Hypotrochoidal positive displacement machine

Abstract

A positive displacement device includes an inner rotor and an outer rotor with intermeshing lobes. A point on each rotor traces an hypotrochoidal path relative to the other rotor. The tips of the outer rotor lobes contact the inner rotor at top dead center (TDC) and bottom dead center (BDC), creating areas of higher and lower pressure. Various elements may mold to other elements to form a seal.

Description

[Technical field]

[0001] This invention relates to an internal gear fluid transfer device. Summary of the Invention

[0002] The displacement device may include a housing, an inner rotor, and an outer rotor. The inner rotor may be fixed for rotation relative to the housing about a first axis and the outer rotor may be fixed for rotation relative to the housing about a second axis parallel to and offset from the first axis. The inner rotor has a radially outward projection and the outer rotor has a radially inward projection configured to mate with the radially outward projection of the inner rotor. The inner rotor, outer rotor and housing may collectively form a set of components arranged for relative movement in a plane perpendicular to the first axis, the set of components defining axially facing surfaces including at least one surface pair arranged to form an interface between a first axially facing surface and a second axially facing surface of at least one surface pairing, the first axially facing surface and the second axially facing surface being defined by different components of the set, and configured such that the first axially facing surface of at least one surface pair shapes, is shaped by, or both, the second axially facing surface of the at least one surface pair.

[0003] Various embodiments may include any one or more of the following features: the radially inward protrusions of the outer rotor may seal against the radially outward protrusions of the inner rotor at a bottom dead center zone including bottom dead center (BDC) of the positive displacement device and against troughs between the radially outward protrusions of the inner rotor at a top dead center zone including top dead center (TDC) of the positive displacement device, the BDC and TDC seal zones separating the positive displacement device into high pressure and low pressure regions. The radially inward protrusions of the outer rotor may be configured to generate substantially equal and opposite torques on the outer rotor in combination with the seal of the radially inward protrusions of the outer rotor against the inner rotor as a result of their similar surface areas exposed to high pressure fluid at TDC and BDC. Two consecutive radially inward protrusions of the outer rotor and two consecutive zones between the radially outward protrusions of the inner rotor, respectively, may be shaped such that a seal is maintained between the inner rotor and the outer rotor in a chamber beyond TDC to provide for internal expansion of the compressed fluid past TDC. Each of the two consecutive radially outward protrusions of the inner rotor may be shaped such that a seal is maintained between the inner rotor and the outer rotor in a chamber beyond the BDC to provide internal compression of the fluid passing through the BDC. The at least one surface pair may include a first housing surface pair having a first surface of the housing and an outer surface of one of the inner rotor and the outer rotor arranged to form a first housing interface, the first surface of the housing configured to mold, be molded by, or both the outer surface of the one of the inner rotor and the outer rotor. The housing includes a port plate, and the at least one surface pair includes a port plate surface pair having a surface of the port plate and an outer surface of one of the inner rotor and the outer rotor arranged to form a port plate interface, the surface of the port plate configured to mold, be molded by, or both the outer surface of the one of the inner rotor and the outer rotor.The outer surface of one of the inner rotor and the outer rotor may be defined by an end plate of one of the inner rotor and the outer rotor. The outer surface of one of the inner rotor and the outer rotor may be an outer surface of the outer rotor. There may also be a port plate interface fluid supply channel configured to supply fluid under pressure to the port plate interface for debris removal. There may also be a proud port plate interface element on the surface of the port plate or on the inner rotor and on the outer surface of one of the outer rotors, the proud port plate interface element being arranged to shape the outer surface of one of the inner rotor and the outer rotor when the proud port plate interface element is on the surface of the port plate, and the proud port plate interface element being arranged to shape the surface of the port plate when the proud port plate interface element is on the outer surface of one of the inner rotor and the outer rotor. The proud port plate interface element may have a helical shaped port plate interface shaping edge, the port plate interface shaping edge being oriented to push shaped debris radially outward from the port plate interface when the axially facing surface of the port plate surface pair moves in the direction of expected relative motion during use of the positive displacement device. An outer surface of one of the inner and outer rotors may have a protruding port plate interface element. The surface of the port plate may include a plastic material over a metal backing plate. There may be an actuator that positions the surface of the port plate in contact or proximity to a surface of one of the inner and outer rotors. The actuator may include a chamber in a housing configured to receive pressurized fluid, the port plate in contact with the chamber to act as a piston. There may be a purge valve connecting the chamber to an inlet of the machine. There may be a biasing element biasing the port plate against a stop in a direction away from the outer surface of one of the inner and outer rotors.At least one surface pair may include a first rotor surface pair having an inner rotor first surface and an outer rotor first surface arranged to form a first rotor interface, the outer rotor first surface being configured to be molded by, molded with, or both. The outer rotor first surface may be defined by an outer rotor end plate. There may be a first rotor interface fluid supply channel configured to supply fluid under pressure to the first rotor interface for debris removal. There may be a protruding first rotor interface element on the inner rotor first surface or the outer rotor first surface, where if the protruding first rotor interface element is on the outer rotor first surface, the protruding first rotor interface element is arranged to mold the inner rotor first surface, and where if the protruding first rotor interface element is on the inner rotor first surface, the protruding first rotor interface element is arranged to mold the outer rotor first surface. The protruding first rotor interface elements may have spiral-shaped first rotor interface shaping edges oriented to push shaped debris radially outwardly from the first rotor interface when the surfaces of the first rotor surface pair move in a direction of expected relative motion during use of the positive displacement device. The outer rotor first surface may have the protruding first rotor interface elements. At least one surface pair includes a second rotor surface pair having an inner rotor second surface and an outer rotor second surface arranged to form a second rotor interface, the outer rotor second surface configured to shape, be shaped by, or both the inner rotor second surface. The outer rotor second surface may be defined by an outer rotor second end plate. The second rotor interface fluid supply channel may be configured to supply fluid under pressure to the second rotor interface for debris removal.There may be a protruding second rotor interface element on the second surface of the inner rotor or the second surface of the outer rotor, the protruding second rotor interface element being arranged to shape the second surface of the inner rotor when the protruding second rotor interface element is on the second surface of the outer rotor, and the protruding second rotor interface element being arranged to shape the second surface of the outer rotor when the protruding second rotor interface element is on the second surface of the inner rotor. The protruding second rotor interface element may have a helical shaped second rotor interface shaping edge, the second rotor interface shaping edge being oriented to push shaping debris radially outwardly from the second rotor interface when the surfaces of the second rotor surface pair move in the direction of expected relative motion during use of the positive displacement device. The second surface of the outer rotor may have a protruding second rotor interface element. At least one surface pair may include a housing surface pair having an axially facing housing surface and a corresponding axially facing surface of at least one of the inner rotor or the outer rotor arranged to form a housing interface, the axially facing housing surface configured to mold, be molded by, or both, the corresponding axially facing surface. There may be an interface fluid supply channel configured to supply fluid under pressure to the housing interface for debris removal. There may be a protruding housing interface element on the axially facing housing surface or on the corresponding axially facing surface, the protruding housing interface element being arranged to mold the corresponding axially facing surface when the protruding housing interface element is on the axially facing housing surface, and the protruding housing interface element being arranged to mold the axially facing housing surface when the protruding second rotor interface element is on the corresponding axially facing surface. The protruding housing interface element may have a helical shaped housing interface shaping edge, the second housing shaping edge oriented to push molded debris in a radially outward direction from the housing interface when the surfaces of the housing surface pair move in the direction of expected relative motion during use of the positive displacement device. An axially facing surface of at least one of the inner rotor or outer rotor may have a protruding second rotor interface element.There may be a fluid supply channel arrangement that may include a fluid supply channel that supplies fluid to any one or more of the above-mentioned interfaces for debris removal. The fluid supply channel arrangement may include, for example, a flow path through the shaft of the inner rotor. The fluid supply channels to the different interfaces may be connected together or separately and, if separate, may supply the same or different fluids. The fluid may be the same as or different from the working fluid of the positive displacement device. The outer rotor may be configured to provide a clearance between the root of the inward protrusion of the outer rotor and the tip of the outward protrusion of the inner rotor, the clearance being selected to accommodate ice that accumulates between the protrusions of the outer rotor. There may be an attachment mechanism for attaching the positive displacement device to an external surface or structure such that the first axis has a non-vertical, non-horizontal orientation such that the discharge port of the positive displacement device is located substantially at the bottom of the active volume of the positive displacement device. The orientation of the first axis may be between 1 degree and 45 degrees from vertical. The inner rotor may include a formable material, for example a machinable or polishable material. The inner rotor may include polytetrafluoroethylene (PTFE). There may be a screen disposed in contact with the fluid flow to the positive displacement device, the screen may be disposed to have a screen temperature that cools more rapidly than the fluid-facing surface of the outer rotor when the positive displacement device is shut down after use. The screen may be thermally connected to a heat sink exposed to ambient temperature. The radially inward projection may have leading and trailing portions configured to contact the radially outward projection of the inner rotor between the seal zones. There may be flow passages disposed to prevent formation of a sealed secondary chamber between the radially outward projection of the inner rotor and the radially inward projection of the outer rotor at or near top dead center (TDC). The trailing portion of the radially inward outer rotor projection may provide relative rotational positioning of the outer and inner rotors and may provide a contact ratio between the rotors in one or more rotational directions.A leading portion of the radially inward outer rotor projection may provide relative rotational positioning of the outer and inner rotors and may provide a mesh ratio between the rotors in one or more rotational directions. The radially outward projection of the inner rotor may have a formable seal zone surface including a formable material, and the portion of the outward projection of the inner rotor that provides rotational positioning relative to the outer rotor may also include a formable material. Each of the axially facing surfaces of the at least one surface pair may include an abradable material and may be configured to mold the other of the axially facing surfaces of the at least one surface pair.

[0004] The positive displacement device may have a housing, an inner rotor, and an outer rotor. The inner rotor may have a number of outward protrusions, and the outer rotor may have a number of inward protrusions. The inner rotor may be fixed to rotate relative to the housing about a first axis, and the outer rotor may be fixed to rotate relative to the housing about a second axis parallel to and offset from the first axis. The number of inward protrusions of the outer rotor may be, for example, one more than the number of outward protrusions of the inner rotor. The outward protrusions of the inner rotor and the inward protrusions of the outer rotor may intermesh, and the outer rotor and the inner rotor are configured to rotate at a relative ratio of rotational speeds defined by the ratio of the number of inner rotor protrusions to the number of protrusions of the outer rotor. The inward-most tips of the outer rotor may have inward-most tips that define a hypotrochoid path with respect to the inner rotor, the inner rotor having tip seal zones at the tips of the outward-most tips and trough seal zones in the troughs between the outward-most tips, the tip seal zones and trough seal zones positioned to seal against the inner-most tips of the outer rotor protrusions as the inner-most tips trace the hypotrochoid path.

[0005] In various embodiments, any one or more of the following features may be included: the tip seal zone may occur at a bottom dead center zone including bottom dead center (BDC) of the positive displacement device, and the trough seal zone may occur at a top dead center zone including top dead center (TDC) of the positive displacement device, the BDC and TDC seal zones separating the positive displacement device into high pressure and low pressure regions. The radially inward protrusions of the outer rotor may be configured to generate substantially equal and opposite torques on the outer rotor in combination with the sealing of the radially inward protrusions of the outer rotor against the inner rotor as a result of their similar surface areas exposed to high pressure fluid at TDC and BDC. Two consecutive radially inward protrusions of the outer rotor and two consecutive zones between the radially outward protrusions of the inner rotor, respectively, may be shaped such that a seal is maintained between the inner rotor and the outer rotor in a chamber beyond TDC to provide for internal expansion of the compressed fluid past TDC. Each of the two successive radially outward protrusions of the inner rotor may be shaped so that a seal is maintained between the inner rotor and the outer rotor in a chamber beyond the BDC to provide internal compression of the fluid passing through the BDC. A screen may be arranged to contact the fluid flow to the positive displacement device, the screen being arranged to have a screen temperature that cools more rapidly than the fluid-facing surface of the outer rotor when the positive displacement device is shut down after use. The screen may be thermally connected to a heat sink exposed to ambient temperature. The sealing zone of the tips of the outward protrusions or the sealing zone of the trough between the outward protrusions or both may be configured with the innermost tip of the outer rotor shaped by the innermost tip of the outer rotor. The first inward protrusion of the outer rotor has a first tip shape that is different from a second tip shape of the second inward protrusion of the outer rotor, the first tip shape having a sharper angle of incidence with the tip of the outward protrusion of the inner rotor in the direction of relative motion at bottom dead center (BDC) and the second tip shape having a sharper angle of incidence at a trough between the outward protrusions of the inner rotor in the direction of relative motion at top dead center (TDC).The first tip and the second tip may be arranged such that the first tip and the second tip trace a common endotrochoidal path relative to the inner rotor. The inward protrusions of the outer rotor may include a plurality of sets of protrusions, each of the protrusions in each set having a common geometric shape, and the number of protrusions of the outer rotor is a multiple of the number of the plurality of sets. The innermost tips of the inward protrusions of the outer rotor may be made of a harder material than the tip seal zone and the trough seal zone, and the innermost tips of the inward protrusions of the outer rotor may be configured to shape the tip seal zone and the trough seal zone during operation of the positive displacement device. The inward protrusions of the outer rotor may be tapered to a sharp edge at the innermost tip. The innermost tip of the outer rotor may be configured with rounded surfaces. Points on the rounded surface may still define an epitrochoidal path, the inner rotor seal surface may be designed to seal against the rounded surface of the outer rotor tip, and the tips of the outer rotor fins may still be shaped to include, e.g., wear-in, the inner rotor seal surface, depending on the embodiment. The tip seal zone or the trough seal zone or both may have radially movable seals. The radially movable seals may be configured to be radially movable at a first temperature and radially fixed or tighter fit in their grooves at a second temperature. The inwardly facing outer rotor protrusions may have leading and trailing portions configured to contact the outwardly facing inner rotor protrusions between the tip seal zone and the trough seal zone. There may be flow passages positioned to prevent formation of a sealed secondary chamber between the outwardly facing inner rotor protrusions and the inwardly facing outer rotor protrusions at or near top dead center (TDC). For purposes of this disclosure, a chamber is defined as a volume formed by contact or close contact interaction, such as a pair of such interactions, between two or more elements, such as an inner rotor and an outer rotor. The trailing portion of the inwardly extending outer rotor projection may provide relative rotational positioning of the outer rotor and the inner rotor and may provide a mesh ratio between the rotors in one or more rotational directions.The leading portion of the inwardly extending outer rotor projection may provide relative rotational positioning of the outer and inner rotors and may provide a mesh ratio between the rotors in one or more rotational directions. One of the troughs between the outwardly extending projections may have a shape such that a sealed chamber is maintained beyond top dead center (TDC) to provide for internal expansion of fluid passing TDC. The other troughs, e.g., all of the troughs between the outwardly extending projections, may have a similar shape. The inner rotor projection of the outwardly extending projection may have a shape such that a sealed chamber is maintained beyond bottom dead center (BDC) to provide for internal compression of fluid passing BDC. The other projections, e.g., all of the outwardly extending projections, may have a similar shape. The tip seal zone, the trough seal zone, or both may comprise a moldable material, and the portion of the inner rotor outwardly extending projection that provides rotational positioning relative to the outer rotor may also comprise a moldable material.

