Abstract:
A two-stroke barrel engine includes a power output shaft configured to rotate, an even number of cylinders encircling the power output shaft, wherein each cylinder includes opposing first and second power pistons configured to reciprocate within their respective power cylinder, and a pair of non-rotating wobbleplates opposed and hingedly connected to the power pistons. The wobbleplates are configured to transfer the reciprocating motion of the power pistons to rotary motion of the power output shaft via a nutating motion of the non-rotating wobbleplate.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to internal combustion engines, and more specifically to a two stroke barrel engine. 
     BACKGROUND 
     A barrel engine is a type of reciprocating engine that replaces the common crankshaft with a circular plate (the swashplate). Pistons press down on a circular plate in a circular sequence, forcing it to nutate around its center. The plate, also known as a wobble plate, is typically geared to produce rotary motion. 
     Barrel engines are differentiated from other engines in that the cylinders are arranged in parallel around the edge of the plate, and possibly on either side of it as well, and are aligned with the output shaft rather than at 90 degrees as in crankshaft engines. This design results in a very compact, cylindrical engine, ideally suited for use in aircraft engines. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       One or more embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, and wherein: 
         FIG. 1  illustrates a barrel engine according to an embodiment; and 
         FIG. 2  is a diagram of a wobbleplate bearing illustrating an alternative anti-rotating arrangement. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a longitudinal view and an end view of a barrel engine  100  according to one embodiment. The engine  100  features a two stroke barrel arrangement that includes a frame, i.e., cylinder block  25 , that houses an even number of cylinders encircling a power shaft  13 , wherein the centerlines of all the cylinders are parallel to each other. The cylinders operate in pairs, wherein each pair of cylinders comprises the two cylinders on opposite sides of power shaft  13 . Engine  100  further includes a wobbleplate drive system that includes two non-rotating wobbleplates  9 , each mounted on opposite ends of cylinder block  25 . 
     Each cylinder comprises a power cylinder comprising power sleeve  3  and a stepped charging cylinder comprising stepped sleeve  4 . Disposed within each power cylinder are opposing piston  1  and  2 . At a top stroke, a piston position encloses minimum cylinder volume; at a bottom stroke a piston position encloses maximum cylinder volume. Piston  1  is a power piston whose reciprocating motion drives power shaft  13 . Piston  2 , however, includes both a power piston and a stepped charging piston portion. 
     The cylinders operate in pairs opposite each other, wherein the stepped charging piston portion of piston  2  compresses inlet air to charge the two stroke power cylinder of the opposing paired cylinder. 
     At opposite ends of the power cylinder and at the bottom of the stroke, one of the power pistons  1  actuates an inlet port  8   b  and the stepped power piston  2  actuates an exhaust port. The ports are configured such that exhaust port  8   a  opens slightly before inlet port  8   b . On the opposite side of wobbleplate  9 , stepped piston  2  opens an inlet port  6  from the carburetor at the bottom of it&#39;s stroke. At the top of it&#39;s stroke there is an always open outlet port  5  leading into a transfer passage  7  that connects with inlet port  8   b  of the power piston it pressurizes. 
     The stepped piston  2  pressurizes the inlet air to charge the power cylinder of its paired cylinder. When the power piston&#39;s inlet port  8   b  has opened for inlet, at the bottom of the stroke, the stepped piston  2  opposite is at the top of it&#39;s stroke, having compressed the fuel/air mixture. 
     The stepped charging piston  2  of one cylinder pressurizes the power cylinder of its paired cylinder. Accordingly, each stepped piston  2  moves in the opposite direction from its paired power piston  1 . The stepped piston can be large enough to produce more piston displacement than the power piston&#39;s displacement producing excess air for supercharging. 
     Intake port  5  is an input to the power cylinder by transfer passage  7 , and the stepped charging cylinder comprises intake port  6  from a carburetor. Transfer passage  7  connects the charging cylinder to a port  8   b  of the power cylinder. The cylinder block further includes two split radial shaft main bearings  18 , a cooling water jacket  21 , a starter ring gear  22 , an accessory drive gear  23 , end housings  24 , a split bore  26  in cylinder block  25  to assemble power shaft  13  into it&#39;s main bearings, spark plug bore  27 , a shaft thrust bearing  17 , and an oil feed bearing  29 . 
