Rotor blade for turbo molecular vacuum pump

Abstract

The present disclosure relates to a rotor blade (104) for a turbo molecular vacuum pump. The rotor blade has a blade angle of 0 DEG at the root (106) that continuously increases along substantially the entire blade span S of the rotor blade (106). The rotor blade (104) tapers over a portion of its blade spread S from a maximum thickness (116) at the root (106) to a minimum thickness point (118) and is made of a polymer material reinforced with staple fibers. This provides a more complex geometry to the rotor blade (104) that has reduced weight and improved performance and cost effectiveness. The present disclosure also relates to a rotor (100) comprising a rotor blade (104), a mold for injection molding a rotor blade (104) or a rotor (100), and a method of injection molding a rotor blade (104) or a rotor (100).

Description

Technical Field

[0001] The present disclosure relates to a rotor blade for a turbomolecular vacuum pump. The present disclosure also relates to a rotor comprising the rotor blade, a two-part mold for injection molding the rotor blade and the rotor, and a method of injection molding the rotor blade and the rotor. Background Art

[0002] A turbomolecular pump (or 'turbo pump') is a type of vacuum pump that typically includes rapidly rotating rotor blades to help create a vacuum. As the rotor blades rotate, they impact gas molecules from the pump inlet and push them downstream toward additional pump stages and exhaust ports to create or maintain a vacuum in a particular system or space. In order to generate the desired vacuum level, the rotor blades may be required to rotate at high speeds (such as 10,000 to 100,000 rpm).

[0003] This type of rotor blade is typically manufactured from aluminum alloys, which provide the low weight and high strength required to operate at these high rotational speeds. However, such rotor blades are typically very simply formed, as it is surprisingly difficult and expensive to provide more complex blade geometries using such production processes and materials. If such complex geometries could be achieved reliably and more cost-effectively, they could be used to improve the pumping performance of a turbomolecular pump.

[0004] Therefore, there is a need for lightweight rotor blades for turbomolecular pumps that have more complex blade geometries and are simpler and more cost-effective to manufacture. Summary of the invention

[0005] From one aspect, the present disclosure provides a rotor blade for a turbomolecular vacuum pump. The rotor blade includes: a span extending from a root to a tip; a chord extending from a leading edge to a trailing edge; and a blade angle defined between the chord and a radial plane parallel to the axis of rotation of the rotor blade. The blade angle is 0° at the root. The blade angle increases along the span. The rotor blade tapers from a maximum thickness at the root to a minimum thickness point over a portion of the span. The rotor blade is made of a polymer material reinforced with short fibers.

[0006] The span extends along a radial axis relative to the axis of rotation (ie, the central axis along which the rotor blade projects from root to tip) from 0% span at the root to 100% span at the tip.

[0007] The continued increase in blade angle along the span causes the rotor blade to 'twist' (ie twist about the radial axis along which it extends).

[0008] In this context short fibers refer to reinforcing fibers whose size is negligible relative to the size of the polymer matrix into which they are introduced. They are distinguished from so-called long fibers or continuous fibers, which are usually laid in oriented layers and are similar in length to the polymer matrix. In this way, short fibers may alternatively be referred to as 'chopped fibers' (i.e., long fibers that have been chopped to provide short fibers).

[0009] The rotor blades are made of polymer materials reinforced with short fibers, allowing the rotor blades to be manufactured using an injection molding process and permitting the manufacture of rotor blades with more complex geometries in a simple and cost-effective manner. The more complex geometries permit the blades to have lower weight and improved (or at least comparable) pumping performance and strength compared to previous rotor blades.

[0010] The 0° blade angle at the root improves the strength and moldability of the rotor blade. For example, it increases the strength of the rotor blade at the root so that it can be removed from the mold during manufacturing with less risk of cracking. It may also allow for maximum clearance between adjacent rotor blades at the root. This reduces the need for thin or sharp cutting edges in the mold, which may be too thin to withstand manufacturing conditions and therefore tend to prematurely damage / crack after only a few moldings.

