EP3153706B1 - Pump - Google Patents

Description

The present invention relates to a pump, in particular a vacuum pump, which comprises at least two conveying elements which are movable relative to one another, at least one seal arranged on one of the two conveying elements and a sliding layer applied at least in regions to at least one of the conveying elements. In addition, the invention relates to the use of components provided with a sliding layer and at least one seal for the manufacture of pumps, in particular vacuum pumps.

Fluids such as greases or oils can generally be used to seal a delivery chamber of pumps, in particular vacuum pumps. A piston pump, for example, basically has a gap between the delivery chamber and the piston. In a fluid-sealed or -lubricated version, this gap is filled with a fluid, usually oil or grease, during the operation of the pump, the fluid acting as a seal between the piston and the delivery chamber. A disadvantage of such pumps is that the media conveyed by the pump, such as gases or vapors, can react with the fluids used as seals, which in particular can reduce the sealing effect. Another problem, particularly in the case of vacuum pumps, is contamination of the recipient by the fluids used.

For this reason, so-called dry solutions are preferred especially for vacuum pumps, in which the conveyed media do not come into contact with fluids. Here, sliding or rubbing seals made of chemically resistant materials, usually plastics, are generally used. In the case of a piston pump, for example, seals of this type are generally used on Piston arranged. During operation, the seal grinds against an inner wall of a cylinder in order to seal the resulting delivery space as hermetically as possible. Another example of a pump which is usually also operated dry, ie without a fluid lubricant, is a scroll or spiral pump. Scroll pumps have crescent-shaped scoops, which are formed by a rotor with a spiral cross-section in engagement with a similar spiral-shaped stator, the rotor being set into an orbital movement by an eccentric drive. Seals are provided on the spiral end faces to seal the delivery spaces, the end seal of the rotor rubbing against the stator and vice versa.

A disadvantage of such sliding or rubbing seals is that, as a rule, due to the constant sliding friction, they are subject to very high wear and often have only a limited service life. In particular, the seals in the form of dust can wear off in the scoop chamber after some operating time. This dust can disturb both the function of the pump itself and the function of devices connected to the pump.

From the AU 68083 81 A a pump with the features according to the preamble of claim 1 is known.

In the JP 2001 165972 A describes a pump according to a similar technology.

The GB 2 130 685 A describes a piston pump with a coating applied to a body of the piston pump and made of aluminum or magnesium oxide. The coating interacts with a seal made of polytetrafluoroethylene material.

The object of the present invention is therefore to provide a pump with a sliding seal which overcomes the disadvantages described above or at least represents an improvement over known solutions, in order to increase the service life of the pump.

According to the invention, the object is achieved by a pump having the features of claim 1.

• zumindest zwei relativ zueinander bewegliche Förderelemente, die derart angeordnet sind, dass sie unter Ausbildung von zumindest einem Förderraum dichtend zusammenwirken,
• wenigstens eine auf einem der beiden Förderelemente angeordnete Dichtung, und
• eine zumindest bereichsweise auf wenigstens eines der Förderelemente aufgebrachte, mit der jeweiligen Dichtung zusammenwirkende Gleitschicht.

The pump according to the invention, which is preferably a vacuum pump, comprises

• at least two conveying elements which are movable relative to one another and which are arranged such that they cooperate in a sealing manner with the formation of at least one conveying space,
• at least one seal arranged on one of the two conveying elements, and
• an at least partially applied to at least one of the conveyor elements, interacting with the respective seal.

The pump is particularly characterized in that the seal comprises a polytetrafluoroethylene material containing polyimide particles and produced by hot molding and sintering. In particular, the seal consists of the polytetrafluoroethylene material.

The pump is further characterized in that the sliding layer comprises an oxide layer formed by anodic oxidation in an electrolyte containing oxalic acid. In particular, the sliding layer is the oxide layer.

Surprisingly, it has been found that the sliding contact combination of the polytetrafluoroethylene material used according to the invention and the sliding layer not only increases the service life of pumps in general, but also extends the maintenance intervals provided for replacing seals.

