US3446487A - Concrete mixers - Google Patents

Description

R. W. STREHLOW CONCRETE MIXERS May 27,1969

Sheet Filed Nov. 21, 1967 INVENTOR ROBERT w. STREHLOW ATTORNEY May 27, 1969 R. w. STREHLOW CONCRETE MIXERS Sheet Filed Nov. 21. 1967 IN v E N TOR ROBERT w. STREHLOW vA T TORNEY R. W. STREHLOW CONCRETE MIXERS May 27, 1969 Sheet Filed'Nov. 21, 1967 INVENTOR ROBERT w. STREHLOW AT TOR-N E v United States Patent 3,446,487 CONCRETE MIXERS Robert W. Strehlow, New Berlin, Wis., assignor to Rex Chainbelt Inc., Milwaukee, Wis., a corporation of Wisconsin Filed Nov. 21, 1967, Ser. No. 684,797 Int. Cl. B28c 5/20, 7/16 US. Cl. 259-161 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to concrete mixers, and is particularly adapted to the types which are used at the batching plant where the concrete ingredients are weighed and assembled. After mixing, the concrete is hauled to its point of use, preferably in a receptacle which has provision for agitating the concrete so to avoid segregation during the period between the mixing and placing of the concrete.

The object of the invention is the provision of a mixer which alone or in combination with another mixer can mix in shorter time and in a more thorough manner than mixers heretofore used.

The horizontal mixer of this invention lends itself to use with a conventional tilting type mixer so that the materials are partially mixed in the new mixer and then after transfer to the conventional mixer, the entire, batch is mixed more thoroughly and complete mixing is obtained more rapidly than in previous combinations of two compartment mixers.

The mixer drum rotates about a horizontal axis with a charging opening at one end and a discharge opening at the other end. The drum at the charging end is frustoconical, whereas the rest of it, including the discharge portion is cylindrical, the shell portion being concentric with the axis of rotation. In this drum and integral therewith are spiral blades extending from the charging opening to a spaced distance from the head at the discharge end. In this space, axial lifting or discharge blades are equally spaced circumferentially of the drum. These blades, which are also attached to the drum wall are radial to and extend inwardly toward the axis of rotation, their radial dimension being roughly of the order of one-half the distance radially from the drum opening to the maximum diameter of the drum.

In one of its aspects, the invention resides in the provision of a stationary sealing plate or barrier on one side of the drum only which eflfectively retains all concrete on the discharge blades until the blades are tilted in the range of forty-five degrees to the horizontal. Integral with the barrier is a gate and discharge chute, the gate being tiltable between two positions. In one position, it receives the concrete from the blades and directs it to the chute, and in the other position, it prevents discharge from the drum and directs the concrete toward the center of the drum. The drum is rotated at a speed so that in view of the size of the discharge opening and the location of the barrier, more concrete is elevated to the hopper than can pass through the opening, the suiplus being free to fall ofl? the blades as they descend on the opposite side of the opening. The quantity of concrete passing over the hopper is of the same order as the amount discharged through the opening. As a result, a large mass of concrete is maintained below the drum opening augmented by the partially mixed material which is being moved from the charging opening by the spiral blades previously mentioned.

There is no obstruction between the portion of the drum in which the spiral blades are operative and the balance of the drum in which the discharge blades are located. Consequently the spiral blades keep heaping material over the tops of the discharge blades so that the spaces or pockets between adjoining discharge blades beneath the barrier and the drum opening are constantly full of concrete. Furthermore, when the gate is closed during the mixing operation, and concrete is being directed by the gate toward the charging opening, it can chute off the end of the gate unobstructedly into the portion of the drum in which the spiral blades operate.

As previously mentioned, the drum is especially designed for serving as a pre-mixer for a conventional type tilting mixer. In this instance, when the gate is in discharge position, only a portion of the material lifted by the discharge blades is discharged. The other portion is divided and stays in the first drum until eventually all material is discharged into the second drum. This continuous division at the discharge point enables more adequate mixing of the divided portions, so that when they are recombined, they can be more evenly mixed and the ingredients, i.e. the sand, cement, Water and aggregates will be more uniformly dispersed throughout the entire mix.

