Patent Publication Number: US-2011048370-A1

Title: Revolving piston internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims the benefit of U.S. Provisional Application 11/856,263 filed on Sep. 17, 2007. application Ser. No. 11/856,263 is a Continuation-in-part of application Ser. No. 10/545,251 filed on Aug. 10, 2005, which is a U.S. National Phase of PCT Application No. PCT/IN02/00025 filed Feb. 13, 2003 and entitled “Revolving Piston Internal Combustion Engine”. 
    
    
     FIELD OF THE INVENTION 
     The present invention discloses a revolving piston engine incorporating dual revolving pistons for improving fuel efficiency, increasing power output, easy sealing, easy cooling and reduced vibration. One or more of revolving pistons, each consisting of one piston and one cylinder head, revolve within a ring cylinder, around a common axis in a same direction, but with different velocities. A revolving piston compressor is also disclosed, incorporating appropriately designed and relocated ports/valves for both of associated intake and outlet components. 
     BACKGROUND OF THE INVENTION 
     Conventional internal combustion engines are well known and widely used in day-to-day life, these typically consisting of a cylinder, a crank, a connecting rod and a piston. These reciprocating piston engines are further designed with different capacities and for various applications using different types of fuels. 
     In an attempt to reduce “work loss” (this generally being defined to encompass any component of energy associated with the combustion cycle in the piston and valve arrangement and which is dissipated into some other form outside of output energy delivered to the vehicle crank) associated with such reciprocating piston engines, different types of engines have been produced, both with and without a reciprocating piston. Most notable among these are rotary engines. 
     One such well know effort is the Wankel engine, and which was designed with a rotary piston, that rotates continuously in one direction, thus reducing the losses which otherwise would have caused by the reciprocating motion of the piston in a conventional reciprocating piston internal combustion engine. In the Wankel engine, the four strokes of a typical Otto cycle occur in the space between a rotor, which is roughly triangular, and the inside of an associated housing. In the basic single-rotor Wankel engine, the oval-like housing surrounds a three-sided rotor. A central drive shaft, also called an eccentric shaft, passes through a center of the rotor, and is supported by bearings. 
     In operation, the rotor both rotates around an offset lobe (or crank) located on the eccentric shaft, thus creating orbital revolutions around the central shaft. Associated seals located at the corners of the rotor seal against the periphery of the housing, thus dividing it into three continuously moving combustion chambers. Fixed gears mounted on each side of the housing engage with ring gears attached to the rotor, and to ensure the proper orientation as the rotor moves. 
     During concurrent rotation and orbital revolution, each side of the rotor alternates in its position (i.e. closer and farther) relative to the wall of the housing, thus compressing and expanding the combustion chamber in a fashion similar to the strokes of a piston in a reciprocating engine, and with the power vector of the combustion stage traveling through the center of the offset lobe. 
     In contrast to a standard four stroke piston engine producing one combustion stroke per cylinder for every two rotations of the crankshaft (that is, one half power stroke per crankshaft rotation per cylinder), each combustion chamber in the Wankel generates one combustion stroke per each driveshaft rotation, i.e. one power stroke per rotor orbital revolution and three power strokes per rotor rotation. Accordingly, the power output of the Wankel engine is generally higher than that of a four-stroke piston engine of similar physical dimension and size. 
     Wankel engines have several major advantages over reciprocating piston designs, in addition to having higher output for similar displacement and physical size, most notably including being considerably simpler with far fewer moving parts. The elimination of these parts not only makes a Wankel engine much lighter (typically half that of a conventional engine of equivalent power), but it also completely eliminates the reciprocating mass of a piston engine, with its internal strain and inherent vibration due to repeated acceleration and deceleration, thereby producing not only a smoother flow of power but also the ability to produce more power by running at higher revolutions per minute (rpm). 
     Corresponding disadvantages of Wankel style engines include, and in comparison to standard four cycle piston engines, the time available for fuel to be injected into the Wankel engine being significantly shorter, and again due to the way the three chambers rotate. Also, the fuel-air mixture cannot be pre-stored, as there is no intake valve and which means that, in order to obtain acceptable performance out of a Wankel engine, more complicated fuel injection technologies are required than for regular four-stroke engines. Also, the difference in intake times causes Wankel engines to be more susceptible to pressure loss at low RPM compared to regular piston engines. Also, and in terms of fuel economy, Wankel engines tend to be generally less efficient than four stroke piston engines. 
     Problems also occur with exhaust gases at a peripheral port exhaust, where the prevalence of hydrocarbon can be higher than from the exhausts of regular piston engines. Given the above considerations associated with Wankel engines, appropriate cooling and sealing have become very difficult and probably for these reasons the engine has not become very popular in industries. 
