Title:
Concrete mixer
United States Patent 2338820


Abstract:
This invention relates to concrete mixers, and refers particularly to truck or transit mixers. Concrete mixers of this type are mounted upon truck chassis and have their drums rotatable either by means of the truck engine, or a separate engine. In the earlier types of truck mixers, the drum...



Inventors:
Peters, Harry C.
Application Number:
US31371040A
Publication Date:
01/11/1944
Filing Date:
01/13/1940
Assignee:
T L SMITH COMPANY
Primary Class:
Other Classes:
239/288, 239/533.14, 366/44, 366/59
International Classes:
B28C5/42
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Description:

This invention relates to concrete mixers, and refers particularly to truck or transit mixers.

Concrete mixers of this type are mounted upon truck chassis and have their drums rotatable either by means of the truck engine, or a separate engine.

In the earlier types of truck mixers, the drum was loaded through a hatch opening which had to be opened and closed by the driver. This was obviously an inconvenience.

To overcome this disadvantage of the earlier type of truck mixer and to effect other improvements, the construction illustrated in Patent No. 2,029,126, issued January 28, 1936, to Adolph W.

Rybeck, for "Mixing apparatus" was developed.

With this new design, the drum was loaded and discharged at the same end.

Since the issuance of the aforesaid Rybeck patent, it has been found that an end to end mixing action is best suited to transit mixers, and where the mixer is completely charged at the batching plant, that is, charged wet for mixing during transit satisfactory mixing action was obtained.

However, in instances where the drum had to be loaded dry as is the case in some localities where regulations require the mixing to be done on location under the supervision of inspectors, the means employed for introducing the water into the drum was found inadequate and responsible for improper mixing, notwithstanding the end to end mixing action. This resulted from the fact that water introduced in the ways heretofore known did not reach the bottom of the mass, which in drums of this type, is directly adjacent to the closed front end of the drum.

It is, therefore, an object of the present invention to provide an improved manner of introducing the water.into the mixing drum. More specifically, it is an object of this invention to provide means for introducing water into a previously dry loaded drum in such a manner that the water definitely reaches the bottom of the mass adjacent to the closed front end wall of the drum to form a wet zone thereat.

With this arrangement the closed front end. of the drum constitutes an initial mixing zone to which the dry material is advanced by the end to end mixing action, but to.insure movement of the wet material back to the open end of the drum, it is another object of this invention to provide means for positively lifting the wet material out of the wet initial mixing zone to the surface of the mass where it is progressed rearwardly to the open end of the drum by the end to end mixing action. It is obviously desirable to introduce the water through the charging opening as this eliminates the necessity of having the water line pass through the bearing at the closed end of the drum.

Consequently, this invention proposes an improved manner of introducing the water into the drum through its open rear end and discharging it at the closed front end of the drum at a point beneath the level to which the drum is normally charged.

In instances where the mixing is done in transit, and the water is introduced into the drum before the other aggregates or at least before the cement it is desirable to eliminate all water lines from the interior of the drum.

To this end, the present invention has, as another of its objects, the provision of an improved water injection line which is readily removable so that the mixer can be. quickly adapted for this type of transit mixing.

Another object of this invention resides in the provision of simple, practical valve means for precluding the entrance of concrete and concrete mix into the interior of the water injection line.

Still another object of this invention is to provide a practical efficient manner of connecting the water injection line, which is located inside the drum, with a supply pipe in such a manner ao as to permit relative rotation therebetween.

In this type of mixer wherein charging and discharging is effected through the same end of the drum, spiral blades are provided within the drum to convey the material back and forth for .I5 mixing upon rotation of the drum in one direction; and to carry the material out through the discharge opening upon rotation of the drum in the opposite direction.

In a broad sense, the use of spiral blades for this purpose is not new; but this invention contemplates certain improvements in this respect by which a more efficient mixing action is obtained and a more rapid and complete discharge effected.

