Four-stroke internal combustion engine

Abstract

A four-stroke internal combustion engine is provided that is capable of use in many power tools, including those power tools subjected to tippable applications. There is provided within an engine housing, an oil reservoir and a valve chamber which independently communicate with a crank chamber. A system of strategically placed dividers and passageways within the engine housing appropriately directs lubricant within the engine housing so that the internal cavity of the engine is lubricated during use in any operational attitude, and so that the lubricant flows to and is held in the proper chambers during storage. There is also provided a breather arrangement for an internal combustion engine which includes a camshaft having a hollow passageway in communication with a crank chamber.

What is claimed is:  
     
         1 . A four-stroke internal combustion engine, comprising: 
 an engine housing including a crankcase and a cylinder;    a crank chamber disposed within said crankcase;    a crankshaft supported for rotation within said crank chamber;    a piston operably interconnected with said crankshaft for reciprocation within said cylinder in response to rotation of said crankshaft;    an oil reservoir disposed within said crankcase, and in fluid flow communication with said crank chamber;    an arcuate divider at least partially separating said crank chamber from said oil reservoir; and    a depending wall extending at least partially into said crank chamber to define a lubricant receiving space between said divider and said depending wall.    
     
     
         2 . An engine as set forth in  claim 1 , wherein said divider includes an opening, such that said crank chamber and said oil reservoir are in fluid flow communication through said opening.  
     
     
         3 . An engine as set forth in  claim 2 , wherein said divider further includes a second opening and a third opening, said second opening positioned substantially across from said third opening, said crank chamber and said oil reservoir being in fluid flow communication through said second and third openings.  
     
     
         4 . An engine as set forth in  claim 1 , wherein said depending wall is a cylinder side wall.  
     
     
         5 . An engine as set forth in  claim 1 , further comprising an intake valve and an exhaust valve disposed within the engine housing to the side of the cylinder, wherein said engine housing further includes a valve chamber in which said intake valve and said exhaust valve are disposed, said valve chamber being in fluid flow communication with said crank chamber.  
     
     
         6 . An engine according to  claim 1 , further comprising: 
 a cam shaft rotatably driven by said crankshaft and oriented substantially normal with respect to said crankshaft.    
     
     
         7 . An engine according to  claim 6 , further comprising first and second valve tappets associated with a respective valve and operatively engaging said cam shaft, wherein said valves are disposed substantially normal to said crankshaft.  
     
     
         8 . An engine according to  claim 6 , wherein said cam shaft has an axial passageway and a radial aperture communicating between said crank chamber and said passageway, said engine further comprising a breather tube having one end communicating with said passageway of said cam shaft and another end communicating with an air intake system of said engine.  
     
     
         9 . An engine according to  claim 1 , wherein said crankshaft is cantilevered, said crankcase includes an access hole, said piston includes an aperture, said access hole and aperture being alignable during assembly of said engine; 
 and wherein said engine further comprises:    a connecting rod having one end pivotally attached to said crankshaft and the other end pivotally connected to said piston; and    a wrist pin insertable through said access hole and into said aperture in said piston to pivotally connect said connecting rod to said piston.    
     
     
         10 . An engine according to  claim 1 , wherein said crank chamber includes at least two bearing pockets, one pocket having a larger diameter than the other and both pockets being disposed on the same side of said depending wall.  
     
     
         11 . An engine according to  claim 1 , further comprising a shroud at least partially surrounding said engine housing and including a pair of opposed channels, and a fuel tank having opposed outwardly-extending shoulders, such that said shoulders of said fuel tank are received by said respective channels of said shroud.  
     
     
         12 . An engine according to  claim 1 , wherein said engine housing further includes a back plate which is adjacent to a flywheel, and wherein said crankcase, cylinder, and back plate are cast as a single component.  
     
     
         13 . An engine according to  claim 1 , wherein said cylinder includes elliptical intake and exhaust ports on opposite sides of said engine housing, and intake and exhaust valves in communication with said intake and exhaust ports, respectively.  
     
     
         14 . An engine as set forth in  claim 1 , wherein the divider is substantially U-shaped.  
     
     
         15 . An engine as set forth in  claim 14 , wherein one side of the divider is exposed to the oil reservoir and an opposite side of the divider is exposed to the crank chamber.  
     
     
         16 . The engine of  claim 1 , wherein said cylinder defines a bore having a bore axis, and wherein said depending wall extends into said crank chamber generally parallel to said bore axis.  
     
     
         17 . The engine of  claim 1 , wherein said cylinder defines a bore, and wherein said depending wall defines an extension of said cylinder bore into said crank chamber.  
     
     
         18 . The engine of  claim 17 , wherein said bore extension and said cylinder bore have substantially the same diameter.  
     
     
         19 . The engine of  claim 18 , wherein said bore extension and said cylinder bore are substantially coaxial with each other.  
     
     
         20 . The engine of  claim 1 , further comprising a cylinder head mounted to said engine housing over said cylinder to at least partially define a combustion chamber in said cylinder, and intake and exhaust valves disposed within said engine housing.