US 3924836 A
Description (OCR text may contain errors)
O Unlted States Patent 1191 1111 3,
Bruning et al. Dec. 9, 1975 [5 MIXING DEVICE FOR CURABLE LIQUID 3,318,580 5/1967 Simonetti 259/8 MATERIAL 3,471,131 10/1969 Fritzweiler 259/8  I Kl B T d rf H h 3,495,808 2/1970 Klein 259/8 nventors: aus runin rois o einric Lob, Eschmarglboth of Germany FOREIGN PATENTS OR APPLICATIONS 823,153 lO/l937 France 259/8  Asslgnee- Dynam" Nobel Germany 904,004 8/1962 United Kingdom 259/8  Filed: Apr. 19, 1974 Primary Examiner-Robert W. Jenkins  Appl. NO.. 462,550 Attorney, Agent, or Firm-Craig & Antonelli Related US. Application Data  Continuation of Ser. No. 231,112, March 2, 1972,  ABSTRACT abandoned. A device for mixing curable liquid materials which comprises a mixing vessel, a mixer shaft disposed in  Foreign Application Priority Data the mixing vessel and extending through an opening in Mal. 2, 1971 Germany 2109848 One end of Said vessel, inlet means for introducing the components for forming a curable liquid material into  us. CI. 259/7 the vessel. Outlet means for discharging the resultant 51 Int. C1. BOIF 7/24 mixture therefrom, one of the components being a q-  Field of Search 259/7, 8, 9, 10, 23, 24, Hid component which cannot be cured without eddi- 259/5 43 44; 23/252 R tives, and means for subdividing the vessel into two mixing chambers in communication with each other in  Reference Cit d such a manner that the opening is not blocked with UNITED STATES PATENTS the curable mlxwre- 2,847,196 8/1958 Franklin 259/8 11 Claims, 4 Drawing Figures Dec. 9, 1975 US. Patent MIXING DEVICE FOR CURABLE LIQUID MATERIAL This is a continuation of application Ser. No. 231,112, filed Mar. 2, 1972, now abandoned.
This invention relates to an apparatus for the mixing of curable, liquids, for example, such as formed by the process described in copending application Ser. No. 311,913, filed Dec. 4, 1972, and commonly assigned to the Assignee of the present application, e.g. hardenable, polymeric resin liquids and more particularly to an apparatus having a mixer shaft arranged in a mixing vessel and inlet and outlet ducts for introducing the components to be mixed into the mixing vessel.
In conventional mixers, difficulties are repeatedly encountered during the processing of curable mixtures of polymeric materials and the likeas in connection with the sealing of the wall entrance or opening for the bearing of the mixer shaft with respect to mixture penetrating from the mixer vessel; the mixture enters this zone, hardens, and blocks the mixing device.
The use of slide ring packings at the opening for the mixer shaft with a narrow leakage fluid slot has not provided any help against the breakdown of the mixing apparatus due to mixture entering in the zone of the seal; thus the mixture hardens at that point and blocks the mixer. These disturbances can occur within very short intervals and cause considerable shutoff periods due to the required amount of repairs.
It is the object of this invention to avoid the existing disadvantages in mixing devices for curable liquids, by eliminating any contact of the sealing element, i.e. the mixer shaft opening, bushing or hearing with the curable liquid material.
According to the invention, a mixing device is provided wherein a mixer vessel is subdivided into two mixing chambers which are in communication with each other by forming an annular slot or opening therebetween. With this arrangement, according to a further feature of this invention, it is possible to dispose the inlet duct or means for introducing a liquid mixing component which cannot cure without additives in the mixing chamber adjoining the bearing of the mixer shaft within the mixing vessel. This means that no curable material, e.g. polymer, is present in the space or zone closely adjacent or proximate to the shaft bearing; in other words, the blocking of the mixer shaft due to setting up or curing of a curable material is prevented.