To this end, the present invention has, as another of its objects, the provision of blades which vary in height in direct proportion to the changing diameter of the drum so that the blade has maximum height where the mass has greatest 80 depth.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as 85 hereinafter described, and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed in accordance with the best mode so far devised for the practical application of the principles thereof, and in whichFigure 1 is a side view of a truck mixer embodying this invention; Figure 2 is an enlarged longitudinal sectional view through the drum of the mixer and its charging chute, showing the water injection line in place; Figure 3 is a cross sectional view taken through Figure 2 on the plane of the line 3-3; Figure 4 is an enlarged sectional view through the charging and discharging end of the drum and its charging hopper, with the combined charging hopper and sealing door swung partially open; Figure 5 is a perspective view of the water injection pipe per se; Figure 6 is an enlarged longitudinal sectional view through the discharge end of the water Injection pipe; Figure 7 is a cross sectional view taken through Figure 6 on the plane of the line 7-7; Figure 8 is a longitudinal sectional view through 3( the outer or inlet end portion of the water injection pipe; Figure 9 is an end view of the inlet end of the water injection pipe, with parts broken away to illustrate structural details; and Figure 10 is a detail sectional view taken through Figure 8 on the plane of the line 10-10. • Referring now particularly to the accompanying drawings, in which like numerals indicate like 4 parts, the numeral 5 designates a concrete mixer unit which is mounted on the chassis of a truck 6. The mixer unit comprises the usual base 7 from which supporting structure 8 rises to rotatably support the mixing drum 9. In the present instance, a separate engine 10 is provided for driving the mixing drum, suitable clutches (not shown) being provided for connecting the drum with the engine at the will of the operator.

The mixing drum is roughly cone-shaped or 5 more particularly in the shape of a top, and is mounted with its longitudinal axis inclined to the horizontal. The angle at which the axis is inclined is rather steep so as to dispose the open rear end of the drum at a substantial elevation which facilitates discharging the drum contents.

The specific manner in which the drum is rotatably mounted forms no part of this invention; and, therefore, has not been illustrated. It is sufficient to note that no part of the mounting 6 means for the drum enters the interior and that the head or lower front end of the drum which is formed by .a casting 11 is completely closed.

In the open end of the drum is a short truncated cone 12 to divide the open end portion of 6 the drum into an inner charging passage 13 and an outer annular discharge passage 14. This truncated cone is held in spaced relation to the walls of the drum by a plurality of spiral blades or. vanes 15 which extend radially across the dis- 7 charging passage 14.

Preferably, these blades or vanes are welded to the wall of the drum and to the truncated cone and they extend uninterruptedly from the open end of the drum spirally along the inner wall of 7 the drum to its closed inner end where they terminate in scoops or buckets, indicated generally by the numeral 16. These scoops or buckets are formed by curving the inner ends of the blades or vanes, as best illustrated in Figure 3. Their functions will be defined hereinafter.

Another feature of the blades is that they increase in width as they approach the large diameter closed end of the drum. This facilitates the movement of materials by providing greater area for the blades where the mass is greatest in depth.

With this spiral arrangement of the blades, a screw or helix is formed on the inner wall of the drum which works the material toward the closed head end of the drum upon rotation of the drum in one direction, and which conveys the material up along the inclined bottom wall of the drum into and through the discharging passage 14 during rotation of the drum in the opposite direction.

With the drum revolving in the mixing direction, the spiral blades carry the materials in front of them toward the closed end of the drum, as stated. This causes the aggregates to pile up higher at the closed end of the drum than at the open end; and as a consequence, the top of the drum contents slopes downwardly toward the open end of the drum.

As a result, the large aggregates flow or migrate toward the open end of the drum more Sreadily than the fine aggregates, tending to effect objectionable stratification of the aggregates. To overcome this objection, the blades are T-shaped in cross section, with the head 17 of the T disposed substantially parallel with the adjacent wall i of the drum.

The flanges formed by the head of the T projecting from opposite sides of the blades as they do cooperate with the adjacent walls of the drum to define troughs which are better able to hold the materials and insure more efficient mixing and discharging than if the blades had no flanges.