     An example of another type of rotary engine, drawn from the prior art, is set forth in U.S. Pat. No. 5,133,317, issued to Sakita, and which discloses a rotary piston engine incorporating a housing having a cylindrical shaped working chamber with inlet and exhaust ports. First and second piston assemblies are provided, each of which includes one or more pairs of diametrically wedge shaped pistons located within the working chamber. The piston assemblies rotate in a same direction and at recurrently variable speeds, such that one pair of diametrically opposite sub-chambers decreases in volume, with the other pair correspondingly increases in volume. 
     Reference is also made to the engine and drive system set forth in U.S. Pat. No. 6,691,647, issued to Parker, and which teaches an engine having four open-ended curved cylinders disposed in a toroidal arrangement with respect to a central pivot point. Two piston arms are pivoted about the central pivot point, the two arms carrying at opposite ends of each a total of four pistons. Each piston exhibits two faces and, in mounting on the piston arm ends, faces tangentially one away from the other for alternate engagement with adjacent ends of two of the cylinders. 
     Gas turbine technology is another type of non-reciprocating piston engine application and which is in fairly wide use, although not presently in most vehicular applications. A gas turbine extracts energy from a flow of hot gas produced by combustion of gas or fuel oil in a stream of compressed air. Turbines typically incorporate an upstream air compressor (radial or axial flowing), and which is mechanically coupled to the downstream turbine (this also generally defined by a plurality of radially extending and centrifugally driven blade element), with a combustion chamber in between. 
     In this fashion, energy is released when compressed air is mixed with fuel and ignited in the combustion chamber. The resulting gases are directed over the turbine&#39;s blades, thereby spinning the turbine and mechanically powering the compressor. In a final step, the gases are passed through a nozzle, generating additional thrust by accelerating the hot exhaust gases by expansion back to atmospheric pressure. 
     Energy from a turbine engine is extracted in the form of shaft power, compressed air and thrust, in any combination, and used to power such as aircraft, trains, ships, electrical generators and, in regards to land operated vehicles, such as military tanks. Given that gas turbines exhibit very high values of power to weight ratio, and work most efficiently at very high speeds, this renders them for the most part not practical in use with automobiles. 
     SUMMARY OF THE INVENTION 
     The present invention discloses a revolving piston engine for reducing losses associated with conventional reciprocating piston engine, and which further provides easier and improved sealing and cooling properties, lower vibration and reduced power losses properties, in comparison to other prior art rotary piston engine designs. 
     The present invention incorporates any number of pistons, such as a twin piston variant in a disclosed embodiment, incorporated within an outer ring gear exhibiting a plurality of internal teeth, and within which are mounted elliptical and circular gear pairs. In another variant, the selected elliptical gears can be substituted by crank mechanisms. Applications include use in automobiles, power generation, aero industries, battlefield tanks, among other applications. The same concept, with appropriate design changes, can be used to develop a revolving piston air compressor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to the attached drawings, when read in combination with the following detailed description, wherein like reference numerals refer to like parts throughout the several views, and in which: 
         FIG. 1  is a schematic representation of the twin piston, “revolving piston engine” showing the probable locations of the inlet and exhaust ports and also showing both top dead center (TDC) and bottom dead center (BDC), in dotted illustration, equivalent positions for the engine; 
         FIG. 2  is a sectional illustration of pitch ellipses associated with the elliptical gear pair, and in order to maintain a varying speed ratio between the revolving piston and the revolving cylinder head; 
         FIG. 3  is a graphical illustration of a curve showing the relationship between an instantaneous speed ratio of the interengaging gears in  FIG. 2 , from 0° to 720° (two cycles of rotation) and in a counterclockwise direction, the negative values in the curve representative of the face that the two gears rotate in opposite direction; 
         FIG. 4  is a further schematic representation of the revolving piston engine showing the probable gear arrangement and the direction of motion of the various main components; 
         FIG. 5  is a cutaway illustration taken along line A-A in  FIG. 4  and showing the arrangement of the various components and gears; 
         FIG. 6  is a sectional illustration of an elliptical gear pair, and which is rigidly connected to the circular gears shown in  FIG. 4 ; 
         FIG. 7  is an illustration of a double crank mechanism with two cranks and a coupler link, shown in replacement of the two elliptical gears, the first and second cranks replacing the plurality of four elliptical gears previously disclosed in the variant of  FIG. 4 ; 
         FIG. 8  illustrates another double crank mechanism and coupler link replacing the two elliptical gears and according to another variant of the present inventions; 
         FIG. 9  is a partial cutaway B-B of  FIG. 4 , and illustrating a cross-sectional cutaway of the fixed ring cylinder; 
         FIG. 10  is a schematic of the ring gear assembly shown in  FIG. 4 , with revolving cylinder heads and schematic ring gear, which is shown with internal gear teeth. Schematic openings are shown to connect the space between revolving piston and revolving cylinder head to a pair of ports; 
         FIG. 11  is a schematic sectional view of a ring gear assembly as taken in cutaway fashion by line C-C in  FIG. 10 ; 
         FIG. 12  is another schematic illustration of the ring gear assembly shown in  FIG. 4 , with revolving pistons and schematic ring gear, again further shown with internal gear teeth, a pair of schematically illustrated openings connected a space between revolving piston and revolving cylinder head to the pair of ports (see again  FIG. 4 ); 
         FIG. 13  is a schematic sectional view of the ring gear assembly in  FIG. 12  and as shown in cutaway along line D-D; 
         FIG. 14  is a schematic representation of an equivalent revolving piston engine, such as shown in  FIG. 4  and according to a further variant showing a probable gear arrangement and direction of motion of various main components; 
         FIG. 15  is a sectional illustration of an elliptical gear pair rigidly connected to the circular gears associated with but not clearly shown in  FIG. 14 ; and 
         FIG. 16  is a cutaway view taken along line E-E of  FIG. 14  and showing a schematic arrangement of various components and various gears associated with the present design, related elliptical gears being mounted on axes not being shown in the figure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description of the various embodiments of the present invention will now be provided, beginning with that of the various engine components associated with the revolving piston internal combustion engine. Before proceeding with a detailed description, the following definitions are referenced as relevant to and in cooperation with an explanation of the present inventions, namely: 
     Pitch ellipse: This is a mathematical ellipse that is used as a base for making an elliptical gear. When two elliptical gears are in meshing engagement, the pitch ellipse(s) corresponds to the respective elliptical gears “roll” over each other. In application, pitch ellipses are used for kinematic calculations. 