[0011] The continuous blade twist provided by the increased blade angle allows for simpler and more reliable manufacture of the rotor blade using a two-part mold. It also reduces the amount of sharp corners in the mold, thereby reducing the risk of air being trapped and material not adequately filling the mold during the injection molding process. This can also reduce the tendency of the mold to crack during the process. Twist can also be used to define a more aerodynamic shape of the rotor blade (e.g., compared to an untwisted blade).

[0012] Tapering a rotor blade from a maximum thickness at the root to a minimum thickness point over a portion of its span may provide the rotor blade with maximum strength at the root to handle increased stresses at the root during molding and high speed operation of the rotor while reducing the overall mass of the rotor blade.

[0013] The twist and taper combine to provide improved pumping efficiency / performance for the rotor blades because they can provide a more aerodynamic blade geometry and higher molecular flow efficiency (eg, providing a more favorable geometry for gas molecules to collide with and move downstream from the rotor blades during operation).

[0014] In the above embodiments, the thickness of the rotor blade is constant from the point of minimum thickness to the tip.

[0015] This minimizes the mass of the rotor blades while maintaining sufficient strength for the high speed operation required of the turbomolecular pumps.

[0016] In any of the above embodiments, the minimum thickness point may be between 20% and 40% of the leaf span.

[0017] This may provide an optimum balance between high strength at the root and lower mass across the span as a whole. In one example, the minimum thickness is at 25% of the span.

[0018] In any of the above embodiments, the maximum thickness may be at least 3.5 mm.

[0019] In any of the above embodiments, the minimum thickness may be at least 2.0 mm.

[0020] These values ​​may provide the lowest possible mass blade while ensuring sufficient structural strength of the rotor blade to cope with the injection moulding process and the stresses from the high rotational speeds experienced in use.

[0021] In any of the above embodiments, the thickness may decrease continuously over the portion where the thickness tapers.

[0022] This can optimize the balance between strength and mass across the tapered portion of the rotor blade and improve pumping performance.

[0023] In any of the above embodiments, the length of the blade chord may increase continuously along substantially the entire blade span (ie, substantially from root to tip).

[0024] In this way, the rotor blade can be said to 'fan out' as it extends between the root and the tip. This can improve pumping performance by reducing the gap between adjacent rotor blades, thereby reducing the probability of gas molecules leaking back upstream through the rotor blades during pumping operation.

[0025] In any of the above embodiments, the rotor blade further comprises a rounded region extending along the leading edge to the region where the leading edge meets the front blade surface of the rotor blade. In one embodiment, the rounded region extends across the entire length of the leading edge (i.e., along the entire span of the rotor blade from root to tip).

[0026] The rounded area blunts the leading edge area where the leading edge meets the front blade surface so that when gas molecules collide with the rounded area, they have an improved chance of picking up downstream of the rotor blade. This can improve pump performance. The rounded area can also reduce the sharpness of the corners within the mold, which can reduce air that can become trapped therein during molding and improve mold reliability and durability, among other things.

[0027] In any of the above embodiments, the radially outer surface at the tip is radiused. In this way, the radially outer surface is rounded so that when it is received in the turbomolecular pump, it more closely conforms to the cylindrical surface of the turbomolecular pump.

[0028] This may minimize tip clearance and therefore flow leakage between the tip and the surface of the rotor blade to improve pumping performance.

[0029] In any of the above embodiments, the polymer material may include 20% to 40% by weight of short fibers (ie, reinforced with these short fibers). In one example, the polymer material may include 30% by weight of short fibers (ie, reinforced with these short fibers).

[0030] This provides the best balance between mechanical strength, weight and production costs.

[0031] The short fibers may be one or a combination of carbon fibers, glass fibers, or aramid fibers.

[0032] The polymer material may be one of polyamide 6 (PA6), polyphthalamide (PPA), polyimide (PI), or polyetheretherketone (PEEK).

[0033] In one embodiment, the polymer material is one of PA6, PPA, PI or PEEK reinforced with 30% by weight of short carbon fibers.

[0034] In any of the above embodiments, the total length of the blade span from root to tip is at least 70 mm. In other words, the length of the rotor blade is at least 70 mm.

