Abstract:
A fluid transfer device, comprising an outer housing having an inward facing cylindrical or partially cylindrical surface, an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis, a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor; an inner rotor secured for rotation about an axis within the carrier, the inner rotor having an outward facing surface plane perpendicular to the inner rotor axis and outward projections arranged around the outward facing surface configured to operate as a pump.

Description:
BACKGROUND 
       [0001]    A new pump design uses the same sealing geometry as in U.S. Pat. No. 7,111,606 with some important modifications. 
       SUMMARY 
       [0002]    In various embodiments, there may be included any one or more of the following features: 
         [0003]    A pump, comprising: 
         [0004]    an outer housing having an inward facing cylindrical or partially cylindrical surface. 
         [0005]    an outer rotor with radial inward projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0006]    an inner rotor secured for rotation about an axis within the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface; 
         [0007]    the inward projections projecting inward and the outward projections projecting outward to mesh with each other and define variable volume chambers between the inward projections and the outward projections as the inner rotor rotates within the carrier; 
         [0008]    the outward projections each having a leading edge and trailing edge; 
         [0009]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers; and 
         [0010]    the outer rotor is connected to be driven with a rotary shaft input, and convex trailing contact surfaces of the outward projections of the inner rotor contact the leading contact surfaces of the inward projections, the leading surface of each inner rotor outward projection does not seal and can be any shape as long as it prevents the rotors from locking up when the pump is freespinning or backturning. 
         [0011]    A pump, comprising: 
         [0012]    an outer housing having an inward facing cylindrical or partially cylindrical surface. 
         [0013]    an outer rotor with radial inward projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0014]    a carrier secured for rotation at least partly within the outer housing; 
         [0015]    an inner rotor secured for rotation about an axis within the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface; 
         [0016]    the inward projections projecting inward and the outward projections projecting outward to mesh with each other and define variable volume chambers between the inward projections and the outward projections as the inner rotor rotates within the carrier; 
         [0017]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers; and 
         [0018]    other advantages of driving the outer rotor include the ability to drive subsequent stages with a drive shaft that extends from both ends of one or more outer rotors to drive multiple similarly constructed outer rotors, coaxial stator shaft through the center of the drive shaft would be supported (at the opposite end from the drive shaft input) to the pump casing and would prevent the inner rotor housings from spinning 
         [0019]    A pump, comprising: 
         [0020]    an outer housing having an inward facing cylindrical or partially cylindrical surface. 
         [0021]    an outer rotor with radial inward projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0022]    a carrier secured for rotation at least partly within the outer housing; 
         [0023]    an inner rotor secured for rotation about an axis within the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface; 
         [0024]    the inward projections projecting inward and the outward projections projecting outward to mesh with each other and define variable volume chambers between the inward projections and the outward projections as the inner rotor rotates within the carrier; 
         [0025]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers; and 
         [0026]    in one configuration of the pump, it is designed to handle the admission and pumping of breakable solids such as but not limited to methane hydrate ice crystals, it does this with a combination of features such as sharp leading edges on spinning components and sharp trailing edges on stationary components which will slice the ice as it flows into and through the pump. It is also designed to minimized areas where ice could become wedged and restrict the flow by using increasing cross sections along the flow path. 
         [0027]    A pump, comprising: 
         [0028]    an outer housing having an inward facing cylindrical or partially cylindrical surface. 
         [0029]    an outer rotor with radial inward projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0030]    a carrier secured for rotation at least partly within the outer housing; 
         [0031]    an inner rotor secured for rotation about an axis within the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface; 
         [0032]    the inward projections projecting inward and the outward projections projecting outward to mesh with each other and define variable volume chambers between the inward projections and the outward projections as the inner rotor rotates within the carrier; 
         [0033]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers; and 
         [0034]    by providing fluid pressure to the outlet port of the pump configuration described above and shown in the drawings, the device can also be used in reverse rotation as a hydraulic motor. In this case, the leading convex edges of the inner rotor feet contact the flat or substantially flat trailing surface of the outer rotor which drives the output shaft. 
         [0035]    A fluid transfer device, comprising: 
         [0036]    an outer housing having an inward facing cylindrical or partially cylindrical surface. 
         [0037]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0038]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor; 
         [0039]    an inner rotor secured for rotation about an axis within the carrier, the inner rotor having an outward facing surface plane perpendicular to the inner rotor axis and outward projections arranged around the outward facing surface, and a trailing convex surface on each outward projection, the leading face of the radial projections and the trailing convex face of the outward projections mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0040]    the radial projections each having a leading edge and trailing edge; 
         [0041]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers. 
         [0042]    Method of using a pump of any preceding claim in which the pump is ideally suited to pump gases entrapped in a compressible fluid as follows: Gas bubbles that enter the pump are centrifuged to the innermost area of each outer rotor cylinder chamber; When the inner rotor foot rapidly enters the chamber in the discharge port zone, it will create an acceleration force on the fluid which is in the opposite direction of the centrifugal force on the fluid up to that point; This causes the higher density fluid to swap radial positions with at least some of the entrained gas, effectively pushing a bubble of gas out ahead of (radially outward from) the fluid as it exits the rotating chamber. The flow reliefs on the inner rotor are shown as being on the bottom but may be top, bottom or center. 
         [0043]    A gas compatible design as described above, in which the rotational axis is preferably (but not necessarily) vertical and the inner rotor has a flow relief (which exists between the trailing convex contact surfaces of each subsequent inner rotor foot) only on the bottom of the inner rotor so gravity can bias the higher density liquid to the bottom of the chamber and the gas to the top of the rotating chamber as it moves from the input to the output area of the pump; the top sealing surface of the inner rotor is therefore more adequately sealed against gas leakage (by virtue of it spanning a greater circumferential span of the chamber) and is capable of pushing at least part of the entrained gas out of each chamber during each rotation. 
         [0044]    A fluid transfer device, in which in the case of entrained gas, it is preferable to not push all of the gas out of the chamber at once, this will reduce input torque and pressure variations for smoother operation and longer service life. 
         [0045]    A fluid transfer device, in which the pump is also ideally suited to pump grit such as sand. In this case, the port leading up to a pumping stage is preferably curved along an arced or helical path to centrifuge the heavier sand to the outer surface of the flow path. The will bias the higher density sand and/or other abrasives away from the intake rotor sliding interaction with the outer rotor. The sand then travels around the outer perimeter of the casing and cylinder volume to the discharge port where centripetal force ejects and biases it away from the rotor sliding interaction. The multiple seal of the cylinder wall outer surfaces and casing wall inner surface allows the perimeter area (where the sand will be sliding) to have a larger gap clearance while still preventing high leakage rates. 
         [0046]    A fluid transfer device, comprising: 
         [0047]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0048]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0049]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor; 
         [0050]    an inner rotor secured for rotation about an axis within the carrier, the inner rotor having an outward facing surface plane perpendicular to the inner rotor axis and outward projections arranged around the outward facing surface, and a trailing convex surface on each outward projection, the leading face of the radial projections and the trailing convex face of the outward projections mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0051]    the radial projections each having a leading edge and trailing edge; 
         [0052]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the radius of the trailing convex surface on the inner rotor is substantially equal to the offset distance of the leading face of the radial projections on the outer rotor from the radial line form the axis of the outer rotor. 
         [0053]    A fluid transfer device, comprising: 
         [0054]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0055]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0056]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor; 
         [0057]    an inner rotor secured for rotation about an axis within the carrier, the inner rotor having an outward facing surface plane perpendicular to the inner rotor axis and outward projections arranged around the outward facing surface, and a trailing convex surface on each outward projection, the leading face of the radial projections and the trailing convex face of the outward projections mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0058]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0059]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0060]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance than the trailing surface such that fluid pressure is allowed to communicate with the chamber ahead of it. 
         [0061]    A fluid transfer device, comprising: 
         [0062]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0063]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0064]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0065]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, and a trailing convex surface on each outward projection, the leading face of the radial projections and the trailing convex face of the outward projections mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0066]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0067]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0068]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance than the trailing surface such that fluid pressure is allowed to communicate with the chamber ahead of it, and the outer cylindrical surface of each projection of the inner rotor is substantially cylindrical and in sealing proximity to the inward facing cylindrical surface of the carrier for part of the rotation, and the rotational power to the device is input to the outer rotor. 
