Abstract:
A rotary pump device includes a stator chamber with a cylindrical inner wall having intake and exhaust ports therein, and a two-part, expanding rotor eccentrically mounted for rotation within the chamber. The rotor comprises two crescentoid bodies with end surfaces in sliding, mating contact. A spring rod is placed between the inner rotor body surfaces to maintain rotor contact points in continuous wiping contact with the chamber wall. A full intake/exhaust cycle occurs every 180° of rotor travel.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention is in the field of pumps, and more particularly rotary pumps of the type having a stator chamber with inlet and outlet ports. 
       BACKGROUND OF THE INVENTION AND DESCRIPTION OF RELATED ART 
       [0002]    The term “pump” is used herein to refer to a device comprising a stator chamber or housing and a rotor that rotates within the chamber to cause sequential intake, compression, and exhaust of a fluid medium such as a gas, a liquid, or a combination thereof. The term, therefore, comprehends not only devices that cause fluid movement but also devices that compress or pressurize fluids with or without ignition and combustion. Further, the term “pump” embraces a reverse operation in which fluid drives a rotor rather than the rotor driving the fluid; i.e., in reverse operation every pump is effectively a motor. 
         [0003]    One example of a rotary pump is the well-known Wankel engine that uses an ellipsoid stator chamber and a triangular rotor with seals at the corners. 
         [0004]    Another example of a rotary pump is shown in U.S. Pat. No. 4,507,067 to Hansen. The pump in the Hansen patent comprises an elliptical, non-expanding rotor within an elliptical chamber with co-located geometric and rotational centers. The device is characterized by complexity in the number of radially sliding seals required. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present invention comprises a pump structure having a stator chamber with a substantially continuous inner wall with intake and exhaust ports formed therein. The pump further comprises an eccentrically mounted, cyclically expanding, two-part rotor mounted within the chamber such that as the rotor rotates, the rotor parts shift in position to maintain a wiping contact between the trailing edges of the rotor parts and the inner wall of the chamber to effect intake, compression, and exhaust functions with each 180° of rotor movement. 
         [0006]    In an illustrative embodiment, the chamber wall is cylindrical and the rotor comprises a pair of crescentoid rotor bodies (each being less than semi-cylindrical, or covering less than 180°, in outer circumference; but of essentially constant radius, so as to form a body with an elliptical outer surface when the bodies are joined) with outer surface contours conforming to the inner surface contours of the chamber wall, so that within each 180° of rotation one rotor body lies fully and conformingly against the chamber wall while the other rotor body is maximally separated or spaced from the wall, the intake port is full open, and the exhaust port is full closed. 
         [0007]    In the illustrative embodiment, the crescentoid rotor bodies have end surfaces that abut and slide over one another to effect rotor expansion and contraction. A spring-biased pin or rod interconnects the inner diameters of the rotor bodies to urge them outwardly into continuous wiping contact with the chamber wall. 
         [0008]    In accordance with a preferred embodiment hereafter described, the trailing rotor body edges that contact the stator wall are chamfered to reduce initial wear. The intake and exhaust ports are opposite one another [and offset] along a chord that intersects the rotor axis. As will be understood from the following specification, the pump of the present invention can be scaled to any desired capacity and constructed using any material or combination of materials including hard, dense plastics such as HDPE, ceramics, cermets, and/or metals. 
         [0009]    These and other features and advantages of the invention will become apparent from the detailed description below, in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a plan view of a pump embodying the invention with the rotor in an offset position that opens an intake port and closes an exhaust port. 
           [0011]      FIG. 2  is another plan view of the pump with the rotor displaced approximately 90° from the position shown in  FIG. 1 , and in a fully expanded condition. 
           [0012]      FIG. 3  is a side view, partly in section, of a detail of the  FIG. 1  pump. 
           [0013]      FIGS. 4A-4F  make up a schematic, sequential showing of rotor position and fluid flow over approximately 180° of rotation. 
           [0014]      FIG. 5  is an isometric view of one rotor body with a preferred edge structure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Referring to  FIGS. 1 ,  3  and  5 , there is shown a pump  10  comprising a stator  12  defining a cylindrical chamber having an inner wall  14  interrupted only by intake (inlet) and exhaust (outlet) ports  16  and  18 , respectively. The stator chamber has a floor  13  and it will be understood that a cover plate or other structure (not shown) closes the chamber when all of the parts described in the following are installed. The chamber is cylindrical as defined by the inner wall, and has a geometric center at  20 . 