[0035] This provides a relatively long blade length, which can allow higher rotational speeds at the tip of the rotor blade and thereby improve pumping performance by increasing the probability that the rotor blade will collide with gas molecules and propel them downstream during operation. Due to the reduced weight and geometric characteristics of the rotor blades provided by the above embodiments, this blade length can be achieved without exceeding the operational stress limit.

[0036] From another aspect, the present disclosure provides a rotor comprising: a hub; and a plurality of rotor blades according to any one of the above embodiments, the plurality of rotor blades protruding from the hub. The rotor blades protrude radially from the hub.

[0037] In the above embodiment, the blade spacing distance between the leading edges of adjacent rotor blades is at least 3.24 mm across the entire span of the rotor blade. This avoids forming too thin sections or edges in the mold, which may be prone to damage under molding conditions. It also ensures that the spacing is large enough to ensure good pump performance (i.e., there is enough opportunity for gas molecules to be swept between adjacent rotor blades during their rotation).

[0038] In any of the above embodiments, the radially outer surface of the hub is rounded between roots of adjacent rotor blades.

[0039] The radiused section of the hub reduces stress concentrations at the roots of the rotor blades. This ensures that the rotor can cope with the stresses caused by the very high rotational speeds experienced during use.

[0040] In any of the above embodiments, the plurality of rotor blades are integrally formed with the hub.Thus, the rotor may be formed as a single unitary structure.

[0041] This can make manufacturing simpler and more efficient by reducing the number of steps in the process used to manufacture a complete rotor. This can also reduce the risk of compromising the structural strength of the rotor, for example by avoiding attachment points between the rotor blades and the hub.

[0042] Alternatively, the plurality of rotor blades may each be formed separately from the hub and attached by any other suitable means (eg, adhesive or mechanical interlock / interference fit).

[0043] From another aspect, the present disclosure provides a mold for injection molding a rotor blade or rotor of any of the above embodiments, the mold comprising two complementary mold halves which define a cavity in the shape of a rotor blade or rotor therebetween when pressed together.

[0044] The geometry of the rotor blade ensures that there are no overhanging features in the direction of mold opening, and allows easier molding and removal of the molded blade. It also allows the mold to be less susceptible to wear or cracking during use because it includes fewer thin sections and sharp edges. Similarly, there may be a reduced risk of air being trapped in sharp corners, thereby improving filling. By enabling a more reliable two-part mold injection molding process, the manufacture of rotor blades or rotors may be faster and more cost-effective.

[0045] From another aspect, the present disclosure provides a method of injection molding any of the above rotor blade or rotor embodiments using the above mold. The method includes: pressing two halves of the mold together to define a cavity in the shape of a rotor blade or rotor therebetween; injecting a molten polymer material having short fibers dispersed therein into the cavity; and solidifying the polymer material to form the rotor blade or rotor. Solidification may include cooling the mold halves and applying pressure to the mold halves. A curing process may also be performed during solidification.

[0046] This provides a simple and cost-effective method of producing a rotor blade or rotor for a turbomolecular pump having the advantageous weight and rotor blade geometry characteristics discussed above.

[0047] While certain advantages have been discussed with respect to certain features above, other advantages of certain features may become apparent to the skilled artisan in light of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Some exemplary embodiments and features of the present disclosure will now be described, by way of example only, and with reference to the following drawings, in which:

[0049] Figure 1 shows a perspective view of a rotor according to an embodiment of the present disclosure;

[0050] Figure 2 Shows Figure 1 A close-up top view of two adjacent rotor blades of a rotor;

[0051] Figure 3 Shows Figure 1 A close-up perspective view of a rotor hub region of a rotor;

[0052] Figure 4 A highly schematic perspective view showing a mold half according to an embodiment of the present disclosure; and

[0053] Figure 5 A method of injection molding a rotor or a rotor blade using a mold according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0054] refer to Figure 1 , shows a rotor 100 for a turbomolecular pump according to an embodiment of the present disclosure. The rotor 100 includes a rotor hub 102 having a central axis A about which the rotor 100 is configured to rotate. A hole 103 passing through the center of the rotor hub 102 is configured to engage with a rotatable shaft of the turbomolecular pump to provide rotation during operation. A plurality of rotor blades 104 are circumferentially spaced around the rotor hub 102 and extend radially from the rotor hub.