     Focus of ellipse: There are two such points, on the major axis of every ellipse and which are symmetrical about a minor axis of the ellipse. The summation of the distances from both of its focuses to any point on the ellipse is always equal to the length of its major axis. 
     Hollow Ring Cylinder: 
     A hollow circular ring is shown in schematic fashion in  FIG. 1  as well as in cutaway view in  FIG. 5 . The ring  1  may exhibit any suitable cross-section, and which becomes a common axis, outside the cross-section of which renders the ring  1  with a substantially cylindrical geometric shape. 
     The hollow ring  1  is analogous to the cylinder of a conventional reciprocating piston engine, in which the piston slides and may exhibit any cross-sectional shape in order to provide ease of sealing and ease of manufacturing. The ring cylinder  1  may also be made of many parts joined together, or otherwise casted or machined from one or more integrally formed pieces. 
     The ring cylinder  1  has two main components, one is fixed (see as also referenced at  1 ′ in  FIG. 5 ) and the other is revolving (at  1 ″ in  FIG. 5 ). The revolving component consists of two assemblies revolving around the common axis that passes through its center  63  ( FIG. 4 ), of the ring cylinder. These two revolving ring gear assemblies, as also represented by  48  and  49  in  FIG. 4 , revolve at different angular speeds and are coupled to each other with a mechanism that regulates the differential angular speed. 
     Revolving Pistons: 
     Referring again to  FIG. 1 , a pair of revolving pistons are represented at  3  and  9 , in one position, and at  17  and  21 , in another position. The revolving pistons slide within the ring cylinder  1 , and thus revolve around the common axis that passes through the center of the ring cylinder  1 . 
     The revolving pistons are arranged in diametrically opposite fashion relative to each other, and are connected to the ring gear assembly  49 . The shaping associated with the revolving pistons is further intended to complement the sealing requirements associated with the cross-sectional configuration of the ring cylinder  1 , and as these are analogous to the features of the piston associated with a the conventional reciprocating piston engine, referenced hereinafter here as pistons instead of revolving pistons. 
     Revolving Cylinder Head: 
     Referencing again  FIG. 1 , a pair of revolving cylinder heads are represented by  2  and  8 , in one position and by  16  and  20 , in another position. These are very similar to the pistons however, mimic cylinder heads associated with a conventional reciprocating piston engine. 
     The revolving cylinder heads slide in the ring cylinder  1 , and thus revolve around the common axis that passes through the center of the ring cylinder. As best shown in  FIG. 4 , the revolving cylinder heads are diametrically opposite to each other and are connected to the ring gear assembly  48 . The shaping of the revolving cylinder heads, similar to that of the revolving pistons, is intended to suit the sealing requirements of the ring cylinder  1 . These revolving cylinder heads are analogous to the cylinder head of a conventional reciprocating piston engine, as the active volume is trapped between the piston and these parts and, accordingly, hereafter these parts are referred to as cylinder heads instead of revolving cylinder heads. 
     Ring Gear Supporting the Revolving Pistons: 
     As shown throughout the present illustrations, the ring gear assembly may be incorporated with either internal or external configured gear teeth. In the illustrated embodiment, again referencing  FIG. 4 , the ring gear is illustrated as exhibiting internal gear teeth and with the pistons  3 / 9  and  17 / 21  being mounted thereupon. 
     The ring gear may also form a portion of the inner walls of the ring cylinder  1  and to be free to revolve around the common axis that passes through the center of the ring cylinder. As again shown at  49  in  FIG. 4 , the ring gear is also represented in  FIG. 1  at positions  15  and  25 , representing the ring gear  49  as a rigid link in two of its different positions. 
