Vacuum pump

Abstract

A vacuum pump (100) comprising: a first chamber (112); a second chamber (106); a rotatable shaft (110) extending from the first chamber (112) into the second chamber (106); one or more sealing members (208) extending around the shaft (110) and positioned between the first chamber (112) and the second chamber (106); and a dynamic sealing element (206) extending around the shaft (110), the dynamic sealing element (206) having a first side (220) facing towards the first chamber (112) and an opposing second side (222) facing towards the second chamber (106); wherein the dynamic sealing element (206) is configured to, responsive to a positive pressure differential between the first side (220) and the second side (222) being at or above a threshold value, axially deform such that the second side (222) contacts a first surface of the one or more sealing members (208), thereby restricting and / or preventing flow of fluid between the first chamber (112) and the second chamber (106).

Description

[0001] VACUUM PUMP

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to seals between chambers of vacuum pump systems, especially, but not limited to, dry vacuum pumps.

[0004] BACKGROUND

[0005] In dry vacuum pumps, typically a rotating drive shaft is supported by bearings located at opposite axial ends of the drive shaft. The bearings are located in lubrication chambers located at the opposing axial ends of the drive shaft. One or both of the lubrication chambers may comprise a gear assembly and, as such, may be considered to be a gearbox or a gearbox chamber. A lubricant, such as an oil, is circulated in the lubrication chambers to lubricate the moving parts therein, including the bearings, the gearbox, and the drive shaft. The lubricant may be circulated by means of a throwing arm, i.e. a thrower, that may be attached to one of the drive shafts. In contrast, no liquids are used in the main pumping stages (i.e. the pumping chamber) between the lubrication chambers.

[0006] It is desirable to seal the lubrication chambers located at the opposing axial ends of the drive shaft from the main pumping stages located therebetween such that no fluid flows between the lubrication chambers and the main pumping stages. In other words, it is generally desirable to prevent fluid lubricant flowing from the lubrication chambers into the main pumping stages, and also to prevent pumped gas from flowing from the main pumping stages into the lubrication chambers.

[0007] SUMMARY OF INVENTION

[0008] In an aspect, there is provided a vacuum pump comprising: a first chamber; a second chamber; a rotatable shaft extending from the first chamber into the second chamber; one or more sealing members extending around the shaft and positioned between the first chamber and the second chamber; and a dynamic sealing element extending around the shaft, the dynamic sealing element having a first side facing towards the first chamber and an opposing second side facing towards the second chamber. The dynamic sealing element is configured to, responsive to a positive pressure differential between the first side and the second side being at or above a threshold value, axially deform such that the second side contacts a first surface of the one or more sealing members, thereby restricting and / or preventing a flow of fluid between the first chamber and the second chamber.

[0009] The first chamber may be a lubrication chamber.

[0010] The second chamber may be a pumping chamber.

[0011] The vacuum pump may further comprise a wall between the first chamber and the second chamber.

[0012] The dynamic sealing element may comprise an outer ring fixed to the wall, and an inner ring.

[0013] The inner ring may further comprise a contacting portion formed of a material from the group of materials consisting of: cast iron, oil impregnated sintered metal, polytetrafluoroethylene, and graphite.

[0014] The dynamic sealing element may be further configured to, responsive to a negative pressure differential between the first side and the second side being at or above a threshold value, axially deform such that the first side contacts a second surface of the one or more sealing members, thereby restricting and / or preventing a flow of fluid between the first chamber and the second chamber.

[0015] The vacuum pump may further comprise means of conveying a pressurisation gas at the first side and / or the second side of the dynamic sealing element.

[0016] The vacuum pump may further comprise a further dynamic sealing element having a third side facing towards the first chamber and an opposing fourth side facing towards the second chamber. The further dynamic sealing element is configured to, responsive to a negative pressure differential between the third side and the fourth side being at or above a further threshold value, axially deform such that the third side contacts a third surface of the one or more sealing members, thereby restricting and / or preventing a flow of fluid between the first chamber and the second chamber.

[0017] The wall may further comprise an opening through which the shaft extends. The dynamic sealing element may be positioned within the opening at a proximal end to the first chamber.

