MOVING CEMENTITIOUS COMPGSITIONS Herbert A. Stein, H. A. Stein-Company, 2001 W. Front St., Chester, Pa. Filed Nov. 6, 1957, Ser. No. 694,883 12 Claims. (Cl. 94-44) This invention relates to material handling and more particularly to a method and apparatus for moving mixtures such as structural concrete, insulating concrete, plaster, acoustical plaster, exterior stucco, masonry mortar, refractory cement, and the like, from a position of availability to a position of desired use.

In the present state of the art, if these two positions are too far apart, making transfer by chutes impractical, the mixtures are carried in wheelbarrows, powered bug; gies, or in hand held hods to the position of use, where they are then poured, troweled, or sprayed into place. If the position of use is at a higher elevation than the mixer, the mixture is usually elevated by means of a bucket hoist on a scaffold or hoisted by a crane. Pumping methods are in limited use, usually involving positive displacement pumps, such as the piston pump and the moving cavity pump. The principal disadvantage of these methods, even where the mixture cannot be harmed by the high pressures needed for pumping, is that in order to transfer the mixture at an economically fast rate, rigid pipe of considerable diameter must be used, and the expense of setting this up and moving it, make this method more expensive under most conditions than the hoist and buggy method. Another disadvantage is that in pumping mixtures, such as insulating concrete, lightweight plaster, and acoustical plaster, where the pressure required to pump them is suihcient to break down the particles in the mixture, so much volume and acoustical and insulating properties are lost that the manual or batched method, though more laborious, proves less costly. For example, when trying to pump lightweight concrete containing a lightweight and hence porous aggregate, the slurry (consisting of binder and water) is forced into the pores of the aggregate, converting the mass from a plastic substance capable of flowing into a solid which defies moving no matter what pressure is applied.

Those skilled in the art will readily appreciate, that the requirement of low slump in cementitious mixtures makes it very diflicult to pump these mixtures, as low slump corresponds to high viscosity, and the pressure required to pump a fluid at a given rate through a given system is roughly proportional to its viscosity. In accordance with the principles of the present invention, pumpability of these mixtures is increased by adding more water and thereby decreasing the viscosity. This produces a high slump which makes the mixtures difficult to place, especially on slopes or on a vertical surface, and the extra water also generally weakens the final set product. The present invention avoids this difficulty by removing the excess watercontinuousiy at the pointof discharge, this water, usually containing a certain amount of the finer ingredients or binder material,

States Patent gate cementitious compositions which includes the steps of diluting the composition to effect settling of the coarser aggregate and then pumping the finer ingredients and Water as a slurry to the position of use while metering out the settled coarser aggregate into the slurry flow to be mixed and carried thereby to the position of use.

A further object of the present invention is the provision of an apparatus of the type described particularly adapted for use in handling heavy aggregate cementitious compositions which includes means for separately handling the coarser aggregate and other finer ingredients and water so that only the latter are passed through the pump for conveying the composition.

A still further object of ihe present invention is the provision of an apparatus of the type described embodying improved means for applying the composition at the position of use.

These and other objects of the present invention will become more apparent during the course of the following detailed description and appended claims.

The invention may best be understood with reference to the accompanying drawings wherein illustrative embodiments are shown,

In the drawings:

FIGURE 1 is a side elevational view, partly broken away, of an apparatus embodying the principles of the present invention;

FIGURE 2 is a side elevational view, partly broken away, of a modified form of the thickening or separating device of the apparatus;

FIGURE 3 is a View similar to FIGURE 2 showing another modified form of the separating device;

FIGURE 4 is a view similar to FIGURE 2 showing a further modified form of the separating device;

FEGURE 5 is a top plan view of a still further modified form of the separating device;

FIGURE 6 is a cross-sectional view taken along the line 6-6 of FIGURE 5;

FIGURE 7 is a side elevational view of a modified form of the mixing and pumping device of the apparatus; and

FIGURE 8 is a view similar to FIGURE 7 showing another modified form of the mixing and pumping device.

