Patent Publication Number: US-7905205-B1

Title: 2-stroke engine crank shaft

Description:
This application claims the benefit of provisional application Ser. No. 60/961,824 filed Jul. 24, 2007. 
    
    
     BACKGROUND OF INVENTION 
     The present invention relates to a modified crank shaft for a 2-stroke engine. Crank counter weights attached to the crank shaft include peripheral grooves for directing a fuel/air mixture from the crank case toward the transfer ports of the engine cylinder resulting in increased fuel efficiency, power, and smooth operation. 
     Two-cycle engines utilizing a crank disk with a pocket for mechanically transferring a fuel charge from a crankcase to a combustion chamber is shown in U.S. Pat. No. 4,362,132 to Newman. 
     The present invention is directed to a modified crankshaft used with a two-cycle engine which continuously directs an optimized volume of fuel/air mixture from the crankcase to the combustion chamber. 
     SUMMARY OF INVENTION 
     The present invention utilizes modified counterweights attached to the crankshaft of a two-cycle engine. Two similarly shaped counterweights are conventionally attached to the crankshaft for connecting the crankshaft with a connecting rod. The counterweights of the present invention have a disk wheel shape. Each disk wheel having a rim. The rim of a first counterweight is provided with a plurality of parallel grooves arranged continuously around the circumference of the disk wheel and extend from an outer edge to an inner edge of the rim. The grooves are angularly disposed with respect to an axis of rotation of the crankshaft and in a direction against the direction of rotation of the crankshaft. 
     The rim of the second counterweight is provided with a plurality of parallel grooves arranged continuously around the circumference of the disk wheel and extend from an outer edge to an inner edge of the corresponding rim. The grooves are angularly disposed with respect to the axis of rotation of the crankshaft and in a direction against the direction of rotation of the crankshaft. 
     The grooves of the first counterweight are aligned with the grooves of the second counterweight whereby the corresponding grooves form a “V” configuration. 
     With this construction of the counterweights the grooves tangentially throw a fuel/air mixture from the crankcase toward the transfer ports of the engine cylinder. The volume of the fuel/air mixture directed to the transfer ports and the forces exerted on the fuel/air mixture being directed to the transfer ports are significantly increased thereby optimizing the fuel/air mixture delivered to the combustion chamber. The result is enhanced fuel efficiency, power and smooth operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be clearly understood and readily carried into effect, a preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings wherein: 
         FIG. 1  is an exploded view of a conventional 2-stroke engine; 
         FIG. 2  is a top view of a pair of crank counter weights which have been modified according to the present invention; 
         FIG. 3  is a cross-sectional view taken along the line  3 - 3  in  FIG. 2 ; 
         FIG. 4  is a rear elevation view of the crank counterweight shown in  FIG. 3 ; and 
         FIG. 5  is a photograph of the present invention mounted in a 2 cylinder, 2-stroke engine with parts removed. 
     
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     An exploded view of a conventional 2-stroke engine is shown in  FIG. 1 . The conventional engine includes a crank shaft A to which is secured a pair of crank counter weights B and B′. A connecting rod C is rotatably secured to the counter weights B and B′ with a pin D. The connecting rod C connects the crank shaft A with a piston E reciprocally moving with an upstroke and a downstroke into a combustion chamber F. 
     The present invention  10  is shown in  FIGS. 2 ,  3  and  4 . The present invention  2  includes a pair of crank counter weights  12  and  14  secured to the crank shaft A for rotating with the crank shaft in a direction of rotation. The counter weights  12  and  14  replace the conventional counter weights B and B′ shown in  FIG. 1 . 
     An elevational view of the counter weight  12  is shown in  FIGS. 3 and 4 . Each of the counter weights  12  and  14  have a disk wheel shape having a rim  15 . Each of the counter weights  12  and  14  have a pair of cutouts  16  and  18 , leaving a boss  20  a shown in  FIGS. 2 and 3 . The boss  20  of counter weights  12  and  14  support a pin D for rotatably supporting connecting rod C to the counter weights  12  and  14 . 
     The rim  15  of counter weight  12  has a series of parallel disposed grooves  22  as shown in  FIG. 2  which are arranged continuously around the circumferences of the disk wheel and extend from the outer edge of the rim to an inner edge of the rim. The grooves  22  are angularly disposed with respect to an axis of rotation of the crank shaft and directed against the direction of rotation. 
     Similarly the counter weight  14  has cutout portions  16  and  18  leaving a boss  20 . The rim  15  of counterweight  14  has a series of parallel disposed peripheral grooves  24  which are arranged continuously around the circumference of the disk wheel and extend from an outer edge of the rim to the inner edge of the rim. The grooves  24  are angularly disposed with respect to the axis of rotation of the crankshaft and directed against the direction of rotation. 
     Each of the grooves  22  is aligned with each of the grooves  24  whereby the corresponding grooves form a generally truncated “V” configuration on the rims  15  of counter weights  12  and  14  as shown in  FIG. 2 . 
     When the counter weights  12  and  14  are substituted for the counter weights B and B′ in a conventional 2 cycle engine, the fuel charge from a carburetor (not shown) flows into an engine crank case  27  and is caught and tangentially thrown outwardly toward transfer ports  26 , shown in  FIG. 5 , provided in the crank case  27 . The grooves  22  and  24  are disposed continuously around the exterior surface of the counter weights  12  and  14 , thus the fuel charge from the crank case  27  is continuously thrown toward the transfer ports  26 . With this arrangement, fuel efficiency, power and smooth operation is significantly enhanced. 
     While the fundamental novel features of the invention have been shown and described, it should be understood that various substitutions, modifications, and variations may be made by those skilled in the arts, without departing from the spirit or scope of the invention. Accordingly, all such modifications or variations are included in the scope of the invention as defined by the following claims: