US2088099A - Apparatus for mixing concrete and the like - Google Patents

Description

July 27, 1937. w. M. VENABLE APPARATUS FOR MIXING CONCRETE AND THE LIKE Filed Feb. 11, 1956 5 Sheets-Sheet 1 INVENTOR 414684. Wa dww e/al I July 27, 1937. w. M. VENABLE APPARATUS FOR MIXING CONCRETE AND THE LIKE Filed Feb. 11, 1936 5 Sheets-Sheet 2 INVENTOR July 27, .1937. w. M. VENABLE I 2,088,099

' APPARATUS FOR MIXING CQNCRETE AND THE LIKE Filed Feb. i1. 193a 3 Sheets-Sheet 5 INVENTOR Patented July 27, 1937 APPARATUS FOR MKXHNG CONCRETE AND THE LIKE William Mayo Venable, Pittsburgh, Pa, assignor to Blaw-Knox Company, Elawnox, Pa., a C01? poration of New Jersey Application February 11, 1936, Serial No. 63,371

'7 Claims. (Cl. 83-73) This invention relates generally to a method and apparatus for mixing concrete and the like and more particularly to truck mixers in which the mixing operation is carried out during the transit of the mixer. In this type of mixer particularly, it is important that it be capable of taking as large a charge as possible for a given three-fourths full with unmixed materials which} when mixed, occupy about two-thirds of the drum capacity. The present invention relates particularly to the shape and arrangement of the mixing vanes, whereby a very effective mix-V ing action is obtained, the other parts of the apparatus being conventional.

In accordance with the preferred embodiment of the present invention, a cylindrical mixing drum is employed. It is provided with mixing vanes which are secured to the inside of the drum in such manner that the lines of juncture of the vanes with the drum form an interrupted helix. The ends of the vanes at their proximal edges, that is, the edges which are secured to the drum, are spaced apart so as to provide spaces for portions of the water and concrete to pass therethrough rather than being picked up and carried on the vanes. The ends of adjacent vanes at their distal edges, that is, the edges farthest away from the line of juncture of the vanes with the drum, are secured to each other as by welding in order to provide a rigid structure of vanes. The distal edges of the vanes thus form a continuous though imperfect helix. The faces of the vanes are curved or bent so as to make them trough-shaped in order that they may be capable of picking up those portions of the batch which lie adjacent the drum surface, raising such portions above the main level of the batch and then discharging the portions into the batch at points displaced axially of the drum. The greater part of the concrete is not picked up by the vanes, but rolls or tumbles from one side of the drum to the other, very similar to the action which would take place if an ordinary barrel were filled two-thirds full of material and rolled on its side. The main portion of the batch which rolls upon itself is maintained in relatively the same position longitudinally of the drum. The small portions which are picked up by the vanes are raised above the main level of the batch and there discharged upon the batch at points which are spaced longitudinally of the drum with respect to the places at which such small portions were picked up by the vanes. This causes the concrete to pile up slightly toward the discharge end of the drum which is provided with a cover which may be removed during the discharging operation. Each of the vanes, in addition to being trough-shaped so as to enable it to retain and raise a small portion of the batch above the main batch of concrete, is secured to the drum so that when it is in its uppermost position its edges are inclined downwardly longitudinally of the drum at an angle to the drum axis which is approximately'the angle of repose of the concrete when the vane is in its uppermost position. In other Words, the line of juncture of each vane with the drum, and the distal edge of each vane, each forms an angle with the axis of the drum when the vane is in its uppermost position, which approximately equals the angle of repose of the concrete. This angle is approximately 45, al-

though it Will vary in either direction 10 or 15 degrees according to the consistency and com position of the concrete.

Due to the use of trough-shaped mixing vanes and also because of their arrangement in the drum in the form of an interrupted or broken helix, it is unnecessary to reverse the direction of rotation of the drum at intervals in order to obtain the proper mixing action. In the present invention, efiicient mixing may be obtained by rotating the drum in one direction only so as to cause the concrete to be crowded toward the discharge end of the drum. This is a distinct advantage over those mixers which depend for efiicient mixing on periodically reversing the rotation of the drum. One such mixer which requires the reversing of the drum is described in McCrery Patent No. 1,999,843, granted April 30, 1935, and assigned to the assignee of the present application. In the McCrery patent, because of the use of mixing vanes having fiat faces, the drum must be reversed during mixing and the mixing action is not suificiently effective if it is attempted to use it with a batch which more than half fills the drum. The vanes of the Mo- Crery patent being flat, are not capable of raising small portions of the concrete above the main level of the batch and then discharging them again into the main batch at points which are displaced longitudinally of the drum from the points where such portions were picked up. The elimination of reversing mechanism for the drum and the fact that the drum may be charged more fully and still obtain efiicient mixing action are important advantages of the present invention.

