Abstract:
A family of sliding vane rotary power devices provides an internal combustion engine, a pump, a compressor, a fluid-driven motor, an expander device, a fluid-driven pump, a compressor or a throttling device. All of these devices have a rotor assembly with a number of vanes equally spaced about the rotor dividing the rotor chamber into discrete cavities. As the rotor turns, the vanes follow the wall contour of the rotor chamber so that the cavities rotate with the rotor and expand and contract as the rotor turns. Various combinations of smooth wall contours and rotational arrangements are provided in different devices in order to cause an appropriate number of expansions and contractions of a cavity during the course of a rotation. Various devices in the family of devices differ both in the shape of the rotor chamber and in the configuration of an internal stator member about which the rotor assembly turns.

Description:
FIELD OF THE INVENTION 
     The invention relates to sliding vane rotary power devices, and more particularly to internal combustion engines, pumps, compressors, fluid-driven motors, expander devices, fluid-driven pumps and compressors or throttling devices, where various ones of those devices differ from others by a simple modification of a central stator member. 
     BACKGROUND OF THE INVENTION 
     Rotary power device of the radial vane type are characterized in having a rotor assembly comprising a number of vanes spaced about the rotor and dividing the rotor chamber into discrete cavities. As the rotor turns, the vanes follow the wall contour of the rotor chamber and thereby provide cavities that rotate with the rotor. 
     Sliding vane rotary devices generally comprise straight vanes slidably received within respective slots radially formed in a rotor. As the rotor spins, vanes are driven outward by centrifugal forces to an extent constrained by the wall contour, so as to execute radially reciprocating motion as the rotor spins. In an effort to increase the outward centrifugal force, a variety of sliding rotary devices have been developed. One class of devices uses a biasing spring disposed at the base of each vane. Another class uses a pair of controlling sidewall cam grooves engaged by sub-shafts fixed to lower side portions of a vane. Still another class uses a transfer passage connecting a pressurized fluid to the base of the vanes. Problems generally encountered by such devices include fluid slip, leakage, complexity associated of the disposition of intake and discharge, and lack of an ability to functionally modify the device to operate as either a pump or an IC engine. Examples of rotary devices of the above type can be found in United States patent such as U.S. Pat. No. 6,030,195 to Pingston, U.S. Pat. No. 4,355,965 to Lowther, U.S. Pat. No. 5,415,141 to McCann, U.S. Pat. No. 4,353,337 to Rosaen, and U.S. Pat. No. 4,018,191 to Lloyd. 
     SUMMARY OF THE INVENTION 
     This invention relates to a rotary power device of the radial vane type characterized in having a rotor assembly comprising a number of vanes equally spaced about the rotor and dividing the rotor chamber into discrete cavities. As the rotor turns, these vanes follow the wall contour of the rotor chamber and thereby provide cavities that rotate with the rotor and that expand and contract as the rotor turns. Various combinations of smooth wall contours and rotational arrangements are provided in different embodiments of the invention in order to cause an appropriate number of expansions and contractions of a cavity during the course of a rotation. In embodiments calling for a single expansion and a single contraction, a substantially circular rotor chamber may be used in combination with an eccentric shaft. In embodiments calling for two or more cycles of expansion and contraction, a rotor chamber having the appropriate number of lobes may be used in combination with a rotor turning about an axis through a center of the rotor chamber. 
     There are several preferred inventive combinations of rotor chamber shape and rotational arrangements for the rotor. Some of these are: 
     A preferred two-cycle engine having a rotor chamber in which the wall contour forms a substantially circular wall eccentrically enclosing the rotor and forming two symmetrical halves of expanding and contracting cavities. In operation as a two-cycle engine, each cavity executes compression, power, and intake and exhaust scavenging processes during the course of each rotation of the rotor. 
     A preferred rotary single-action pump having a rotor eccentrically disposed in a substantially circular rotor chamber so that the cavities expand and contract once during each rotation of the rotor assembly. 
     A preferred four-cycle engine having a rotor chamber comprising an oval-shaped wall. The rotor chamber has a center coinciding with a shaft axis and forming four quadrants. Two diametrically opposed quadrants provide expanding cavities that are alternated by another two quadrants of contracting cavities. As a cavity moves through the four quadrant ranges it executes intake, compression, power and exhaust processes. 