This is due in particular to the properties of the polytetrafluoroethylene material used as a seal according to the invention, which contains polyimide particles and is produced by means of hot molding or injection molding or extrusion and is additionally subjected to a sintering process. The seal has a very high dimensional stability and thus wear resistance at elevated temperatures on what is due on the one hand to the very low porosity and on the other hand to the finely divided, non-agglomerated polyimide particles.

In combination with the properties of the oxide layer formed by hard anodic oxidation in a, in particular cold, oxalic acid electrolyte, there are particular advantages.

In comparison to oxide layers which are produced in a sulfuric acid electrolyte, the layers according to the invention have a very low layer thickness tolerance, which is in a range of at most ± 5 μm , in particular approximately ± 3 μm . This means that the oxide layer formed has a very flat surface, which results on the one hand in an exact seal in combination with the seal according to the invention and on the other hand low friction, since less unevenness has to be overcome when the two conveying elements move relative to one another.

In addition, the sliding layer shows only a slight edge effect. These are bone-shaped projections on the edges of the layer, which prevent the exact positioning of the seal on the sliding layer, which is required for an optimal seal. Since the bumps are basically bumps, they also increase the friction during the movement of the two conveying elements relative to one another. Accordingly, the low edge effect in combination with the dimensional stability of the seal according to the invention also leads to a particularly low wear rate of both the sliding layer and the seal.

It has proven to be particularly advantageous if the pump is a spiral or scroll pump, in particular a spiral or scroll vacuum pump. The conveying elements are then correspondingly two spiral elements that can be moved relative to one another, each spiral-shaped on a carrier have a wall running around an axis with a free end face and are arranged in such a way that the walls engage in a sealing manner to form conveying spaces. In this embodiment, the seals are arranged on the free end faces of the walls and the sliding layer is applied to the spiral elements at least in some areas.

Accordingly, there are two combinations of sliding layers, each of which is formed from a seal arranged on the end face and an opposite area of a carrier provided with a sliding layer.

A seal is preferably used for a spiral element, the seal preferably being formed in one piece and in particular in the form of a band. The seals can be connected to the free end faces of the walls, for example by gluing or screwing. It is particularly advantageous if the seals are inserted into a groove provided on the free end faces of the walls. If necessary, a further fixation can then be carried out by means of adhesive or screws.

The sliding layer is preferably applied to the surfaces of the supports facing the conveying spaces, in particular over the entire surface. It may further be preferred if, in addition, the spiral walls of the two spiral elements are at least partially covered with the sliding layer. The spiral elements can also be completely provided with the sliding layer.

A further advantageous embodiment of the pump according to the invention is a piston pump, in particular a piston vacuum pump. The conveying elements are then accordingly a cylinder and a piston movable therein, the seal being arranged on the piston and / or a cylinder inner wall and the sliding layer being applied at least in regions to the cylinder inner wall and / or the piston.

The sliding contact combination is preferably formed here from a piston-side seal and a cylinder inner wall provided with the sliding layer.

The seal is preferably arranged in the circumferential direction on an outer wall of the piston. The seal is preferably formed in one piece and can be attached, for example, by gluing or screwing. However, it is particularly advantageous if the piston outer wall has a groove which partially accommodates the seal. If necessary, the seal can be further fixed in the groove by means of adhesive or screws. The piston can have more than one seal, it being advantageous if one seal is attached to an upper end of the piston outer wall and another to a lower end of the piston outer wall.

The sliding layer is preferably applied only to the inner surface of the cylinder. In principle, however, both the outer wall of the piston and the inner surface of the cylinder can be provided with the sliding layer. Furthermore, it is conceivable that the cylinder inner wall also has a seal, reference being made to the above statements with regard to its fastening.

In one embodiment, the polytetrafluoroethylene material of the seal has a proportion of polyimide particles between 1 and 25% by weight, preferably between 5 and 20% by weight, particularly preferably between 7 and 15% by weight, in particular between 8 and 12% by weight .-%, on. The information refers to the dry weight of the material.

In a further embodiment, the polyimide particles have an average particle size between 1 and 50 μm , preferably between 5 and 40 μm , particularly preferably between 10 and 30 μm , in particular between 15 and 25 μm .