         [0069]    A fluid transfer device, comprising: 
         [0070]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0071]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0072]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a inward facing surface that is at least partially circular along any plane perpendicular to the inner rotor axis; 
         [0073]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, and a trailing convex surface on each outward projection, the leading face of the radial projections and the trailing convex face of the outward projections mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0074]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0075]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0076]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance than the trailing surface such that fluid pressure is allowed to communicate with the chamber ahead of it up to the contact between the trailing convex surface of the preceding inner rotor projection contact with the leading offset radial surface of the preceding radial projection of the outer rotor; 
         [0077]    and the outer surface of each projection of the inner rotor is at least partially substantially circular along any plane perpendicular to the center axis of the inner rotor and in sealing proximity to the inward facing surface of the carrier for part of the rotation, and the carrier is secured from radial movement by a shaft which is coaxial with the outer rotor rotational axis and a bearing between the carrier shaft and the outer rotor. [0079] 
         [0078]    A fluid transfer device, comprising: 
         [0079]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0080]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0081]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a inward facing surface that is at least partially circular along any plane perpendicular to the inner rotor axis; 
         [0082]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, and a trailing convex surface on each outward projection, the leading face of the radial projections and the trailing convex face of the outward projections mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0083]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0084]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0085]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance than the trailing surface such that fluid pressure is allowed to communicate with the chamber ahead of it up to the contact between the trailing convex surface of the preceding inner rotor projection contact with the leading offset radial surface of the preceding radial projection of the outer rotor; 
         [0086]    the outer surface of each projection of the inner rotor is at least partially substantially circular along any plane perpendicular to the center axis of the inner rotor and in sealing proximity to the inward facing surface of the carrier for part of the rotation, and the carrier is secured from radial movement by a shaft which is coaxial with the outer rotor rotational axis and a bearing between the carrier shaft and the outer rotor, and the rotational power to the device is input to the outer rotor. 
         [0087]    A fluid transfer device, comprising: 
         [0088]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0089]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0090]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0091]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, the outward projections each having a cylindrical outward facing surface and a trailing convex surface, the leading face of the radial projections on the outer rotor and the trailing convex face of the outward projections on the inner rotor mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0092]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0093]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0094]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance and/or a relieved area proximal to the trailing face of the outer rotor radial projection preceding it such that fluid pressure in that chamber is allowed to at least partially equalize with the fluid pressure in the chamber preceding it between the outward and trailing surfaces of the preceding inner rotor projection and the forward facing face of the preceding outer rotor radial projection up to the contact between the trailing convex surface of the preceding inner rotor projection and the leading offset radial surface of the preceding outer rotor projection, and the outer cylindrical surface of each projection of the inner rotor is in sealing proximity to the inward facing cylindrical surface of the carrier for part of the inner rotor rotation. 
         [0095]    A fluid transfer device, comprising: 
         [0096]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0097]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0098]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0099]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, the outward projections each having a cylindrical outward facing surface and a trailing convex surface, the leading face of the radial projections on the outer rotor and the trailing convex face of the outward projections on the inner rotor mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0100]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0101]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0102]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance and/or a relieved area proximal to the trailing face of the outer rotor radial projection preceding it such that fluid pressure in that chamber is allowed to at least partially equalize with the fluid pressure in the chamber preceding it between the outward and trailing surfaces of the preceding inner rotor projection and the forward facing face of the preceding outer rotor radial projection up to the contact between the trailing convex surface of the preceding inner rotor projection and the leading offset radial surface of the preceding outer rotor projection, and the outer cylindrical surface of each projection of the inner rotor is in sealing proximity to the inward facing cylindrical surface of the carrier for part of the inner rotor rotation and the rotational power to the device is input to the outer rotor. 
         [0103]    A fluid transfer device, comprising: 
         [0104]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0105]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0106]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0107]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, the outward projections each having a cylindrical outward facing surface and a trailing convex surface, the leading face of the radial projections on the outer rotor and the trailing convex face of the outward projections on the inner rotor mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0108]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0109]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0110]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance and/or a relieved area proximal to the trailing face of the outer rotor radial projection preceding it such that fluid pressure in that chamber is allowed to at least partially equalize with the fluid pressure in the chamber preceding it between the outward and trailing surfaces of the preceding inner rotor projection and the forward facing face of the preceding outer rotor radial projection up to the contact between the trailing convex surface of the preceding inner rotor projection and the leading offset radial surface of the preceding outer rotor projection, and the outer cylindrical surface of each projection of the inner rotor is in sealing proximity to the inward facing cylindrical surface of the carrier for part of the inner rotor rotation and the rotational power to the device is input to the outer rotor, and the sealed chamber is partially defined by planar side faces of the outer rotor. 
         [0111]    A fluid transfer device, comprising: 
         [0112]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0113]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0114]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0115]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, the outward projections each having a cylindrical outward facing surface and a trailing convex surface, the leading face of the radial projections on the outer rotor and the trailing convex face of the outward projections on the inner rotor mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0116]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0117]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0118]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance and/or a relieved area proximal to the trailing face of the outer rotor radial projection preceding it such that fluid pressure in that chamber is allowed to at least partially equalize with the fluid pressure in the chamber preceding it between the outward and trailing surfaces of the preceding inner rotor projection and the forward facing face of the preceding outer rotor radial projection up to the contact between the trailing convex surface of the preceding inner rotor projection and the leading offset radial surface of the preceding outer rotor projection, and the outer cylindrical surface of each projection of the inner rotor is in sealing proximity to the inward facing cylindrical surface of the carrier for part of the inner rotor rotation and the rotational power to the device is input to the outer rotor and the sealed chamber is partially defined by a planar side face of the outer housing. 
         [0119]    A fluid transfer device, comprising: 
         [0120]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0121]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis;. 
         [0122]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0123]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, the outward projections each having a cylindrical outward facing surface and a trailing convex surface, the leading face of the radial projections on the outer rotor and the trailing convex face of the outward projections on the inner rotor mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0124]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0125]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0126]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance and/or a relieved area proximal to the trailing face of the outer rotor radial projection preceding it such that fluid pressure in that chamber is allowed to at least partially equalize with the fluid pressure in the chamber preceding it between the outward and trailing surfaces of the preceding inner rotor projection and the forward facing face of the preceding outer rotor radial projection up to the contact between the trailing convex surface of the preceding inner rotor projection and the leading offset radial surface of the preceding outer rotor projection, and the outer cylindrical surface of each projection of the inner rotor is in sealing proximity to the inward facing cylindrical surface of the carrier for part of the inner rotor rotation and the rotational power to the device is input to the outer rotor and the sealed chamber is partially defined by a planar side face of the outer rotor perpendicular to the axis of the outer rotor and a planar face of the perpendicular to the axis of the outer rotor. 
         [0127]    A fluid transfer device, comprising: 
         [0128]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0129]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0130]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0131]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, the outward projections each having a cylindrical outward facing surface and a trailing convex surface, the leading face of the radial projections on the outer rotor and the trailing convex face of the outward projections on the inner rotor mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0132]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0133]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0134]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance and/or a relieved area proximal to the trailing face of the outer rotor radial projection preceding it such that fluid pressure in that chamber is allowed to at least partially equalize with the fluid pressure in the chamber preceding it between the outward and trailing surfaces of the preceding inner rotor projection and the forward facing face of the preceding outer rotor radial projection up to the contact between the trailing convex surface of the preceding inner rotor projection and the leading offset radial surface of the preceding outer rotor projection, and the outer cylindrical surface of each projection of the inner rotor is in sealing proximity to the inward facing cylindrical surface of the carrier for part of the inner rotor rotation and the rotational power to the device is input to the outer rotor and the sealed chamber is partially defined by a planar side face of the outer housing, and the outer rotor is supported for rotation at both axial ends. 
         [0135]    A fluid transfer device, comprising: 
         [0136]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0137]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0138]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0139]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, the outward projections each having a cylindrical outward facing surface and a trailing convex surface, the leading face of the radial projections on the outer rotor and the trailing convex face of the outward projections on the inner rotor mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0140]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0141]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0142]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance and/or a relieved area proximal to the trailing face of the outer rotor radial projection preceding it such that fluid pressure in that chamber is allowed to at least partially equalize with the fluid pressure in the chamber preceding it between the outward and trailing surfaces of the preceding inner rotor projection and the forward facing face of the preceding outer rotor radial projection up to the contact between the trailing convex surface of the preceding inner rotor projection and the leading offset radial surface of the preceding outer rotor projection, and the outer cylindrical surface of each projection of the inner rotor is in sealing proximity to the inward facing cylindrical surface of the carrier for part of the inner rotor rotation and the rotational power to the device is input to the outer rotor and the sealed chamber is partially defined by a planar side face of the outer housing, and the inner rotor is supported for rotation at both axial ends. 