[0006] A method of running-in a positive displacement device may include providing a positive displacement device having an inner rotor and an outer rotor, the inner rotor having a radially movable seal configured to seal against a radially innermost tip of an inward protrusion of the outer rotor, the radially movable seal being radially movable or fixed depending on a temperature of the seal. The radially movable seal may be located at the tip of the outward protrusion of the inner rotor or in a trough between the outward protrusions of the inner rotor or both. The method further includes operating the positive displacement device at a first temperature, allowing the radially movable seals to advance radially to respective top-out positions contacting the radially innermost tips of the inward protrusions of the outer rotor when the positive displacement device operates at the first temperature, for example, thereafter operating the positive displacement device at a second temperature, the radially movable seals being fixed at their respective top-out positions when the positive displacement device is operated at the second temperature.

[0007] Various embodiments may include any one or more of the following features: When the positive displacement device operates at a first temperature, the radial advancement of the radially movable seal may be caused by centrifugal force. The radially movable seal may be biased radially inward. For example, the radially movable seal may be biased radially inward by a spring. The seal may alternatively be biased radially outward, for example, by a spring, such that the radial advancement occurs under a biasing force. The seal may be disposed in grooves, the radially movable seals being radially movable at a first temperature and fixed or tighter within those grooves at a second temperature due to differential thermal expansion of the seal relative to the material defining the groove. A fixed seal may, for example, allow a position to be set that establishes a small gap. A tighter seal may, for example, reduce a leak path around the seal in the groove.

[0008] A further method of running-in a positive displacement machine includes providing a positive displacement machine having a housing and an inner rotor having a radially outward protrusion, the inner rotor fixed for rotation relative to the housing about a first axis, an outer rotor having a radially inward protrusion configured to mesh with the radially outward protrusion of the inner rotor, the outer rotor fixed for rotation relative to the housing about a second axis parallel to and offset from the first axis, the inner rotor having a first axially facing surface and a second axially facing surface. The method may also include operating the positive displacement machine under conditions such that the first axially facing surface interferes with a first corresponding axially facing surface of the outer rotor or housing such that the first corresponding axially facing surface shapes the first axially facing surface, or operating the positive displacement machine under conditions such that the second axially facing surface interferes with a second corresponding axially facing surface of the outer rotor or housing such that the second corresponding axially facing surface shapes the second axially facing surface, or operating the positive displacement machine under conditions such that both occur. The positive displacement machine may then be operated under conditions such that at least some of the interference does not occur.

[0009] Various embodiments may include any one or more of the following features: the inner rotor may be constructed to cause the above-mentioned interference when the positive displacement device is operated as constructed, and subsequent operation without the interference may be due to shaping of the inner rotor when the positive displacement device is operated as constructed. The condition under which the interference occurs may be a condition under which the inner rotor has a first temperature, and the inner rotor may have a second temperature during subsequent operation without the interference that is different from the first temperature.

[0010] Yet another method of running-in a positive displacement machine may include providing a positive displacement machine having a housing and an inner rotor having a radially outward protrusion, the inner rotor fixed for rotation relative to the housing about a first axis, an outer rotor having a radially inward protrusion configured to mate with the radially outward protrusion of the inner rotor, the outer rotor fixed for rotation relative to the housing about a second axis parallel to and offset from the first axis, the housing including a port plate having an axially facing surface of the port plate facing a corresponding axially facing surface of the inner rotor or the outer rotor. The method may also include operating the positive displacement machine under conditions such that the axially facing surface of the port plate interferes with the corresponding axially facing surface of the inner rotor or the outer rotor to cause the axially facing surface of the port plate to mold to the corresponding axially facing surface, and then operating the positive displacement machine without interference between the axially facing surface of the port plate and the corresponding axially facing surface.

[0011] Various embodiments may include any one or more of the following features: the port plate may be constructed to cause interference when the positive displacement device is operated as constructed, and subsequent operation without interference may result from shaping of the port plate when the positive displacement device is operated as constructed. The condition in which an axially facing surface of the port plate interferes with a corresponding axially facing surface of the inner rotor or outer rotor may be a condition in which the port plate has a first temperature, and the port plate may have a second temperature different from the first temperature during subsequent operation without interference. A method of clearing ice from a positive displacement machine may be applied to a positive displacement machine having a housing, an inner rotor having a radially outward protrusion, the inner rotor being fixed for rotation relative to the housing about a first axis, and an outer rotor having a radially inward protrusion configured to mesh with the radially outward protrusion of the inner rotor, the outer rotor being fixed for rotation relative to the housing about a second axis parallel to and offset from the first axis, or any of the positive displacement machines described above. The method includes the steps of operating the positive displacement machine, where an internal temperature of the positive displacement machine during operation is greater than 0° C., stopping operation of the positive displacement machine, monitoring the internal temperature of the positive displacement machine over a cooling period as the internal temperature of the positive displacement machine cools toward an ambient temperature below 0° C., and upon detecting that the internal temperature of the positive displacement machine is approaching 0° C., rotating the positive displacement machine to move water in the positive displacement machine out of the positive displacement machine, for example by rotating the rotor of the positive displacement machine to centrifuge condensed water in the positive displacement machine out of the rotor of the positive displacement machine. Detecting that the internal temperature of the positive displacement device is approaching 0°C may be performed, for example, by detecting that the internal temperature reaches a threshold temperature, or, for example, by detecting that a temperature trend of the internal temperature leads to 0°C or a different temperature threshold within a time threshold. The positive displacement device may include a screen arranged to filter the flow of fluid to the positive displacement device, the screen arranged to have a screen temperature lower than the device temperature of the positive displacement device during a cool down period.

[0012] These and other aspects of the apparatus and methods are set forth in the claims. [Brief description of the drawings]

[0013] Embodiments are now described with reference to the figures, where like reference characters indicate, by way of example, like elements throughout.

[0014] [Figure 1]FIG. 2 is an exploded isometric view of an exemplary fluid transfer device showing a housing, a port plate, an outer rotor, and an inner rotor.

[0015] [Diagram 2] 2 is a top view of a port plate of the exemplary fluid transfer device of FIG. 1.

[0016] [Diagram 3] 2 is a top view of the exemplary fluid transfer device of FIG. 1 showing the inner and outer rotors and the housing.

[0017] [Figure 4] 2 is a bottom view of the housing of the exemplary fluid transfer device of FIG. 1 showing the intake and exhaust ports and the port plate adjustment screw.

[0018] [Diagram 5] 1 is an isometric view of an assembly of components of a further exemplary fluid transfer device including an inner rotor having radially movable apex seals and an outer rotor end plate;

[0019] [Figure 6] 6 is an isometric cross-sectional view of the further exemplary fluid transfer device of FIG. 5 showing an input shaft, an inner rotor, an outer rotor, and an end plate.

[0020] [Figure 7] 6 is an isometric cross-sectional view of the further exemplary fluid transfer device of FIG. 5 showing the port plate, the intake port, and the exhaust port.

[0021] [Figure 8] FIG. 2 is a cross-sectional view of another exemplary fluid transfer device showing an inner rotor, an outer rotor, an input shaft, a port plate, and a housing.

[0022] [Figure 9] 1 is a flow chart illustrating a method performed on a fluid transfer device.

[0023] [Figure 10] FIG. 2 is a schematic diagram of the hypotrochoidal path traced by the ends of the outer rotor lobes relative to the inner rotor.

[0024] [Figure 11] FIG. 11 is a top view showing a schematic diagram of the hypotrochoidal path shown in FIG. 10 traced by the tips of the outer rotor lobes superimposed on the inner and outer rotors of an exemplary machine.

[0025] [Figure 12] FIG. 2 is a top view of an exemplary machine showing the driving surfaces of the inner rotor and the corresponding driven surfaces of the outer rotor.

[0026] [Figure 13] FIG. 6 is a top view of the inner and outer rotors of the exemplary machine of FIG. 5, showing the hypotrochoidal path traced by the tip of the outer rotor protrusion.

[0027] [Figure 14] FIG. 14 is an isometric view of the inner rotor and outer rotor shown in FIG.

[0028] [Figure 15] FIG. 2 is a top view of the inner and outer rotors of an exemplary machine, where the inner rotor has seven outward lobes and the outer rotor has eight inward lobes.

[0029] [Figure 16] FIG. 2 is a top view of the inner and outer rotors of an exemplary machine, the inner rotor having 11 outward lobes and the outer rotor having 12 inward lobes.

[0030] [Figure 17]FIG. 1 is a top view of an exemplary machine having an inner rotor with 9 outward lobes and an outer rotor with 10 inward lobes.

[0031] [Figure 18] FIG. 18 is an enlarged top view of the inner and outer protrusions of the machine of FIG. 17 meeting near bottom dead center (BDC) showing a detailed view of the seal / formed interaction between the inner and outer rotors.

[0032] [Figure 19] FIG. 4 is an enlarged top view of the forming edge of the outer rotor protrusion.

[0033] [Figure 20] FIG. 1 is a diagram of the protrusion of the outer rotor in forming contact with the inner rotor near top dead center (TDC).

[0034] [Figure 21] FIG. 13 is a top view near the BDC of the inward protrusions of the inner rotor in an exemplary machine showing two different types of formed edges on alternating protrusions of the outer rotor.

[0035] [Figure 22] FIG. 22 is a top view of the example machine of FIG. 21 having an inner rotor with 9 outward protrusions and an outer rotor with 10 inward protrusions, with adjacent outer rotor protrusions having different formed edges.

[0036] [Diagram 23] FIG. 22 is an enlarged top view showing the formed edge of the outer rotor protrusion of the embodiment of FIG.

[0037] [Figure 24] FIG. 11 is a top view overlay of two different outer rotor forming edges of another example machine to show that the tips seal in the same location.

[0038] [Diagram 25]FIG. 23 is an isometric exploded view of the exemplary machine of FIG.

[0039] [Figure 26] FIG. 26 is an isometric exploded view of an end plate of the example machine of FIG. 25 showing mold features.

[0040] [Figure 27] 25 is an isometric exploded view of the exemplary machine of FIG. 22 showing a different isometric perspective view than FIG. 25.

[0041] [Figure 28] FIG. 23 is a first isometric exploded view of the outer rotor of the exemplary machine of FIG. 22 showing the non-sealing portions and molded features on the axial face of the outer rotor that provide flow paths to prevent sealing of the secondary chamber.

[0042] [Figure 29] FIG. 23 is an isometric exploded view of selected components of the example machine of FIG.

[0043] [Diagram 30] FIG. 23 is a bottom view of the outer rotor of the example machine of FIG. 22 showing molded features on the axial surface of the outer rotor.

[0044] [Diagram 31] FIG. 23 is a second isometric view of the outer rotor of the exemplary machine of FIG. 22 showing molded features on the axial surface of the outer rotor.

[0045] [Diagram 32] FIG. 30 is an isometric view showing the outer rotor end face and inner rotor assembly of the example machine of FIG. 29 with mold features shown on the outer rotor end plate.

[0046] [Diagram 33] FIG. 13 is a top view of the outer rotor showing radial and axial molding features.

[0047] [Diagram 34] FIG. 34 is a top view of an outer rotor having an alternative molded feature design to that shown in FIG. 33, also showing the non-sealing portion that provides the fluid channels.

[0048] [Diagram 35] FIG. 2 is a top view of the outer rotor of an exemplary machine having an inner rotor with 9 outward protrusions and an outer rotor with 10 inward protrusions, showing axial mold features.

[0049] [Diagram 36] FIG. 2 is a cross-sectional view of an exemplary machine having an inner rotor with 9 outward lobes and an outer rotor with 10 inward lobes, showing ice removal components.

[0050] [Figure 37] FIG. 1 is a schematic diagram illustrating an apparatus including a mesh screen for reducing ice buildup in cold operating conditions.

[0051] [Figure 38] FIG. 1 is a cross-sectional view of an exemplary machine showing an inner rotor with 9 outward lobes and an outer rotor with 10 inward lobes, including a cross-sectional view of the unsealed flow passages on the outer rotor.

[0052] [Figure 39] FIG. 45 is an enlarged side cross-sectional view of an exemplary machine showing the port plate, also shown in FIG. 44, which translates when pressurized fluid is applied to the corresponding port.

[0053] [Diagram 40] FIG. 2 is a first isometric view of a port plate having a multi-part construction.

[0054] [Diagram 41] FIG. 41 is a second isometric view of the port plate of FIG.

[0055] [Diagram 42] FIG. 13 is an isometric view of an alternative port plate having a multi-part construction.

[0056] [Diagram 43] FIG. 13 is a cross-sectional view of an exemplary machine showing a port plate that moves axially by adjusting a screw.

[0057] [Diagram 44] FIG. 1 is a cross-sectional view of an exemplary machine including a port plate that translates when a corresponding port provides pressurized fluid.

[0058] [Diagram 45] FIG. 1 is an enlarged cross-sectional view of an exemplary machine showing a port plate arranged to translate toward the outer rotor.

[0059] [Figure 46] 39 is a cross-sectional view of the exemplary machine shown in FIG. 38 from a different axial direction.

[0060] [Figure 47] FIG. 36 is a second cross-sectional view of the exemplary machine shown in FIG. 35 taken from a different axial direction showing an axial non-sealing portion that prevents sealing of the secondary chamber.

[0061] [Figure 48] FIG. 44 is an enlarged cross-sectional view of the exemplary machine shown in FIG. 43 with passageways throughout the machine that deliver pressurized air to the forming area of ​​the machine and carry swarf away from the machine.

[0062] [Figure 49] 1 is a cross-sectional view of another exemplary machine having passageways throughout the machine for delivering pressurized air to the forming area of ​​the machine and carrying swarf away from the machine, with the swarf removal exhaust port removed; FIG.

