US2814474A - Mixing machine for materials such as cement - Google Patents

Description

R. A. ERREN Nov. 26, 1957 MIXING MACHINE FOR MATERIALS SUCH AS CEMENT Filed Juhe 28; 1954 United Sttes MIXING MACHINE FOR MATERIALS SUCH AS CEMENT Rudolf Arnold Erren, Hannover-Liminer, Germany Application June 28, 1954, Serial No. 439,535

1 Claim. (Cl. 259-175) The invention relates to a free-fall rotary, continuously operating mixing machine. Preferably the machine is movable, and is intended particularly, although not exclusively, for preparing concrete and mortar, having a rotating cylindrical or conical drum disposed with its feeding or loading side below funnel like stock hoppers for the feeding of aggregate material, the supply of which may be regulated as desired.

The stock to be mixed which, as usual, is first subjected to intensive dry mixing and is moistened by means of a spray .device only immediately before its emergence from the mixing drum, is continuously conveyed by means of a helical conveyor strip on the interior of the drum casing, between the turns of which conveyor strip are mounted shovel blades parallel or obliquely arranged to the drum shaft.

Mixing machines constructed in this manner are already known, but hitherto since for continuous working in mixing concrete and mortar the known free-fall mixers have not proved equal to the task, use has been made exclusively of forced-feed mixers in which the materials are mixed together in small quantities by a mixing and conveying worm or screw extending right across the casing of the fixed drum, and are then conveyed out of the drum. In mixers of this type the drum casing and the conveyor worm or screw are subjected to extreme wear :and tear, and when relatively coarse materials are being processed there is the danger that large, solid components of the aggregate may become firmly wedged between the conveyor worm or screw and the drum casing. This leads in many cases to damage to the machine parts and necessitates frequent repairs. Forced-feed mixers have the ad ditional disadvantage of needing relatively large driving power as a necessary concomitant of the great frictional resistances of the mixing parts rotating against each other, and the stock mixed between them.

The proposal to use free-fall mixers of the type mentioned above for mixing concrete and mortar in a continuous process, has therefore until now not been followed by a successful practical machine, since it was not possible successfully to mix the additional materials and the binding agent as thoroughly as is absolutely essential for the production of a completely homogeneous concrete or mortar mass which, after further processing, has completely uniform strength throughout. An intensive mixing in free-fall mixers can be obtained, therefore, only if the material on its passage through the rotating drum, the length of which must be kept within acceptable constructional limits, is repeatedly lifted in small quantities and thoroughly shaken together while it is free and in a loose state, so that there can be no blockages of material.

Such blockages of material are unavoidable if, according to another known proposal, the conveying and mixing of the material is performed exclusively by means of stirring surfaces divergently disposed upon the interior of the drum casing. On the other hand, a helically wound conveyor strip extending relatively deeply into the 2,814,474. Patented Nov. 26, 1957 interior of the drum, as provided in another known free fall mixing machine, while giving an eflicient conveyor effect, also prevents the constant falling back of part of the material and thus prejudices the operation of the shovel blades disposed transversely between the turns of the conveyor surface, which shovel surfaces are of less radial height than the conveyor surface.

According to the invention a considerable technical advance in the manner of continuously operating free-fallmixing machines of known type is achieved by constructing the conveyor surface as a flat helical strip with close turns of appreciably less radial height than shovel blades which are disposed between its turns. The flat metal strip, which conveys the stock in small quantities through the mixing drum, in no way hinders a portion of the material raised in the mixing drum by the transverse shovel blades from constantly falling back. Consequently the material is shovelled together many times on its passage through the drum and in this way is subjected to an exceptionally thorough mixing. Thus an essential condition for the use of continuously operating free-fall mixers for mixing concrete and mortar is fulfilled in completely satisfactory manner, .and it becomes possible to use, in continuous operation, free-fall mixers instead of forced-feed mixers, with the consequent advantages of greater reliability in operation, reduction in driving power and cheaper manufacture.

An external roller type of drive may be used for the drum, in which case the drum can be supported upon two rollers and may .be driven by friction or by gear wheels. A preferred method of drive, however, consists in mounting the mixing drum on a shaft running through it and driving this shaft. In this case the spokes connecting the drum to the shaft may, in the manner known in mixing drums with a separate mixing apparatus, be formed as conveyor paddles, so that when the drum rotates they may aid the conveyance of the stock to be mixed.