     A preferred double-action pump having a rotor concentrically disposed with respect to an elliptical chamber. In a double-action pump the cavities expand and contract twice during each rotation of the rotor assembly. 
     The present invention comprises a rotary power device that can be configured, among other things, to serve as either a two-cycle or a four-cycle internal combustion engine, or as a single-action or double-action pump by replacement of a stationary central member. Preferred embodiments of the invention comprise a generally toroidal rotor assembly fixedly secured to an end shaft and rotatably carried at one end of an external stator housing. The preferred rotor comprises a central bore communicating with a plurality of radial compartments that are open to a peripheral surface of the rotor and that will be hereinafter referred to as open-ended compartments. 
     The preferred rotor block also comprises a plurality of radial slots disposed in alternating relation with the radial compartments. Each radial slot is connected to an adjacent radial compartment by a transfer passage connecting the base of the slot with the compartment. An external stator portion of the device defines an internal volume that, when combined with the stationary central stator portion, defines a chamber for receiving the rotor. The preferred rotor chamber, when viewed in a medial section perpendicular to a rotational axis of the device, may appear as an ellipse or as a circle. Moreover, the rotor chamber may be concentric or eccentric with respect to the rotational axis of the device. Furthermore, preferred devices comprise an internal stator fixedly secured to the external stator and rotatably enclosed, with clearance, within the central bore of the rotor. The internal stator comprises channels connected to ports communicating with inner openings of the rotor compartments. As the rotor spins, a cavity formed between two adjacent vanes enclosing a radial compartment intermittently communicates with the ports in the internal stator so as to perform intake, compression, and power and exhaust functions. In addition to embodiments serving as internal combustion engines, the rotary device of the invention can function as pump or compressor by replacing the internal stator with one having the appropriate port and channel configuration. 
     One object of some embodiments of the invention is to provide an improved radial vane rotary power device that is light in weight, small in size and that has the minimum number of parts. 
     Another object of some embodiments of the invention is to provide a rotary power device that can be easily converted to other type of rotary power device such as, a pump, a compressor, or a work exchanger device by a simple modification or replacement of a central stationary member. 
     Another object of some embodiments of the invention is to provide a rotary power device that closely approximates continuous intake, compression, combustion and discharge processes. 
     Another object of some embodiments of the invention is to provide a rotary power device characterized by reduced noise and vibration. 
     Another object of some embodiments of the invention is to provide a rotary power device with minimum fluid slip and leakage. 
     These and other objects and advantages of the present invention will be apparent from the following detailed description and the appended claims. Although it is believed that the foregoing recital of features and advantages may be of use to one who is skilled in the art and who wishes to learn how to practice the invention, it will be recognized that the foregoing recital is not intended to list all of the features and advantages. Moreover, it may be noted that various embodiments of the invention may provide various combinations of the hereinbefore recited features and advantages of the invention, and that less than all of the recited features and advantages may be provided by some embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded isometric view of a rotary power device of the invention having a portion of a housing cut away for purposes of illustration. 
     FIG. 2 is an isometric view of a rotary power device of the invention in which an external stator portion is partially cut away for purposes of illustration. 
     FIG. 2 a  is an alternative isometric view of the rotary power device of FIG. 2 in which the ignition means is disposed in the external stator portion. 
     FIG. 2 b  is an alternative isometric view of the rotary power device of FIG. 2 in which the ignition means and exhaust passageway are disposed in the external stator portion. 
     FIG. 3 is an isometric view of a rotor having a portion cut away for purposes of illustration. 
     FIG. 4 is a side elevation view of the rotary power device of FIG.  2 . 
     FIG. 4 a  is a side elevation view of the rotary power device of FIG. 2 a.    
     FIG. 4 b  is a side elevation view of the rotary power device of FIG. 2 b.    
     FIG. 5 is a cross-sectional view taken along  5 — 5  of FIG.  4 . 
     FIG. 5 a  is a cross-sectional view taken along  5   a — 5   a  of FIG. 4 a.    
     FIG. 5 b  is a cross-sectional view taken along  5   b — 5   b  of FIG. 4 b.    
     FIG. 6 is an end view of the rotary power device of FIG.  2 . 
     FIG. 7 is a cross-sectional view taken along  7 — 7  of FIG.  6 . 
     FIG. 8 is an isometric view of an alternate central internal stator for a power device of the present invention. 
