TAPERED ROTARY DISC PUMP

Abstract

A tapered rotary disc pump is disclosed, including a disc assembly with a first disc and a second disc arranged in parallel to define a chamber. Each disc has an inner surface with multiple vanes extending toward the chamber. The vane outer ends align with the disc periphery, while vane inner ends extend toward the disc center. At least one vane tapers from the outer end toward the inner end, and optionally from the inner surface toward the chamber, to reduce turbulence and increase pumping efficiency. Standoffs couple the discs together and may extend into the vanes to further minimize turbulence. The vane leading face may include convex and concave portions to enhance fluid flow. Alignment of opposing vanes and equal vane counts between discs provide balanced operation and improved handling of fragile, abrasive, or high-solids fluids.

Claims

1. A tapered rotary disc pump, comprising: a disc assembly comprising a first disc and a second disc, the first disc comprising a first inner surface and the second disc comprising a second inner surface, the first disc and second disc forming a chamber between the first disc and the second disc; a plurality of standoffs coupling the first disc with the second disc; and a plurality of vanes comprising a first plurality of vanes and a second plurality of vanes, wherein the first plurality of vanes is disposed on the first inner surface and the second plurality of vanes is disposed on the second inner surface, each of the plurality of vanes comprising: a vane inner end and a vane outer end opposite the vane inner end, the vane outer end terminating at a disc periphery of the first disc or the second disc, wherein the vane inner end extends inwardly toward a center of the first disc or the second disc, a vane leading face and a vane trailing face, the vane trailing face comprising an orthogonal configuration with a respective inner surface; wherein at least one of the plurality of vanes tapers from the vane outer end toward the vane inner end, and further wherein the at least one of the plurality of vanes tapers from the respective inner surface toward the chamber.

2. The tapered rotary disc pump of claim 1, wherein each of the plurality of vanes tapers from the vane outer end toward the vane inner end, and further wherein each of the plurality of vanes tapers from the respective inner surface toward the chamber.

3. The tapered rotary disc pump of claim 1, wherein the first disc is in parallel alignment with the second disc.

4. The tapered rotary disc pump of claim 1, wherein the first disc is concentrically aligned with the second disc.

5. The tapered rotary disc pump of claim 1, wherein the first plurality of vanes comprises a first quantity and the second plurality of vanes comprises a second quantity, wherein the first quantity equals the second quantity.

6. The tapered rotary disc pump of claim 1, wherein each of the first plurality of vanes is aligned with one of the second plurality of vanes such that two opposing vanes are at equal radial positions during rotation of the tapered rotary disc pump.

7. The tapered rotary disc pump of claim 1, wherein each vane outer end forms a surface alignment with the disc periphery of one of the first disc or the second disc.

8. The tapered rotary disc pump of claim 1, wherein each of the plurality of standoffs extends into one of the first plurality of vanes.

9. The tapered rotary disc pump of claim 8, wherein each of the plurality of standoffs extends into one of the second plurality of vanes.

10. The tapered rotary disc pump of claim 1, wherein each of the plurality of standoffs is orthogonal to the first disc and the second disc.

11. The tapered rotary disc pump of claim 1, the vane leading face further comprising a convex portion and a concave portion, wherein the concave portion extends from the respective inner surface toward the convex portion, and the convex portion extends from the concave portion to the vane trailing face.

12. A tapered rotary disc pump, comprising: a disc assembly comprising a first disc and a second disc, the first disc comprising a first inner surface and the second disc comprising a second inner surface, the first disc and second disc forming a chamber between the first disc and the second disc; a plurality of standoffs coupling the first disc with the second disc; and a plurality of vanes comprising a first plurality of vanes and a second plurality of vanes, wherein the first plurality of vanes is disposed on the first inner surface and the second plurality of vanes is disposed on the second inner surface, each of the plurality of vanes comprising: a vane inner end and a vane outer end opposite the vane inner end, the vane outer end terminating at a disc periphery of the first disc or the second disc, wherein the vane inner end extends inwardly toward a center of the first disc or the second disc, a vane leading face and a vane trailing face, the vane trailing face comprising an orthogonal configuration with a respective inner surface; wherein at least one of the plurality of vanes tapers from the vane outer end toward the vane inner end.

13. The tapered rotary disc pump of claim 12, wherein each of the plurality of vanes tapers from the vane outer end toward the vane inner end.