[0055] The rotor blades 104 are made of a polymer material reinforced with short fibers (i.e., a short fiber reinforced polymer composite). In one example, the polymer matrix material used is polyphthalamide (PPA) due to its relatively low cost. However, any other suitable polymer may be used, such as polyamide 6 (PA6), polyimide (PI), or polyetheretherketone (PEEK), etc.

[0056] The polymer matrix is ​​reinforced with short fibers. Any suitable short fibers can be used, such as carbon fibers, glass fibers, aramid fibers, etc. In this context, short fibers refer to fibers whose size is negligible relative to the size of the polymer matrix into which they are introduced. For example, the maximum length of the short fibers can be generally less than 10 mm, preferably less than 5 mm, and more preferably less than 1 mm. This is in contrast to the use of long reinforcing fibers, the size of which is not negligible relative to the size of the polymer material matrix into which they are introduced. Short fibers may also be referred to as chopped fibers (i.e., because they can be formed by chopping long fibers).

[0057] Compared to using short fibers, reinforcing a polymer matrix with long fibers can be more complex and expensive because all of the long fibers need to be laid in a specific orientation within the polymer matrix material. They are usually arranged in a predetermined direction of maximum stress in the produced part, so that these fibers can best reinforce the part. Although this increases the structural strength of the material, the complexity of orienting the long reinforcing fibers in a predetermined direction in a part with a complex shape leads to high production costs and time.

[0058] In contrast, an advantage of reinforcing a polymer with short fibers is that, due to the negligible size of the short fibers, they do not need to be oriented in any particular direction. Instead, they can simply be dispersed (e.g., in a substantially random manner) within the polymer matrix material. This significantly reduces the complexity of the manufacturing process while still providing reinforcement to the polymer matrix. In particular, it allows the rotor blade 104 to be manufactured by known injection molding processes. This reduces production costs relative to equivalent aluminum blades that are typically manufactured by more complex machining or casting processes. The resulting rotor blade 104 may also exhibit similar structural strength to an equivalent blade manufactured from an aluminum alloy while being lighter.

[0059] The polymer matrix material may be reinforced with 20% to 40% by weight of short fibers. In a particularly suitable example, 30% by weight of short fibers may be used. In another particularly suitable example, the polymer matrix material may be reinforced with 30% by weight of short carbon fibers.

[0060] It is believed that the above examples provide a good balance between mechanical strength, weight, and production cost of the rotor blade 104. Nevertheless, it is contemplated that the type and relative amounts of polymer matrix material and fibers may be readily varied to suit specific application requirements.

[0061] The rotor hub 102 may also be made of a polymer material reinforced with short fibers. The rotor hub 102 may be made of the same composite material as the rotor blades 104, integrally made with the rotor blades 104, or formed separately from the rotor blades and attached to them by any suitable means. For example, the rotor hub 102 and a plurality of rotor blades 104 may be injection molded as an integral or monolithic structure. It is believed that this provides mechanical strength and manufacturing efficiency benefits. Nevertheless, alternatively, the rotor blades 104 may be injection molded separately and then each separately attached to the rotor hub 102, which may also be injection molded. The rotor blades 104 may be attached by any suitable method, such as by bonding or mechanically bonding to the rotor hub.

[0062] refer to Figures 1 to 3 , rotor blade 104 extends from root 106 to tip 108 to define a span S. Root 106 is at 0% span and tip 108 is at 100% span. Although span S can be any suitable length, in certain embodiments, span S can be at least 70 mm, such as 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, or longer. This provides a relatively increased blade length, thereby providing a higher rotational speed at the tip of rotor blade 104, and thereby improving pumping performance by increasing the probability that rotor blade 104 will collide with a given gas molecule and propel it downstream, thereby increasing the number of successful collisions. This increased blade length can be achieved (e.g., without exceeding operating stress limits) as compared to known designs due to the weight reduction due to the use of short fiber reinforced polymer composites and the geometric characteristics of the rotor blades discussed below.

