RHEOMETER HAVING A GAS BEARING

Abstract

A rheometer has a shaft, which is supported rotatably in a gas bearing. The gas bearing has a first bearing element (rotor) attached to the shaft and a second bearing element (stator) that surrounds the first bearing element (rotor) with a distance between the two, forming a bearing gap. At least sections of the second bearing element (stator) are made from a gas-permeable material, and gas is passed through them in such manner that a gas cushion is formed in the bearing gap, by which the first bearing element (rotor) and the shaft are supported without direct contact between the two. It is provided that the first bearing element (rotor) is also made from a gas-permeable material, at least in the areas that face the second bearing element (stator), and which the gas penetrates and forms a preferably static gaseous layer close to the surface as a result of the dynamic pressure or backpressure of the gas.

Claims

1. A rheometer having a shaft which is supported rotatably in a gas bearing, wherein the gas bearing comprises a first bearing element attached to the shaft and a second bearing element that surrounds the first bearing element with a space in between, forming a bearing gap, wherein at least sections of the second bearing element are made from a gas-permeable material, through which the gas flows in such manner that a gas cushion (P) is formed in the bearing gap, by which the first bearing element and the shaft are supported without any direct contact, and wherein the first bearing element comprises a gas-permeable material at least in those regions facing the second bearing element, and the gas penetrates the material forming a gaseous layer (S) close to the surface as a result of the dynamic pressure or backpressure of the gas.

2. The rheometer according to claim 1, wherein the first bearing element is entirely or at least almost entirely made of the gas-permeable material.

3. The rheometer in according to claim 1, wherein the gas-permeable material is a sintered material or a graphite material or ceramic.

4. The rheometer according to claim 1, wherein the cross-sectional area of the bearing gap measured in a radial plane is equal in the axial end to the corresponding cross-sectional area in its axial central portion.

5. The rheometer according to claim 1, wherein at least sections of the shaft are designed as a hollow shaft with an axial channel, and that the axial channel is linked to the bearing gap via at least one connecting channel that passes through the first bearing element.

6. The rheometer according to claim 5, wherein at least one adjustable throttle is positioned in the axial channel and/or downstream to the channel in the direction of flow.

7. The rheometer according to claim 1, wherein at least one feed channel is formed in the second bearing element, through which a supplied gas (G) can be spread over the entire circumference inside the second bearing element.

8. The rheometer according to claim 7, wherein the supply channel comprises at least two supply channel arms that are entirely independent of each other in terms of fluid flow, each having its own gas supply (G.sub.1, G.sub.2).

9. The rheometer according to claim 8, wherein the supply channel arms are arranged a distance from each other in the axial direction of the second bearing element.

10. The rheometer according to claim 7, wherein a throttle is positioned in at least one of the supply channel arms.

11. The rheometer according to claim 1, wherein the first bearing element has at least one circumferential groove on the surface thereof facing the bearing gap.

12. The rheometer according to claim 1, wherein the first bearing element has at least one spherical part that is in the form of a spherical segment or has a spherical segment-like shape.

13. The rheometer according to claim 12, wherein the first bearing element has two spherical parts in the form of a spherical segment or having a spherical segment-like shape, which are positioned axially one behind the other so that their smaller, flat surfaces face each other or lie flush against each other.

14. The rheometer according to claim 1, wherein the first bearing element has at least one part in the shape of a truncated right circular cone.

15. The rheometer according to claim 14, wherein the first bearing element has two element parts in the shape of truncated right circular cones, which are arranged axially one behind the other such that their smaller, flat surfaces are face each other or lie flush against each other.

16. The rheometer according to claim 1, wherein the first bearing element has at least one part that is in the shape of a tubular, porous sleeve and surrounds the shaft.

17. The rheometer according to claim 1, wherein the first bearing element has at least one spherical part and/or at least one part in the shape of a truncated right circular cone and/or at least one part in the shape of a tubular sleeve.

18. The rheometer according to claim 1, wherein at least sections of the surface of the first bearing element that are outside of the bearing gap are covered and/or sealed by a cover.

