TW202225558A - Sliding vane pump - Google Patents

Abstract

A sliding vane pump, vacuum pump lubricated by such a pump and the vane for a sliding vane pump are disclosed. The sliding vane pump comprises: a rotor rotatably mounted within a stator. The rotor comprises at least one vane slidably mounted within a corresponding at least one cavity, at least one end surface of the vane being configured to abut with an inner wall of the stator. The rotor, stator and at least one vane define a plurality of variable volume pumping chambers for conveying fluid from a fluid inlet to a fluid outlet on rotation of the rotor, the at least one vane separating adjacent pumping chambers. The pump further comprises a channel configured to provide a passage between the adjacent pumping chambers.

Description

Sliding Vane Pump

The field of the invention is that of sliding vane pumps, vanes used in such pumps and a vacuum pump lubricated by such a pump.

Sliding vane pumps are used to pump liquids such as oil. It can be used in conjunction with a vacuum pump to lubricate the shaft and drive the inlet valve. These pumps operate at high rotational speeds and have a variable volume pumping chamber formed by the rotor, vanes and inner walls of the stator. The variable volume pump chamber draws lubricant into the chamber through the inlet and compresses the lubricant as it moves the lubricant from the inlet to one of the pump's outlets.

In such a pump, a cavitation problem in the fluid occurs especially when the density of the fluid being pumped and the rotational speed of the rotor are high. Cavitation is a phenomenon in which a rapid pressure change in one of the liquids results in the formation of small vapor-filled cavities in lower pressure regions. When the pressure in these areas increases, the bubbles collapse and generate strong shock waves in the vicinity of the bubbles, which cause the pump to vibrate and be noisy.

Chemical-resistant lubricants, such as PTFE lubricants, are increasingly used in vacuum pumps for pumping corrosive chemicals from semiconductor chambers. These lubricants have a high density that is nearly twice that of a mineral oil, and the problem of cavitation in these pumps is increasing.

It is desirable to suppress cavitation in sliding vane pumps.

A first aspect provides a sliding vane pump, the pump comprising: a rotor rotatably mounted in a stator; the rotor comprising at least one vane slidably mounted in a corresponding at least one cavity, the vane At least one end face is configured to abut an inner wall of the stator; the rotor, stator and at least one vane define a plurality of variable volume pumps for delivering fluid from a fluid inlet to a fluid outlet after rotating the rotor chambers, the at least one vane separating adjacent pump chambers; and a channel configured to provide a passageway between the adjacent pump chambers.

The inventors are aware of potential problems associated with sliding vane pumps for pumping fluids such as oil. These pumps create a region of lower pressure as the volume of the pumping chamber increases and draw fluid into the pumping chamber through the inlet. The pumping chamber then reduces in volume towards the outlet and the fluid is compressed and discharged through the outlet. In some situations (such as if the pump is rotating at a high speed and/or the fluid is particularly dense), air bubbles can form in the lower pressure regions and this can result in the formation of the lower pressures therein Cavitation in which bubbles collapse during compression of the fluid. Cavitation in a pump causes excessive noise and vibration and should be avoided as much as possible. Providing a fluid communication channel between adjacent pump chambers that allows fluid to flow from a higher pressure region in one pump chamber to a lower pressure region in an adjacent pump chamber allows the lower pressures to be relieved Excessive pressure drop in the zone and suppress bubble formation in a simple, inexpensive and robust way.

But there may be a technical bias against providing one of the channels that allows fluid communication between the pumping chambers, as this reduces pumping efficiency and actually causes leakage. If cavitation can be a problem, providing a via with a controlled predetermined, constrained size such that controlling the leakage to a desired value provides an efficient solution to the cavitation problem. A passage through or around a vane can be easy to manufacture and provide a solution for defining the size of the passage relatively independent of the tolerances of the pump assembly.

One or more vanes are longitudinal elements mounted to slide along a longitudinal axis in a corresponding shaping cavity within the rotor. This sliding movement allows the creation of a variable volume pumping chamber as the rotor rotates eccentrically within the stator.

Although the channel providing the passageway between adjacent pumping chambers can be formed in different ways, in some embodiments the channel is formed in the at least one vane.

In some embodiments, the channel includes a groove in an end face of the blade, at least a portion of the end face abutting the inner stator wall.

