Abstract:
A reciprocating engine comprising a cylinder assembly having a pair of connected pistons for reciprocation therein, a drive ring having a rotational orbit substantially encircling the cylinder assembly and a power transfer mechanism for coupling and converting reciprocating motion of the piston to rotating motion of the drive ring. The engine with drive ring can be more compact than an equivalent conventional engine with crankshaft, can generate higher torque and can be subject to less cylinder wall wear due to side thrust of the pistons.

Description:
FIELD OF INVENTION  
         [0001]    The present invention relates to the field of reciprocating engines. In particular, to a reciprocating engine having a drive ring.  
         BACKGROUND  
         [0002]    Reciprocating engines have been known and in common use for more than a century. The basic architecture of the most commonly used of these engines comprises reciprocating pistons connected to a crankshaft via crank throws. As more demanding applications for reciprocating engines are developed the limitations of this commonly used engine architecture are being pushed. The requirements such as those in aerospace and submarine applications for compact, high torque and durable engines are difficult to meet with the classic reciprocating piston and crankshaft architecture. In particular, the use of a crankshaft and its associated geometry contribute to increased engine size, less than optimal torque generation and premature cylinder wall wear due to side thrust loads on the pistons. What is needed is a reciprocating engine that is compact, generates high torque and that mitigates cylinder wall wear.  
         SUMMARY OF INVENTION  
         [0003]    An embodiment of the reciprocating engine of the present invention comprises a cylinder assembly having a pair of connected pistons for reciprocation therein, a drive ring having a rotational orbit substantially encircling the cylinder assembly and a power transfer mechanism for converting reciprocating motion of the piston to rotating motion of the drive ring. The engine with drive ring can be more compact than an equivalent conventional engine with crankshaft, can generate higher torque and can be subject to less cylinder wall wear due to side thrust of the pistons. The engine with drive ring eliminates the need for a crankshaft with it attendant crank throws and journals.  
           [0004]    In accordance with one aspect of the present invention, an engine comprising a cylinder assembly, a pair of connected pistons for reciprocating motion within the cylinder assembly, a drive ring arranged for rotational motion encircling the cylinder assembly; and a power transfer mechanism for converting reciprocating motion of the pair of pistons to rotational motion of the drive ring.  
           [0005]    In accordance with another aspect of the present invention, an engine as described in the aspect above wherein the power transfer mechanism comprises: a reciprocating member connected to the pair of pistons, a drive cam connected to the drive ring, and a plurality of cam follower mechanisms connected to the reciprocating member for cooperative engagement with the drive cam.  
           [0006]    Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0007]    The present invention will be described in conjunction with the drawings in which:  
         [0008]    [0008]FIG. 1 is a perspective view of an exemplary embodiment of the engine of the present invention.  
         [0009]    [0009]FIG. 2 is a side view of an exemplary embodiment of the engine of the present invention.  
         [0010]    [0010]FIG. 3 is a cross-sectional view of a sub-assembly of an exemplary embodiment of the engine of the present invention.  
         [0011]    [0011]FIG. 4 is a perspective view of an exemplary embodiment of the engine of the present invention with details of a valve drive mechanism.  
         [0012]    [0012]FIG. 5 is a perspective view of an exemplary embodiment of the engine of the present invention with details of an alternative valve drive mechanism.  
         [0013]    [0013]FIG. 6 is a cross-sectional view of an exemplary embodiment of the engine of the present invention with details of an alternative valve drive mechanism.  
     
    
     DETAILED DESCRIPTION  
       [0014]    An embodiment of an engine  100  according to the present invention is represented in FIGS. 1-3 (N.B. FIG. 3 represents a sub-assembly of the engine  100 ). The engine  100  is a reciprocating engine comprising a cylinder assembly  120  having a pair of pistons  130  joined by a connecting rod  140  for reciprocation therein, a drive ring  150  having a rotational orbit substantially encircling the cylinder assembly  120  and a power transfer mechanism  160  for coupling and converting reciprocating motion of the pistons  130  to rotating motion of the drive ring  150 . The cylinder assembly  120  comprises a cylinder bore  122  and a pair of cylinder heads  124 . Each piston  130  in conjunction with the cylinder bore  122  and one of the cylinder heads  124  defines a combustion chamber. The engine  100  is an internal combustion engine of any of the power cycle types such as, for example, Otto cycle or Diesel cycle and of either two-stroke or four-stroke operation. In an alternative embodiment the engine  100  can be an external combustion engine such as for example a Watt (steam) engine or a Stirling cycle engine.  