     Ring Gear Supporting the Revolving Cylinder Heads: 
     This is another ring gear assembly with either internal or external configured gear teeth. According to the present illustrations, the ring gear  2  is also chosen to have internal gear teeth, with the cylinder heads mounted upon the ring gear. The ring gear may also define a portion of the inner walls of the ring cylinder  1 , and to be free to revolve around the common axis that passes through the center of the ring cylinder. As shown again at  48  in  FIG. 4  this ring gear is also referenced. In  FIGS. 1  at  14  and  24 , and represents as a rigid link in two of its different positions. 
     Linkage to Constrain the Movement of the Two Ring Gears: 
     A linkage component influences the velocity profile of the ring gear  2 , with respect to that of ring gear  1 . In the preferred embodiment illustrated, two elliptical gears are shown in meshing engagement, with their axes of rotation passing through a geometric focus point of their respective pitch ellipses, used for the linkage purpose. 
     In addition, a few circular gears may be used in series to obtain the direction of rotation and the overall speed ratio as desired. With this linkage, it should be possible to rotate both the ring gears in same direction, with varying speed of ring gear  2  for a constant speed of ring gear  1  and keeping same period for both the ring gears to complete their one revolution. It is possible to use other linkages for obtaining the desired varying speeds; one such linkage could be a four bar linkage operating as double crank mechanism. 
     Principle of Operation: 
     To understand the operation of the engine, it is necessary first to understand the functioning of the two elliptical gears. The pitch ellipse (both pitch ellipses being identical) used for the two elliptical gears has an eccentricity of approximately 0.38. Items  29  and  31 , in  FIG. 2 , represent the elliptical gears. The instantaneous speed ratio between gear  31  to gear  29 , with their axes of rotation passing through their respective focal points are further shown at  32  and  30 . 
     With respect to rotation  39  (again  FIG. 2 ) of the gear  29  in direction shown by  41 , is plotted in  FIG. 3 . A further rotation (at  40  in  FIG. 2 ) of gear  31 , corresponding to the rotation  39  of gear  29 , can further be calculated from the geometry of the pitch ellipses. 
     In  FIG. 3 , the horizontal axis represents the rotation  39  of gear  29  in direction  41  from 0° to 720°, and the vertical axis represents the instantaneous speed ratio between gear  31  to gear  29 . It can be seen from  FIG. 3  that the speed ratio varies approximately from −2.22 to −0.45. The negative speed ratio indicates that the direction of rotation  42  of gear  31  is opposite to direction of rotation  41  of gear  29 . 
     As both the elliptical gears are identical, they have equal number of teeth and thus simultaneously complete their one revolution. In  FIG. 3 , it can be seen that at points the speed ratio obtained is unity, at that moment both the elliptical gears rotate at the same instantaneous speed. These positions of the two ring gears, when the speed ratio is unity, are analogous to the TDC and BDC positions in the conventional reciprocating piston engine. 
     The piston and corresponding cylinder head are at closest and farthest to each other in these positions of TDC and BDC respectively. It is further noted that, with reference again to  FIG. 2 , the distance between the two focal points,  30  and  32 , as well as between corresponding axes of rotation, is equal to the length of the major axis of the pitch ellipse. 
     Engine Kinematics Construction: 
     The engine has one hollow ring cylinder, represented again at  1  in  FIG. 1 , consisting of fixed and revolving parts (see again  1 ′ and  1 ″ as referenced in the side cutaway of  FIG. 5 ). The fixed part of the ring cylinder is used for providing cooling to the cylinder and also has both an intake port  27  and an exhaust port  26 , connected to it (see also  FIG. 4 ). 
     The revolving parts of the ring cylinder are mainly made of two ring gears, namely ring gear  1  and ring gear  2 . These ring gears also form a part of the inner walls of the ring cylinder. The pistons and the cylinder heads are integral parts of the ring gears assemblies and thus the ring gears revolve with the pistons and the cylinder heads respectively. 
     As the ring gears revolve with the piston and the cylinder heads, proper design of these ring gears can make sealing of the piston and cylinder heads less difficult. The ring gear  49 , which has internal teeth, is connected with a spur gear  50  (again  FIGS. 4 and 5 ) with a speed ratio of 1:2. This spur gear has a fixed axis  52 , and has another coaxial gear  51  rigidly connected to it. 
     The coaxial gear  51  drives another spur gear  53 , with a speed ratio of unity, having another fixed axis  55 . Gear  53  has an elliptical gear  54  rigidly connected to it with an axis  55  passing through the focus of the pitch ellipse of the elliptical gear  54 . The elliptical gear  54  drives another elliptical gear  56 , which has its fixed axis of rotation  58  passing through the focus of its pitch ellipse. 