A simple and convenient way of providing the channel may be to provide it as a groove in the end face of the blade.

In some embodiments, the at least one end face is curved to provide a sealing surface with the inner stator wall.

The groove provides an indentation in the sealing surface that forms a channel therethrough connecting adjacent pump chambers and provides a passage between the leading and trailing edges of the vane during operation of the pump.

In other embodiments, the channel includes a passage within the vane.

An alternative could be to provide the channel as a passageway extending through the vane. Because the vane is a vane that extends away from a cavity in the rotor by different amounts depending on where the rotor is eccentrically mounted, the passageway is configured to even when the vane is in a recessed position opposite an extended position is located within a portion of the blade that is not shielded by the cavity of the rotor.

Alternatively and/or additionally, the channel may comprise a groove in the inner stator wall.

The location of the channel may be in the rotor or stator wall or both, the actual location of the channel is immaterial if a passage is provided that allows some flow between the pumping chambers. The amount of flow provided depends on the size of the passage. Making a passage or a channel allows the bypass path between the chambers to be accurately controlled and relatively independent of other tolerances of the pump. The size of the passage may be selected to provide a desired bypass flow rate sufficient to inhibit cavitation without unduly hindering the performance of the pump. This will depend to some extent on both the density of the fluid to be pumped and the rotational speed of the pump. Although the channel may be machined in the inner stator wall, it may be preferred to provide the channel in the blade because it may be easier to manufacture.

In some embodiments, both end faces of the vane include grooves that form channels between the pumping chambers.

Although there may be a plurality of individual vanes extending from individual grooves or cavities of the rotor, in some embodiments the vanes may extend through the rotor or radial pairs of ends of the vanes abutting the inner wall of the stator set the surface. The vane slides within the cavity and both ends of the vane include a channel in the form of a groove.

In some embodiments, the rotor is mounted for eccentric rotation within the stator.

The center of rotation of the rotor can be offset relative to the center of the chamber formed by the inner wall of the stator so that as it rotates its movement is eccentric relative to the inner wall of the stator.

In some embodiments, a cross-section of at least a portion of a length of the vane includes a protrusion protruding from an outer surface and cooperating with a corresponding shaped cavity in the rotor to inhibit twisting of the vane about its longitudinal axis .

In order for the vane to provide the passage between the leading edge and the trailing edge during rotation, the vane should be restrained from twisting or rotating about its longitudinal axis so that the entrance of the passage remains aligned with the pumping chambers into which it leads . This can be accomplished by providing a protrusion that is configured to cooperate with a corresponding shaping cavity in the rotor. The protruding portion may extend from the longitudinally extending side surface of the blade and thus inhibit rotation about a longitudinal axis. In some embodiments, if the channel includes a groove extending in a straight line from a leading edge to a trailing edge, the protrusion protrudes substantially perpendicular to the groove.

However, the pump can be configured to pump several fluids, and in some embodiments, the pump is configured to pump a lubricant.

In some embodiments, the pump is configured to pump a high density lubricant, one of the lubricants having a density greater than 1.5 kg/liter.

Cavitation is a particular problem in a pump when pumping high density fluids and lubricants with a density greater than 1.5 kg/liter can trigger cavitation in sliding vane pumps, making embodiments particularly suitable for such pumps.

In some embodiments, the channel includes a cross-section between 1 mm ² and 2 mm ² .

The size of the channel required to inhibit cavitation will depend on the density of the fluid being pumped and the rotational speed of the pump. The channel should be sized to avoid too much drop in pumping efficiency but should be sufficient to allow some pressure relief and inhibit cavitation. In many cases, a cross-section between 1 mm ² and 2 mm ² will provide the flow required to inhibit cavitation without unduly affecting the performance of the pump.

In some embodiments, the channel is sized such that a final pressure reduction of between 5% and 15% can be achieved by the pump.

As previously mentioned, the channel will reduce the final pressure that can be achieved by the pump but will have the advantage of inhibiting cavitation. It has been found that a channel size selected such that the final pressure achievable by the pump is reduced by a limited amount provides effective reduction of cavitation while still providing an efficient pump.

In some embodiments, there may be a plurality of channels. In some embodiments, these may be in the form of grooves in the end face of the blade.

In some embodiments, the channel forms a substantially straight path between the two pumping chambers, while in other embodiments, the channel may not be straight.