Referring now more particularly to the drawings, there is shown in FIGURE 1 an apparatus, generally indicated at 10, which embodies the principles of the present invention. In general, the apparatus 10 includes a mixing and pumping device, generally indicated at 12, in which a cementitious composition is mixed with excess water and binder, at a position where the ingredients of the composition are available, and then pumped from such position. Conduit means, generally indicated at 14, is providedfor being returned tothe point of introduction of the ingredients. 7

Accordingly, it is an object of the present invention to provide a method of transporting cementitious compositions from a position of availability to a position of use which overcomes the disadvantages noted above.

Another object of the present invention is the provision of an apparatus of the type described which is simple, but effective in operation.

Still another object of the. present invention is the.

provision of a novel method of handling heavy aggreconveying the pumped mixture from the device 12 at the position of availability to a remote position of use. At the position of use, there is provided a thickening or separating device 16 which receives the water and binder rich mixture and separates the excess Water and binder from the remainder of the composition. Finally, the excess water and binder from the separ-atingdevice' 16 is returned to the mixing and pumping device by conduit means ind'icated at 18.

' The mixing and pumping device 12 comprises a mixing container orhopper 20 having a material receiving chute 22 at the upper endof one side thereof. The lower interior of the hopper 2% is divided into a plurality of sections by weirs or divider plates 24 and 26. Extending through the axis of the hopper 20 is a shaft 28 having longitudinally spaced mixing blade assembles 30, 32 and 34 mounted thereon for rotary movement within the sections provided by the divider plates 24 and 26. A bottom discharge opening 36 is provided in the hopper section remote from the material receiving chute 22 and a discharge duct or pipe 38 extends from the opening 36 to a pump, generally indicated at ll).

The pump 40 includes a housing 42 having a diaphragm 44 of a suitable resilient material, such as rubber or the like, mounted on the upper end thereof. Disposed in the lower portion of the housing 42 i a cushion pad 46 of rubber or other suitable yieldable material, which serves to prevent injury to the pump when large particles of aggregate or foreign matter are passed therethrough. An inlet valve 48, of any suitable construction, is disposed between the end of the discharge duct 38 and the housing 4-2 and a discharge valve Si is disposed in the outlet side of the housing 42.

The diaphragm 44 is moved toward and away from the cushion 46 by any suitable means, such as a connecting rod 52 having its lower end suitably secured to the diaphragm and its upper end provided with a cam follower 54. An eccentric circular cam 56, of conventional construction, is disposed within the cam follower 54 and is mounted on a shaft 58.

Any suitable means may be provided for rotating the pump shaft 58 and, as shown, an internal combustion engine 60 is utilized which also serves to drive the mixing shaft 28. To this end, the output shaft of the engine 61) is connected to the input shaft of a gear box 62 by any suitable means, such as a belt and pulley assembly 64, and the output shaft of the. gear box is connected to the pump shaft 58 and mixing shaft 28 by any suitable means, such as sprocket and

chain assemblies

66 and 68 respectively.

It will be seen that during the movement of the diaphragm 4 t away from the cushion 46, mixture will enter through the inlet valve 48 from the duct 38 to fill the housing. On the downstroke of the diaphragm, the mixture in the housing will be forced out through the discharge valve Eli and into an air surge tank 76 connected therewith. When using air entraining admixes in concrete, the air bubbles in the mixture can cause the pump to become very weak, due to compression of the air in the material in the pump housing on the downstroke of the piston and expansion of the air on the upstroke. This can be avoided or minimized by filling in the pump housing so that as little volume remains as possible during the downstroke. This is the primary purpose of the cushion pad 46, which, as noted above, also serves to minimize the danger of breaking a connecting rod in the event that some large piece of foreign matter inadvertently gets into the space between the diaphragm and the cushion pad. The pump 40 forces the mixture into the surge tank '70 intermittently on the pressure or downstroke. The surge tank 76 is filled with air, which is replenished continuously from the air entrained in the mixture by the agitating action of the paddles in the mixer. The air space in the upper portion of the surge tank 7% is compressed on the pressure stroke of the pump and expands on the upstroke. In this way, the pressure of the mixture leaving the surge tank 70 remains at relatively constant pressure, regardless of whether the pump ill is on the intake or the pressure stroke. For greater output rates, a plurality of pumps can be used, connected together at input and output sides by means of manifolds.