[0018] The further dynamic sealing element may be positioned within the opening at a proximal end to the second chamber.

[0019] The further dynamic sealing element may comprise a further outer ring fixed to the wall, and a further inner ring.

[0020] The further inner ring may further comprise a further contacting portion formed of a material from the group of materials consisting of: cast iron, oil impregnated sintered metal, polytetrafluoroethylene, and graphite.

[0021] The vacuum pump may further comprise means for conveying a pressurisation gas at one or more of the following locations: the first side of the dynamic sealing element, the second side of the dynamic sealing element, the third side of the further dynamic sealing element, and the fourth side of the further dynamic sealing element.

[0022] The vacuum pump may further comprise one or more lip seals extending around the shaft and positioned between the first chamber and the second chamber.

[0023] The vacuum pump may further comprise a labyrinth seal extending around the shaft and positioned between the first chamber and the second chamber.

[0024] The labyrinth seal may comprise: a first labyrinth seal part secured to and rotatable with the shaft; and a second labyrinth seal part substantially fixed relative to a housing of the vacuum pump. The first and second labyrinth seal parts define a tortuous path for a fluid.

[0025] The first labyrinth seal part may comprise the one or more sealing members.

[0026] The vacuum pump may further comprise a pressure equalisation means configured to, responsive to a pressure differential between the first chamber and the second chamber being at or above a threshold value, reduce the pressure differential to a value below the threshold value.

[0027] BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic illustration (not to scale) of a vacuum pump;

[0029] Figure 2 is a schematic illustration (not to scale) showing further details of a portion of the vacuum pump, including a seal system;

[0030] Figure 3 is a schematic illustration (not to scale) showing perspective view of a dynamic sealing element of the seal system; and

[0031] Figure 4 is a schematic illustration (not to scale) showing further details of a portion of the vacuum pump, including a further seal system.

[0032] DETAILED DESCRIPTION

[0033] Figure 1 is a schematic illustration (not to scale) of a vacuum pump 100.

[0034] In this embodiment, the vacuum pump 100 is a dry vacuum pump, such as a positive displacement dry pump.

[0035] The vacuum pump 100 comprises a pump inlet 102 and a pump outlet 104. The vacuum pump 100 is configured to pump a fluid (e.g. a gas) from the pump inlet 102 to the pump outlet 104.

[0036] The vacuum pump 100 comprises a plurality of vacuum pumping stages 106 that together define a pumping chamber 107 of the vacuum pump 100. Although four pumping stages 106 are depicted in Figure 1. It will be appreciated by those skilled in the art that a different number of stages may be implemented. The number of stages 106 may be application dependent. For example, the number of stages 106 of the pump 100 may depend on pumping requirements, such as a desired pressure at the pump inlet 102, and a pumping capacity.

[0037] Each of the vacuum pumping stages 106 comprises a respective pumping mechanism. Each pumping mechanism comprises a respective intermeshed pair of rotors 108. In this embodiment, the rotors 108 of the pumping mechanisms are driven by two drive shafts 110. The pumping mechanisms, i.e. the rotors 108, are driven by the drive shafts 110 for pumping fluid in series through the pumping stages 106 from the pump inlet 102 to the pump outlet 104.

[0038] The vacuum pump 100 further comprises lubrication chambers 112 located at opposing axial ends of the train of pumping stages 106. The lubrication chambers 112 are separated from respective adjacent pumping stages 106 by housing portions 114 having openings 115 for receiving the drive shafts 110. For example, the housing portions 114 may be headplates, end covers, or may form part of a stator of the vacuum pump. The lubrication chambers 112 house bearings 116 configured to support the drive shafts 110.

[0039] The vacuum pump 100 further comprises a motor (not shown) configured to one of the drive shafts 110. A gear assembly (not shown) is coupled between the drive shafts 110 such that rotation of a first drive shaft 110 by the motor drives the other of the drive shafts 110. The gear assembly may be located in a lubrication chamber 112.

[0040] A lubricant, such as an oil, is provided in sumps of the lubrication chambers 112. In operation, the lubricant is circulated in the lubrication chambers 112 to lubricate the moving parts (including the bearings 116, the gear assembly, and the drive shafts 110) within the lubrication chambers 112. The lubricant may be circulated by means of a throwing arm that may be attached to one of the drive shafts 110.

