Rotor blade rows for turbomolecular vacuum pumps

Abstract

A turbomolecular vacuum pump rotor blade row for a turbomolecular vacuum pump having a rotor shaft to which, in use, the rotor blade row is coupled; the rotor blade row comprising: an injection-moulded rotor blade row body including a substantially annular hub and an array of rotor blades, the rotor blade row body being substantially formed of a fibre-reinforced polymer; an insert for reinforcing the annular hub; wherein the insert is substantially formed of a fibre-reinforced polymer having a substantially circumferential fibre distribution; and wherein the insert is integrally formed with the rotor blade row body.

Description

Field

[0001] The present invention relates to rotor blade rows for turbomolecular vacuum pumps, and to methods for manufacturing the same.Background

[0002] Rotor blade rows for vacuum systems, turbomolecular vacuum pumps for example, are increasingly formed of fibre-reinforced polymeric, ceramic and / or composite materials, e.g. carbon-fibre-reinforced polymers, which are mounted to a rotor shaft in use. However, there are several problems associated with rotor blade rows formed of these materials, which must be overcome.

[0003] During use, a rotor blade row is typically subject to high rotational speeds (e.g. up to around 90,000 RPM) and a broad temperature range (typically anywhere from around 243 K, i.e. -30°C, to greater than 373 K, i.e. greater than 100°C). This is the case particularly for turbomolecular pumps. Under these conditions, fracture and / or deformation of the rotor blade row (e.g. via creep) is more likely to occur. Strength, stiffness, high-temperature stability, creep resistance and fatigue resistance are all highly desirable properties for rotor blade rows of such systems.

[0004] The inventors of the present invention have investigated the manufacture of rotor blade rows formed of fibre-reinforced polymers. However, the inventors have determined that, for such rotor blade rows, guarding against fracture, via hoop stress and / or creep is especially challenging. In particular, under typical turbomolecular vacuum pump (TMP) operation conditions, such rotor blade rows can fail (e.g. fracture).

[0005] Nevertheless, there are clear advantages which support the continued production and use of injection moulded, fibre-reinforced rotors, e.g. improved pumping capabilities, reduction in weight, and ease of manufacture. Therefore, there is an ongoing need to provide improved rotors, and rotors having improved fracture resistance.

[0006] The present invention aims to solve these and other problems with the prior art.Summary

[0007] Accordingly, in a first aspect, the present invention provides a turbomolecular vacuum pump rotor blade row for a turbomolecular vacuum pump having a rotor shaft to which, in use, the rotor blade row is coupled.

[0008] The rotor blade row comprises an injection-moulded rotor blade row body including a substantially annular hub and an array of rotor blades, the rotor blade row body being substantially formed of fibre-reinforced polymer. The rotor blade row further comprises an insert for reinforcing the annular hub. The insert is substantially formed of fibre-reinforced polymer having a substantially circumferential fibre distribution. The insert is integrally formed with the hub of the rotor blade row body.

[0009] As described above, the inventors investigated the manufacture of fibre-reinforced rotor blade rows, including single piece, injection moulded rotor blade rows. They have found that such rotor blade rows are prone to fracture, hoop stress and / or creep, particularly at or towards their typically annular hub from which their rotor blades extend substantially radially outwardly therefrom.

[0010] Further investigation has led the inventors to determine that this tendency for weakness at the hub of a single piece, injection-moulded rotor is due to the distribution of the reinforcing-fibres therein.

[0011] As a component is injection moulded, the component's mechanical strength is dependent on reinforcing-fibre distribution. In particular, while the distribution (e.g. orientation) of reinforcing-fibres at the rotor blades is typically aligned with the flow direction, thus improving the mechanical resistance of the blade to stresses typically experienced during use, this has been observed not to be the case at the hub.

[0012] It has been found that a relatively ineffective fibre distribution is produced around the hub.

[0013] Typically, the distribution is at least partly determined by the location of injection gates. Typically, a single central injection gate is used to distribute molten fibre-reinforced material through a membrane that expands radially outwardly, in order to minimise the possibility of cold (or weld) lines which are mechanically weaker. This generally results in fibres being substantially aligned with the direction of injection flow.

