Abstract:
A system for driving a water induction and discharge system of a watercraft propelled by a water jet includes a water impeller, an engine including a driven shaft and a first chamber for containing engine oil, a second chamber for containing engine oil, a pinion secured to the driven shaft and located in the second chamber, a gear located in the second chamber, engaged with the pinion and driveably connected to the water impeller, and a dam located in the second chamber for limiting oil flow across the dam into the oil contained in the second chamber.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a watercraft propelled by a water jet, and in particular, to an internal combustion engine for driving the propulsion system of such a watercraft. 
     2. Description of the Prior Art 
     A jet-boat is a boat propelled by a jet of water ejected from the back of the craft. Unlike a powerboat or motorboat that uses a propeller in the water behind the boat, a jet-boat draws the water from under the boat into a pump-jet inside the boat, then expels the injected water through a nozzle at the stern. 
     Jet-boats are steered and maneuvered by directing the nozzle and water jet laterally from the axis of longitudinal direction, whereby the jet both propels and steers the craft. Jet boats can be reversed and brought to a stop within a short distance from full speed using the jet. 
     A conventional screw impeller accelerates a large volume of water by a small amount, similar to the way an airplane&#39;s propeller accelerates a large volume of air by a small amount. In a jet-boat, pumping a small volume of water, accelerating it by a large amount, and expelling the water above or below the water line delivers thrust that propels the craft. Acceleration of the water is achieved by the impeller driven by a small internal combustion engine (ICE) onboard the craft. 
     SUMMARY OF THE INVENTION 
     The engine includes a crank shaft, a first chamber for containing engine oil and, a second chamber for containing engine oil, a gear secured to the crankshaft, and a mating gear secured to an output shaft connected to the water impeller though a coupling. A dam, located in the second chamber, limits oil flow across the dam into the oil contained in the second chamber, 
     The oil flows from the first chamber to the second chamber through an orifice, providing lubrication to the gear set in the second chamber. The rotating gear brings the oil in the lower portion of second chamber into the higher position behind the dam. The orifice limits the amount of oil flow from the first chamber to the second chamber. As the gear rotates, it carries the oil from the lower portion of second chamber to the higher portion of the second chamber behind the dam so that the gear is not submerged in oil. 
     The dam prevents oil from flowing back from the higher portion to the lower portion in the second chamber. Another orifice permits engine oil, located behind the dam, to flow back to the first chamber. The dam and orifice operate to keep the gear lubricated without being submerged in oil, and maintain an optimum height of the oil level for lubricating the gear properly. Lubrication protection is not at its best when gears are submerged in oil. 
     The correct level of oil in the second chamber, provided by the orifices and dam, also limits energy losses due to hydraulic drag on the gear as it rotates in the oil compared to the drag loss that would otherwise occur if the oil level were high in the second chamber. Hydraulic drag on the gear increases the magnitude of external load on the engine, potentially reduces the operating efficiency of the engine. 
     The system also provides a continuous supply of lubricant to the pinion, bear, shafts and bearings. As the gear rotates, oil in the second chamber is thrown radial outward in a mist onto the surfaces of the pinion and gear. An orifice, formed through wall  56 , is sized to permit engine oil to flow at an acceptable rate from the first chamber into the second chamber  76 , thereby replenishing oil that has been carried away as the pinion rotates through the oil in the second chamber. 
     The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional side view of an engine-powered kayak showing the water induction system and engine; 
         FIG. 2  is partial cross section side view of the engine and water induction system shown in  FIG. 1 ; 
         FIG. 3  is an end view of the engine view of the engine shown in  FIG. 1 ; and 
         FIG. 4  is a side view, partially in cross section, of the engine exhaust gas system. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a kayak  10  includes a sealed hull portion  12  covered with a seamless molded plastic skin, the hull being formed with a recess  14  on its upper surface  15 , in which recess the rider sits facing forward with legs straddling a manually-operated control lever  16  (called a joystick) and feet supported on foot rests. The volume of hull  12  between its upper deck  15  and its bottom surface  17  is filled with a core material  20  that reinforces, strengthens and stiffens the hull. The core  20  may be expandable, cellular molded foam or a hollow, hexangular honeycomb whose walls are of Kevlar or a similar synthetic material. Alternatively, the core may be machined foam. The hull portion  12  is sealed, thereby preventing entry of water from waves or spray and making it possible to roll the kayak upright again following a tip over without it filling with water. 
     A seat back  22 , secured to the upper surface of the hull  12  supports the seated rider. The core-reinforced portion of the hull  12  is closed by a partition or bulkhead  24 , located at the forward end of an engine compartment  26 , which contains an engine  28 , water intake duct  30 , bladed impeller  32  that forces water from the intake duct, and a nozzle  34 , whose angular position about a vertical axis can be varied leftward and rightward to steer the kayak  10 . Water inducted through duct  30  flows through the impeller and exits through the nozzle  34 . The engine compartment  26  is covered with a cowling  36  formed with an air inlet passageway  38 . Cowling  36  is secured by latches to the upper surface of the hull, thereby sealing the engine compartment against entry of water when the cowling is latched to the hull. Preferably, engine  28  has a single cylinder and piston, low displacement and operates at high efficiency on a four stroke cycle. 
     The intake duct  30 , which may be a component separate from the hull  12  or formed integrally with the hull, is of molded plastic having an intake opening  44  in the bottom of the hull, through which water is inducted and flows toward the outlet of nozzle  34 . A driveshaft  46 , secured to the crankshaft of engine  28  drives the bladed impeller  32  in rotation, thereby drawing water into the intake duct  30  and forcing it through the impeller and out the nozzle  34 . A water jet, which propels and steers the kayak  10 , rises from the outlet of nozzle  34  into the air above the water surface. 
