The invention relates to a device for filtering liquids. Such a device is described for example in DE 100 19 672 A1.
Devices of this kind serve the cross-flow permeation of free-flowing media. They contain at least two shafts, onto which in each case many disk-shaped diaphragm bodies are arranged parallel to each other and in mutual distance. The shafts are hollow, and the diaphragm disks are made of ceramic material and are burred with radial channels. Between the radial channels and the inside of the hollow shaft is a conducting connection. The liquid to be filtered arrives from the outside through the porous material of the diaphragm body into the channels, and from there into the hollow shaft.
The shafts mentioned run parallel to each other, so that also the diaphragm disks of two each other adjacent disk stacks are arranged parallel to each other. The shafts are arranged so close next to each other in such a manner that the disks of two disk stacks interlockingly engage.
The disks do not have to have the mentioned design using porous ceramic material. There are also applications in which some disks are built up as so-called dummy disks. It is also possible to make the disks from strainer bodies. Also combinations of the designs mentioned are conceivable, for example the combination of strainer body-diaphragm body. In the following description only the term “disks” is used.
In order to achieve as great a productivity as possible, as many disks as possible are to be positioned on a shaft. The disks therefore must be arranged as close as possible. On the other hand however it must be made certain that the disks of one stack do not touch the disks of the other stack. Therefore an accurate axial positioning of the disks on their shafts is required.
For the purpose of positioning, distancing elements are arranged between adjacent disks. Also for the purpose of an accurate axial positioning the total disk stack is compressed, for example by a nut, which is screwed onto the hollow shaft on one of its ends, and which exerts a suitable pressure on the multiplicity of disks with the distancing elements present between them. A spring assembly can be mounted between the nut and hollow shaft.
Furthermore it must be ensured that the disks are positioned perfectly also in the radial direction, and that with the rotation of the shaft with the disks present on it concentricity is ensured and radial deflecting is avoided. Furthermore it must be ensured that the torque is transferred from the rotating hollow shaft equally onto all disks of the hollow shaft.
Finally a perfect seal between the disks and the distancing elements must be provided, so that no liquid passes through between the disks and the distancing elements to the hollow shaft.
All these requirements could not be fulfilled to the desired extent with the well-known devices.
It is the task of the invention to develop a device of the initially described kind in such a manner that a perfect axial and radial positioning of the disks results, that the impermeability against passing of liquid between the disks and the distancing elements is ensured, that the torque is transferred equally to all disks, and that the whole device with all its many component parts can be easily and reliably assembled.
The central idea of the invention consists in the design of the distancing element. Said distancing element contains one support ring as well as two sealing rings.
The support ring is dimensioned in such a manner that it is oversized in relation to the hollow shaft. Between the lateral surface of the hollow shaft and the inner surface of the support ring thus a ring-shaped gap area is present. This gap area extends over the total length of the hollow shaft. It can be dimensioned amply, so that a free current is possible and deposits are avoided. This is for example of great importance for applications in the pharmaceutical industry.
For the purpose of positioning the support ring exhibits projecting parts, which are supported by the lateral surface of the hollow shaft. The projecting parts can taper—when viewed in a cross-section perpendicular to the axis—towards the lateral surface, so that between projecting part and lateral surface of the hollow shaft only line contact prevails.
In addition a device is provided to create a rotationally fixed connection between the hollow shaft and support ring. Due to the tight restraint between the support rings, the sealing components and the disks, the disks are carried forward by the distancing elements through friction.
One of the projecting parts mentioned can engage in a suitable recess of the hollow shaft parallel to the axis, creating a rotationally fixed connection.
The sealing rings mentioned are located on the two faces of each support ring. They create the desired sealing connection as well as the necessary torque transmission between support ring and disk.
The invention is described in more detail with the drawings. The following is detailed represented:
As can be seen in
The two hollow shafts 1, 1′ are driven—see
In the present case the disks 2 and 2′ serve the purpose of filtration. They are composed of a porous ceramic material and exhibit internal channels. The channels are in conducting connection with the insides of the hollow shafts 1, 1′.
The medium to be treated arrives in the inside of the reservoir 10 through the inlet 10.1. The filtrate/permeate enters then through the pores of the ceramic material the channels mentioned and arrives from there in the inside of the two hollow shafts 1, 1′. It emerges then at the upper ends of the hollow shafts—see the two arrows pointing upward.
Whatever amount is not able to penetrate through the pores of the ceramic material, arrives as residue at the outlet 10.2 of the reservoir 10.
In the design example shown in
The distancing element 3 is crucial. It is ring-shaped. It encloses the hollow shaft 1.
The distancing element 3 includes a support ring 3.1 as well as two sealing rings 3.2, 3.2.
The shape of the distancing element 3 can be seen more accurately in
The support ring 3.1 is oversized in relation to the hollow shaft 1. Its internal circumferential area has a larger radius than the lateral surface of the hollow shaft 1. For this reason a ring-shaped gap 4 is formed between these two areas—see
Support ring 3.1 exhibits a peculiarity. As can be seen in
The ring-shaped gap 4 between the support ring 3.1 and the hollow shaft 1 can again be seen in
As can be seen in
The dimensioning of projecting part 3.1.3 and groove 1.1, represented in
The projecting parts 3.1.1, 3.1.2 and 3.1.3 cause a centering of the support ring 3.1 on the hollow shaft 1 and position thereby at the same time the disks 2 of the total disk stack, which results from the following.
