ROTARY VANE VACUUM PUMP

Abstract

The invention relates to a rotary vane vacuum pump comprising a housing member whose inner wall defines at least one pumping space, and a rotor that is arranged for rotation in the pumping space and has a rotor member and at least one vane, wherein the vane projects radially beyond the rotor member and together with the inner wall of the housing body a pumping volume that can be pumped by rotation of the rotor from an inlet to an outlet of the rotary vane vacuum pump, wherein the vane, at least in a region cooperating with the inner wall, comprises a polytetrafluoroethylene material containing polyimide particles and manufactured by hot pressing and sintering, and wherein the inner wall has a slide layer at least in a region cooperating with the vane, said slide layer comprising an oxide layer formed by anodic oxidation in an electrolyte including oxalic acid.

Claims

1. A rotary vane vacuum pump comprising a housing member whose inner wall defines at least one pumping space; and a rotor that is arranged for rotation in the pumping space and has a rotor member and at least one vane, wherein the vane radially projects beyond the rotor member and defines together with the inner wall of the housing member a pumping volume that can be pumped from an inlet to an outlet of the rotary vane vacuum pump by rotation of the rotor; wherein, at least in a region cooperating with the inner wall, the vane comprises a polytetrafluoroethylene material containing polyimide particles and manufactured by hot pressing and sintering; and wherein, at least in a region cooperating with the vane, the inner wall has a slide layer that comprises an oxide layer formed by anodic oxidation in an electrolyte containing oxalic acid.

2. The rotary vane vacuum pump in accordance with claim 1, wherein the total vane is manufactured from the polytetrafluoroethylene material.

3. The rotary vane vacuum pump in accordance with claim 1, wherein the total inner wall defining the pumping space has the slide layer.

4. The rotary vane vacuum pump in accordance with claim 1, wherein the vane is displaceably supported in the rotor member and, at least in a region cooperating with the rotor member, comprises a polytetrafluoroethylene material containing polyimide particles and manufactured by hot pressing and sintering, with at least, in a region cooperating with the vane, the rotor member having a slide layer that comprises an oxide layer formed by anodic oxidation in an electrolyte containing oxalic acid.

5. The rotary vane vacuum pump in accordance with claim 4, wherein the rotor member has a guide for the vane and the regions are cooperating guide regions.

6. The rotary vane vacuum pump in accordance with claim 4, wherein the rotor member has an abutment for the vane and the regions are cooperating abutment regions.

7. The rotary vane vacuum pump in accordance with claim 1, wherein a closure wall is provided that extends transversely to an axis of rotation of the rotor and axially bounds a respective pumping volume, with, at least in a region cooperating with the closure wall, the vane comprising a polytetrafluoroethylene material containing polyimide particles and manufactured by hot pressing and sintering, and with, at least in a region cooperating with the vane, the closure wall having a slide layer that comprises an oxide layer formed by anodic oxidation in an electrolyte containing oxalic acid.

8. The rotary vane vacuum pump in accordance with claim 7, wherein the closure wall is part of the housing member.

9. The rotary vane vacuum pump in accordance with claim 7, wherein at least one of the closure wall and a second closure wall is formed by a component separate from the housing member.

10. The rotary vane vacuum pump in accordance with claim 1, wherein the housing member, the rotor member and/or the closure wall, at least in the region of the slide layer, comprises/comprise a base material that is at least partly formed from aluminum or an aluminum alloy and to which the slide layer is applied.

11. The rotary vane vacuum pump in accordance with claim 1, wherein the rotary vane vacuum pump has a temperature regulating device for the pumping space.

12. The rotary vane vacuum pump in accordance with claim 1, wherein the temperature regulating device is configured to maintain the temperature of at least one of the inner wall, the rotor body of the closure wall, and the vane in a temperature range in operation, with an upper limit of the temperature range amounting to at most 100 C., and/or with a lower limit amounting to at least 20 C.

13. The rotary vane vacuum pump in accordance with claim 1, wherein the rotor is supported at at least one side by a plastic plain bearing.

14. The rotary vane vacuum pump in accordance with claim 1, wherein the rotary vane vacuum pump is formed as two-stage.

15. The rotary vane vacuum pump in accordance with claim 1, wherein the rotary vane vacuum pump is configured for dry running.