         [0143]    A fluid transfer device, comprising: 
         [0144]    an outer housing having an inward facing cylindrical or partially cylindrical surface; 
         [0145]    an outer rotor with radial projections having at least a leading face which is, along any plane perpendicular to the outer rotor axis, offset from a radial line radiating from the outer rotor rotational axis; 
         [0146]    a carrier secured to prevent rotation relative to the outer housing at least partly within the outer rotor, the carrier having a partially cylindrical inward facing surface; 
         [0147]    an inner rotor secured for rotation about an axis within the cylindrical inward facing surface of the carrier, the inner rotor having an outward facing surface and outward projections arranged around the outward facing surface, the outward projections each having a cylindrical outward facing surface and a trailing convex surface, the leading face of the radial projections on the outer rotor and the trailing convex face of the outward projections on the inner rotor mesh with each other and define variable volume chambers between the leading offset radial face and the trailing convex face of the outward projections as the inner rotor rotates within the carrier; 
         [0148]    the radial projections on the outer rotor each having a leading face and trailing face; 
         [0149]    the outward projections of the inner rotor each having a leading surface and trailing surface 
         [0150]    fluid transfer passages on at least one of the outer housing and carrier to permit flow of fluid into and out of the variable volume chambers and the leading surface of the inner rotor projections has a larger gap clearance and/or a relieved area proximal to the trailing face of the outer rotor radial projection preceding it such that fluid pressure in that chamber is allowed to at least partially equalize with the fluid pressure in the chamber preceding it between the outward and trailing surfaces of the preceding inner rotor projection and the forward facing face of the preceding outer rotor radial projection up to the contact between the trailing convex surface of the preceding inner rotor projection and the leading offset radial surface of the preceding outer rotor projection, and the outer cylindrical surface of each projection of the inner rotor is in sealing proximity to the inward facing cylindrical surface of the carrier for part of the inner rotor rotation and the rotational power to the device is input to the outer rotor and the sealed chamber is partially defined by a planar side face of the outer housing, and the inner and outer rotors are supported for rotation at both axial ends. 
         [0151]    These and other aspects of the device and method are set out in the claims, which are incorporated here by reference. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0152]    Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which: 
           [0153]      FIG. 1  is an isometric view of a design according to U.S. Pat. No. 7,111,606 (the &#39;606 design); 
           [0154]      FIG. 2  is a top view of an outer rotor and inner rotor of the &#39;606 design; 
           [0155]      FIG. 3  is a top view of a housing for the first embodiment of the &#39;606 design; 
           [0156]      FIG. 4  is a first view illustrating a progressive cycle of compression of a compression chamber of the &#39;606 design; 
           [0157]      FIG. 5  is a second view illustrating a second position of a cycle of compression of a compression chamber where the base of a foot begins displacing the gas contained therein of the &#39;606 design; 
           [0158]      FIG. 6  is a third view illustrating a third stage and a compression cycle of a compression chamber where a portion of the compression chamber is exposed to and exit passage of the &#39;606 design; 
           [0159]      FIG. 7  is a fourth view illustrating the progression of a compression cycle of the &#39;606 design; 
           [0160]      FIG. 8  is at this view illustrating the final phase of a single compression cycle for a compression chamber of the &#39;606 design; 
           [0161]      FIG. 9  is a schematic view illustrating the geometries for the outer circle and inner circle of the &#39;606 design; 
           [0162]      FIG. 10  shows the outer circle and inner circles superimposed upon the outer rotor and inner rotor respectively of the &#39;606 design; 
           [0163]      FIG. 11  shows the geometric relationship of the inner and outer rotor where the method of defining the contact surfaces for the legs of the inner rotor and the fans of the outer rotor a shown of the &#39;606 design; 
           [0164]      FIG. 12  shows a day modification to the first embodiment where to interior rotors are employed wall maintain an aspect ratio of two to one with respect to the outer and inner reference circles of the &#39;606 design; 
           [0165]      FIG. 13  is an exploded view showing the method of calculating the contact surface for the leg of the inner rotor of the &#39;606 design; 
           [0166]      FIG. 14  shows an isometric view of the preferred embodiment where a plurality of interior rotors are employed of the &#39;606 design; 
           [0167]      FIG. 15  is an isometric view showing a backside of the preferred embodiment shown in  FIG. 18  or a scoop section is shown of the &#39;606 design; 
           [0168]      FIG. 16  is an isometric view showing a modification to the embodiment in  FIG. 18  where the casing provides openings for a pump configuration of the &#39;606 design; 
           [0169]      FIG. 17  is an isometric view showing the casing of the pump configuration of the &#39;606 design; 
           [0170]      FIG. 18  is an isometric this of the pump configuration of the preferred embodiment with the outer rotor placed inside the housing of the &#39;606 design; 
           [0171]      FIG. 19  is an isometric view of the end cap of the &#39;606 design; 
           [0172]      FIG. 20  is an isometric view of a close up an interior rotor of the preferred embodiment of the &#39;606 design; 
           [0173]      FIG. 20   a  is a second isometric view of the interior rotor engaging the fins of the exterior rotor of the &#39;606 design; 
           [0174]      FIG. 21  is a front view showing the geometric relationship of the reference circles the inner and outer rotors of the &#39;606 design; 
           [0175]      FIG. 22  is a close of the view in  FIG. 21  and shows the perpendicular distance from the outer reference radii to the endpoints of the inner rotor change with respects to rotation of both reference circles while maintaining a constant velocity at the intersect point of the &#39;606 design; 
           [0176]      FIG. 23  shows the geometric relationship with the forward surface of the toe region and the reference axis of the outer rotor that extends through an outer rotor fin of the &#39;606 design; 
           [0177]      FIG. 24  shows an isometric view of a foot region of an inner rotor and the surface of a fin that is adapted to engage the surface of the toe region of the foot of the &#39;606 design; 
           [0178]      FIG. 25  is a front view of the outer and inner reference circle showing various variables that are used to mathematically define the first and second surfaces of the fins of the &#39;606 design; 
           [0179]      FIG. 26  is a simplified top view of the prototype configuration of an embodiment of the present invention with transparent casing; 
           [0180]      FIG. 27  is a simplified top view of an embodiment of the present invention with no top casing, in which the arrow shows the rotational direction of the rotors when operated as a pump (as a hydraulic motor, rotation would be in the opposite direction); 
           [0181]      FIG. 28  is a simplified iso view of an embodiment of the present invention with no top casing; 
           [0182]      FIG. 29  is a simplified iso view of an embodiment of the present invention with no casing; 
           [0183]      FIG. 30  is a simplified top view of an embodiment of the present invention with no casing (fasteners not shown in any views); 
           [0184]      FIG. 31  is a simplified schematic bottom view of the discharge port of an embodiment of the present invention with no casing showing entrained gas handling capability (when inner rotor foot enters the chamber, the acceleration on the fluid is in the opposite direction and all or part of the lighter gas is pushed out of the chamber first); 
           [0185]      FIG. 32  is a simplified top view of an embodiment of the present invention with bottom casing only, the casing showing entrained sand handling capability (white arrows show path of denser particles that enter the pump on a helical path and are biased away from the inner rotor sliding interface by centripetal force); and 
           [0186]      FIG. 33  is a simplified schematic iso section view of an embodiment of the present invention showing coaxial multi stage configuration (no casing shown). 
       
    
    
     DETAILED DESCRIPTION 
       [0187]    The following description is extracted from U.S. Pat. No. 7,111,606. 
         [0188]    Throughout this description reference is made to top and bottom, front and rear. The device of the present invention can, and will in practice, be in numerous positions and orientations. These orientation terms, such as top and bottom, are obviously used for aiding the description and are not meant to limit the invention to any specific orientation. 
         [0189]    To a description of the apparatus  20 , an axis system  10  is defined as shown in  FIG. 1  where the transverse axes is indicated by arrow  12 , arrow  14  is referred to as the crossword axis and is aligned to pass through centerpoints  50  and  26 . Finally, the axis orthogonal to both axes  12  and  14  are referred to as the wayward axis indicated by arrow  16 . 
         [0190]    The term fluid is defined as compressible and incompressible fluids as well as other particulate matter and mixtures that flows with respects to pressure differentials applied thereto. Displacing a fluid is defined as either compressing a fluid or transfer of an incompressible fluid from a high to low pressure location or allowing expansion of a fluid in a chamber. Engagement is defined as either having a fluid film or fluid film seal between two adjacent surfaces or be in contact or having interference between two surfaces where forceful contact occurs for a tight seal. 