         [0015]    In normal operation of the engine  100  the pair of pistons  130  and the connecting rod  140  reciprocate, in unison, within the cylinder assembly  120 . The power transfer mechanism  160  comprises a reciprocating member  162  that is connected to the pair of pistons  130  via the connecting rod  140 , a drive cam  164  connected to the drive ring  150  and a plurality of cam follower mechanisms  166 . Reciprocation of the pistons  130  and connecting rod  140  result in reciprocation of the reciprocating member  162 . The reciprocating motion of the reciprocating member  162  imparts rotational motion to the drive ring  150  by the coupling of the reciprocating member  162  to the drive cam  164  via the cam follower mechanisms  166 .  
         [0016]    The reciprocating member  162  in the exemplary embodiment is an elongate member connected, via the connecting rod  140 , to the pair of pistons  130  and to one of the plurality of cam follower mechanisms  166  at each of its two ends. In alternative embodiments of the engine  100  the reciprocating member  162  can be one of: an elongate member with one end connected to the pair of pistons  130  and the other end connected to a cam follower mechanism  166 , a member connected to the pair of pistons  130  and having more than two ends each one connected to one of the plurality of cam follower mechanisms  166 , or other similar structures.  
         [0017]    The drive cam  164  in the exemplary embodiment comprises a sinuous recess or grove formed between a pair of cam sections  168  connected to the drive ring  150 . Each of the cam sections  168  has a working face  170 . The recess is defined by the spatial relationship between the working faces  170  of the pair of cam sections  168 . Undulations in the sinuous recess are engineered to provide specific engine characteristics (e.g. torque multiplication) using techniques similar to those used in the design of cam-drive or swash-plate engines. In an alternative embodiment of the engine  100 , the drive cam  164  can be formed as part of the drive ring  150 , as a separate part or an assembly connected to the drive ring  150  or by an assembly of parts that comprise the drive ring  150 . In the exemplary embodiment the cam follower mechanisms  166  are received in the recess of the drive cam  164  between the two working faces  170 . In another alternative embodiment the drive cam  164  can comprise a sinuous ridge or protrusion, with two working faces  170 , connected to the drive ring  150 . In this alternative embodiment substantially opposed cam follower mechanisms  166  cooperatively engage the two working faces  170 . In a further alternative of the engine  100 , the drive cam  164  can be formed on either or both of the end faces of the drive ring  150 .  
         [0018]    The cam follower mechanisms  166  of the exemplary embodiment comprises a pair of roller bearings, radially spaced apart relative to the cylinder assembly  120 , that cooperate with the working faces  170  of the drive cam  164 . The pair of roller bearings comprises an inner bearing and an outer bearing. The inner bearing is proximate the cylinder assembly  120  relative to the outer bearing. The pair of cam sections  168  is arranged such that the inner bearing engages the working face  170  of one of the pair of cam sections  168  and the outer bearing engages the working face  170  of the other of the pair of cam sections  168 . Such an arrangement, in which each roller bearing engages only one working face  170 , results, during normal engine operation, in each roller bearing rotating only in one direction and prevents binding when the drive ring  150 , and therefore the drive cam  164 , rotates relative to the reciprocating member  162 . In an alternative embodiment of the engine  100 , the cam follower mechanisms can comprise, for example, ball bearings, conical bearings or other similar mechanisms.  
         [0019]    The drive ring  150  is secured laterally by a plurality of ring retention mechanisms  180 . A number of ring retention mechanisms  180 , each connected to the cylinder assembly  120 , engage the end faces of each of the pair of cam sections  168  that are connected to the drive ring  150 . Each of the ring retention mechanisms comprises a roller bearing thereby permitting the drive ring  150  to freely rotate while preventing lateral movement of the drive ring  150 . In an alternative embodiment of the engine  100 , the ring retention mechanisms  180  can engage the end faces of the drive ring  150  directly. In another alternative embodiment of the engine  100  each of the ring retention mechanisms  180  can comprise a ball bearing, a conical bearings or other similar mechanisms.  
         [0020]    A pair of ring carrier mechanisms  190  provide for the free rotation of the drive ring  150  in an orbit that substantially encircles that cylinder assembly  120 . In the exemplary embodiment each of the ring carrier mechanisms  190  supports one of the pair of cam sections  168  and thereby the drive ring  150 . The ring carrier mechanisms  190  comprise a plurality of roller bearings that permit the free rotation of the drive ring  150 . In an alternative embodiment of the engine  100  the ring carrier mechanisms  190  can support the drive ring  150  directly. In another alternative embodiment of the engine  100  each of the ring carrier mechanisms  190  can comprise a ball bearing, a conical bearings or other similar mechanisms. In yet another embodiment of the engine  100  the functions of a ring retention mechanisms  180  and be combined with the functions of a ring carrier mechanisms  190  in a single mechanism.  