The particle size is determined by means of laser light scattering or laser diffraction. The particle size is also determined by measuring scanning electron microscope images.

The polyimide particles are present in the polytetrafluoroethylene material in particular in finely divided and essentially non-agglomerated form. “Essentially” is to be understood to mean that only a very small number of polyimide particles are present in agglomerates of more than two polyimide particles in the material. In other words, the polyimide particles are embedded homogeneously in a matrix made of polytetrafluoroethylene, with no agglomerates of more than two polyimide particles occurring. The number of agglomerates is determined by evaluating scanning electron micrographs.

It is also particularly advantageous if the polytetrafluoroethylene material has a porosity between 0.1 and 5%, preferably between 0.1 and 2%, particularly preferably less than 1%. The porosity is determined on the one hand by means of light microscopic images and on the other hand by means of electrode microscopic images.

The homogeneous distribution of the polyimide particles in the polytetrafluoroethylene matrix and the low porosity of the polytetrafluoroethylene material are particularly responsible for its wear resistance. Both parameters can be controlled by the hot molding process, in which the raw material of the polytetrafluoroethylene material is heated directly under pressure in a controlled heated tool, and by the subsequent sintering process. If the porosity is less than 1%, the polytetrafluoroethylene material can have a density of up to 2.10 g / cm ³ .

In a further embodiment of the pump according to the invention, the sliding layer has a layer thickness between 10 and 50 μm , preferably between 15 and 40 μm , particularly preferably between 20 and 30 μm . The layer thickness is determined on the basis of electron microscopic sectional images.

In a particularly advantageous embodiment, the sliding layer is additionally impregnated with a dry lubricant, in particular polytetrafluoroethylene. The dry lubricant is stored in the layer and there is no additional layer build-up. The dry lubricant in conjunction with the polytetrafluoroethylene material of the seal improves the sliding behavior and thus reduces friction. The storage of a dry lubricant has the further advantage that the sliding properties are essentially retained in the event of abrasive wear on the sliding layer.

It can also be preferred for the sliding layer to be coated with a dry lubricant, in particular polytetrafluoroethylene, with an additional layer structure occurring here. The additional dry lubricant applied improves the dry lubrication properties of the sliding layer and increases its service life. Polytetrafluoroethylene has anti-adhesive properties and thus makes cleaning the surface of the sliding layer easier.

Alternatively, the sliding layer can also be post-treated with salt solutions or with hot, in particular demineralized, water. Such treatment closes the pores in the sliding layer and increases their corrosion resistance.

The sliding layer preferably has an apparent hardness between 400 and 600 HV 0.025, in particular between 500 and 550 HV 0.025. The hardness is measured using the Vickers (HV) hardness test principle. An indentor in the form of a straight pyramid is pressed vertically into the surface of the sample in question with a predetermined test force. Because the footprint If the pyramid is square, the Vickers hardness can be calculated from the area of the test impression. This is measured with a test force of 0.2452 Newton (HV 0.025). Since the sliding layer can have a porosity between 0.1 and 5% as described above, the hardness is also called apparent or mixed hardness in the present case.

The apparent hardness of conventional layers, in particular those formed by anodic oxidation in an electrolyte containing sulfuric acid, is generally at least 50 HV 0.025 lower. A higher apparent hardness results in higher wear resistance. This could be shown in a Taber-Abraser test, with which the abrasion resistance of different materials can be determined. In the test, the abrasion stress is generated by two friction rollers, which are pressed onto the rotating sample with a specified force. The overlay according to the invention exhibited a wear of 12.5 μ m at a force of 10 N (abrasive roller CS 10) only after 90 000 cycles the sample. Under the same conditions, conventional coatings showed this wear after only 60,000 revolutions.

The improved chemical resistance of the layer according to the invention compared to conventional layers, in particular formed by anodic oxidation in an electrolyte containing sulfuric acid, could be demonstrated by the salt spray test. This is a standardized test according to DIN EN ISO 9227 for evaluating the corrosion protection effect of coatings. With the layer according to the invention, the first noticeable signs of corrosion only appeared after more than 2,000 hours of exposure, whereas conventional layers showed these after half the time.