[0063] [Figure 50] FIG. 50 is a cross-sectional view of the exemplary machine shown in FIG. 49 with a swarf removal exhaust port inserted.

[0064] [Figure 51] FIG. 1 is an isometric view of an exemplary machine housing including an input shaft, an intake port, and an exhaust port.

[0065] [Figure 52] FIG. 1 is a side cross-sectional view of an exemplary machine having an inner rotor and an outer rotor that interact axially on only one side, with both rotors interacting with an axial surface of the housing on the opposite side;

[0066] [Diagram 53] FIG. 53 is a side cross-sectional view of an exemplary machine similar to that of FIG. 52, but with the axes of the inner and outer rotors angled approximately 45 degrees from vertical to aid in purging fluids such as water from the chamber.

[0067] [Figure 54] 4 is a flow chart illustrating an exemplary method for preventing ice formation in a positive displacement device.

[0068] [Figure 55] 4 is a flow chart illustrating an exemplary method of break-in in a positive displacement device.

[0069] [Figure 56] FIG. 1 is a cross-sectional view of an exemplary machine having two surface pairs between the inner and outer rotor combination and the housing.

[0070] [Figure 57] FIG. 57 is a cross-sectional view of the exemplary machine shown diagrammatically in FIG. 56 showing the housing sealing against the inner rotor and outer rotor.

[0071] [Figure 58] FIG. 58 is an isometric view of the housing shown in FIG. 57 sealing against the inner and outer rotors.

[0072] [Figure 59] FIG. 59 is another isometric view of the housing shown in FIG. 58 showing the exterior of the housing including the intake and exhaust ports. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0073] Minor changes may be made to the embodiments described herein without departing from the scope of the claims.

[0074] Disclosed herein are configurations, design methods, and variations for pumps or compressors or expanders or related devices that, in some embodiments, can provide low internal leakage, low internal friction, low manufacturing tolerance requirements, low wear during operation, and high efficiency.

[0075] A non-limiting exemplary embodiment of the device is shown in FIG. 1 in a simplified exploded view. Such a device may have, among other components, an outer rotor 0100 whose axis is parallel to, but not collinear with, the axis of the inner rotor 0105. The outer rotor may have, among other features, radially inward protrusions 0110 in shapes referred to herein as fins. Points on these fins 0110 of the outer rotor 0100 trace a hypotrochoidal path relative to the inner rotor 0105 when the device is in operation. This hypotrochoidal motion, in conjunction with the outer rotor fin shape and other features disclosed herein, may be used to derive the device shape required to achieve the operational advantages discussed throughout this document.

[0076] The inner rotor 0105 may have, among other features, radially outward projections 0115 (hereinafter "lobes"), some of whose form is derived from that of the fins 0110, such that the fins 0110 trace a hypotrochoidal path relative to the inner rotor 0105. It is also possible to start with the inner rotor 0105 and derive the form of the fins 0110 on the outer rotor 0100. It is also possible to derive the form of the fins and the lobes in parallel. The derivation of the inner rotor lobe shape can be done accurately at the design stage and manufactured without further shaping of the inner rotor lobes during operation. The derivation of these surfaces can also be done approximately, with some intended interference, at operating conditions during the design stage, such that the shaping of the surfaces is done roughly during manufacturing and then more accurately during operation by self-shaping effects as described below.

[0077] The device can operate as a pump or compressor, or as a hydraulic motor or expander. Operation of the device as a pump or compressor is as follows.

[0078] Fluid entering the device through the intake port 0125 is drawn through the port plate 0130 into one or more chambers 0135 (such as those labeled) formed by contact or close contact interaction between the inner rotor 0105 and the outer rotor 0100. As the rotors rotate in the direction indicated by the arrow 0140 relative to the housing 0155, fluid is drawn into the device via expansion of the one or more chambers 0135.

[0079] The term "seal" as used in this document indicates that the components have a small enough gap between them that rotation at the operating speed and pressure of the device significantly increases the resistance to flow through this gap from an area of ​​high pressure to an area of ​​low pressure such that positive displacement results. A seal does not need to be zero leakage.

[0080] As the rotors 0100 and 0105 rotate and the volume of the chambers increases, fluid fills the chamber or chambers until the volume of the chamber or chambers reaches an ideal value. In many cases, priority is given to drawing fluid into the chambers until the volume of the fluid reaches a maximum value. The point of rotation where the chamber reaches its maximum value is referred to in this disclosure as bottom dead center (BDC). For example, the chamber 0135 is near or at BDC as shown in FIG. 1. If the working fluid (the fluid whose flow rate is controlled by the device) is an incompressible fluid such as water or oil, the timing of opening and closing the ports is preferably arranged so that the point where the chamber rotates to the BDC position and is sealed from the intake port is at or near the point where the chamber opens to the exhaust port. Similarly, if the working fluid is a compressible fluid or if it is desired to increase the pressure of the compressible fluid before the chamber opens to the exhaust port, the timing of opening and closing the ports is preferably arranged so that the point where the chamber rotates to the BDC position and is sealed from the intake port is the maximum volume position of the chamber and the volume is reduced to achieve internal compression before the same chamber opens to the exhaust port. In other words, for incompressible fluids, it is important to ensure that the chamber is always or nearly always in communication with either the intake or exhaust port when the chamber changes volume, and that no or very little compression or expansion of the fluid is implied by the change in volume of the chamber at the BDC, and in fact, to reduce losses due to friction that occurs when the incompressible fluid is forced through small gaps in or out of the chamber as the volume changes. Alternatively, for compressible working fluids in applications where it is desired to increase the pressure of the working fluid, it is preferable to maintain a seal in each chamber until the chamber volume is reduced from the BDC and the pressure of the fluid increases to a desired level, such as the pressure at the compressor exhaust port.

[0081] The position where the chamber has the smallest volume is referred to as top dead center (TDC) in this disclosure. For example, the chamber 0145 is at or near TDC as shown in FIG. 1. After the fluid in the chamber is exhausted from the exhaust port, at or near the minimum volume position (TDC) the chamber may become sealed from the exhaust port. For incompressible fluids, the chamber may be open to the intake port at or near this point. For compressible fluids, it may be desirable to keep the chamber sealed for an angle of rotation that allows the compressed fluid to expand to a pressure close to or equal to the pressure of the intake port. Fluid is exhausted from the compression side of the device through the stationary port plate 0130 and from the device via the exhaust port 0150 in the housing 0155. Additional sealing beyond top or bottom dead center may be provided by an inner rotor protrusion having a shape with a seal zone that extends to such a length that two seals surrounding the chamber between the inner and outer rotors are maintained while the chamber changes volume. For example, as seen in Figure 3, the inner rotor trough of this embodiment allows the seal to be maintained beyond top dead center (TDC) to provide for internal expansion of the compressed fluid passing TDC. Also, as shown in Figure 3, the inner rotor lobe protrusion of this embodiment has a shape that allows the seal to be maintained beyond bottom dead center (BDC) to provide for internal compression of the fluid passing BDC. To allow for this internal compression and expansion, the chamber rotation chamber port (not shown in this figure, but shown in Figure 5 as 0515) that allows the chamber to communicate with the inlet and exhaust ports is preferably closed at or near BDC and TDC and remains closed long enough to allow the desired pressure to be reached within the sealed chamber.

[0082] The disclosed invention may also incorporate additional features or components not shown in FIG. 1 for clarity.

[0083] In Figure 3, the preferred direction of rotation of the inner rotor 0305 and the outer rotor 0310 in this non-limiting exemplary embodiment is indicated by the arrow 0315. As shown in Figures 2, 3 and 4, the port plate 0200 may have an inlet port 0205, which may be exposed to one or more chambers expanding as the inner rotor 0305 and the outer rotor 0310 rotate, and may be connected to a port channel 0210 that may act as a manifold to combine and smooth the flow from the multiple chambers. Similarly, the outlet port 0215 may be exposed to one or more chambers that reduce in volume as the inner rotor 0305 and the outer rotor 0310 rotate and expel fluid into the outlet port channel, and may be connected to an outlet port channel 0220 that may act as a manifold to combine and smooth the flow from the multiple chambers. Fluid passes through the housing 0400 via an inlet port 0405 and an outlet port 0410.

[0084] A further non-limiting embodiment is shown in FIG. 7. This embodiment will be discussed in relation to operation as an expander. In the compressor configuration, port 0710 is used as an intake with port 0715 acting as an exhaust and shaft 0725 acting as a mechanical input for the inner rotor, however, the inventors envision that the device may operate in an expander configuration where fluid is supplied to port 0715 acting as an intake at a higher pressure than the pressure at port 0710 acting as an exhaust port. As the fluid travels into the chamber formed between the rotors and expands, it rotates the inner rotor and shaft 0725, providing mechanical work. Many other port configurations are possible and contemplated by the inventors.

[0085] FIG. 5 shows the inner rotor 0505 and outer rotor end plate 0510 of the embodiment of FIG. 7. For reference, the end plate 0510 is shown in FIG. 1. The inner rotor 0505 is in contact with the outer rotor end plate 0510. The outer rotor end plate 0510 has an array of rotation chamber ports 0515 that allow fluids to enter and exit the device. Radial ports that allow fluid flow to the inlets and outlets could also be used, but the inventors believe that they would be more difficult to seal than the axial port exemplary embodiment shown. This is because radial ports require the outer radial surface of the outer rotor to seal against the inner radial surface of the housing or other surface, and these surfaces must form coaxial cylinders that remain coaxial and maintain a tight gap as the rotor expands and deforms due to thermal expansion and / or centrifugal forces.

[0086] In the embodiment shown in Figures 5, 13, and 14, the purpose of the device is to provide radially movable, sliding apex seals in the sealing zones at TDC and BDC without additional leakage paths around the edges of these seals. The configuration and method are proposed as shown in Figure 9. In step 1, the inner rotor / outer rotor positive displacement device is provided with an apex seal that slides radially on the inner rotor. The term "apex seal" generally refers to a seal at a protrusion tip, but here refers to a seal that seals against the protrusion tips of the other rotor, whether the seal is on the protrusion tip or in the trough between the protrusions of the rotor to which the seal is attached. In the exemplary embodiment shown in Figures 5, 13, and 14, the apex seal includes a seal at the tip of the inner rotor lobe to seal against the tips of the fins of the outer rotor at bottom dead center (BDC) and a seal in the trough between the inner rotor lobes to seal against the tips of the fins of the outer rotor at top dead center (TDC). This use of separate radially movable seals at TDC and BDC allows each to have its own unique position. The radially movable seals may be radially movable at a first temperature and may be configured to be radially fixed at a second temperature or to provide a smaller gap clearance around the sides of the seal. In the exemplary method shown in FIG. 9, in step 2, the radially movable seals are allowed to advance radially outward to their respective positions where they contact the tips of the protrusions of the outer rotor ("top-out positions") at a temperature lower than the expected operating temperature, and the seals may advance to the radially outward positions under the influence of centrifugal forces, for example, when the device operates at low temperatures. In step 3, heat is applied to the system at operating temperature, causing the seals to expand in all directions to take up the gaps along the sides of the grooves. The seals are made of a material with a higher coefficient of thermal expansion compared to the material of the inner rotor with the seal grooves. The run-in must be gentle enough to prevent the seals from wearing down and catching on the mating surfaces.In one embodiment, the seal may be preloaded radially inward, such as with a spring configured to return the seal to an inward position when at rest, and centrifugal force pushes the seal outward toward its top-out position. This allows for break-in by gradually increasing the speed while cold until the seal stops moving outward at its top-out position, and then applying heat to expand it to close the gap in the seal groove. The seal may be a flexible, elastic or rigid material. Closing the gap may allow the seal to lock into place, or may allow the seal to become tighter in the groove, reducing leakage around the seal in the groove, or both.

[0087] Figure 6 is an isometric cross-sectional view of the apparatus shown in Figure 7, showing the drive shaft 0605 of the inner rotor 0610 eccentric to the bearing seat 0615 of the outer rotor. Note that although the housing is not shown in Figures 5 or 6, one skilled in the art would understand that components having ports with sliding seals, such as the port plate 0705 shown in Figure 7 having an intake port 0710 and an exhaust port 0715 when operating as a pump or compressor, would typically be located proximate to the rotating port 0620 located at the axial end of the outer rotor end plate 0625. 7, the stationary ports having intake ports 0710 and exhaust ports 0715 located on the seal plate 0720 allow fluid to enter and exit the volume formed between the protrusions of the inner rotor 0610 and the outer rotor 0630 as said rotors rotate, while sealing the rotating ports 0620 located on the end plate 0625 at or near top dead center where the fluid volume between the rotors is at a minimum and at or near bottom dead center where the volume between the fluid volumes is at a maximum. In operation, fluid passes through the axial ports 0620 of the outer rotor which rotates relative to the stationary ports (e.g., including intake ports 0710 and exhaust ports 0715 located on the stationary port plate 0705) as shown in FIGS.

[0088] Figure 6 also shows the parallel axes of the inner rotor shaft 0605 and the outer rotor shaft and bearing supports 0615. In a non-limiting exemplary embodiment, both rotors 0610 and 0630 are supported for rotation at both axial ends for high rigidity. Bearings are not shown for clarity, but the implementation can be understood from Figure 6 by one skilled in the art, where the shaft 0605 of the inner rotor 0610 extends through the bearing seat 0615 for the outer rotor. This bearing arrangement can be achieved in other ways as contemplated by the inventors.

[0089] For example, in the embodiment shown in FIG. 8, the machine 0800 includes an inner rotor 0805 and an outer rotor 0810, which form a chamber between the inner rotor and the outer rotor. In the embodiment shown in FIG. 1, the inner rotor 0105 and the outer rotor 0100 are each cantilevered with two bearings at one axial end of each rotor, but in the configuration shown in FIG. 8, the inner rotor 0805 and the outer rotor 0810 are each supported by bearings at both axial ends of the respective rotors, allowing for high stiffness and a compact form factor. In the non-limiting embodiment shown in FIG. 8, the bearing seat of the inner rotor bearing 0820 is within the inner diameter of the outer rotor bearing 0815. Alternatively, the inner rotor bearing 0820 can be axially offset, allowing for a larger inner rotor bearing 0820 and / or a smaller outer rotor bearing 0815.