     FIG. 8 a  is an isometric view of another alternate central internal stator for a power device of the present invention. 
     FIG. 9 is a side view of the rotary power device of FIG. 1 employing the alternate internal stator of FIG.  8 . 
     FIG. 9 a  is a side view of the rotary power device of FIG. 1 employing the alternate internal stator of FIG. 8 a.    
     FIG. 10 is a cross-sectional view taken along line  10 — 10  of FIG. 9 of a rotary power device of the invention that uses the alternate central stator of FIG.  8  and that is capable functioning as a double-action pump, a double-action compressor, a double-action expander or a fluid-driven motor. 
     FIG. 10 a  is a cross-sectional view taken along line  10   a — 10   a  of FIG. 9 a  of a rotary power device of the invention that uses the alternate central stator of FIG. 8 a  and that is capable of functioning as a double-action pump, a double-action compressor, a double-action expander or a fluid-driven motor. 
     FIG. 11 is an isometric view of another alternate internal stator for a two-cycle power device of FIG.  1 . 
     FIG. 11 a  is an isometric view of yet another alternate internal stator for a two-cycle power device of FIG.  1 . 
     FIG. 11 b  is an isometric view of still another alternate internal stator for a two-cycle power device of FIG.  1 . 
     FIG. 11 c  is an alternative end plate having an eccentric cam grove corresponding to a two-cycle power device. 
     FIG. 12 is a side view of the rotary power device of FIG. 1 employing the alternate internal stator of FIG.  11 . 
     FIG. 13 is a cross-sectional view taken along line  13 — 13  of FIG. 12 of a rotary power device using the central stator of FIG.  11  and functioning as two-cycle internal combustion engine. 
     FIG. 14 is an end view of the rotary power device of FIG. 1 employing the alternate internal stator of FIG.  11 . 
     FIG. 14 a  is an end view of the rotary power device of FIG. 1 employing the alternate internal stator of FIG. 11 a.    
     FIG. 14 b  is an end view of the rotary power device of FIG. 1 employing the alternate internal stator of FIG. 11 b.    
     FIG. 15 is a sectional view taken along  15 — 15  of FIG. 14 
     FIG. 15 a  is a sectional view taken along  15   a — 15   a  of FIG. 14 a    
     FIG. 15 b  is a sectional view taken along  15   b — 15   b  of FIG. 14 b    
     FIG. 16 is an isometric view of an alternate internal stator of the present invention. 
     FIG. 16 a  is an isometric view of another alternate internal stator of the present invention. 
     FIG. 17 is a side view of the rotary power device of FIG. 1 employing the alternate internal stator of FIG.  16 . 
     FIG. 17 a  is a side view of the rotary power device of FIG. 1 employing the alternate internal stator of FIG. 16 a.    
     FIG. 18 is a cross-sectional view taken along line  18 — 18  of FIG. 17 of the device of FIG. 1 employing the alternate internal stator of FIG.  16  and functioning as a single-action pump, compressor, expander or fluid-driven motor. 
     FIG. 18 a  is a cross-sectional view taken along line  18   a — 18   a  of FIG. 17 a  of the device of FIG. 1 employing the alternate internal stator of FIG. 16 a  and functioning as a single-action pump, compressor, expander or fluid-driven motor. 
     FIG. 19 is an isometric view of another alternative internal stator of the present invention. 
     FIG. 19 a  is an isometric view of still another alternative internal stator of the present invention. 
     FIG. 20 is a side view of the rotary power device of FIG. 1 employing the alternative internal stator of FIG.  19 . 
     FIG. 20 a  is a side view of the rotary power device of FIG. 1 employing the alternative internal stator of FIG. 19 a.    
     FIG. 21 is a cross-sectional view taken along line  21 — 21  of FIG. 20 of a rotary power device employing the alternate stator of FIG. 19, the device functioning as fluid-driven pump. 
     FIG. 21 a  is a cross-sectional view taken along line  21   a — 21   a  of FIG. 20 a  of a rotary power device employing the alternate stator of FIG. 19 a , the device functioning as fluid-driven pump. 
    
    
     DETAILED DESCRIPTION 
     In FIGS. 1-7 of the drawing, the principles of this invention are illustrated through its application as a four-cycle internal combustion engine. It will be understood, however, that these principles can be successfully employed to yield other devices such as pumps, compressors, fluid driven motors, or fluid driven pumps or compressors through a simple modification or replacement of either or both of the internal and external stator portions. 