The coefficient of friction of the sliding layer is preferably less than 0.9, particularly preferably less than 0.8, in particular approximately 0.73, the coefficient of friction being determined using a pin-disc tribometer.

The contact pressure of the tribometer was 5 Newtons at a speed of 6 m / min and 9000 U / min.

The sliding layer has a very high surface quality. Usually, in vacuum pumps, the mutually movable surfaces without a sliding layer according to the invention have a mean roughness value Ra of approximately 0.2 μm and an average roughness depth Rz of approximately 1.4 μm . A slipping layer according to the invention with a typical layer thickness of about 20 μ m is now distinguished in particular by the fact that the average roughness Ra after the application of the sliding layer so as not .mu.m increases more than 1.0, preferably about 0.5 μ m. In the case of conventional layers, the increase in the average roughness Ra is typically at least 1.5 μm . After the application of the sliding layer, the average roughness depth Rz increases with a layer thickness of approximately 20 μm , preferably by less than 0.3 μm , particularly preferably by less than 0.2 μm , in particular by less than 0.1 μm . to. In the case of conventional layers of comparable thickness, the average roughness depth Rz typically increases by at least 0.3 μm .

In a preferred embodiment of the pump according to the invention, the delivery elements comprise a base material which is at least partially formed from aluminum or an aluminum alloy and on which the sliding layer is applied. The conveyor elements preferably consist of aluminum or an aluminum alloy. The base material is particularly preferably an aluminum alloy of the AlMgSi type. Aluminum alloys of the type AlMgSiMn, AlMgSiPb or AlZnMg are also advantageous. Aluminum and aluminum alloys have proven to be particularly suitable for being subjected to anodic oxidation in an electrolyte containing oxalic acid and for forming a sliding layer according to the invention.

Another aspect of the invention relates to the use of one or more seals made of a polyimide particle-containing, by hot molding and sintered polytetrafluoroethylene material, and components which are coated, at least in regions, with an oxide layer formed by anodic oxidation in an electrolyte containing oxalic acid, for the production of sealingly interacting conveying elements for pumps, in particular for vacuum pumps, as described above.

In particular, the conveying elements are spiral elements of a spiral or scroll pump or cylinders and pistons of a piston pump movable therein.

Fig. 1

eine einseitige Spiral- oder Scrollpumpe gemäß einer Ausführungsform der Erfindung in schematischer Schnittdarstellung,

Fig. 2

eine Detaildarstellung der Spiral- oder Scrollpumpe aus Fig. 1,

Fig. 3

eine Teildarstellung einer Spiral- oder Scrollpumpe gemäß einer Ausführungsform der Erfindung in schematischer Darstellung in einem Querschnitt senkrecht zur Achse,

Fig. 4

eine Teildarstellung einer doppelseitigen Spiral- oder Scrollpumpe gemäß einer Ausführungsform der Erfindung in schematischer Schnittdarstellung, und

Fig. 5

eine schematische Schnittdarstellung einer Kolbenpumpe gemäß einer Ausführungsform der Erfindung.

The above and further features and advantages of the invention will be explained in more detail with reference to the following description of the exemplary embodiments with reference to the accompanying drawings, in which identical reference numerals are used to represent identical elements. Show it:

Fig. 1

a one-sided spiral or scroll pump according to an embodiment of the invention in a schematic sectional view,

Fig. 2

a detailed representation of the spiral or scroll pump Fig. 1 ,

Fig. 3

2 shows a partial illustration of a spiral or scroll pump according to an embodiment of the invention in a schematic illustration in a cross section perpendicular to the axis,

Fig. 4

a partial view of a double-sided spiral or scroll pump according to an embodiment of the invention in a schematic sectional view, and

Fig. 5

is a schematic sectional view of a piston pump according to an embodiment of the invention.

In the Fig. 1 The spiral or scroll pump 10 shown comprises a work space 23 enclosed by a housing 12 with a drive area 26. An inlet 11 opens into the work space 23, to which a recipient or a further pump stage can be connected.