     The elliptical gear  56  is rigidly connected to a coaxial spur gear  57 , and which in turn drives the ring gear  2 . The speed ratio between the spur gear  57  and ring gear  2  is, in the embodiment illustrated 2:1. 
     A flywheel, not shown in the figures, of appropriate size is provided and connected to the ring gear  1 , and in order to support the revolving pistons. Thus the ring gear  1  rotates at half the speed of the elliptical gear  54  and the ring gear  2  rotates at half the speed of the elliptical gear  56 . 
     The full gear train ensures that ring gear  1  and ring gear  2  rotate in the same direction. As shown in  FIG. 4 , arrows  59 ,  60 ,  61  and  62  show the direction of rotation of different gears. The elliptical gears  54  and  56  are assembled in such a way that they have instantaneous speed ratio of unity when the pistons and the corresponding cylinder heads are closest to each other and the speed of the elliptical gears  56  is tending to reduce as compared to the speed of gear  54  as the gears rotate in the direction shown by  62  and  61 , i.e. as the ring gears rotate in the direction shown by  59 . 
     It should be further stated that the linkage utilized here includes all the gears for motion transfer from the ring gear  1  to ring gear  2  make a positive drive, and in order to provide non-slip motion. Thus, the ring gear  1  drives the ring gear  2  with the desired speed variation. 
     The elliptical gears  54  and  56  in mesh thus ensure the differential speeds between pistons and the cylinder heads. It is important to note that the linkage with elliptical gears can be replaced by some other linkage; one such possible linkage including a four bar linkage operating as double crank mechanism (as will be described in more detail in reference to  FIGS. 7 and 8 ). 
     Specifically, and as is shown in  FIG. 7 , a double crank mechanism with cranks  70  and  71  are illustrated with interconnecting coupler link  72 . This is in replacement of the two elliptical gears previously illustrated at  54  and  56  in the embodiment of  FIGS. 4 and 5 , and which are referenced in broken lines. The crank  70  replaces the elliptical gear  54 , thus being rigidly connected to the gear  53 . The crank  71  further replaces the elliptical gear  56 , thus being rigidly connected to gear  57 . 
     As further referenced in  FIG. 8 , another variation of a double crank mechanism is provided and illustrating cranks  73  and  74  with interconnecting coupler line  75  (this in replacement again of the elliptical gears  54  and  56 ). As the cranks  73  and  74  revolve in a same direction, they are coaxially and rigidly connected to the gears  50  and  57 , respectively, and without the need of gear  53  and meshing gear  51 . Also, an output shaft, which is also not shown, is connected to the ring gear  1  and operates in a fashion as conventionally known in the art. 
     As again illustrated in  FIG. 9 , a partial cutaway B-B of  FIG. 4  illustrates a cross-sectional cutaway of the fixed ring cylinder  1  and in particular referencing the selected ports  27 . Further shown in  FIG. 10  is a schematic of the ring gear assembly, as shown in  FIG. 4 , with revolving cylinder heads  2  and  8  and schematic ring gear  48 , which is shown with internal gear teeth. Schematic openings  76  and  77  are shown to connect the space between revolving piston and revolving cylinder head to the pair of ports  26  and  27 . 
       FIG. 11  is a schematic sectional view of a ring gear assembly  48 , as taken in cutaway fashion by line C-C in  FIG. 10 .  FIG. 12  is another schematic illustration of the ring gear assembly shown in  FIG. 4 , with revolving pistons  3  and  9  and schematic ring gear  49 , again further shown with internal gear teeth. A pair of schematically illustrated openings, at  78  and  79 , connect a space between the revolving piston and revolving cylinder head to the pair of ports  26  and  27  (see again  FIG. 4 ). 
     Referring to  FIG. 13 , a schematic sectional view is again shown of the ring gear assembly  49  in  FIG. 12 , in cutaway along line D-D.  FIG. 14  is a schematic representation of an equivalent revolving piston engine, such as shown in  FIG. 4  and according to a further variant showing a probable gear arrangement and direction of motion of various main components. Of note, similar identification numbers are used for various items corresponding to that illustrated in  FIG. 4 . The ring gears are further exhibited as having external gear teeth. 
     The elliptical gears that are mounted on axes  55  and  58 , in reference to  FIG. 14  and further shown in  FIG. 15 , which is a sectional illustration of an elliptical gear pair  54  and  56  rigidly connected to the circular gears  53  and  57 . The axes  55  and  58  are again identical to that shown in  FIG. 14 . 
     Finally,  FIG. 16  is a cutaway view taken along line E-E of  FIG. 14  and showing a schematic arrangement of various components and various gears associated with the present design. Relative elliptical gears are further understood as being mounted on axes not being shown in the figure. 