[0090] --------------------Inner trochoid derivation--------------------

[0091] The design aspects of the disclosed invention can be determined by the following methods:

[0092] Select the preferred ratio of the speeds of the two rotors of the device, which depends on the number of inner rotor protrusions, or, if the inner rotor protrusions are lobed, the number of lobes on the inner rotor, N lobesThe number of outer rotor protrusions, or if the outer rotor protrusions are fins, the number of fins on the outer rotor N fins is the ratio to:

[0093]

number

[0094] This ratio also determines the relative speed at which each rotor rotates relative to the housing. In some instances, the outer rotor protrusion number is one greater than the inner rotor protrusion number.

[0095] A preferred offset of the axes of the two rotors of the machine is also selected; this is the distance between the axes and shall be called the Axis Offset.

[0096] We also select a preferred size for the device, defined as the inner radius of the outer rotor measured at the inner tips of the fins of the outer rotor, which shall be referred to as the Radius. In embodiments where the tip of the outer rotor is rounded rather than a point, the Radius is measured from the axis of rotation of the outer rotor to the center point of the circle that defines the rounded tip of the outer rotor.

[0097] Construct the sealing geometry of the inner rotor which can be driven by the parametric equations:

number

[0098] X and Y from 0 to 2π*N fins Note that when plotted with t varying from , the parametric equations produce a hypotrochoid with a size determined by the radius and a shape determined by the axial offsets and ratios. Such a hypotrochoid has a length of N lobes For example, a nine-lobe hypotrochoid defined by these equations is shown in Figure 10.

[0099] The outer and inner portions of this hypotrochoid correspond to the surface of the inner rotor, which form a seal zone against which the tips of the outer rotor fins seal. In an embodiment, the seal zone includes portions of the tips of the inner rotor lobes and portions of the troughs between the inner rotor lobes. The seal zone may include an explicit moving seal, as shown above with respect to FIG. 5, or may be an integral part of the inner rotor. In either case, the seal zone, the tips, the trough, or both, may be configured to be shaped, e.g., machined, by the innermost tip with the innermost tip of the outer rotor, e.g., by the material selection of the seal zone compared to the innermost tip, the shape of the innermost tip, or both. Other ways in which the tips may shape the surface include pushing a formable material (plastic deformation), grinding an abradable material, or pushing and thus moving a moving element, e.g., a moving seal. It is preferred that the outer rotor tip is not infinitely sharp, but rather that the outer rotor tip is shaped by the innermost tip, e.g., by the material selection of the seal zone compared to the innermost tip, the shape of the innermost tip, or both. Other ways in which the tips may shape the surface include pushing a formable material (plastic deformation), grinding an abradable material, or pushing and thus moving a moving element, e.g., a moving seal. OuterRotorTip In an embodiment having a radius of R, all seal surfaces of the inner rotor are spaced apart from the hypotrochoid defined by the motion of the center point of a circle that defines the rounded outer rotor tip relative to the inner rotor. OuterRotorTipThe hypotrochoidal plot is shown in FIG. 11 overlaid on a non-limiting embodiment of the apparatus disclosed herein having a straight fin 1105 and an infinitely sharp outer rotor fin tip 1110. It may be noted that the tip of the outer rotor fin 1105 traces a hypotrochoidal path 1115 relative to the inner rotor 1120 because as the outer rotor 1125 rotates about its axis relative to the housing, the inner rotor 1120 also rotates at a different speed proportional to the relative number of lobes, resulting in a hypotrochoidal path 1115 relative to the inner rotor 1120. It may further be noted that the geometry of the inner rotor 1120 is defined by the hypotrochoidal path 1115 with certain exceptions such as the leading and trailing edges of the inner rotor lobes 1130 that allow the fin tip 1110 to trace the hypotrochoidal path 1115 without interference with the inner rotor lobes 1130 of the remainder of the fin.

[0100] The shape shown in FIG. 11 is further developed in FIG. 12. In this non-limiting embodiment, the inner rotor is considered to be supplied with an external torque source, for example from a shaft driven by an electric motor. Since it is considered by the inventors to be disadvantageous for the inner rotor to drive the outer rotor only at the tip of the outer rotor (since very little surface is at the fin tip of the outer rotor that contacts the inner rotor), an additional driving surface 1205 is designed on the inner rotor lobe, which drives the outer rotor via an additional driven surface 1210 on the outer rotor fin. In the embodiment shown in FIG. 12, this driven surface is an arc that approximately intersects with the outer rotor fin tip. In some embodiments, it may intersect exactly with the outer rotor fin tip; however, in this embodiment, the arc is moved radially outward to form a transition zone at the outer rotor fin tip to aid in the transition between the outer rotor fin driven surface driven by the inner rotor lobe and the outer rotor fin tip that forms the seal zone between the inner rotor lobes. The angle of the arc at the fin tips should be selected for the proper rake angle to shape the seal zone of the inner rotor, a concept that is explained in more detail below.

[0101] The inventors note that this outer rotor surface need not be an arc; however, it is believed that an arc provides a suitable combination of rolling and sliding contact between the inner and outer rotors. Regardless of the selected shape of the outer rotor fin trailing / driven surface 1210, this surface may define the inner rotor lobe driving surface 1205. If an arc, the inner rotor lobe driving surface may be defined in the following manner.

[0102] Select the location of the center of the circle containing the arc that defines the driven surface of the outer rotor fin and the radius of the circle (Fin Backing Radius, 1215).

[0103] Determine the distance from the center point of this circle to the axis of the outer rotor (Fin Backing Circle Radial Distance, 1220).

[0104] 4. Determine the angle formed between a radial line passing through the outer rotor axis and the center point of this circle, and a radial line passing through the outer rotor axis and the fin tip (Fin Backing Circle Offset Angle, 1225).

[0105] The following hypotrochoid equation is used to define the curve of the inner rotor:

[0106]

number

[0107]

number

[0108] Note that these are the same equations used to define the seal surface, except with different point radii based on the fin backing circle radial distance.

[0109] The hypotrochoid defined by the equation above is rotated (about the axis of the inner rotor in the direction of rotation of the fin backing circle offset angle, 1225) by the fin backing circle offset angle, 1225, divided by the ratio.

[0110] Offset the hypotrochoid by the fin backing circle radial distance, 1220. This results in a conjugate surface for the inner rotor drive surface 1205 defined by the arc on the outer rotor. Note that this method can also be used to define the inner rotor seal surface at TDC and BDC if rounded fin tips are used on the outer rotor.

[0111] If the OR fin driven surface is not a circular arc, the following method can be used to define the mating surface of the inner rotor.

[0112] An appropriate number of points on the outer rotor fin driven surface is selected.

[0113] For each of these points, determine the distance to the axis of the outer rotor (Point Radial Distance).

[0114] Determine the angle formed between the outer rotor axis and a radial line passing through that point and a radial line passing through the outer rotor axis and the fin tip (Point Offset Angle).

[0115] We use the following hypotrochoidal equation to define the curve:

[0116]

number

[0117]

number

[0118] Rotate the hypotrochoid defined by the equation above (around the axis of the inner rotor, in the direction of rotation of the point offset angle) by the point offset angle divided by the ratio.

[0119] 1. Select the extreme points of all points in the set of hypotrochoids formed by each of the points selected in 1 (i.e., the deepest points of the inner rotor lobe) and use them to define a curve representing the driving surface of the inner rotor lobe. A spline or similar interpolation between the sets of extreme points may be preferred.

[0120] 13 illustrates an embodiment using a circular arc 1305 on the driven surface of an outer rotor fin 1310 and shows the resulting offset inner trochoid 1330 formed on the inner rotor driving surface. The opposite surface to that defined by the circular arc 1305 on the same outer rotor fin, used for reverse operations such as pump applications, may be defined as a circular arc as shown in this non-limiting exemplary embodiment so as not to interfere with the inner rotor. Their designs are discussed further below.

[0121] 14 shows an isometric cross-section of the inner rotor 1405 and outer rotor 1410, illustrating the hypotrochoidal path 1440 of the outer rotor nose tip 1450 relative to the inner rotor 1405. Arrow 1445 indicates the direction of rotation of the outer rotor 1410 and inner rotor 1405 for purposes of the above discussion.

[0122] -------------------Contact Ratio-------------------

[0123] Another feature of the described geometry is the ability to design a contact ratio of the inner rotor 1405 relative to the outer rotor 1410 that is greater than or equal to 1 and that always rotationally positions both rotors relative to each other and provides the torque required to rotate the outer rotor 1410, as seen in FIG. 14. Contact ratio is defined in this document as the average number of points of contact between the driving, leading surfaces 1415 of the inner rotor 1405 and the driven, trailing surfaces 1420 of the outer rotor 1410 as they rotate. In the disclosed embodiment device, a ratio of 1 or greater ensures that there is always at least one point of contact between the inner and outer rotors. It is noted that this assumes that once the driving surface stops contacting the driven surface, it does not regain contact with the driven surface until the next rotation. Similarly, the contact ratio can be used to refer to the non-driven timing contact of the inner rotor trailing surface 1425 and the outer rotor leading surface 1430 that prevents the driven rotor from rotating faster than it is being driven; for example, during deceleration of the inner rotor 1405. In this document, leading is used to describe features that face primarily toward the direction of rotation, and trailing is used to describe features that face primarily away from the direction of rotation. A contact ratio of 1 or greater for both the driving and timing surfaces is considered by the inventors to provide operation of the device without the need for external timing gears, in combination with other features of the device, such as the hydraulically balanced driving rotor described herein. The primary driving contact 1435 is between two surfaces with similar curvatures that the inventors believe are ideal for low wear due to reduced contact pressure. In an embodiment, these surfaces include a convex surface on the outer rotor driven surface and a concave surface on the inner rotor driving surface. This combination of concave and convex surfaces with similar curvatures is also ideally suited to mold a fluid film between these surfaces to reduce rotor-to-rotor contact during operation.Further reduction in wear is believed by the inventors to result from a constant progression of contact between the driving and driven surfaces along both of these surfaces. This results in only momentary contact at each point along the surface of the rotor once per revolution of the rotor. This provides only a small amount of heating and wear at each point, providing the remainder of that rotor's revolution to allow cooling of that point. Alternatively, the outer rotor can be the driving rotor, but this would result in higher contact pressures since the inner rotor is not hydraulically rotationally balanced.

[0124] For clarity, the embodiment of the device as shown in FIG. 13 has slide surfaces 1320, 1325, 1330 and 1335 and seal surfaces 1340 and 1345. In the non-limiting embodiment shown in FIG. 13, the seal surfaces may have radially movable seals 1370 and 1380. Thus, the outer rotor 1355 has a first slide surface 1320 at the leading side of the direction of rotation indicated by the arrow 1350 and a second slide surface 1325 at the trailing side of the direction of rotation. The inner rotor 1360 has a first slide surface 1330 at the leading side of the direction of rotation and a second slide surface 1335 at the trailing side of the direction of rotation. The inner rotor 1360 also has a seal surface 1340 and a seal surface 1345 at the outermost of the lobes. The interaction of the slide surfaces provides angular timing between the inner rotor and the outer rotor to achieve mating motion and is not intended to provide a seal. For example, the seal zone defined by the area of ​​contact or near contact where the radially moving seal or seals occur is not intended to provide rotational timing, but rather provides a near zero clearance seal with the advantages of low leakage and low drag torque. Contact between the inner rotor leading surface and the outer rotor trailing surface preferably begins after the seal zone at BDC and ends before the seal zone at TDC. Timing contact between the inner rotor trailing surface and the outer rotor leading surface preferably begins after the seal zone at TDC and ends before the seal zone at BDC.

[0125] Portions of the outward projections of the inner rotor contact the leading or trailing surfaces of the outer rotor described above to provide rotational positioning of the outer rotor relative to the inner rotor. These surfaces of the inner rotor may also include a formable material, where the seal zone includes the formable material. In one example, the entire radially outer envelope of the inner rotor includes a formable material as shown in FIG. 17, whereby the contact pressure of the outer rotor tip 1735 is high enough on the seal zone at TDC and BDC to form the formable material at TDC and BDC, but low enough to slide with minimal wear on the drive surface 1770 of the inner rotor.

[0126] The slide surfaces are preferably designed with a mesh ratio of 1 or greater in the direction of rotation indicated by arrow 1350. During forward rotation of the inner rotor resulting in the displacement of fluid from the outlet, resistance to rotation of the outer rotor is expected from viscous friction with the fluid. This resists the forward rotation of the outer rotor 1355 and creates a contact force between the driving surface 1325 and the driven surface 1330. Upon deceleration, the rotational momentum of the outer rotor 1355 may advance it relative to the inner rotor 1360 such that the slide surfaces 1320 and 1335 may come into contact.

[0127] The sliding contact surfaces are preferably characterized by having similar curvatures to the corresponding surfaces of the inner and outer rotors to provide low contact forces. For example, sliding surface 1325 and sliding contact surface 1335 have similar morphology. The sliding contact surfaces are further preferably characterized by having simultaneous sliding and rolling interactions as seen by either rotor during operation, which provides two advantages. The first advantage is reduced sliding speed for a given rotational speed of the rotor. The second advantage is that in the case of a pair of rotors, at least one of which has an arced sliding surface, a certain amount of rolling contact ensures that no point on the sliding surface is in contact at the same location for more than an instant. In other words, since the contact point between the inner and outer rotor sliding surfaces is constantly moving, there is only one instant of localized heating from the sliding at any point on the sliding contact surface per rotor revolution, while the remainder of the rotor revolution serves to allow the surface to cool. Because wear on these types of surfaces is greatly affected by the amount of heat generated, the sliding surfaces of this device are well suited to providing low wear, even with a thin fluid film or no lubrication.

[0128] The contact surfaces that make contact during such deceleration events are also preferably characterized by a contact ratio of 1 or greater, but may have shorter contact surfaces and larger differences in arc radii, as shown in surfaces 1705 and 1710 in FIG. 17, where 1705 indicates a rounded surface on the inner rotor 1715 and 1710 indicates a curved surface on the outer rotor 1720. This has less of a wear benefit, but the deceleration contact surfaces primarily serve to prevent the outer rotor from advancing relative to the inner rotor, which may occur during such deceleration events. This deceleration can be limited by the speed control of the drive motor, so that the deceleration contact surfaces are always only slightly engaged or not engaged at all during normal use. In many applications, it is more important for the device to accelerate quickly than for it to decelerate quickly, so this is considered a useful operating parameter.

[0129] It should be noted that in this arrangement a certain amount of backlash can be tolerated, and a small amount of backlash may be preferred for low friction operation.

