Patent Publication Number: US-2011065340-A1

Title: Outboard motor steering structure

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally related to an outboard motor and, more particularly, to a steering structure of an outboard motor that incorporates a single piece steering arm, swivel tube, and lower yoke. 
     2. Description of the Related Art 
     Those skilled in the art of outboard motor construction are familiar with many different types of steering mechanisms that generally comprise a swivel bracket configured to support a steering mechanism for rotation about a generally vertical steering axis. The steering mechanism often comprises a tubular structure with a steering arm attached to its upper end and a lower bracket, or yoke, attached to its lower end. The tubular structure normally extends through a tubular opening formed in the swivel bracket. 
     U.S. Pat. No. 3,774,571, which issued to Shimanckas on Nov. 27, 1973, describes an outboard motor steering arrangement. The outboard motor has releasable means engageable between a kingpin and a swivel bracket for preventing relative pivotal movement between the kingpin and the swivel bracket. Releasable means can include a wrap spring. In another embodiment, the releasable means includes a series of rollers movable relative to a locking position wherein the rollers engage both the swivel bracket and the kingpin to prevent relative movement therebetween. 
     U.S. Pat. No. 3,961,595, which issued to Meyer on Jun. 8, 1976, discloses a steering apparatus for small outboard motors. A steering tiller handle assembly is attached to a driveshaft housing and pivotally mounted within a swivel mounting bracket assembly. The swivel bracket assembly includes a split tubular element within which a split tubular section of the steering arm assembly is notably mounted and located encircling a tubular portion of the driveshaft housing. Upper and lower annular rubber mounts are located between the upper and lower ends of the steering tubular section and the driveshaft housing. 
     U.S. Pat. No. 4,406,632, which issued to Blanchard on Sep. 27, 1983, describes an outboard motor with dual trim and tilt axes. A transom bracket is adapted to be fixed to a boat transom. A stem bracket has an upper end and extending downwardly from the upper end and including a first mounting arrangement located below the upper end at a first distance and second mounting arrangement located below the upper end at a second distance greater than the first distance. It also comprises a tilt pivot pivotally connecting the transom bracket and the upper end of the stem bracket for swinging movement about a horizontal axis of the stem bracket relative to the transom bracket. 
     U.S. Pat. No. 4,545,770, which issued to Ferguson on Oct. 8, 1985, describes an outboard motor mounting arrangement. It includes a transom bracket having a mounting portion fixed to the rear of a boat transom below the upper edge thereof and a pair of laterally spaced arms extending upwardly from the mounting portion and including respective upper ends located rearwardly of the boat transom and above the upper edge thereof. 
     U.S. Pat. No. 5,194,025, which issued to Blanchard et al. on Mar. 16, 1993, describes a vibration absorbing steering device for an outboard motor. The device has a swivel bracket constructed and arranged for mounting to a transom bracket and defining a vertical passageway which includes a tubular pivot shaft which is pivotally engaged in the passageway. It also includes an engine mount bracket designed to mount the engine for rotation within the pivot shaft and a vibration absorbing torque tube for absorbing vibration generated by the engine. 
     U.S. Pat. No. 5,503,576, which issued to Ming et al. on Apr. 2, 1996, describes a vibration isolation means for an outboard motor. The outboard motor comprises means adapted for connection to a boat transom and includes a swivel bracket having a king pin bore. It also includes a propulsion unit having a power head including an internal combustion engine. It has a lower unit fixed to the power head and including a driveshaft having a vertically extending axis. It is driven by the engine and adapted to drive a propeller. A forwardly facing surface is located on the propulsion unit in forwardly spaced relation to the driveshaft axis. A king pin extends in the king pin bore and includes an upper end. A steering arm is connected to the upper end of the king pin for rotation in common with the king pin. 