The distancing element carries the two mentioned sealing rings 3.2 on its two faces. In the present case these two sealing rings are connected by a bar 3.3. The sealing rings 3.2 and the bar 3.3 are one-piece. The bar has thereby no functional meaning, but is suitable for production reasons. It could also be positioned radially further outside, in such a manner that the two sealing rings 3.2, 3.2 form together with the bar 3.3 in the representation according to
The perspective representation of the distancing element 3 according to
In the left-hand end of the figure the sealing ring 3.2 can be seen in a condition, in which it is fastened to the support ring 3.1 by vulcanizing, however without being machined. In the right-hand side the two sealing rings 3.2, 3.2 are machined and a seat is formed, which is rectangular in this representation. The purpose of this seat is to receive the disk 2. The accurate seat can be formed directly during the vulcanization. The seat face can be profiled, for example in a wave shape or saw tooth shape.
The total disk stack including the multiplicity of distancing elements 3 present between them is restrained evenly in axial direction during assembly. An axial pressure is exerted, so that the components mentioned are pressed together. This can be achieved for example by screwing a nut onto one end of the hollow shaft 1; here the nut exercises an axial load on the distancing element 3 when it is tightened. The contact pressure is passed symmetrical and without friction losses to all other disks 2 and distancing elements 3.
The special design according to the invention of the carrying component 3 enables the distancing elements 3 to slide in axial direction basically frictionless on the lateral surface of the hollow shaft 1 when restrained as mentioned. Thereby a pressure drop of the clamping force over the length of the hollow shaft 1 is avoided.
The clamping force is necessary in order to transfer the torque that is transferred by the shaft 1 to the support ring 3.1 also to the disks 2. A frictional connection between the disks 2 and the sealing rings 3.2 is created by the restraint mentioned, so that when the hollow shaft 1 is turned all disks are taken along.
The following benefit, which results from the invention, is especially important: The axial clamping of the disks 2 and the distancing elements 3 leads to an accurate positioning of the disks 2 in axial direction. It is important that in an arrangement according to the
The material of the support rings 3.1 should be a relatively hard, to a large extent incompressible material, for example high-grade steel, in special cases titanium, ceramic(s), carbon, synthetic, e.g. enforced.
As materials for the sealing rings ductile and/or elastic ductile materials come into consideration, e.g. elastomers, easily ductile metals and/or their alloys as well as graphite.
An important point is the problem of the expansion of the whole unit during a temperature rise. The hollow shaft 1 will generally be made of high-grade steel. Its thermal expansion can be easily determined.
The thermal expansion of the hollow shaft is to be compared to the thermal expansion of its surrounding components, i.e. the disks 2 consisting of ceramic(s) or the like, the carrying components 3.1 and the sealing rings 3.2. Hereby it is desirable or necessary that these two components—hollow shaft on the one hand and disks, carrying components, sealing rings on the other hand—show the same thermal expansion behavior. This is usually not the case. Therefore according to a further thought of the invention it is recommended to select concerning the materials of the three components last mentioned—disks, support rings, sealing rings—materials that lead to the desired result when interconnected. See for this
These two structural components, in each case containing shaft and disks, are located in a reservoir 10. The reservoir 10 includes a tubular, cylindrical casing 10.3, a base 10.4 as well as a lid 10.5. The reservoir does not have to be a regular cylinder. It can for example have the cross-section of a polygon. The reservoir does not even have to be cylindrical. It can be for example in the shape of a truncated cone.
The shafts 1, 1′ are passed through the lid 10.5. They are mounted in the lid and sealed. The bearing and the seal are not represented here in detail.
On the exterior of the lid 10.5 are, likewise not represented, drive units for the two shafts 1, 1′.
It is important that the two shafts 1, 1′ are over-mounted. They thus project freely out of the lid 10.5, without the need for a support of the two shafts 1, 1′ at their other ends. In the present case thus a distance between the free ends of the shafts 1, 1′ and the base 10.4 prevails.
Such a recess 5.4.1 can be suitable. However, it is not absolutely necessary. In each case no seal is required at the free end of the two shafts 1, 1′. Medium flows around the free shaft end during operation.
Particularly interesting design examples are represented in
The design example according to
The whole device according to
The twin design according to
In the design example according to
Contrary to the design examples according to
The drive unit of the shafts is located between the two single devices.
All devices according to the invention, shown here, can exhibit the following features:
The reservoir casing 10.3 forms together with the outer circumferences of the disk stacks two areas 15, 15′, which look remotely similar to a sickle-shape. These two areas 15, 15′ can be used very well for taking up auxiliary aggregates, particularly of cooling equipment, but also of heating equipment. See the schematically suggested condenser tubes 16, which run parallel to the longitudinal axis of the reservoir casing 10.3.
The inventors invented a particularly interesting method of operating the device. The device will be operated in such a manner that the disk stacks are during a certain time interval in standstill, then in rotation, then again in standstill, and so on. Thus the following is achieved:
During the standstill phases a static filtration takes place. A cake creates itself on the external surfaces of the disks. During the time intervals of rotation the cake is removed again.
This thought can be applied not only to the design of the device according to the invention, but also to a design deviating herefrom. Only the design of the disk stacks mentioned is necessary, in which the disks of one stack engage in the spaces between each other adjacent disks of the other stack. The rotation of the disks in the same direction is not necessary, but it is preferred.
Number | Date | Country | Kind |
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100 34 055 | Jul 2000 | DE | national |
101 01 846 | Jan 2001 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP01/07588 | 7/3/2001 | WO | 00 | 2/24/2003 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO02/05935 | 1/24/2002 | WO | A |
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