[0063] The rotor blade 104 extends from a leading edge 110 to a trailing edge 112 to define a chord C. In the depicted embodiment, the length of the chord C increases continuously along substantially the entire span (S), i.e., from the root 106 to the tip 108. In this context, “substantially” means at least 90% of the span S. This may allow a small portion (e.g., up to 10% of the span S adjacent to the root 106 (e.g., 0% to 10% or 0% to 5% span)) to exhibit a constant or non-increasing chord C. Nonetheless, in some embodiments, the chord C may increase continuously from the root 106 at 0% span to the tip 108 (i.e., continuously increase from 0% to 100% span).

[0064] The increased chord C causes the rotor blades 104 to fan out' along their span S'. This is believed to improve pumping efficiency / performance by reducing back leakage (ie, by reducing the gaps between adjacent rotor blades 104 to prevent gas molecules from escaping back over the rotor blades 104).

[0065] The rotor blades 104 also define a blade angle α. As shown, the blade angle α is defined as a radial plane R extending parallel to the central axis A. p A different blade angle α is defined at each % span position, depending on the blade chord C relative to the radial plane R at that % span position. p How to angle.

[0066] At the root 106, the rotor blade 104 includes a blade angle of 0°. In other words, at the root 106, the chord C of the rotor blade 104 is parallel to the central axis A about which the rotor blade 104 is configured to rotate. The 0° blade angle at the root 106 improves moldability. This is because it improves the strength at the root 106, making the finished blade easier to remove from the mold and less likely to break. It also provides a larger gap between the roots 106 of adjacent blades, so a wider portion of the mold can be used between the blades. This means that the mold is less prone to breaking in the molded condition, and therefore the reliability and life of the mold are improved.

[0067] The blade angle α increases continuously along substantially the entire span S. Again, in this context, "substantially" means at least 90% of the span S. This may allow a small portion (e.g., up to 10% of the span S adjacent to the root 106 (e.g., 0% to 10% span or 0% to 5% span)) to exhibit a constant or non-increasing blade angle α. In this manner, the blade angle α increases continuously from the root 106 at 0% span (or from the 0% to 10% span portion) to the tip 108. This increasing blade angle causes the rotor blade 104 to 'twist'. In other words, the rotor blade 104 twists continuously as it extends away from the root 106.

[0068] Once the rotor blade 104 is formed, the continuous blade twisting can also make it easier to remove from the mold. In particular, it can prevent the formation of sharp edges in the mold, which may be too thin and tend to break during the molding process or trap air and inhibit mold filling.

[0069] At the tip 108, the blade angle α may be between 30° and 60°, for example 40°, 45°, 50°, 55°. This may be optimal for moldability and also pumping performance.

[0070] The rotor blade 104 defines a thickness between a leading blade surface 114 and a trailing blade surface 115. In the depicted embodiment, the rotor blade 104 includes a maximum thickness 116 at the root 106. This may provide maximum strength at the root 106, which is required to cope with increased stresses at the root 106 during molding of the rotor 100 and during high speed operation. It has been found that, in one example, the maximum thickness 116 at the root 106 may be at least 3.5 mm.

[0071] The thickness of the rotor blade 104 decreases or tapers to a minimum thickness point 118 over a portion 120 of its span S. The thickness may taper starting at the root 106 (i.e., from 0% span). Alternatively, the maximum thickness 116 may be constant for a portion of the span S (e.g., 0% to 10% or 0% to 5% of the span S), after which point the thickness begins to taper.

[0072] The minimum thickness point 118 may be located between 20% and 40% of the leaf span, such as at 20%, 25%, 30%, 35% or 40% of the leaf span. As shown, the thickness may continuously decrease along the tapered thickness portion 120 to the minimum thickness point 118 .

[0073] These examples may provide the blade 104 with a more optimal balance between strength near the root and reduced mass across the span S as a whole.

[0074] In one example, it has been found that the minimum thickness 118 will be at least 2.0 mm. This may provide the lowest possible mass while ensuring sufficient structural strength of the rotor blade 104 to cope with the injection molding process and the loads generated by the high rotational speeds experienced in use.