16. The rotary vane vacuum pump in accordance with claim 1, wherein the rotary vane vacuum pump is free of a vapor pressure safety valve.

Description

[0049] The invention will be explained only by way of example in the following with reference to the schematic drawing.

[0050] FIG. 1 shows a schematic diagram of a rotary vane vacuum pump of the prior art;

[0051] FIG. 2 shows a rotary vane vacuum pump of the prior art in a sectional representation;

[0052] FIG. 3 shows a further rotary vane vacuum pump in a sectional representation; and

[0053] FIG. 4 shows the pump of FIG. 3 in a longitudinal section.

[0054] The rotary vane vacuum pump 10 of the prior art shown in FIG. 1 comprises an inlet 12 via which a process gas enters in operation of the pump 10 as indicated by an arrow. The process gas is pumped to an outlet 14 by the pump 10.

[0055] The rotary vane vacuum pump 10 additionally comprises a housing member 16 whose inner wall 18 defines a pumping space 20 for the process gas. A rotor 22 is arranged for rotation in the pumping space 20 and comprises a rotor member 24 and two vanes 26. The vanes 26 are each displaceably supported in a recess 28 of the rotor member 24 and are radially outwardly preloaded and thus preloaded against the inner wall 18 by a spring, not shown, at the recess base. The rotor 22 is arranged eccentrically toward the inner wall 18 of the housing member 16 so that on a rotation of the rotor, the vanes 26 are displaced in the recesses 28, but maintain contact with the inner wall 18.

[0056] The vanes 26 project radially beyond the rotor member 24 and together with the inner wall 18 of the housing member 16 define a pumping volume 30 that can be pumped from the inlet 12 to the outlet 14 by rotation of the rotor 22. The rotor 22 rotates in this process counterclockwise with respect to FIG. 1.

[0057] An outlet valve 32 is provided in front of the outlet 14 in the pumping direction and prevents a backflow of the process gas into the pumping space 20, for example on a functional problem and/or a standstill of the pump 10. A valve can alternatively or additionally also be provided at the inlet 12.

[0058] The vacuum pump 10 further comprises an outer housing 34 that comprises an oil chamber 36 that is filled with oil for lubricating the pump 10. The oil chamber 36 is in fluidic contact (not shown) with the pumping space 30 and thus provides a lubrication of the rotor 22 in the pumping space 30. It is therefore here the initially described classical case of a rotary vane vacuum pump by means of which a fine vacuum can admittedly generally be achieved. The oil can, however, result in an unwanted chemical reaction with the process gas and/or in a contamination of a recipient (not shown) connected to the inlet 12.

[0059] A rotary vane vacuum pump 10 of the prior art is shown in FIG. 2. The same reference numerals are used herein for corresponding features, with the corresponding features also being able to be differently configured. The longitudinal section of FIG. 2 has a sectional plane that extends along an axis of rotation 38 of a rotor 22 of the pump 10.

[0060] The pump 10 comprises an inlet 12 and an outlet that is not visible due to the selected sectional plane. Two pumping spaces 20.1 and 20.2 are provided in the pumping direction between the inlet 12 and the outlet and are each defined by an inner wall 18.1 and 18.2 respectively of a housing member 16.

[0061] The rotor 22 comprises a rotor member 24 and vanes 26.1 and 26.2 that rotate in the corresponding pumping spaces to pump the process gas. The rotor 22 can, for example, also have at least one further vane 26, in particular per pumping space 20.

[0062] The pump 10 of FIG. 2 also has an oil chamber 36 for providing a lubricating oil. The invention can nevertheless be further illustrated in the following with reference to FIG. 2 and also with reference to FIG. 1.

[0063] With reference to FIG. 1, in accordance with the invention at least one of the vanes 26 is formed at a region 40 cooperating with the inner wall 18 such that it comprises a polytetrafluoroethylene material containing polyimide particles and manufactured by hot pressing and sintering. At least in a region 42 cooperating with the region 40 of the vane 26, the inner wall 18 has a slide layer that comprises an oxide layer formed by oxidation in an electrolyte containing oxalic acid. This material combination of the friction partners enables particularly low friction so that an oil lubrication and an oil chamber 36 can in particular be dispensed with. The described slide layer is in particular applied to the total inner wall 18, that is in particular cylindrical, of the housing member 16. The low friction is thus implemented over the total friction path described by the vane 26 at the inner wall 18 and the slide layer can additionally be applied advantageously, inexpensively, and particularly homogeneously.