Having a single channel and having it formed as a straight channel can have the advantage of ease of manufacture. However, there may be embodiments in which two or more channels are provided and/or in which the channels form a more complex inclined path.

In some embodiments, the pump includes a lubricant pump for driving a valve and supplying lubricant to a vacuum pump.

The oil pump for supplying lubricant to the vacuum pump can be mounted on the same shaft as the vacuum pump and thus its rotational speed is set by the rotational speed of the vacuum pump and can be very high. Furthermore, vacuum pumps are often used to pump corrosive chemicals and thus the lubricants within these pumps need to be resistant to these chemicals, the lubricants can have a high density. Thus, the cavitation problem occurs in such pumps due to vacuum pumps and embodiments may provide a particularly efficient solution to this.

In some embodiments, a largest portion of the vane includes a circular cross-section; and at least one further portion of the vane includes a non-circular cross-section.

A second aspect provides a sliding vane pump, which includes a rotor rotatably mounted in a stator; the rotor includes at least one vane slidably mounted in a corresponding at least one cavity; the rotor, the stator and at least one one vane defines a plurality of variable volume pump chambers for delivering fluid from a fluid inlet to a fluid outlet after rotating the rotor, the at least one vane separates adjacent pump chambers; and a largest portion of the vane has a circular cross-section; at least one further portion of the blade has a non-circular cross-section.

A circular cross-section of the main part of the blade means that the corresponding part of the cavity in which the blade slides has a corresponding circular cross-section. This results in easier to machine and stronger parts. However, a circular cross-section means that axial rotation or twisting of the blade occurs. The heads of the vanes have a shape that needs to remain aligned with the inner wall of the stator to provide an effective seal. Therefore, maintaining the head in alignment requires some method to restrain the blade from rotating. This problem is solved by providing a portion of the blade with a non-circular cross-section that allows preventing the rotation of the blade. The majority of the blade has a circular cross-section that allows easier machining of both the blade and the cavity in the rotor into which the blade is inserted. Only a portion has a non-circular cross-section, because inhibiting axial rotation of a portion of the vane will inhibit axial rotation of the entire vane.

In some embodiments, the at least one further portion is located at one end of the blade.

In some embodiments, a cross-section of an annular groove in the stator configured to receive the vane includes a non-circular cross-section corresponding to the non-circular cross-section of the vane.

The non-circular portion may advantageously be located at one end of the vane and in some cases be the portion of the vane that extends away from the rotor cavity when the rotor is at its position furthest from the inner stator wall. The stator inner wall is provided with an annular groove having a corresponding non-circular cross-section and this maintains the vanes in a particular alignment and inhibits axial rotation as the vanes extend away from the rotor into the stator.

In some embodiments, the at least one further portion is located at both ends of the blade.

If the vane extends through the rotor, both ends of the vane may advantageously have a non-circular cross-section, such that at any one time at least one end of the vane will extend into a corresponding shaped stator and thus at At least one end of the blade, and thus the entire blade, is prevented from rotating at any one time.

In some embodiments, the at least one cavity within the rotor includes a circular cross-section along a length of the cavity.

If the non-circular cross-sectional portion of the vane is at both ends, it is the end portion of the vane and the corresponding stator shape that prevents axial rotation of the vane and the cavity in the rotor may be circular along its entire length . This makes it easier to manufacture.

In other embodiments, a portion of the cavity within the rotor may have a non-circular cross-section and a largest portion has a circular cross-section.

In some embodiments, the rotor includes an additional anti-rotation component mounted in a portion of the rotor cavity configured to receive the at least one further portion of the blade.

In some embodiments, the non-circular cross-sectional portion of the cavity may not be formed within the rotor itself but may be formed by an additional component such as a pin extending across the cavity. In some embodiments, the pin may be located at one end of the cavity, the pin obscuring a portion of the circular cross-section and positioned such that it is located where the non-circular cross-sectional portion of the vane is housed and hinders rotation of the vane part of the cavity. This may be desirable if the vane does not extend through the rotor and has only one end with a non-circular cross-section.

In some embodiments, the non-circular cross-section is smaller than the circular cross-section.

It may be advantageous if the non-circular cross-section of the blade is smaller than the circular cross-section, as this allows it to be machined from a circular cross-section portion. Furthermore, it can fit in a circular cross-section cavity within the rotor and only a small portion of the cavity has a corresponding non-circular portion for hindering rotation. This allows simple machining of the cavity and the addition of an additional anti-rotation component, such as a pin, to the machined cavity.