The conduit means 14 may be of any suitable construc- ,tion and, as shown, includes a hose 7?. of conventional form having one end connected with the outlet of the surge tank and its opposite end extended to the position of use and provided with a discharge nozzle 74- of gooseneck configuration, operable to dischargethe water rich rnixture conveyed through the conduit means 14 by the pump 40 to the separating device 16.

' The separating means 16 comprises a downwardly inclined screen 76 of conventional construction having its upper end disposed below the nozzle 74 to receive the water rich mixture discharging therefrom. Surrounding the undersurface of the screen 76 and supporting the same is an inclined water collection box 78 having a bottom above the screen to prevent the mixture from spilling over the sides of the screen. It will be seen that as the water rich mixture passes over the downwardly inclined screen 76, the excess water thereon will pass therethrough into the collection box 78, thereby thickening the mixture or separating the excess moisture from the composition so that the latter issues from the lower end of the screen to the position of use at the desired mix ratio or consistency.

In order to prevent clogging of the screen, a vibrating device 8-4 of conventional construction is bolted or otherwise secured to the bottom wall 86 of the'box 78. The device 84 is actuated by any suitable means, such as a compressor 86 positioned adjacent the mixing and pumping device to be driven by the engine 60 thereof through any suitable means, such as a belt and pulley assembly 88. Compressed air from the compressor 86 is directed to the vibrating device 84 by an air hose 9% or the like.

The excess water collected in the lower portion of box 78 discharges through an outlet 92 provided in the lower end thereof and the outlet 92 is connected to one end of a hose 94 of conventional construction, which constitutes the excess water conduit means 18. The opposite end of the hose 1% extends to the mixing and pump ing device 12 and, preferably, is connected to an inlet pipe 96 of a pump and surge tank assembly 98 of a construction similar to the pump 44 and surge tank '70 previously described. Because of this similarity, a detailed description is not believed to be necessary. Suffice it to say, that the assembly 98 includes an air surge tank 109 communicating with the inlet pipe 96, a pump housing 1812, an inlet valve 104 between the surge tank and housing, and a cushion pad 106 and diaphragm 10 8 in the housing, the latter moved up and down by a connecting rod 115 and cam assembly 1-12 operatively connected with the shaft 58. The outlet of the housing 102 has a valve 114 therein and communicates with one end of a water inlet duct or pipe 116, the other end of which communicates with the upper end of the mixing hopper 20 adjacent the material receiving chute 22-.

Make up water is supplied to the mixing hopper from a pipe 118 connected with a suitable water source (not shown) and having a conventional valve 120 on the downstream end thereof. A short pipe 122 connects the valve 1120 with one side of a water meter 124, the other side of which is connected with the inlet pipe 96 through a pipe 126. The Water meter serves as a guide to the operator to determine the proper setting of the valve 12-6, as will hereinafter be more fully explained.

In FZGURE 2, there is shown a modified form of the separating device which includes a downwardly inclined screen 128 having the nozzle 74 of the hose 7-2 disposed to discharge the water rich mixture on the upper end thereof. A collection box 130 surrounds the undersurface of the screen-and supports the same. The box 130 includes side walls 132 which extend above the level of the screen to prevent the mixture from running off the sides thereof. In contradistinction to the box 78 previously described, the box 13 0 has a series of apertures 134 formed in each side wall 132 thereof. Mounted for sliding movement on each side wall in a position covering the apertures 134 thereof is a slide bar 136 having a corresponding series of apertures 138 formed therein. It will be seen that the operating vacuum in the lower portion of the collection box can be varied by moving the slide bars to provide more or less registry between the apertures 1341 and 138. Of course, as before, the lower end of the collection box has an outlet pipe 140, which is connected with the hose 94 leading to the water pump.