[0041] The vacuum pump 100 further comprises a plurality of seal systems 118 positioned within the openings 115. The seal systems 118 will be described in more detail later below with reference to Figures 2 and 3.

[0042] Conventional seal systems, such as piston rings, lip seals (also known as radial shaft seals), and labyrinth seals tend not to be fluid tight. Thus, there may be small leakages of lubricant from the lubrication chambers into the pumping stages, thereby contaminating the previously “dry” pump. Furthermore, there may be leakages of pumped process gases from the pumping stages into the lubrication chamber, thereby causing risk of damage to components such as the gear assembly due to the reactive nature of certain process gases. Under general operating conditions, these seal systems are effective, however, when there is a large pressure differential between the lubrication chamber and an adjacent pumping stage, the aforementioned leakages may occur.

[0043] What will now be described are embodiments of seal systems including a dynamic sealing element that tends to address the aforementioned problems associated with conventional seal systems.

[0044] Figure 2 is a schematic illustration (not to scale) showing further details of a portion of the vacuum pump, including the seal system 118.

[0045] Figure 3 is a schematic illustration (not to scale) showing a perspective view of a dynamic sealing element 206 of the seal system 118.

[0046] The seal system 118 comprises a piston ring labyrinth seal having a rotating part 202 and a plurality of fixed rings 204. The seal system 118 further comprises a dynamic sealing element 206. The seal system 118 is positioned within the opening 115.

[0047] The rotating part 202 is secured to and rotatable with the drive shaft 110. In other words, the rotating part 202 is fixed to the drive shaft 110 such that rotation of the drive shaft 110 causes the rotating part 202 to be rotated. The rotating part 202 comprises a series of axially spaced apart piston rings 208 along the drive shaft 110.

[0048] The plurality of fixed rings 204 are fixed relative to a housing of the vacuum pump 100. In this embodiment, the plurality of fixed rings 204 form a part of the housing portion 114. In other embodiments, however, the plurality of fixed rings 204 may be fixedly attached to the housing portion 114. The fixed rings 204 protrude from an inwardly facing surface of the opening 115.

[0049] The rotating part 202 and the fixed rings 204 are arranged such that at least one lateral surface of each piston ring 208 faces a lateral surface of an adjacent fixed ring 204. Furthermore, one or more radially outer faces (i.e. outwardly facing surfaces) of the rotating part 202 face a radially inner face (i.e. inwardly facing surface) of the opening 115. Each of the aforementioned facing surfaces are spaced apart such that there exists a small gap between the opposing surfaces. This gap defines a tortuous path through which the migration of gas or contaminants (e.g. from the pumping chamber 107 into the lubrication chamber 112) is difficult. In other words, leakage of process gases from the pumping chamber 107 to the lubrication chamber 112 is limited by means of the tortuous path.

[0050] The dynamic sealing element 206 comprises an outer ring 214, an inner ring 216, and a contact surface 218. The dynamic sealing element has a first side 220 facing towards the lubrication chamber 112 and a second side 222 facing towards the pumping stage 106.

[0051] In this embodiment, the dynamic sealing element 206 is positioned intermediately between two adjacent piston rings 208. More specifically, under normal operating conditions, the inner ring 216 and the contact surface 218 are positioned such that they are equidistant from the two adjacent piston rings 208. The outer ring 214 is fixedly attached to the housing portion 114. As described herein, “normal operating conditions” refers to operation of the vacuum pump 100 when a pressure differential between the lubrication chamber 112 and the adjacent pumping stage 106 is below a threshold value.

[0052] In this embodiment, the dynamic sealing element 206 can be considered to form a part of the tortuous path.

[0053] In this embodiment, the inner ring 216 is formed of a malleable sheet metal. The contact surface 218 is formed of a material that is hard wearing and has self-lubricating properties. In non-limiting examples, the contact surface 218 may be formed of a material selected from the group of materials consisting of: cast iron, oil impregnated sintered metal, polytetrafluoroethylene (PTFE), and graphite.