[0130] -----------------Radial Shaping (Round OR Fins)-----------------

[0131] Returning to FIG. 13, one important feature of this device is that the pointed tip 1365 (which could be a sharp edge to cut into the inner rotor, a small radius, preferably with an abrasive texture to wear into the inner rotor, or a range of other geometries with various effects) only seals at or near top dead center (TDC) and at or near bottom dead center (BDC), and does not need to contact and / or seal between these poles. The seals at TDC and BDC separate the positive displacement device into high pressure and low pressure sections.

[0132] The outer rotor protrusions may be configured to receive substantially equal and opposite torques from their surface areas exposed to the high and low pressure portions at TDC and BDC. By using sharp or small radius tips 1365 on the outer rotor lobes 1310 as seals at TDC and BDC, the surface areas of the outer rotor 1355 exposed to the high pressure fluid are equal or nearly equal at TDC and BDC. This creates a situation where there is no or no significant torque acting on the outer rotor 1355 as a result of the fluid pressure. This effect is referred to in this disclosure as rotationally hydraulically balanced, and the motion of the outer rotor 1355 without significant net torque from the fluid pressure is referred to in this disclosure as freewheeling. This freewheeling reduces the torque that must be transferred from the inner (drive) rotor 1360 to the outer (driven) rotor 1355, for example, by the meshing of the lobes of each of the two rotors. This results in very low surface contact forces between the inner rotor 1360 and the outer rotor 1355 for low wear, low friction, and high efficiency.

[0133] The sharp tip 1365 may be designed to cut or wear a path through the sealing surfaces 1340 and 1345 of the inner rotor 1360, removing material from the seal area of ​​the inner rotor 1360 during certain operating conditions. This may allow the device to be initially constructed to low tolerances, but achieve a very precise seal geometry in operation where the outer rotor tip 1365 carves a unique path through the sealing surfaces 1340 and 1345 of the inner rotor 1355. Design and operation of the disclosed invention in such a manner is expected to result in a close fit between the sharp edge 1365 and the inner rotor 1360 during operation. This close and narrow gap acts to reduce the leakage rate of the fluid medium through the gap while simultaneously providing low friction.

[0134] Radially sliding seals such as lobe tip seal 1370 located on inner rotor lobe 1375 and recessed seal 1380 located in inner rotor lobe root 1385 are also shown in the non-limiting exemplary embodiment shown in FIG. 13. These seals may be spring loaded inward or outward and / or their position is determined by centrifugal force (used colloquially) to tend to contact the outer rotor during operation and form an effective seal. As shown by the shape of seals 1370 and 1380 in FIG. 13, the seals may have a mechanical stop feature that prevents them from moving outward beyond a desired point. In the embodiment shown in FIG. 13, such a mechanical stop feature is provided by the fitted round base of seals 1385 and 1390. When the seal is flipped inward, shaping of the seal surface can occur gradually and at higher speeds during the break-in phase as centrifugal force pushes the seal radially outward against the spring force until the seal is fully shaped into the desired shape by the outer rotor fin tips 1365.

[0135] This configuration has the advantage of allowing a moving seal to be inserted into the inner rotor body, which may be made of a material with less strength than the inner rotor body. This allows high pressure operation with excellent sealing immediately after assembly, and maintains sealing effectiveness after long term operation even when the seal wears from sliding contact. Another important advantage of this construction is that the outer rotor tips contact different inner rotor seals at TDC and BDC. This prevents gaps from forming in either the TDC or BDC zones if the inner rotor and outer rotor shafts are not precisely aligned in manufacture and assembly. The seals are all configured with a "top out" feature that allows, for example, fluid pressure, preload springs, centrifugal force in many high speed applications, or other mechanisms to move the seal outward until it hits a hard-stop. This includes the seal from centrifugal ejection and prevents wear during operation beyond the point when the molding effect of the outer rotor fin tips no longer contacts with sufficient force to cause further wear.

[0136] The non-limiting embodiment shown in Figures 13 and 14 has a lobe to fin ratio of 9 / 10 (as defined above), which has the advantage of allowing a drive rotor-driven rotor mesh ratio of greater than 1. Other lobe to fin ratios are possible, preferably with a difference of 1 between the number of inner rotor lobes and outer rotor fins. It is also possible to have a difference greater than 1. This impacts the shape of the hypotrochoid, as taught previously.

[0137] 15 shows a simplified semi-schematic embodiment where the inner rotor has seven outward lobes and the outer rotor has eight inward fins. The direction of rotation of the inner rotor 3005 and outer rotor 3010 is indicated by arrow 1510. This non-limiting exemplary embodiment has a lobe-to-fin driving-driven mesh ratio of 1 or more, where there is always one or more seal contact points between the inner and outer rotors at TDC and always one or more seal contact points between the inner and outer rotors at BDC.

[0138] 16 shows an embodiment in which the inner rotor 5020 has 11 outward lobes and the outer rotor 5010 has 12 inward fins. This non-limiting exemplary embodiment has a lobe-to-fin driving-driven mesh ratio of 1 or more, and there is always one or more sealing contact points between the inner and outer rotors at TDC and always one or more sealing contact points between the inner and outer rotors at BDC. The direction of rotation of the inner rotor 5020 and outer rotor 5010 is indicated by arrow 1615.

[0139] ------------------Radial Forming (Pointed Outer Rotor Fin)---------

[0140] 17, as the inner rotor 1715 and outer rotor 1720 rotate in unison, two regions of sealing contact occur. At TDC, which occurs at or near the point where the chamber reaches its minimum volume, as shown approximately by chamber 1725 in FIG. 17, the innermost portion 1730 of the radial surface of the inner rotor 1715 contacts the fin tips 1735 of the outer rotor, resulting in shaping by machining, grinding and / or wear between the fin tips 1735 of the outer rotor 1720 and the machinable or formable or wearable portion 1740 of the inner rotor 1715. An example of this shaping contact at TDC is shown within the dotted circle 1745.

[0141] Similarly, at BDC, as the chamber reaches or approaches its maximum volume, as shown approximately by chamber 1750 in Figure 17, the tops of the outermost portions 1755 of the radial surfaces of the inner rotor 1715 lobes contact the fin tips 1735 of the outer rotor 1720, causing machining and polishing of the outer surface of the inner rotor. An example of this forming contact at BDC is shown within the dotted circle 1760.

[0142] Figure 18 provides a more detailed view of the fin tip and inner rotor interaction at a point near BDC. For clarity, the same reference numbers used in Figure 17 are provided in Figure 18 where applicable.

[0143] To aid in the following discussion, the rake angle referred to below refers to the angle between the outer rotor fin tip forming edge and a reference plane perpendicular to the plane tangent to the formed surface of the inner rotor at the point where the forming edge intersects the formed surface in the direction of relative motion of the two components. The rake angle is measured from a reference plane perpendicular to the tangential plane. FIG. 19 shows a non-limiting embodiment with a rake angle of about -12 degrees. The dotted line 1925 is the reference plane and the dotted line 1930 is the plane representing the leading surface of the forming edge. As shown in FIG. 19, a rake angle where the leading surface of the forming edge 1930 is forward of the reference plane 1925 in the direction of rotation 1920 is referred to as a negative rake angle and a rake angle where the reference plane 1925 is forward of the leading surface of the forming edge 1930 in the direction of rotation 1920 is referred to as a positive rake angle.

[0144] As conceptually shown in FIG. 19, the inventors have determined through experimentation that when using an outer rotor fin 1905 with a sharp tip, labeled 2005 as shown in FIG. 20, a formable surface such as PTFE is formed, although the inventors believe that many other formable materials, including those that are machinable or polishable, may be used with varying degrees of effectiveness. Polishable materials generally do not require sharp tips. An example formable surface 1910 is shown in FIG. 19 and labeled 2010 as shown in FIG. 20 (an enlarged view of the fin 1905 shown in FIG. 19, shown in the context of the interaction between the fin tip 2005 and the formable inner rotor 2020 surface 2010), where the rake angle is important in ensuring proper machining / forming characteristics. For example, in FIG. 19, the inventors have found for steel as the outer rotor fin material for the formed edge 1915 and PTFE as the formable surface material.

number

[0145] The maximum rake angle depends on many factors, including the material combination and the tip hardness, sharpness and stiffness of the forming edge. Furthermore, the effective rake angle between the forming edge 1915 of the outer rotor 2015 and the formable surface of the inner rotor changes continuously as the inner rotor 2020 and the outer rotor 2015 rotate in unison and the forming edge 1915 moves over the formable surface of the inner rotor 2020. As a result, in many configurations such as those shown in this disclosure, achieving the optimum forming angle at TDC requires sacrificing the optimum rake angle at BDC or vice versa. This is because the contact angle between the fin tip and the inner rotor seal surface changes over the course of the contact, making it difficult to maintain the optimum rake angle at the same tip angle.

[0146] To address this, the inventors propose a non-limiting exemplary embodiment shown in Figures 21-24, where every other fin on the outer rotor has a shaping edge designed to operate at an optimized angle to shape the inner rotor at some contact points, and the remaining tips have shaping edges designed to operate at an optimized angle to shape the inner rotor at other contact points, such that as the inner and outer rotors rotate in unison, the inner rotor experiences alternating tip shapes with corresponding alternating rake angles.

[0147] Thus, for all or most of the shaped area, half of the fins (or in other embodiments, one or more) have a shaping / rake angle optimized for shaping the inner rotor seal surface at TDC, and the remaining half of the fins (or in other embodiments, one or more) have a shaping / rake angle optimized for shaping the inner rotor seal surface at BDC. This is in contrast to the case where all of the fins have the same rake angle, where optimal shaping occurs only at TDC or BDC, or is not optimized for either. This non-limiting configuration is shown in FIG. 21, where a first outer rotor 2110 fin 2115 has a shaping rake angle of the shaping feature 2125 at the tip of the adjacent second outer rotor 2110 fin 2130,

number

number

number

[0148] An important feature of the alternate fin tip angle embodiment is that the contoured tips of both fin shapes 2120 and 2124 trace a common hypotrochoidal path relative to the inner rotor. This allows both tips to participate in a seal with consistent contact or gap clearance. FIG. 24 shows an overlaid image of both fins (i.e., fin 2115 and fin 2130 in FIG. 21) showing their tip positions in the same location relative to the sliding / timing surface of the outer rotor fin. Ensuring that the tips of both (or all) fin shapes are in the same location relative to the sliding surface of the outer rotor fin ensures that a consistent seal gap and timing is provided for all fin tips.

[0149] For clarity, where applicable, the same reference numbers are used in FIG. 24 as were used in FIG.

[0150] The inventors understand and anticipate that more than one tip shape may be used, for example, in a multiple lobe set, where each lobe in each lobe set has a common shape. It is believed by the inventors that it is preferred, but not required, for the number of outer rotor fins to be divisible by the number of different tip shapes, i.e., the number of multiple sets of different tip shapes corresponding to the multiple lobe sets, in order to maintain rotational balance and consistent shaping during break-in.

[0151] -------------AXIAL shaping----------------------

[0152] In one embodiment, it is an objective of the device to limit leakage of pumping medium along the axial surface of the inner rotor 2505 from the high pressure side of the device to the low pressure side of the device, which may result in, among other things, higher efficiency of the device. The inner rotor may have first and second axially facing surfaces. The first axially facing surface of the inner rotor may face the axially facing surface of the outer rotor to comprise a first surface pair. The second axially facing surface of the inner rotor may face the housing or another axially facing surface of the outer rotor to comprise a second surface pair. In the example shown in Figures 25-27, the outer rotor 2510 includes an outer rotor end plate 2515, the outer rotor having a first axially facing surface in contact with the first axially facing surface of the inner rotor, and the end plate 2515 having an axially facing surface facing the second axially facing surface of the inner rotor. To achieve a low friction, close tolerance seal between the outboard axial end of the inner rotor 2505 and the inboard axial end of the outer rotor 2510, the outer rotor end plate 2515 may employ methods similar to those already described for creating a radially close contact seal. That is, the inclusion of sharp, abrasive, or otherwise capable features capable of removing material from other parts of the device may be used. Examples of such features are the multiple molded features shown in Figures 25-27. An abradable coating may also be used on one or both of the mating surfaces such that one surface wears away quickly or both surfaces may wear away from each other. Any of the axial surface pairs described may have such features or coatings, and the features may be on either surface of the pair and the coatings may be on either or both surfaces of the pair.

[0153] In the non-limiting embodiment shown in FIG. 25, the first molded feature 2520 is a small protrusion on the outer rotor end plate 2515 that protrudes from the plate surface 2525 by a distance of about 0.01 mm. The exact size of the protrusion may be larger or smaller, resulting in different effects, but it may be advantageous to select a 0.01 mm protrusion as shown in FIG. 26 to enhance the sealing of the device in the axial direction, not only at the top of the molded feature, but also at one or both of the leading and trailing edges. Furthermore, the shape of the molded feature may be designed to occupy a small percentage of the total sealing surface area, such that the surface area of ​​the top of the molded surface feature has a minimal surface area that may rub against the molded edge and machinable / polishable / or otherwise formable material and cause localized heating. The location of the outer rotor plate 2515 and the orientation of the first molded feature 2520 in a non-limiting exemplary device may be shown in FIG. 25. In this orientation, it can be seen that the first mold feature 2520 is positioned to remove material from the rotating inner rotor 2505 during certain operating conditions, such as during a break-in phase. The removal of material on the inner rotor 2505 by the first mold feature 2520 can be controlled during a break-in period during a test procedure or after initial start-up. Additionally, the inventors consider the break-in period to occur after the device has been repaired or as a process to improve sealing if the sealing surfaces of the device have been damaged or worn during operation. Methods for controlling such removal are taught by the authors below.

[0154] To improve device performance, the molded features for any of the surface pairs described may be generally angled in a counterclockwise outward helical direction for a clockwise rotating device (as the view is toward the surface of the end plate 2515 having the molded features 2520), as shown in FIG. 25 as a non-limiting example. This contributes to the removal of molded debris toward the outside of the rotor where it can be exhausted from the exhaust port. FIG. 26 shows the end plate 2515 separated from the rest of the device. In FIG. 26, the direction of rotation of the end plate 2515 is indicated by arrow 2620.

[0155] Figure 27 shows second mold features 2715 located on the outer rotor 2710, which are configured in a similar manner as the first mold feature 2520 of Figure 25. In the non-limiting embodiment shown in Figure 27, these second cutting features are oriented to remove material from the inner rotor 2705 when the device is operating under certain conditions, such as during a break-in phase.