[0075] In the depicted embodiment, the thickness of the rotor blade 104 is constant from the minimum thickness point 118 to the tip 108. In other words, the minimum thickness 118 may extend from the minimum thickness point 118 to the tip 108.

[0076] In another embodiment, the thickness of the rotor blade 104 increases along the span S after the minimum thickness point 118 to an intermediate thickness 117 (shown in dashed lines) that is higher than the minimum thickness 118 but lower than the maximum thickness 116. The intermediate thickness 117 is then maintained to the tip 108. In one example, the thickness of the blade 104 is maintained at the intermediate thickness 117 from 30% to 100% span, or from 40% to 100% span, or from 50% to 100% span. As will be appreciated, this span range will depend on the % span position of the minimum thickness 118, as discussed above.

[0077] Will understand, Figure 2is a 2D view of a twisted blade that includes both a blade angle α and a varying thickness along its span S, and so relative dimensions may not be accurately derived therefrom. For example, although the intermediate thickness at point 117 is shown in dashed lines, this may be the same as the minimum thickness at point 118, and any visual difference in thickness at these points may be spurious.

[0078] The thickness profiles of the rotor blade 104 embodiments discussed above may minimize the mass of the rotor blade while ensuring that sufficient material is present to handle the loads experienced during use.

[0079] At the tip 108, the rotor blade 104 defines a radial outer surface 122. The radial outer surface 122 can be radiused (i.e., rounded) so that it better conforms to the curvature of the conduit / surface of the turbomolecular pump in which it is configured to rotate. This minimizes the gap between the tip 108 of the rotor blade 104 and the conduit / pump surface to minimize leakage around the tip 108 and improve pumping performance. The radius of curvature of the radial outer surface 122 at the tip 108 can also avoid the use of sharp corners in the mold when defining the tip 108. This can improve mold filling / avoid air being trapped in the corner during the manufacturing process. The radius of curvature of the radiused / rounded tip can vary depending on the pump surface to which it will conform.

[0080] The leading edge 110 of the rotor blade 104 includes a rounded region 124 extending along its entire length, i.e., across the entire span S from the root 106 to the tip 108. The rounded region 124 extends along the leading edge 110 to where it meets the leading blade surface 114. The rounded region 124 provides a blunt surface that may take any suitable form, such as rounded / radii or chamfered.

[0081] When gas molecules collide with the rounded area 124, they have an improved chance of picking up downstream of the rotor blade 104 than if the rounded area 124 were not present. Thus, the rounded area 124 may improve pump performance.

[0082] Additionally, the radiused areas 124 reduce the sharpness of the corners required in the mold to define the rotor blade 104. This improves mold filling during manufacturing since less air can be trapped in the mold, and may also improve mold durability and reliability since stress concentrations in the mold are reduced.

[0083] In further examples, rotor blade 104 may additionally or alternatively feature blunting of either of the regions where leading edge 110 and trailing edge 112 meet leading blade surface 114 or trailing blade surface 115. For example, the circular region may extend across the entire span S where leading edge 110 meets trailing blade surface 115, where trailing edge 112 meets leading blade surface 114, and / or where trailing edge 112 meets trailing blade surface 115.

[0084] As shown, the hub 102 may also include a rounded portion 126 extending between the roots 106 of adjacent rotor blades 104a, 104b. In other words, the leading blade surface 114 of the first rotor blade 104a and the trailing blade surface 115 of the adjacent second rotor blade 104b may be attached to the hub 102 via the rounded portion 126. In other words, the leading blade surface 114 of the first blade 104a blends into the trailing blade surface 115 of the second blade 104b via the rounded portion 126. This provides a smoother and rounded interface between the blades 104a, 104b and the hub 102. The rounded portion 126 exists between each pair of circumferentially adjacent rotor blades 104 that radially protrude from the hub 102. The rounded portion 126 helps reduce stress concentrations at the root 106 of each rotor blade 104. This helps the rotor blades 104 resist the loads generated at high rotational speeds experienced during pump operation.