The scoops or buckets 16 formed by the curved inner ends of the blades carry the material which covers the front end wall of the drum up over the top of the drum contents and thus prevent Sstagnation of that part of the drum contents and thereby further improve the mixing action.

Without these scoops or buckets, the aggregates covering the front end of the drum would be left o undisturbed, a condition which would not only prevent admixture of such aggregates with the remainder of the drum contents but would also interfere to some extent with proper mixing as it would retard the desired movement of mate5 rials Which may be defined as an end to end circulation with the surface materials moving rearwardly and the under portions moving forwardly.

As the scoops or buckets carry the material covering the front end wall up and around with O the drum, the material folds over and flows diagonally across the top of the drum contents toward the charging opening to pour over the top of the blades into the spaces behind them.

In discharging the drum, which, as stated, is 5 effected by reversing its direction of rotation, the blades continuously pass through the bottom of the mixed concrete and convey it upwardly along the inclined bottom wall of the drum to pour out through the discharging opening 14.

0 As the concrete slides along the blades, it tends to slide off the edges of the blades which, if permitted, would result in segregation during discharge. The flanges formed by the head of the T reduce this tendency to a minimum; and by 5 forming the troughs, as noted hereinbefore, insure that the concrete will slide freely through the discharge opening and into the chute or other receiving structure.

The charging of the drum, as stated hereinbefore, is effected through the truncated cone 6 12 which provides the charging opening 13. To this end, a combined feed chute and sealing door, indicated generally by the numeral 18, is provided. This unit is hinged as at 19 from the supporting structure to swing from its closed position illustrated in Figure 2 to open position shown in Figure 4.

The specific construction of this unit and the .manner of swinging the same from one position to the other form the subject matter of the copending application of Harry C. Peters and Harold E. Smith, Serial No. 290,110, filed August 14, 1939.

As defined more at length in said copending application, the combined feed chute and sealing door has a water passage 20 built therein which is connected with a force pump (not shown) by which water is pumped from a supply tank 21 through suitable piping into the passage 20 for injection into the mixing drum. If the mixing is to be done in transit, the required amount of water is discharged into the drum before the dry aggregates or during the charging of the sand and gravel. This can be done by merely pouring the water down the same feed chute through which the dry aggregates enter the drum, or it can be effected through the water passage 20.

During such transit mixing, water introduction presents no serious problem as the cement is introduced last; but where it is desired that the mixing be done at the delivery point or at location, difficulties are encountered. When this latter method is practiced, the volume of dry aggregates in the drum, when the mixer is charged with a batch of the full rated capacity allowed by the National Ready Mixed Concrete Association, is so great that a stream of water introduced at the open end of the drum cannot reach the closed head end which is covered by dry aggregates.

Inasmuch as proper mixing in a drum of this kind (loaded dry) necessitates the establishment of a wet initial mixing zone beneath the surface of the drum contents and adjacent to the closed end of the drum and end to end circulation of the materials to and from said zone, it is apparent that the water must be introduced in a manner which will insure its reaching the bottom of the mass and the closed head end of the drum and the blading must be designed to effect such circulation. This, however, has not been appreciated before and as a consequence the location of the point of water discharge into the drum received little attention. \ 00 It has now been found that unless the water is discharged into the drum adjacent to its closed front end wall so as to soak the material covering the same and thus form a very wet highly liquid initial mixing zone and the material is quickly moved from this zone upwardly and rearwardly while the lower drier material is advanced to the wet zone, proper mixing cannot be obtained.

In other words, in instances when the drum is loaded dry and the mixing is done at location or if desired, during transit after dry loading, the establishment of a wet zone at one end of the drum and a continuous circulation of material to and from that zone must be maintained while the water is being injected to rapidly disperse the water throughout the mass if the quality of the mix is not to be impaired and the mixing action objectionably prolonged.