     Sequence of Operation: 
     For purposes of case of illustration, the gear teeth for all the gears are not automatically shown. Rather, and in specific instances, only pitch circles and pitch ellipses are shown for easy understanding. Referencing again the piston and cylinder head pair  3  and  2 , in  FIG. 1  and in  FIG. 4 , the pitch ellipses  31  and  29  are shown separately for easy understanding, otherwise elliptical gears  56  and  54  have similar pitch ellipses as represented by  31  and  29 , and all have the same eccentricity. 
     In this fashion, the curve illustrated in  FIG. 3  is equally applicable for the elliptical gear pair  56 ,  54 . Referencing again  FIG. 3 , a portion  43  of the curve, when the speed ratio, neglecting the negative sign, is less than unity, the elliptical gear  56  rotates slower than the elliptical gear  54 , and thus the ring gear  2  and the cylinder head  2  revolves at a slower speed than the speed of revolution of the ring gear  1  and the piston  3 . 
     Thus, a volume between the faces  4  and  6  keeps on increasing for that portion  43  of the  FIG. 3 , while revolving in the direction as shown by  28 . The positions of the piston and the cylinder head at the start of the portion  43  of the curve in  FIG. 3  are represented by  3  and  2 , and that at the end of portion  43  is represented by  17  and  16 , in  FIG. 1 , respectively. 
     Similarly the other pair of piston and the cylinder head at position  9  and  8  at the start of portion  43  attains the positions  21  and  20  respectively, at the end of portion  43  in  FIG. 3 . The positions of the pistons and cylinder heads at the end of portion  43  are the starting positions for a succeeding portion  44  in  FIG. 3 . At the end of the further portion  44  in  FIG. 3 , the piston  3  attains a position of piston  9 , whereas piston  9  attains the position of piston  3 . Similarly, cylinder head  2  attains the position of cylinder head  8 , whereas cylinder head  8  attains position of cylinder head  2  as again represented in  FIG. 1 . 
     Further succeeding portion  45  in  FIG. 3  is equivalent to the portion  43 , with the piston-cylinder head pairs  3 ,  2  and  9 ,  8  having interchanged their respective positions. Similarly, the ending and beginning portions  46  and  47  together are similar to the portion  44 , with piston-cylinder head pair  3 ,  2  attaining positions at  21 ,  20  respectively at the start of the portion  46  and again attaining positions  3 ,  2  at the end of portion  47 . Similarly, locations  9 ,  8  attain positions  17 ,  16  at the start of portion  46  and again attain positions  9 ,  8  at the end of the portion  47  respectively. The cycle continues to repeat for further revolutions of the ring gears and, thus for one complete revolution of a piston and cylinder head, the elliptical gears require two complete revolutions. 
     For simplicity, a piston-cylinder head pair  3 ,  2  is generally called a first pair and the pair  9 ,  8  is called the second pair (see again  FIG. 1 ). In  FIG. 3 , the portion  43  represents the power stroke for first pair and at the same time intake stroke for the second pair. Similarly, portion  44  represents exhaust stroke for first pair and compression stroke for the second pair; portion  45  represents intake stroke for first pair and power stroke for the second pair and, finally, portions  46  and  47  together represent compression stroke for first pair and exhaust stroke for the second pair. 
     In a preferred application, fuel ignition should take place appropriately after start of the portion  43  or portion  45  for the respective pair. The time delay between start of the portion  43  or  45  and the fuel ignition is to be selected very appropriately and can be varied with engine speed. As the ignition takes place, in the confined space between faces  4  and  6  or in a specially designed combustion chamber outside the confined space, at the time of ignition as stated above, pressure is developed between the two faces forcing them to move apart. Any motion after start of portion  43  or  45 , in the direction opposite to  28  will cause the two faces to come closer, this will increase the pressure between the two faces, which is difficult unless the two faces are forced externally to rotate against direction  28 . 
     Thus, and in the absence of sufficient external forces, the piston  3  and the cylinder head  2  will continue to rotate in the direction  28  (again  FIG. 1 ), by the pressure developed by the ignition of fuel, thus increasing the volume between the two faces  6  and  4 . In this fashion, the ignition of fuel (the power stroke) will force the piston and thus the ring gear  1  to rotate in the direction  28 . 
     It should be noted that, in portions  43  and  45  (again  FIG. 3 ), the volume expansion between the faces  6  and  4  is possible only if the two ring gears rotates in the direction  28 , which is same as direction  59 . As the ring gear  2  and thus the cylinder heads are driven by the ring gear  1 , the cylinder head follows the piston in the direction  59  keeping the speed relationship with the piston as constrained by the curve as shown in  FIG. 3 . 
     During the power stroke (again portion  43 ), the ring gear  2  and thus cylinder heads revolve slower than the piston and the ring gear  1 . During the exhaust stroke, the portion  44 , the ring gear  2  and the cylinder heads revolve faster than the ring gear  1  and pistons, thus forcing the product of combustion out through the exhaust port. During the intake stroke, the portion  45 , the cylinder heads again revolve slower than the pistons thus increasing the volume between the faces  4  and  6  and thus sucks in the air or air fuel mixture through intake port. During the compression stroke (the portions  46  and  47  together), the cylinder heads revolve faster than the pistons, and thus reduces the volume between the faces  4  and  6  compressing the air or air fuel mixture and thus making it ready for combustion in power stroke. 