[0156] Depending on the embodiment, there may be additional axial surface pairs between the inner or outer rotor and the housing, such as the port plate of the housing. In FIG. 25, a third mold feature 2530 is shown located on the axially outer surface of the outer rotor 2510, which is configured in a similar manner as the first mold feature 2520. In the non-limiting embodiment shown in FIG. 25, these third mold features are oriented to remove material from the seal plate 2535 when the device is operating under certain conditions, such as during a break-in period.

[0157] Any such interaction with the port plate may occur with other parts of the housing. In the embodiments described below, such interaction may aid in sealing to the housing if the rotor does not have end plates. If the rotor has end plates, interaction with the port plate may aid in sealing to the port plate, but there is less need to seal to other parts of the housing than with a port plate where an end plate is present, because the end plate does not need to have holes in this case and any chambers between the end plate and the non-port plate housing portion may be isolated from the working fluid region of the device.

[0158] The term "end plate" may be used in this document to refer to a separately constructed plate assembled to a portion of a rotor, such as end plate 2515 in FIG. 26, or a plate that is integral with the remainder of the rotor and has an axially facing surface that faces the rotor and other rotor protrusions, for example a surface that includes molded features 2715 as shown in FIG. 27.

[0159] The inner rotor, outer rotor and housing collectively form a set of components arranged for relative motion in a plane perpendicular to the axis (of either one of the rotors). There may be axially facing surfaces forming an interface between any pair of these components. In some embodiments, the inner rotor contacts the outer rotor at two such interfaces. Both interfaces may include axially facing surfaces of integrally or separately formed end plates of the outer rotor, for example as shown in Figures 25-27. In other embodiments, for example, the outer rotor may contact the end plate of the inner rotor such that the outer rotor is axially within the end plate of the inner rotor (a "spool" arrangement), or the inner and outer rotors may each have a respective end plate that is contacted by the other rotor. In further embodiments discussed below, there may be fewer than two such interfaces between the rotors.

[0160] In the embodiment shown in Figures 25-27, the inner rotor is axially between the outer rotor surfaces, so there are two surface pairs between the axial surfaces of the inner and outer rotors, and only the outer rotor has a surface pair with the housing. In other embodiments, for example as shown in the non-limiting simplified embodiment of the machine 5200 shown in Figure 52, the inner rotor 5205 may have a single surface pair with the outer rotor 5210, shown by dashed line 5230, and each of the inner rotor 5205 and outer rotor 5210 may have a surface pair with the inwardly facing axial surface of the housing 5270. This pair between the rotors 5205, 5310 and the housing 5230 is shown by dashed line 5240. For reference, the lower part of the housing 5260 supports bearings 5245 and 5250, which support the input shaft 5265 of the inner rotor 5205, and bearings 5225 and 5255 support the outer rotor 5210. Also for reference, 5215 is the intake port and 5220 is the exhaust port.

[0161] In an alternative simplified non-limiting embodiment shown in FIG. 56, the inner rotor is axially between two housing surfaces, so there are two surface pairs between the inner rotor axial surface and the housing surface, and two surface pairs between the outer rotor axial surface and the axial surface of the housing. As shown in FIG. 56, for ease of assembly, the housing may include two parts, a first housing part 5660 and a second housing part 5620. The inner rotor 5605 may have a first surface pair between the aforementioned outward axial surface of the inner rotor and the axially inward surface of the first housing part 5660, and a second surface pair between the outward axial surface of the inner rotor and the inward axial surface of the second housing part 5620. Also, the outward axial surface of the outer rotor may have a first surface pair between the aforementioned outward axial surface of the outer rotor and the inward axial surface of the first housing part 5660, and a second surface pair between the aforementioned outward axial surface of the outer rotor and the inward axial surface of the second housing part 5620. If the rotors contact the housing without end plates, then both rotors may contact the housing. In the claims, the recitation of a surface of one rotor contacting a surface of the housing does not exclude the other rotor also contacting the same surface of the housing.

[0162] 56, a first portion of the housing 5660 supports a bearing 5670 that supports a first end of the outer rotor 5650 and a bearing 5635 that supports a first end of the inner rotor shaft 5615. A second housing portion 5620 supports a bearing 5665 that supports a second end of the outer rotor 5610 and a bearing 5665 that supports a second end of the input shaft 5215. Also, 5625 is an intake port and 5630 is an exhaust port. Other embodiments may have different arrangements of bearings and ports.

[0163] To further illustrate the above embodiment, a cross-sectional view of an embodiment similar to that shown in FIG. 56 is shown in FIG. 57. In the embodiment shown in FIG. 57, the intake port 5625 and exhaust port 5630 are in different locations as shown in FIG. 58, but serve the same purpose as shown in FIG. 56. From FIG. 57, it is observed that none of the port plates interact with the axially facing surfaces of the inner rotor 5605 and the outer rotor 5610. Rather, the second housing portion 5620 has a first axially facing surface 5810, as shown in FIG. 58, which forms a surface pair with the axially facing surfaces on the inner rotor 5605 and the outer rotor 5610. In such an embodiment, molded features on any one or combination of the inner rotor 5605, outer rotor 5610, or second housing portion 5620 may be configured to mold opposing surfaces to form a close-contact seal that may have low leakage and / or low friction. A sealing barrier 5825 divides the second housing portion 5620 into an intake manifold 5835 and an exhaust manifold 5830. The sealing barrier 5825 prevents leakage from the exhaust manifold 5830 to the intake manifold 5835 across the axial surface of the inner rotor 5605 between the axial surface of the inner rotor 5605 and the second housing portion 5620. In the non-limiting example shown in FIG. 56, the second housing portion 5620 is designed for a pump configuration used with incompressible fluids. However, it will be clear to one skilled in the art how to adjust the geometry to allow for internal compression and / or expansion and / or include a compressor configuration, for example, as shown in other embodiments.

[0164] An alternative view of the second housing portion 5620 is shown in Figures 58 and 59. For clarity, where applicable, reference numbers from Figure 56 are reused in Figures 57, 58 and 59. For added clarity, the preferred direction of rotation is indicated by arrow 5705 in Figure 57.

[0165] The inventors note that the mold features may take on configurations different than those shown in Figures 25-27. For example, in the non-limiting embodiment shown in Figure 28, the first mold features 2805 are small protrusions on the inner axially facing sealing surface 2815, and these first mold features 2805 protrude from the axially facing sealing surface 2815 of the outer rotor 2810. As previously taught, protrusions of various sizes can be used, but as shown in Figure 28, it may be advantageous to minimize the size to enhance axial device sealing in close clearances of the surfaces surrounding the mold features. The location of the axially facing sealing surface 2815 of the outer rotor 2810 and the orientation of the first mold features 2805 in the non-limiting example device are shown in Figure 29. It can be seen that in this orientation, the first mold feature 2915 on the outer rotor 2910 is positioned to remove material from the rotating inner rotor 2905 when the device is operating under certain conditions. The removal of material on the inner rotor 2905 by the first mold feature 2915 can be controlled during wear during testing procedures or in periods following device assembly or repair. Methods for controlling such removal are taught by the authors below.

[0166] Visible in Figure 32 are second mold features 3210 located on the outer rotor end plate 3215 that are configured in a similar manner as the first mold feature 2805 from Figure 28. In the non-limiting embodiment shown in Figure 32, these second mold features 3210 are oriented to remove material from the inner rotor 3205 during certain operating conditions, such as break-in conditions.

[0167] In Figures 30 and 31, third mold features 3005 located on the outer rotor 3010 are visible that are configured in a similar manner as the first mold feature 2805 from Figure 28. In the non-limiting embodiment shown in Figure 30, these third mold features 3005 are oriented to remove material from the seal plate 2920 of Figure 29 when the apparatus is operating under certain conditions. For clarity, reference numbers from Figure 30 are reused in Figure 31 where applicable.

[0168] The raised surfaces, including molded features such as the first molded feature 2805, the second molded feature 3210, and the third molded feature 3005, have a dual role of molding the corresponding surface as well as forming a seal between said raised surface and its corresponding molded surface. Thus, the raised surfaces can be designed with a predetermined balance between molding and sealing. As shown in the non-limiting embodiment shown in FIG. 33, the raised surface 3305 is designed to extend from the end 3315 of the outer rotor 3310 protrusion toward the central axis of the outer rotor 3310 to have a molded edge while simultaneously providing an uninterrupted seal chamber between the inner rotor and the outer rotor. Although circumferentially thick raised surfaces such as 3305 shown in FIG. 33 provide a long, primarily tangential seal passage between the chambers that provides an improved seal than thinner raised surfaces, these thick raised surfaces 3305 also indent or displace the molded surface in contact as the raised surface passes over and presses the molded surface. Softer materials being molded may be prone to overheating during molding due to the large sliding surface area and require a thinner raised surface, depending on the operating conditions and the amount of molded surface material to be removed. The thickness of molded feature 3405, shown as the distance between arrows 3415 and 3420, is approximately ten thousandths of an inch, as shown in the non-limiting embodiment shown in FIG. 34. Both circumferentially wide and thin molded features have been shown to be effective, and the ideal width for a particular device may be determined through experimentation.

[0169] In the non-limiting embodiment shown in FIG. 35, the thickness of the molded feature 3505, shown as the distance between the arrows 3515 and 3520, is approximately 35 thousandths of an inch, which the inventors believe to be sufficient to provide a suitable balance between sealing and molding for a particular application when the raised molded surface is made from steel and the molded surface of the inner rotor is PTFE. In the non-limiting embodiment shown in FIG. 35, the raised surfaces radiate largely radially from the ends of the outer rotor fins toward the center of the inner rotor shaft. These radially extending raised surfaces 3505 are connected to each other via circular portions 3530 of the raised surfaces.

[0170] Each of these molded features serves to remove material from the corresponding machinable / abradable / otherwise formable surface of the other part in such a way that the molded part and the part to be molded are in close contact when the molding process is completed. In the case of a mating abradable coating, the coating serves to abrad both parts to bring them into close contact when the abrading process is completed. In this way, the gap between the two, and accordingly, the leakage of working fluid from the high pressure side of the device to the low pressure side of the device between the two parts, is limited, improving the efficiency of the device. As an added benefit, the small gap ensures that there is little or no rubbing, dragging, or other significant amount of contact between the two parts, reducing the torque required to rotate the device and improving the efficiency of the device.

[0171] All of the above-described embodiments that use molding between axially oriented surfaces can be implemented without such molding, for example by using high-precision machining to form the surfaces into the desired shape in the initial structure. This is particularly desirable for embodiments that are intended to withstand higher pressures, such as high-pressure pumps. When high pressures are anticipated, more strength may be required and moldable materials, which tend to have lower strength, are less desirable.

[0172] -----------------------RUN-IN-METHOD-----------------------

[0173] 55 illustrates an exemplary break-in method. In step 550, a positive displacement machine is provided that includes an inner rotor, an outer rotor, and a housing. The inner rotor has a radially outward protrusion, the inner rotor is fixed for rotation relative to the housing about a first axis, the outer rotor has a radially inward protrusion configured to mesh with the radially outward protrusion of the inner rotor, the outer rotor is fixed for rotation relative to the housing about a second axis parallel to and offset from the first axis, and the inner rotor has a first axially facing surface and a second axially facing surface. In step 552, the positive displacement machine is operated under conditions where one or both of the axially facing surfaces of the inner rotor interfere with a corresponding axially facing surface of the outer rotor or the housing, causing molding of the inner rotor.

[0174] In step 554, the positive displacement device can then operate without interference between any of the sealing surfaces. The inner rotor may be configured to cause interference when the positive displacement device operates as constructed, and the subsequent operation without interference may be due to shaping of the inner rotor when the positive displacement device operates as constructed. Alternatively, the condition causing interference may be a condition in which the inner rotor has a first temperature, and the inner rotor has a second temperature different from the first temperature during subsequent operation without interference. The temperature change may be an increase or decrease in temperature depending on the temperature changes of other components and the coefficients of expansion of the different components.

[0175] An exemplary break-in procedure may include rotating the device up to a desired operating speed, then introducing heat (e.g., in some embodiments, allowing the device to heat up on its own) to raise the device temperature to the temperature range expected during operation. By selecting an inner rotor formable (e.g., machinable / polished) surface material (e.g., PTFE, as a non-limiting example, when used as a coating or overmold around a metal core) with an appropriate thickness, it is possible to use the centrifugal force and / or thermal expansion of this layer to grow the formable surface radially and axially outward until it contacts the molded edge or when the abradable surface contacts and creates a tight clearance seal. With a sufficiently thick PTFE surface with sufficient thermal expansion at the operating temperature, it is also possible to build the inner rotor with a low precision manufacturing method such as injection molding to create a part with sufficient clearance that is easy to assemble. After assembly, the device is preferably rotated to a speed slightly higher than the intended operating speed, and then the device is preferably heated (e.g., by heating the working fluid entering the device) to a temperature slightly higher than the intended operating temperature (to ensure slightly more material is removed or slightly more molding of material than is necessary during break-in) so that a small seal gap is achieved without further molding or contact of the seal surfaces during operation at the intended speed and temperature range.

[0176] -----------------Ice Removal------------------------

[0177] When an apparatus such as the exemplary embodiment 3600 shown in Figure 36 is used in a humid gas application, such as, but not limited to, a hydrogen recirculation blower for a fuel cell, the compressed hydrogen mixture will likely contain water vapor that can condense and freeze in cold atmospheric conditions when the fuel cell is shut down. If a water-laden hydrogen recirculation blower is exposed to freezing temperatures while not in operation, and if it is not properly designed to address this ice formation, as described below, there is a risk that components will freeze together and render the machine inoperable until the ice melts.

[0178] The machine 3600 may include a purge valve 3605 (described below) to depressurize the chamber 3610. The purge valve 3605 may be configured to depressurize the chamber by opening a path from the chamber 3610 to the inlet side of the machine 3600 when the machine 3600 is not operating, so that the port plate 3615, biased by the spring 3620 away from the outer rotor 3625, is retracted with a relatively large gap between the corresponding axial surfaces of the outer rotor 3625 and the port plate 3615 to prevent ice from forming between these surfaces. However, such a purge valve is likely not necessary because once the device is no longer operating, the close contact seal between the port plate 3615 and the outer rotor 3625 leaks at a rate sufficient to allow all pressure chambers to equalize and also to allow the port plate 3615 to be pulled away from the outer rotor axial surface 3630 as a result of the force of the spring 3620.

[0179] Even if ice does form between the seal surfaces, the molded features located on the inwardly facing axial surface and the outwardly facing axial end of the outer rotor can quickly scrape or grind the ice away from the seal surfaces.