14. The tapered rotary disc pump of claim 12, wherein the first plurality of vanes comprises a first quantity and the second plurality of vanes comprises a second quantity, wherein the first quantity equals the second quantity.

15. The tapered rotary disc pump of claim 12, wherein each vane outer end forms a surface alignment with the disc periphery of one of the first disc or the second disc.

16. A tapered rotary disc pump, comprising: a disc assembly comprising a first disc and a second disc, the first disc comprising a first inner surface and the second disc comprising a second inner surface, the first disc and second disc forming a chamber between the first disc and the second disc; a plurality of standoffs coupling the first disc with the second disc; and a plurality of vanes comprising a first plurality of vanes and a second plurality of vanes, wherein the first plurality of vanes is disposed on the first inner surface and the second plurality of vanes is disposed on the second inner surface, each of the plurality of vanes comprising: a vane inner end and a vane outer end opposite the vane inner end, the vane outer end terminating at a disc periphery of the first disc or the second disc, wherein the vane inner end extends inwardly toward a center of the first disc or the second disc, a vane leading face and a vane trailing face, the vane trailing face comprising an orthogonal configuration with a respective inner surface; wherein at least one of the plurality of vanes tapers from the respective inner surface toward the chamber.

17. The tapered rotary disc pump of claim 16, wherein each of the plurality of vanes tapers from the respective inner surface toward the chamber.

18. The tapered rotary disc pump of claim 16, wherein each of the first plurality of vanes is aligned with one of the second plurality of vanes such that two opposing vanes are at equal radial positions during rotation of the tapered rotary disc pump.

19. The tapered rotary disc pump of claim 16, wherein each of the plurality of standoffs extends into one of the first plurality of vanes.

20. The tapered rotary disc pump of claim 19, wherein each of the plurality of standoffs extends into one of the second plurality of vanes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other features, combinations, and embodiments will be appreciated by one having the ordinary level of skill in the art of fluid pumps upon a thorough review of the following details and descriptions, particularly when reviewed in conjunction with the drawings, wherein:

[0011] FIG. 1 shows a cross-section view of a conventional rotary disc pump;

[0012] FIG. 2 shows a perspective view of a disc assembly of a tapered rotary disc pump in accordance with a first illustrated embodiment

[0013] FIG. 3 shows dissected views of the disc assembly of the tapered rotary disc pump according to the first illustrated embodiment;

[0014] FIG. 4 shows a side view of a vane of the tapered rotary disc pump according to the first illustrated embodiment;

[0015] FIG. 5 shows a perspective view of a tapered rotary disc pump in accordance with a second illustrated embodiment;

[0016] FIG. 6 shows a perspective view of a first disc of a tapered rotary disc pump in accordance with a third illustrated embodiment; and

[0017] FIG. 7 shows a perspective view of a first disc of a tapered rotary disc pump in accordance with a fourth illustrated embodiment.

DETAILED DESCRIPTION

[0018] For purposes of explanation and not limitation, details and descriptions of certain preferred embodiments are hereinafter provided such that one having ordinary skill in the art may be enabled to make and use the invention. These details and descriptions are representative only of certain preferred embodiments, however, a myriad of other embodiments which will not be expressly described will be readily understood by one having skill in the art upon a thorough review of the instant disclosure. Accordingly, any reviewer of the instant disclosure should interpret the scope of the invention only by the claims, as such scope is not intended to be limited by the embodiments described and illustrated herein.

[0019] The features, components, and configurations described in connection with the various embodiments illustrated herein may be combined, interchanged, or otherwise modified in any number of ways without departing from the scope and spirit of the invention. The embodiments are presented by way of example and not limitation, and it is intended that the invention encompasses all such combinations, permutations, and modifications as would be understood by those skilled in the art.

[0020] For purposes herein, reference numbers are provided in the drawings for illustrating certain features of embodiments. Where distinct figures of the drawings utilize a shared reference number, it can be appreciated that the feature corresponding to the shared reference number is the same or similar, perhaps observed from a different view, or observed with respect to a different embodiment deploying the same or similar feature.

[0021] For purposes herein, the term taper means to gradually decrease in width, thickness, or diameter toward one end.

[0022] The term respective inner surface means one of the first inner surface or the second inner surface associated with the particular vane.

[0023] Unless explicitly defined herein, terms are to be construed in accordance with the plain and ordinary meaning as would be appreciated by one having skill in the art.