, In FIGURE 3, there is shown another modified form of the separating device in which the vibrating device has been replaced with an endless scraping assembly 142. As before, the device includes a downwardly. inclined screen mounted in a collection box 146 having upstanding side walls .148 and a lower outlet pipe 149 connected to the hose 94, as in previous constructions. The assembly 142 is mounted between the side walls 148 above the screen 144 and includes a pair of spaced shafts 150, each having a pair of sprocket wheels 152 mounted thereon adjacent the side walls. A sprocket chain 154 is trained about the sprocket wheels 152 adjacent each side wall and aplurality of scraper elements or blades 156 are suitably mounted between the chains 154 so as tobe moved in an endless path thereby having a lower run in scraping relation to the upper surface of the screen 144. The assembly 142 may be moved by any suitable means and, as shown, an air motor158 is provided which may be conveniently driven by the compressor 86, through connection of the air hose 90 therewith. The air motor 158 has its output shaft connected with the upper shaft 152 by any suitable means, such as a sprocketand chain assembly 160.

'In the embodiments described above, the composition with the excess water removed by the separating device discharges from the lower end of the screen to the position of use. For special applications, means may be incorporated in the separating device for directly applying the composition as it discharges therefrom. In FIG- URE 4,- there is shown an arrangement for spraying the composition'on vertical surfaces or the like. To this end, atube 162 is connected to the air vibrating device84 to receive the compressed air passing therethroughl" The-tu-be extends through the bottom wall 80 or the collection box 78 into the interior thereof and terminates-in a nozzle 164 disposed adjacent the lower end of the screen. Preferably, the nozzle 164 is elongatedhorizontally so that it extends the width of the screen. In this way, the air jet issuing therefrom serves to propel the composition discharging from the lower end of the screen outwardly in a spray which can be conveniently directed to deposit on a vertical surface or the like. If desired, instead of horizontally elongating thenozzle 164, suitabledeflector plates may be provided on the; lower .end of the screen to direct all of the.compositionlto'the.central portion thereof where .an air jet is "created by a .circular nozzle for propelling the composition.

In FIGURES S and 6,.there is shown a specially constructed separating device, generally indicated at 166, particularly. suited for applying the composition in horizontal slab or carpet formationof a desired width. The device 166 comprises a transversely extending frame 168 having an upright frame member 170 rigidly secured to each end thereof and extending upwardly'therefrom. A headertube 172 is disposed between the upper ends of the frame members 170 and has opposite end portions extending therethrough and rigidly secured therewith, as by welding or the like. Aparallel frame member 174 is disposed outwardly of each frame member 170 and each has its upper end rigidly secured to the header tube, as by weldingor the like. Supported between the lower ends. of each pair of

parallel frame members

170 and 174 isa wheel 176, which serves to support the frame for movement along a roof or other structure where the slab is to be-applied. Suitable means, preferably in the form of handles 178 rigidly mounted on the frame, is provided for effecting movement of the frame.

collection box 186 1n0unted above the transversely extending frame 168 by means permitting vibratory movement thereof, such as a plurality of coil springs 188. As before, the box 186 includes a bottom wall 190 having an air-actuated vibrating device 192 fixed thereto, a pair of side walls 194 extending above the level of the screen to prevent side spillage of the mixture thereon, and a water outlet pipe 196 leading from the lower end thereof and connected with the hose 94.

Rigidly secured to the outer surface of each frame member 174 adjacent its lower end is one end of a resilient plate 198 which is preferably made of spring steel or some other material of similar properties. The opposite end of each plate 198 extends horizontally beyond the associated side wall of the collection box in parallel relation therewith and is connected with a transversely extending leveling board 200, as by brackets 202 or the like. The leveling board 200 is arranged to ride on a pair of parallel forms or screeds 204 between which the slab is to be applied and is transversely oscillated to level off the upper surface of the slab. Any suitable means may be utilized to effect the oscillation of the board and, as shown, a pneumatic piston and cylinder unit 206 is provided. The unit 206 includes a cylinder 208 which is rigidly connected with one end of a diagonal bar 210 having its other end fixed to the central portion of' the header tube 172. Extending outwardly from the other side of the cylinder 208 is a piston rod 212 which is fixed to the lower end of the adjacent bracket 202. Com pressed air from the compressor 86 is alternately delivered to opposite ends of the cylinder by a valve 214 having a suitable hose 216 leading thereto from the compressor. The valve includes a pair of

plungers

218 and 220 which extend outwardly therefrom and cooperate with a bracket 222 secured to the upper end of the bracket 202 to direct the air fiowto the opposite cylinder end when the piston reaches the end of its travel in either direction.