     The preferred rotary power device  10  comprises an external stator portion comprising a middle portion preferably formed from mating half portions  12   a ,  12   b . The preferred external stator portion also comprises front  14   a  and back  14   b  end plate portions. The two middle half portions are preferably mated by means of alignment rods  68  inserted through holes  74 . The end plate portions are preferably fixed to the middle half portions by fixture means such as bolts  70  inserted through aligned holes  72  and  73 . The front end plate  14   a  preferably comprises an opening  66   a  for rotatably mounting a rotor  20  and an end shaft  18  by means of a suitable bearing  26 . A preferred back end plate  14   b  includes an opening  66   b  for fixedly mounting an internal stator potion  40  by known fixturing means (not shown). The inner face of the front and back end plates may further comprise respective cam grooves  32   a  and  32   b.    
     A medial cross-section of the external stator, taken transverse to an axis of rotation  22  of the device  10  shows that the rotor chamber  23  of a preferred four cycle engine embodiment of the invention (e.g., as depicted in FIG. 5) has an elliptical wall  15  having a central axis coinciding with the axis of rotation  22 . More generally, the shape of the medial cross-section of the rotor chamber  23  is a smooth curve selected so that rotor vanes  34  cooperate with the rotor chamber wall to produce an appropriate number of radially inward and outward reciprocations of the vanes  34  during each rotation of the rotor. In devices analogous to four or more cycle internal combustion engines, this cooperative effect may be obtained by a combination of a lobed chamber wall (where an oval or elliptical shape provides two lobes) and a rotor turning concentrically with respect to the rotor chamber  23 . In two-cycle engines, single-acting pumps and other such analogous devices, subsequent portions of this disclosure will describe rotor chambers that, when viewed in the same section, have a circular inner wall eccentrically disposed with respect to an axis of rotation of a shaft of those devices. 
     For any of the choices of rotor chamber shape defined with respect to a section perpendicular to the axis of rotation, when viewed in a cross-section or cut-away taken parallel to the axis of shaft rotation (e.g., as seen in FIG. 2) the portion of the rotor chamber wall  15  formed by the middle portion of a preferred external stator is seen to have a semi-circular profile, a central point of which traces the ellipse, circle, or other smooth curve when followed along a plane perpendicular to the axis of the shaft. Correspondingly, both an outer edge portion of a vane cooperating with the rotor chamber  23 , and a peripheral portion of a preferred rotor have matching semi-circular profiles. 
     A rotor assembly  20  of the preferred four-cycle engine may be concentrically mounted within the annular rotor chamber  23  defined by the inner wall of the middle portions, the inner wall of the front and back end plates, and the peripheral wall of the central internal stator. A preferred rotor assembly comprises a block  36  fixedly connected to or integrally formed with a central shaft  18  having an axis coincident with the axis of the device  22 . A preferred block includes a peripheral wall portion  37  that is cylindrical in the sense of having a single selected maximum radial extent from the axis of rotation  22  for any choice of angle about the shaft  18 . Moreover, the peripheral portion  37  of the cylindrical block comprises a semi-circular profile when viewed in a cross-section taken in a plane containing the axis of the device, as depicted in FIG.  3 . This semi-circular profile cooperates with the semi-circular profile of the wall  15 , which is the inner wall of the external stator&#39;s middle portion and the outer wall of the rotor chamber  23 . The cylindrical block may further comprise a central bore  42  communicating with a plurality of open-ended radial compartments  44  through respective inner openings  46 . There is also an equal multiplicity of radial slots  38  that are disposed in alternating relation with the radial compartments, where each radial slot communicates at a lower portion with an adjacent radial compartment by means of a respective transfer passage  47 . A multiplicity of vane assemblies  30  is preferably disposed in the rotor chamber  23 , and arranged so that each vane assembly includes a respective vane plate portion  34 , a respective pin  48  fixable to the base of the vane and protruding through a respective rotor cam slot  45 , and a respective cam follower roller  28  rotatably mounted at pin end  48  and engaging a guide cam groove  32   a  and  32   b . As the rotor spins, the vanes reciprocate outward and inward along respective radii where the motion of the vanes is controlled by the side cam or inner wall cam, and the vane tips contact or come close to contacting the inner wall of the middle portion of the external stator. 