To establish the wet initial mixing zone at the desired location, a water supply line or pipe 22 is provided. This pipe is located axially of the drum and extends from the open rear end to a point closely adjacent to the closed head end of the drum. At its forward end the pipe has a discharge nozzle 23, to be hereinafter described and from which the water issues to impinge the closed end of the drum; and at its rear end, the pipe carries a swivel head 24 by which it is connectible to the spout of a supply pipe'25 which leads from the water passage 20 and constitutes a part of the combined feed chute and sealing door unit.

The pipe 22 is removably held in place by two collars 26 and 26' supported centrally by spokes 27 and 27' and in which conical flanges 28 and 28' fixed to the pipe are seated. A latch 29 engaging over the flange 28' holds the unit in place in a manner permitting ready removal. Such removal of the water line is desirable for the reason that when the truck is being-used for transit mixing, it is best to have the interior of the drum unobstructed.

The discharge nozzle 23 comprises a plate seated in a counter-bore 31 and provided with a plurality of circumferentially arranged holes 32.

Overlying the outer face of this plate is a washer 33 of rubber or other suitable flexible material, which is held in place by a snap ring 34 bearing against a metal washer 35.

In this manner ingress of concrete and aggregates into the pipe is precluded without interfering with the discharge of the water as the rubber washer yields to the pressure of the water within the pipe.

To form the several streams issuing from the individual holes 32 into one solid stream and thereby insure its striking the center of the front end wall, a lug 36 projects from the central portion of the plate into the hole 37 of the rubber washer.

The swivel head 24 by which the inlet end of the pipe is connected to the supply pipe 25 in a manner permitting rotation of the pipe 22 consists of a sleeve-like casting 38 rotatably fitted to the end of the pipe 22 and held against removal by cap screws 39, the ends of which project into an annular groove 40 in the pipe 22.

A flange 41 is formed on the outer end of the casting 38 and to which a rubber valve unit 42 is attached, preferably by having the valve unit provided with an inner flange 43 which engages over the flange 41. This rubber valve unit 42 has a plurality of radial slits 44, the outer edges of which are preferably beveled, as at 45. Normally, the resilience of the valve unit keeps these slits closed, to be opened by the nozzle \46 of the supply pipe 25 as it is swung into operative position.

The supply pipe 25 also carries a flarge 47 which engages flatly against the face of th- valve unit to frictionally grip the valve unit and consequently hold the entire swivel head azainst rotation.

Slippage between the casting 38 and the rubber valve unit is prevented by radial ribs 48 projecting from the inner face of the valve unit and seated in appropriate radial grooves in the face of the flange 41.

In this manner, a substantially leak-proof con-.

I - - I nection is afforded between the swivel head and the pipe 25. Any leakage which occurs between the casting 38 and the pipe 22 has the advantage of keeping the joint between the casting and the pipe 22 clean to insure free relative rotation between these parts.

The water issuing from the nozzle 23 and striking the closed front end of the drum forms the desired initial wet mixing zone at the innermost portion of the drum to which access of water has always been difficult in the past. During the water injection the buckets or scoops 16 in revolving around the nozzle 23 lift the wet soupy material to the surface of the drum contents where the end to end mixing action produced by the spiral blades carries it rearwardly to the extreme opposite open end of the drum while drier materials are moved forwardly along the bottom of the drum to the wet initial mixing zone. In this manner, the water is rapidly dispersed throughout the contents of the drum during its injection and, the total mixing time reduced to a minimum.

From the foregoing description taken in connection with the accompanying drawings, it will be apparent to those skilled in the art that this invention provides a substantial improvement in concrete mixers of the transit type.