In the accompanying drawings which illustrate two embodiments of my invention,

Figure l is, in part, a side elevation and, in part, a longitudinal vertical section through the mixing drum;

Figure 2 is a transverse vertical section through the drum on the line II-II of Figure 1;

Figure 3 is a view similar to Figure 1 illustrating the drum with a batch therein and showing the action of the mixing vanes;

Figure 4 is a perspective view showing a portion of the mixing drum and certain of the mixing vanes, illustrating the spaces between the proximal edges of adjacent vanes;

Figure 5 is a front elevation of one of the vanes;

Figure 6 is an enlarged transverse vertical section of a vane taken on the line VI-VI of Figure 4 and showing a small section of the drum;

Figure '7 is a view similar to Figure 1, but showing a modified arrangement of vanes in which the proximal edges of the vanes form a continuous though imperfect helix and in which the distal edges of the vanes are spaced apart; and

Figure 8 is a transverse vertical section through the drum of Figure '7 taken on the line VIIIVIII of Figure '7.

Referring now more particularly to the accompanying drawings and for the present to the embodiment shown in Figures 1 through 6, there is shown a mixing drum 2 of conventional form having a cylindrical body portion 3, conical end portions i, a charging opening 6 provided with a cover I and a discharge opening 8 provided with a cover 9. The forward end of the drum is closed by a plate 3a. The drum is provided with means for supporting and rotating it, but such means are not shown since they may be of any suitable kind.

Secured to the inside; of the drum as by welding is a plurality of mixing vanes l5, ll, l2 and I3. These vanes are so arranged as to form an interrupted helix around the drum at the lines of juncture of the vanes with the drum. In the embodiment shown, four of these vanes extend approximately half way around the drum, although a greater or lesser number of vanes may be employed. Also, the number of helixes employed in the drum may be varied. It is preferred, however, to employ two of these helixes, each helix extending half way around the drum. One of the vanes is illustrated in Figure 5. It is bent or curved about its longitudinal axis ab sothat it is trough-shaped in order that it may maintain a small portion of concrete on its surface until the vane is raised to its uppermost position, whereupon this small portion is discharged into the main batch of concrete which has not been lifted by the vanes. The face [5 of the vane l0 illustrated in Figure 5 is concave. The curvature of the vanes is best illustrated in Figure 6 which is an enlarged vertical transverse section through the vane l2 of Figure 4. The vane I2 is secured to the drum by welding as indicated by the reference numeral 16 in Figure 6. The vane is preferably curved so that the plane 0 which is tangent to the curvature of the vane at its distal edge ll makes an angle at of approximately 45 with the vertical plane 6 through the distal edge of the vane.

The proximal edges I8 of the vanes are secured to the inside of the drum by welding 15. The ad jacent ends of the vanes at their proximal edges are spaced from each other, but at their distal edges are welded to each other in order to form a strong structure of vanes. Thus, as shown in Figure 4, the proximal edges iii of vanes i2 and 3 at their adjacent ends E20. and 53a are spaced from each other so as to form a space 1 which is generally triangular in shape, but having curved sides, the bottom side being formed by the curved surface of the drum 2 and the other two sides being formed by the adjacent ends Ma and l3a of the two vanes l2 and 33. This space J allows water to flow therethrough rather than being picked up by the vanes, thereby giving more efficient mixing. The adjacent ends 22a and Ma of the vanes 52 and 53 are welded to-- gether at their distal edges I! as indicated by the reference numeral l9, as are also the other vanes. of the vanes with the drum are not continuous, but are interrupted so that the vanes at their proximal edges formv an interrupted helix rather than a true helix. The distal edges of adjacent vanes meet at the adjacent corners and are welded together so as to form a continuous though imperfect helix.

In carrying out the mixing of a batch of concrete, the drum is filled about three-fourths full and is rotated in a clockwise direction as indicated by the arrow in Figure 2. The greater part of the batch simply rolls or tumbles over upon itself, but small portions of the concrete which lie adjacent the surface of the drum in the path of the vanes are picked up by the vanes, raised above the main batch and thereafter again discharged into the batch at points displaced longitudinally from the points at which they were picked up. In Figures 1 and 3, the vane I9 is shown in its uppermost position. In rising from its lowermost to its uppermost position, the vane IQ, for example, picks up a small portion of concrete, raises it above the surface indicated by the line 20 of the main batch shown in Figure 3 and discharges it again into the batch at a point nearer the discharge end of the drum than the point from which the portion was raised from the batch. The portion being discharged from the vane I53 is indicated in Figure 3 by the reference numeral 9. Each of the vanes acts in a similar manner to raise a small portion of the concrete above the main level of the batch and dump it onto the batch nearer the discharge end of the drum than the point from which it was picked up. While this raising of the small portions above the main level of the batch and dumping it again onto the batch is taking place, the main portion of the batch simply rolls or tumbles on itself. There is thus provided a combined mixing action which is very eflective. The effect of raising small portions of the batch above the main level and again dumping them onto the batch is to raise the level of the concrete toward the discharge end of the drum, as is shown by the line 20. The small portions of concrete discharged onto the main batch by the individual vanes slide by gravity toward the forward end 4a of the drum and are again picked up by the vanes and moved toward the discharge end of the drum. The batch, in addition to being slightly higher at the discharge end of the drum than at the opposite end, is also higher at the far side of the drum than at the near side, as viewed in Figure 3, due to the direction of rotation of the drum. This also causes the small portions of concrete It will be seen that the lines of juncture 5;:

picked up by the individual vanes to move transversely of the drum, thereby causing added'mixing thereof. The concrete below the line 20a of Figure 3 is shown in section, while that above this line is shown in elevation.

Referring now to the embodiment illustrated in Figures 7 and 8, a drum 3B having the same construction as is shown in Figure 1 is provided with a charging opening 3| having a cover 32, the drum also being provided with a discharge opening and cover therefor at its left-hand end, as viewedin Figure '7, this cover, however, not being shown. Vanes 33, 34, 35 and 3e are secured to the inside of the drum as by welding. These vanes, like those described in connection with the other embodiment, are curved or bent along their longitudinal axes so as to make them trough-shaped in order that they may retain the concrete which is picked up by them until such time as the vanes are raised above the main batch of concrete. Thereafter, the small portions of concrete so raised by the individual vanes are discharged again into the main batch of concrete, at points spaced longitudinally of the drum from the points at which they were picked up, as previously described. In this embodiment the proximal edges 3? are welded to the inside of the drum. so as to form a continuous though imperfect helix about the drum. The distal edges 38, however, are spaced from each other at their adjacent ends so as to leave spaces between the adjacent vanes corresponding to the spaces f shown in Figure 4. Referring to Figure 8, the proximal edges 3'! of the vanes 33 and 34, for example, are welded to the inside surface of the drum so as to form a continuous line of juncture with the drum, and such line of juncture forms a continuous although imperfect helix about the inside surface of the drum. The distal edges 38 of the vanes 33 and 34, for example, at their adjacent ends 39 and M are spaced apart, thus leaving spaces through which water and concrete may pass when the vanes are submerged in the batch.

In either embodiment, when water is admitted to the batch, the water finds its'way into the interstices between the stone or gravel or crushed rock, as the case may be, and is distributed in a manner which depends upon the shape of the mixing drum. Upon initiation of rotation of the drum, the water continues to remain in the bottom of the drum as long as there is free space between the stone not occupied by a mixture of sand and cement. This assists in properly distributing the water during the first few rotations of the 'drum and it is desirable that dur ing this period the water should be free to flow wherever it may find space in the interstices of the stone. In the present invention this flow of water is permitted due to the provision of spaces between the adjacent ends of the vanes. If the vanes formed a continuous helix having watertight connections between the adjacent vanes, the vanes would lift the water with the mix, thus preventing the free fiow of water from one side of the drum to the other during the first part of the mixing operation.

In each of the embodiments shown, the mixing vanes are arranged so that there are spaces between the ends of adjacent vanes which allow the water to wet the batch during the early stages of mixing and which during the later stages allow some of the batch to flow through these spaces so as to increase the efficiency of the mixing action.

By arranging the mixing vanes in the form of an interrupted helix, I am enabled to use vanes of a very simple construction. The faces of the vanes are bent or curved into trough-shape so as to retain concrete thereon as the vanes are raised to their highest position. The vanes may be arranged to form an interrupted helix along their proximal edges, as in the embodiment shown in Figures 1 through 6, or they may be arranged to form an interrupted helix along their distal edges, as in the embodiment shown in Figures 7 and 8. In either embodiment, spaces are provided between the ends of adjacent vanes. By arranging the vanes as described, they may be made out of sheet metal and bent in only one direction, namely, about the longitudinal axis of the vane, whereas if the vanes formed an uninterrupted helix, they would have to be curved or bent about their transverse axes in addition. The disposition of the vanes in an interrupted helix, therefore, simplifies the manufacture of the vanes and also increases the efficiency of the mixing action due to the provision of spaces between theends of adjacent vanes.