     The central internal stator  40 , as shown in FIG.  1  and FIG. 2, comprises a cylindrical portion  52  extending coaxially through the opening  66   b  into engagement with the interior of the rotor  20 , and an end flange portion  54  for fixedly attaching the cylindrical portion  52  to the back end plate  14   b  by suitable fixture means (not shown). Alternatively, the central internal stator  40  may be manufactured as a cylindrical projection from the back end plate. A preferred cylindrical portion  52  is provided with two peripheral cutout openings forming angularly adjacent intake  56  and exhaust  58  ports. Each port opening is defined within an approximate angular extension of 90° and has an angularly varying radial depth profile. These lateral openings respectively communicate with an axial intake channel  62  and an exhaust channel  60  connecting these ports to the exterior. An ignition port  61  is disposed approximately diametrically opposite to the angularly adjacent pair of intake and discharge ports and is connected to an axial ignition channel  64  that is preferably provided with an ignition means such a spark plug  24  or a glow plug, as appropriate. 
     Another embodiment is the four-cycle rotary power device shown in FIG. 2 a  in which the internal stator comprises an intake passageway  62  and an exhaust passageway  60 , but in which the ignition means  24  is disposed in the external stator portion. 
     Still another embodiment of a four-cycle rotary power device is shown in FIG. 2 b  in which the internal stator portion comprises an intake passageway  62 ; but the exhaust passageway  63  and the ignition means  24  are disposed in the external stator portion. In this embodiment the exhaust passageway  63  comprises a groove cut into the inner peripheral wall of the external stator. The groove is defined over a 90° angular displacement and is connected to a discharge port  67 , as shown in FIG. 5 b.    
     In operation as a four-cycle internal combustion engine, a starter motor (not shown) is connected to the shaft  18  to initiate the rotation of the rotor  20  to start the engine. Each cavity is bounded by two adjacent extended vanes and encloses a radial compartment that moves through four phases comprising intake, compression, power and discharge phases, each phase taking place within a 90° angular displacement of the rotor. Step by step operation of the four phase internal combustion is explained with reference to FIG.  5 . For example, consider the movement of a cavity bounded by two adjacent vanes that starts at the top-most position where the volume is minimum, which corresponds to top dead center (TDC) in a conventional reciprocating engine. As the rotor turns, the volume increases gradually and the inlet port  56  of the central stator comes into communication with the intake channel  62  which registers with inner openings  46  of the rotor, so as to perform intake of a fuel/air mixture. This phase terminates at a maximum volume position corresponding to the first bottom dead center (BDC) position in a conventional engine. During the second phase, the cavity volume decreases and the compartment inner opening  46  is blocked by the cylindrical wall portion  52  of the central stator, thereby compressing the charge. This phase terminates at a second minimum volume corresponding to the second (TDC) in a conventional engine. During the third phase, the compressed charge is ignited as the cavity registers with the ignition port  61  comprising ignition means such as a glow plug or spark plug  24 . The ignition means  24  may be disposed in the internal stator as shown in FIG.  4  and FIG. 5 or in the external stator as shown in FIGS. 5 a  and  5   b . Subsequent to ignition, a power phase is initiated in which the volume increases and the compartment inner openings  46  are blocked again by the cylindrical wall portion  52 . The effect of the resultant pressure forces of the expanding gases on the extended vanes provides a larger tangential force on that vane having the larger extended area, which provides the propelling torque, causing the rotation of the rotor. The expansion process continues until the cavity volume reaches a maximum, corresponding to the second (BDC) position in a conventional engine. At the beginning of the fourth phase, blow down of combustion products is followed by an exhaust process as the volume decreases while the inner opening  46  registers with the exhaust port  58 , thus further expelling the combustion products through a channel  60  as shown in FIG. 2, FIG. 2 a . FIG.  5  and FIG. 5 a . Alternatively, the combustion products are expelled through the exhaust passageway  63  in the external stator leading to an exhaust port  67  as the open-ended compartment registers with the passageway, as shown in FIG. 5 b . Thus, as the cavity completes one revolution, it executes one complete four-cycle operation comprising intake, compression, power, and exhaust phases. 