What I claim as my invention is: 1. In a concrete mixer: a rotatable mixing drum having one end open to permit charging and discharging of the drum therethrough and having an imperforate wall closing its other end; a water supply tube wholly within the drum extending axially from the open end of the drum to a point adjacent to but spaced from the opposite closed end thereof; a discharge nozzle for the tube at said opposite closed end of the drum; means detachably connecting said tube with the drum so that the tube rotates with the drum, said means holding the tube with its discharge nozzle so positioned with relation to said imperforate end wall that water issuing from the nozzle will pass through any material between the nozzle and said imperforate end wall of the drum to impinge the center of the imperforate end wall; and nonrotatable means connectible with the tube at the open end of the drum for supplying water thereto.

2. In a concrete mixer: a rotatable mixing drum having one open end and its other end closed by an end wall; a water injection tube within said drum with is discharge end closely adjacent to but spaced slightly from said end wall of the drum and its inlet end adjacent to the open end of the drum; means connecting the tube with the drum so that the tube turns therewith; a normally closed discharge nozzle at the discharge end of the tube for forcefully directing water against the end wall of the drum, said nozzle being adapted to be opened by the pressure of water within the tube; means movable toward and from a charging position with respect to the open end of the drum for charging the same, said charging means including a water supply duct movable therewith; and means for establishing a substantially leak-proof- swivel connection between the inlet of the tube and the water supply duct upon movement of the charging means to charging position so that water may be discharged into the drum through said tube while the drum is loaded and revolving.

3. In a concrete mixer of the transit type: a rotatable mixing drum having one end open and its other end imperforate; a water discharge tube extending longitudinally along the interior of the drum from the open end thereof and with its discharge end adjacent to but spaced from the imperforate end of the drum; means supporting the discharge tube from the drum so that the tube turns with the drum; a water supply tube mounted for movement to and from an operative water injecting position at the open end of the drum and aligning with the outer end of said discharge tube in its operative position for conducting water to said discharge tube; and a readily separable swivel connection between the outer end of the discharge tube and said movable water supply tube established automatically upon motion of the water supply tube to its operative water injecting position.

4. In a concrete mixer of the transit type: a rotatable mixing drum open at its rear end and closed at its front end; a water supply tube extending from the open rear end of the drum to a point adjacent to its closed front end; a normally closed discharge nozzle at said latter end of the tube adapted to be opened by the force of water under pressure within the tube; means supporting the tube from the drum so that the tube rotates with the drum; a combined drum charging and closing unit movably mounted at 30 the open end of the drum to be swung from a closed charging and transit position to an open discharging position; a water introduction member carried by said unit so as to move therewith to and from a position with its outlet adjacent to and in line with the adjacent end of the tube; and readily separable coupling means for connecting said water introduction member to the adjacent end of said water supply tube.

5. In a concrete mixer: a drum having an open 4end; a water supply tube entirely within the drum and rotatable therewith, said tube having an outer end portion adjacent to the open end of the drum and an inner end portion terminating adjacent to the end of the drum opposite its open end; a charging unit movable to and from operative position in juxtaposition to the open end of the drum and including a water injection tube movable therewith, said water injection tube having an end portion adapted to be aligned with -5 the drum carried tube; a swivel head on the outer end of said drum carried tube; a flange on the water injection tube; and friction means between the swivel head and said flange when the water injection tube is in charging position for holding the swivel head against turning and for sealing the connection therebetween.

6. In a concrete mixer: a drum having an open end; a water supply tube entirely within the drum and rotatable therewith, said tube having an outer end portion adjacent to the open end 10 of the drum and an inner end portion terminating adjacent to the end of the drum opposite its open end; a charging unit movable to and from operative position in juxtaposition to the open end of the drum and including a water injection tube, said water injection tube having an end portion adapted to be aligned with the drum carried tube; a swivel head on the outer end of said drum carried tube; a flange on the water injection tube; and friction means between the swivel head and said flange when the water injection tube is in charging position for holding the swivel head against turning and for sealing the connection therebetween, said swivel head embracing the drum carried tube so that water leaking throut . the connection between the swivel head and the drum carried tube keeps said connection clean to insure freedom of rotation of the swivel head with respect to the drum carried tube.