I have illustrated and described two embodiments of my invention. It is to be understood, however, that the invention may be otherwise embodied within the scope of the following claims. I

I claim:

.1. A truck mixer comprising a normally closed rotary drum with a removable closure and hav-- ing lifting vanes curved in cross-section and having one edge contacting with the drum and adapted to raise portions of the concrete above the level of the main batch and discharge them onto the batch at points which are displaced longitudinally of the drum from the points at which they were picked up by the vanes, said vanes forming an interrupted helix about the drum at their proximal edges, the distal edges of adjacent vanes being connected together adjacent their ends so as to form a continuous though imperfect helix about the drum, the vanes being so inclined with respect to the longitudinal axis of the drum and, so shaped as to retain portions of concrete thereon when they are lifted above the level of the main batch.

2. A truck mixer comprising a normally closed rotary drum with a removable closure and having lifting vanes curved in cross-section and having one edge contacting with the drum and adapted to raise portions of the concrete above the level of the main batch and discharge them onto the batch at points which are displaced longitudinally of the drum from the points at which they were picked up by the vanes forming an interrupted helix about the drum at their proximal edges and providing spaces between adjacent vanes, the. distal edges of adjacent vanes being connected together adjacent their ends so as to form a continuous though imperfect helix about the drum, said vanes being so inclined with respect to the longitudinal axis of the drum and so shaped as to retain portions of concrete thereon when they are lifted above the level of the main batch.

3. A truck mixer comprising a normally closed rotary drum having its length greater than its diameter, said drum being provided with a removable closure, and having lifting vanes curved in cross-section and having one edge contacting with the drum and adapted to raise portions of the concrete above the level of the main batch and discharge them onto the batch at points which are displaced longitudinally of the drum from the points at which they were picked up by the vanes, said vanes forming an interrupted helix about the drum at their proximal edges and providing spaces between adjacent vanes, the distal edges of adjacent vanes being connected together adjacent their ends so as to form a continuous though imperfect helix about the drum, said vanes being so inclined with respect to the longitudinal axis of the drum so shaped as to retain portions of concrete thereon when they are lifted above the level of the main batch.

4. A truck mixer comprising a normally closed rotary drum with a removable closure and having lifting vanes curved in cross-section and having one edge contacting with the drum and adapted to raise portions of the concrete above the level of the main batch and discharge them onto the batch at points which are displaced longitudinally of the drum from the points at which they were picked up by the vanes, said vanes forming an interrupted helix about the drum at their distal edges and providing spaces between adjacent vanes, the proximal edges of adjacent vanes being connected together adjacent their ends so as to form a continuous though imperfect helix about the drum, said vanes being so inclined with respect to the longitudinal axis of the drum and so shaped as to retain portions of concrete thereon when the vanes are lifted above the level of the main batch.

5. A truck mixer comprising a normally closed rotary drum having its length greater than its diameter, said drum being provided with a removable closure, and having lifting vanes curved in cross-section and having one edge contacting with the drum and adapted to raise portions of the concrete above the level of the main batch and discharge them onto the batch at points which are displaced longitudinally of the drum from the points at which they were picked up by the vanes, said vanes forming an interrupted helix about the drum at their distal edges and providing spaces between adjacent vanes, the proximal edges of adjacent vanes being connected together adjacent their ends so as to form a continuous though imperfect helix about the drum, said vanes being so inclined with respect to the longitudinal axis of the drum and so shaped as to retain portions of concrete thereon when the vanes are lifted above the level of the main batch.

6. A truck mixer comprising a normally closed rotary drum with a removable closure and having lifting vanes curved in cross-section and having one edge contacting with the drum and adapted to raise portions of the concrete above the level of the main batch and discharge them onto the batch at points which are displaced longitudinally of the drum from the points at which they were picked up by the vanes, said vanes forming an interrupted helix about the drum at their proximal edges and providing spaces between adjacent vanes, the distal edges of adjacent vanes being connected together adjacent their ends so as to form a continuous though imperfect helix about the drum, said vanes being trough-shaped and so inclined with respect to the longitudinal axis of the drum as to retain portions of concrete thereon when the vanes are lifted above the level of the main batch, said vanes when in their uppermost positions having their edges downwardly inclined longitudinally of the drum at an angle with the axis of the drum approximately equal to the angle of repose of the concrete.

'7. A truck mixer comprising a normally closed rotary drum with a removable closure and having lifting vanes curved in cross-section and having one edge contacting with the drum and adapted to raise portions of the concrete above the level of the main batch and discharge them onto the batch at points which are displaced longitudinally of the drum from the points at Which they were picked up by the vanes, said vanes forming an interrupted helix about the L drum at their proximal edges and providing spaces between adjacent vanes, the distal edges vof adjacent vanes being connected together adjacent their ends so as to form a continuous though imperfect helix about the drum, each of said vanes being made out of a fiat plate bent only about its longitudinal axis and not about its transverse axis, each vane being trough-shaped and so inclined with respect to the longitudinal axis of the drum as to retain a portion of concrete thereon when it is lifted above the level of the main batch.

WILLIAM MAYO VENABLE.

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