[0085] The blade spacing distance X is defined between the leading edges 110 of adjacent rotor blades 104a, 104b and is maintained at or above a minimum value X over the entire blade span S of the blades 104a, 104b. min , to avoid forming too thin sections or edges in the mold, which may be prone to damage under injection molding process conditions. In one example, it has been found that a suitable minimum blade spacing distance X min is at least 3.24 mm. In the depicted embodiment, it is found that the minimum separation distance X min It is between the roots 106 of adjacent rotor blades 104a, 104b.

[0086] refer to Figure 4 , depicts a schematic depiction of a mold half 200 for injection molding a rotor 100. The mold half 200 includes features 202 shaped to provide the geometry of the rotor blade 104 discussed above and features 204 shaped to provide the hub 102 to which the rotor blade 104 is attached. The features 202, 204 may be machined into the mold half 200 prior to use. The mold half 200 also includes a material injection channel 206 therein that is in fluid communication with the features 202, 204 and the exterior of the mold half 200.

[0087] As will be appreciated by a skilled artisan, a complementary second mold half (not shown) having features complementary to those of mold 200 will be pressed onto the top of mold half 200 to define a cavity (or a fluidly linked series of cavities) therein which will provide the shape of the rotor 100 and rotor blades 104 discussed above.

[0088] A known injector (not shown) such as a screw extruder will be placed in fluid communication with the material injection channel 206. The polymer material and the short fibers can be mixed and heated in the injector so that the molten polymer material with the short fibers dispersed therein can be delivered (or injected) into the mold formed by the two complementary mold halves 200. The molten polymer material will fill the cavity(ies) in the mold and solidify to form the rotor 100 and the rotor blades 104, which can then be removed by separating the two mold halves 200.

[0089] As will be appreciated, one mold may be used to define rotor 100 and plurality of rotor blades 104 as a single, unitary part, or separate molds may be used to define individual rotor blades 104 and other portions of rotor 100 (eg, hub 102 ) that may later be assembled together.

[0090] Forming the mold in two parts (ie, using two mold halves 200 ) may make it easier to eject the finished rotor blade 104 from the mold.

[0091] The mold may be made of a material suitable for the injection molding process, such as steel.

[0092] As discussed above, the geometry of the rotor blade 104 and in particular the 0° root blade angle and continuous blade twist ensures that there are no overhanging features in the direction that the mold halves open and allows for easier removal of the molded blade. It may also allow the mold to include fewer thin sections or sharp edges, thereby making it less susceptible to wear or cracking when subjected to molding conditions. This may make it less prone to trapping air in sharp corners when filling the mold and ensure that there are fewer defects in the molded rotor blade 104 and / or rotor 100.

[0093] The process of injection molding of short fiber reinforced polymers is well known to the skilled person and therefore need not be discussed in detail in this disclosure. Figure 5 A general method 300 for injection molding the rotor blade 104 and / or rotor 100 described above using the mold described above is depicted in FIG.

[0094] The method 300 includes: pressing two halves of a mold together to define a cavity in the shape of a rotor blade or rotor therebetween (step 301); injecting a molten polymer material having short fibers dispersed therein into the cavity in a molten form (step 302); and then solidifying the polymer material to form a rotor blade 104 or rotor 100 (step 303). The finished rotor blade 104 or rotor 100 can then be removed from the mold by separating the two mold halves.

[0095] As the skilled person will appreciate, depending on the material and properties of the short fiber reinforced material desired, various curing treatments (i.e., pressure and heat treatments) may be applied during the solidification step 303. As such steps will be part of known injection molding processes, they will not be discussed in further detail in this disclosure.

[0096] Although the drawings and accompanying description describe specific embodiments and examples, it will be understood that the scope of the present disclosure is not limited to such specific embodiments but is instead defined by the following claims.