It may be necessary to regulate, in known manner, the duration of the mixing according to the nature .and moisture content of the materials used, and the drum should be set .at an appropriate angle. A possible method of regulating the speed at which the stock to be mixed is supplied, is by mounting the paddle-like spokes so that their angle is capable of adjustment.

A preferred embodiment of the invention will now be described with reference to the accompanying diagrammatic drawings, in which:

Figure 1 shows, in side elevation and partly in section, a free-fall mixing machine;

Figure 2 is a perspective view, showing also a section on the line A-B of Figure 1, of the mixing drum;

Figure 3 is a fragmentary sectional view of one of the spokes and showing the associated boss, this being on an enlarged scale; and

Figure 4 is a fragmentary side elevation on an enlarged scale of a spoke and associated structure showing the manner of adjusting the boss.

The mixing machine is mounted in a frame 1. On this frame are carried a pair of wheels one of which is shown at 2. For transport purposes a trailer stirrup 3 is affixed to one end of the frame. To set up the machine use may be made of jacking legs 4. A shaft 7 is mounted in bearing blocks 5 and 6 in the frame. The shaft 7 is driven, through a gear 8, by a motor 9. Above the gear are disposed funnel-shaped stock hoppers 10 for the materials. A vibratory feeder 11, operated by the rotation of the shaft, provides, .in conjunction with pu-shers, for a uniform admission of starting materials at the exit open ing of the stock hoppers, the feeder being adjustable.

Behind the stock hoppers the mixing drum 12 is rigidly openings to permit the passage, of the material.

' 3 mounted upon the shaft 7. The drum casing is carried upon spokes 13. These spokes are constructed as conveyor shovels or paddles and for this purpose are capable of oblique adjustment according to the desired speed of conveyance, so that the stock, being mixed may be accelerated or decelerated during its passage through the drum. The interior of the drum casing is provided with a helical strip 14. Between the turns ofthis strip are disposed shovel or paddle blades 15, which are mounted either side by side parallel to the shaft or displaced on the periphery. By the inclusion of several such shovel or paddle surfaces between two adjacent curved portions of the strip, the circumference may be divided into sectors in any desired manner. The shovel or paddle blades project radially into the mixing drum. In this way compartments are formed, within the mixing drum, between which, in consequence of the fiat helical strip, there are When the drum revolves these compartments rotate. In conjunction with, the spokes formed as conveyor shovels or paddles an effective mixing is obtained. The conveying is ensured by means of the helical arrangement of the strip. If need be it is possible to, shape and dispose the shovel or paddle surfaces so as to increase the conveying or mixing effect.

The shaft 7 is preferably hollow, so that liquid and/or air maybe passed through it. In the region of the dry mixing an admission nozzle for such fluid is provided.

This nozzle is protected against fouling by means of a sleeve 16. It is possible in this manner, even before actually passing in the liquid, to add moisture to the mixing stock or to spray colour through a spray tube 17.. The mixing stock emerges through the drum aperture 18.

Particularly as shown on Figures 3 and 4 the spoke 13 is fixed with respect to the boss 20, but the boss is rotatable on the longitudinal axis of the spoke on the shaft 7. Adjustability is achieved by pulling out the peg 21,1rotating the spoke 13, and the boss 20 to the desired position, and then reinserting the peg 21 in the boss and into a cooperating aperture 23 formed in the shaft 7.

What I claim is:

A mixing machine for cement and the like, comprising a rotatable cylindrical drum, a shaft concentric with said drum, a plurality of spokes radiating from said shaft and connected to said drum and constituting shovel blades, each spoke being obliquely adjustable and having a flat surface inclined to a transverse plane relative to the drum axis, an helical strip secured to the inner curved surface of the drum, and a plurality of longitudinally disposed shovel blades spaced around the inner curved surface of the drum between each adjacent pair of turns of the strip, the radial depth of the strip being less than that of the blades, and the radial depth of each blade being less than half the free radial space within the drum.

References Cited in the file of this patent UNITED STATES PATENTS 410,016 Phillips Aug. 27, 1889 1,048,763 Tiedtke Dec. 31, 1912 1,872,624 Eggert Aug. 16, 1932 1,953,091 Westberg et al. Apr. 3, 1934 2,322,189 Cole June 15, 1943 2,638,687 Vincent May 19, 1953

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