7. In a concrete mixer: a rotatable mixing drum having one end open and its other end imperforate; means for introducing water into the drum comprising, a tube entirely within the drum extending from the open end of the drum 1 and terminating closely adjacent to the imperforate end thereof; and means readily removably supporting the tube in the drum comprising, longitudinally spaced collars having aligned tapered bores large enough to enable the tube to be passed 1 through the collars, spokes supporting said collars within the interior of the drum, and tapered enlargements on the tube wedged in the bores of said collars.

8. A water injection unit for transit type con- 2 crete mixers comprising: an elongated tube adapted to be removably mounted in the drum of the mixer; a discharge nozzle at one end of the tube comprising, a plate having a plurality of holes spaced from the center; an elastic washer overlying the outer face of the plate and normally closing the holes but movable away from othe holes by the pressure of water within the tube; a central projection on the outer face of the plate within the hole of the elastic washer to form the streams issuing from the holes into one solid stream; and a swivel head at the opposite end of the tube by which the tube may be connected with a water injection tube while allowing the tube to rotate on its axis.

9. A water injection unit for transit type concrete mixers comprising: an elongated tube adapted to be removably mounted in the drum of the mixer; a discharge nozzle at one end of the tube comprising, a plate having a plurality of holes spaced from the center; an elastic washer overlying the outer face of the plate and normally closing the holes but movable away from the holes by the pressure of water within the tube; a central projection on the outer face of the plate within the hole of the elastic washer to form the streams issuing from the holes into one solid stream; a swivel head at the opposite end of the tube by which the tube may be connected with a water injection tube while allowing the tube to rotate on its axis; and an elastic seal for normally closing the inlet to the swivel head, said seal being adapted to be opened upon connection cooperatively of said tube with said water injection tube.

10. In a concrete mixer: a mixing drum having one end open and its other end closed by an end wall; means mounting the drum for rotation on an inclined axis with its open end uppermost and its closed end lowermost so that materials in the drum substantially cover said end wall at the closed end of the drum; mixing and conveying blades on the side walls of the drum; scoops on the end wall of the drum for lifting portions of the drum contents contacting said end wall to the surface of the drum contents and cooperating with said mixing blades to establish an end to end mixing action; and a water injection pipe entering the drum and having its discharge closely adjacent to the closed end of the drum centrally of said scoops for discharging water into the body of the materials covering said end wall of the drum beneath the top surface of said materials so that the material handled by the scoops is highly liquid.

11. In a concrete mixer: a mixing drum rotatable on an inclined axis and having an opening at its upper raised end through which the drum is charged and discharged, the lower end of the drum being closed by an imperforate end wall; a water injection nozzle mounted adjacent to the open end of the drum for motion to and from a predetermined position at which the discharge end of the nozzle directs water into the open end 0 of the drum; and a tubular extension for said nozzle mounted inside the drum axially thereof and having its inlet directly adjacent to the discharge end of the nozzle to receive water therefrom when the nozzle is in said predetermined position, said extension having its discharge end terminating closely adjacent to but spaced slightly from the closed end of the drum so as to be completely embedded in the drum contents covering said imperforate end wall of the drum. 0 12. In a concrete mixer: a rotatable mixing drum closed at one end arid open at its other end; means for introducing water into the drum, said means discharging the water towards said closed end of the drum and at a point beneath ,5 the surface of the drum contents and sufficiently close to said closed end to insure water issuing therefrom penetrating through material between said means and the closed end of the drum so as to form a wet zone at the closed end of the 30 drum extending below the surface of the drum contents; and means for effecting circulation of aggregates within the drum to and from said wet zone.

13. In a concrete mixer: a rotatable mixing 35 drum having a single opening through which the drum is charged and discharged; means for introducing water into the drum, said means having its discharge mouth close enough to a wall of the drum remote from the charging and-dis40 charging opening to insure water issuing therefrom reaching said wall, although the drum is loaded with dry aggregates, to form a wet zone directly adjacent to said wall; and mixing and conveying means for continuously moving wet 45 material from said zone and for bringing drier aggregates to said wet zone during the water injection to rapidly disperse water throughout the mass of aggregates and to continue the mixing action and complete dispersion of the water 50 through the aggregates after completion of the water injection.