     The rotary power device  10  can be easily converted to serve a different purpose than that of an internal combustion engine by simple replacement of the internal stator  40  with the alternative central stator  40   a  shown in FIG.  8  and FIG. 8 a . A rotary power device employing the alternative central stator  40   a  can function as a double-action compressor, a pump, an expander or as a fluid-driven motor. In the configuration of FIG. 8, the central stator comprises two diagonally disposed intake ports  56   a  and  56   b  alternated by two diagonally disposed exhaust ports  58   a  and  58   b . Each port is formed as a respective cutout in the peripheral wall of the internal stator portion and is defined within a 90° angular extension. The two intake ports are connected to a common intake channel  62 , and the two exhaust ports are connected to a common exhaust channel  60 . One channel may comprises a central channel and the second may comprises an annular channel concentric with the central channel. In another alternative configuration, depicted in FIG. 8 a , the internal stator comprises only two diagonally disposed intake ports  56   a  and  56   b  connected to a common intake passageway  62 ; and the external stator comprises two diagonally disposed discharge passageways  63   a  and  63   b  connected to respective discharge ports  67   a  and  67   b  as shown in FIG. 10 a.    
     When functioning as a pump or compressor, the rotor is made to rotate by coupling the end shaft  18  to a driving means such as a motor. Centrifugal force urges the vanes  34  outward and is assisted by fluid pressure communicated to the base of the vanes through a transfer passage  47 . A sealed cavity is enclosed between two vanes having outer vane tips making contact engagement with the toroidal and side wall of the rotor chamber  23  through spring biased vane tips (not shown) or, alternatively, making a small clearance engagement with the walls for vanes having cam followers engaging end plate cams  32   a  and  32   b . As depicted in FIG.  10  and FIG. 10 a , each cavity is preferably bounded by two vanes and encloses a respective radial compartment that goes through two angular displacements of expanding volume alternated by two angular displacements of contracting volume. During expansion, the inner opening  46  registers with intake ports  56   a  and  56   b , and during contraction the inner opening  46  registers with discharge ports  58   a  and  58   b , or alternatively, with discharge passageways  63   a  and  63   b . Thus, simultaneous diagonally opposed intake and exhaust take place as the rotor rotates. In functioning as a fluid driven motor or expander device, a pressurized fluid communicated through intake channels  62  connected to ports  56   a  and  56   b  provides a net turning force on the differential extended vane area as the cavities expand, thus causing rotation of the rotor. At the same time, the resulting rotation expels the depressurized fluid through discharge ports  58   a  and  58   b  connected to discharge channels  60  or, alternatively, expels the depressurized fluid through discharge passageways  63   a  and  63   b  as the cavities contract in volume. 
     The rotary power device  10  can also be configured as a two-cycle internal combustion engine comprising modifications shown in FIG.  11  through FIG.  15 . These modifications comprise the use of an eccentric rotor chamber profile, eccentric end cams and a modified central internal stator. In these embodiments the wall  15  of the middle portion of the external stator, when viewed in a section taken perpendicular to the shaft axis (see FIG. 13) is circular, with a center that is displaced from the axis of rotation of the shaft. The central internal stator  40   b  for the two-cycle engine comprises axially spaced apart intake port  56  and exhaust port  58 , each connected to a respective intake channel  62  and exhaust channel  60 . The exhaust port  58  extends over a larger angular range than does the intake port  56 , and the intake port is defined within an angular displacement overlapping the exhaust  58  in order to allow for intake-exhaust scavenging. An injection port  61  is disposed approximately diametrically opposite to the intake and exhausts port and is connected to an injection channel  65 . Another embodiment of the internal stator  40   b , shown in FIG. 11 a , comprises only intake  62  and exhaust  60  passageways, while the ignition port  61  is included in the external stator portion as shown in FIG. 15 a . Still another embodiment of the internal stator  40   b , depicted in FIG. 11 b , comprises only intake passageway  62  connected to a respective peripheral intake port  56 ; while the external stator portion comprises an exhaust passageway  69  and an ignition port  61 . 