In some embodiments, the at least one further portion includes at least one concave section machined from an outer surface of the blade.

As mentioned earlier, if the non-circular cross-section is smaller than the circular cross-section, the non-circular cross-section can be machined from the outer surface to form a concave cross-section.

In some embodiments, the at least one recessed section includes a flat axially extending surface.

A flat axially extending surface can be used to inhibit axial rotation and facilitate machining. In this regard, the corresponding flat surface of the groove or cavity into which the vane extends may be located within the rotor or, if the recessed cross-section is at one or both ends of the vane, the end of the vane extends into the corresponding plastic in which it extends. A shaped groove will be located in the stator of the pump. This may be easier to machine than machining a shape into a cavity in the rotor.

A third aspect provides a vacuum pump including a sliding vane pump according to a first aspect or a second aspect for supplying lubricant to the vacuum pump.

A fourth aspect provides a vane for a sliding vane pump according to a first aspect, the vane being configured to be slidably mounted in a corresponding cavity in a rotor and extending from the cavity such that during installation At least one end face of the vane abuts an inner stator wall when in the rotor in the pump and thereby separates adjacent pumping chambers; the vane includes a configuration configured to provide the phases when the vane is installed in the pump A channel between adjacent pump chambers.

In some embodiments, the channel includes a groove in the at least one end face.

In other embodiments, the channel includes a passageway extending from a leading edge of the blade to a trailing edge when the blade is installed in the rotor.

A fifth aspect provides a vane for a sliding vane pump according to a second aspect, the vane being configured to have a substantially circular cross-section for a larger portion of a length of the vane and For a non-circular cross-section of a smaller portion of a length of the vane, the vane is configured to be slidably mounted within a corresponding shaped cavity in a rotor and to extend from the cavity so as to be slidably mounted in the rotor At least one end face of the vane abuts an inner stator wall when in the rotor of the pump and thereby separates adjacent pumping chambers.

In some embodiments, the vane includes a channel that is configured to provide a passage between the adjacent pumping chambers when the vane is installed in the pump.

In some embodiments, the at least one channel is located in at least one of the end faces.

Further specific and preferred aspects are set forth in the accompanying independent and dependent claims. The features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combinations other than those expressly stated in the scope of the application.

If a device feature is described as being operable to provide a function, it should be understood that this includes a device feature that provides that function or is adapted or configured to provide that function.

Before discussing the embodiments in more detail, an overview will first be provided.

Figure 1 shows a section through a sliding vane pump. In this pump, there is a rotor 40 mounted to rotate eccentrically within a stator 50 . The rotor 40 has mounted therein a vane 10 that is configured to contact the inner wall of the stator 50 and slide within the rotor as it rotates. The pumping chamber is formed between the vanes, the inner wall of the stator and the outer wall of the rotor. Rotation of the rotor pushes oil from an inlet 30 towards an outlet 20 after counterclockwise rotation of the rotor 40 .

Although in this embodiment only a single vane is shown extending across the diameter of the rotor, in other embodiments there may be two or more that are mounted in correspondingly shaped grooves at different locations in the rotor The vanes are biased to extend from their grooves and contact the inner stator wall. The vanes, rotor and inner stator walls form the pumping chamber.

In this embodiment, there are anti-rotation components in the form of pins 41 extending across a portion of the circular cross-section at either end of the cavity in the rotor housing the blades. In an otherwise circular cross-section, the vane 10 has grooves in portions at either end. These grooves slide against the pin so that the pin inhibits axial rotation of the vane. In other embodiments, such as the embodiment shown in FIGS. 3 and 4 , the cross-sectional shape of the stator receiving the vanes matches the non-circular shape of the ends of the vanes and this is sufficient to eliminate the need for additional non-rotating components such as pins 41 . In this case, the rotation of the blades is suppressed. However, in embodiments where the vanes do not extend through the stator (not shown in the figure), the rotor will be required when the rotor is in a position where the vanes do not extend out of the cavity (the position on the left hand side of the vanes in this figure). An anti-rotation component within the cavity itself or a change in the shape of the rotor cavity to inhibit rotation.