         [0191]    In the following text, there will first be a description of the first embodiment with a detailed description of the geometries necessary to prevent surface interference between the inner rotor  24  and the outer rotor  22 . Finally, there is a description of several other preferred embodiments that utilized numerous internal rotors, which have inner reference circles that are at a ratio of number of legs (Λ) divided by the number of chambers (X) defined by the fins is equal to the radius of the inner reference circle r i  divided by the outer reference circle r o  (i.e. Λ/X=r i /r o ) and r i /r o  is &lt;½. 
         [0192]    As seen in  FIG. 1 , there is shown a first embodiment of the apparatus  20  comprising a rotor assembly  21  and a housing  25 . Shown in  FIG. 1 , the rotor assembly  21  comprises an outer rotor  22 , and an inner rotor  24 . The outer rotor  22  has an outside diameter d ( FIG. 2 ) and a center point indicated at  26  that indicates the location of the axis of rotation for the outer rotor  22 . The outer rotor further has a plurality of fins  28  discussed further herein. As shown in  FIG. 10 , the outside rotor further has an outer reference circle  80  and the inner rotor  24  has an inner reference circle  82  that is one half of the diameter of the outer reference circle  80 . The significance of this geometrical integer ratio requirement is discussed further herein. 
         [0193]    Now referring back to  FIG. 2 , the fins  28  each have a central axis  30  that extends through the center point  26 . The fins  28  further comprise a forward surface  32  and a rearward surface  34 . It should be noted that surfaces of  32  and  34  are substantially flat and aligned to the transverse axis. The outer rotor  22  further comprises the surface  40  that is located in the transverse plane and partially defined sealed chambers discussed further herein. As seen in  FIG. 2 , a semi chamber (or semi chamber region)  42   d  is defined as surface  40   d,  forward surface  32   d,  and rearward surface  34   c.  Located in the radially outward portion of the outer rotor  22  is a peripheral edge portion  44  that defines a circle about center point  26 . The peripheral edge  44  is adapted to intimately engage the housing  25  to form a compression chamber discussed further herein. 
         [0194]    The inner rotor  24  has a center of rotation indicated at  50  and a plurality of legs  52 . Each leg has a foot portion  54  that has a toe portion  58 . The foot  54  further comprises a radially outward surface  60 . The toe portion  58  has a toe surface  64  that as adapted to engage the forward surface  32  of the fins  28 . 
         [0195]    Each leg  52  further has a rearward surface  65  and a forward surface  66 . Opposing forward and rearward surfaces  65  and  66  facing one another (e.g.  66   d  and  65   c ) define an inner rotor chamber  67 . 
         [0196]    There will now be a discussion of the geometric relationship between the inner rotor  24  and the outer rotor  22 . As previously mentioned above,  FIG. 2  shows an embodiment where the rotor  24  has nine legs  52  with nine corresponding foot portions  54 . The radially outward surface surfaces  60  of the foot portions  54  define at least in part a circular cylinder in the transverse axis about center point at  50 . As shown in  FIG. 2 , there are twelve semi chamber regions  42  of the outer rotor  22 . The number of semi chamber regions in the outer wheel in the embodiment shown in  FIG. 2  is twice the number of legs  52  of inner rotor  24 . 
         [0197]    As previously mentioned above, in the first embodiment the circumference the outer reference circle  80  of the outer rotor  22  is exactly twice the circumference of the inner reference circle  82  of the inner rotor  24 . Therefore, as the inner rotor wheel  24  rotates about center point  50 , the inner rotor&#39;s rotations per minute is exactly twice the rotations per minute of the outer rotor  22 . The ratio between the circumferences of the inner rotor  24  and the outer rotor  22  is a factor of two. As discussed further herein the ratios between the inner rotors and the outer rotor will be the ratio of the number of legs  52  and fins  28  of the inner and outer rotors as a direct relationship with ratio of the inner and outer radii of the inner and outer rotors  24  and  22 . In other words the number of legs (Λ) divided by the number of chambers (X) defined by the fins is equal to the radius of the inner reference circle r i  divided by the outer reference circle r o  (i.e. Λ/X=r i / r o ). 
         [0198]    Of course there is a linear relationship between the radius, diameter, and circumference of a circle. Therefore, the ratios between the diameter of the inner rotor  24  and the diameter of the outer rotor  22  is the same as the ratio between the circumference of the inner rotor  24  and the circumference of the outer rotor  22 . 
         [0199]    There will now be a discussion of the forward surface  32  of the outer rotor  22  with reference being made to  FIGS. 9-11 .  FIG. 9  shows an outer reference circle  80  and an inner reference circle  82 . The outer reference circle has sixteen pie sections spaced at twenty two and a half degrees defining outer reference points  84   a - 84   p . The inner reference circle  82  has eight evenly spaced pie sections at forty-five degrees defining inner reference points  86   a - 86   h.    
         [0200]    The center point  26  shown in  FIG. 9  is the center of outer reference circle  80 , and center point  50  is the center of inner circle  82 . The radius of the outer circle indicated by r o  is exactly twice see inner radius r i . The circumference of a circle is a linear relationship with respects to the radius. The well-known equation is c=2πr. Therefore, one-half of a radius yields exactly one-half the circumference. Further, forty-five degrees of circumference section  88  for the inner circle  82  yields exactly one-half of the circumferential distance of forty-five degrees circumference section  90  for the outer circle  80 . Therefore, twenty two and a half degrees (½ of forty five degrees) circumferential section  92  for the outer circle  80  yields the exact same circumferential distance as a  45  degree circumferential length  88  for the inner circle  82 . So as the outer circle  80  rotates about center point  26  and the inner circle  82  rotates about center point  50  and the perimeters of each circle at point  84   a  move at the same speed, the inner circle  82  will rotates at exactly twice the rotational velocity of the outer circle  80 . This rotational scheme is defined as the dual rotation. 
         [0201]    By having the inner radius r i  one-half the length of the outer radius r o  there is an interesting mathematical phenomena where points  86  define linear lines on the outer circle  80  during dual rotation. In other words, as the circles rotate in the dual rotation fashion point  86   d  defines straight line  84   d.  Likewise, all of the points about the circumference of the inner circle define straight lines radially extending from the center point  26  are the outer circle  80 . 
         [0202]    With the foregoing geometric relationships in mind, reference is now made to  FIG. 10  where the inner and outer circles  80  and  82  are superimposed upon the rotor assembly of the first embodiment. The point  86   a  is located on the toe portion of leg  52   a  and point  84   a  is at the exact same location. This location is referred to as the contact point where the circumference is of the inner circle  82  and the outer circle  80  cross. The line  84   a ′ extends to point  86   a  when point  86   a  is in the contact point position. The toe surface  64  is defined by a semi-circle having a center point at  84   a  and a radius of  90   a  (see  FIG. 11 ). The center of toe surface  64  is point  86   a.  Therefore all points along toe surface  64  are equidistant from the point  86   a  at a distance  90   a.  To reiterate the geometric relationship phenomenon, as the inner and outer rotors  24  and  22  rotate in the dual rotation scheme described above, the point  86   a  will travel along the line  84   a ′. Therefore, rearward surface  32   a  must be parallel to line  84   a ′. In other words, as point  86   a  travels radially inwardly along line  84   a ′ during the dual rotation scheme, the surface  32   a  must be parallel to radially extending line  84   a ′ to avoid interference between the surface  32   a  and the toe surface  64 . 
         [0203]    The same analysis can be conducted for all of the fins  28  with the respective legs  52  lined adjacent thereto. 
         [0204]    It should be noted that the preferred surface for the first embodiment toe heel surface  64  is a semi-circle about a point. The semi-circle allows the fins to have non-curved surfaces that radially extend from the outer reference circle  80 . Other circular shapes for the toe surface  64  could be employed with a varying radius. 
         [0205]    In addition to having the reference circles  80  and  82  radii (and circumferences) a ratio of two to one, it is just as important to have the number of fins  28  line of the outer rotor twice in quantity as the number of legs  52  line of the inner rotor (see  FIGS. 9-11 ). This integer ratio is crucial for having continuous rotation of the inner and outer rotors free from having a leg crashed down upon a fin for the first embodiment. 
         [0206]    There will now be a discussion of the rotor assembly mounted in the housing  25  along with the various components of the apparatus  20  followed by a description of the pumping or displacement scheme. 