     The above explains cycle repeats for other piston-cylinder head pair  9 ,  8  keeping 180° phase difference with the pair  3 ,  2 . The faces  12  and  10  in pair  9 ,  8  are corresponding to the faces  6  and  4  in pair  3 ,  2 . Furthermore, the portions  43 ,  44 ,  45 ,  46  and  47  in  FIG. 3  illustrate the zones for ideal strokes for the revolving piston internal combustion engine; the actual start and end of a stroke being decided after considering dynamics of engine, fuel characteristics and many other parameters. It is also understood that appropriate intake and exhaust valves can replace the intake and exhaust ports. 
     Additional preferred embodiments contemplate incorporating more pairs of piston and cylinder head for one ring cylinder, alternatively there can be provided a single tandem arrangement of piston and cylinder head for one ring cylinder. In the instance of “N” number of pairs (for “N” being any even number) for one ring cylinder, the overall speed ratio between the ring gears, and thus the assemblies to the respective elliptical gears, will be 1:N. The mechanism that uses elliptical gears can be replaced by some other mechanism that can give desired variation in the speed of the cylinder head for constant piston speed; one such mechanism could be an appropriate four bar linkage operating as a double crank mechanism (as again previously described in  FIGS. 7 and 8 ). 
     Calculation for the Compression Ratio: 
     As disclosed in  FIG. 1 , the volume between faces  4  and  6  can be assumed as the clearance volume analogous to the reciprocating piston engine, as piston at  3  and cylinder head at  2  are in positions equivalent to the TDC in a conventional reciprocating piston engine. The volume between faces  18  and  19  can also be taken as expanded volume, as the piston  3  in position  17  and cylinder head  2  in position  16  are equivalent of BDC in conventional reciprocating piston engine. Similarly, a volume between faces  10  and  12  is considered clearance volume for another pair of piston  9  and cylinder head  8 , and the volume between faces  22  and  23  is an expanded volume as positions  21  and  20  are the BDC equivalent position for the piston  9  and cylinder head  8  respectively. 
     The compression ratio (CR) is the ratio of volume between faces  19  and  18  to that between faces  6  and  4 . 
     In other words CR=(angle from  18  to  19 )/(angle from  4  to  6 ); 
       CR=((angle from 15 to 25)−(angle from 14 to 24)+(angle from 4 to 6))/(angle from 4 to 6)
 
     All the angles mentioned above are measured in the direction  28 . 
     The angle from angular locations  15  to  25  (see again  FIG. 1 ) is the ratio of rotation of elliptical gear  29  for the portion  43  to the speed ratio between elliptical gear and the ring gear  1 . Similarly, angle from angular locations  14  to  24  is the ratio of rotation of elliptical gear  31  for the portion  43  to the speed ratio between elliptical gear and the ring gear  2 . 
     These angles can be calculated from the geometry of the pitch ellipse as shown in  FIG. 2 . The pitch ellipse used for the elliptical gears is having length of major axis (distance from  35  to  37  or  37  to  66 ) as 80 units and length of minor axis (distance from  64  to  67  or  65  to  68 ) as 74 units, thus the eccentricity is 0.3799671. For the TDC position, the two elliptical gears are shown by  33  and  34 , having the instantaneous speed ratio between them as unity and thus in this position length between  32  and  69  is equal to the length between  30  and  69 . Here  30  and  32  are the focal points of the respective ellipses and  69  represent the point of contact of the two pitch ellipses. 
     As the speed ratio between elliptical gears to ring gears is 2:1 and the pitch ellipses are symmetrical about their major and minor axes. 
     Angle from  15  to  25 =angle between lines  38 - 30  and  30 - 66   
     OR angle from  15  to  25 =angle between lines  65 - 30  and  30 - 66 =112.332° 
     Similarly, 
       Angle from 14 to 24=Angle between lines 36-32 and 32-37=Angle between lines 64-32 and 32-35=67.668°
 
     If we have clearance angle as 4°, then CR=(112.332−67.668+4)/(4)=12.163 
     If the clearance angle is changed to 5° then for the same engine the CR becomes (112.332−67.668+5)/5)=9.9328 
     Thus, it can be seen that just by changing the clearance angle the CR can be changed very easily. The CR can also be changed easily by selecting pitch ellipses with different eccentricity. It can be seen that lower the eccentricity of pitch ellipses, lesser is the CR obtained. It is to be noted here that, for the calculations faces  4 ,  6 ,  18 ,  19 , etc. are assumed to be planer faces and the planes of the faces pass through the common axis of revolution. 