[0014] A substantially circumferential fibre distribution about the annular hub is thought to be optimal. As described above, a circumferential fibre distribution is not observed in practice. The mechanical strength at the hub may be equal to approximately the capacity of the polymeric base material when the fibres are not effectively distributed (e.g. substantially radially or axially orientated at the hub). In other words, the addition of reinforcing fibres to a base material may have a limited effect where those fibres are not distributed effectively.

[0015] Single piece, injection-moulded turbomolecular vacuum pump (TMP) rotor blade rows in particular are therefore likely to experience significant mechanical stress, e.g. hoop stress and / or creep, due to the stresses generated as a result of typical TMP operating conditions. The required interference fit with a rotor shaft, which is typically formed of a different material, exacerbates the issue as the rotor shaft exhibits different behaviour, e.g. linear thermal expansion, during vacuum system operation. This may be described as creep, e.g. the gradual deformation or movement of a material under persistent stress over a period of time.

[0016] In the present invention, by providing a TMP rotor blade row comprising an integrally formed insert substantially formed of a fibre-reinforced polymer and having a substantially circumferential fibre distribution, the problems described above may be addressed. The substantially circumferential fibre distribution of the insert improves the mechanical stress resistance of the rotor blade row, e.g. hoop strength. Injection moulding one of the rotor blade row body and the insert onto the other bonds the two components together such that the insert is integrally formed with the rotor blade row body. The rotor blade row, for example, may be more resistant to centrifugal forces during rotation of a TMP rotor shaft. The insert may be integrally formed with the annular hub.

[0017] The insert reinforces the annular hub. By reinforcing the annular hub, the insert may strengthen the rotor blade row by supporting or improving the resilience of the rotor blade row body and more particularly the annular hub. The inventor believes the configuration of the present invention provides a rotor blade row with improved strength, stiffness, creep resistance, high-temperature stability and / or fatigue resistance.

[0018] The configuration of the present invention provides the rotor blade row with an improved, e.g. high, creep and hoop stress resistance. For the purposes of the present invention, a high creep resistance may be defined as the material having a melting temperature at least three times higher than the highest operational temperature of the TMP in Kelvin. Preferably, the highest operational temperature may be from about 353 K to about 408 K. The configuration of the present invention provides improved hoop stress and / or axial stress resistance. The insert may improve resistance to mechanical changes which may be brought about by temperature change, pump rotational speeds and / or the design of components of the rotor blade row.

[0019] The present invention also provides a rotor blade row having improved thermal expansion coefficient, e.g. linear thermal expansion coefficient relative to a base material of the reinforced polymer.

[0020] As used herein, the term "integrally formed" refers to the insert and rotor blade row body being made of a single piece or formed into a single piece.

[0021] Typically, the insert may not form part of a rotor shaft of a turbomolecular vacuum pump to which, in use, the rotor blade row is coupled. The insert may be configured to couple the rotor blade row to a rotor shaft of a vacuum pump. The insert may be substantially embedded within the rotor blade row body. For example, the insert may be substantially overmoulded by the rotor blade row body such that the rotor blade row body is at least partially in contact with a rotor shaft when the rotor blade row is coupled thereto.

[0022] As used herein, the term "circumferential fibre distribution" typically refers to the reinforcing fibre(s) of the insert having a substantially curved configuration about a longitudinal, e.g. rotational, axis of the rotor blade row (as opposed to the reinforcing fibre(s) being longitudinally or radially aligned).

[0023] The curvature of a reinforcing fibre(s) of the insert may be at a substantially constant distance from the longitudinal axis of the insert or at a varied distance (e.g. increasing or decreasing in distance) therefrom along the extent of the fibre or insert. For example, a reinforcing fibre or group of reinforcing fibres of the insert may have a hoop, coiled, spiral or helical configuration. The insert may comprise a single fibre or a plurality of fibres. The reinforcing fibre(s) of the insert may extend through at least part of the axial thickness of the insert and / or through at least part of the radial thickness thereof.

[0024] In embodiments, the insert may be substantially annular. The insert may have a fibre distribution which is substantially concentric with the substantially annular insert.

[0025] In embodiments, the rotor blade row body may be substantially monolithic.