     U.S. Pat. No. 6,200,175, which issued to Natsume on Mar. 13, 2001, describes a mounting arrangement for an outboard motor. A swivel bracket and clamping brackets have interengaging sliding surfaces that take side thrusts and minimize loading on the tilt pin during trim operation. In addition, certain electrical cables and hydraulic conduits are juxtaposed to the steering shaft and mounted so that they pass through the various brackets in a location close to the various pivotal axes to minimize flexure and reduce the necessary length therefore. 
     U.S. Pat. No. 6,276,977, which issued to Treinen et al. on Aug. 21, 2001, discloses an integrated hydraulic steering actuator. The actuator is provided for an outboard motor system in which the cylinder and piston of the actuator are disposed within a cylindrical cavity inside a cylindrical portion of a swivel bracket. The piston within the cylinder of the actuator is attached to at least one rod that extends through clearance holes of a clamp bracket and is connectable to a steering arm of an outboard motor. The one or more rods attached to the piston are aligned coaxially with an axis of rotation about which the swivel bracket rotates when the outboard motor is trimmed. As a result, no relative movement occurs between the outboard motor, the rod attached to the piston of the actuator, and the swivel bracket during rotation of the outboard motor about the axis of rotation. 
     U.S. Pat. No. 7,172,476, which issued to Nakamura et al. on Feb. 6, 2007, describes an outboard motor with bracket assembly. The outboard motor includes a drive unit and a bracket assembly mounting the drive unit on an associated watercraft. The bracket assembly includes a swivel bracket that carries the drive unit for pivotal movement about a steering axis that extends generally vertically and a clamping bracket that supports the swivel bracket and the drive unit for pivotal movement about a tilt axis that extends generally horizontally. Either the swivel bracket or the clamping bracket, at least in part, has a first flange, a second flange spaced apart from the first flange, and a web that extends between the first and second flanges to connect together the first and second flanges. 
     U.S. Pat. No. 7,267,587, which issued to Oguma et al. on Sep. 11, 2007, describes a steering system of an outboard motor. A swivel bracket can be attached to a transom plate of a watercraft by means of a clamp bracket. A steering bracket can be rotationally provided in a swivel shaft of the swivel bracket. An outboard motor body can be secured to the steering bracket. An electric motor can be housed in the outboard motor and engaged with a stationary gear secured to the swivel bracket by way of a reduction gear. Driven by the electric motor, the steering bracket turns relative to the swivel bracket, causing the outboard motor body to turn. 
     The patents described above are hereby expressly incorporated by reference in the description of the present invention. 
     As described above, those skilled in the art of outboard motors are familiar with many different systems and procedures for steering the outboard motor. Most typically, a steering tube is supported for rotation about a generally vertical steering axis and torque is applied to the steering tube by a steering arm attached to its upper regions. The steering tube is connected, typically at two vertically spaced positions, to the main body of the outboard motor at its engine location and at a position on the driveshaft housing. This arrangement has been used for many years to allow the steering arm to be rotated and, in response, cause the engine and driveshaft housing of the outboard motor to rotate about the generally vertical steering axis which is typically coincident with a central axis of the steering tube. 
     Known arrangements for steering outboard motors can result in certain disadvantageous results. For example, when splines are used to connect the steering tube to a lower steering bracket, or yoke, the splines can involve expensive machining operations. In addition, assembly of the steering mechanism to a transom bracket can result in scratching or defacing painted surfaces that later result in corrosion. It would therefore be significantly beneficial if a rugged and less expensive steering mechanism could be provided. 
     SUMMARY OF THE INVENTION 
     An outboard motor made in accordance with a preferred embodiment of the present invention comprises a bracket which is attachable to a transom of a marine vessel, a steering mechanism that comprises a tubular member and is supported by the bracket for rotation about a generally vertical steering axis, a first bearing support structure configured to attach the steering mechanism to the bracket, and a second bearing support structure configured to attach the steering mechanism to the bracket. The first and second bearing support structures comprise first and second generally semi-circular members, respectively, which are removably attachable to the bracket with the tubular member therebetween. The bracket is shaped to cooperate with the first and second bearing support structures to define generally circular openings to capture the tubular member therein when the first and second bearing support structures are attached to the bracket. 
