Patent Publication Number: US-2007123119-A1

Title: Outboard motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation of my co-pending application Ser. No. 11/156,184 filed on Jun. 20, 2005, which is a continuation of application Ser. No. 10/389,157 filed on Mar. 14, 2003, entitled “Outboard Motor,” now U.S. Pat. No. 6,921,305, the full disclosures of which are incorporated by reference herein and priority of which is hereby claimed. 
    
    
     BACKGROUND OF THE INVENTION  
      This invention relates to outboard drive units and, more particularly, to a drive unit for use with a watercraft, such as a pleasure boat.  
      Conventional marine outboard drive units are supported on a transom of a boat and can be tilted about a horizontal tilt axis. When required for storage, servicing or repair, the drive units are tilted upward to raise the units above the water surface. There is no intermediate tilting position during operation of a watercraft; conventional outboard motors are submerged during operation below the water surface.  
      The majority of outboard motors are equipped to run in the water. A special category of outboard motors is designed to run in muddy waterways, in shallow water and in the body of water that has overgrown with vegetation. In Such cases, the conventional outboard drive unit becomes almost useless, especially if vegetation wraps around the rotating portion of the propeller shaft or when the propeller shaft encounters particularly viscous or hard obstacles. There also exists a possibility of the propeller striking an underwater tree stump with a disastrous result.  
      The special category of mud propellers utilizes what is known as a “go-devil” —a special extended rod with a wide steering radius of up to 72 inches that helps raise the propeller out water or move it sideways in case of heavy obstructions. However, these types of drive units are difficult to operate and require special skill.  
      The present invention contemplates elimination of drawbacks associated with the prior art and provision of an outboard drive unit that can be tilted to extend partially above water and that would allow the watercraft to move safely in clear water as well as mud, while protecting the propeller unit.  
     SUMMARY OF THE INVENTION  
      It is, therefore, an object of the present invention to provide an outboard drive unit that can be used on a conventional watercraft, such as a pleasure boat, for operation in clean water as well as mud conditions.  
      It is another object of the present invention to provide an outboard drive unit that allows tilting of the propeller unit to partially raise the propeller blade above the water.  
      It is a further object of the present invention to provide an outboard drive unit with a propeller having high pitch as compared to conventional propeller units to facilitate trimming of the boat in muddy waters.  
      It is still a further object of the present invention to provide an outboard drive unit that has a small steering radius to facilitate control of the boat.  
      These and other objects of the present invention are achieved through a provision of an outboard drive unit for a watercraft that has an upper unit housing an engine, or motor and a lower unit carrying a propeller assembly. Interposed between the engine and the propeller assembly is an input shaft, which engages a gear assembly.  
      The gear assembly is also operationally connected to the propeller assembly; the gear assembly is a reduction gear assembly with a reduction ratio is in the order of 1.5:1, as compared to conventional mud motors having a 1:1 gear ratio. Tile reduction gear allows a propeller with a greater pitch to be rotated using the same torque value generated by the engine.  
      The outboard drive unit can be tilted to control the level of submerging of the propeller assembly in water or mud. Normally, the propeller assembly is submerged when the watercraft is stationary. During acceleration, especially in mud, the propeller encounters significant resistance from the liquid medium. By tilting the drive unit and partially elevating the propeller assembly above water, an operator can use a larger propeller with the same engine power. This design also allows to reduce the drag forces acting on the propeller, thereby increasing speed and efficiency.  
      The outboard drive unit of the instant invention has the propeller shaft oriented at an obtuse angle in relation to the input shaft. This design allows to avoid damage to the propeller when encountering grass or underwater tree stumps. The drive unit has a steering radius of less than 20″, more precisely about 16″, which is a significant improvement in maneuverability as compared to conventional “go devil” designs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Reference will now be made to the drawings, wherein like parts are designated by like numerals, and wherein  
       FIG. 1  is a perspective view of the outboard drive unit of the present invention as mounted on a boat.  
       FIG. 2  is an exploded view of the steering and propeller portion of the outboard motor of the present invention.  
       FIG. 3  is a schematic view of the outboard drive unit of the present invention in a position stationary in water.  
       FIG. 4  is a schematic view showing the boat as it accelerates in water, with a cavitation plate of the propeller unit being completely submerged under water.  
       FIG. 5  is a schematic view illustrating the watercraft with an outboard drive unit of the present invention when the boat is completely on plane in either mud or water.  
       FIG. 6  is a schematic view illustrating position of the boat and the outboard drive unit of the present invention when the boat accelerates on mud.  
       FIG. 7  is a schematic top view of a watercraft with an outboard drive unit of the present invention illustrating steering radius from at the steering pivot point and propeller.  
       FIG. 8  is a schematic top view of a watercraft with an outboard drive unit of the present invention illustrating steering radius from the steering pivot point and propeller.  
       FIG. 9  is a perspective view of a propeller blade of the outboard drive unit of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Turning now to the drawings in more detail, numeral  10  designates the outboard drive unit of the present invention. The outboard motor  10  comprises an upper unit, or power head  12 , a drive shaft housing  14  and a lower unit  16 . The power head  12  includes an internal combustion engine (not shown) of a conventional design, for instance and inline two-cylinder motor that operates on a four-stroke combustion principle.  