[0026] As used herein, the term "monolithic" typically refers to the hub and blades being formed as a substantially single piece, for example as a result of an injection moulding process. In embodiments the rotor blade row body may be a single piece. In embodiments, the rotor blade row body may comprise a number of segments, wherein each segment includes a portion of the annular rotor hub and one or more integrally formed rotor blades.

[0027] In embodiments, the rotor blade row body may be injection moulded onto the insert. The insert may be overmoulded by the rotor blade row body.

[0028] In embodiments, the rotor blade row may comprise a plurality of inserts.

[0029] In embodiments, the insert may be a single piece insert. For example, the insert may be in the form of a ring defining a through-hole. In embodiments, the insert may comprise two or more pieces. For example, the insert may comprise two or more segments, or substantially parallel, coaxially spaced pieces. Typically, the insert may be generally tubular, e.g. cylindrical.

[0030] The insert may be configured to substantially couple the rotor blade row to the shaft of a vacuum pump.

[0031] In embodiments, at an interface between the insert and the rotor blade row body the polymer of the insert may be substantially fused with the polymer of the rotor blade row body. As used herein, the term "fused" refers to the intermixing and / or joining together of the rotor blade row body and the insert. For example, the rotor blade row may comprise a substantially amalgamated region including a mixture of the rotor blade row body material and the insert material where the rotor blade row body and the insert interface. In embodiments, the polymer of the insert may be substantially fused with the polymer of the rotor blade row body about substantially the entire circumference of the rotor blade row.

[0032] As used herein, the term "polymer" may refer to a singular polymeric material, polymer blend, or similar. In respect of the rotor blade row body or the insert, the polymer and reinforcing fibre(s) together provide a matrix. The polymer acts as a base material of the matrix. The reinforcing fibre(s), e.g. one or more filaments of carbon, glass, or the like, are contained by the polymeric base material.

[0033] In embodiments, the melt temperature of the insert, e.g. the base polymer thereof, may be substantially equal to or lower than the melt temperature of the rotor blade row body, e.g. the base polymer thereof. As the rotor blade row body is injection moulded onto the insert, the insert, or a portion thereof, e.g. an outer layer, may melt or otherwise deform to the extent that the insert fuses with the rotor blade row body as the rotor blade row body is formed. The polymer of the insert may substantially fuse with the polymer of the rotor blade row body. Typically, only a portion of the insert proximal to the interface with the blade row body may melt or otherwise deform upon contact with the molten blade row body.

[0034] In embodiments, the insert may be substantially formed of a continuous-fibre-reinforced polymer. The insert may be substantially formed of fibre-reinforced polymer wherein the fibres thereof have an average length which is longer than an average length of the fibres of the fibre-reinforced polymer of the rotor blade row body. The length-to-diameter ratio of the insert fibres may be greater than the length-to-diameter ratio of the rotor blade row body fibres. The insert may be substantially formed of a continuous circumferentially-orientated fibre reinforced polymer. In embodiments, the insert may comprise substantially a single fibre, e.g. a fibre coiled about the circumference of the insert multiple times over.

[0035] As used herein, the term "continuous fibre" may refer to a fibre which extends about substantially the entire circumference of the insert, and may circle the longitudinal axis of the rotor blade row at least once, substantially without interruption or a break therein.

[0036] In embodiments, the insert may have an average fibre length which is substantially equal to or greater than the diameter of the insert. In embodiments, the insert may have an average fibre length which is substantially equal to or greater than the circumference of the insert. In embodiments, the insert may have an average fibre length of at least 1 mm, optionally at least 2 mm. In embodiments, the insert may have an average fibre length of at least 20 mm. In embodiments, the insert may have an average fibre length of between around 20 mm and around 60 mm. The insert may comprise longer reinforcing fibres than those of the rotor blade row body.

[0037] In embodiments, the insert may be substantially additively manufactured, as described below.

[0038] In embodiments, fibre(s) of the fibre-reinforced polymer of the insert may be substantially unidirectional. For example, the fibres of the insert may extend in substantially the same or similar direction, e.g. in substantially clockwise direction, about the insert. The fibres of the insert may be substantially parallel to one another.