FIG. 2 shows an end view of the pump of FIG. 1 and shows an exhaust pipe leading to exhaust outlet 20 and an inlet machining aperture leading to inlet 30 . A pressure limiter 60 is also shown. In this embodiment, a sliding vane pump is used to supply lubricant to a vacuum pump, one of the lubricant pumps. The pressure limiter 60 controls the pressure of lubricant supplied to the vacuum pump. In this embodiment, the rotor of the vane pump is mounted on the same shaft as the rotor of the vacuum pump and therefore rotates at the same high speed. The temperature of the pump will rise during operation and will affect the viscosity of the lubricant and the pressure of the lubricant supplied to the vacuum pump. The pressure limiter 60 is used to control the supply of lubricant to the vacuum pump.

Some components of the sliding vane pump are shown in FIGS. 3 and 4 . FIG. 3 shows a stator or cylinder 50 of a pump including an annular ring having a sealing surface 52 and an anti-rotation surface 53 configured to correspond to the truncated circular cross-sectional shape of the end portions of the vanes shown in FIG. 4 grooves or grooves. These corresponding non-circular shapes inhibit axial rotation of the vanes. The main portion of the vane has a circular cross-section corresponding to the cross-section extending through the cylindrical cavity of the rotor.

FIG. 4 shows the rotor 40 with the vanes 10 . The vanes are shown separately from the rotor and are installed therein. The blade on the left-hand side includes a circular cross-section for most of its length with a concave end portion that mates with a similarly shaped surface 52 in the stator 50 of FIG. 3 to thereby hinder rotation of the blade about its longitudinal axis. . In the right hand view there is a side portion which protrudes from one of the longitudinal side surfaces of the vane and further prevents the vane from twisting or rotating about its longitudinal axis when mounted in a corresponding shaping cavity in the rotor.

Figure 5 shows the pump cylinder or stator 50 mounted on the rotor. It also shows the shaft 42 on which the rotor is mounted.

Figure 6 shows the end face 8 of the blade 10 in more detail. The upper left view of FIG. 6 shows a vane of an embodiment of a second aspect in which the end face 8 forms a sealing surface for sealing with the inner wall 52 of the stator to isolate the pumping chambers from each other. The sealing surface is curved to correspond to the curved inner wall 52 of the pump cylinder or stator 50 (see Figure 3). There is a groove in one side towards the end exhibiting a non-circular cross-section. This corresponds to the non-circular cross-sections of the pump cylinders in the stator and these corresponding non-circular cross-sections prevent the vanes 12 from rotating about their longitudinal axes.

The upper right figure shows a similar embodiment in which there is a channel 12 within the end face 8 of the vane 10 that provides a passage between adjacent pumping chambers separated by the vane and allows fluid to flow from a lower one on one side of the vane The pressure zone passes to a higher pressure zone on the other side of the vane, and the fluid flow inhibits the formation of air bubbles in the lower pressure zone. Channel 12 is configured such that it provides a path between the leading and trailing edges of the vanes and a bypass passage between adjacent pumping chambers in operation of the pump. It should be noted that forming the channel 12 on the end face of the blade is easy to manufacture, inexpensive and robust. An alternative may be to include a passageway having a cylindrical form extending through a portion of the blade extending from a groove or cavity in the rotor in substantially all positions of the rotor. Alternatively, the channel 12 may be formed as a groove in the inner stator wall rather than the vanes themselves.

The lower diagram in FIG. 6 shows example dimensions for this particular embodiment. In this example, the channel in the form of a trench has a width of 1 mm and a depth of 1.4 mm. The overall width of the blades is 4.9 mm and their length is 40 mm. In this embodiment in which the vanes extend through the rotor, the length of the vanes corresponds to the distance between the opposing surfaces 52 of the pump cylinder 50 .