[0064] The friction can be further minimized in that, for example, the rotor member 24 has the slide layer in accordance with the invention at a guide region 44 for the vane 26, with the vane 26 comprising the polytetrafluoroethylene (PTFE) material in accordance with the invention at a corresponding guide region 46. This can advantageously also be provided in the other vane 26 or at an oppositely disposed guide region for which this is not separately referenced for reasons of clarity.

[0065] The rotor member 24 comprises an abutment having an abutment region 48 that can advantageously be provided with the slide layer in accordance with the invention. A corresponding abutment region 50 of the respective vane 26 comprises the PTFE material in accordance with the invention. Friction and wear are thus also reduced here. The total vane can in particular be manufactured from the PTFE material in accordance with the invention.

[0066] Guide regions 44 and 46 of at least one vane 26 or of the vanes 26 can also be equipped with the material pairing in accordance with the invention in the pump 10 shown in FIG. 2. The respective inner wall 18 can have the described slide layer with the advantages in accordance with the invention. A region of the respective vane 26 cooperating therewith is not visible in FIG. 2, but advantageously comprises the described PTFE material.

[0067] A further pair of cooperating guide regions 52 and 54 of the vane 26 and the rotor member 24 is visible in FIG. 2 and can likewise comprise the material pairing in accordance with the invention. While the guide regions 44 and 46 extend in the longitudinal direction, the guide regions 52 and 54 are formed at respective axial end regions of the vane 26 or rotor member recess.

[0068] Closure walls 56 for the pumping spaces 20 are visible in the longitudinal section shown in FIG. 2. They each axially bound the respective pumping volumes 30. A closure wall 56.1 is formed by a component that is separate from the housing member 16 and that also forms a support for the rotor 22 in this embodiment. A second closure wall 56.2 is formed in one part with the housing member 16. The closure walls 56.1 and 56.2 together axially bound a pumping volume 30.1. The pumping volume 39.1, as also the pumping volume 30.2, is radially bounded by the inner wall 18 and by the rotor member 24. The respective pumping volume 30 is bounded by the vane or vanes 26 in the peripheral direction. A respective closed pumping volume 30 is hereby defined that is pumped from the inlet 12 to the outlet by rotation of the rotor 22.

[0069] In a similar manner to the closure walls 56.1 and 56.2, the closure walls 56.3 and 56.4 are likewise formed in one part with or separately from the housing member 16, with other constructions also being possible.

[0070] At least one of the closure walls 56 can advantageously be equipped with the slide layer in accordance with the invention. A vane 26 here advantageously comprises the PTFE material in accordance with the invention at least in a region 58 cooperating with the closure wall 56. The friction is thus minimized at a further position and the leak tightness, service life, and pump power of the pump 10 are improved overall. The further closure walls 56.2, 56.3, and 56.4 and the respective regions of the respective vane 26 cooperating herewith, but not separately referenced, can be equipped with the material pairing in accordance with the invention to further reduce the friction.

[0071] In a further embodiment, the housing member 16, the rotor member 22 and/or the separate components forming the closure walls 56.1 and 56.4 are configured such that they comprise aluminum or an aluminum alloy as the base material at least in the regions cooperating with at least one of the respective vanes 26. Not only the total weight of the pump 10 is hereby reduced, but a particularly advantageous base material for the respective slide layer is also provided.

[0072] It also applies to the pump 10 of FIG. 2 that the oil chamber 36 or the lubrication oil and/or further parts of a liquid lubrication system can now be omitted. This not only saves the costs associated therewith, but also enables completely new application areas of the rotary vane vacuum pump 10 that in particular has two stages. The features described here are admittedly not restricted to a two-stage rotary vane vacuum pump, but they can develop further or improved advantages in same. A particularly low end pressure is in particular hereby achievable, with a contamination of process gas and/or recipient being avoided.