[0180] Another approach to ability to sub-zero temperature starting is to use the device with a drain port at the bottom of the device, tilted from horizontal, such as, but not limited to, between 1° and 45°, so that condensed water droplets that fall or flow to the bottom of the outer rotor when the device is not rotating tend to flow downward to the drain port. At angles within this range, condensed water tends to fall to the bottom of each chamber and the bottom of the outer rotor.

[0181] Another approach to cold start capability that can be used alone or in combination with the above is shown in FIG. 54. In step 540, a positive displacement machine having an inner rotor and an outer rotor is provided. In step 541, the machine is operated at an operating machine temperature (e.g., the temperature of the surface of the outer rotor facing the fluid flow) greater than 0° C. In step 542, the operation of the machine is stopped. In step 543, the temperature of the machine is monitored, for example, using an internal temperature sensor that alerts the CPU when the temperature inside the machine reaches a temperature threshold. The temperature threshold may be, for example, slightly above 0° C. In the non-limiting embodiment of FIG. 54, the threshold is set between 1° C. and 5° C. In decision step 544, if the temperature threshold is reached, the method proceeds to step 545, otherwise monitoring continues. In step 545, the machine is instructed by the CPU to spin at a speed sufficient to centrifuge condensed water droplets onto the outermost inward-facing surface of the outer rotor chamber, where some or all of this water can be forced out of the drain port. Any water droplets remaining in the rotor chambers after this short spin cycle will tend to fall to the bottom of the outer rotor in the outermost volume of the chamber. The outer rotor may be shaped to provide a clearance between the root of the inward projection of the outer rotor fins and the tip of the outward projection of the inner rotor, and the clearance may be selected to accommodate ice accumulated during shutdown and start-up. Thus, the outermost portion of the chambers of this device may be configured to have an adequate recirculation volume to maintain clearance with the inner rotor at TDC and the remainder of a full rotation. As a result, water that freezes in the outermost volume of either chamber will not prevent the rotors from meshing during start-up. As the device warms up to operating temperature, the ice melts and is drained out of the drain port.

[0182] To allow the device to start up at sub-freezing temperatures, the device is preferably mounted such that the exhaust port is located at the bottom of the device. Also, the bottom surface of the exhaust port is preferably tilted downwards, generally away from the outer rotor, so that water entering the exhaust port flows away from the outer rotor as a result of gravity. This can be done by tilting the entire device or by tapering the outermost inward-facing surface of the outer rotor chamber. As shown in the non-limiting example of FIG. 53, the device 5300 can be tilted to attach the positive displacement device to an external surface or structure, for example, using a mounting mechanism 5305, so that the first axis has a non-vertical, non-horizontal orientation in which the positive displacement device's exhaust port 5320 is located at substantially the bottom portion of the positive displacement device's effective volume. For example, the orientation of the inner rotor 5325 axis, the axis shown by the dashed line 5310, can be between 1 degree and 45 degrees from vertical. The angle of the inner rotor axis shown in FIG. 53 is approximately 45 degrees from vertical. For reference, the inlet port is labeled 5315.

[0183] The device can be spun for a short time just before the components within the device reach 0°C during cooling so that the condensed water is centrifuged to the outermost volume of the outer rotor chamber and then flows out of the drain port. By using a combination of centrifugal force and gravity to expel the water droplets from the outer rotor to the drain port, the inventors believe that this can be done at a slow enough rotation speed that the condensed water droplets can be removed from the device without creating a high enough flow rate to draw in more water droplets from elsewhere in the system. For example, if the device has a rated operating speed of several thousand rpm, it may be possible to drain the majority of the condensed water during a device water removal cycle of less than one minute at only a few hundred rpm. To further enhance this effect, a high thermal conductivity mesh or screen 3705 made of a high thermal conductivity material such as aluminum can be placed upstream of the device 3700 and connected to a frame / housing that is exposed to ambient temperature and therefore acts as a heat sink 3710 to cool the mesh / screen as shown in FIG. 37. At sub-freezing external temperatures, as a result of the heat sink, this screen will reach below 0°C before the inner or outer rotor, e.g., the fluid-facing surface of the outer rotor. The inner and outer rotors may have a larger thermal mass than the screen, are not directly exposed to the environment, and should cool more slowly than the screen. If the inner or outer rotors are cooling during shutdown in sub-freezing environmental conditions, for example when the outer rotor is just above freezing, the screen is already below freezing. When the operator or CPU 3715 commands the rotors to spin at a slower speed, at this point any water that has condensed on the rotors will drain off their surface, and any humidity in the incoming stream will tend to condense and freeze on the screen 3705, reducing the likelihood of additional water droplets entering the device.

[0184] --------Inner rotor structure------------------

[0185] 38 shows an exemplary embodiment of the device featuring a clamshell construction of moldable material around an inner rotor 3805. In this embodiment, the inner rotor 3805 is constructed by fastening, such as with bolts or adhesive, a plastic material 3815 onto an inner portion 3820 of the inner rotor 3805, the inner portion 3820 being preferably constructed from a material that is stiffer and / or stronger, and preferably less costly, than the material of the outer portion 3820.

[0186] 17 shows an exemplary embodiment of an overmolded construction, in which an inner rotor 1715 is constructed by overmolding a plastic material 1765 onto an inner portion 1770 of the inner rotor 1715, the inner portion 1770 being constructed from a material that is stiffer and / or stronger, and preferably less costly, than the overmolded material.

[0187] Returning to Figure 38, the outer rotor forming edges 3825 located at the ends of the inward fins on the outer rotor 3810 are designed to form the preferably softer inner rotor outer material 3830 such that the forming edges 3825 trace an endotrochoidal path on the profile of the inner rotor 3805, as previously described in this disclosure. The direction of rotation of the inner rotor 3805 and outer rotor 3810 during operation is indicated by arrow 3835.

[0188] ----------------Port plate structure and adjustment mechanism-------- Materials may be selected to avoid unwanted thermal expansion and wear effects. In the non-limiting example shown in FIG. 25, the port plate 2535 is constructed as a single piece. It may be advantageous for the port plate 2535 to be constructed from a relatively soft and / or easily moldable material such as PTFE or PEEK, since the soft material is more easily removed or molded by the molded features 2530 on the outer rotor 2510 as taught by the above authors. However, constructing such a port plate from a single piece of plastic may be expensive due to high material costs. Furthermore, such materials have the disadvantage that their thermal expansion coefficient exceeds that of many metals, including aluminum. As a result, the gap between the port plate and the sealing surface of the outer rotor may change depending on the temperature of the port plate and the housing due to the different thermal expansion coefficients. Thus, a single piece port plate may have further disadvantages if the housing 2540 is constructed from a material that has a different thermal expansion coefficient compared to that of the material of the port plate. Such disadvantages arise when, under high temperature conditions, the port plate 2535 expands axially more or less than the housing 2540, resulting in contact with the molded features 2530 of the outer rotor 2510 or a large gap between the sealing surfaces of both. A small amount of molding of the port plate seal by the outer rotor is desirable for a near zero gap seal. This small amount can be controlled by mechanical stops that set the amount of axial movement of the axially movable, mechanically energized port plate and / or thermal expansion of the port plate or port plate moldable surfaces. For example, too much thermal expansion resulting in too much material removal is undesirable as it increases the time required for break-in.One way to ensure minimal self-molding is to use thin sections of machinable / polishable / otherwise moldable material, such as but not limited to PTFE, on the port plate sealing surface and limit the amount of thermal expansion of the port plate surface, and a more rigid port plate body made from a material, such as but not limited to aluminum. In a non-limiting example shown in Figures 39, 40, 41, and 42, the port plate 3905 is comprised of a moldable piece 3910 (shown in Figure 39) and a support piece 3915. The moldable piece 3910 can be a soft material, such as but not limited to PEEK or PTFE. This material can be selected for its machinability. For reference, Figures 40 and 41 show the same non-limiting embodiment in which the port plate 3905 position is actuated via pressurized fluid. Figure 42 shows a different non-limiting embodiment in which the port plate 4200 position is adjusted via a screw.

[0189] The support piece 3915 may be constructed of a material such as, but not limited to, aluminum whose stiffness may exceed the stiffness of the wear piece 3910 material, thus providing resistance to deformation of the port plate 3905. Additionally, the material of the support piece 3915 may be selected to have a coefficient of thermal expansion close to that of the material of the housing 3920. As an added benefit, the material of the support piece 3915 may have a greater thermal conductivity than the material of the wear piece 3910, allowing heat to be transferred more quickly from the port plate 3905 via conduction with contacting components of the device, such as the housing 3920.

[0190] Figures 40 and 41 provide alternative views of the embodiment shown in Figure 39. For clarity, the same reference numbers used in Figure 39 are provided in Figures 40 and 41, where applicable.

[0191] As shown in the non-limiting embodiment of FIG. 42, the port plate 4200 includes two portions, a support portion 4205 and a seal portion 4210. Although the support portion 4205 and the seal portion 4210 are shown bolted together, other fastening methods are also contemplated by the inventors, including but not limited to the use of adhesives, rivets, and thermal joints. In FIG. 42, an inlet port 4215 and an outlet port 4220 provide a passage through the port plate 4200, and a platform 4225 contacts an axle screw that adjusts the axial position of the port plate 4200. The axle screw mechanism is described below. Port 4230 is an optional port for a sensor in this non-limiting exemplary embodiment and can be used for diagnostics.

[0192] In a non-limiting embodiment shown in FIG. 43, the port plate 4315 may have a two-piece construction with a backing plate 4320 made from a metal such as aluminum, covered by a sealing surface plate 4325 made from a plastic material such as, but not limited to, PEEK or PTFE. A means such as, but not limited to, an axial screw 4330 may be used to axially move the port plate 4315, forcing it to press against the axial end of the outer rotor 4310, which may have molded features on a surface 4335 facing the port plate 4315, which may be similar to, for example, molded feature 3105 shown in FIG. 31 or molded feature 2530 shown in FIG. 25. These features machine, grind, mill, mold, or otherwise remove material from the port plate to create a light contact or small gap between the outer rotor and the port plate.

[0193] 43, the port plate 4315 includes a backing plate 4320 and a sealing surface plate 4325. The sealing surface plate 4325 is molded with molded features located on the outer axial surface 4335 of the outer rotor 4310. In a non-limiting embodiment, the backing plate 4320 is made from a material having a similar coefficient of thermal expansion as the housing 4340. Thus, as the temperature of the housing changes, the distance between the sealing surface of the sealing surface plate 4325 and the corresponding molded features located on the axially outward facing surface 4335 of the outer rotor 4310 remains approximately the same.

[0194] In a non-limiting exemplary embodiment, the backing plate 4320 and the housing 4340 are made from aluminum and the moldable member 4325 is made from PTFE.

[0195] In a non-limiting exemplary embodiment shown in FIG. 44, the port plate 4415 is axially movable and is biased via a spring 4420 to move axially away from the outer rotor 4410. Pressurized fluid in the channel 4425 flows into a chamber 4430 between the port plate 4415 and a housing 4435, causing the port plate 4415 to act as a piston and move axially towards the outer rotor 4410. In a non-limiting exemplary embodiment, the pressurized fluid provided to the chamber 4430 is provided by an external source, such as an external air compressor or external compressed air reservoir, or by pressure generated by the output of the device. This allows for control of the axial position and therefore shaping of the port plate 4415.

[0196] In a non-limiting embodiment, the fluid chamber 4430 is in communication with a high pressure area of ​​the machine, such as the exhaust port, such that when the exhaust port is at a higher pressure compared to the inlet port and therefore additional sealing is required, the chamber 4430 experiences a pressure greater than the average pressure on the opposite side of the port plate 4415, overcoming the force provided by the spring 4420 and moving the port plate toward the outer rotor 4410.

[0197] 45, the port plate 4515 is positioned within a housing 4575 with a first pair of seals 4570 and 4590 and a second pair of seals 4545 and 4595 such that the cross-sectional area exposed to the working pressure on the side of the port plate furthest from the outer rotor is greater than the cross-sectional area exposed to the working pressure on the side of the port plate 4515 that seals against the outward axial end of the outer rotor 4530. Port 4580 may be used to maintain the area between seals 4570 and 4545 at a pressure lower than the working pressure of the working fluid, and port 4585 may be used to maintain the area between seals 4590 and 4595 at a pressure lower than the working pressure of the working fluid.

[0198] 45, the ports 4535 are positioned to communicate with fluid passing through the ports in the outer rotor and the passages in the port plate 4515. In operation, the port plate experiences a net force in the direction indicated by arrow 4550 towards the outer rotor 4530.

[0199] In other non-limiting embodiments, the springs can be oriented to push the port plate toward the outer rotor, without the need for a backing pressure chamber or axial screw.

[0200] Returning to FIG. 44 , a “top out” feature 4440 may be used to prevent the pressurized fluid in the chamber 4430 acting on the port plate 4415, or the spring in an embodiment if a spring is used instead of a pressure chamber, from pushing the port plate 4415 further toward the outer rotor 4410 beyond a predetermined axial position, even after the surface of the sealing plate 4445 has been cut or worn or shaped by a molded feature of the outer rotor. This additional movement is prevented by contact between the port plate 4415 and the top out feature 4440, which may be a feature of the housing 4435 or another component of the device. Additionally, feature 4450 prevents the spring 4435 from pushing the port plate 4415 away from the outer rotor 4410 beyond a predetermined axial position. This additional movement is prevented by contact between the top out feature 4450, which may be a feature of the housing 4435 or another component of the device, and the port plate 4415.

[0201] It may be desirable for the port plate 4415 and outer rotor 4410 to separate when the device is not operating to prevent or reduce freezing of the port plate 4415 to the outer rotor 4410 which would require excessive torque to separate them upon start-up. In embodiments where the chamber 4430 is pressurized with an external pressure supply, disconnecting the external pressure supply when the device is not operating achieves this separation as the pressure force is not against the spring. In embodiments where the chamber 4430 is pressurized using the device's discharge pressure, separation occurs as the chamber 4430 is depressurized when the device is not operating and the pressure force is not against the spring. In this embodiment, it is desirable to keep this separation small enough so that, even with this gap, the device seals sufficiently to build up enough pressure in the chamber 4430 against the spring when the device begins to operate so that the port plate 4415 molds the outer rotor 4410 or reaches its top-out position. A reasonable separation range is 0.002-0.004 inches, which the inventors believe will allow sufficient pressure build-up, although higher gaps may also work in various configurations (eg, for larger devices).