      Similarly to conventional engines, the engine employed in the design of the present invention has reciprocating cylinders moving within combustion chambers and moving a crank shaft or drive shaft. The drive shaft transmits rotational force to the lower unit  16  through an input shaft  20 .  
      The engine  12  is connected to a fuel supply system (not shown) that supplies a fuel charge to the combustion chambers to allowing damning of the fuel an exhaust of gases out of the combustion chambers. Although not shown, it is within the knowledge of those skilled in the art that the engine  12  is also connected to lubrication and cooling systems that are conventionally employed for operation of such type of motors.  
      The lower unit  16  comprises a support assembly  22 , which supports the drive unit  10  on the watercraft transom  24 . The support assembly  22  orients the lower unit along with the associated propeller assembly such that the propeller is submerged when the hull of the watercraft is stationary on a body of water.  
      Turning now in more detail to  FIG. 2 , the lower unit  16  is illustrated in an exploded view. As can be seen in the drawing, the lower unit is secured to the engine portion  12  with a pair of attachment plates  30 ,  32  using conventional bolts or other securing means  34 . Each bolt  34  is received in a retainer  35  that helps in retaining the plates  30 ,  32  in a parallel spaced-apart relationship to each other.  
      Mounted between the attachment plates  30 ,  32  is an electric clutch  36  resting on a drive coupling  38 . The plates  30  and  32 , as well as the coupling  38  are provided with central through openings allowing extension of a drive shaft connection therethrough. The input shaft  20  is connected to the drive shaft of the engine  12  for transmitting rotational force to a propeller shaft  40 .  
      The upper portion of the input shaft  20  is enclosed in a standoff tube  42  mounted below the lower attachment plate  32 . An upper steering bearing  44  is interposed between the stand off tube  42  and the plate  32 . A steering tube  46  houses the standoff tube  42 . A lower steering bearing  48  abuts the bottom of the standoff tube  46 . A pair of U-shaped brackets  50 ,  52  extend about the outer circumference of the steering tube  46  for engagement with the support assembly  22 . The brackets  50 ,  52  can be secured with a pair of wing nuts (shown in  FIG. 1 ) to the attachment bracket  54  of the support assembly  22 .  
      The support assembly  22  also comprises a swivel bracket  56  provided with a pair of levers  67  and a swivel bracket cross bar  68 . An internally threaded opening is formed in the cross bar  68  for receiving a distant end of a steering shaft  58  therethrough. A pair of tilt pins  60  (only one is shown in  FIG. 2 ) secures the swivel bracket  56  to a Support bracket  62 . A clamp  64  with an internally threaded opening receives a proximate end of the threaded steering shaft  58 . A hand wheel  70  is secured on the proximate end of the steering shaft  58  to facilitate tilting of the drive unit, as will be explained in more detail hereinafter.  
      The support bracket  62  is fitted between the levers  67  and receives the tilt pins  60 . The clamp  64  is secured between the arms of the support bracket  62  and is attached to the support bracket cross bar  66 , as can be better seen in  FIG. 2 .  
      Secured below the lower steering bearing  48  is an upper thrust bearing  72  that is fitted, with a jam nut  74 , a spacer  76  and an upper seal  78 , into an input housing  80 . The input housing  80  also houses a distant end of the input shaft  20 . An annular flange  82  formed in the lower portion of the input housing  80  engages with a lower steering bearing  48  when the lower unit  16  is assembled.  
      Mounted below the upper thrust bearing  72  is an output thrust bearing  84 , which is mounted, together with an input gear  86  in a hub  90 . The input gear  86  is sized and shaped to mesh with an output gear  92  and provide a gear reduction in the ratio of 1.5:1 between the input shaft  20  and the propeller shaft  40 . A bearings cartridge  94  houses a proximate end of the propeller shaft  40  along with a forward thrust bearing  96  and a rear thrust bearing  98 . An internal seal, such as an O-ring  100  may be seated around the propeller shaft  40  at the point of engagement with the rear thrust bearing  98 .  
      A distant end of the propeller shaft  40  is secured in a stuffing tube  102  that carries a skeg  132  and a cavitation plate  130 . The cavitation plate  130  is oriented at about a right angle in relation to the skeg  132 . A propeller  120  is secured for rotation on the propeller shaft  40  and an end cap  134  is fitted on the distant end of the propeller shaft  40 . The design of the propeller assembly may also include a needle roller bearing  136  mounted between the end cap  134  and the stuffing tube  102 . A pair of lower seals  138  protects the needle roller bearing  136  during rotation of the shaft  40 .  
      The design of the propeller  120  can be better seen in  FIG. 9 . As shown in the drawing, the propeller  120  has a cupped area  122  and an auger portion  124 . The cupped area occupies about 110 degrees of an arcuate portion of the propeller blade. The cupped area  122  ends approximately at a point where the propeller effective blade area culminates. The angle of the cup of the propeller is about 25 degrees with a pitch of about 13 inches. Of course, these dimensions are exemplary and can be modified, depending on the torque demands of the drive unit. In the embodiment shown in  FIG. 9 , rotation of the propeller  120  covers a distance of approximately 15 inches.  