[0054] Under normal operating conditions, the seal system 118 is not fluid tight. As described above, the leakage of process gas from a pumping stage 106 into an adjacent lubrication chamber 112 is limited by means of the tortuous path. The seal system 118 may further comprise an oil labyrinth seal (not shown) configured to limit leakage of lubrication oil from the lubrication chamber 112 to the pumping stage 106 by means of a further tortuous path. The oil labyrinth seal is located at a side of the piston ring labyrinth seal facing towards the lubrication chamber 112. Furthermore, a pressure in the lubrication chamber 112 tends to be at or above a pressure in the adjacent pumping stage 106. Thus, under normal operating conditions, leakage of process gas from a pumping stage 106 into the lubrication chamber 112 is further opposed by means of the resulting pressure gradient therebetween.

[0055] However, there are conditions in which the pressure differential between the lubrication chamber 112 and a pumping stage 106 temporarily exceeds the aforementioned threshold value. In such conditions, the dynamic sealing element 206 is configured to provide a total seal between the lubrication chamber 112 and the adjacent pumping stage 106, thereby fluidly isolating the lubrication chamber 112 from the adjacent pumping stage 106. More specifically, the inner ring 216 of the dynamic sealing element 206 is configured to, responsive to the pressure differential exceeding the threshold value, axially deform towards a region of lower pressure such that the contacting surface 218 contacts a proximal piston ring 208. In this way, the plurality of piston rings 208 can be considered as sealing members providing surfaces for the dynamic sealing element 206 to abut in order to form a total seal. Equivalently, the rotating part 202 may be considered as a sealing member providing surfaces for the dynamic sealing element 206 to abut in order to form a total seal.

[0056] Thus, leakage of contaminants between the lubrication chamber 112 and the adjacent pumping stage 106 tends to be avoided until a pressure equalisation means (not shown) of the vacuum pump 100 restores the pressure differential between the lubrication chamber 112 and the adjacent pumping stage 106 to below the threshold value.

[0057] For example, in operation, as process gases are introduced into a pumping chamber 106, a pressure in the pumping stage 106 may temporarily exceed a pressure in an adjacent lubrication chamber 112, whereby the pressure differential between the lubrication chamber 112 and the pumping stage 106 exceeds the threshold value. In this way, a negative pressure differential is established between the first side 220 and second side 222 of the dynamic sealing element 206. The inner ring 216 of dynamic sealing element 206 is configured to, responsive to the negative pressure differential exceeding the threshold value, axially deform towards the lubrication chamber 112 until the contacting surface 218 contacts a piston ring 208 proximal to the first side 220. Thus, the lubrication chamber 112 and the pumping stage 106 are fluidly isolated from each other. In other words, a fluid tight seal is provided between the lubrication chamber 112 and the pumping stage 106. Advantageously, a leakage of process gases from the pumping stage 106 to the lubrication chamber 112 that would have otherwise occurred tends to be avoided by means of the dynamic sealing element 206.

[0058] In a further example, as process gases are evacuated from a pumping stage 106, the decrease in pressure in the pumping stage 106 may cause a pressure differential between an adjacent lubrication chamber 112 and the pumping stage 106 to exceed the threshold value. In this way, a positive pressure differential is established between the first side 220 and second side 222 of the dynamic sealing element 206. The inner ring 216 of the dynamic sealing element 206 is configured to, responsive to the positive pressure differential exceeding the threshold value, axially deform towards the pumping stage 106 until the contacting surface 218 contacts a piston ring 208 proximal to the second side 222. Thus, the lubrication chamber 112 and the vacuum pumping stage 106 are fluidly isolated from each other. In other words, a fluid tight seal is provided between the lubrication chamber 112 and the pumping stage 106. Advantageously, a leakage of lubrication oil that would have otherwise occurred tends to be avoided by means of the dynamic sealing element 206.

[0059] Advantageously, the above-described configuration further tends to prevent large gas flows across the oil labyrinth seal which would otherwise overwhelm the seal and cause leakage of lubrication oil.