GENERAL DESCRIPTION OF EMBODIMENTS

[0024] In a general embodiment, a tapered rotary disc pump is disclosed. The pump includes a disc assembly comprising a first disc and a second disc, the first disc having a first inner surface and the second disc having a second inner surface, with the first and second discs forming a chamber between them. A plurality of standoffs may couple the first disc with the second disc. A plurality of vanes includes a first plurality of vanes disposed on the first inner surface and a second plurality of vanes disposed on the second inner surface. Each vane has a vane inner end and a vane outer end opposite the vane inner end, the vane outer end terminating at a disc periphery of the first disc or the second disc, and the vane inner end extending inwardly toward a center of the respective disc. Each vane also includes a vane leading face and a vane trailing face, the vane trailing face having an orthogonal configuration with the respective inner surface. At least one of the plurality of vanes tapers from the vane outer end toward the vane inner end, and further tapers from the respective inner surface toward the chamber.

[0025] In some embodiments, each of the plurality of vanes may taper from the vane outer end toward the vane inner end, and may further taper from the respective inner surface toward the chamber.

[0026] In some embodiments, the first disc may be in parallel alignment with the second disc.

[0027] In some embodiments, the first inner surface may be in parallel alignment with the second inner surface.

[0028] In some embodiments, the first disc may be concentrically aligned with the second disc.

[0029] In some embodiments, the first plurality of vanes may include a first quantity and the second plurality of vanes may include a second quantity, wherein the first quantity may equal the second quantity.

[0030] In some embodiments, each of the first plurality of vanes may be aligned with one of the second plurality of vanes such that two opposing vanes may be at equal radial positions during rotation of the tapered rotary disc pump.

[0031] In some embodiments, each vane outer end may form a surface alignment with the disc periphery of one of the first disc or the second disc.

[0032] In some embodiments, each of the plurality of standoffs may extend into one of the first plurality of vanes.

[0033] In some embodiments, each of the plurality of standoffs may extend into one of the second plurality of vanes.

[0034] In some embodiments, each of the plurality of standoffs may be orthogonal to the first disc and the second disc.

[0035] In some embodiments, the second disc may further comprise an inlet aperture.

[0036] In some embodiments, the pump may further comprise a rotor assembly coupled to the first disc.

[0037] In some embodiments, the vane leading face may further comprise a convex portion and a concave portion, wherein the concave portion may extend from the respective inner surface toward the convex portion, and the convex portion may extend from the concave portion to the vane trailing face.

[0038] In another general embodiment, a tapered rotary disc pump is disclosed. The pump includes a disc assembly comprising a first disc and a second disc, the first disc having a first inner surface and the second disc having a second inner surface, with the first and second discs forming a chamber between them. A plurality of standoffs couple the first disc with the second disc. A plurality of vanes includes a first plurality of vanes disposed on the first inner surface and a second plurality of vanes disposed on the second inner surface. Each vane has a vane inner end and a vane outer end opposite the vane inner end, the vane outer end terminating at a disc periphery of the first disc or the second disc, and the vane inner end extending inwardly toward a center of the respective disc. Each vane also includes a vane leading face and a vane trailing face, the vane trailing face having an orthogonal configuration with the respective inner surface. At least one of the plurality of vanes tapers from the vane outer end toward the vane inner end.

[0039] In some embodiments, each of the plurality of vanes may taper from the vane outer end toward the vane inner end.

[0040] In some embodiments, the first disc may be in parallel alignment with the second disc.

[0041] In some embodiments, the first inner surface may be in parallel alignment with the second inner surface.

[0042] In some embodiments, the first disc may be concentrically aligned with the second disc.

[0043] In some embodiments, the first plurality of vanes may include a first quantity and the second plurality of vanes may include a second quantity, wherein the first quantity may equal the second quantity.

[0044] In some embodiments, each of the first plurality of vanes may be aligned with one of the second plurality of vanes such that two opposing vanes may be at equal radial positions during rotation of the tapered rotary disc pump.

[0045] In some embodiments, each vane outer end may form a surface alignment with the disc periphery of one of the first disc or the second disc.

[0046] In some embodiments, each of the plurality of standoffs may extend into one of the first plurality of vanes.

[0047] In some embodiments, each of the plurality of standoffs may extend into one of the second plurality of vanes.