     In a particularly preferred embodiment of the present invention, the steering mechanism comprises an upper attachment bracket and a lower attachment bracket. The tubular member is attached therebetween. The upper attachment bracket is permanently attached to the tubular member and the lower attachment bracket is also permanently attached to the tubular member. The upper attachment bracket is configured to be attached to a support structure for an engine of the outboard motor and the lower attachment bracket is configured to be attached to a driveshaft housing of the outboard motor. In a preferred embodiment of the present invention, first and second pairs of semi-circular bearing segments are disposed between the first and second bearing support structures and the bracket. The first and second pairs of semi-circular bearing segments are disposed between the first and second bearing support structures, respectively, and the tubular member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully and completely understood from a reading of the description of the preferred embodiment in conjunction with the drawings, in which: 
         FIG. 1  shows a generally known type of steering system for an outboard motor; 
         FIG. 2  is a side view of a steering system for an outboard motor made in accordance with a preferred embodiment of the present invention; and 
         FIG. 3  is a section view of a portion of the system shown in  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Throughout the description of the preferred embodiment of the present invention, like components will be identified by like reference numerals. 
       FIG. 1  shows a steering mechanism that is generally known to those skilled in the art. A swivel bracket  10  is attached to a transom bracket (not shown in  FIG. 1 ) for rotation about a generally horizontal trim/tilt axis  12 . The swivel bracket  10  is provided with a tubular opening  16  that is shaped to receive a tubular member  20  therein. A steering arm  24  is part of an upper attachment bracket  26 . A lower attachment bracket  30  is attachable to a lower end of the tubular member  20 . In a typical application that is well known to those skilled in the art, the tubular member  20  is rigidly and permanently attached to the upper attachment bracket  22  and then the tubular member  20  is inserted in the tubular opening  16  formed in the swivel bracket. With the lower end of the tubular member  20  extending downwardly through the tubular opening  16 , the lower attachment bracket  30  is connected to the lower end of the tubular member  20 . The lower portion of the tubular member  20  is machined to have splined teeth  36  which are movable into threaded engagement with splined teeth formed on the inner portion of the lower attachment bracket  30 . In order to attach the lower attachment bracket to the splined end of the tubular member  20 , a ring  38  can be used to restrict the downward movement of the lower attachment bracket  30  relative to the tubular member  20 . This attachment is done after the tubular member  20  is inserted downwardly through the tubular opening  16  formed in the swivel bracket  10 . When torque is exerted on the steering arm  24 , that torque is transmitted to the tubular member  20  for rotation about a generally vertical steering axis which is coincident with the central axis of the tubular member  20 . It should be understood that, in order to remove the tubular member  20  from the swivel bracket  10 , the lower attachment bracket  30  must be removed from its splined connection to the lower portion of the tubular member  20 . Then, the tubular member  20  can be moved in an upwardly direction to remove it from the tubular opening  16 . 
     With continued reference to  FIG. 1 , several problems exist in conjunction with the structure shown in  FIG. 1 . First, the machining of the splined teeth  36  at the lower end of the tubular member  20  and the corresponding splined teeth within the lower attachment bracket  30  can be significantly expensive. Secondly, the lower end of the tubular member  20  must also be provided with a machined circumferential groove to accept the snap ring  38  in order to retain the lower attachment member  30  in position. Furthermore, the provision of the hole, or cylindrical opening  16 , through the length of the swivel bracket  10 , is expensive. In addition to these disadvantages, the assembly of the splined end of the tubular member  20  can result in chipping or scratching of painted surfaces. This could result in corrosion if the chipping or scratching exposes otherwise protected surfaces. 