In the embodiments of the invention thus far described, the ingredients of the cementitious composition are initially mixed simultaneously with the mixture of an excess of water therewith in the mixing hopper 20. The present I ceive the composition from the ready-mix concrete truck The header tube 172 receives the water rich mixture pumped from the mixing and pumping device through the hose 72, as by a pipe 180 connected to the end of the hose 72 anud to the central portion of the header tube, and delivers thesame througha'plurality of longitudinally spaced nipples 182 extending downwardly therefrom. A downwardly inclined screen 184 has its upper end disposed'ina position to receive themixture issuing through the nipples 182in the same manner as previously ,de-

scribed in connection with the embodiment of FIG- URES 1-4.

224. Extending horizontally into the central portion of the hopper is a discharge pipe 230 of a centrifugal water pump 232 having its inlet side connected with the hose 94 leading from the-excess water collection box of the separating device utilized therewith. The end'of the pipe 230 is curved downward along the axis of the hopper and terminates in a nozzle 234 from which the excess water discharges with a velocity suflicient to effect a mixing thereof with the pre-mixed composition of the hopper. The lower endof the hopper 228has a pipe 236 leading therefromwhich is connected with the inlet side of asecond centrifugal pump 238 having its outlet side connected with the hose 72 for conveying the water rich mixture to the separating device. Both of the

pumps

232 and 238 are of conventionalconstruction and are driven by any suitablemeans, such as an internal combustion engine 240 having its output shaft connected with the input shafts of the pumps 232 and 23:08 by'belt and pulley ingredients. The device 246 includes a mixing hopper 248 arranged to receive the composition from the premix truck 224. The excess water is introduced into the central portionof the hopper by a siphon pump 25%), here'- inafter to be more fully described. The mixture of the excess water with the heavy aggregate containing composition causes the coarser aggregate to settle to the bottom of the hopper and the finer ingredients to remain in the upper portion of the hopper as a slurry. A pipe 252 communicates the upper portion of the hopper 248 with the inlet side of a centrifugal slurry pump 254 which draws the slurry from the hopper and delivers it into an outlet pipe 256. Preferably, a screen 258 is provided in the hopper adjacent the connection of the pipe 252 therewith to prevent coarse particles from passing therethrough and into the pump.

The coarse aggregate which settles to the bottom of the hopper 24% passes into a housing 26% which communicates at its lower end with the pipe 256. A horizontal shaft 262 is journaled in the housing 260 and has a plurality of radially extending blades or paddles 264 secured thereto within the housing which serve to meter the coarser aggregate into the slurry flow in pipe 256. The pipe 256 extends from the housing 260 and is connected with the hose 72, which conveys the water rich mixture to the separating device utilized.

The siphon pump 250 comprises a nozzle 266 of venturi configuration having a side inlet nipple 268 communicating with the restricted area thereof. The nipple 268 is connected with the hose 94 leading from the excess Water collection box of the separating device. A high velocity 'et of slurry is made to flow through the nozzle 266 by a pipe 270 leading from the pipe 256 intermediate its connection with the pump 254 and housing 260, and terminating in a nozzle 272 having its axis aligned with the axis of the nozzle 266. The flow of the slurry through the restriction of the nozzle 266 creates a partial vacuum in the nipple 268 so that the excess Water therein is drawn into the nozzle 266 and discharged with the slurry into the'hopper through outlet 274.

As before, the pump 254 is rotated by any suitable means, such as an internal combustion engine 276 having its output shaft connected with the pump through a belt and pulley assembly 278. The shaft 262 is also driven in predetermined relation With respect to the pump by the engine 276 through a gear box 286 connected with the shaft and with the engine output shaft by means of a belt and pulley assembly 282.