A stationary spiral element 13, which is connected to the housing 12 of the pump 10, and a rotating spiral element 16 are arranged in the working space 23. The spiral elements 13, 16 each comprise a carrier 14, 17 and a wall 15, 18 connected to it and spiraling about a respective axis. The carrier 14 of the fixed spiral element 13 can also be formed as part of the pump housing 12. The outlet 22 of the pump 10 runs axially through the fixed spiral element 13. The spiral elements are arranged in such a way that the walls 15, 18 engage in one another in a sealing manner, with the formation of delivery spaces 24. The spiral walls 15, 18 each have an end face 19 on which a seal 20 is arranged. The seals 20 touch the opposite carrier 14, 17, on which a sliding layer 21 is applied. The sliding layer 21 is additionally impregnated with polytetrafluoroethylene.

Fig. 2 shows a detailed view of the spiral or scroll pump Fig. 1 in the area where the seal 20 contacts the carrier 14, 17 provided with the sliding layer 21. In particular, the spiral elements 13, 16 are arranged in such a way that the seal 20 is pressed against the carrier 14, 17. The impregnation of the sliding layer 21 is not shown, since the polytetrafluoroethylene is embedded in the sliding layer. There is no additional layer structure. The impregnation promotes the dry lubrication properties of the sliding layer 21 and additionally reduces its wear.

The carriers 14, 17 and the spiral walls 15, 18 are each formed in one piece and consist of an aluminum alloy of the AlMgSi type. The sliding layer 21 is an aluminum oxide layer produced by anodic oxidation in an oxalic acid electrolyte. The sliding layer 21 is applied in particular to all surfaces of the spiral elements 13, 16 facing the conveying spaces 24. The seals 20 are polytetrafluoroethylene, which contains 10% by weight of polyimide particles (based on the dry weight of the seal) and was produced by hot molding and subsequent sintering. The average particle size of the polyimide particles is 25 μm .

In the drive area 26 of the pump 10 there is an electric motor 31 which comprises a motor stator 30 (winding) and a motor rotor 32 (rotor). The electric motor 31 drives a shaft 33 that defines an axis A _W. The rotating spiral element 16 is coupled to the shaft 33 with an eccentric shaft 35, which defines the eccentric axis A _E. The axis A _{W of} the shaft 33 and the eccentric axis A _E run parallel to one another. Both shafts 33, 35 are supported with bearings 34. The shaft 33 also includes counterweights 36 to ensure that the pump 10 runs smoothly.

During operation of the pump 10, the shaft 33 rotates, and the eccentric shaft 35 connected to it executes an orbital movement about the axis A _{W of} the shaft 33. The spiral element 16 accordingly carries out a centrally symmetrical oscillation movement on a circular path around the axis A _W. The spiral element 16 does not rotate about its own axis A _E , which is achieved by rotation prevention mechanisms known to those skilled in the art. This movement creates closed, crescent-shaped delivery spaces 24 between the interlocking spiral elements 13, 16, which continuously reduce their volume towards the inside in the direction of the pump outlet 22. In this way, a gas drawn in via the inlet 11 is compressed.

The shape of the funding areas can be in Fig. 3 recognize that shows a section of a cross section perpendicular to the shaft 33 of a spiral pump. The cross-sectional plane runs through the interlocking spiral walls 15, 18 of the spiral elements 13, 16.

Since the pump 10 according to Fig. 1 has a movable spiral element 16, the support 17 of which is provided on one side only with a spiral wall 18, it is a one-sided pump system, which is also referred to as a single-wrap pump system.

Fig. 4 on the other hand shows a partial representation of a spiral or scroll pump with a double-sided pump system. The entire housing, including a drive area, has not been shown. In contrast to the one-sided version according to Fig. 1 the circumferential spiral element 16 has a carrier 17 which is provided on both sides with spirally extending walls 18. Furthermore, the fixed spiral element 13 comprises a further support 14 with a spiral-shaped wall 15. Both walls 18 of the rotating double-sided spiral element 16 engage with the walls 15 of the fixed spiral element 13 to form conveying spaces 24. The end faces 19 of the walls 15, 18 are each provided with seals 20. The surfaces of the carriers 14, 17 facing the conveying spaces 24 are provided with a sliding layer 21, the sliding layer 21 being additionally impregnated with polytetrafluoroethylene. With regard to the materials of the spiral elements 13, 16 and the composition of the sliding layer 21 and the seal 20 as well as with regard to the functioning of the pump, reference can be made to the explanations relating to FIGS Fig. 1 and 2nd to get expelled. Compared to a one-sided pump system, the double-sided pump system for delivering a fluid has twice the number of delivery spaces 24.