[0039] In embodiments, the reinforcing fibres of the insert may be substantially continuous and unidirectional, and may have a substantially circumferential distribution.

[0040] In embodiments, the rotor blade row body may be substantially formed of a discontinuous-fibre reinforced polymer. The rotor blade row body may be substantially formed of short fibres. A short fibre may be defined as a fibre having an aspect ratio (the ratio of fibre length to diameter) of between around 20 and around 60. In embodiments, the rotor blade row body may have an average fibre length of less than 1 mm, optionally less than 0.5 mm.

[0041] The polymers of the insert and rotor blade row body may be selected from the group consisting of a thermoset, a thermoplastic, an elastomer, and combinations thereof. For example, appropriate resins and polymers include, but are not limited to, acrylonitrile butadiene styrene (ABS), epoxy, vinyl, nylon, polyetherimide (PEI), Polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyamide-imide (PAI), polyamide (PA), polycarbonate (PC), polyactic acid (PLA) liquid crystal polymer, polyacetals (POM), polypropylene (PP), high-density polyethylene (HDPE), and various other thermoplastics.

[0042] In embodiments, the fibre-reinforced polymer of the rotor blade row body may comprise a thermoplastic. In embodiments, the rotor blade row body may comprise polyether ether ketone (PEEK).

[0043] In embodiments, the fibre-reinforced polymer of the insert may comprise a thermoplastic. For example, the insert may comprise a thermoplastic composite formed by a semi-crystalline low melt resin. In embodiments, the insert may comprise polyaryletherketone (PAEK).

[0044] Where the rotor blade row body is formed of PEEK and the insert is formed of PAEK, a stronger bond between the rotor blade row body and the insert is provided, compared to the rotor blade row body and insert being formed of substantially the same material, for example. During formation or manufacture, the molten PEEK resin fuses with the PAEK composite insert due to the differential in melt temperature. Molten PEEK melts and fuses with lower melt PAEK. This results in a robust bond being formed at the interface of the two components. For example, a lower temperature continuously reinforced PAEK composite may be overmoulded with shorter-fibre-reinforced PEEK. The rotor blade row has excellent mechanical properties and chemical resistance. The bond may be described as a high capacity, strong or stronger bond. Without being bound by theory, the inventors believe this is a result of physical intermixing of the polymer chains of the two materials forming the insert and the rotor blade row body.

[0045] In embodiments, the fibre-reinforced polymer of the rotor blade row body may comprise carbon and / or glass fibre(s). In other words, the rotor blade row body may be formed of a carbon-fibre-reinforced polymer. In embodiments, the fibre-reinforced polymer of the insert may comprise carbon and / or glass fibre(s). In other words, the insert may be formed of a carbon-fibre-reinforced polymer. A carbon fibre may be a collection, e.g. bundle, of carbon filaments which are substantially aligned with one another along a shared longitudinal axis. For example, the insert may be formed substantially of a continuous carbon fibre laminate. The laminate may be thermoformed and / or cut to form the insert.

[0046] In embodiments, each rotor blade may comprise a blade root proximal to the rotor hub and a blade tip distal from the rotor hub. The insert may extend only within the rotor hub. For example, the insert may not extend beyond the blade root of each rotor blade.

[0047] In embodiments, the reinforcing fibres of the rotor blade row body may be relatively denser towards the blade root and relatively less dense towards the blade tip.

[0048] In embodiments, a radially innermost surface of the rotor blade row body and a radially innermost surface of the insert may be substantially flush. In other words, the inner diameter of the rotor blade row body may be substantially the same as the inner diameter of the insert.

[0049] In embodiments, the inner diameter of the insert may be substantially smaller than the inner diameter of the rotor blade row body. Thus, when the rotor blade row is coupled to a rotor shaft of a vacuum system, in use, the insert may substantially prevent the rotor blade row body from contacting the rotor shaft.

[0050] In embodiments, the insert may extend axially up to axial ends of the rotor blade row body. Alternatively, in embodiments, the insert may extend beyond one or both axial ends of the rotor blade row body.