[0060] In some embodiments, there may be provided means for conveying a pressurisation gas at the first side 220 and / or at the second side 222 of the dynamic sealing element 206, thereby providing means to increase the pressure differential above the threshold value and provide a total seal. This may be desirable, for example, during load-lock of the vacuum pump 100, where there are greater fluctuations in pressure within the pumping chambers 106.

[0061] In the above embodiments, the fixed rings 204 are fixedly attached to, or form a part of the housing portion 114. In other embodiments, however, the fixed rings 204 may be fixedly attached to, or form a part of, the outer ring 206. In such embodiments, the outer ring 206 may extend across a length corresponding to a length of the rotating part 202, or the outer ring 206 may extend across a full length of the opening 115.

[0062] In the above embodiments, the inner ring of the dynamic sealing element 206 is formed of a malleable sheet metal. In other embodiments, however, the inner ring may be formed of any suitable material such that the inner ring 216 deforms under a desired pressure differential between the lubrication chamber 112 and the pumping stage 106.

[0063] In the above embodiments, the dynamic sealing element 206 is provided in a seal system 118 having a piston ring labyrinth seal. In other embodiments, however, the piston ring labyrinth seal may be omitted, and the dynamic sealing element 206 may act as a standalone seal. For example, in such an embodiment, the seal system may comprise a sealing member (e.g. a piston ring) rotatable with the shaft 110, thereby providing a surface for the dynamic sealing element 206 to contact in order to provide a total seal.

[0064] In further embodiments, the piston ring labyrinth seal may be omitted, and the dynamic sealing element 206 may be provided in a seal system having different sealing means, such as one or more lip seals (also known as radial shaft seals). In such an embodiment, the seal system may comprise a sealing member rotatable with the shaft 110, thereby providing a surface for the dynamic sealing element to contact in order to provide a seal. Advantageously, the dynamic sealing element 206 may be used with lip seals that are noncontacting with the shaft. For example, due to wear and manufacturing tolerances, the lip seal may not contact the shaft 110, but rather be of close tolerance with the shaft 110. Thus, an ingress of contaminants between the lubrication chamber 112 and the adjacent pumping stage 106 may occur dependent on a pressure differential therebetween. The dynamic sealing element 206 may be used to provide a total seal upon the pressure differential exceeding a threshold value. Advantageously, this facilitates the use of lip seals formed without per- and polyfluoroalkyl substances (PFAS), where it is desirable for the lip seal to not contact the shaft 110 due to, for example, greater sensitivity to wear and temperature compared to lip seals formed at least partially of PTFE. In this way, the dynamic sealing element 206 may be considered to advantageously facilitate the use of other types of seal systems 118.

[0065] In yet further embodiments, the dynamic sealing element may be provided in a seal system having both a piston ring labyrinth seal and further different sealing means, such as one or more lip seals.

[0066] In the above embodiments, the dynamic sealing element 206 is provided in a seal system 118 between a lubrication chamber 112 and a pumping stage 106. In other embodiments, however, the dynamic sealing element 206 may be provided in a seal system between any two chambers of a vacuum pump 100.

[0067] In the above embodiments, there may be provided a single dynamic sealing element 206 configured to axially deform towards the first lubrication chamber 112 or the pumping stage 106 depending on a negative pressure differential or a positive pressure differential exceeding a threshold value respectively. In other words, the dynamic sealing element 206 may act in both directions. In other embodiments, however, there may be provided a single dynamic sealing element acting in a single direction, or two dynamic sealing elements each acting in opposite directions.

[0068] By way of example, Figure 4 is a schematic illustration (not to scale) showing further details of the vacuum pump 100, including a seal system 118 according to a further embodiment.

[0069] In this embodiment, the seal system 118 comprises a first dynamic sealing element 406 and a second dynamic sealing element 410.

[0070] The first dynamic sealing element 406 is positioned proximate to the lubrication chamber 112. More specifically, the first dynamic sealing element 406 is positioned at a first end of the opening 115, wherein the first end is a proximal end to the lubrication chamber 112.

[0071] The first dynamic sealing element 406 has a first side 420 facing towards the lubrication chamber 112, and a second side 422 facing towards the pumping stage 106.