Figure 7 shows a section through a pump with one of the rotors in different positions. The arrows show the counterclockwise direction of rotation of the rotor. Arrow 72 points to a compression chamber, which is the location of the pump chamber where rotation of the rotor reduces the size of the pump chamber and thereby pushes oil out of the chamber towards and through outlet 20 . Chamber 74 is the lower pressure chamber in which the pump chamber is expanded and oil is drawn from inlet 30 into the expansion pump chamber 74 . Region 70 is where cavitation can occur because this is one of the lower pressure regions in the expansion chamber. The passages formed by the grooves 12 in the end faces of the vanes between adjacent pumping chambers provide a flow path for the fluid from the higher pressure region 72 to the lower pressure region 70 where cavitation occurs. This increases the pressure in the lower pressure region and inhibits cavitation. It will be appreciated that this results in a slightly less efficient pump and the size of the channels is chosen to inhibit cavitation but still maintain a desired level of pump efficiency. This level can be set such that the final pressure the pump can produce is reduced by only 15%, preferably less than 10%. In this regard, the pressure produced by the oil pump may in some embodiments be higher than typically required and may be controlled by a pressure limiter as shown in FIG. 2, in which case the final pressure obtainable by the pump may not be acceptable. pressure.

FIG. 8 shows an embodiment in which an oil pump 80 is installed to provide lubricant to a vacuum pump 90 and drive a valve of the vacuum pump 90 . As can be seen, the oil pump is mounted on the shaft 42 of the vacuum pump driven by the motor 95 . The rotation speed of the rotor of the oil pump is set by the requirements of the vacuum pump. Thus, the rotor can rotate at a very high rotational speed, typically about 1500 rpm to 1800 rpm. Additionally, if the vacuum pump is used to evacuate chemically aggressive products (as may be the case in semiconductor processing), the oil or lubricant supplied by the pump 80 is selected to be a chemically resistant one. These lubricants may have a high density, one such lubricant having a density of 1.88 kg/liter. This is greater than twice the density of normal mineral oils and the combination of high pumping speed and high density of the fluid being pumped increases the probability of cavitation that can cause percussion within the pump. Providing channels that allow a restricted fluid flow between adjacent pump chambers inhibits cavitation and can improve pump performance.

Although in the embodiment shown there is a single blade extending through the rotor, it should be understood that in other embodiments the blade may be formed to extend from opposite sides of the rotor and spring biased against the inner stator wall. Two separate leaves. Other embodiments in which there are more pump chambers and more vanes are also contemplated and also benefit from a constrained pressure relief channel between adjacent pump chambers.

Embodiments also provide a method of upgrading a pump in which the vanes are replaced by vanes having a groove or passage to allow a conventional pump to operate at higher speeds and have a higher density of lubricant while still inhibiting cavitation.

Embodiments also provide a method of repairing a vane in which a worn vane is replaced with a vane having a groove or passage.

Although illustrative embodiments of the present invention have been disclosed in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiments and those skilled in the art can make use of the appended claims and their equivalents without departing from the scope of Various changes and modifications of the present invention can be effected within the defined scope of the present invention.

8: End face 10: Slider 12: Channel/Groove 20: Export 30: Import 40: Rotor 41: Pin 42: Shaft 50: Stator/Cylinder 52: Sealing surface/inner wall 53: Anti-rotation surface 60: Pressure Limiter 70: Area 72: Compression chamber/higher pressure area 74: Pump Room 80: oil pump 90: Vacuum pump 95: Motor

Embodiments of the present invention will now be further described with reference to the accompanying drawings, in which: Figure 1 shows a section through a sliding vane pump according to an embodiment; Figure 2 shows an end view of a pump according to an embodiment; Figure 3 shows the stator or cylinder of a pump according to an embodiment; Figure 4 shows the vane and the vane installed in the rotor; Figure 5 shows the cylinder of the pump mounted on the rotor; Figure 6 shows two blades according to various embodiments; 7 shows a cross-sectional view through a pump according to an embodiment with rotors in different positions; and Figure 8 schematically shows a sliding vane pump as an oil pump in a vacuum pump.

12: Channel/Groove

20: Export

30: Import

70: Area

72: Compression chamber/higher pressure area

74: Pump Room

Claims (30)