[0048] In some embodiments, each of the plurality of standoffs may be orthogonal to the first disc and the second disc.

[0049] In some embodiments, the second disc may further comprise an inlet aperture.

[0050] In some embodiments, the pump may further comprise a rotor assembly coupled to the first disc.

[0051] In another general embodiment, a tapered rotary disc pump is disclosed. The pump includes a disc assembly comprising a first disc and a second disc, the first disc having a first inner surface and the second disc having a second inner surface, with the first and second discs forming a chamber between them. A plurality of standoffs couples the first disc with the second disc. A plurality of vanes includes a first plurality of vanes disposed on the first inner surface and a second plurality of vanes disposed on the second inner surface. Each vane has a vane inner end and a vane outer end opposite the vane inner end, the vane outer end terminating at a disc periphery of the first disc or the second disc, and the vane inner end extending inwardly toward a center of the respective disc. Each vane also includes a vane leading face and a vane trailing face, the vane trailing face having an orthogonal configuration with the respective inner surface. At least one of the plurality of vanes tapers from the respective inner surface toward the chamber.

[0052] In some embodiments, each of the plurality of vanes may taper from the respective inner surface toward the chamber.

[0053] In some embodiments, the first disc may be in parallel alignment with the second disc.

[0054] In some embodiments, the first inner surface may be in parallel alignment with the second inner surface.

[0055] In some embodiments, the first disc may be concentrically aligned with the second disc.

[0056] In some embodiments, the first plurality of vanes may include a first quantity and the second plurality of vanes may include a second quantity, wherein the first quantity may equal the second quantity.

[0057] In some embodiments, each of the first plurality of vanes may be aligned with one of the second plurality of vanes such that two opposing vanes may be at equal radial positions during rotation of the tapered rotary disc pump.

[0058] In some embodiments, each vane outer end may form a surface alignment with the disc periphery of one of the first disc or the second disc.

[0059] In some embodiments, each of the plurality of standoffs may extend into one of the first plurality of vanes.

[0060] In some embodiments, each of the plurality of standoffs may extend into one of the second plurality of vanes.

[0061] In some embodiments, each of the plurality of standoffs may be orthogonal to the first disc and the second disc.

[0062] In some embodiments, the second disc may further comprise an inlet aperture.

[0063] In some embodiments, the pump may further comprise a rotor assembly coupled to the first disc.

[0064] In some embodiments, the vane leading face may further comprise a convex portion and a concave portion, wherein the concave portion may extend from the respective inner surface toward the convex portion, and the convex portion may extend from the concave portion to the vane trailing face.

[0065] Generally, the plurality of vanes is monolithically and integrally coupled to the first disc and the second disc to comply with most standards (i.e. API, ANSI, etc.) that require the impeller to comprise one single component casted. Alternatively, the plurality of vanes can be detachably coupled to the first disc and the second disc.

[0066] The disc assembly may comprise various metallurgies including WCB, Ductile Iron, CD4MCu, Super Duplex, High Chrome, and all alloys. Other metallurgies may also be used as can be appreciated by one having skill in the art.

[0067] While various details, features, and combinations are described in the illustrated embodiments, one having skill in the art will appreciate a myriad of possible alternative combinations and arrangements of the features disclosed herein. As such, the descriptions are intended to be enabling only, and non-limiting. Instead, the spirit and scope of the invention is set forth in the appended claims.

Illustrated Embodiments

[0068] Now, turning to the drawings, FIG. 1 shows a cross-section view of a conventional rotary disc pump (100). The rotary disc pump comprises a disc assembly (130) being a first disc (131) and a second disc (133) spaced apart by a clearance (142). The clearance forms a chamber (111) by a first inner surface (132) of the first disc and a second inner surface (134) of the second disc. The first disc and second disc are concentrically aligned and coupled together by a plurality of standoffs (140) that couple to both the first inner surface and the second inner surface. The first disc is coupled to a rotor assembly (120) at a center thereof. A housing (110) surrounds the disc assembly and forms a sealed alignment (121) with the rotor assembly. The rotor assembly is configured to rotate both the first disc and the second disc due to linkage by the plurality of standoffs. The second disc comprises an inlet aperture (113) disposed at a center of the second disc to allow entry of material into the rotary disc pump. The housing encapsulates both the first disc and second disc and further comprises an inlet (112) adjacent to said inlet aperture. The rotary disc pump comprises a pump axis (141) that is concentrically aligned with each of the first disc and the second disc. Both the first disc and the second disc further comprise vanes (135) disposed on the first inner surface and the second inner surface, respectively. The vanes sacrifice some material handling properties with the benefit of improved pumping efficiency over a flat rotary disc pump of equivalent dimensions and has better material and solid handling and greater stability than a standard centrifugal pump. The vanes enhance fluid movement by creating a channel that guides the fluid toward the pump outlet. This directed flow minimizes turbulence and random fluid motion which can cause energy losses. The vanes create a more controlled environment for pressure buildup by confining and guiding the fluid. The controlled pressure buildup reduces the likelihood of cavitation and other pressure-related inefficiencies. Furthermore, flat rotary disc pumps, fluid recirculation can occur where some of the fluid returns to the inlet side. The vanes reduce recirculation by ensuring the fluid flows a more linear and directed path from inlet to outlet.