         [0207]      FIG. 1  shows the rotor assembly with the housing  25  in conjunction with the inner rotor  24  and the outer rotor  26 . As seen in  FIG. 3 , the housing  25  is preferably a unitary designed having a central area  94 , an exit/entrance portion  96 , a discharge region  98 , an entrance region  100 , an outer rotor annular slot  102 , an inner rotor annular slot  104 , a high compression region  106 , an expansion region  108  and finally an annular support region  110 . The outer rotor annular slot  102  is adapted to house the outer rotor  22  (see  FIG. 2 ). The outer rotor  22  can rotate therein slot  102  and press upon the inward annular surface  112  and the outward annular surface  114 . Further, the annular slot has a surface  116  adapted to support the lower surface of the outer rotor  22 . The inner rotor annular slot  104  is defined by radially inward facing surface  118  and a radially outward facing surface  120 . The radially outward facing surface  120  is adapted to position the inner rotor  24 . Further, the radially inward surface  118  is in close engagement with the radially outward surface  60  of the inner rotor  24 . Therefore, surfaces  118  and  120  independently cooperate to hold inner rotor  24  and place to rotate about center point  50 . 
         [0208]    The outer rotor annular slot  102  and inner rotor annular slot  104  cooperate to assist in positioning the outer rotor  22  and inner rotor  24  so both rotors rotate about centerpoints  26  and  50  respectively. 
         [0209]    The airflow into and out of the rotor assembly  20  is accomplished by the exit/entrance portion  96 , the discharge region  98 , and finally the entrance region  100 . The exit/entrance portion  96  comprises an exit passage  122  and an entrance passage  124 . The exit passage  122  comprises a first surface  126 , a second surface  128  and upper and lower surfaces  130  and  132 . A boundary corner is defined at numeral  134  and a second corner portion is indicated at  136 . The entrance passage  124  comprises a first surface  138 , a second surface  140 , an upper and lower surfaces  144 . A corner portion  146  is located at the juncture between surface  112   b  and first surface  138 . 
         [0210]    To properly understand the air flow scheme of the apparatus  20  there will first be a discussion of the chamber volume displacement. In general, a compression chamber  148  is defined by the radially outward surface  60   a,  the forward surface  32   a,  the rearward surface  34   b  the radially inward surface  112   a  and finally the upper and lower surfaces of the outer rotor  22 . 
         [0211]    The gas entrance phase will now be discussed with reference again made to  FIGS. 4-8 . 
         [0212]    As seen in  FIG. 4 , gas enters in entrance passage  124  and enters into expansion chamber  150 . The expansion chamber  150  is defined as the particular inner rotor chamber  67  that is in communication with entrance passage  124 . 
         [0213]    As seen in  FIG. 6 , the inner rotor chamber  67   b  is not directly in communication with exit passage  122 ; however, the seal between fin  28   c  and toe portion  58   c  of leg  52   c  is not a perfect seal and some higher pressure gas can seep into chamber  67   b.    
         [0214]    As the inner and outer rotors  22  and  24  are positioned in the matter shown in  FIG. 5 , inner rotor chamber  67   b  is now substantially sealed from exit passage  122  and entrance passage  124 . However, the pressure in chamber  67   b  may be slightly greater than the pressure in entrance passage  124 . 
         [0215]    As seen in  FIG. 5 , the leg  52   c  is near the radially inward portion of entrance passage  124 . Shown in  FIG. 6 , the inner rotor  24  has rotated additional degrees clockwise and the expansion chamber  150  is increasing in volume. It is important to note that it is undesirable to have the expansion chamber  150  sealed and not be in communication with the entrance passage  124 . If the expansion chamber was substantially sealed between surfaces  112   c,    34   d,    32   c  and  60   c  as the chamber  150  increases in volume corresponding to the clockwise rotation of rotors  22  and  24 , the low-pressure therein would create a counter clockwise force as a result of the tangential surface difference between rearward surface  34   d  and forward surface  32   c.    
         [0216]    As seen in  FIG. 7 , the expansion chamber  150  has increased in volume with respect to the location in  FIG. 6 . The distance dr 1  indicates the amount of surface area exposed in the radial direction (presuming a finite amount of depth). The distance dr 2  represents the amount of surface area in the radial direction for the fin  28   d.  It is therefore apparent that a positive clockwise torque is created upon the outer rotor due to the increase in surface area of distance dr 2  over dr 1 . 
         [0217]    In  FIG. 8  the expansion chamber is fully expanded and now defined by the surfaces  112   c,    114   b  and forward surface  32   c  and rearward surface  34   d.  Finally, the air is subjected a centrifugal force and ejected through the discharge region  98 . 
         [0218]    There will now be a discussion of how air enters into the semi chamber regions  42  of the outer rotor  22 . As seen in  FIG. 1 , as the outer rotor  22  rotates in the direction indicated by arrow  151 . The air is drawn in through the entrance region  100 . The entrance region  100  comprises glide surface  152  having generally downward slope in the radial outward and tangentially clockwise direction. As discussed above, the rotations per minute of the outer rotor  22  are in the order of magnitude in the thousands to hundreds of thousands with certain materials in certain configurations. At this high-speed air channeled through the entrance region  100  is “pre-compressed” into the semi chambers  42 . The compression at this phase is similar to a centrifugal compressor. When the rearward fin  28  of semi chamber  42  passes the position  154  ( FIG. 3 ) the semi chamber is now substantially sealed and ready for the gas contained therein to pass to the high compression region  106 . 
         [0219]    We have thus far discussed one embodiment of the present invention, which employs a single outer rotor  22  and a single inner rotor  24 . There will now be a discussion of a second embodiment employing two inner rotors while still maintaining a two to one ratio between the outer reference circle  380  of the outer rotor  322  and the inner rotors  324 . The numerals designating the components of the second embodiment will correspond, where possible, to the numerals describing similar components except the numeric values will be increased by three hundred. 
         [0220]    As shown in  FIG. 12 , the rotor assembly  321  comprises an outer rotor  321 , a first inner rotor  324  and a second inner rotor  324 ′. 
         [0221]    The outer rotor  321  is very similar to the outer rotors  22  in the first embodiment except for different angles of the forward and rearward surfaces  332  and  334 . The center point  326  is the center of rotation for the outer rotor  322 . The reference circle  380  for the outer rotor coincides with the peripheral edge  344  also having a center point  326 . 
         [0222]    The inner rotors  324  and  324 ′ are substantially similar and hence inner rotor  324  will be described in detail with the understanding the description also relates to inner rotor  324 ′. 
         [0223]    The inner rotor  324  comprises a plurality of legs  352  where each leg has a foot portion  354 . The foot portion  354  comprises a toe portion  358  and a radial outward surface  360 . The radial outward surface  360  defines a circle about point  350 . The inner reference circle for the inner rotor  324  is indicated at  382  and coincides with the circle defined by radially outward surface  360 . 
         [0224]    As seen in  FIG. 13 , the forward surface  364  of the toe portion  358  is semi-circular about point  386   a.  The point  386   a  lifelong the inner reference circle  382  (as well as the circle defined by radially outward surfaces  360 ). The significance of having the reference point at this radially outward extreme location from the center point  350  is discussed further herein. 
         [0225]    There is now a description of the forward and rearward surfaces  332  and  334  of the fins  328 . The analysis of the forward and rearward surface  332  and  334  is very similar to the analysis of surfaces  32  and  34  of the first embodiment discussed above referring to  FIGS. 9-10 . The main difference in the third embodiment is the point  386  is located on the radially outward surface  360 , whereas in the first embodiment the point  86  is located a distance radially inward from the radial outward surface  60 . 
         [0226]    The line  386   a ′ extends from the reference point  386   a  to the center point  326  of the outer reference circle  380  (see  FIGS. 12 and 13 ). When the inner and outer rotors  324  and  322  engage in the dual rotation scheme, the reference point  386   a  travels radially inward along line  386   a ′. Therefore, forward surface  332   a  must be parallel to the line  386   a ′. A similar analysis can be conducted for the rest of the surfaces  364  and  362  of the inner rotors  324  and  324 ′. 
         [0227]    By having the outer reference circle  382  coexisting with the radially outward surface  360  or slightly radially outward from radially outward surface  360 , the rotor assembly  321  can fit the second rotor  324 ′ into the housing as well. 
         [0228]    In a preferred form, the inner reference circles  382  and  382   a ′ are a small tolerance distance from the radially outward surfaces  360  and  360 ′ to avoid interference between these surfaces at the center point location  326 . 
         [0229]    The third embodiment is shown in  FIG. 14  where four inner rotors are employed. The third embodiment has advantages of allowing a throughput shaft that is attached to the outer rotor  422 . As with the previous embodiments, the numerals for the most part correspond with the first embodiment except increased by four hundred. 