A sliding vane pump comprising: a rotor rotatably mounted in the stator; the rotor includes at least one vane slidably mounted within a corresponding at least one cavity, at least one end face of the vane being configured to abut an inner wall of the stator; the rotor, stator and at least one vane define a plurality of variable volume pumping chambers for delivering fluid from a fluid inlet to a fluid outlet after rotating the rotor, the at least one vane separating adjacent pumping chambers; and A channel configured to provide a passage between the adjacent pump chambers. The sliding vane pump of claim 1, wherein the passage is formed in the at least one vane. The sliding vane pump of claim 2, wherein the passage includes a groove in an end face of the vane, at least a portion of the end face abutting the inner stator wall. The sliding vane pump of claim 2, wherein the passage includes a passage within the vane. The slider of any of the preceding claims, the at least one end surface is curved to correspond to and provide a sealing surface with the inner stator wall. A sliding vane pump as claimed in any preceding claim, wherein the passageway includes a groove in the inner stator wall. A sliding vane pump as in any preceding claim comprising a single vane slidably mounted in a cavity extending through the rotor, either end of the vane abutting the inner wall of the stator. The sliding vane pump of claim 7 when dependent on claim 3, wherein both end faces of the vane include the groove. A sliding vane pump as claimed in any preceding claim, wherein the rotor is mounted for eccentric rotation within the stator. The sliding vane pump of any preceding claim, a cross-section of at least a portion of a length of the sliding vane including a protrusion configured to cooperate with a correspondingly shaped indentation in the cavity in the rotor In part, the protruding portion inhibits twisting of the blade about its longitudinal axis. A sliding vane pump as in any preceding claim, the pump being configured to pump a lubricant. The sliding vane pump of claim 11 configured to pump a high density lubricant, the lubricant having a density greater than 1.5 Kg/liter. A sliding vane pump as claimed in any preceding claim, wherein the passage comprises a cross section of between 1 mm ² and 2 mm ² . The sliding vane pump of any of the preceding claims, the passage is sized such that a final pressure reduction of between 5% and 15% can be achieved by the pump. A sliding vane pump as claimed in any preceding claim, wherein a largest portion of the vane comprises a circular cross-section; and At least one further portion of the blade includes a non-circular cross-section. A sliding vane pump comprising a rotor rotatably mounted in a stator; the rotor includes at least one vane slidably mounted in a corresponding at least one cavity; the rotor, stator and at least one vane define a plurality of variable volume pump chambers for delivering fluid from a fluid inlet to a fluid outlet after rotating the rotor, the at least one vane separating adjacent pump chambers; and A largest portion of the blade has a circular cross-section; At least one further portion of the vane has a non-circular cross-section. A sliding vane pump as in claim 15 or 16, wherein the at least one further portion is located at an end of the vane. The sliding vane pump of claim 17, wherein the at least one further portion is located at both ends of the vane. The sliding vane pump of any one of claims 15 to 18, wherein a cross-section of a groove in the stator configured to receive the vane includes a non-circular cross-section corresponding to the non-circular cross-section of the vane Circular cross section. The sliding vane pump of any one of claims 15 to 19, wherein the at least one cavity within the rotor includes a circular cross-section along a length of the cavity. The sliding vane pump of any one of claims 15 to 20, wherein the rotor includes an additional anti-rotation component mounted in a portion of the rotor cavity configured to receive the at least one further portion of the vane. The sliding vane pump of any one of claims 15 to 21, wherein the non-circular cross-section is smaller than the circular cross-section. The sliding vane pump of any one of claims 15 to 22, wherein the at least one further portion comprises at least one concave section machined from an outer surface of the vane. The sliding vane pump of claim 23, wherein the at least one recessed section includes a flat axially extending surface. A sliding vane pump as claimed in any preceding claim, wherein the pump includes a lubricant pump for actuating a valve and supplying lubricant to a vacuum pump. A vacuum pump comprising a sliding vane pump as claimed in any preceding claim for supplying lubricant to the vacuum pump. A vane for a sliding vane pump as claimed in any one of claims 1 to 15, the vane being configured to be slidably mounted in a corresponding cavity in a rotor and extending from the cavity so as to be mounted on the pump At least one end face of the vane abuts an inner stator wall when in the rotor and thereby separates adjacent pumping chambers; The vane includes a channel that is configured to provide a passage between the adjacent pump chambers when the vane is installed in the pump. 28. The blade of claim 27, wherein the channel includes a groove in the at least one end face of the blade. The vane of claim 28, wherein the passageway includes a passageway extending through the vane. A vane for a sliding vane pump as claimed in any one of claims 15 to 24, the vane being configured to have a substantially circular cross-section for a larger portion of a length of the vane and for the vane A non-circular cross-section of a smaller portion of a length, the vane is configured to be slidably mounted in a correspondingly shaped cavity in a rotor and extend from the cavity such that it is mounted on a pump in the At least one end face of the vane abuts an inner stator wall when in the rotor and thereby separates adjacent pumping chambers.

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