[0073] FIG. 3 shows a rotary vane vacuum pump 10 in accordance with the invention in a cross-section. A rotor 22 of the pump 10 comprises a rotor member 24 and, in this embodiment, three vanes 26. The vanes 26 are arranged distributed over the periphery of the rotor member 24 and are radially displaceably supported in respective recesses of same. In this embodiment, the vanes 26 are furthermore formed at a slant with respect to the periphery of the rotor member 24. Their connection axes do not intersect the axis of rotation 38 of the rotor 22. Respective sections of the vanes 26 projecting radially beyond the rotor member 24 bound a pumping volume 30 in the peripheral direction.

[0074] Regions 40 and 42 having the material pairing in accordance with the invention are provided at the vane 26 and at the inner wall 18. In addition, this material pairing can be provided at guide regions 44, 46 and/or at abutment regions 48, 50 of the vane 26 or rotor member 24.

[0075] The housing member 16 has a temperature regulating device formed as a cooling device. The cooling device comprises a plurality of cooling ribs 60 by means of which heat can be led off from the pumping space 20 and from the housing member 16. The cooling device can, for example, be constructionally adapted to maintain the temperature of the inner wall 18 and/or of other pump-active components in a temperature range in operation. The cooling device can, for example, comprise a fan, not shown, that is it can be configured as active. Alternatively or additionally, for example, a liquid temperature regulating device can be provided.

[0076] The rotary vane vacuum pump 10 of FIG. 3 is shown in a longitudinal section in FIG. 4. The rotor 22 with the rotor member 24 and with one of the vanes 26 can inter alia be seen as well as a housing member 16 whose inner wall 18 defines a cylindrical pumping space 20 in which the rotor 22 for pumping a process gas can rotate.

[0077] As can be seen in FIG. 4, the pump 10, unlike that of FIG. 2, is a single-stage rotary vane vacuum pump having only one pumping space 20. The latter is axially bounded by closure walls 56 of which in turn one, the left one in FIG. 4, is formed by a separate component and one, the right one in FIG. 4, is connected to the housing member 16 in one part.

[0078] As already stated with respect to FIG. 4, the vane 26 has the PTFE material in accordance with the invention at a region 40 that slides along a region 42 of the inner wall 18 in operation, while the inner wall 18 has the slide layer in accordance with the invention in the corresponding region 42. The material pairing in accordance with the invention composed of the PTFE material and the slide layer is also provided at a region 61 of the vane 26 or a region 58 of the closure wall 56.

[0079] The rotor 22 is advantageously supported at at least one side, here at two sides, by the component forming the closure wall 56. They are here in particular a separate support plate 62 and/or a support region of the housing member 16.

[0080] The rotor 22 can, in accordance with FIG. 4, be supported for a further friction reduction and for an avoidance of lubricants at at least one side, here at two sides, by a plain bearing that is in particular formed as a plastic plain bearing.

[0081] The vacuum pumps shown are optimized in a technical friction manner at a number of points in comparison with the prior art. A rotary vane vacuum pump for providing a fine vacuum in dry operation can hereby be implemented overall with a good service life and little wear. Before knowing of the invention, there was apparently no need in the technical word for a dry rotary vane vacuum pump in the fine vacuum sector and at least no approach to develop same, and indeed, on the one hand, due to the easily available scroll pumps and, on the other hand, due to the pressure limit of the water vapor pressure previously caused by the principle. It has now been shown that the cost benefits of the rotary vane vacuum pumps can also be used in this application case, namely dry running in conjunction with fine vacuum generation.

REFERENCE NUMERAL LIST

[0082] 10 rotary vane vacuum pump [0083] 12 inlet [0084] 14 outlet [0085] 16 housing member [0086] 18 inner wall [0087] 20 pumping space [0088] 22 rotor [0089] 24 rotor member [0090] 26 vane [0091] 28 recess [0092] 30 pumping volume [0093] 32 outlet valve [0094] 34 outer housing [0095] 36 oil chamber [0096] 38 axis of rotation [0097] 40 region [0098] 42 region [0099] 44 guide region [0100] 46 guide region [0101] 48 abutment region [0102] 50 abutment region [0103] 52 guide region [0104] 54 guide region [0105] 56 closure wall [0106] 58 region [0107] 60 cooling ribs [0108] 61 region [0109] 62 support plate [0110] 64 plain bearing