         [0230]    The apparatus  420  has a rotor assembly  421  that comprises an outer rotor  422  and a plurality of inner rotors  424   a - 424   d.  The outer rotor has a reference circle  480  and a center of rotation indicated about axis  426 . Likewise, the inner rotors  424  have been inner reference circle  482 . In a similar manner with the previous embodiments the relationship between the circumference of the inner reference circle and the outer reference circle  482  and  480  is a ratio that is an integer and in this embodiment a ratio of 3-1. 
         [0231]    The relationship between the ratio of the number of legs  52  and fins  28  of the inner and outer rotors has a direct relationship with ratio of the inner and outer radii of the inner and outer rotors  24  and  22 . In other words the number of legs (Ε) divided by the number of chambers (X) defined by the fins is equal to the radius of the inner reference circle r i  divided by the outer reference circle r o  (i.e. Λ/X=r i /r o ). 
         [0232]    Further, the outer rotor has  18  fins and the inner rotors have six legs (a ratio of 3-1). It should be noted that although the third embodiment discloses four interior rotors  424 , there can be one—four interior rotors. However, having four interior rotors as particular benefits of balancing the force upon the central shaft described further herein. 
         [0233]    The rotor  422  further comprises a scoop region  431  best shown in  FIG. 15  which shows the backside of one of the rotor assembly support  420  of  FIG. 14 . As seen in  FIG. 15 , the scoop region  431  comprises a plurality of vanes  433  define channels  435  that channel the air radially inward to the longitudinal extensions  437 . Now referring to  FIG. 14 , the extensions  437  channel air into the chambers  442 . The scoop region  431  is connected to and can be a unitary structure with the outer rotor  422 .  FIG. 14  shows an embodiment where two apparatuses  420  are positioned in a back-to-back arrangement having two outer rotors  422  and eight inner rotors  424 . 
         [0234]    The apparatus  420  further comprises a central frame member  494  that has a central open region  495  and annular interior surfaces  518  that are adapted to house the inner rotors  424 . Further, a radially recessed region  497  allows communication to the longitudinal extensions  437  of the scoop region  431 . 
         [0235]    Finally, the apparatus  420  has a housing (not shown) that is connected to the front face  499  of the central frame member  494 . The housing provides a seal in a similar manner to the housing is shown in  FIG. 1 , except a plurality of interest and exit ports would be provided for each interior rotor  424 . 
         [0236]      FIG. 16  shows a pump version for the third embodiment where in general the entry and exit ports are modified to allow exit ports to be communication with any chamber that is displaced in volume to prevent compression of a fluid. The housing  425  is best shown in  FIG. 17  and comprises a plurality of entrance ports  520  and exit ports  522 . The entrance ports  520  comprise a radial outward slot portion  524 , an axial conduit  526 , and a toe portion passage  528 . 
         [0237]    The exit ports  522  comprise a radial outward slot portion  540  a radially extending slot  542  and a toe portion slot  544 . The radially extending slot and toe portion slot  542  and  544  are in communication with one another and are in communication with a central annular slot region  546  which is in turn in communication to the axial conduit  548 . 
         [0238]    As shown in  FIG. 18 , the outer rotor  560  is similar to the outer rotors discussed above, with the exception a plurality of ports  562  are provided and are adapted to communicate with the toe portion passages  528 .  FIG. 19  shows an endcap  570  that is adapted to the mounted upon the pump assembly shown in  FIG. 16 . The endcap  570  has a center crossmember  572  that provides a plurality of surfaces  574  that are adapted to house the interior rotors. The extensions  576  are adapted to extend to the central shaft of the interior rotors and allowing the interior rotors to rotate their around. The central region  578  is open and allows a shaft  580  (shown in  FIG. 18 ) pass therethrough. 
         [0239]    The pump embodiment can be used as a flow meter as well. The multi interior rotor embodiment is particularly advantageous because the center shaft can extend therethrough and the load balance upon the shaft is desirable where the primary force upon the shaft is the torque caused by the force of the inner rotors acting upon outer rotor. 
         [0240]    The two dimensional nature of the invention allows for variances of the geometries in the transverse direction. In other words in the transverse plane (the plane aligned in the wayword and crossword axes) at a given location in the transverse direction, the points on the inner and outer rotors  24  and  22  remain in the said plane during rotation. This is due to the axes of rotation for each rotor are parallel to each other. Therefore the geometry for the outer and inner rotors  22  and  24  can change with respects to the transverse position coordinate. To run the device in  FIG. 14  as an expander the sealed chamber that is formed with a housing similar to that of the first embodiment with a gas entrance passage would receive compressed gas and provide a torque to drive the outer rotor. 
         [0241]    There will now be a discussion of the geometric relationships between the inner and outer reference circles for the embodiments where the ratio of r i /r o  is less than  1 / 2 . For this example we will assume the inner reference circle radius, r i , is ⅓ of the outer reference circle, r o . 
         [0242]    Referring to  FIG. 21 , there will now be a discussion of the fundamental geometries that are used to define the engagement surfaces.  FIG. 21  is similar to  FIG. 9  except when the r i /r o  is not a factor of ½ then the exterior points on the inner reference circle  482  will not follow the path of the outer reference circle&#39;s radii during dual rotation (where velocity of travel is the same at the insect point as both circles rotate about their center axis. The outer reference circle  480  has a r o  of three units and the inner reference circle has an inner radius of r i  of one unit. Therefore the ninety degree circumferential section  481  of the inner circle  482  is equal in circumferential length to the thirty degree circumferential length  483  (see angle references  481 ′ and  483 ′). For this example, four points of rotation will be examined in the clockwise direction, 0°, 30°, 60°, and 90° indicated by r i 0 , r i 30 , R i 60  and r i 90  for the inner rotor  482  and corresponding angles of 60°, 70°, 80° and 90° indicated by r o 60 , r o 70 , r o 80  and r o 90  for the outer rotor  480 . The distal points of r i 0 , r i 30 , r i 60  and r i 90  intersect the corresponding distal points of r o 60 , r o 70 , r o 80  and r o 90  at the intersection location as both reference circles rotate. However, it is apparent that the corresponding radii (e.g. r o 60  and r i 0 ) do not intersect at other rotational positions at the distal point of the inner reference radius such shown in  FIG. 9 . 
         [0243]    Now referring to  FIG. 22 , additional reference radial are added. For this illustrative example each outer radii r o  is repositioned counter clockwise a fixed amount of degrees (e.g. 8° for this example) and numbered in the same reference degree offset fashion as r o 68 , r o 78 , r o 88  and r o 98 . These outer circle reference radii are similar to r o  as shown in  FIG. 20 . The perpendicular distance d 0  is defined as the reference radii r o 68  to the distal point of r i  0 indicated at P i  0 and the perpendicular distances d 30 , d 60  and d 90  are defined in a like fashion with reference radii r o 78 , r o 88  and r o 98  and points P i 30 , P i 60  and P i 90  respectively. It is therefore apparent that the perpendicular distances (d 0 , d 30 , d 60  and d 90 ) increase during the course of rotation. 
         [0244]    It should be reiterated that the subscript notations are the angle of rotation of the inner rotor (where 0° is to the right in the wayward axis direction and clockwise rotation is positive). 
         [0245]    Now referring back to  FIG. 20 , it should be noted that distance d′ 1 , is greater than d′ 2 . The point  486 ′ is near the bottom dead center portion of rotation. The point  486 ′ will continue to travel along the inner reference circle path  482  away from the outer reference circle  480 . Therefore as shown in  FIG. 20   a,  an extension region  481  is provided that is adapted to engage the outer surface indicated at the portion  483 . This extension region further supplies an additional advantage by increasing the compression ratio of the device. 
         [0246]    It should be noted that the inner reference radius r, i0  is primarily for exemplary purposes of an extreme location because of the difficulty of having a fin extend radially inwardly to engage the arc at that rotational position. 