Operation and procedure In the operation of the apparatus shown in FIGURE 1, the mixing and pumping device 12 is set up at a convenient site, preferably at a position of availability of the composition ingredients, as between piles of aggregate and binder, and the water supply is connected'to the valve 124). It is important to have a sufiicient pressure and a pipe 118 of adequate size so as to insure an essentially constant supply of water once this has been set on the valve 12%} according to the reading of the water meter 124. The separating device 16 is set up at the desired position of use and the three

hoses

72, 90 and 94 are connected to the separating device. Then the engine 60 is started, causing the output pump 40, the return pump 98, the mixer shaft 28, and the air compressor 86 to rotate. The water valve 12% is opened to a definite flow 7 rate indicated onthe water meter 124, and the time necessary to fill up the sections of the hopper 20 to the height of the weirs 24 ancl26 is measured. By multiplication, the amount of water inthe system is deter mined, and the corresponding amount of binder isadded to the hopper through chute 22 according to the binderto-water ratio specified in the mix design. Once this circulating slurry is prepared, the mix can proceed accordo in maintain a mixture in the hopper 20 of about pumpable consistency. During the entire run, which can last for a full day or more if desired, the initial amount of extra binder and water which was put in remains circulating in the apparatus at all times, carrying the mixture up to the separating device 16 and returning via the return hose 94.

To stop pouring concrete, the insertion of aggregate is ceased and the system is allowed to circulate until no more concrete comes off the screen. Starting up again is accomplished simply by beginning to put in the aggregate, binder, and Water in the correct proportions again. When shutting down for a period of such length that the binder would begin to set up in the system, it is necessary, of course, to clean out the whole system with fresh water.

As one example of the operation of the present invention, with a cementitious composition issuing from the discharge end of the screen 76 of the FIGURE 1 appa ratus having a mix ratio of 12 gallons of water to 94 pounds of cement binder and 6 cubic feet of aggregate, an excess of 24 gallons of water and 188 pounds of binder were kept circulating in the system.

It will be understood that any of the mixing and pumping devices disclosed may be used in combination with any of the separating devices disclosed and that the: invention is not limited to those combinations shown. In general, the mixing and pumping device 12 shown in FIGURE 1 is used where the ingredients of the composition are initially mixed at the position of availability, whereas the devices shown in FIGURES 7 and 8 are utilized where pre-mixed composition is available.

The device 12 disclosed in FIGURE 1 is especially suitable for most fine compositions and could be utilized even with compositions containing coarse aggregate. The construction of the diaphragm pumps 44} and 98 is such that they can handle fine aggregate material with a highly effective operation and coarse aggregate without too much difficulty. The manner in which the excess water is separated from the water rich mixture fed to the screen to obtain a composition'of desired mix ratio and consistency is believed to be evident from the above description. Of particular significance, is the operation of the device shown in FIGURE 4 wherein a jet of compressedair is discharged into the composition issuing from the screen to spray the composition onto a vertical surface. It will be apparent that the composition is entrained by the air jet and propelled toward the vertical surface where it deposits thereon as directed.

The operation of the device illustrated in FIGURES 5 and .6 is also of particular significance where slabs or carpets of concrete are to-be formed. It will be noted that the pneumatic cylinder and piston unit 206 is effective to transversely oscillate the leveling board 200 which is mounted on the frame 163 by the resilient plates 198 So as to readily permit such movement. While a vibratr ing device 192 is shown to prevent clogging on the screen 184, it will be understood that the arrangements shown in FIGURES 2 and 3 may be utilized if desired, in which case, the springs 188 may be eliminated and the collection box maybe fixed directly to the frame.

The device 226 shown in FIGURE 7 is particularly suited for handling composition containing fine heavy ining to the proper ratio of aggregate -hinder and water,

the solid ingredients being put in whenever needed to gredients and operation thereof is best carried "out by maintaining the amount of water introduced with the concrete from the truck the same as the amount of water in the concrete issuing from the screen at the position of use. If not, an excess ordeficiency of water will be noted in the hopper 228 and the batching operation of theconcrete can be modified to include drier or wetter subsequent batches. Of course, excess binder -in proportion to the water is added also, as before. In an entergency, if the mixture in the hopper 228 is too 'wet, the excess slurry can be allowed to overflow onto the ground, or ifthe mixture in the hopper 228 is too dry, extra water All 9 may be added to maintain sufiicient fluidity in the material to be passed through the pump 238.

