Sustainable rotary vane vacuum pump

Abstract

The invention relates to an improved oil-lubricated rotary vane vacuum pump having a rotor (4) in a rotary vane chamber (13), wherein the inner wall of the rotary vane chamber (13) has at least one oil pocket (9) with at least two oil pocket portions (11, 12), and the oil pocket portions (11, 12) differ in terms of their flow cross-section.

Description

[0001] Sustainable rotary vane vacuum pump

[0002] Technical field of the invention

[0003] The invention relates to an improved oil-lubricated rotary vane vacuum pump with a rotor in a rotary vane chamber, wherein the inner wall of this rotary vane chamber has at least one oil pocket with at least two oil pocket sections ("stepped oil pocket"), wherein the one or more oil pockets extend along the circumference of the inner wall of the rotary vane chamber, and wherein the oil pocket sections differ in their flow cross-section. In a preferred embodiment, the rotary vane chamber is cylindrical.

[0004] Rotary vane vacuum pumps have a pumping stage with a housing in which a cylindrical rotor is eccentrically arranged in a preferably cylindrical rotary vane chamber. In addition to the preferred circular cross-section, the rotary vane chamber can also be based on an oval, an ellipse, or more generally on a continuous, symmetrical, numerically defined curve. Only the preferred shape (cylindrical rotary vane chamber) is described below; however, the invention is not limited to this. The cylinder, together with the (cylindrical) covers, forms the housing into which the working medium flows and is subsequently compressed and expelled. The axis of the eccentrically mounted rotor runs parallel and offset to the axis of the rotary vane chamber. The rotor has one or more vanes. These vanes are arranged so that they can slide in slots in the rotor, with the slots being aligned approximately radially in cross-section.The vanes are pressed against the inner wall of the rotary vane chamber by the rotation of the rotor due to centrifugal force. During operation of the vacuum pump, the rotor rotates radially offset from the center axis of the cylindrical rotary vane chamber. This creates closed discharge chambers separated by the radially movable vanes, whose size changes during one rotation of the rotor. The change in size of the discharge chambers during operation of the vacuum pump results in pressure differences between the individual discharge chambers and thus between the inlet and outlet sides of the rotary displacement pump.

[0005] A typical rotary vane vacuum pump has three vanes in three slots, defining three discharge chambers. Rotary vane vacuum pumps with more or fewer vanes, slots, and discharge chambers are also conceivable. For example, rotary vane vacuum pumps with two vanes, slots, and discharge chambers are also conceivable.

[0006] Oil-lubricated rotary vane vacuum pumps are characterized by the fact that oil is introduced into the pumping stage or rotary vane chamber. This oil clogs the gaps between the various components, particularly between the vanes and the walls of the rotary vane chamber. This impedes gas exchange between the various pumping chambers. This allows higher vacuums to be achieved during operation than is possible with dry-running rotary vane vacuum pumps.

[0007] The inner wall of the rotary vane chamber of rotary vane vacuum pumps typically has one or more oil pockets. The inner wall of the rotary vane chamber of large rotary vane vacuum pumps preferably has several oil pockets, while the inner wall of the rotary vane chamber of smaller pumps often has only one oil pocket.

[0008] Oil pockets are depressions in the inner wall of the rotary vane chamber. Oil pockets allow the theoretically separate delivery chambers to communicate with each other, as the oil pockets create a channel between the delivery chambers, which the gas uses to equalize pressure. The oil pockets extend along the circumference of the inner wall of the rotary vane chamber and have an axial extension ("width"). As the suction pressure decreases, more and more oil is pumped into the pump stage or the rotary vane chamber due to the increasing pressure difference between the separator and the pumping stage. Oil pockets create a volume into which the oil can escape. This prevents attempted oil compression by the vanes, known as oil hammer, when suction pressures reach close to the ultimate pressure. This reduces the forces acting on the vane(s) and minimizes pump noise.

