Mixer for double dispensing cartridges or dispensing appliances

The mixer for double dispensing cartridges having two storage cylinders whose volumetric ratio is different from 1:1 comprises a mixer housing which is attachable to the cartridge, and a mixer element group arranged therein. The two contiguous dispensing openings of the cartridge communicate with an inlet portion which precedes the mixer element group, the inlet portion being divided into a larger inlet chamber for the first component having a greater dispensing volume and into a smaller inlet chamber for the second component having a smaller dispensing volume. The smaller inlet chamber is positioned and designed in such a manner that the first component envelops the second component at the outlet of the inlet chamber and the first edge of the first helix cuts both the first and the second component in half, and that the laterally entering second component is guided to the center of the mixer. Such a mixer allows an intimate mixture of the components without the need of previously dispensing a certain useless quantity in order to adjust the correct mixing ratio.

BACKGROUND OF THE INVENTION 
The present invention refers to a mixer for double dispensing cartridges or 
dispensing appliances having at least two storage cylinders whose 
volumetric ratio is different from 1:1, comprising a mixer housing which 
is attachable to the cartridge respectively the dispensing appliance, and 
a mixer element group arranged therein, the two contiguous dispensing 
openings of the cartridge resp. the dispensing appliance communicating 
with the inlet portion of the mixer element group. Such mixers are known 
e.g. from U.S. Pat. No. 4,538,920, and they have the function of 
intimately mixing the two components dispensed from the dispensing 
cartridges n order to prepare them for their application. 
If the two storage cylinders of the dispensing cartridge have approximately 
identical volumes and also have approximately equal dispensing openings, 
no major problems are involved in mixing the two components from the 
start. If however the two storage cylinders have substantially different 
volumes--which is equivalent to different cross-sectional areas since the 
storage cylinders have the same length on account of manufacturing and 
operating conditions--and different dispensing openings, e.g. of a ratio 
of 10:1, there is a risk that the component from the larger storage 
cylinder fills up the mixer element group of the mixer at the beginning of 
the dispensing process and that the second component having a smaller 
volume is thus suppressed or subdued. In particular, in the inlet area, 
the larger partial flow "A" will press the smaller partial flow "B" 
against the wall of the mixing tube on the B side, where it is retarded by 
the wall friction and therefore subdued or suppressed by the larger A 
component and thus can only begin to flow after some time. In this initial 
phase, the partial flow A precedes, and a mixture according to the 
intended proportions cannot take place, so that the components cannot or 
only partially react with each other and their use results in defective 
bonds, joints, impressions, etc. 
Since the second component is generally the hardener (catalyst) and a 
component mixture with an insufficient amount of hardener is useless, it 
is common practice, in order to stabilize the desired proportions of the 
partial flows, to dispense a certain quantity which is discarded before 
being able to start the actual application of the mixture. Besides the 
loss of component substance, these dispensed substances cannot harden and 
may cause disposal problems. 
In European Patent Publication No. 0 584 428, a solution of this problem is 
suggested by first retaining the first, larger component in a chamber and 
by providing means for directing this first component to the inlet chamber 
of the second component and for carrying the latter along. Although this 
embodiment provided an improvement with respect to the state of the art, 
this solution results in an increased flow resistance due to several 
necessary restrictions of the cross-sectional area. This increased flow 
resistance may require a reinforcement of the cartridge walls and involves 
higher dispensing forces. 
Furthermore, a dispensing appliance is known from European Patent 
Publication No. 472,448 in which the outlets of the dispensing appliance 
resp. of the cartridge housing are arranged in such a manner that the 
larger component flows around the smaller one and carries it along. The 
appliance is intended for use with or without a mixer. In the case where 
no mixer is used, the two components unite in the cartridge or in the 
dispensing appliance already, and because of the hardened substance, the 
outlet area must be cleaned after a cartridge exchange before continuing 
to work. If a mixer is used, the substance hardens there, and after 
exchanging the mixer, the work can be continued without cleaning the 
outlet area of the cartridge or of the dispensing appliance. However, in 
the above appliance, no measures are taken to ensure an exact mixing 
ratio. 
SUMMARY OF THE INVENTION 
On this background, it is the object of the present invention to provide a 
mixer in which the components dispensed side by side are guided in the 
inlet portion in such a manner that the two components flow against the 
first mixer element in such a way that a good mixture is guaranteed from 
the beginning and that no increased flow resistance exists in front of the 
first mixer element group. This object is attained by a mixer wherein the 
inlet portion in front of the mixer element group is divided into a larger 
inlet chamber for the first component having a greater dispensing volume 
and into a smaller inlet chamber for the second component having a smaller 
dispensing volume, and wherein the smaller inlet chamber is arranged and 
designed in such a manner that the first component envelops the second 
component at the outlet of the inlet chamber and that the first inlet edge 
of the first helix cuts both the first and the second component in half.