[0072] The first dynamic sealing element 406 comprises an outer ring 414 fixed to the housing portion 114, an inner ring 416, and a contacting surface 418. The inner ring 416 is configured to, responsive to a positive pressure differential between the first side 420 and the second side 422 exceeding a threshold value, axially deform such that the contacting surface 418 at the second side 422 contacts the rotating part 202, thereby fluidly isolating the lubrication chamber 112 from the pumping stage 106.

[0073] The second dynamic sealing element 410 is positioned proximate to the pumping stage 106. More specifically, the second dynamic sealing element 410 is positioned at a second end of the opening 115, wherein the second end is a proximal end to the pumping stage 106.

[0074] The second dynamic sealing element 410 has a third side 421 facing towards the lubrication chamber 112, and a fourth side 423 facing towards the pumping stage 106.

[0075] The second dynamic sealing element 410 comprises an outer ring 415 fixed to the housing portion 114, an inner ring 417, and a contacting surface 419. The inner ring 417 is configured to, responsive to a negative pressure differential between the third side 421 and the fourth side 423 exceeding a further threshold value, axially deform such that the contacting surface 419 at the third side 422 contacts the rotating part 202.

[0076] Advantageously, this embodiment facilitates the first dynamic sealing element 406 and the second dynamic sealing element 410 to have different tolerances to pressure differentials acting across them. For example, the inner ring 416 of the first dynamic sealing element 406 may be formed of a different material and / or thickness than the inner ring 417 of the second dynamic sealing element 410. It may be desirable, for example, for the further threshold value associated with the second dynamic sealing element 410 to be smaller than the threshold value associated with the first dynamic sealing element 406.

[0077] It will be appreciated that in all of the embodiments described herein, the dynamic sealing elements 206, 406, 410 are reversibly axially deformable such that, once the above-described pressure differentials are no longer above the required threshold, the dynamic sealing elements 206, 406, 410 return to their original state in which they do not fluidly isolate the above-described chambers 106, 112 from each other. In some embodiments, there may be provided means for conveying a pressurisation gas at one or more of the following locations: the first side 420 of the first dynamic sealing element 406, the second side 422 of the first dynamic sealing element 406, the third side 421 of the second dynamic sealing element 410, and the fourth side 423 of the second dynamic sealing element 410. Thus, means are provided to increase the pressure differential above the threshold value and provide a total seal. This may be desirable, for example, during loadlock of the vacuum pump 100, where there are greater fluctuations in pressure within the pumping chambers 106.

[0078] In the above embodiments, the dynamic sealing elements 206, 406, 410 are configured to, responsive to a pressure differential between the lubrication chamber 112 and an adjacent pumping stage 106 exceeding a threshold value, fluidly isolate the lubrication chamber 112 from the pumping stage 106. In other embodiments, however, the dynamic sealing elements 206, 406, 410 does not fluidly isolate the lubrication chamber 112 from the pumping stage 106, and instead may restrict or limit a flow of fluid between the lubrication chamber 112 and the adjacent pumping stage 106. In such embodiments, the dynamic sealing elements 206, 406, 410, responsive to the pressure differential exceeding the threshold value, may define at least part of an increased tortuous path.

[0079] REFERENCE NUMERAL KEY

[0080] 100 - vacuum pump

[0081] 102 - pump inlet

[0082] 104 - pump outlet

[0083] 106 - pumping stage

[0084] 107 - pumping chamber

[0085] 108 - rotor

[0086] 110 - drive shaft

[0087] 112 - lubrication chambers

[0088] 114 - housing portions

[0089] 115 - opening

[0090] 116 - bearings

[0091] 118 - seal system

[0092] 202 - rotating part

[0093] 204 - fixed rings

[0094] 206 - dynamic sealing element

[0095] 208 - piston rings

[0096] 214 - outer ring

[0097] 216 - inner ring

[0098] 218 - contacting surface

[0099] 220 - first side

[0100] 222 - second side

[0101] 406 - first dynamic sealing element

[0102] 410 - second dynamic sealing element

[0103] 414, 415 - outer rings

[0104] 416, 417 - inner rings 418,419- contacting surfaces

[0105] 420 - first side

[0106] 421 - third side

[0107] 422 - second side 423 - fourth side

Claims

CLAIMS1 . A vacuum pump comprising: a first chamber; a second chamber; a rotatable shaft extending from the first chamber into the second chamber; one or more sealing members extending around the shaft and positioned between the first chamber and the second chamber; and a dynamic sealing element extending around the shaft, the dynamic sealing element having a first side facing towards the first chamber and an opposing second side facing towards the second chamber; wherein the dynamic sealing element is configured to, responsive to a positive pressure differential between the first side and the second side being at or above a threshold value, axially deform such that the second side contacts a first surface of the one or more sealing members, thereby restricting and / or preventing a flow of fluid between the first chamber and the second chamber.