     The pistons disposed within each power cylinder include a power piston  1  and a combination power piston and stepped charging piston  2 . Connecting rods  14  connect each piston  1 ,  2  to wobbleplates  9  via carden type two-pin universal joints at both ends of the connecting rod  14 . Because all of the pins handle the same load, the diameter of the pins is determined by the diameter of the piston wrist pins. Unlike a crankshaft connecting rod that experiences a violent lateral oscillation due to rotation of the crank, the connecting rods  14  do not need to be of the strong I-beam shape of crankshaft connecting rods. Accordingly, in one embodiment, connecting rods  14  are comprised of lightweight tubes having thick ends, the ends flattened and bored, wherein the hole for the pin goes through the thicker part of the flattened rod end. No welding or riveting is required. 
     As disclosed herein, wobbleplate  9  eliminates the need of piston rollers of previous wobbleplate designs and is designed according to a fatigue life determined by factors including the material used, stress in the shaft, and the number of its cycles experienced in its lifetime. Stress is based upon the value of the bending moment, caused by the spread of main bearings  18  between wobbleplates  9  and the offset of the connecting rods  14  from the shaft center and the number of cycles experienced. The greater the bearing spread, the higher the bending moment value. 
     Wobbleplates  9  are restricted from rotating and receive force from each piston  1 ,  2  equally spaced around the periphery of wobbleplate  9  by a connecting rod  14  having swiveled ends that cause wobbleplate  9  to wobble, thereby transferring the piston&#39;s reciprocating motion into rotary motion of power shaft  13 . 
     Each wobbleplate  9  is mounted via wobbleplate mounting bearing  10  to a slug  11  with a skewed bore, and is configured to transfer reciprocating motion from pistons  1 ,  2  into rotary motion of power shaft  13  passing through slug  11 . Pin  12  secures slug  11  to power shaft  13 . Connecting rod  14  includes hinged ends mounted to hinged double pin carden joints. The hinged connection  15  of wobbleplate  9  to the connecting rod  14  allows angular motion of connecting rod  14  at the wobbleplate  9 . Hinged carden joint  16  includes a piston wrist pin. 
     Wobbleplates  9  are non-rotating. In the embodiment illustrated in  FIG. 1 , anti-rotator rod  19  is fixed to, and extends radially from, the periphery of each wobbleplate  9 . Non-limiting, wobbleplate  9  is prevented from rotating by a pair of fixed planar members  20  straddling the anti-rotator rod  19 , the straddling members lying in planes parallel to the centerline of power shaft  13  and anchored to frame  25  of engine  100 . As wobbleplate  9  rocks, anti-rotator rod  19  slides always parallel to the centerline of power shaft  13  preventing wobbleplate  9  from rotating. 
       FIG. 2  illustrates another embodiment of an anti-rotator device wherein rotation of each wobbleplate  9  is prevented by a rotatable yoke  29  having at least one of its ends pivoted 90 degrees around a rotation restraint pin  31  mounted to the outside of wobbleplate  9 , and at least one other end of yoke  29  connected to frame  25  via attachment pin  30 . Rotation restraint pin  31  is configured to swivel into yoke  29 , allowing yoke  29  to rotate, while preventing the rotation of wobbleplate  9 . 
     Rotation restraint pin  31 , mounted to the periphery of wobbleplate  9 , oscillates, following the angle of wobbleplate  9  twice every revolution of shaft  13  as pin  31  slides back and then forth with the wobble. Furthermore, rotation restraint pin  31  carries the load of wobbleplate  9  from connecting rods  14 . Accordingly rotation restraint pin  31  is preferably lubricated by the surrounding load-carrying bushings. 
     In one embodiment, shaft  13  is hollow and contains oil under pressure. A groove disposed all the way around the inside of bearing  29  allows oil to flow from skewed slug  11  through wobbleplate  9  to rotation restraint pin  31  or anti-rotator rod  19 . 
     In an alternate embodiment, a non-wobbling oil disc  28  is mounted on power shaft  13  between the wobbleplate  9  and the cylinder block. Unlike oil being dispersed from wobbleplate  9 , non-wobbling oil-disk  28  has an advantage of directing oil into the cylinders with greater accuracy without squirting oil in a trajectory determined by the wobble.