[0009] In addition, the oil pockets also have the function of collecting the oil and thus ensuring sufficient lubrication of the components in the pumping stage.

[0010] The problem is that at intake pressures < approx. 600 mbar, significant backflow losses occur due to the oil pockets, which result in increased energy requirements: When the outlet valve is closed, the pressure in the upstream delivery chamber is always higher than in the downstream delivery chamber. During compression, the gas uses the oil pocket to escape into the downstream delivery chamber with its lower pressure. Once there, the gas is compressed again due to the rotor movement and escapes into the next downstream delivery chamber. The constant backflow increases the losses and therefore the energy requirements of the vacuum pump in this intake pressure range. This means that if long and deep oil pockets are used, in the range of low intake pressures these cause gas backflow via the oil pocket itself because they form a channel between the chambers, which leads to energy losses.

[0011] The object of the present invention is therefore to reduce energy consumption at low intake pressures, especially at intake pressures < 600 mbar. State of the art

[0012] In the state of the art, this problem is solved by shortening the oil pockets. While this optimizes energy consumption in the pressure range between ultimate pressure and 600 mbar, it simultaneously increases energy consumption at intake pressures above 600 mbar because short and shallow oil pockets cause overcompression at higher intake pressures. Since the oil pockets are usually connected to the outlet channels of the pumping stage, they determine the point in time at which the gas can escape at high intake pressures. This is because before the actual outlet channels are reached, the delivery chamber is already at overpressure compared to the atmosphere, and the gas uses the oil pocket to escape into the leading delivery chamber and flow out. If the oil pockets are shortened, the enclosed delivery chamber reaches them at a later point in time within the rotor rotation than would be the case with longer oil pockets.Up to this point, the gas is compressed. This means that the gas has already reached the pressure required for escape before reaching the oil pocket. However, since the geometry prevents the gas from escaping, it is unnecessarily compressed during further rotation, leading to energy losses. Shortening the oil pocket simultaneously results in significantly higher compression, known as overcompression, at intake pressures above 600 mbar.

[0013] A further object of the invention is therefore to optimize the energy consumption over the entire range of intake pressures, i.e. the pressures from final pressure to atmospheric pressure.

[0014] Description of the invention

[0015] The subject matter of the invention is an oil-lubricated rotary vane vacuum pump 1 with at least one pumping stage 2 with a housing 3 having a rotor 4 in a rotary vane chamber 13, wherein the inner wall 5 of this rotary vane chamber has a distance R0 from the center of this rotary vane chamber, characterized in that the rotary vane chamber 13 has at least one oil pocket 9 with at least two oil pocket sections 11 and 12 on the inner wall 5, wherein the one or more oil pockets 9 extend along the circumference of the inner wall 5 of the rotary vane chamber, and wherein the oil pocket sections 11 and 12 differ in terms of their flow cross-section. The inner wall of the rotary vane chamber is preferably cylindrical.

[0016] The invention will now be described with reference to the preferred embodiment of the oil-lubricated rotary vane vacuum pump according to the invention, in which the rotary vane chamber is cylindrical. However, the invention is not limited to this embodiment. As already mentioned above, in addition to the preferred circular cross-section, the rotary vane chamber can also be based on an oval, an ellipse, or more generally on a continuous, symmetrical, numerically defined curve. In this case, the distance R0 of the inner wall of the rotary vane chamber from the center of the rotary vane chamber will vary (R01, R02, R03, etc.). It will also be clear to those skilled in the art in this case that the distances of the individual oil pocket sections R1 and R2 from the center of the rotary vane chamber satisfy the conditions for the respective distance specified below, i.e., R11 > R21 > R01 or R12 > R22 > R02, etc.

