Worm mixer for a container

An improved worm mixer for use in containers having pivotally mounted wires attached to the superficies of the worm and being parallel to the axis of the worm so as to prevent residue from forming on the walls of the container.

BACKGROUND OF THE INVENTION 
This invention relates to a worm mixer for a container. In such containers 
all kinds of substances receive treatments, which vary greatly, ranging 
from mixing pulverulent- and granular materials to pasty substances; such 
a treatment may be carried out at an increased or decreased temperature or 
pressure. During such a process the problem may occur that a layer of the 
treated materials is deposited on the inside wall of the container along 
which the worm mixer moves. This layer may impair the treatment results 
and when the treatment has been terminated and the container is cleaned, 
the layer may be hard to remove. 
SUMMARY OF THE INVENTION 
The invention aims to overcome this trouble and to provide a worm mixer 
which reduces the deposit to a minimum, while moreover the process is less 
influenced by the wall effect. 
This is attained according to the invention by the arrangement that at 
least part of the outer marginal portion of the worm is provided with one 
or more wires or bands which are secured in the vicinity of the 
superficies of the worm. These wires or bands cut loose doughy or pasty 
material clinging to the wall, whereby a smaller propulsion of the 
material in an upward direction along the wall is attained. Furthermore 
the cutting edges reduce the dimensions of the deposit on the container 
wall to a minimum, while the wall effect on the material itself is reduced 
by the regular severance of the material on the wall from that in the 
other part of the container, which particularly may be of importance when 
operating with pasty substances. The cutting edges also have likewise a 
clod breaking, clod cutting effect, respectively on the material which is 
elsewhere in the container. 
According to an efficient embodiment of the invention the wires or bands 
extend in an axial direction over at least one length of pitch of the 
worm. 
According to another embodiment of the invention the wires or bands are 
each mounted on two or more brackets, which are each pivotally connected 
around pivot axes to the blades of the worm, said pivot axes each 
extending parallel to the axes of the worm mixer, whereas the brackets 
have been pivotated eccentrically, the spacing from the pivot axes to the 
leading edge of the band cross section, that preferentially is somewhat 
decreasing to this leading edge, being greater than the spacing to the 
container wall, so that this leading edge can scrape along the container 
wall. These bands scrape by their leading edges close along the inner wall 
of the container and limit the thickness of layer of the deposit of 
hardening substances, so that cleaning the container is considerably 
simplified and almost the entire contents of the container partakes of the 
treatment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 represents a container 1 which contains a worm mixer 2 extending 
close along the inner wall of the container 1. The worm mixer is supported 
at its lower end on a thrust bearing 3 and at its upper end connected with 
a driving head 4. This head 4 is mounted at the end of an arm 5 which is 
rotated by a shaft 6 mounted in the centre of the container 1. Yet another 
separate drive is provided in the driving head 4, so that the worm mixer 2 
is rotated around its own axis on the one hand and is rotated by the arm 5 
close along the inner wall of the truncated conical vessel on the other 
hand. 
The worm mixer 2 comprises a shaft 7 on which is mounted a helical blade 8. 
Along the outer edge of the blade and extending on almost the entire axial 
length thereof is mounted a wire or band 9. This wire or band 9 can have a 
cross section which is circular as at 9a, lozenge-shaped as at 9b, 
rectangular and having blunt edges as at 9c, or rectangular with knife 
edges as at 9d, as indicated in outline in FIG. 1. This wire or band 9 is 
secured, at least at the ends, to the blade 8 and has at least at one end, 
here at its upper end a tensioning device 9a. When pasty or doughy 
substances are treated in the container 1 the wire 9 has a cutting effect 
on the material which deposits on the inner wall of the container, whereby 
the propulsion of this material in an upward direction is considerably 
reduced and a complete mixing in the container 1 is achieved. When the 
wire or band is sufficiently slack tensioned it can scrape along the 
inside of the container. 
FIGS. 2 and 3 show a second embodiment of the invention. 
This comprises wires or bands 10a, 10b that are each mounted on two or more 
brackets 11a, 11b, which are each pivotally connected around pivot axes 
12a, 12b to the blades 8 of the worm 2, said pivot axes 12a, 12b each 
extending parallel to the axis of the worm mixer. 
Furthermore, the brackets 11a, 11b have been pivotated eccentrically, the 
spacing from the pivot axes 12a, 12b to the leading edge 13a, 13b of the 
band cross section, that preferentially is somewhat decreasing to this 
leading edge, being greater than the spacing to the container wall 1, so 
that this leading edge can scrape along the container wall. 
Also, the wires or bands 10a, 10b are distributed around the circumference 
of the worm shaft 7, whereas these wires or bands each extend over a short 
length of one or more pitch length.