Description

[0034] Further advantages and features of the invention will be evident from the following description of exemplary embodiments with reference to the drawing. The drawings show:

[0035] a schematic vertical section through a gas bearing of a rheometer shaft specified in this invention,

[0036] an enlarged view of the gas flow that is set up and the gaseous layer close to the surface,

[0037] a first variation of the design indicated in FIG. 1

[0038] a second variation of the design as indicated in FIG. 1

[0039] a subsequent development of the design shown in FIG. 4,

[0040] a second further development of the design shown in 4,

[0041] a third development of the design shown in FIG. 4,

[0042] an enlarged view of the bearing gap, and

[0043] a schematic vertical section through a gas bearing of a rheometer shaft according to a further embodiment of the invention.

[0044] FIG. 1 shows a vertical section through a gas bearing 10 of a rheometer shaft 11 that is essentially aligned vertically. The shaft is driven in a rotary direction, as indicated by the double-headed arrow A in FIG. 1. The first bearing element (rotor) 12 is seated on the shaft and is attached firmly to the shaft 11 and includes two spherical parts 21, 22, each of which has a layer of spheres, wherein the said parts 21, 22 are arranged one behind the other on the shaft 11 in the axial direction such that their smaller flat surfaces lie flush against one another.

[0045] Shaft 11 is configured as a hollow shaft and has an axial channel 15 extending along the longitudinal direction of shaft 11, and this channel is linked to the connecting channel 16 that extends essentially radially to shaft 11 and this link is via a radial bore 17 in the wall of shaft 11. The connecting channel 16 extends linearly in the region of the contact surface between the two spherical parts 21, 22 of the element.

[0046] Shaft 11 is preferably made from a metallic material, and first bearing element 12 (rotor) is made from a gas-permeable material, particularly a sintered material, a graphite material or ceramic.

[0047] The first bearing element (rotor) 12 is surrounded by a second bearing element (stator) 13 with a space in between, wherein a bearing gap 18 is formed between the outer surface of the first bearing element (rotor) 12 and the inner surface of the second bearing element (stator) 13.

[0048] The second bearing element (stator) 13 is made of a gas-permeable material of the type described. In addition, feed channels 14 are formed inside the second bearing element (stator) 13, and the feed channels 14 have a fluidic connection with an inlet opening 26. A gas (arrow G) is introduced into feed channels 14 through the inlet opening 26 and spreads across the channels over the entire circumference of the second bearing element (stator) 13. Because of the resulting gas pressure and the gas permeability and porosity of the second bearing element (stator) 13, the supplied gas exits at the surface of the second bearing element (stator) 13 facing the first bearing element (rotor) 12 into several small nozzles distributed evenly about the circumference thereof, as indicated by arrows B in FIG. 2. The air exiting the second bearing element (stator) 13 infiltrates the porous surface of the first bearing element (rotor) 12 on the opposite side of bearing gap 18. As a result, however, a backpressure of the gas is generated, forming a static gaseous layer S indicated in FIG. 2, over the entire surface of first bearing element (rotor) 12 that confines the bearing gap 18.

[0049] Gas that subsequently exits the second bearing element (stator 13) is unable to pass through gaseous layer S and then flows along the bearing gap 18 eitheras shown in FIG. 2upwards to the axial outlet of the bearing gap 18 or downwards to the transition area between the two spherical parts of the element as shown in FIG. 2 and then enters the connecting channel 16, flows through the radial bore 17 into the axial channel 15 of the shaft 11, and is dissipated through this.

[0050] FIG. 3 shows a first variant of the embodiment shown in FIG. 1. The gas bearing 10 shown in FIG. 3 differs from the one in FIG. 1 only in that the first bearing element (rotor 12) in this case consists of two parts, each in the form of a right circular truncated cone, wherein the right circular truncated cones are arranged one behind the other in the axial direction of the shaft 11 in such manner that the smaller, flat surfaces thereof lie flush against one another. Consequently, instead of a bidirectionally curved course, bearing gap 18 then has two straight sections which merge into each other in the area of the contact surface of the two right circular truncated cones 23, 24.

[0051] FIG. 4 shows a further variation of the design of gas bearing 10 shown in FIG. 1 and differs from it in that the feed channels 14 inside the second bearing element (stator 13) are divided into two feed channel arms 14a and 14b which are designed completely independent of each other for fluid flow purposes and are placed at a distance from each other in the axial direction of the second bearing element (stator 13), and each of them has an inlet opening 26a, 26b for a gas stream G.sub.1 and G.sub.2. A throttle 27a and 27b are arranged in the corresponding gas line upstream to the respective inlet openings 26a, 26b. This enables different quantities of gas to be supplied to the supply channel arms 14a and 14b at different gas pressures and with different flow velocities. Consequently, the gas exits from axially separated surface of the bearing gap 18 under different conditions, which in turn may lead to a desired axial displacement of the first bearing element (rotor 12) and with it the displacement of the shaft 11.