         [0247]    There will now be a discussion of the engagement surface  464  of the toe region  458  with reference to  FIG. 23 . The toe region arc at the positions indicated at a′ 30 , a′ 60  and a′ 90  are centered about points P i 30 ., P i 60.  P i 90  respectively. The indicator lines  469  are ninety degrees from the inner radius reference lines r i  and are helpful for determining the angle of the orthogonal distances d f . The orthogonal d f30 , d f60  and d f90  increase as the rotors rotate clockwise to the 90 degree position and the d′ f30 , d′ f60  and d′ f90  that are defined as the orthogonal distances d f30 , d f60  and d f90  subtracted by the arc radius of arcs a′ in  FIG. 23 . It can be observed that the distances d′ f30 , d′ f60  and d′ f90  increase with clockwise rotation. The arc represents the engagement surface  464  as shown in  FIGS. 20   a  and  24 . Therefore with an arc that has a constant radius, the second defined distance d′ f  as shown in  FIG. 24  increases with respects to the radial location along the second reference radius shown at r o 82  and the engagement surface  432  of the fin  428  in  FIG. 24  must increase in distance from the outer reference radius r o 82  with respects to radially outward travel along r o 82 . 
         [0248]    Therefore as the perpendicular distance d f  changes with respects to the rotational position of the inner and outer rotors, the second defined distance  505  of the toe region is collinear with the second defined distance  507  (d′ f ) of the second fin  509  and their sum plus a desired gap totals the distance d f  that changes with respects to the rotational position of the inner and outer rotors. 
         [0249]    The distance  471  in  FIGS. 23 and 24  roughly indicates the location and magnitude of increased tangential distance between r o 82  and the distal portion of surface  432 . This accelerated increase in distance is because as seen in  FIG. 23  the orthogonal line  473  is above the ninety degree reference line  469  and indicates the shortest path from the reference point  486  to r o 82 . However, for clearance among the parts it is advantageous extend the material at extension portion  491  to engage the outer region  473  of the surface  464 . 
         [0250]    Therefore a preferred method of constructing the first and second surfaces  434  and  432  is sketch out a CAD drawing such as that in  FIG. 23  and rotate the inner circle  3  units and the outer circle  1  unit (the aspect ratio to r o /r i ) and enter in spline points that traces the path of the forward and rearward (second and first) fin surfaces with a desirable gap or interference fit thereinbetween. Then the inner chamber  435  ( FIG. 16 ) should be constructed in a manner to not interfere with the fin during rotation. 
         [0251]    To use the preferred embodiment as an expander the exit port is an entrance port and the fluid will fill the expanding sealed chamber. It is therefore apparent that the preferred embodiment utilizes nonlinear surfaces in the radial direction of the fins. It is important to note the desirable balancing loads radial loads upon the outer rotor when a plurality of inner rotors are employed. Further, a center throughput shaft can be attached to the outer rotor in the preferred embodiment. 
         [0252]    The mathematical model to define the surfaces of the fin is discussed below. 
         [0253]    To ease the explanation the first (toe surface of the fin will be defined using two coordinate systems O 1  and O 2 . The first coordinate system is referenced to the casing and is located at the center of rotation of the outer reference circle  480  of the outer rotor. Because we are interested in defining the surfaces of a fin of the outer rotor, a second coordinated system is defined at O 2  and the Y axis of the second coordinate system extends radially inward along the reference radius  484  which is the reference radius that extends through a point through the fin to be defined. 
         [0254]    The relationship between the rotational value θo of the reference circle to the rotational value θi of the inner reference circle is defined by the equation: 
         [0000]    
       
         
           
             
                 
             
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         [0255]    The angular location of the center of the toe arc  464 ′ are denoted by θt where each point  486  are rotationally offset from point  450  by a value θi_t_o for the toe region. These offsets represents the distance the points  486  and  486 ′ are from the center radius  484  of the fin to be defined. Therefore the resulting equation is:            
         [0256]    The position of the toe center point  486  with respects to the first axis O 1  are defined by x,y coordinates Xi —t and Yi   —t where Rip _t is the distance from the inner circle center point  450 . The point  486  lies on the circumference of the outer reference circle. However, the point  486  can be extended beyond the inner reference circle to define the first surface (toe fin surface)  464 ′:                      
         [0257]    The x,y location of the second origin O 2  in the first coordinate system is defined as:                      
         [0258]    The second coordinate system O 2  is referenced to the center axis  484  of a fin of the outer rotor. Therefore the second coordinate system changes position with respects to the first coordinate system during rotation of the inner and outer reference circles (corresponding to rotation of the inner and outer rotors). To convert from the first coordinate system O 1  to the second coordinate system O 2  the following functions are used.                      
         [0259]    Therefore, the arc center points  486  and  486 ′ in the second (fin) coordinate system is:            
         [0260]    which are expanded to the format:                      
         [0261]    Finally the offset from the center point  486  to the center fin axis in the second coordinate system axis is defined as the equations:                      
         [0262]    The above equations are for the toe surface where r_t is the radius or radius function for the toe surface arc and gap_t is the gap clearance distance or function to account for a fluid film gap. The expanded full form of the equations are:                      
         [0263]    Substituting in the variables for θo we get the equation: 
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         [0264]    to have the x,y values be a function of the θi (the inner rotation of the inner reference circle. 
         [0265]    It should be noted that the preferred embodiment allows for points of contact between the toe second engagement surface and the second surface of a second fin for a more than an instant point of rotation. The sealed chamber is in effect for more than a finite range of rotation (i.e. certain amount of rotation of the inner and outer rotors). In other words a sealed chamber is maintained for up to 45° of rotation of the inner rotor and possibly higher with longer thinner fins extending radially inwardly. 
         [0266]    Therefore it is apparent that the device has numerous applications for converting energy. While the invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as expressed in the appended claims. 
         [0267]    There will now be a discussion of the geometric relationships between the inner and outer reference circles for the embodiments where the ratio of r i /r o is less than  ½. 
         [0268]    For this example we will assume the inner reference circle radius, r i , is ⅓ of the outer reference circle, r o . 
         [0269]    As shown in  FIG. 20 , the heel portion of  456   a  of leg  452   a  comprises a surface  462   a  that is defined as a circular surface in the transverse plane about heel point  486 ′. It can be seen that as the inner rotor  424  rotates to a position as leg  452   b  the engagement point of surface  462   a  is at a more distal location. Further, the perpendicular distance between the heel point  486 ′ and the outer reference circle reference radius increases in the course of rotation (during the rotation compression phase). 
         [0270]    Referring to  FIG. 21 , there will now be a discussion of the fundamental geometries that are used to define the engagement surfaces.  FIG. 21  is similar to  FIG. 9  except when the r i /r o  is not a factor of ½ then the exterior points on the inner reference circle  482  will not follow the path of the outer reference circle&#39;s radii during dual rotation (where velocity of travel is the same at the insect point as both circles rotate about their center axis. The outer reference circle  480  has a r o  of three units and the inner reference circle has an inner radius of r i  of one unit. Therefore the ninety degree circumferential section  481  of the inner circle  482  is equal in circumferential length to the thirty degree circumferential length  483  (see angle references  481 ′ and  483 ′). For this example, four points of rotation will be examined in the clockwise direction, 0°, 30°, 60°, and 90° indicated by r i 0 , r i 30 , r i 60  and R i 90  for the inner rotor  482  and corresponding angles of 60°, 70°, 80° and 90° indicated by r o 60 , r o 70 , r o 80  and r o 90  for the outer rotor  480 . The distal points of r i 0 , r i 30 , r i 60  and r i 90  intersect the corresponding distal points of r o 60 , r o 70 , r o 80  and r o 90  at the intersection location as both reference circles rotate. However, it is apparent that the corresponding radii (e.g. r o 60  and r i 0 ) do not intersect at other rotational positions at the distal point of the inner reference radius such shown in  FIG. 9 . Therefore it is apparent that the engagement surfaces of the heel surface  462  and the forward fin surface  434  must adapt to this varying tangential distances. 
         [0271]    Now referring to  FIG. 22 , additional reference radial are added. For this illustrative example each outer radii r o  is repositioned counter clockwise a fixed amount of degrees (e.g. 8° for this example) and numbered in the same reference degree offset fashion as r o 68 , r o 78 , r o 88  and r o 98 . These outer circle reference radii are similar to r o  as shown in  FIG. 20 . The perpendicular distance d 0  is defined as the reference radii r o 68  to the distal point of r i 0  indicated at P i 0  and the perpendicular distances d 30 , d 60  and d 90  are defined in a like fashion with reference radii r 0 78 , r 0 88  and r 0 98  and points P i 30 , P 1 60  and P i 90  respectively. It is therefore apparent that the perpendicular distances (d 0 , d 30 , d 60  and d 90 ) increase during the course of rotation. 
         [0272]    Now referring back to  FIG. 20 , it should be noted that distance d′ 1 , is greater than d′ 2 . The point  486 ′ is near the bottom dead center portion of rotation. The point  486 ′ will continue to travel along the inner reference circle path  482  away from the outer reference circle  480 . Therefore as shown in  FIG. 20   a,  an extension region  481  is provided that is adapted to engage the outer surface indicated at the portion  483 . This extension region further supplies an additional advantage by increasing the compression ratio of the device. 