When the gate is closed, the division continues, with some material being diverted by the gate and the balance continuing to pass over the top of the gate the same as it does when the gate is opened. The two divided portions of the batch are then recombined with the remaining ingredients as the drum continues to revolve, and it complete mixing is desired in this drum, it can be done in an improved and more efficient manner.

The invention is illustrated in the accompanying drawings, in which:

FIGURE 1 is a side elevation of certain elements of a portable batching plant including the horizontal axis mixing drum and a tilting type, double-cone mixer, with the latter arranged to receive partially mixed concrete from the former;

FIG. 2 is an enlarged side elevation of the horizontal axis drum with parts of the drum and the guide cover broken away;

FIG. 3 is a section taken on the line 33 of FIG. 2; and

FIG. 4 is a detail view, partly in section, of a portion of FIG. 2 showing the rubber seal assembly and rollers on the discharge end of the horizontal mixer.

Referring to FIGURE 1, which shows certain portions of a concrete mixing plant, the mixing drum 11 is of the well-known, double-cone, tilting type, which does its mix ing when its axis of rotation is in a horizontal position. This drum has a charging opening 12 surrounded by a conical portion at one end and a discharge opening 13 surrounded by another conical portion at the other end, and the ring gear 14 is arranged to be driven by a pair of gear head motors one on each side of the drum.

When the drum '11 is tilted about the pivot 15, to the dotted line position, the mixed concrete pours out the discharge opening 13 into either a truck mixer or some form of hauling body (not shown). There must be sufficient clearance beneath the mixer when tilted for the truck to pass and for the receiving body or hopper of the truck mixer to be located. An example of the tilting type mixer is described in greater detail in US. Patent 2,590,438 issued Mar. 25, 1952, and need not be elaborated on in this description. It should be pointed out that the charging opening 12 is provided with a cone extension 16 which extends a slight distance axially from the closed head 17 surrounding the opening 12. The mixer 11 is supported by a suitable stand or foundation 18 which determines its elevation.

Spaced from the stand 18 is a somewhat similar stand 19 which supports the cement batcher 20 and other machinery as hereafter described. The cement batcher is arranged to weigh the prescribed quantity of cement which is supplied to it from an overhead bin, an adjacent silo or other means of cement supply. The weight of material in the batcher is recorded by the scales 2 1 which can be utilized to cut off the supply of cement when a predetermined weight is in the batcher.

Supplying aggregates to a point adjacent to the discharge of the cement batcher is the sloping belt conyeyor 22', the head pulley 23 of which is driven by chain 24 connected to the motor and speed reducer designated 25. It will be understood that the aggregates are separately weighed in batchers over a lower portion of the belt (not shown) and that they may be fed simultaneously with the cement through the chute 26 that is arranged beneath the cement batcher and over the end of the belt conveyor. A suitable scraper may be provided adjacent the belt as it passes over the head pulley to direct material into the chute 26.

Disposed between the two stands 18 and .1-9 and like- 'wise supported by them is the horizontal mixer 27, which receives the raw ingredients through its charging opening 28 from the chute 26, and then in turn discharges the partially mixed concrete into the tilting mixer 11, previously described.

The mixer 27 is mounted on a chassis 29 which is provided with wheels 30 permitting the mixer to be towed when the plant is being transported from one location to another, as in highway paving. Power for rotating the mixer drum is derived from two electric motors 31, one on each side of the drum. As illustrated in FIG. 2, motor 31 drives the counter shaft 332 through the chain 33 and sprockets 34. At the charging end of the drum and surrounding the conical section 35 are a pair of sprockets 36. One sprocket is driven by the chain 37 which engages the sprocket 37' on one of the counter shafts 32, while the other sprocket is driven by a chain 38 and sprocket 38', the latter being mounted on the counter shaft on the other side of the drum. The drum is rotated in clockwise direction as indicated by the arrow in FIG. 3 when viewed from the charging end of the drum.

At the discharge end of the drum there is an upright frame structure 39 on which is mounted the discharge chute body generally designated 40, which extends through the opening 40' at the discharge end of the drum. The body 40 is cantilevered on the side of the frame 3 9 and includes within the drum, the stationary sealing plate 48 and the transfer gate 53 along with the mechanism for operating the latter.