Fig. 5 shows a schematic sectional illustration of a piston pump 100 according to the invention. A piston 104 fastened to a piston rod 105 is movably mounted in a cylinder 102. The piston 104 and the cylinder 102 together form a delivery space 124. The piston 104 has a seal 120 on both a lower edge 106 and an upper edge 108, which seals against an inner wall 103 of the cylinder 102. The cylinder inner wall 103 is provided with a sliding layer 121 which has also been impregnated with polytetrafluoroethylene. The seal 120 is designed in the form of a narrow band which extends in the circumferential direction around the piston 104. An inner seal leg 120b of the seal 120 is received by a groove 109 arranged on the lower and upper edge 106, 108 of the piston 104, respectively. A free sealing leg 120a extends outside the groove 109 and is angled because it is wider than the distance between the cylinder inner wall 103 and the piston 104. Both the cylinder 102 and the piston 104 are made of an aluminum alloy of the AlMgSi type. The seal 120 and the sliding layer 121 are designed according to the invention, as described above, in particular with reference to Fig. 2 , is described.

During operation of the pump 100, the piston 104 rises and falls, the delivery chamber 124 being reduced and enlarged accordingly and a fluid being sucked in or expelled with timed opening and closing of valves (not shown).

Due to the up and down movement of the piston 104, the free legs 120a of the seals 120 which bear against the inner wall 103 of the cylinder are subject to constant friction. The combination of materials according to the invention from the special sliding layer 121, which has a very smooth surface, and the special, resistant polytetrafluoroethylene seal brings about a reduction in this friction. Firstly, the abrasion on the side of the seal 120 is reduced, which leads to a longer lifespan of the seal and thus to an extension Maintenance intervals. Secondly, the abrasion on the side of the cylinder inner wall 103 is minimized and the service life of the pump 100 is thus extended overall.

In a long-term test lasting over a year, piston pumps, which had a seal and sliding layer designed according to the invention, were compared with structurally identical conventional piston pumps. The conventional pumps had a standard coating formed by anodic oxidation in an electrolyte containing sulfuric acid. The seals of the conventional pumps consisted either of an unsintered polytetrafluoroethylene material or of a polytetrafluoroethylene material which differed from the embodiment according to the invention with regard to the polyimide content and / or the polyimide particle size.

After one year the wear of the seal and the sliding layer was determined. It was found that the combination of materials according to the invention showed the least wear, ie the least layer and seal abrasion. Some of the conventional pumps also failed before the end of the test due to wear.

Reference symbol list

10th

Spiral or scroll pump

11

inlet

12

casing

13

fixed spiral element

14

Carrier of the fixed spiral element

15

spiral wall of the fixed spiral element

16

circumferential spiral element (orbiter)

17th

Carrier of the revolving spiral element

18th

spiral wall of the revolving spiral element

19th

Face

20th

poetry

21st

Sliding layer

22

Outlet

23

working space

24th

Funding area

26

Drive range

30th

Motor stator

31

Electric motor

32

Motor rotor

33

wave

34

warehouse

35

eccentric

36

Balance weight

A _W

Axis of the shaft

A _E

Eccentric axis

100

Piston pump

102

cylinder

103

Inner cylinder wall

104

piston

105

Piston rod

106

lower margin

108

upper edge

109

Groove

120

poetry

120a

free seal leg

120b

inner sealing leg

121

Sliding layer

124

Funding area

Claims (14)

1. A pump (10, 100), in particular a vacuum pump, comprising

   - at least two conveying elements (13, 16, 102, 104) which are movable relative to one another and which are arranged such that they sealingly cooperate while forming at least one conveying space (24, 124);

   - at least one seal (20, 120) arranged on one of the two conveying elements (13, 16, 102, 104); and