         [0273]    It should be noted that the inner reference radius r, i0  is primarily for exemplary purposes of an extreme location because of the difficulty of having a fin extend radially inwardly to engage the arc at that rotational position. 
         [0274]    To ease the explanation the first surfaces (heel surface of the fin will be defined using two coordinate systems O 1  and O 2 . The first coordinate system is referenced to the casing and is located at the center of rotation of the outer reference circle  480  of the outer rotor. Because we are interested in defining the surfaces of a fin of the outer rotor, a second coordinated system is defined at O 2  and the Y axis of the second coordinate system extends radially inward along the reference radius  484  which is the reference radius that extends through a point through the fin to be defined. 
         [0275]    The angular location of the center of the heel arc  462 ′ are denoted by θh where each point  486 ′ are rotationally offset from point  450  by a value θi_h_o for the heel region. These offsets represents the distance the points  486 ′ are from the center radius  484  of the fin to be defined. Therefore the resulting equations are is:            
         [0276]    The point  486 ′ lies on the circumference of the outer reference circle. However, the point  486 ′ can be extended beyond the inner reference circle to define the first and second surface (heel fin surface)  462 ′ and  464 ′. In a similar manner the position of the heel center point  462 ′ in the first axis O 1  coordinate system is defined by the equations:                      
         [0277]    Therefore, the arc center points  486 ′ in the second (fin) coordinate system are is:                      
         [0278]    which are expanded to the format:                      
         [0279]    Likewise for the heel surface, the equation to determine the perpendicular distance from the center point  486 ′ to the heel surface is defined as:                      
         [0280]    and the expanded forms are:                      
         [0281]    Substituting in the variables for θh and θo we get the equation: 
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         [0282]    to have the x,y values be a function of the θi (the inner rotation of the inner reference circle. 
         [0283]    The new variables r_h and gap gap_h represent the radius of the heel arc and the desired gap distances (or equations of they vary with respects to rotation). 
         [0284]    It should be noted that the preferred embodiment allows for points of contact between the-first engagement surface of the heel and the first surface of an adjacent fin for a more than an instant point of rotation. The sealed chamber is in effect for more than a finite range of rotation (i.e. certain amount of rotation of the inner and outer rotors). In other words a sealed chamber is maintained for up to 45° of rotation of the inner rotor and possibly higher with longer thinner fins extending radially inwardly. 
         [0285]    The design uses the basic design as in U.S. Pat. No. 7,111,606 as modified below. The following modifications are shown in the figures. 
         [0286]    When used as a pump, the larger outer rotor  622  is driven with a rotary shaft input, and only the convex trailing contact surfaces  678  of the inner rotor  624  contact the flat (or substantially flat) leading contact surfaces of the outer rotor “cylinder” walls. The leading surface  680  of each inner rotor foot does not seal and can be any shape as long as it prevents the rotors from locking up when the pump is freespinning or backturning. 
         [0287]    Benefits of this design include the ability of the inner rotor to rotationally “retreat” (as opposed to the more commonly used term “advance”) in relation to the outer rotor  622  as the inner rotor  624  and/or outer rotor contact surfaces wear. This will, in effect, allow the pump to “wear in” for a period of time rather than wear out. 
         [0288]    Other advantages of driving the outer rotor  622  include the ability to drive subsequent stages with a drive shaft that extends from both ends of one or more outer rotors  622   f  to drive multiple similarly constructed outer rotors. A coaxial stator shaft  694  through the center of the drive shaft would be supported (at the opposite end from the drive shaft input) to the pump casing and would prevent the inner rotor housings from spinning 
         [0289]    As Ice Pump 
         [0290]    In one configuration of the pump, it is designed to handle the admission and pumping of breakable solids such as but not limited to methane hydrate ice crystals. It does this with a combination of features such as sharp leading edges on spinning components and sharp trailing edges on stationary components which will slice the ice as it flows into and through the pump. It is also designed to minimized areas where ice could become wedged and restrict the flow by using increasing cross sections along the flow path. 
         [0291]    As Hydraulic Motor 
         [0292]    By providing fluid pressure to the outlet port of the pump configuration described above and shown in the drawings, the device can also be used in reverse rotation as a hydraulic motor. In this case, the leading convex edges of the inner rotor feet contact the flat or substantially flat trailing surface of the outer rotor  622  which drives the output shaft. 
         [0293]    As Multi Phase Pump 
         [0294]    The pump is ideally suited to pump gases entrapped in a compressible fluid as follows: Gas bubbles that enter the pump will be centrifuged to the innermost area of each outer rotor cylinder chamber. When the inner rotor foot rapidly enters the chamber in the discharge port zone, it will create an acceleration force on the fluid which is in the opposite direction of the centrifugal force on the fluid up to that point. This is expected to cause the higher density fluid to swap positions with at least some of the entrained gas, effectively pushing a bubble of gas out ahead of the fluid as it exits the chamber. In a gas compatible design, the rotational axis is preferably (but not necessarily) vertical and the inner rotor  624  has a flow relief (which exists between the trailing convex contact surfaces  678  of each subsequent inner rotor foot) only on the bottom of the inner rotor  624  so gravity can bias the gas to the top of the chamber as it moves from the input to the output area of the pump. The top sealing surface of the inner rotor  624  is therefore more adequately sealed against gas leakage and is believed to be capable of pushing at least part of the entrained gas out of each chamber. 
         [0295]    In the case of entrained gas, it may be preferable to not push all of the gas out of the chamber at once. This will reduce torque and pressure variations for longer service life. 
         [0296]    In the case of entrained gas, it may be preferable to not push all of the gas out of the chamber at once. This will reduce torque and pressure variations for smoother operation and longer service life. 
         [0297]    The pump is also ideally suited to pump grit such as sand. In this case, the port leading up to a pumping stage is preferably curved along an arced or helical path to centrifuge the heavier sand to the outer surface of the flow path. The will bias the sand away from the intake rotor sliding interaction. The sand then travels around the outer perimeter of the casing and cylinder volume to the discharge port  670  where centripetal force ejects and biases it away from the rotor sliding interaction. 
         [0298]    The multiple seal of the cylinder wall outer surfaces and casing wall inner surface allows the perimeter area (where the sand will be sliding) to have a larger gap clearance while still preventing high leakage rates. 
         [0299]    Many other configurations of the pump described here are possible and conceived by the inventor. Various features and advantages of the pump design are shown in the figures as described below. 
         [0300]      FIG. 27  shows metal inserts  674  in plastic prototype casing are sharp on trailing edges to slice entrained ice. Arrow A shows the rotational direction of rotors when operated as a pump. As a hydraulic motor, the rotation would be in the opposite direction. 
         [0301]    In  FIG. 28  inner crescent  676  is held from rotating by shaft and provides bearing position for inner rotor  624 . 
         [0302]    In  FIG. 29  a relief cut on inner rotor  624  allows leading surface  680  of inner rotor  624  to remain unsealed. 
         [0303]    In  FIG. 30  the inner crescent  676  is held from rotating by shaft and provides bearing position for inner rotor  624 . Trailing surface  678  of driven inner rotor  624  seals against leading flat surface of driving outer rotor  622 . Leading edges  682  of outer rotor  622  are sharp to break/slice/crush ice that enters the pump. Convex leading surface  680  of inner rotor foot does not seal against trailing surface of outer rotor cylinder wall. Sealed housing section  684  between intake and discharge. Extra material  686  on trailing (contact) surface  678  of inner rotor  624  maintains seal integrity as it wears. 
         [0304]    As shown in  FIG. 31 , entrained gas  688  is centrifuged toward inside of outer rotor cylinders. When an inner rotor foot enters the chamber, the acceleration on the fluid is in the opposite direction and all or part of the lighter gas is pushed out of the chamber first. Arrow B shows the direction of rotation of outer rotor  622 . 
         [0305]    In  FIG. 32 , arrows C show the path of denser particles that enter the pump at preferably helical intake  690  on a helical path and are based away from the inner rotor  624  sliding interface by centripedal force. 
         [0306]    In  FIG. 33  the casing is not shown. Drive torque from the motor or shaft is provided to outer rotor member  692  which rotates and transmits torque to outer rotor of next stage Inner coaxial shaft  694  is secured to casing at opposite end from drive input and prevents inner members (which position inner rotors) from turning. 
         [0307]    Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims. 
         [0308]    In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.