Extending through the drum opening 40 and as a part of the body 40 is a downwardly inclined duct or chute 41, the lower portion 42 of which is stationary and is surrounded by a flange or collar 43 which lies just outside the head of the rotating drum. The flange 43 is bolted or otherwise secured to the upright frame 39. A cylindrical portion 44 extends inwardly from the flange 43 through the drum opening and carries the assembly for retarding discharge and then for selectively causing or preventing such discharge while dividing the concrete brought to the discharge opening.

The guide cover 45 consists of two spaced end mem bers 46 and 47, one of which 46 lies generally parallel to and closely adjacent and alongside the inner side of the head of the drum. It is the inner member 46 which is secured to the inner end of the cylinder 44. The members 46 and 47 extend above the top of the drum opening and being open at the top and bottom define the front and back of a hopper for the material to pass as hereafter described.

On one side of the drum opening, the end members 46 and 47 extend below the opening and are enclosed by a sealing plate or barrier 48, the outer surface of which is cylindrical and concentric with the axial drum opening. The width of this wrapper 48 is substantially the same as the length of the discharge blades 62 mounted on the drum wall, the inner portions of which pass in close proximity to the outer surface of the wrapper as the drum is revolved.

Extending downwardly from the upper end of the cylindrical portion of the wrapper 48 is an inclined throat portion 49 which connects with the vertical portion 50 which is set acutely to the carrying surface of the blade side of the opening, opposite throat portion 51 merges with the vertical portion 52 defining the opposite side of the hopper. Chute portion 42 merges with the side portions 50 and 52 and forms the bottom portion of the hopper and directs material through the opening.

At the upper edge of the stationary portion 42 of the chute is a flop gate 53 which can be swung from one position in which it directs material passing through the hopper out the opening, to another position 53 where it closes the opening and directs material back into the drum. The gate 53 is pivotally mounted in bearings 54 which permit the gate to flop about a horizontal axis slightly above the axis of the drum.

The gate 53 is actuated by a pair of hydraulic cylinders 55 extending through the drum opening on either side of the chute 42. The inner ends of the pistons 55 operating in the cylinders are connected to lever arms 56 which are keyed to the flop gate trunnions 57 journalled in the bearings 54.

When the cylinders are extended, the upper edge of the gate 53 is adjacent to the end member 47 of the guide cover, and in this position it serves as an extension of the stationary portion of the chute 42. When the upper edge is pivoted so as to be in the dotted line position 53' adjacent the member 46 which lies next to the drum head, the gate blocks the passageway through the drum opening and directs material back into the center of the drum. To facilitate the latter action, there is a stationary baflle or deflector 58 which lies below the bearings 54 and forms an extension of the gate when the gate is blocking the passageway. The lower end of the battle 58 is in substantially the same plane as the end member 47 and since it is a goodly distance above the bottom of the drum, it serves to throw the material Well back into the middle of the drum.

Both of the cylinders 55 are covered and protected from concrete, the cylinder on the side where the sealing plate 48 is located extending into the space formed by the wrapper. A separate cover 59 encloses the other cylinder and lever arm. A removable plate 60 on the end member 47 permits access to one of the bearings 54 while a removable plate 60 on the vertical cover 59 permits access to the other bearing 54.

Surrounding the lower end of the portion of the chute 41, which extends outside the drum is a flange 61. This flange is bolted to a seal (not shown) which engages the cone extension 16 of the tilting mixer 11 when the latter is in horizontal position. Since the axis of the tilter in this position is slightly below the axis of the mixer 27, the tilting mixer when tilting moves away from the chute 41 and no interference results.

The fixed axis horizontal mixer 27 is provided with discharge blades 62 which are equally spaced circumferentially of the drum and which extend radially from the outer wall toward the axis of rotation. These blades extend from the head of the drum which surrounds the discharge opening a distance substantially equal to the length axially of the sealing plate 48. Each blade is supported by triangular brackets 64 bolted or otherwise secured to the drum shell. Each blade also has a lip 65 which is set acutely to the carrying surface of the blade and keeps concrete from falling off the blade in an axial direction of the drum toward the central portion of the drum.