[0051] In embodiments, the insert may comprise a radially outwardly extending flange. A radially outwardly extending flange typically increases the surface area of the insert bonded to the rotor blade row body. In embodiments, the radially outwardly extending flange may be substantially circumferential. In embodiments, the insert may have a substantially L-, H-, or U- shaped axial cross section. In other words, the rotor blade row body and the insert may be coupled to one another by one or more interlocking connections. The one or more interlocking connections may be configured to minimise or substantially eliminate relative rotational movement of the insert and the rotor blade row body.

[0052] In embodiments, the insert may be configured to be integrally formed with more than one rotor blade row body.

[0053] In a further aspect, the present invention provides a rotor blade row assembly comprising two or more rotor blade rows according to any preceding aspect, and an insert integrally formed with each rotor blade row. The rotor blade row assembly may include a spacer configured to accommodate a stator of a turbomolecular vacuum pump, in use.

[0054] In a further aspect, the present invention provides a turbomolecular vacuum pump comprising one or more rotor blade rows according to any preceding aspect. The turbomolecular pump may comprise a plurality of pump stages including a stator and a rotor blade row according to any preceding aspect.

[0055] Advantageously, the insert does not typically form part of the rotor shaft and is distinct therefrom. Instead, the insert forms part of the rotor blade row which is coupled to the rotor shaft.

[0056] The skilled person will appreciate that the dimensions, shape, morphology, number, and arrangement of the rotor blade(s) may vary, e.g. according to the pump type.

[0057] In a further aspect, the present invention provides a method of manufacturing a turbomolecular vacuum pump rotor blade row for a turbomolecular vacuum pump. The method comprises the steps of: a. providing a mould for injection moulding a rotor blade row body having a substantially annular hub and an array of rotor blades; b. providing and placing an insert substantially formed of a fibre-reinforced polymer having a substantially circumferential fibre distribution within the mould such that a void exists between the insert and the mould; and c. injecting a fibre-reinforced polymer into the void and onto the insert.

[0058] Therefore, during step c., molten fibre-reinforced polymer material flows around the insert placed within the mould and substantially fills the void to form the rotor blade row body.

[0059] In embodiments, step c. may include the fusing e.g. bonding of the polymer of the insert with the polymer of the rotor blade row body at an interface between the insert and the rotor blade row body.

[0060] The method may include the step of curing, e.g. cooling, the rotor blade row. The curing step may substantially follow step c. Curing may include irradiating with ultraviolet (UV) light.

[0061] In embodiments, the method may include the step of finishing the rotor blade row. For example, the rotor blade row may be finished, e.g. machined and / or stamped, after curing. Finishing may include trimming, sanding, and / or polishing the rotor blade row or part thereof.

[0062] In embodiments, the step of finishing may include coating the rotor blade row or part thereof. The coating may, for example, comprise a chemical resistant coating.

[0063] In embodiments, the insert provided in step b. may be substantially formed of a continuous-fibre-reinforced polymer. In embodiments, the insert provided in step b. may have an average fibre length which is substantially equal to or greater than the circumference of the insert. In embodiments, the fibre-reinforced polymer of the insert provided in step b. may be substantially unidirectional.

[0064] In embodiments, the melt temperature of the insert provided in step b., e.g. the polymer thereof, may be at most substantially equivalent to or is substantially lower than the melt temperature of the rotor blade row body, e.g. the polymer thereof. The process may include pre-heating the insert prior to injection moulding the rotor blade row body. For example, the process may include pre-heating the insert to a temperature at which a solid to relatively fluid phase change of an outermost portion of the insert occurs in order that the outermost portion may intermix with the polymeric material of the injection moulded rotor blade row body.

[0065] In embodiments, step c. may include a one-shot injection. Alternatively, in embodiments, step c. may include a multi-shot injection.

[0066] In embodiments, the insert may be formed at least partially via an additive manufacturing process. In embodiments, the insert may be substantially manufactured by winding a tape including one or more substantially continuous fibres around a distinct mandrel to form a substantially annular insert. Typically, the tape may be wound around the mandrel so that several layers of tape are provided. Wound layers of tape may be arranged substantially one on top of another. The mandrel may be separated from the tape following winding. The insert may be cut from a larger body of wound tape. In embodiments, the insert may be substantially formed by a laser assisted tape winding (LATW) process.