[0202] Figure 4 shows the suction and exhaust sides of the machine. In a non-limiting exemplary embodiment, the port plate position may be adjusted via three adjustment screws 0415 that thread into the housing and exert a force on the port plate axially toward the outer rotor to define the port plate position. A spring that pushes the port plate away from the outer rotor provides an opposing force that ensures the port plate is in full contact with the three adjustment screws.

[0203] -----------------Compression removal flow path---------------------

[0204] When the leading or trailing edge of the outer rotor projection contacts the corresponding surface of the inner rotor projection, the curved surface of each projection may form an additional sealed chamber near top dead center, referred to herein as a secondary chamber. To prevent these secondary chambers from being sealed and thus resulting in unnecessary compression or decompression of the fluid within that space, flow passages may be arranged to connect these secondary chambers to a port, such as an intake port. The flow passages may be located, for example, in the inward axial end plate of the outer rotor, in the contact surface of the inward projection of the outer rotor, or in the outward projection of the inner rotor. In the example shown in FIG. 46, the non-sealing portion 4615 provides a flow passage along the driven surface of the outer rotor fin 4620 to prevent sealing of the non-useful secondary chamber 4625 formed between where the tip 4630 of the outer rotor projection 4620 contacts the inner rotor surface 4635 and where the tip of the inner rotor lobe 4640 contacts the outer rotor fin surface 4645, thereby avoiding unnecessary compression of the fluid within this volume, and thus avoiding or reducing this energy loss.

[0205] The non-sealed portion 4615 may also take on additional configurations as illustrated by the non-sealed portion 2720 of the embodiment shown in Figures 27 and 28. In these non-limiting exemplary embodiments, the outer rotor has a pocket on the leading surface of the outer rotor projection to provide a flow path to allow fluid to exit the secondary chamber and avoid undesirable compression as described above.

[0206] For clarity, the same reference numbers are used for the non-sealed parts in both Figures 27 and 28.

[0207] In another non-limiting embodiment shown in Figure 47, the flow passage 4715 is located on an axially facing seal surface 4720 of the outer rotor 4710 which allows flow from the secondary chamber 4725, thereby preventing unwanted compression in the secondary chamber. In Figure 47, the direction of rotation of the inner rotor 4735 and the outer rotor 4710 is indicated by arrow 4730.

[0208] ----------------Debris Removal-------------------

[0209] As discussed above, in embodiments, pairs of axially facing surfaces are configured such that one surface of the pair molds the other. Fluid flow channels may be provided to supply fluid to any one or more interfaces involving these surface pairs for debris removal. In embodiments that do not mold the surfaces, fluid flow channels may be provided for other purposes such as cooling. In a non-limiting exemplary embodiment shown in FIG. 48, an inlet port 4820 supplies compressed gas that is routed within the machine 4800 to the internal machined / polished / formed surfaces between the port plate 4815 and the outer rotor 4810 to remove molded debris from the seal surfaces to prevent heat buildup and to prevent particles generated from the molding process from accumulating on the molding or formed surfaces and interfering with the sliding contact between said surfaces. The path taken by the supplied compressed gas is indicated by arrows 4825. Compressed gas from a compressor 4830, shown diagrammatically as a box, enters an inner axial channel 4835 at which point a first portion of the compressed gas passes through a flow passage 4895 in the outer rotor 4810, allowing the compressed gas to carry debris generated between the inner rotor 4805 and the outer rotor 4810, and the compressed air carrying the debris exits through a port 4705, shown blocked by a plug 4855 in FIG. 48 but which is unplugged during debris removal.

[0210] A second portion of the compressed gas travels via an alternative path indicated by arrow 6120. Said second portion of compressed gas travels from the axial channel 4835 of the outer rotor 4700 to an area 4855 that allows compressed gas to flow from the channel 4835 located on the inner axis of the shaft of the outer rotor 4700 to the axial channel 4650 of the inner rotor 4805. After traveling through the channel 4650, the compressed gas exits the channel through a port 4880 to an area 4710 that accumulates debris generated by the inner and outer rotors. The compressed gas carrying the debris then travels through a gap 4860 between the housing 4885 and the outer rotor 7400, exits through the port 4705, and leaves the machine 4600 through the port 4705 when the plug 4855 is removed.

[0211] 49, compressed gas is provided from an external compressor 4925, e.g., an air compressor, (schematically shown as a box), to a gas inlet 4930, via a path indicated by arrow 6500. The compressed gas then travels from the air inlet 4930 to a flow path 4935 within the inner rotor shaft 4906 of the inner rotor 4905. At this point, a first portion of the gas exits the flow path 4935 via a first inner rotor shaft port 6640, this path indicated by arrow 6575, while a second portion continues to travel within the flow path 4935, this path indicated by arrow 6570, until it reaches the end of the flow path 4935, at a second inner rotor shaft port 4940.

[0212] Said first portion of gas further splits into a third portion of gas and a fourth portion of gas after passing through port 6640. The third portion, indicated by arrow 6615, passes through debris pick-up area 6700 and exits through port 6605. The fourth portion, indicated by arrow 6620, passes through debris accumulating area 6705 and continues through channels in the outer rotor 4910, the path indicated by arrows 6625 and 6630, before traveling through channels in port plate 6710 that lead to the exterior of the apparatus (such as exhaust port 4225 visible in FIG. 42), thereby exhausting the debris from the machine, the path indicated by arrow 6635.

[0213] A second portion of the compressed gas then travels through said second inner rotor shaft port 4940, a path indicated by arrow 4945. As the compressed gas exits port 4940 and passes through seal 4950, which is a region that generates debris (between the axial seal surface of the outer rotor 4910 and the axial seal surface of the inner rotor 4905, this portion of the path indicated by arrow 6610), and region 4955, which is also a region that accumulates debris, the bulk compressed gas carries the debris out of the machine through port 4965 located on housing 6545, this portion of the path indicated by arrow 6515. Compressed gas may also be provided from compressor 4925 to inlet port 5115 (shown in FIG. 51 ) of machine 7000, which causes the gas to travel through a chamber formed between inner rotor 4905 and outer rotor 4910 of machine 7000 and to be exhausted through exhaust port 5120, thereby carrying debris out of the chamber and out of machine 7000.

[0214] 50 and 51, an external gas compressor is connected to the inlet port 5115 of the machine 5000, which allows compressed gas to enter a chamber formed between the protrusions of the outer rotor 5010 and the inner rotor 5005. As the input shaft 5015 rotates, the compressed gas moves through the machine 5000, thereby carrying debris out of the machine 5000 through the exhaust port 5120.

[0215] As shown by the non-limiting example in FIG. 50, the plug 5025 may be used to seal the housing 5030 of the machine 5000 once the molding / break-in process is complete. In other embodiments, fluids other than compressed gas may be used to flush debris and / or remove heat, such as, but not limited to, water, coolant, or alcohol. For clarity, reference numbers used in either FIG. 50 or FIG. 51 are used again in the opposite figure, where applicable. The fluid supply channels supplying fluid to the different interfaces may be connected together or separately, and when separate, may use the same or different fluids. The fluid used may be the same as the working fluid of the positive displacement device or different. The fluid supply channels may include fluid channels that supply the interface via a direction away from the interface, such as via a flow passage shown through the shaft of the inner rotor, as shown in FIGS. 48-50. Fluid flow channels may be provided within the interface, such as, for example, a depression in the surface that forms an interface that does not form a seal and therefore allows debris to move through the interface from where the seal occurs to the outlet.

[0216] In the claims, the word "comprise" is used in its inclusive sense and does not exclude the presence of other elements. The indefinite articles "a" and "an" preceding a claim feature do not exclude the presence of a plurality of features. Each individual feature described herein can be used in one or more embodiments and is not to be construed as essential to all embodiments defined by the claims by virtue of its mere description herein.

Claims

1. a housing; an inner rotor having outward protrusions with the number of inner rotor protrusions, the inner rotor being fixed to rotate relative to the housing about a first axis; an outer rotor having inward protrusions with the number of outer rotor protrusions, the outer rotor being fixed to rotate relative to the housing about a second axis parallel to and offset from the first axis; and having, the outward protrusions of the inner rotor and the inward protrusions of the outer rotor engage, and the outer rotor and the inner rotor are configured to rotate at a relative ratio of rotational speeds defined by a ratio of the number of inner rotor protrusions to the number of outer rotor protrusions; the inward protrusions of the outer rotor have a most inner tip that defines an epitrochoid path relative to the inner rotor during rotation of each of the inner rotor and the outer rotor; the inner rotor has a tip seal zone at the tip of the outward protrusions and a trough seal zone in a trough between the outward protrusions, and the tip seal zone and the trough seal zone are arranged to seal against the most inner tip of the protrusions of the outer rotor and form respective engagements with the tip seal zone and the trough seal zone along the epitrochoid path when the most inner tip traces while moving along the epitrochoid path during rotation of each of the inner rotor and the outer rotor, during at least a part of each of the respective engagements with the trough seal zone, the most inner tip that traces while moving is the same as the rotation of the inner rotor, during the whole of each of the respective engagements of the most inner tip of the outer rotor with the tip seal zone, the most inner tip that traces while moving is opposite to the rotation of the inner rotor, a positive displacement device.

2. The number of the outer rotor protrusions is one greater than the number of the inner rotor protrusions. The positive displacement device according to claim 1.

3. The tip seal zone occurs in a bottom dead center zone including the bottom dead center (BDC) of the positive displacement device, the trough seal zone occurs in a top dead center zone including the top dead center (TDC) of the positive displacement device, and the seal zones of the BDC and the TDC separate the positive displacement device into a high pressure region and a low pressure region. The positive displacement device according to claim 1.

4. The radially inward protrusions of the outer rotor, in combination with the seal of the radially inward protrusions of the outer rotor with respect to the inner rotor, are configured to generate substantially equal and opposite torques on the outer rotor as a result of their similar surface areas exposed to high pressure fluid at the TDC and the BDC. The positive displacement device according to claim 3.

5. Two consecutive regions between two consecutive radially inward protrusions of the radially inward protrusions of the outer rotor and the radially outward protrusions of the inner rotor are each shaped such that a seal is maintained between the inner rotor and the outer rotor in a chamber beyond the TDC to provide internal expansion of the compressed fluid passing through the TDC. The positive displacement device according to claim 3.

6. Two consecutive radially outward protrusions of the radially outward protrusions of the inner rotor are each shaped such that a seal is maintained between the inner rotor and the outer rotor in a chamber beyond the BDC to provide internal compression of the fluid passing through the BDC. The positive displacement device according to claim 3.

7. Further comprising a screen arranged to contact the fluid flow to the positive displacement device, the screen being arranged to cool more rapidly than the surface of the outer rotor facing the fluid when the positive displacement device is shut down after use. The positive displacement device according to claim 1.

8. The screen is thermally connected to a heat sink exposed to the ambient temperature. The positive displacement device according to claim 7.

9. The tip seal zone or the trough seal zone or both are configured at the innermost tip of the outer rotor such that the tip seal zone or the trough seal zone or both are shaped by the innermost tip of the outer rotor. The positive displacement device according to claim 1.

10. The first inward protrusion of the inward protrusions of the outer rotor has a first tip shape different from the second tip shape of the second inward protrusion of the inward protrusions of the outer rotor, the first tip shape having a higher rake angle with the tip of the outward protrusion of the inner rotor in the relative motion direction at bottom dead center (BDC), and the second tip shape having a higher rake angle in the trough between the outward protrusions of the inner rotor in the relative motion direction at top dead center (TDC). The positive displacement device according to claim 9.

11. The first inward protrusion has a first tip at the innermost tip of the outer rotor, the second inward protrusion has a second tip at the innermost tip of the outer rotor, and the first tip and the second tip are arranged such that the first tip and the second tip trace a common internal trochoid path with respect to the inner rotor. The positive displacement device according to claim 10.

12. The inward protrusions of the outer rotor include a plurality of sets of protrusions, the protrusions of each set having a common geometric shape, and the number of outer rotor protrusions being a multiple of the plurality of sets. The positive displacement device according to claim 10.

13. The innermost tip of the inward protrusions of the outer rotor is made of a material harder than the inner rotor in the tip seal zone and the trough seal zone, and the innermost tip of the inward protrusions of the outer rotor is configured to form the tip seal zone and the trough seal zone during operation of the positive displacement device. The positive displacement device according to claim 9.

14. The innermost tip of the inward protrusions of the outer rotor has a pointed tip, and each innermost tip is gradually tapered by the inward protrusions in a direction away from the inner portion of the outer rotor ending at the pointed tip. The positive displacement device according to claim 9.

15. The innermost tip of the outer rotor is composed of a rounded surface. The positive displacement device according to claim 9.

16. The tip seal zone or the trough seal zone or both include a radially movable seal. The positive displacement device according to claim 1.

17. The radially movable seal is configured to be radially movable at a first temperature and radially fixed at a second temperature. The positive displacement device according to claim 16.

18. The radially movable seal is configured to be radially movable within a groove and radially movable at a first temperature, and to fit tightly into the groove at a second temperature. The positive displacement device according to claim 16.

19. The inward protrusion of the outer rotor has a leading portion and a subsequent portion configured to contact the outward protrusion of the inner rotor between the tip seal zone and the trough seal zone. The positive displacement device according to claim 1.

20. Further having a flow path arranged to prevent the formation of a sealed secondary chamber between the outward protrusion of the inner rotor and the inward protrusion of the outer rotor at or near top dead center (TDC). The positive displacement device according to claim 19.

21. The subsequent portion of the inward protrusion of the outer rotor provides relative rotational positioning of the outer rotor and the inner rotor and provides a meshing ratio between the rotors in one or more rotational directions. The positive displacement device according to claim 19.

22. The leading portion of the inward protrusion of the outer rotor provides relative rotational positioning of the outer rotor and the inner rotor and provides a meshing ratio between the rotors in one or more rotational directions. The positive displacement device according to claim 19.

23. Of the troughs between the outward protrusions, the trough has a shape such that a sealed chamber is maintained beyond the TDC to provide internal expansion of the fluid passing through the top dead center (TDC). The positive displacement device according to claim 1.

24. The inner rotor protrusion of the outward protrusions has a shape such that a sealed chamber is maintained beyond the bottom dead center (BDC) to provide internal compression of the fluid passing through the bottom dead center (BDC). The positive displacement device according to claim 1.

25. The tip seal zone, the trough seal zone, or both, include a formable material, and a portion of the outward protrusion of the inner rotor that provides rotational positioning relative to the outer rotor includes the formable material. The positive displacement device according to claim 1.

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