[0017] In a preferred embodiment, the oil pocket 9 has two oil pocket sections 11 and 12. The inner wall 14 of the first oil pocket section 11 of the oil pocket preferably has a maximum distance R1 from the center of the rotary valve chamber, and the inner wall 15 of the second oil pocket section 12 of the oil pocket preferably has a distance R2 from the center of the rotary valve chamber, where R1 is greater than R2 and R2 is greater than R0 (R1 > R2 > R0), with the first oil pocket section 11 merging into the second oil pocket section 12. Since the oil pocket extends along the circumference of the inner wall 5 of the rotary valve chamber, the "length of the oil pocket section" is to be understood as its radian dimension (see Fig. 3). I.e. the first oil pocket section 11 extends over the radian dimension d1, and the second oil pocket section 12 over the radian dimension d2.

[0018] The beginning and end of the oil pocket are the points at which the distance to the center of the rotary valve chamber deviates from RO.

[0019] Depending on the process used to produce the oil pocket—i.e., casting or milling—the inlet and / or outlet of the oil pocket will be more or less flat, i.e., the transition from RO to R1 or R2 will be shorter or longer. This also applies to the transition from one oil pocket section to the other.

[0020] The "flow cross-section" is the area of ​​the cross-sectional area of ​​the oil pocket section, i.e., the area used by the gas and oil to flow from one production chamber to the other. The volumes of the at least two oil pocket sections can be the same or different. If more than two oil pocket sections are present, the oil pocket sections differ from each other in terms of their flow cross-section.

[0021] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, the volume of an oil pocket I with two oil pocket sections is 15-35 vol.%, preferably 20-30 vol.%, smaller than the volume of a conventional oil pocket II without two oil pocket sections in a conventional rotary vane vacuum pump with the same overall length and the same axial extent of the two oil pockets I and II. The first oil pocket section of the oil pocket I and the oil pocket II each have a distance R1 from the center of the rotary vane chamber over their length, while the second oil pocket section of the oil pocket I has a distance R2 from the center of the rotary vane chamber over its length, where R1 > R2 > RO.

[0022] It is also conceivable that the flow cross-section within the individual oil pocket sections varies continuously, i.e., without gradations, but that the two oil pocket sections 11 and 12 can still be clearly distinguished in their flow cross-sections by the discontinuous gradation. Their shape could then be described using other mathematical forms such as straight lines and splines.

[0023] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, the flow cross-section of the oil pocket section 11 is larger than the flow cross-section of the oil pocket section 12.

[0024] It is understood that the inner wall 5 of the rotary valve chamber can also have several such oil pockets 9, wherein individual or several oil pockets can each be designed differently or identically.

[0025] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, the oil pockets 9 present all have the same orientation, ie, the oil pockets 9 are aligned next to one another on the inner wall 5 of the rotary vane chamber along a direction parallel to the circumferential direction. This is the case, for example, in the arrangement of the oil pockets shown in Fig. 4.

[0026] The one or more oil pockets 9 can have a straight or curved shape along their length. "Straight" in this context means along a direction at a 90° angle to the rotor axis. "Curved" means that the oil pocket deviates from this direction in its length. It is also conceivable for oil pockets with a straight shape and oil pockets with a curved shape to be present next to one another. Preferably, at least one oil pocket 9 is connected to an outlet channel 10. Preferably, the first oil pocket section 11 is connected to an outlet channel 10. In a further preferred embodiment of the invention, the oil pocket section 11 is provided with two outlet channels 10 and 10 1 tied together.

[0027] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, two or more oil pockets have the same "width," ie, the same axial extent. In a particularly preferred embodiment, the oil pockets connected to one or more outlet channels are wider than the oil pockets not connected to an outlet channel. In a further embodiment, the width of the oil pockets not connected to an outlet channel decreases with increasing axial distance from the outlet channel.

[0028] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, two or more oil pockets have the same total length d. In a particularly preferred embodiment, the oil pockets connected to an outlet channel have the same total length d, whereby any additional oil pockets not connected to an outlet channel may be shorter.