[0067] In embodiments, the rotor blade row may be coupled to a rotor shaft outside of a vacuum pump.

[0068] In a further aspect, the present invention provides a computer-readable medium storing data which defines both a digital representation of the rotor blade row body and / or the insert, and operating instructions adapted to control a fabrication device to fabricate the blade row body and / or the insert using the digital representation of the same. The fabrication device may be an additive manufacturing device. The fabrication device may be an injection-moulding device.

[0069] For the avoidance of doubt, features of aspects and embodiments described herein may be combined, and still fall within the scope of the present invention.Brief Description of Figures

[0070] Preferred features of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates an axially sliced view of a rotor blade row in accordance with the present invention. Figure 2 shows an axial cross section of a rotor blade row in accordance with the present invention. Figure 3 illustrates an axially sliced view of a rotor blade row in accordance with the present invention including an L-shaped insert. Figure 4 illustrates an axial cross section of a rotor blade row in accordance with the present invention including an H-shaped insert. Figure 5 illustrates an axial cross section of part of a rotor blade row in accordance with the present invention including a U-shaped insert. Figure 6 illustrates an axial cross section of part of a rotor blade row in accordance with the present invention, comprising two inserts. Detailed Description

[0071] Figure 1 shows a rotor blade row according to the present invention, referenced generally as 10, which, in use, is suitable for coupling to the rotor shaft of a turbomolecular vacuum pump.

[0072] The rotor blade row 10 comprises a rotor blade row body 12 and an integrally formed insert 14.

[0073] The rotor blade row body 12 is injection moulded and is typically formed by injecting a fibre-reinforced polymer through a diaphragm-type gate. The rotor blade row body 12 is a one-piece, e.g. monolithic, unit which includes an annular hub 16 and a plurality of rotor blades 18 which are integrally formed with, and which extend radially outwardly from the annular hub 16. Each of the rotor blades 18 extends radially outwardly from the hub 16 at a blade root 26 of the blade 18 towards a blade tip 28 of the blade 18. Each of the rotor blades 18 is arranged to displace fluid (e.g. gas) during operation of the vacuum pump in which it is located, in use.

[0074] The insert 14, also substantially annular, is coupled to the rotor blade row body 12. The insert 14 of Figure 1 is a single piece insert.

[0075] The rotor blade row body 12 is a carbon-fibre-reinforced polymer matrix. The insert 14 is integrally formed with the rotor blade row body 12 and is also a carbon-fibre-reinforced polymer matrix. As described below, the 'base' polymer of the rotor blade row body 12 matrix is substantially different to the 'base' polymer of the insert 14 to aid bonding of the insert 14 to the rotor blade row body 12 during formation of the rotor blade row 10.

[0076] In the embodiment of Figure 1, the insert 14 is a substantially cylindrical component onto which the rotor blade row body 12 is injection moulded. The insert 14 is bonded to the rotor blade row body 12 during moulding thereof.

[0077] The reinforcing fibres of the rotor blade row body 12 have a shorter average length than those of the insert 14 and have a substantially radial distribution at each of the rotor blades 18. The reinforcing fibres are typically short fibres. The distribution of reinforcing fibres at the hub 16 of the rotor blade row body may typically be substantially radially aligned, e.g. as a result of injection moulding from a single, relatively central gate.

[0078] The reinforcing fibre or fibres of the insert 14 have a longer average length than those of the rotor blade row body 12 and are substantially circumferentially arranged. More specifically, the insert 14 comprises a substantially continuous and unidirectional circumferential fibre distribution.

[0079] In the rotor blade row of Figure 1, the polymer matrix of the rotor blade row body 12 comprises polyether ether ketone (PEEK) as a base material and the polymer matrix of the insert 14 comprises polyaryletherketone (PAEK) as a base material. These materials are selected in part due to the differential in their melt temperatures. The melt temperature of PAEK is typically lower than that of PEEK.

[0080] Figure 2 shows a magnified portion of the rotor blade row 10.

[0081] Typically, the insert 14 is placed within a mould such that a void exists between the insert 14 and the mould. The fibre-reinforced polymer for the rotor blade row body 12 is then injected into the void, typically via a diaphragm gate, to fill the void and form the single-piece rotor blade row. Thus, by virtue of placing the insert 14 within the mould prior to injection, the insert 14 is over-moulded by the rotor as the rotor is formed.