     Calculation for Output Power: 
     The volume between faces  3  and  2  acts as the active volume. After TDC the charge between faces  3  and  2  is ignited. As the result of combustion, the pressure between the faces  3  and  2  increases and forces the volume between the faces to increase and thus forces the ring gears to rotate in CCW direction as shown in  FIG. 4 . The theoretical power generated can be calculated with the standard power generation equation: 
       CV*CR 
     
       
      
       W= 
       ∫ 
       p 
       + 
       dv  
      
     
       CV         Where:   W=Work done OR power generated,   CV=clearance volume,   CR=compression ratio,   p=pressure of the active volume,   v=volume of the active volume.       
     In practice, some power is always lost in compressing the air or air-fuel mixture in the active volume. Some additional quantum of power is also lost in accelerating and decelerating the ring gear  2  assembly, supporting the revolving cylinder heads and associated linkages. The loss of power in acceleration and deceleration depends upon the total mass and inertia of the components undergoing speed variation. Given this, it is advisable to keep the mass and the inertia of such parts to a minimum as to reduce the losses. The difference between the power generated and the power lost becomes available for utilization outside the engine. 
     Advantages of the Revolving Piston Engine: 
     Given the above description, the following bullet list identifies the advantages associated with the present inventions, and which are as follows:
     1. The revolving piston engine does not have exhibit any reciprocating part.   2. The engine is suitable for use with all types of fuels and different ignition methods, and such as which are also used in reciprocating piston engine. As disclosed herein, the combustion chamber can also be designed outside the ring cylinder.   3. Use of ports for intake and exhaust are possible instead of valves to operate, this rendering the engine more robust. Thus, and in this way, a four stroke engine can be made to work with ports.   4. During the active combustion cycle, and while the products of combustion expand, the active volume between the corresponding faces of the piston and cylinder head revolves in the ring cylinder; thus creating a revolving heat source making cooling easy and efficient, and in addition to providing increased surface area available for cooling.   5. A large portion of the ring cylinder is fixed making it suitable for easy cooling by liquid coolant or any other cooling method.   6. A same ring cylinder can accommodate one to many pairs of pistons and cylinder heads, thus allowing higher power generation possible for approximately a same physical size of engine. This aspect also allows higher power to weight ratio obtainable, with less modifications.   7. Vibration levels will be very low, as the reciprocating components are absent and the pistons and cylinder heads can be arranged in such a way that they balance other pistons and cylinder heads within the same ring cylinder.   8. The engine can be used as an engine module. Similar engines can be put together in parallel with a common output shaft (e.g. scalability); thus it is easy to increase power output without much change in the design.   9. It is possible to use multiple engines at a time with a common output shaft to make an equivalent of multi-cylinder reciprocating piston engine. The engine can be designed for ease of interchangeability and thus making it possible to keep an engine as a spare and use it to replace a faulty engine in emergency with ease and with minimum down time required for the engine repair.   10. While using multiple engines, it is possible to arrange the different engines on same output shaft in a way as to have a power stroke in one engine overlapping compression stroke in other engine, for obtaining smooth power output and thus possibly reducing the size of the flywheel.   11. Instead of elliptical gear pairs, it is also envisioned that some other mechanism can be used to obtain desired differential velocity for the two ring gears supporting the pistons and cylinder heads. An ideal differential velocity pattern is that which will give maximum separation between the revolving piston and revolving cylinder head during power and intake strokes with minimum acceleration and deceleration, keeping the clearance volume to a minimum.   12. It is possible, in an alternate variant, to use the space between faces  7 ,  11  and faces  13 ,  5  for pre-compression of the separately filled air or air fuel mixture during intake stroke or power stroke, and supplying it to the active volume between  6 ,  4  and  12 ,  10  appropriately during compression stroke. This can be used to increase the output power, as in super charging of the engine.   13. A very compact engine can be made as it contains less number of parts.   14. It can be suitably designed to have less down time while repairing the engine.   15. The ring cylinder can have any suitable crass-section as required for easy manufacture and assembly.   16. The engine&#39;s expected life is longer as it has no reciprocating part and very effective cooling is possible. The engine heating is less because of revolving active volume.   17. It is possible to mount spark plug on to the piston itself to have better control on the ignition timing and thus eliminating the need of separate combustion chamber.   18. It is very easy to use this principle to develop a revolving piston compressor for that the ports or the valves are to be appropriately designed and relocated. In such applications, and referring again to the graph of  FIG. 3 , portions  44 ,  46  and  47  are used for compression strokes and portions  43  and  45  are used for intake strokes. The input power is to be supplied to the ring gear  1 .   19. The revolving piston can additionally be adapted for application to newly developing steam engine technologies.   20. The pistons and cylinder heads can be arranged in equi-spaced fashion to their respective assemblies for better balancing of the engine.   21. In certain applications, the internal gear arrangement in use with the outer ring gear can be substituted by external gears.   

     Having described my invention, other and additional preferred embodiments will become apparent to those skilled in the art to which it pertains, and without deviating from the scope of the appended claims.