     The operation of the two-cycle engine may be explained with reference to FIG.  13 . Because of the eccentricity of the rotor chamber  23 , each cavity enclosed between two vanes goes through a range of contracting volume and an equal range of expanding volume. A significant portion of the contracting volume range comprises the compression phase. Within a small range surrounding the cavity at minimum volume, ignition of the charge takes place at a port  61  by either injection of fuel in compressed air or by a glow plug or spark plug igniting a fuel/air mixture charge. Following the ignition process, the power expansion takes place for a significant portion of the expanding cavity range during which the inner openings  46  are blocked by the peripheral wall  52  of the central stator. The expansion process terminates with exhaust blow down as the open-ended compartment registers, through its inner opening  46 , with an exhaust port  58  in the internal stator or, alternatively, as the open-ended compartment registers through its outer end opening with exhaust passageway  69  in the external stator. This is followed by intake-exhaust scavenging taking place within an angular range surrounding the cavity at maximum volume so that the intake  56  overlaps with either of the exhaust ports  58 ,  69 . 
     The two-cycle internal combustion engine described above can be transformed into a single-action pump, compressor, expander device or fluid-driven motor by replacing the internal stator  40   b  with other internal stators  40   c  shown in FIGS. 16,  16   a . The alternative internal stator  40   c  as shown in FIG. 16 comprises an intake port  56  and an angularly adjacent discharge port  58 , where each port preferably comprises a 180 degree angular cutout in the peripheral wall of the internal stator connected to respective intake  62  and exhaust channels  60 . Alternatively, the internal stator  40   c , as shown in FIG. 16 a , comprises only an intake passageway  62  connected to a respective peripheral intake port  56   a , defined over 180 degree of angular displacement; and the external stator portion comprises a discharge passageway  63  connected to a respective discharge port  67 , as shown in FIG. 18 b . The operation of the pump may be explained with reference to FIG.  18  and FIG. 18 a  In operation, the shaft is rotated by an external rotating means, such as a motor (not shown). Various combinations of the effects of centrifugal force, cam action, fluid pressure transmitted through transfer passage  47 , and a biased spring action (not shown), causes the vane or blades  34  to make a contacting or a small clearance engagement with the toroidal peripheral wall of the chamber as the rotor rotates. A cavity enclosed by two vanes goes through a 180° range of expansion during which the inner opening  46  of each radial compartment  44  communicates with the intake port  56 , so as to perform an intake phase. This is followed by a 180° range of contraction during which the open-ended compartment, through its inner opening  46 , registers with the discharge port  58  in the internal stator. Alternatively, as shown in FIG. 18 a , the compartment may register through its outer opening with the discharge passageway  63  in the external stator portion, thus performing a discharge phase. 
     Still other embodiments of the invention provide a rotary power device operating as a fluid-driven pump or as an energy recovery device. Applications for this sort of device include a turbocharger for internal combustion engines and an energy recovery device useful in reverse osmosis plants. Examples of such apparatus are depicted in FIG.  19  through FIG. 21 a  and employ an external stator having an elliptical working chamber as has been previously described with respect to FIG.  1 . In these embodiments the internal central stator  40  of the rotary power device shown in FIG. 1 is replaced with another internal stator  40   d  as shown in FIG. 19 or, alternatively, as shown in FIG. 19 a . As shown in FIG. 19, the modified internal stator comprises four angularly adjacent ports comprising two diagonally opposed intake ports  56   a ,  56   b  connected to respective intake channels  62   a ,  62   b , and another two diagonally opposed discharge ports  58   a ,  58   b  connected to respective discharge channels  60   a ,  60   b . Alternatively, as shown in FIG. 19 a , the internal stator portion may include only two diagonal intake ports  56   a ,  56   b  connected to respective intake channels  62   a ,  62   b ; while the external stator portion includes two diametrically disposed discharge passageways  63   a ,  63   b  connected to respective discharge ports  67   a ,  67   b  as shown in FIG. 21 a  In operation as fluid driven pump, a fluid I of higher pressure is communicated to one intake channel, for example  62   a , and a second fluid II of lower pressure is communicated to a second intake channel  62   b . The effect of net pressure forces on vanes caused by the high-pressure fluid during the intake phase is to cause rotation of the rotor and the pressurization of the lower pressure fluid. Thus, a pressure exchange takes place whereby a higher-pressure fluid experiences a pressure loss as it discharges through the exhaust channel  60   b  or alternatively through discharge passageway  63   b ; and the lower pressure fluid experiences an increase in pressure as it discharges through the channel  60   a  or alternatively, through discharge passageway  63   a.    
     As will be understood by those skilled in the art, various embodiments other than those described in detail in the specification are possible without departing from the scope of the invention will occur to those skilled in the art. It is, therefore, to be understood that the invention is to be limited only by the appended claims.