Device for mixing and applying wet concrete

A method and device for preparing a wet concrete mix. An elongated tubular swirl chamber has a generally cylindrical shaped interior. A shaft extends axially in the chamber and is adapted for rotation at about 100 r.p.m. or higher. The chamber contains an inlet end for the introduction of dry particles pneumatically carried by a pressurized gas and an outlet end. Blades are arranged in several rows circumscribing the shaft so that the blades overlap to form a helical spiral to aid in moving the particles through the chamber. The blades in the helical spiral form a turbulent swirling distribution of particles traveling through the chamber when the shaft is rotated at 100 r.p.m. or higher and simultaneously the particles are forced by the pressurized gas through the chamber. A liquid is injected into the turbulent swirling distribution so as to wet the particles. The wetted particles are ejected out of the outlet by the force of the pressurized gas and at the same time the blades in the helical spiral are rotating to form the turbulent swirling distribution.

The invention relates to a device for mixing and spraying wet concrete, 
especially in underground cavity structures. The device consists of a 
device for metering and pneumatically transporting dry mix such as cement, 
sand, gravel and dust- or fiber-like additives, from which the dry mix is 
fed to a swirl chamber; a swirl chamber in which the dry mix is mixed with 
liquids; and a wet-spraying nozzle. 
Devices for spraying wet concrete are known, in which the water is fed to 
the dry mix directly at the spraying nozzle. Such devices have the 
disadvantage that the dry mix is wetted only incompletely. This makes the 
quality of the wet concrete frequently inhomogeneous. In addition, much 
dust is developed which can lead to health damage such as silicosis, 
especially in underground cavities. 
From Offenlegungsschrift No. 29 47 913, a device is further known, in which 
the dry mix is mixed with water in a kneading worm, to which wet concrete 
is fed via a densifier screw to a nozzle which leads into a ring nozzle 
and from which the wet concrete is fed to the spraying nozzle by means of 
compressed air. This device has the disadvantage that because of the not 
absolutely uniform transport of the wet concrete from the densification 
screw, the compressed air fed-in via the ring nozzle backs up and 
penetrates into the kneading worm. This prevents a uniform transport of 
the wet concrete. A further disadvantage is due to the fact that through 
the backup of compressed air fed from the ring nozzle, pressure 
equalization of the compressed air fed from the ring nozzle with the 
compressed air in the kneading worm takes place, by which the dry mix is 
fed to the kneading worm. Thereby, a complete stoppage of the transport 
can occur. It is a further disadvantage that material in fiber form, 
particularly steel fibers, are subjected in the kneading worm to heavy 
mechanical stress and thereby, their effectiveness for the wet concrete is 
reduced. It is an object of the invention to develop a device for mixing 
and spraying wet concrete in underground cavities, by which the 
shortcomings of the known devices are overcome. 
The invention consists of a device in which a high-speed shaft which is 
provided with overlapping vanes arranged in a helical spiral is arranged 
in a swirl chamber and in which, in the vicinity of the one end, an inlet 
for the pneumatically transported dry mix is provided. Over the cylinder 
surface of the swirl chamber, inlets for feeding-in water and liquid 
aggregates or aggregates in dust or fiber form and additives are provided. 
On the side of the swirl chamber facing away from the inlet, an outlet for 
the mixed wet concrete material is provided. 
The shaft of the swirl chamber is preferably driven at 100 to 4000 RPM in 
order to obtain the most intensive turbulence possible and a cement glue 
formation as uniform as possible. 
It may be of advantage to make the shaft a hollow shaft, to add to the 
mixture optionally further additives even if only intermittently. 
It is advantageous to arrange the vanes movably on the shaft, so that, 
depending on the application, the pneumatic mix transport and the 
intensity of the mixing can be influenced. 
The swirl chamber is preferably cylindrical so as to favor by means of the 
vanes the mechanical self-cleaning effect of the swirl chamber. 
If the design of the swirl chamber is cylindrical, it is advantageous to 
arrange the inlet for the dry mix in the one and the outlet for the wet 
concrete material in the other end face of the swirl chamber. Preferably, 
the inlet and the outlet are provided opposite each other in the lower or 
upper region of the end faces. However, it may also be advantageous to 
arrange the inlet and the outlet offset in the regions. 
For certain mixtures it is of advantage to break through the end wall on 
the outlet side with a large area, for instance, to make the end wall as a 
spoke wheel, in the hub of which the shaft is supported, and the end of 
which extends into an adjoining funnel, the end of which leads into the 
hose to the spraying nozzle. 
It may also be of advantage to dispense with the end face on the outlet 
side and to let the cylinder surface merge into a cone. In this case, the 
shaft of the swirl chamber is supported overhung in the end wall on the 
inlet side. 
To prevent clogging in the funnel and to ensure continuous mechanical 
cleaning of the funnel, one or several conical cleaning blades are 
preferably arranged on the shaft end. 
On the shaft of the swirl chamber, several rows of blades are preferably 
arranged which are offset relative to each other to define a helical 
spiral. This allows improved turbulence of the mix. If the swirl chamber 
is cylindrical, the diameter of the cylinder circumscribed by the rotating 
blades preferably corresponds almost to the inside diameter of the swirl 
chamber. This prevents the development of undesirable deposition spaces, 
which is essential in view of the very fast setting of wet concrete 
material. It is difficult to remove deposited and set concrete from the 
swirl chamber later. For this reason it is also advantageous to provide, 
in the design of the cylindrical swirl chamber, with a closed end face on 
the outlet side, one or several cleaning blades. 
It is also possible to design the swirl chamber as a cone tapered toward 
the outlet, where the shaft is supported either overhung in the end face 
on the inlet side or in the end face and in the hub of a spoke wheel 
arranged in the lower portion of the funnel. 
The device according to the invention, has, in each of its embodiments, the 
advantage over the known, so-called dry cement spraying devices, that the 
spraying nozzle may simply be the end of the hose which leads away from 
the swirl chamber and is easy to handle due to its small weigth. 
Furthermore, the wetting of the dry mix is removed from the influence of 
the nozzle operator, which results in a uniform quality of the concrete. 
It is a further advantage that immediately at the working site which in 
the case of tunnel construction, is usually very cramped, the work is not 
hindered by bulky equipment.

The device consists of a swirl chamber 1, the shell 5 of which is 
cylindrical. In the end faces of the swirl chamber 1, a shaft 2 is 
supported in bearings centrically, on which several rows of staggered 
vanes 3 and, at the end face on the outlet side, a cleaning blade 8 are 
arranged. In inlet 4 and an outlet 7 are arranged in the lower portion of 
the end faces. In this embodiment, a further inlet 4' is provided in the 
vicinity of the end face on the inlet side on the cylinder surface 5. 
Finally, several inlets 6 for feeding-in water and liquid additives or 
additives in dust or fiber form are arranged on the cylinder shell 5. 
To prepare the wet concrete, the dry mix which is premixed in a metering 
and conveyer device of known type, is pneumatically fed into the swirl 
chamber 1 via a hose. The dry mix is mechanically stirred in the swirl 
chamber 1 by the vanes 3 and is wetted by the water via the inlets 6 and 
other liquids. At the same time, the mixed material is transported by the 
air stream which comes from the metering and conveyer device, is passed-on 
pneumatically through the swirl chamber 1 and through the outlet 7 to the 
spraying nozzle.