14. In a concrete mixer: a rotatable mixing drum closed at one end and open at its other end to provide a single charging and discharging 55 opening through which the drum may be loaded with aggregates to a predetermined level; means rotatably mounting the drum with its axis so positioned that the closed end wall and the side wall form the bottom of the drum; a water sup60 ply pipe entering the drum and having its discharge directly adjacent to the closed end wall of the drum and beneath the surface of aggregates within the drum to define a wet zone at said closed end wall of the drum; and means for con65 tinuously moving wet material from said zone upwardly to the surface of the aggregates in the drum and for moving drier material along the side wall of the drum to said wet zone to quickly disperse the water through the mass of 70 aggregates while the water is being injected and to thereafter complete the mixing action, said last named means comprising spiral mixing and discharging blades. on the side wall of the drum so pitched as to move materials toward the closed 75 end of the drum during rotation of the drum in one direction, and scoops at the inner ends of the spiral blades and on said end wall to revolve around the axis of the drum within the wet zone and continuously lift the wet material to the surface of the drum contents.

15. In a concrete mixer: a rotatable mixing drum having an open end through which the drum is charged and discharged and having its opposite end closed by an imperforate end wall; means for effecting an end to end mixing action with the drum contents moving in a continuous stream toward and across said imperforate end wall, said means comprising spiral blades on the sides of the drum for advancing the lower strata of the drum contents from the open end of the drum to said imperforate end wall upon rotation of the drum in a mixing direction and for conveying the drum contents toward the open end of the drum to discharge the same upon drum rotation in the opposite direction, and blade means acting on the material brought to the imperforate end wall by the spiral blades for positively moving said material across said imperforate wall to the top surface of the drum contents for circulation back toward the open end of the drum; and means for introducing water into the drum contents wholly beneath the top surface thereof having a discharge nozzle directed toward, and close enough to said imperforate end wall to insure water issuing therefrom passing through materials between the nozzle and said imperforate end wall to impinge said imperforate wall and preclude accumulation-of materials thereon.

16. In a concrete mixer: a mixing drum mounted for rotation on an inclined axis and having its raised end open -and its lower end closed by an imperforate end wall substantially normal to the axis of rotation of the drum; apiral blades on the sides of the drum for moving materials 4 along the side wall of the drum from the open end thereof to said end wall during rotation of the drum in one direction and for discharging the drum contents duiing drum rotation in the opposite direction; means on said end wall for 4 receiving material conducted thereto by the spiral blades and for positively working the material laterally across said end wall to the top surface of the drum contents for gravitational movement in an upper surface strata back to- 6 ward the open end of the drum; and means for introducing water into the drum contents under pressure and wholly beneath the top surface of the drum contents including a water discharge nozzle substantially axially of the drum and directed toward and spaced from said imperforate end wall a distance such that at the available pressure water issuing therefrom passes through material between the nozzle and said end wall to impinge the end wallh 6 17. In a truck mixer of the type for transporting dry aggregates to and mixing the same at location: a drum rotatably mounted on the chassis of the truck, said drum having its rear end open to enable charging and discharging of 6C the drum at the rear of the truck; a charging unit movable from a charging position at which it is operable to direct aggregates into the drum to a position removed from said open end of the drum to permit discharging of the drum con- 7( tents; water supply means carried by the truck including a water passage on the charging unit so as to be movable therewith, the mouth of said passage being accessible from the open end of the drum; and means inside the drum for con- 75 ducting water from the mouth of said water passage to a point under the surface of the drum contents near a wall of the drum which is covered by its contents during the mixing action, said means being carried by the drum to revolve therewith and being automatically .connectible with the mouth of said water passage upon movement of the charging unit to its charging position.