[0029] In a further embodiment, the oil pockets connected to an outlet channel have the same total length d, with further oil pockets present that are not connected to an outlet channel being longer.

[0030] If a rotary vane vacuum pump according to the invention, in particular a rotary vane vacuum pump according to Fig. 2 or Fig. 4, is operated, more and more oil is pumped into the pump stage as the intake pressure decreases due to the increasing pressure difference between the separator and the pump stage. By means of the oil pockets according to the invention, a volume is formed into which the oil can escape in order to prevent an attempted oil compression by the vanes, the so-called oil hammer, when intake pressures close to the ultimate pressure are reached. This leads to fewer forces on the vane(s) and to a reduction in pump noise. At intake pressures < approx. 600 mbar, gas backflow via the oil pocket is still possible; however, due to the two oil pocket sections and their special stepped geometry, the gas backflow is reduced compared to rotary vane vacuum pumps with conventional oil pockets, i.e.This compares to rotary vane vacuum pumps with oil pockets of the same overall length and a consistent depth, corresponding to the depth of the deeper oil pocket section of the oil pocket according to the invention. This means that the shallower oil pocket sections of the oil pockets make it more difficult for the gas to flow back from the upstream to the downstream pumping chamber. Due to this reduced gas backflow, the energy requirement is reduced.

[0031] At intake pressures above 600 mbar, the gas reaches the pressure required for discharge even before reaching the oil pocket. Since the geometry of the inventive oil pockets allows the gas to escape, the energy requirement is also reduced compared to conventional rotary vane vacuum pumps.

[0032] Since less energy is required to operate a rotary vane vacuum pump according to the invention than to operate a conventional rotary vane vacuum pump, the rotary vane vacuum pump according to the invention is sustainable.

[0033] A further advantage is an improvement in the noise level when starting the pump, i.e., the pump according to the invention is quieter when starting than a conventional rotary vane vacuum pump. Further important features and advantages of the invention emerge from the dependent claims, the drawings, and the associated description of the figures with reference to the drawings.

[0034] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0035] Preferred embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. The inventive inner wall of the rotary vane chamber is shown as an example in a rotary vane vacuum pump with one pumping stage, but can also be implemented in rotary vane vacuum pumps with two or more pumping stages. In rotary vane vacuum pumps with more than two pumping stages, the oil pockets can be installed in just one pumping stage, in several, or in all pumping stages.

[0036] The drawings show the preferred embodiment of the inventive oil-lubricated rotary vane vacuum pump with a cylindrical rotary vane chamber. However, the invention is not limited thereto.

[0037] Short description of the drawings

[0038] Fig. 1 shows a side view of a rotary vane vacuum pump according to the invention without a view of the cylinder cover.

[0039] Fig. 2 shows a cross section of a rotary vane vacuum pump according to the invention, with the arrow at the top showing the inlet and the arrow on the left showing the outlet.

[0040] Fig. 3 shows the enlarged detail B from Fig. 2 (3x magnification). Fig. 4 shows the section along line CC in Fig. 1. Here, the parallel alignment of the oil pockets next to each other, i.e., along a direction parallel to the circumferential direction, is clearly visible.

[0041] Preferred embodiments of the invention

[0042] In all figures, identical or functionally identical elements and devices have been provided with the same reference numerals, unless otherwise stated.

[0043] Fig. 1 shows the structure of a conventional pumping stage of a rotary vane vacuum pump, wherein a rotor 4 is arranged eccentrically in a cylindrical rotary vane chamber 13 with an inner wall 5. The vanes 616'16" are arranged in slots 7 / 7 ' / 711 which thus determine the conveying chambers 818'18".