[0082] Typically, during injection-moulding of the rotor blade row body 12, molten fibre-reinforced polymer flows into a mould (not shown) containing the insert 14 and as that molten fibre-reinforced polymer contacts the insert, a region of the insert 14 proximal to the molten fibre-reinforced polymer of the forming rotor blade row body 12 melts or softens. As the lower melt temperature material (e.g. PAEK) of the insert region melts, it intermixes with the molten fibre-reinforced polymer. The higher melt temperature material (e.g. PEEK) of the rotor blade row body 12 thereby fuses with the material of the insert 14 at an interface, shown by dashed lines, between the insert 14 and the rotor blade row body 12.

[0083] The rotor blade row body 12 and insert 14 are therefore substantially monolithic.

[0084] Referring back to Figure 1, the inner diameter of the hub 16 of the rotor blade row body and the inner diameter of the insert 14 are substantially equivalent.

[0085] The insert 14 extends from a proximal end 20 to a distal end 22. When in situ on a rotor shaft, the proximal end 20 is typically located towards a lower-pressure end of the rotor blade row 10 and the distal end 22 is typically located towards a relatively higher-pressure section of the rotor blade row 10. In the embodiment of Figure 1, the insert 14 extends axially beyond the boundary of the rotor blade row body 12 in the distal direction.

[0086] Referring to Figure 3, which shows another embodiment of a rotor blade row 100, an interlocking connection is formed between the rotor blade row body 112 and insert 114 (e.g. as well as the fusing described above). More specifically, the insert 114 includes a radially outwardly extending flange 124 around which the rotor blade row body 112 is formed during injection-moulding thereof. It is also envisaged that, alternatively or in addition, the rotor blade row body 112 could include a radially inwardly extending flange and the insert could include a corresponding recess (not shown) which is substantially filled by molten fibre-reinforced polymer of the rotor blade row body 112 during injection-moulding.

[0087] The radially outwardly extending flange 124 of the insert 114 does not extend beyond the blade root 126 of each rotor blade 118. The flange 124 is embedded only within the rotor hub 116. The insert 114 has a substantially L-shaped axial cross section.

[0088] Each of the embodiments of Figures 3, 4 and 5 comprise radially outwardly extending flanges, 124, 224, 324 and each of the radially outwardly extending flanges is substantially circumferential. In other words, the radially outwardly extending flange of the insert extends substantially continuously about the circumference of the insert.

[0089] Referring to Figure 4, the rotor blade row 200 comprises an insert 214 which does not extend axially further than the hub 216 of rotor blade row body 212. The insert 214 includes a radially outwardly extending flange 224. The flange 224 has two opposing and axially extending limbs 230, 232 arranged towards a radial extremity thereof. The axially extending limbs 230, 232 are substantially embedded in the rotor blade row body 212. The insert 214 of Figure 4 has a substantially H-shaped axial cross section.

[0090] In the embodiment 300 of Figure 5, the insert 314 has a flange 324 including an axially extending limb 330. The insert 314 has a substantially U-shaped axial cross section. In Figure 5, the insert 314 does not extend beyond the hub 316 of the blade row body, i.e. does not extend to the blade root 226 of the rotor blades 218.

[0091] The shape of the insert 114, 214, 314 in Figures 3, 4 and 5 aids coupling of the rotor blade row body and the insert, typically prior to coupling with a rotor shaft of a vacuum pump. For example, relative rotational movement of the rotor blade row body and the insert may be minimised or substantially avoided.

[0092] The rotor blade row 400 of Figure 6 comprises two inserts 414, 414'. The inserts 414, 414' are substantially distinct, e.g. they do not contact one another directly. Each of the inserts 414, 414' may be formed and fused with the rotor blade row body 412 as described above.