     The rider pivots the joystick  16  leftward and rightward about an axis to steer the craft  10 . The joystick  16  carries a button, which is depressed to start engine  28 , a button that stops the engine, and an engine throttle in the form of a trigger  64  located on the underside of the joystick, by which the engine throttle is opened and closed to control engine speed and speed of the kayak  10 . 
     The rider also pivots the joystick  16  upward and downward about axis  49  to locate its hand grip in a comfortable position during use and in a downward position when the craft  10  is stored or being transported. As the joystick  16  pivots, cables supported on pulleys transmit movement of the joystick to the nozzle  34 , thereby steering and maneuvering the kayak leftward and rightward by redirecting the water jet exiting the nozzle relative to the longitudinal axis of the craft. 
       FIG. 2  shows that the exhaust system for engine  28  includes an exhaust pipe  50 , which carries exhaust gas from the engine in a path that is directed upward and then downward to prevent water from entering the engine. 
     The output shaft  52  of engine  28  is supported by anti-friction bearings  54 ,  55  on a wall  56  formed in the engine casing  58 . Shaft  52  is secured to driveshaft  46  of the water intake and discharge system. Output shaft  52  is secured to an output gear  60 , which is in continuous meshing engagement with a pinion gear  62 , supported on the engine crankshaft  66 . Bearing  68 , fitted in the wall  56  of the engine casing  58 , and bearing  69  support crankshaft  66 . 
     Engine casing  58  is formed with a first oil chamber  70 , which normally contains engine lubricating oil at about level  72 . A dipstick  74 , threaded into an exterior wall of casing  58 , can be removed to visually check the level of oil in the first oil chamber  70 . Wall  56  separates the first chamber  70  from a second oil chamber  76  having a first surface  77  that supports engine oil contained in the second chamber. Normally the upper surface of the engine oil in chamber  76  is at level  78 . Gear  60  and pinion  62  are located in chamber  76 , and the teeth of gear  60  rotate through the oil in chamber  76  as gear  60  is driven by pinion  62  in rotation about axis  79 . 
       FIG. 3  shows the wall  56  of engine  28  with the cover  80  removed. The engine is supported on the kayak  10  at engine mounts  82 ,  83 , and cover  80  is secured to the engine casing  58  at a series of bolt holes  84  spaced about the periphery of cover  80 , which is shown in-place in  FIG. 2 . A valve cover  88  is secured to the top of a combustion cylinder  96  supplied with air through cowling  36  and duct  92 . A spark plug  94  is fitted on the wall of the combustion cylinder  96 , in which a piston (not shown) reciprocates and drives shaft  66  in rotation. 
     As gear  60  rotates, oil in chamber  76  is thrown radial outward in a fine mist against the inside of cover  80 , onto the surfaces of pinion  62  and gear  60 , and against wall  56 . An orifice  100 , formed through wall  56 , is sized to permit engine oil to flow at an acceptable rate from chamber  70  into chamber  76 , thereby replenishing oil in chamber  76  that has been carried away as pinion  60  rotates through the oil in chamber  76 . 
     A partition or dam  102 , supported on wall  56 , is located in second chamber  76  on a second surface  103  that is located above the surface  78  of oil contained in chamber  76 . Dam  102  limits oil, which may collect in a space  104  behind the dam and at the outboard side of wall  56 , from flowing from surface  103  into the oil contained in chamber  76  and above surface  78 . An orifice  105  formed through wall  56  permits engine oil in space  104  to flow through wall  56  into chamber  70 . Dam  102  and orifice  105  operate to limit the height of the oil level  78  contained in chamber  76 , thereby providing the best lubrication protection. Lubrication protection is not at its best when gears are submerged in oil. Hydraulic drag on gear  60  increases the magnitude of external load on engine  28  and potentially reduces the operating efficiency of the engine. 
     A window  106  formed in wall  56  provides a passageway to circulate any oil mist between chambers  70  and  76 . 
       FIG. 4  illustrates details of the exhaust system of the engine  28  for preventing water from entering the engine. The exhaust pipe  50 , which is secured at one end to an exhaust port  120  of the engine  28 , is in the form of a double walled tube that includes an outer tube  122 , an inner tube  124 , an annular passage  126  between the tubes  122 ,  124 , and an inner passage  128 . The annular passage is closed at its end nearest the exhaust port  1   20 . The annular passage  1   26  carries water, which enters passage  126  from a water body, preferably the lake or stream in which the watercraft  1   0  is operating, through an orifice  1   30 , which is located below the waterline  132  of the watercraft. Engine exhaust gas enters passage  128  from port  120  and is pumped by the engine to the opposite end  134  of tubes  122  and  124 . There, the exhaust gas produces a high speed gas jet exiting passage  128 . The gas jet operates to draw water from annular water passage  126 . The water and exhaust gas combine into a mixed stream that flows into a water box  136 , which is partially submerged below the waterline  132 . Water and engine exhaust gas are pumped by the engine exhaust from the water box  136  through a pipe  138  having an opening  140 , through which the water and exhaust gas exit the system and flow into the water body. 
     The water flowing in annular passage  126  cools the tube  122  and provides a low temperature water jacket around the inner exhaust gas tube  124 . The exhaust pipe  50  is directed upward from outlet port  120  above the waterline  132 , and then downward below the waterline down. This upward and downward path blocks water from entering the engine exhaust port  120  and cylinder head. 
     In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.