[0069] FIG. 2-4 shows a tapered rotary disc pump (200) in accordance with a first illustrated embodiment. The tapered rotary disc pump comprises a disc assembly (230) having a first disc (231) concentrically aligned with a second disc (233). The first and second discs are spaced apart to form a chamber (212) wherein the first disc is fixedly coupled to the second disc by a plurality of standoffs (240). The first disc comprises a plurality of vanes (235) disposed on a first inner surface (232) of the first disc. Similarly, the second disc comprises a plurality of vanes (235) disposed on a second inner surface (234) of the second disc. Preferably the first disc comprises a number of vanes equal to the second disc. Each of the plurality of vanes on the first disc is aligned with one of the plurality of vanes on the second disc such that two opposing vanes are at equal radial positions during rotation of the tapered rotary disc pump.

[0070] Each vane (235) on both the first disc (231) and the second disc (233) comprises a tapered configuration in order to reduce medium turbulence within the chamber (212) to increase pump efficiency. Each vane extends inwardly from a respective inner surface (232; 234) toward the chamber. Additionally, each vane extends from a vane outer end (239) to a vane inner end (238). Each of the vane outer ends forms a surface alignment and is coplanar with a disc periphery (243) of an associated disc, and each of the vane inner end extends equally inwards towards a center of the associated disc. For the first disc, each of the associated vanes comprises the vane outer end forming a surface alignment with the disc periphery of the first disc and whose vane inner end terminates at a center portion corresponding to a rotor assembly. For the second disc, each of the associated vanes comprises the vane outer end forming a surface alignment with the disc periphery of the second disc and whose vane inner end terminates up to an inlet aperture (213) of the second disc.

[0071] Each vane (235) of the disc assembly (230) comprises a vane leading face (236) and a vane trailing face (237). The vane trailing face comprises an orthogonal configuration with an associated inner surface (232; 234). The vane leading face comprises a tapered configuration in two dimensions. The first dimension corresponds along the inner surface wherein the vane comprises a greater width at the disc periphery (243) and a lesser width closer to a center of the associated disc such that vane tapers inward from the disc periphery towards the center of the disc. The second dimension corresponds orthogonally from the inner surface wherein the vane comprises a greater width at the inner surface and a lesser width away from the inner surface such that the vane tapers inward from the inner surface. The tapered configuration of each vane reduces turbulence of the medium during rotation of the rotary disc pump to increase pump efficiency.

[0072] The vane leading face (236) of each of the plurality of vanes (235) further comprises a convex portion (240) and a concave portion (241). The concave portion extends upwards from the inner surface (232; 234) of the associated disc (231; 233), and the convex portion extends from the concave portion towards the vane trailing face (237). The base of each vane at the junction of the inner surface comprises a width defined as a vane disc width (253). The top of each vane where the convex portion meets the vane trailing face comprises a width defined as a vane chamber width (254) wherein the vane chamber width is less than the van disc width.

[0073] Preferably, each of the plurality of standoffs (240) extends into one of the plurality of vanes (235) for both the first disc (231) and the second disc (233). By having the plurality of standoffs avoid direct contact with the first and second inner surfaces (232; 234), an additional point of turbulence is prevented that would otherwise reduce pump efficiency. Furthermore, it is preferable for each of the plurality of standoffs to be orthogonal with the first disc and the second disc to mitigate additional turbulence.