      Turning now to the mode of operation of the drive unit of the present invention, with reference to  FIGS. 3-8 , the watercraft  140  is shown floating in a stationary position in a body of water  142 . The propeller  120  and the cavtitation plate  130  are below the surface  144  of the water body  142 . As can be seen in the drawings, an axis  146  of the drive shaft is oriented at an obtuse angle to an axis  148  of the propeller shaft  40 . This arrangement is different from conventional outboard motors, where the drive shaft and the propeller shaft are arranged in a co-axial relationship.  
      When the propeller shaft  40  along with the propeller  120  is oriented to extend below the bottom of the watercraft  140 , there is a possibility of grass and other vegetation getting caught on the lower unit and cause cooling water suction that may plug and block water in the propeller. Underwater stumps present additional danger. The impact directly with the front of the lower unit causes the motor to “kick up” very hard. The traditional “go-devil” unit operating in muddy conditions is imperfect as it causes the propeller to pop out of water every time the propeller encounters mud or grass. The pivot point allows the propeller shaft to be raised while the cavitation plate remains under water in such a design. However, the shaft of the propeller tends to be pushed above the pivot point, rendering propulsion of the boat very difficult.  
      The design of the present invention utilizing the obtuse angle orientation between the axis of the propeller shaft and the input shaft minimizes or altogether eliminates this problem. The direction of the thrust force designated by numeral  150  keeps the propeller below the pivot point  152  both when the boat is stationary ( FIG. 3 ) and when the propeller shaft is raised to avoid contact with underwater obstacles ( FIG. 8 ).  
       FIG. 4  illustrates position of the boat and the drive unit  10  in water as the watercraft  140  begins its acceleration. As can be seen in the drawing, here the cavitation plate is lowered under water, with the drive unit pivoting about the pivot point  152  to lower the propeller shaft  40  deeper into the water. The cavitation plate  130  acts as a “ski” adding length to the planing surface and facilitating propulsion of the boat  140 .  
       FIG. 5  schematically illustrates position of the boat  140  when it navigates in mud or water. The propeller  120  partially extends above water and the cavitation plate  130  is exposed above the water surface  144 . The direction of the thrust force  150  is directed along the line of the propeller shaft towards the boat transom.  
      The drive unit  10  turns about the pivot point  152  by the boatman turning the wheel  70  of the attachment unit  22 . The operator can easily change the relative orientation of the steering shaft by turning the wheel  70  clockwise or counter-clockwise. By turning the wheel  70 , the operator causes the drive unit to change its relative position to the surface  144 , helping the unit to move through water or mud.  
      With the propeller partially out of the water, a larger propeller can be turned with the same engine having a pre-determined power capacity. This also means less drag in the water since a smaller portion of the lower unit is submerged. As a result the same power motor can achieve more speed and efficiency using the lower unit of the design of the present invention.  
      The present invention is particularly advantageous when the boat needs to accelerate in shallow, muddy water full of vegetation, grass, etc. Position of the propeller in such cases can be seen in  FIG. 6 . When the boat is taking off in muddy conditions, the propeller  120  is dropped below a mud line  156 . A larger propeller, with low pitch can be used thanks to the reduction gear assembly forming part of the lower unit. The larger propeller can “grab” better than a smaller propeller with conventional 1:1 gear ratio. In the position of the boat  140  as illustrated in  FIG. 6 , the cavitation plate  130  is above water, while the boat  140  accelerates in mud. After the boat takes off, the engine is trimmed to the running position, with the propeller working under normal torque conditions.  
       FIG. 7  shows the turning or steering radius from a steering pivot point provided by the design of the present invention. The steering radius designated by numeral  158  in  FIG. 7  is less than 20 inches, preferably about 16 inches. Conventional long shaft mud motors have radius of about 72 inches, making them much more difficult to turn and navigate in muddy conditions.  
       FIG. 8  illustrates position of the watercraft  140  while encountering grass  160  or an under-water tree stump  162 . The operator, observing dangerous conditions, tilts the drive unit  10 , partially lifting the propeller  120  out of water and above the water surface  144 . The direction of the thrust force  150  continues to ensure that the boat  140  is propelled, while the propeller shaft  40  is partially lifted, protecting the propeller when it encounters the grassy area  160  or underwater tree stumps  162 . The tilt angle will help deflect the outboard motor unit  10  off of the stump easier than conventional outboard motors.  
      During trim/tilt of the watercraft, the hand wheel  70  pulls on a thrust bearing. The threaded steering rod, or shaft  58  pulls the cross bar  68  moving the trim lever assembly with the levers  67 . The trim levers  67  pivot on the pin  60  and tilt the drive unit  10 . As the motor tilts, the propeller  120  is lifted.  
      Many modification and changes can be made in the design of the present invention without departing from the spirit thereof. I, therefore, pray that my rights to the present invention be limited only by the scope of the appended claims.