The inner edges of the blades 62 pass in close proximity to the arcuate surface of the sealing plate 48 and the concrete on the blades is retarded from discharge until the blades have passed over the top of plate 49. The concrete then falls between the side plates 49 and 51 and if the gate 53 is in discharge position, the concrete, which is partially mixed, passes through the duct 41 into the tilting mixer 11, where mixing is completed. If the gate is closed the concrete is directed onto the inner chute 58 and thence toward the center of the drum for further mixing.

Regardless of whether the gate 53 is open or closed, the rate of drum rotation, which is of the order of ten to fifteen r.p.m., is such that the amount of concrete which is elevated by the discharge blades 62 is substantially more, and of the order of twice as much, as will pass through the throat formed by sides 49 and 51 and the end members 46 and 47. Consequently the concrete elevated by the discharge blades is divided at this point and the excess concrete passes over the top of this throat and falls off the blades through the unrestricted opposite side of the drum into the space where the blades can again propel it around the sealing plate.

The portion of the drum not occupied by the discharge blades (to the right of these blades as shown in FIG. 2) is provided With slanting blades 66 which cause the material entering from the charging opening 28 to move into the section served by the discharge blades 62. There is no obstruction between these sections of the drum, and the slanting blades cause concrete to be heaped in the portion of the drum beneath the discharge chute body. Such concrete plus the concrete passing over the top of the chute, keeps the pockets between the blades 62 full of concrete and therefore meters the quantity raised to the throat of the hopper.

There are three slanting blades 66 equally spaced around the circumference of the drum and these blades are troughed as is well known in the art. The blades 66 may extend into the conical portion 35 at the charging end of the drum, or separate blades 67 which are similarly sloped may be provided in this section, and they may be offset circumferentially with respect to the blades 66.

To maintain a seal between the cylindrical member 44 and the drums discharge head 63, a groove 68, as best shown in FIG. 4, is provided in the outer surface of the cylinder 44. A rubber seal 69 rides in this groove and in turn is bolted or otherwise secured to the sealing plate 70 which is bolted to the head 63*. The outer diameter of the annular plate 70 is greater than the dimensions of the discharge chute body and this enables assembly of the latter within the drum before the plate is bolted to the head.

The head is secured to the outer end of the ring or drum track 71 and the cylindrical shell 72 also overlaps this ring. The ring rests on, or is cradled between two rollers 73. Rollers 74 hearing against the ends of the ring 71 prevent any endwise movement of the drum. It will be understood a similar construction is employed for supporting and connecting the shell to the ring 75 at the other end of the drum.

A water supply pipe 77 enters a passage 76 in the upper portion of the discharge chute 41. The water supplied thereby flows 'into the tilting mixer 11 and is used to make a'final adjustment in the slump of the concrete. Because of inherent variations in the moisture content of the sand constituting part of the concrete batch, a portion of the batch water is purposely withheld when the horizontal mixer is charged, and as a result the concrete discharged from the horizontal mixer is of slightly lower slump than that required. Before an accurate slump determination can be made, the ingredients of the concrete must be mixed to a suflicient degree of homogeneity. The earliest practicable time to make this determination is immediately after the concrete has been transferred to the tilting mixer. The slump of the concrete in the tilting mixer is then read by the slump meter and the correct amount of water to adjust it as desired is added from the supply pipe 77 and passage 76 as described above.

The foregoing description of the invention and of the manner and process of making and using it sets forth the best mode or modes of carrying out the invention as presently contemplated. The following claim or claims particularly point out and distinctly claim the subject matter which is regarded as the invention.

What is claimed is:

1. In combination with a rotatable drum for mixing concrete having a discharge opening inone end of the drum and discharge blades circumferentially spaced and extending from the side wall of the drum inwardly toward the axis of rotation, a chute sloping downwardly from inside the drum through said opening, an annular, stationary sealing plate arranged within the drum .and on one side of said opening, means for rotating the drum at a speed whereby the blades which travel upwardly past said plate transport substantially more concrete than can be discharged through the chute, the excess concrete being carried over the chute and retained in the drum for further mixing, and a double-cone, tilting type concrete mixer arranged to receive the concrete discharged from said drum, said tilting mixer being adapted to complete the mixing of concrete so received concurrently with the further mixing in and ultimate discharge of concrete from the drum.