[0074] Preferably, the vane outer end (239) of each of the plurality of vanes (235) terminates at the disc periphery (243) to ensure higher pump efficiency. The vane inner end (238) may extend as far inwards as possible to ensure flow distribution with the pump. On the first disc (231), the vane inner end may terminate at a center portion associated with the rotor assembly, and on the second disc (233) the vane inner end may terminate at the inlet aperture (213).

[0075] FIG. 5 shows a tapered rotary disc pump (300) in accordance with a second illustrated embodiment. The tapered rotary disc pump comprises a first disc (331), a second disc (333), and a chamber (312) disposed between a first inner surface (332) and a second inner surface (334) of the first disc and second disc, respectively. The first disc and the second disc form a disc assembly (330) joined together by a plurality of standoffs (340). The first inner surface and the second inner surface each comprise a plurality of vanes (335) utilized for improving pump efficiency. Each of the plurality of vanes comprises a tapered configuration in order to further improve pump efficiency. Testing showed that pump efficiency was able to increase from approximately 30% to 50% with the inclusion of the tapered configuration.

[0076] The tapered configuration comprises a tapering from a vane outer end (239) to a vane inner end (238), in addition to tapering from the vane at the inner surface (332; 334) towards the chamber (312). The vane outer end forms a coplanar surface alignment with a disc periphery (343) of the associated disc. A vane leading face (336) of each vane (335) comprises tapering in both directions while a vane trailing face (337) of each vane comprises an orthogonal relationship with the inner surface.

[0077] FIG. 6 shows a first disc (431) of a tapered rotary disc pump (400) in accordance with a third illustrated embodiment. The first disc comprises a first inner surface (433) with a plurality of vanes (435) having a tapered configuration. Each vane comprises a vane leading face (436) and a vane trailing face (437) defined by rotation of the first disc. Each vane extends from a vane outer end (439) towards a vane inner end (438) wherein the vane inner end terminates near a center of the first disc and the vane outer end forms a surface alignment with a disc periphery (434). Each vane projects upward from the first inner surface (432) and progressively tapers inward the further away from the inner surface such that a vane disc width (453) defined as a width of the vane at the first inner surface is greater than a vane chamber width (454) defined as a width of the vane disposed further away from the first inner surface. It will be appreciated by one having skill in the art that a corresponding second disc (not shown) comprises vanes properly aligned having the same tapered configuration.

[0078] FIG. 7 shows a first disc (531) of a of tapered rotary disc pump (500) in accordance with a fourth illustrated embodiment. The first disc comprises a first inner surface (533) with a plurality of vanes (535) having a tapered configuration. Each vane comprises a vane leading face (536) and a vane trailing face (537) defined by rotation of the first disc. Each vane extends from a vane outer end (539) towards a vane inner end (538) wherein the vane inner end terminates near a center of the first disc and the vane outer end forms a surface alignment with a disc periphery (543). Each vane tapers inward from the vane outer end to the vane inner end such that a vane outer width (552), defined as a width of the vane inner end, is greater than a vane inner width (551) defined as a width of the vane inner end. Furthermore, each vane tapers continuously inward such that each vane decreases in width the closer to the vane inner end. It will be appreciated by one having skill in the art that a corresponding second disc (not shown) comprises vanes properly aligned having a same tapered configuration.

FEATURE LIST

[0079] rotary disc pump (100; 200; 300; 400; 500) [0080] housing (110) [0081] chamber (111; 212; 312) [0082] inlet (112) [0083] inlet aperture (113; 213; 313) [0084] rotor assembly (120) [0085] sealed alignment (121) [0086] disc assembly (130; 230; 330) [0087] first disc (131; 231; 331; 431; 531) [0088] first inner surface (132; 232; 332; 432; 532) [0089] second disc (133; 233; 333) [0090] second inner surface (134; 234; 334) [0091] vane (135; 235; 335; 435; 535) [0092] standoff (140; 240; 340) [0093] pump axis (141) [0094] clearance (142) [0095] vane leading face (236; 336; 436; 536) [0096] vane trailing face (237; 337; 437; 537) [0097] vane inner end (238; 338; 438; 538) [0098] vane outer end (239; 339; 439; 539) [0099] convex portion (240) [0100] concave portion (241) [0101] disc periphery (243; 343; 443; 543) [0102] vane disc width (253; 453) [0103] vane chamber width (254; 454) [0104] vane inner width (551) [0105] vane outer width (552)