[0044] Fig. 2 shows the cross-section of the pumping stage of a rotary vane vacuum pump according to the invention. As in Fig. 1, the rotor 4 arranged in the cylindrical inner wall 5 of the rotary vane chamber 13 can be seen here, with the vanes 616'16", slots 717'17" and the delivery chambers 818'18". The oil pocket 9 with two oil pocket sections 11 and 12 can be clearly seen, one of the two oil pocket sections 11 and 12 being connected to the two outlet channels 10 / 10. 1 In the present preferred case, the deeper oil pocket section 11 is connected to the outlet channels.

[0045] The oil pockets 9 shown in Fig. 2, Fig. 3 and Fig. 4 have two oil pocket sections 11 and 12. Oil pockets with three or more oil pocket sections are also conceivable. Details on the position and shape of the oil pockets can be found in Fig. 4. Fig. 4 shows a preferred embodiment for an inner wall of a rotary valve chamber 13, which has eight oil pockets 9 1 , 9", 9 111 , 9 IV , 9 V , 9 VI , 9 VI1 , and 9 VHI with a straight shape. The oil pockets 9 111 , 9 IV , 9 V and 9 VI connected to the outlet. These oil pockets preferably have 9 111 , 9 IV , 9 V and 9 VI an axial extension b1. In addition, four further oil pockets 9 1 , 9", 9 VI1 and 9 VHI which are not connected to the outlet. Preferably, the oil pockets have 9" and 9 V " an axial extension b2 and the oil pockets 91 and 9 VI " has an axial extension b3, where b1 is greater than b2 and b2 is greater than b3 (b1 > b2 > b3). In a particularly preferred embodiment, the ratio of b1 to b2 to b3 = 6 : 5 : 4.

[0046] The Oil Bags 9 1 , 9", 9 111 , 9 IV , 9 V , 9 VI , 9 V ", and 9 VI " are - as can be seen in Fig. 4 - arranged next to one another on the inner wall 5 of the rotary valve chamber 13 along a direction parallel to the circumferential direction and preferably have the same overall length d and the same arc masses of the first and second oil pocket sections 11 and 12. The ratio of the arc mass d1 of the first oil pocket section 11 to the arc mass d2 of the second oil pocket section 12 is preferably in the range of (1 -2) to 1, particularly preferably in the range of (1.3 - 1.8) to 1, particularly preferably 1.5:1.

[0047] The figures show a cylindrical rotary valve chamber with a cylindrical rotor. The rotary valve chamber is therefore based on a circular cross-section. However, instead of a circle, the rotary valve chamber could also be based on an oval, an ellipse, or, more generally, on a continuous, symmetrical, numerically defined curve.

[0048] Measurement of energy savings in oil-lubricated rotary vane vacuum pumps with the inventive stepped oil pockets. The measurement of power savings by modifying the oil pocket geometry is carried out in two experiments on two rotary vane vacuum pumps with a nominal pumping speed of 100m 3 / h, wherein one rotary vane vacuum pump has conventional oil pockets and the other rotary vane vacuum pump has oil pockets according to the invention.

[0049] Result The stepped oil pocket geometry ensures the rotary valve

[0050] Vacuum pump for a shorter evacuation process and low energy consumption per cycle compared to a rotary vane vacuum pump with conventional oil pockets.

[0051] 1 oil-lubricated rotary vane vacuum pump

[0052] 2 pump stages

[0053] 3 housings

[0054] 4 Rotor

[0055] 5 Inner wall of the rotary valve chamber

[0056] 6, 6 1 , 6" slider

[0057] 7, 7 1 , 7" slot

[0058] 8, 8 1 , 8" feed chamber

[0059] 9i 911.9m, giv9v, gvi9vii 9V111 oil bag

[0060] 10, 10 1 exhaust channel

[0061] 11 First oil pocket section of the oil pocket

[0062] 12 Second oil pocket section of the oil pocket

[0063] 13 Rotary valve room

[0064] 14 Inner wall of the first oil pocket section of the oil pocket

[0065] 15 Inner wall of the second oil pocket section of the oil pocket

Claims

Claims 1. Oil-lubricated rotary vane vacuum pump (1) with at least one pumping stage (2) with a housing (3) having a rotor (4) in a rotary vane chamber (13), wherein the inner wall (5) of the rotary vane chamber has a distance R0 to the center of the rotary vane chamber, characterized in that the inner wall (5) of the rotary vane chamber has at least one oil pocket (9) with at least two oil pocket sections (11) and (12), wherein the one or more oil pockets (9) extend along the circumference of the inner wall (5) of the rotary vane chamber (13), and wherein the oil pocket sections (11) and (12) differ in terms of their flow cross-section.