In a further embodiment of this invention, the provision is made to reduce the cross section of the slot in the transitional zone from the first to the second mixing chamber, as compared to the cross section of the inlet duct for the liquid component which cannot be cured without additives, so that a higher pressure is reached in the slot (and the first chamber) than in the subsequent second mixing chamber. In this manner, it is ensured that the liquid component which cannot be cured by itself can flow from the first mixing chamber into the second mixing chamber, but a reverse flow is made impossible. An effective pressure difference is obtained when the cross section of the slot is reduced to about 0.7 0.9 times that of the cross section of the inlet duct for the liquid component which cannot be cured without additives.
The feeding of the curing agents and further liquid components of the mixture, e.g. blowing agents used in the formation of foams from curable polymers, is ef' fected in the zone of the second mixing chamber wherein the mixing procedure is carried out. In other words, the pressure relationships are to be designed in such a manner that the pressure in the slot is, in any event, above the pressure ambient in the second mixing chamber.
The subdivision of the mixing vessel into two chambers can be done in various ways. One embodiment provides that the mixer shaft is fashioned with a disk; whereas, according to another embodiment, the mixing vessel (which is usually cylindrical) is provided with an annular projection or rim on its inside surface. In either case, an annular slot or narrow opening remains between the disk and the vessel wall, or between the projection and the mixer shaft, which slot connects the two mixing chambers. However, it is also possible to provide projections on the shaft as well as on the mixer vessel. In this case, a type of labyrinth slot can be produced, for example. However, it will be recognized that other ways of subdividing the mixing vessel into two communicating chambers in accordance with the principles of the disclosed embodiments are encompassed within the scope of this invention.
The apparatus of this invention will be further understood from the following detailed description of its pre ferred embodiments and with refernce to the accompanying drawing wherein:
FIG. 1 schematically shows a mixing device of the invention in a longitudinal view;
FIG. la shows a cross-sectional view of the device of FIG. 1; and
FIGS. 2 and 3 show different embodiments of the means for subdividing the internal space of the mixing device into two communicating chambers.
The mixing device according to FIG. 1 includes the cylindrical mixing vessel 2, into which the mixer shaft 1 is inserted longitudinally through the opening 3 and a shaft bearing 12 at the end wall of the vessel.
It is the objective of this invention to seal the opening 3 and bearing 12, including slide ring packing l3 and ball bearing 14 against the penetration of curable liquid materials from the mixing chamber. For this purpose, the mixer shaft 1 is fashioned, in the proximity of the bearing opening 3, with the radially extending disk 7, the annular slot 8 remaining between the mixer vessel and the disk 7. The disk 7 subdivides the inner space of the mixing vessel into the two mixing chambers I and II. The mixing chamber I adjoining the opening in the bearing has an inlet duct 4 for the liquid component which cannot be cured without additives, e.g. phenolic resin. Under the buildup of a pressure obtained by the reduction of the cross-section 8a with respect to the cross-section 4a of the inlet duct 4 leading into the mixing chamber I, this component, e.g. the phenolic resin, flows through the slot 8 into the mixing chamber II wherein the mixing operation is conducted. Via the inlet ducts 5, 6, the other flowable components, e.g. curing agents, fillers, etc. of the mixture are fed, as required, into the mixing chamber II; especially the cur ing agents. Via the outlet 9, the curable mixture is discharged or extruded from the mixing vessel 2. When adjusting the pressure relationships in the mixing vessel, attention must also be directed toward the fact that the pressure in the mixing chamber II must not be above the pressure in the slot 8. In such a case, the mixer constructed in accordance with this invention ensures that no curable mixture passes into the opening 3 provided for the mixer shaft 1.
FIG. 2 shows a mixing device wherein the inner space of the mixing vessel 2 is subdivided by means of an annular projection extending from the sidewalls of the mixing vessel. The mixing chamber I formed adjacent to opening 3 can be relatively small as compared to the mixing chamber II wherein the mixing operation occurs.