[0097] Reference numerals list

[0098] For ease of reference, an attached Figures 1 to 5 List of reference numerals used in:

[0099] 100 rotors

[0100] 102 rotor hub

[0101] 103 rotor hub through hole

[0102] 104 rotor blades

[0103] 106 Rotor blade root

[0104] 108 rotor blade tip

[0105] 110 Rotor blade leading edge

[0106] 112Rotor blade trailing edge

[0107] 114 front blade surface

[0108] 115 rear blade surface

[0109] 116 Maximum blade thickness

[0110] 117 Middle blade thickness

[0111] 118Minimum blade thickness

[0112] 120Thickness tapered part

[0113] 122 Tip radial outer surface

[0114] 124 Rounded area of ​​the leading edge

[0115] 126 Rounded part of the hub

[0116] 200 mold half

[0117] 202 mold features

[0118] 204 mold features

[0119] 206 Material injection channel

[0120] 300 Methods

[0121] 301 Method Steps

[0122] 302 Methods and Steps

[0123] 303 Methods and Steps

[0124] A Rotor rotation axis

[0125] C Leaf String

[0126] S Leaf Exhibition

[0127] X blade spacing

[0128] X min Minimum blade spacing

[0129] R p Radial plane

[0130] α Blade angle

Claims

1. A rotor blade (104) for a turbomolecular vacuum pump, the rotor blade comprising: a leaf spread (S) extending from the root (106) to the tip (108); a blade chord (C) extending from a leading edge (110) to a trailing edge (112); as well as The blade angle (α) is defined between the blade chord (C) and a radial plane (R) parallel to the rotation axis (A) of the rotor blade (104). p )between; wherein the blade angle is 0° at the root (106) and increases continuously along substantially the entire blade span (S); wherein the rotor blade (104) tapers from a maximum thickness (116) at the root (106) to a minimum thickness point (118) over a portion (120) of the blade span (S); and The rotor blade (104) is made of a polymer material reinforced with short fibers.

2. The rotor blade (104) according to claim 1, wherein: The thickness is constant from the minimum thickness point (118) to the tip (108).

3. The rotor blade (104) according to claim 1 or 2, wherein: The minimum thickness point (118) is located between 20% and 40% of the leaf span (S), for example at 25% of the leaf span (S).

4. The rotor blade (104) according to any preceding claim, wherein: The maximum thickness (116) is 3.5 mm and / or the minimum thickness (118) is 2.0 mm.

5. The rotor blade (104) according to any preceding claim, wherein: The length of the blade chord (C) increases continuously along substantially the entire blade span (S).

6. The rotor blade (104) according to any preceding claim, comprising a rounded region (124) extending along the leading edge (110) across the blade span (S) to a region where the leading edge (110) meets a front blade surface (114) of the rotor blade (104).

7. The rotor blade (104) according to any preceding claim, wherein: The radially outer surface (122) at the tip (108) is radiused.

8. The rotor blade (104) according to any preceding claim, wherein: The total length of the blade span (S) from the root (106) to the tip (108) is at least 70 mm.

9. The rotor blade (104) according to any preceding claim, wherein: The polymer material comprises 20 to 40% by weight of staple fibers, such as 30% by weight of staple fibers.

10. A rotor (100) for a turbomolecular vacuum pump, the rotor comprising: Hub (102); as well as A plurality of rotor blades (104a, 104b) according to any preceding claim, said plurality of rotor blades protruding from said hub (102).

11. The rotor (100) according to claim 10, wherein: A blade spacing distance (X) between the leading edges (110) of adjacent rotor blades (104a, 104b) is at least 3.24 mm across the entire span (S) of the rotor blades (104a, 104b).

12. The rotor (100) according to claim 10 or 11, wherein: A portion (126) of the hub (102) is rounded between the roots (106) of adjacent rotor blades (104).

13. The rotor (100) according to claim 10, 11 or 12, wherein: The plurality of rotor blades (104) are integrally formed with the hub (102).

14. A mould for injection moulding a rotor blade (104) according to any one of claims 1 to 9 or a rotor (100) according to any one of claims 10 to 13, the mould comprising two complementary mould halves (200) which, when pressed together, define between them a cavity in the shape of the rotor blade (104) or the rotor (100).

15. A method of injection molding a rotor blade (104) according to any one of claims 1 to 9 or a rotor (100) according to any one of claims 10 to 13 using the mold according to claim 14, the method comprising: pressing the two mold halves (200) of the mold together to define a cavity therebetween in the shape of the rotor blade (104) or the rotor (100); injecting a molten polymer material having staple fibers dispersed therein into the cavity; and The polymer material is solidified to form the rotor blade (104) or the rotor (100).

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