2. A rotatable drum for mixing concrete comprising, an annular discharge head at one end of the drum defining a discharge opening; a discharge hopper and chute body assembly inside the drum rat the discharge end thereof, said assembly being fixed to remain stationary with respect to the rotation of the drum by an extension of the chute body portion through the discharge opening; discharge blades attached to the inside surface of the drum at the discharge end thereof for lifting the concrete and discharging it into the discharge hopper and chute body assembly; a guide cover attached to one side of the assembly on the inside of the drum, said guide cover having a semicylindrical outer surface which lies closely adjacent the radially inner edges of the discharge blades and holds the concrete thereon until the blades pass upwardly around the guide cover to the area above the discharge hopper portion of the assembly; and barrier means within the chute body portion at the bottom of the hopper, said means being operable to selectively direct the concrete received by the hopper through the discharge opening or back into the center of the drum for further mixing.

3. A rotatable drum as in claim 2 wherein means are provided to rotate the drum at a speed whereby substantially half of the concrete carried by the discharge blades is discharged into the hopper while the remaining portion 8f the concrete passes over the hopper with the discharge lades.

4. A rotatable drum for mixing concrete comprising, an upright supporting frame; a discharge head defining a discharge opening at one end of the drum; discharge blades circumferentially spaced and attached to the inside surface of the drum adjacent the discharge end thereof, said blades receiving the concrete and lifting it to the area above the discharge opening; a discharge chute body attached to the supporting frame and extending through the discharge opening and into the drum in the area surrounded by the discharge blades; a guide cover comprising, a first end member attached to the chute body on one side of the discharge opening and lying parallel to and closely adjacent the inside of the discharge head, a second end member parallel to the first and spaced therefrom a distance substantially equal to the length of the discharge blades, a semicylindrical sealing plate concentric with the axis of rotation of the drum and attached at its respective edges to the end members, the outer surface of the plate lying adjacent the radially inner edges of the discharge blades as they pass upwardly around one side of the discharge opeinng; dividing means above the discharge opening and formed by an extension of the guide cover end members for receiving a portion of the concrete carried by the discharge blades and directing it into the discharge chute body and allowing the remaining portion to pass thereover.

5. A rotatable drum as in claim 4 wherein the inner portion of the discharge chute body has mounted therein a movable gate which may be selectively positioned whereby the portion of concrete directed into the chute body by the dividing means may be further directed either through the discharge opening or back into the center of the drum for additional mixing.

6. A rotatable drurn as in claim 4 wherein means are provided to rotate the drum at a speed whereby the portion of concrete received by the dividing means is substantially equal to the portion passing over the dividing means.

7. In combination, a rotatable tilting type concrete mixer having conical portions adjacent the openings at each end, a rotatable horizontal mixing drum having a charging opening at one end and a discharge opening at the other end, the latter opening being in juxtaposed relation to the charging opening in the tilting type mixer, means for mixing and transferring concrete longitudinally in the horizontal drum, means for transferring concrete from the horizontal mixing drum to the tilting type mixer, and means for rendering inoperative the last named means during tilting and discharge of the tilting type mixer.

References Cited UNITED STATES PATENTS 1,298,743 4/1919 Lichienberg 259-176 3,241,821 3/1966 Maxon 259--175 X 3,269,707 -8/ 1966 Phillips 259175 X ROBERT W. JENKINS, Primary Examiner.

US. Cl. X.R.

2 3 33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,446,487 Dated May 27, 1969 Inventor(s) ROBERT W. STREHLOW, Assignor to Rex Chainbelt Inc.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

| In the drawings, Sheet 1, Fig. l, the reference numeral 15 should be applied to the pivot of the drum 11 shown in the upper left hand corner of the stand 18. Column 3 line 39, the reference numeral "332" should read -32- Column 4, line 15, cancel "set acutely to the carrying surface of the blade" and insert --tangent to the side of the duct 41. On the opposite--.

SIGNED AND SEALED MAY 5 .1970

(SEAL) Atteat:

Edward M. Fletcher, It.

WILLIAM E. BGHUYIIER, JR- Attoafingofflwr Commissioner of Patents

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