[0052] FIG. 5 shows a further development of the embodiment of gas bearing 10 shown in FIG. 4 and differs from the latter in that the lower end of shaft 11 as shown in FIG. 5 is sealed, such that the gas which enters the axial channel 15 of shaft 11 through the connecting channel 16 and the radial bore 17 can only escape from the shaft by flowing axially upwards, as shown in FIG. 5. A throttle 19 is positioned in the gas line in the upper area of shaft 11 or downstream to the shaft 11, and this throttle adjusts and varies the flow and pressure conditions in the axial channel 15, and also in the bearing gap 18.

[0053] FIG. 6 shows a second development of the embodiment of the gas bearing 10 shown in FIG. 4, which differs from the latter essentially in that the surfaces of the first bearing element (rotor) 12 that are outside of bearing gap 18 and are oriented axially are covered with a cover 20, and preferably sealed to make them gas-tight. The cover 20, which may either be a cover or a coating, may alternatively be permeable to gas, wherein the material of the cover 20 must still be less permeable to gas than the material of the first bearing element (rotor) 12.

[0054] FIG. 7 shows another development of the design of gas bearing 10 depicted in FIG. 4 and differs from the latter essentially in that besides the connecting channel 16, which extends into the region of the contact surface of the two spherical parts 21 and 22 of the element, further radial connecting channels 28 are formed, and they extend parallel to and at a distance from the connecting channel 26, and each of them is connected to the axial channel 15 formed inside the shaft 11 via a radial bore 29. In addition, grooves 25 are formed on the outer surface of the first bearing element (rotor 12) facing the bearing gap 18 and extend around the entire circumference thereof in order to guide the gas.

[0055] FIG. 8 shows an enlarged view of the bearing gap 18 formed between the first bearing element (rotor) 12 and the second bearing element (stator) 13. This shows that the radial width of the cross section of the bearing gap 18 becomes consistently smaller, starting from the axial middle region thereof, in which the connecting channel 16 branches off, in the direction of the axial end regions thereof, in which the gas stream exits bearing gap 18. Since the distance from the central axisi.e. the radiusis increasing at the same time, the reduction from the circumferential perspective is balanced out. In this context, the bearing gap 18 is geometrically dimensioned in such a manner that the gas flow rate is the same at the axial outlet cross sections and at the inlet cross section in the connecting channel 16. This configuration ensures a high degree of tilt stability with a good load-bearing capacity.

[0056] FIG. 9 shows a modified structure of the gas bearing of a rheometer. Here, sections of shaft 11 are surrounded by a first bearing element (rotor) 12 and connected to it. This bearing element is made from a gas-permeable material of the type described earlier, and is essentially tubular. It has several radial connecting channels 16 that connect the outside of the first bearing element (rotor) 12 to the internal axial channel 15 of shaft 11. In addition, multiple grooves 25 are provided at a distance from each other in the axial direction of the shaft 11 and extending over the outer surface of the first bearing element (rotor) 12.

[0057] The external second bearing element (stator) 13 has a primarily metallic stator housing 30 with a gas inlet port 26 of the type described earlier. An essentially cylindrical stator insert 31 is positioned on the side of the stator housing 30 facing the shaft 11, and essentially surrounds the first bearing element (rotor) 12 to form a bearing gap 18, and is made of a gas-permeable material. A stator chamber 32 is formed on the side of the stator insert facing away from the shaft 11 and can be filled with gas via the outlet opening 26. Under the effect of the gas pressure exerted, the gas in the stator chamber 32 spreads throughout the entire circumference of the bearing element (rotor) 12 and flows through stator insert 31, thus forming the gas stream in the bearing gap 18 that supports shaft 11.

[0058] The preceding text described various design variants of the gas bearing of a rheometer. It should be noted that it is also possible within the scope of the invention to apply each individual feature of each individual embodiment to all the other embodiments, i.e. to implement the individual features in any combination, provided the basic idea of the invention is realised. A limitation to the described exemplary embodiments is neither suggested nor desired according to the invention.