The device 246 shown in FEGURE 8 is particularly suited for handling compositions containing heavy aggregate in that the heavy aggregate is handled separately from the fine ingredient slurry of the composition and never has to pass through a pump. The correct consis tency is maintained in this device in the same manner as the device 226 shown in FIGURE 7. In normal operation, some of the slurry in the hopper 248 is carried with the aggregate into the housing 260, but the major part passes through the screen 258 and overflows into the pipe 252. The slurry in the pipe 252 is given a positive flow pressure by the pump 254 as it passes therethrough and the heavy aggregate is metered by the paddles 264 into this flow to be mixed therewith and carried thereby through the hose 72 to the separating device.

It thus will be seen that the objects of this invention have been fully and effectively accomplished. It will be realized, however, that the foregoing specific embodiments have been shown and described only for the purpose of illustrating the principles of this invention and are subject to extensive change without departure from such principles. Therefore, this invention includes all modifications encompassed Within the spirit and scope of the following claims.

I claim:

1. A method of transporting a cementitious composition comprising an aggregate, a binder and'water in a predetermined mix ratio from a position of availability to a remote position of use which comprises the steps of mixing with the composition at the position of availability an amount of water and binder sufiiciently in excess of that required by the predetermined mix ratio to lower the viscosity of the composition to a pumpable value, pumping the water and binder rich mixture to a position of separation adjacent the position of use, removing the excess water and binder at the position of separation, and returning the removed excess water and binder to the position of availability for mixing with further composition.

2. A method as defined in claim 1 wherein the aggregate, binder and water of the composition are mixed simultaneously with the mixing of the excess water and binder.

3. A method as defined in claim 1 wherein the aggregate, binder and water ofthe composition are mixed subsequent to the mixing of the excess water and binder therewith.

4. Apparatus for transporting a cementitious composition of the type including an aggregate, a binder and.

water in a predetermined mix ratio from a position of availability to a remote position of use comprising means for mixing an excess of water and binder with the composition arranged to be disposed at the position of availability, said mixing means including cooperating blade means, means including a screen'having an aperture size sufficient to pass the binder and water but to retain the aggregate arranged to be disposed at the position of use for separating the excess water and binder from the mixture of composition and excess water and binder, mixseparating means, and excess water and binder conduit' means for recirculating the excess water and binderseparated by said separating means to said mixing means.

5. Apparatus as defined in claim 4 wherein said separating means includes means for preventing said screen from becoming clogged.

6. Apparatus as defined in claim 5 wherein said screen clog preventing means comprises a vibrating device for shaking said screen.

7. Apparatus as defined in claim 5 wherein said screen clog preventing means comprises an endless conveyor having scrapers movable along the surface of said screen.

8. Apparatus as defined in claim 4 wherein said mixing means comprises a housing for receiving the aggregate, binder and water and a rotor journaled in said housing and having mixing blades for mixing the aggregate, binder and water together.

9. Apparatus as defined in claim 4 including means operatively connected to said separating means for leveling the separated composition applied at the position of use.

10. Apparatus as defined in claim 4 including means operatively connected to said separating means for apply ing the separated composition at the position of use including means providing a continuous jet of air in the path of movement of the separated composition for spraying the same on substantially vertical surfaces.

11. Apparatus as defined in claim 9 wherein said wardly extending screen carried by said frame, means for feeding a cementitious composition containing excess water and binder to the upper end of said screen along the width thereof, means on said frame for collecting the excess water and binder issuing through said screen, an oscillating member carried by said frame in spaced relation to the lower end of said screen for leveling off the dewatered composition issuing therefrom, means remote from said frame for receiving composition, excess water and binder conduit means between said collecting means and said composition receiving means, and means for pumping and conveying the composition and excess water and binder from said remote receiving means to said feeding means.

References Cited in the fileof this patent UNITED; STATES PATENTS 1,091,251 Stauffer Mar. 24, 1914 1,878,278 Jaeger Sept. 20, 1932 2,068,783 Wendell "Jan. 26, 1937 2,078,235 Chapman Apr. 27, 1937 2,201,534 Hallenbeck May 21, 1940