18. In a truck mixer of the type for transporting dry aggregates to and mixing the same at location: a drum rotatably mounted on the chassis of the truck, said drum having its rear end open to enable charging and discharging of the drum at the rear of the truck; a charging unit movable from a charging position at which it is operable to direct aggregates into the drum to a position removed from said open end of the drum to permit discharging of the drum contents; water supply means carried by the truck including a water passage on the charging unit so as to be movable therewith, the mouth of said passage being accessible from the open end of the drum; means inside the drum for conducting 2, water from the mouth of said water passage to a point under the surface of the drum contents _jear a wall of the drum which is covered by its c--cntents during the mixing action, said means comprising a tube having an inlet end and a o discharge nozzle; and means for removably mounting the tube inside the drum with its inlet end positioned to automatically connect with the mouth of said water passage upon movement of the charging unit to its charging position ;3 and its discharge nozzle positioned to discharge water into the drum contents beneath the surface thereof and adjacent to a wall of the drum covered by its contents during the mixing action.

0O 19. In a truck mixer of the type for transporting dry aggregates to and mixing the same at location: a drum rotatably mounted on the chassis of the truck, said drum having its front end closed and its rear end open to enable diss5 charging of the drum at .the rear of the truck; water supply means carried by the truck for introducing water into the drum under pressure, said supply means including a water passage leading to the interior of the drum and a nozzle 0 inside the drum for receiving water from said water passage, said nozzle being directed towards and having its mouth close enough to the end wall at the closed front end of the drum to insure water issuing therefrom reaching said end 5 wall to form a wet zone thereat although the drum is loaded with dry aggregates; and means for effecting circulation of aggregates within the drum to and from said wet zone.

20. In a truck mixer of the type for trans0 porting dry aggregates to and mixing the same at location: a mixing drum mounted on the chassis of the truck for rotation on an inclined axis, said drum having its front end lowermost and closed, and its rear raised end open to en5 able discharging of the drum at the rear of the truck; water supply means carried by the truck for introducing water into the drum under pressure, said supply means including a water passage leading to the interior of the drum and ) opening thereto at a point close enough to the closed lower end of the drum to insure contact of water with the wall surfaces at said closed end Sof the drum beneath the surface of the drum contents so as to form a wet zone at the closed lower end of the drum; and mixing and conveying means in the drum for effecting circulation of the drum contents toward and from said wet zone.

21. In a concrete mixer: a mixing drum mounted for rotation on an inclined axis and having its lower end closed, and its raised end open for discharging the drum through said raised end; means for introducing water under pressure into the lower end of the drum while the drum is charged with dry aggregates, and close enough to the closed end of the drum to insure contact of water with the wall surfaces at said closed end of the drum beneath the surface of the drum contents so as to form a wet zone at the closed lower end of the drum; and means in the drum for effecting circulation of the drum contents toward and from said wet zone.

22. In a concrete mixer: a rotatable mixing drum closed at one end and open at the other end and adapted to be charged with aggregates to a predetermined level covering the closed end of the drum; means for discharging water in the drum toward said closed end of the drum and at a point wholly beneath the surface of the drum contents and sufficiently close to said closed end to insure water issuing from said means penetrating through material between said means and the closed end of the drum to impinge said closed end and define a wet zone at that portion of the closed end of the drum which is covered with aggregates.

23. In a concrete mixer: a rotatable mixing drum open at one end and closed at the other; said drum being of the type adapted to be discharged through its open end upon rotation of the drum in one direction; means mounting the drum for rotation with its axis inclined and its open end at a higher elevation than its closed end so that aggregates in the drum congregate in the closed end; means for introducing water into a mass of aggregates congregated in the closed end of the drum comprising a conduit extending from exteriorly of the drum into the interior thereof and discharging toward the end wall at the closed end of the drum at a point beneath the surface of the drum contents and close enough to said end wall to insure the wetting of the aggregates covering the closed end of the drum; and a water pump connected with said conduit exteriorly of the drum for supplying water thereto under pressure.

HARRY C. PETERS.