         [0016]    A rotor  22  comprises substantially identical crescentoid bodies  24  and  26  mounted end-to-end for rotation with an input structure  28 . Each rotor body has an outer surface  42  with a diameter equal to the diameter of the wall  14  and an inner surface  44  of a smaller diameter such that, when the rotor  22  is in the expanded condition shown in  FIG. 2 , the inner surfaces  44  form a circle. Each rotor part also has end surfaces shown at  48  and  50  in  FIG. 5  and these end surfaces slidingly abut one another when the rotor  22  is installed in the chamber. 
         [0017]    The crescentoid rotor bodies  24 ,  26  are identical but asymmetrically installed; i.e., the end surfaces  48 ,  50  differ in depth and area and the bodies are arranged such that the larger end surface (e.g.  48 ) of one body abuts the smaller end surface (e.g.  50 ) of the other body. With rotation in a clockwise direction when viewing the pump  10  as in  FIG. 2 , the trailing edges of the larger ends are the contact or wiping surfaces and are preferably chamfered as shown at  46  in  FIG. 5  to pre-wear the rotor bodies and improve seal function. 
         [0018]    Blind holes  38  and  40  are formed in the inner surfaces  44  of the rotor bodies to receive an end of a connecting spring pin  32  shown in detail in  FIG. 3 . The connecting pin  32  comprises a hollow metal (e.g. steel or brass) rod  33 , a pin  36  which fits slidingly into the rod  33 , and a compression spring  34  which is attached to the pin  36  at one end and rests against the end shoulder  33 a of the rod  33 . Inserted into the blind holes  38 ,  40 , pin  32  resiliently urges the trailing portions of the rotor bodies into continuous contact with wall  14 . The spring pin  32  is fully compressed in  FIG. 1  as the rotor bottoms out against the base of the chamber, forcing the rotor bodies inwardly, and is fully expanded in  FIG. 2 . 
         [0019]    Rotor drive comes from driven post or shaft  28 , the center of which defines the rotor axis of rotation. As can be seen in  FIGS. 1 and 2 , the axis of rotation is displaced from the geometric stator center  20 . The rotor drive post  28  is connected to rotor body  24  by means of a drive pin  30  passing in sliding fashion through a bore in post  28  and connected at both ends to rotor body  24  in holes  49 . (Pin  30  might alternately be slidingly secured at one end in the bore or a blind hole in post  28  and connected at the other end to rotor body  24 , with sufficient length to maintain the drive connection throughout the pump cycle.) 
         [0020]    Referring now to  FIGS. 4A-4F , a description of operation will be given.  FIGS. 4A-4F  represent progressively different degrees of rotor position over about 180° (degrees) of travel in a clockwise direction.  FIG. 4C  corresponds in rotor position to  FIG. 2  and  FIG. 4F  corresponds in rotor position to  FIG. 1 . 
         [0021]    In  FIG. 4A , the rotor  22  is partly expanded and is positioned such that both intake and exhaust ports  16 ,  18  are open. Fluid begins to flow into the intake port  16  and the compression of the fluid in the volume above and to the right of the rotor is just beginning. In  FIGS. 4B and 4C , the intake volume to the left of the rotor  22  continues to expand, creating suction that pulls fluid into the pump while the right hand volume continues to grow smaller. In  FIGS. 4D-4F  the intake volume grows to maximum and the exhaust volume quickly goes to zero, expelling all fluid through port  16 . The cycle repeats every 180° of rotation. 
         [0022]    Pump  10  can also be driven in reverse operation as a motor, in which fluid entering the stator chamber drives the rotor  22  rather than the rotor pumping the fluid through the chamber. Fluid pumped into exhaust port  18  will thus rotate the rotor  22  in reverse, i.e. counterclockwise in the Figures, until exiting the chamber through inlet  16  in a reverse of the 180° cycle described in reference to  FIGS. 4A-4F . Rotor  22  driven by the fluid entering exhaust port  18  accordingly rotates post  28  via pin  30  to effect work at some point outside the pump  10 . 
         [0023]    It may also be possible to make the stator&#39;s inner wall  14  circular over only a portion of its circumference, for example by making the “base” of the wall  14  where the rotor bodies  24 ,  26  bottom out ( FIGS. 1 and 4F ) of constant and thus circular diameter, and by making some portion of the remainder of wall  14  a non-circular shape, such as egg-shaped. This would reduce the amount of rotor travel, and allow the trailing edges of the rotor bodies to maintain a wiping seal with inner wall  14  with less shifting movement. 
         [0024]    It will finally be understood that the disclosed embodiments represent presently preferred forms of the invention, but are intended to be explanatory rather than limiting of the invention. Reasonable variation and modification of the invention as disclosed in the foregoing disclosure and drawings are possible without departing from the scope of the invention. The scope of the invention is defined by the following claims.