2. Oil-lubricated rotary vane vacuum pump (1) according to claim 1, characterized in that the flow cross-section of the oil pocket section (11) is larger than the flow cross-section of the oil pocket section (12).

3. Oil-lubricated rotary vane vacuum pump (1) according to claim 1 and / or 2, characterized in that the inner wall (14) of the first oil pocket section (11) has a maximum distance R1 from the center of the rotary vane chamber, and the inner wall (15) of the second oil pocket section (12) has a maximum distance R2 from the center of the rotary vane chamber, wherein R1 is greater than R2 and R2 is greater than R0, and wherein the first oil pocket section (11) merges into the second oil pocket section (12).

4. Oil-lubricated rotary vane vacuum pump (1) according to one or more of claims 1-3, characterized in that the at least one oil pocket (9) comprises two oil pocket sections and the circumference of the inner wall of the rotary vane chamber (13) along a Total length d, wherein the length d is composed of the length d1 of the first oil pocket section (11) and the length d2 of the second oil pocket section (12), and the ratio of d1 to d2 is preferably in the range of (1-2) to 1, particularly preferably in the range of (1.3-1.8) to 1, most particularly preferably 1.5:

1.

5. Oil-lubricated rotary vane vacuum pump (1) according to one or more of claims 1-4, characterized in that the rotary vane chamber is cylindrical.

6. Oil-lubricated rotary vane vacuum pump (1) according to one or more of claims 1-5, characterized in that several oil pockets (9) are present.

7. Oil-lubricated rotary vane vacuum pump (1) according to claim 6, characterized in that two or more oil pockets (9) have the same axial extent.

8. Oil-lubricated rotary vane vacuum pump (1) according to one or more of claims 6-7, characterized in that two or more oil pockets (9) have the same total length d.

9. Oil-lubricated rotary vane vacuum pump (1) according to one or more of claims 6-8, characterized in that the oil pockets (9) on the inner wall (5) of the rotary vane chamber (13) are aligned next to one another along a direction parallel to the circumferential direction.

10. Oil-lubricated rotary vane vacuum pump (1) according to one or more of the preceding claims, characterized in that at least one oil pocket (9) is connected to at least one outlet channel (10).

11. Oil-lubricated rotary vane vacuum pump (1) according to claim 10, characterized in that the oil pocket (9) connected to an outlet channel (10) has a greater axial extent than the oil pocket (9 1 ) which is not connected to an exhaust duct.

12. Oil-lubricated rotary vane vacuum pump (1) according to claim e, characterized in that the axial extent b of the oil pockets (9) decreases with increasing axial distance from an outlet channel.

13. Oil-lubricated rotary vane vacuum pump (1) according to claim 6 and / or 11, characterized in that the total length d of the oil pockets (9) decreases with increasing axial distance from an outlet channel.

14. Oil-lubricated rotary vane vacuum pump (1) according to one or more of claims 10-13, characterized in that the first oil pocket section (11) of at least one oil pocket (9) is connected to an outlet channel (10).

15. Oil-lubricated rotary vane vacuum pump (1) according to one or more of claims 10 and 12-14, characterized in that all existing oil pockets (9) are connected to one or more outlet channels.

16. Oil-lubricated rotary vane vacuum pump (1) according to one or more of the preceding claims, characterized in that the oil pockets (9) have a straight or a curved shape.

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