[0093] As described above, the rotor blade row is typically formed at least partially by an injection moulding process. The rotor blade row body is typically injection moulded. The insert may also be injection moulded. Typically, the insert is cut, stamped or otherwise formed by a substantially non-injection-moulding process. For example, the insert may be formed by a laser assisted tape winding (LATW) process. The insert 14, 114, 214, 314 may be manufactured via an additive manufacturing process, for example three-dimensional (3D) printing, machining or other manufacturing method. Additional steps, such as machining or stamping may also be carried out to produce the rotor assembly.

[0094] It will be appreciated that various modifications may be made to the embodiments shown without departing from the spirit and scope of the invention as defined by the accompanying claims as interpreted under patent law.Reference Key

[0095] 10, 100, 200, 300, 400Rotor blade row 12, 112, 212, 312, 412Rotor blade row body 14, 114, 214, 314, 414, 414'Insert 16, 116, 216, 316Hub 18, 118, 218, 318Rotor blade 20Insert proximal end 22Insert distal end 26, 126, 226, 326Blade root 28Blade tip 124, 224, 324Radially outwardly extending flange 230,330Limb 232Limb

Claims

1. A turbomolecular vacuum pump rotor blade row for a turbomolecular vacuum pump having a rotor shaft to which, in use, the rotor blade row is coupled; the rotor blade row comprising: an injection-moulded rotor blade row body including a substantially annular hub and an array of rotor blades, the rotor blade row body being substantially formed of a fibre-reinforced polymer; an insert for reinforcing the annular hub; wherein the insert is substantially formed of a fibre-reinforced polymer having a substantially circumferential fibre distribution; and wherein the insert is integrally formed with the rotor blade row body.

2. The turbomolecular vacuum pump rotor blade row according to claim 1, wherein the insert is substantially overmoulded by the rotor blade row body.

3. The turbomolecular vacuum pump rotor blade row according to claim 1 or claim 2, wherein at an interface between the insert and the rotor blade row body the polymer of the insert is substantially fused with the polymer of the rotor blade row body.

4. The turbomolecular vacuum pump rotor blade row according to any preceding claim, wherein the melt temperature of the insert is substantially equal to or lower than the melt temperature of the rotor blade row body.

5. The turbomolecular vacuum pump rotor blade row according to any preceding claim, wherein the insert has an average fibre length which is greater than the average fibre length of the rotor blade row body.

6. The turbomolecular vacuum pump rotor blade row according to any preceding claim, wherein the insert is substantially formed of a continuous-fibre-reinforced polymer; optionally, wherein the insert has an average fibre length which is substantially equal to or greater than the circumference of the insert.

7. The turbomolecular vacuum pump rotor blade row according to any preceding claim, wherein the fibre-reinforced polymer of the insert is substantially unidirectional.

8. The turbomolecular vacuum pump rotor blade row according to any preceding claim, wherein the rotor blade row body comprises a thermoplastic; optionally, wherein the rotor blade row body comprises polyether ether ketone (PEEK).

9. The turbomolecular vacuum pump rotor blade row according to any preceding claim, wherein the insert comprises a thermoplastic; optionally, wherein the insert comprises polyaryletherketone (PAEK).

10. The turbomolecular vacuum pump rotor blade row according to any preceding claim, wherein the insert comprises a radially outwardly extending flange; optionally, wherein the radially outwardly extending flange is substantially circumferential.

11. A turbomolecular vacuum pump comprising one or more rotor blade rows according to any preceding claim.

12. A method of manufacturing a turbomolecular vacuum pump rotor blade row for a turbomolecular vacuum pump, the method comprising the steps of: a. providing a mould for injection moulding a rotor blade row body having a substantially annular hub and an array of rotor blades; b. providing and placing an insert substantially formed of fibre-reinforced polymer having a substantially circumferential fibre distribution within the mould such that a void exists between the insert and the mould; and c. injecting fibre-reinforced polymer into the void and onto the insert.

13. The method according to claim 12, wherein step c. includes the fusing of the polymer of the insert with the polymer of the rotor blade row body at an interface between the insert and the rotor blade row body.

14. The method according to claim 12 or claim 13, wherein the insert provided in step b. is substantially formed of continuous-fibre-reinforced polymer.

15. The method according to any of claims 12 to 14, wherein the melt temperature of the insert provided in step b. is at most substantially equivalent to or is substantially lower than the melt temperature of the rotor blade row body.

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