   - a slide layer (21, 121) which is at least regionally applied to at least one of the conveying elements (13, 16, 102, 104) and which cooperates with the respective seal (20, 120),

   wherein the seal (20, 120) comprises a polytetrafluoroethylene material which includes polyimide particles,
   characterized in that
   the polytetrafluoroethylene material is manufactured by hot compression molding and sintering; and
   in that the slide layer (21, 121) comprises an oxide layer formed by anodic oxidation in an electrolyte including oxalic acid.
2. A pump in accordance with claim 1,
   characterized in that it is a spiral pump or scroll pump (10), in particular a spiral vacuum pump or scroll vacuum pump,

   - with the conveying elements being two spiral elements (13, 16) which are movable relative to one another, which each have a wall (15, 18) on a carrier (14, 17), said wall (15, 18) extending spirally about an axis and having a free end face (19), and which are arranged such that the walls (15, 18) sealingly engage into one another while forming conveying spaces (24),

   - with the seals (20) being arranged on the free end faces (19) of the walls (15, 18), and

   - with the slide layer (21) being at least regionally applied to the spiral elements (13, 16).
3. A pump in accordance with claim 1,
   characterized in that it is a piston pump (100), in particular a piston vacuum pump,

   - with the conveying elements being a cylinder (102) and a piston (104) movable therein,

   - with the seal (120) being arranged at the piston (104) and/or at an inner cylinder wall (103), and

   - with the slide layer (121) being at least regionally applied to the inner cylinder wall (103) and/or to the piston (104).
4. A pump in accordance with any one of the preceding claims,
   characterized in that the polytetrafluoroethylene material has a portion of polyimide particles of between 1 and 25% by weight, preferably between 5 and 20% by weight, particularly preferably between 7 and 15% by weight, in particular between 8 and 12% by weight, with respect to the dry weight of the material.
5. A pump in accordance with any one of the preceding claims,
   characterized in that the polyimide particles have an average particle size of between 1 and 50 µm, preferably between 5 and 40 µm, particularly preferably between 10 and 30 µm, in particular between 15 and 25 µm.
6. A pump in accordance with any one of the preceding claims,
   characterized in that the polyamide particles are included in the polytetrafluoroethylene material in a finely distributed, substantially non-agglomerated form.
7. A pump in accordance with any one of the preceding claims,
   characterized in that the polytetrafluoroethylene material has a porosity of between 0.1 and 5%, preferably of between 0.1 and 2%, particularly preferably of less than 1%.
8. A pump in accordance with any one of the preceding claims,
   characterized in that the slide layer (21, 121) has a layer thickness of between 10 and 50 µm, preferably between 15 and 40 µm, particularly preferably between 20 and 30 µm.
9. A pump in accordance with any one of the preceding claims,
   characterized in that the slide layer (21, 121) is coated and/or impregnated with polytetrafluoroethylene.
10. A pump in accordance with any one of the preceding claims,
    characterized in that the slide layer (21, 121) has an apparent hardness of between 400 and 600 HV 0.025, preferably between 500 and 550 HV 0.025.
11. A pump in accordance with any one of the preceding claims,
    characterized in that the coefficient of friction of the slide layer (21, 121) determined by a pin-on-disk tribometer amounts to less than 0.9, preferably to less than 0.8, particularly preferably to approximately 0.73.
12. A pump in accordance with any one of the preceding claims,
    characterized in that the conveying elements (13, 16, 102, 104) comprise a base material which is at least partly formed from aluminum or from an aluminum alloy and to which the slide layer (21, 121) is applied.
13. A pump in accordance with claim 12,
    characterized in that the base material is an aluminum alloy of the AIMgSi type.
14. Use of

    - one or more seals (20, 120) composed of a polytetrafluoroethylene material, which includes polyimide particles and which is manufactured by hot compression molding and sintering, and

    - of components which are at least regionally coated by a slide layer formed by anodic oxidation in an electrolyte including oxalic acid

    for the manufacture of sealingly cooperating conveying elements (13, 16, 102, 104) for pumps (10, 100), in particular for vacuum pumps, in accordance with any one of the preceding claims.

Images