2. The vacuum pump of claim 1 , wherein the first chamber is a lubrication chamber, and the second chamber is a pumping chamber.

3. The vacuum pump of claim 1 or 2, further comprising a wall between the first chamber and the second chamber, wherein the dynamic sealing element comprises: an outer ring fixed to the wall; and an inner ring.

4. The vacuum pump of claim 3, wherein the inner ring further comprises a contacting portion formed of a material from the group of materials consisting of: cast iron, oil impregnated sintered metal, polytetrafluoroethylene, and graphite.

5. The vacuum pump of any preceding claim, wherein the dynamic sealing element is further configured to, responsive to a negative pressure differential between the first side and the second side being at or above a threshold value, axially deform such that the first side contacts a second surface of the one or more sealing members, thereby restricting and / or preventing a flow of fluid between the first chamber and the second chamber.

6. The vacuum pump of any preceding claim, further comprising means for conveying a pressurisation gas at the first side and / or the second side of the dynamic sealing element.

7. The vacuum pump of any of claims 1 to 3 further comprising: a further dynamic sealing element having a third side facing towards the first chamber and an opposing fourth side facing towards the second chamber; wherein the further dynamic sealing element is configured to, responsive to a negative pressure differential between the third side and the fourth side being at or above a further threshold value, axially deform such that the third side contacts a third surface of the one or more sealing members, thereby restricting and / or preventing a flow of fluid between the first chamber and the second chamber.

8. The vacuum pump of claim 7 further comprising a wall between the first chamber and the second chamber, wherein the wall comprises an opening through which the shaft extends, and wherein the dynamic sealing element is positioned within the opening at a proximal end to the first chamber.

9. The vacuum pump of claim 7 or 8 further comprising a wall between the first chamber and the second chamber, wherein the wall comprises an openingthrough which the shaft extends, and wherein the further dynamic sealing element is positioned within the opening at a proximal end to the second chamber.

10. The vacuum pump of any of claims 7 to 9 further comprising a wall between the first chamber and the second chamber, wherein the further dynamic sealing element comprises: a further outer ring fixed to the wall; and a further inner ring.11 . The vacuum pump of claim 10, wherein the further inner ring further comprises a further contacting portion formed of a material from the group of materials consisting of: cast iron, oil impregnated sintered metal, polytetrafluoroethylene, and graphite.

12. The vacuum pump of any of claims 7 to 11 , further comprising means for conveying a pressurisation gas at one or more of the following locations: the first side of the dynamic sealing element, the second side of the dynamic sealing element, the third side of the further dynamic sealing element, and the fourth side of the further dynamic sealing element.

13. The vacuum pump of any preceding claim, wherein the vacuum pump further comprises one or more lip seals extending around the shaft and positioned between the first chamber and the second chamber.

14. The vacuum pump of any preceding claim, wherein the vacuum pump further comprises a labyrinth seal extending around the shaft and positioned between the first chamber and the second chamber.

15. The vacuum pump of claim 14, wherein the labyrinth seal comprises:a first labyrinth seal part secured to and rotatable with the shaft; and a second labyrinth seal part substantially fixed relative to a housing of the vacuum pump; wherein the first and second labyrinth seal parts define a tortuous path for a fluid.

16. The vacuum pump of claim 15, wherein the first labyrinth seal part comprises the one or more sealing members.

17. The vacuum pump of any preceding claim, further comprising a pressure equalisation means configured to, responsive to a pressure differential between the first chamber and the second chamber being at or above a threshold value, reduce the pressure differential to a value below the threshold value.

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