         [0021]    The drive ring  150  comprises a circumferentially geared face forming a drive gear  155 . Power generated by the engine  100  can be imparted to an external driven element having a driven gear (not shown) engaging the drive gear  155 . Alternative configurations (e.g. straight cut or beveled) of the drive gear  155  and the driven gear provide for adapting to a driven shaft that is parallel to the axis of rotation of the drive ring  150 , that is perpendicular to the axis of rotation of the drive ring  150  or that is at substantially any angle in between the two previously recited orientations. In another alternative embodiment of the engine  100  the drive gear  155  and the driven gear can be connected via a drive chain. In yet another alternative embodiment of the engine  100  the drive gear  155  and driven gear can be replaced by a corresponding drive pulley and a driven pulley connected via a drive belt or other similar power transfer mechanisms.  
         [0022]    In an alternative embodiment of the engine  100  the cylinder assembly  120  and connecting rod  140  can be adapted to operation with a single piston  130 . In a further alternative embodiment, the engine  100  comprises a plurality of cylinder assemblies  120  arranged to be substantially encircled by the rotational orbit of the drive ring  150  with the pistons  130  of each of the plurality of cylinder assemblies  120  connected to the drive ring  150  via a power transfer mechanism  160 .  
         [0023]    In the exemplary embodiment of the engine  100  represented in FIGS. 1-3 the axis of rotation of the drive ring  150  is substantially parallel to the longitudinal axis of the cylinder assembly  120 . In an alternative embodiment of the engine  100  the axis of rotation of the drive ring  150  can be at a non-zero angle to the longitudinal axis of the cylinder assembly  120  and the power transfer mechanism  160  can be adapted appropriately.  
         [0024]    Referring now to FIG. 4 which represents an exemplary embodiment of the engine  100  of the present invention with detailed features of a valve (induction and exhaust) drive mechanism comprising a pair of sinuous valve timing cams  200 , a plurality of push rods  210  and a plurality of rocker arms  220 . One of the pair of sinuous valve timing cams  200  is formed on each of the cam sections  168  which are coupled to the drive ring  150 . Each of the plurality of push rods  210  engage, at one end, one of the valve timing cams  200 . Each of the plurality of push rods  210 , at its other end, engages one of the plurality of rocker arms  220  that provide for valve actuation. Although the exemplary embodiment illustrates a single valve timing cam  200  per cam section  168 , it will be understood that multiple valve timing cams  200  can be provided for each cam section  168 . Multiple valve timing cams  200  can provide, for example, different timing of induction and exhaust valves or different timing between multiple induction or multiple exhaust valves.  
         [0025]    In a further alternative embodiment of the engine  100  one or more of the valve timing cams  200  can be formed directly on the drive ring  150 .  
         [0026]    [0026]FIGS. 5 and 6 represent another exemplary embodiment of the engine  100  of the present invention with detailed features of an alternative valve drive mechanism comprising a pair of cam ring gears  310 , a pair of cam gears  320  and a pair of cam drive shafts  330 . One of the pair of cam ring gears  310  is connected to each of the cam sections  168  that are coupled to the drive ring  150 . Each one of the pair of cam gears  320  engages one of the pair cam ring gears  310 . Each one of the cam drive shafts  330  is connected to one of the pair of cam gears  320 . The cam drive shafts  330  provide for valve actuation through additional well-known mechanisms such as cam shafts, rocker arms and other similar mechanisms. Although the exemplary embodiment illustrates a single cam ring gear  310  per cam section  168 , it will be understood that multiple cam ring gears  310  can be provided for each cam section  168 . Multiple cam ring gears  310  can provide, for example, different timing of induction and exhaust valves or different timing between multiple induction or multiple exhaust valves. In a further alternative embodiment of the engine  100  one or more of the cam ring gears  310  can be coupled directly to the drive ring  150 .  
         [0027]    It will be understood by those skilled in the art that a reciprocating pump with a drive ring having a structure similar to that of any of the embodiments the engine of the present invention described above falls within the scope and spirit of the present invention. In the case of a reciprocating pump having a drive ring, power is received by the pump via the rotation of the drive ring and is converted and transferred to reciprocating motion of the pistons.  
         [0028]    It will be apparent to those skilled in the art that numerous modifications and departures from the specific embodiments described herein may be made without departing from the spirit and scope of the present invention.