FIG. 3 shows the subdivision of the mixing vessel into two mixing chambers I and II by means of a disk 7 mounted on the mixer shaft 1, as well as by the projection 10 on the inner sidewall of the mixing vessel 2. These projections cooperate to form a type of labyrinth slot 11. However, other embodiments of the means for effecting subdivision of the internal space of the mixing vessel for preventing curable material from entering the opening for the mixing shafts are also contemplated.
While the novel embodiments of the invention have been described, it will be understood that various omissions, modifications and changes in these embodiments may be made by one skilled in the art without departing from the spirit and scope of the invention.
What is claimed is:
1. A device for mixing curable liquid materials which comprises a mixing vessel,
a mixer shaft disposed in said mixing vessel, said shaft being supported for rotation at one end of said vessel,
inlet means for introducing components for forming a curable liquid material mixture into said vessel,
outlet means for discharging the resultant mixture therefrom, said outlet means being disposed at an end of said mixing vessel opposite to said one end,
one of said components of said curable liquid mixture being a liquid component which cannot be cured without additives,
partition means for subdividing said vessel into a first chamber and a second mixing chamber in communication with each other, said partition means including an annularly extending disk mounted on said shaft,
said inlet means including at least one first inlet duct for introducing the liquid component which cannot be cured without additives into said first chamber, said first inlet duct having a predetermined crosssection, and said inlet means including at least one additional inlet duct for introducing only into said second mixing chamber the additives for curing the liquid component which cannot becured without additives,
said partition means having an opening from said first chamber into said second chamber, said opening having a cross-section reduced by approximately 0.7 to 0.9 times said predetermined cross-section of said first inlet duct such that said one end of said vessel including said first chamber is maintained free of said curable mixture during mixing of said curable liquid material mixture.
2. The device of claim 1, wherein said first chamber adjoins said one end and a bearing is included at said one end in the mixing vessel for the mixer shaft.
3. The device of claim 2, wherein said reduced crosssection of said opening creates a positive pressure differential between said first chamber and said second mixing chamber such that a higher pressure is obtained in the opening than in said second mixing chamber, thereby maintaining said one end free of said curable mixture.
4. The device of claim 3, wherein said opening is formed by the position of said partition means with respect to said mixing vessel such that an annular slot is formed between said annularly extending disk and an inside wall of said mixing vessel.
5. The device of claim 4, wherein said partition means further includes an annular projection, said annular projection being provided on the inside wall of the mixing vessel to form a labyrinth type slot between said chambers with said annularly extending disk.
6. The device of claim 5, wherein said annular projection on said inside wall and said annularly extending disk on said shaft are axially displaced from one another.
7. The device of claim 1, wherein said partition means further includes an annular projection, said annular projection being provided on the inside wall of the mixing vessel to form a labyrinth type slot between said chambers with said annularly extending disk.
8. The device of claim 1, wherein said outlet means includes an extrusion means for discharging said resultant mixture.
9. The device of claim 1, wherein said first chamber is arranged above said second mixing chamber, said one component being introduced into said first chamber and said curable mixture being formed in said second mixing chamber.
10. In an apparatus for mixing curable liquids of the type having a mixer shaft supported in a mixing vessel by means of a bearing and seal support in an opening at one end of the mixing vessel, the improvement comprising means mounted on said mixer shaft for subdividing said mixing vessel into two chambers such that the curable liquid mixture is prevented from contacting said bearing and seal support, and inlet means for introducing a component of said curable liquid mixture into the one of said two chambers adjacent said bearing and seal support, said component being uncurable without the addition of additives, and said inlet means including an inlet duct for said component having a predetermined cross-section, wherein said means for subdividing provides an annular gap between said two chambers with said annular gap having a cross-section of a size relative to said predetermined cross-section of said inlet duct for providing a higher pressure in said gap than in the subsequent chamber to prevent back-flow of the curable liquid mixture to said bearing and seal support.
11. The apparatus of claim 10, wherein the cross-section of said annular gap is reduced by approximately 0.7 to 0.9 times said predetermined cross-section of said inlet duct.