DETAILED DESCRIPTION OF THE INVENTION 
In prior art mixers, the components are randomly supplied to the first 
helix of the mixer, the mixer element group being designed in such a 
manner that the two components are well mixed across the mixer until the 
dispensing end. As mentioned in the introduction, in known mixers having 
different volume ratios resp. cross-sectional ratios of the storage 
cylinders, it occurs that the substance having a larger volume suppresses 
or subdues the substance having a smaller volume, particularly in the 
initial phase, i.e. when the mixing tube is being filled up, so that the 
prescribed mixing ratio cannot be obtained. After a certain time, i.e. 
when the mixer is completely filled and a certain amount has been 
dispensed, the mixing ratio of the partial flows stabilizes at a 
predetermined value. 
FIGS. 1 and 1a show the inlet portion 2 and the upper part of mixer element 
group 1 in perspective views, and FIG. 2 shows the inlet of mixer housing 
3. Inlet portion 2, which fits into mixer housing 3, comprises an aligning 
and guiding projection 6 which fits into a corresponding guide groove 7 of 
mixer housing 3 and which guides partial flow B, in addition. In order to 
orient the mixer with respect to the cartridge or the dispensing 
appliance, the inlet portion may either comprise two aligning portions 4 
and 5, as shown in FIG. 1, which cooperate with the outlet of the 
cartridge or the dispensing appliance, or the mixer housing may comprise a 
recess 25 which cooperates with a corresponding projection of the 
cartridge or the dispensing appliance. 
The smaller component B is supplied from the cartridge outlet resp. from 
the dispensing appliance to channel 11, while the larger component A 
occupies the remainder of the available volume of the inlet portion. The 
shape and the position of the channel cause component A to entirely 
envelop component B at the beginning of the first helix 9. Furthermore, 
FIG. 1a shows that the roof-shaped edge 10 where the first helix begins, 
is located exactly in the center of the channel 11 for the smaller 
component B and divides partial flow A as well as partial flow B in half. 
Blind flange 8 corresponds to the clear width of mixing tube 13 and may 
possibly comprise a sealing bead. Below the blind flange, on the opposite 
side of the inlet of component A, an inclined guiding surface 12 is 
provided which prevents the accumulation of possibly present air or gas 
and thus ensures a good air evacuation and prevents the formation of air 
bubbles in the substance. 
By the precise alignment of both partial flows with respect to edge 10 of 
the first helix 9, which also extends behind the end wall 11a of channel 
11, and by the fact that component B is surrounded by component A, a 
precise mixing ratio and thus an optimal mixture of the two components is 
obtained from the first helix 9 on to the second helix 9a and further, and 
any suppression of component B is prevented. Furthermore, the 
cross-sectional areas of the two partial flows in the area between the 
blind flange and the edge are designed to approximately correspond to the 
mixing ratio. 
In FIGS. 3 to 6, a second embodiment is represented in which the channel 
for the smaller component B is completely enclosed. Since this is also a 
mixer for a double cartridge having adjacent storage cylinders, the outlet 
B of the cartridge and the inlet of the mixer for the smaller component B 
is not disposed in the center but laterally displaced. For an optimal 
envelopment of component B by component A, it is particularly advantageous 
to direct component B to the center of the mixing tube. 
In FIG. 3, inlet portion 14 with the following mixer element group 15 is 
shown in a perspective view. On the B side, the inlet portion is sealed by 
a blind flange 16 which comprises an opening 17 for the smaller component 
B, while the larger component A flows into the inlet portion on the side 
of blind flange 16. When the mixer is connected to the cartridge, cartride 
outlet 22 is sealingly pressed against blind flange 16. Wall 18 is 
arranged perpendicularly to blind flange 16 and serves the purpose of 
centering and stabilizing the inlet portion in the mixer housing. In this 
embodiment as well, an inclined guiding surface 12 is provided below blind 
flange 16 on the opposite side of the inlet of component A in order to 
obtain a good air evacuation. 
In contrast to channel 11 of the previous embodiment, channel 19 for the 
smaller partial flow B is closed on all sides. Channel 19 is oblique with 
respect to the longitudinal axis of the mixer, see also FIG. 4, and ends 
in the center of the mixing tube. Adjacent the channel end, roof-shaped 
edge 20 of the first helix 21 is arranged, which divides the partial flow 
B in two halves in order to provide good conditions for a correct mixture. 
The first mixer element need not comprise an edge 10 or 20, and the latter 
need not be roof-shaped. 
Mixer housing 3B represents an alternative of the mixer housing according 
to FIG. 2 and is attached to the cartridge housing resp. to the dispensing 
appliance by means of a bayonet attachment comprising a guide groove 7B, 
see FIG. 5, matching wall 18 on the A side. The edge of the bayonet flange 
comprises a recess 26 which serves to align the mixer with the cartridge 
of the dispensing appliance. 
In FIG. 4, a cutaway view of mixer housing 3B is shown in which the outlet 
22 with the two dispensing openings 23 and 24 of the double cartridge 
resp. the dispensing appliance is illustrated. In the two cross-sections 
of FIG. 5 and 6 it appears that channel 19 leads to the center of mixing 
tube 13B. 
It follows from the above description that the dispensing openings of the 
dispensing cartridge or of the dispensing appliance must correspond to the 
inlet openings of the mixer, and that it is necessary to take measures 
ensuring that the mixer is attached thereto in the correct position, 
particularly if the volumetric ratio and the ratio of the openings of the 
two storage cylinders are different from 1:1, as is the case in the 
present application. Different additional measures to this end have been 
described in European Patent Application No. 92810645.9 mentioned in the 
introduction. The same applies for the attachment of the mixer of the 
present invention to a mixer connector of dosing and proportioning 
installations. 
The mixer of the invention ensures an efficient and optimal mixing process. 
In this arrangement, the possible occurrence of slight phase shifts or 
pulsations between components A and B, which are caused by different 
influences such as different elasticities of the two cartridge cylinders, 
are largely compensated by the improved balancing and remixing effect of 
the static mixer. In this context, of course, it must be ensured that the 
cross-sectional areas of the partial flows are proportioned in such a 
manner that the two partial flows are supplied to the first helix at the 
same time.