       FIG. 2  is a side view of an outboard motor steering mechanism made in accordance with a preferred embodiment of the present invention. In a preferred embodiment, the present invention comprises a bracket  40  which is rotatable about a trim/tilt axis  42 . A steering mechanism  46  is supported by the bracket  40  for rotation about a generally vertical steering axis. 
       FIG. 3  is a section view taken through a portion of  FIG. 2 . In addition to the components illustrated in  FIG. 2 ,  FIG. 3  shows split bearing members,  81  and  82 . 
     With continued reference to  FIGS. 2 and 3 , a first bearing support structure  51  and a second bearing support structure  52  are configured to attach the steering mechanism  46  to the bracket  40 . The steering mechanism  46  comprises an upper attachment bracket  60 , a lower bracket attachment  62 , and a tubular member  64  which is attached to both the upper and lower attachment brackets. The tubular member  64  is permanently attached to both the upper and lower attachment brackets,  60  and  62 , preferably by welding. Once the steering mechanism  46  is thus constructed, the three major components of the steering mechanism cannot be separated from each other. 
     With continued reference to  FIGS. 2 and 3 , the bracket  40  is shaped to cooperate with the first and second bearing support structures,  51  and  52 , to define a generally circular opening to capture the tubular member  64  therein when the first and second bearing support structures are attached to the bracket  40 . More specifically, the bracket  40  is shaped to have two semi-circular depressions,  70  and  72 , formed therein. The first and second bearing support structures,  51  and  52 , comprise first and second generally semi-circular members,  75  and  76 , which are removably attachable to the bracket  40  with a portion, such as the tubular member  64 , disposed therebetween. 
       FIG. 3  specifically shows the second bearing support structure  52  with respect to the mating portion of the bracket  40 . A pair of semi-circular bearing segments,  81  and  82 , is held in place through the cooperation of the bearing support structures,  51  and  52 , and the bracket  40 . Bolts  88  are shown for the purpose of rigidly attaching the first and second bearing support structures,  51  and  52 , to the bracket  40 . 
     With continued reference to  FIGS. 2 and 3 , it should be understood that the tubular member  64  is first permanently attached to the upper and lower attachment brackets,  60  and  62 , prior to assembling the steering mechanism  46  to the bracket  40 . The steering mechanism  46  is then held in place, along with associated split bearings,  81  and  82 , by the attachment of the first and second bearing support structures to the bracket. Subsequent removal of the steering mechanism  46  from the bracket  40  is accomplished by removing the bolts  88  and then loosening both bearing support structures. 
     With continued reference to  FIGS. 2 and 3 , it can be seen that the upper attachment bracket  60  comprises a steering arm  90  in a manner described above. In addition, several significant advantages of the present invention, as illustrated in  FIG. 2 , can be seen. First, the lower end of the tubular member  64  requires no splined teeth. Similarly, the lower attachment bracket  62  requires no splined teeth. This eliminates two expensive and time consuming machining operations. In addition, since the lower attachment bracket  62  and the upper attachment bracket  60  are both permanently welded to the tubular member  64 , they form a unitary steering mechanism  46  that need not ever be disassembled. Accordingly, the tubular opening  16 , described above in conjunction with  FIG. 1 , is unnecessary. Therefore, that casting process that would otherwise be needed to form that opening is no longer needed. Instead, two semi-circular segments,  70  and  72 , can easily be formed in the bracket  40 . During assembly of the steering mechanism  46  to bracket  40 , it is much less likely that paint can be chipped than in the previous procedure described above in conjunction with  FIG. 1 . Similarly, no machining operation is necessary to form the circumferential groove at the bottom of the tubular member  64  that would otherwise be used to retain the snap ring  38  described above in conjunction with  FIG. 1 . 
     With continued reference to  FIGS. 2 and 3 , it can be seen that an outboard motor steering system made in accordance with a preferred embodiment of the present invention comprises a bracket  40  which is attachable to a transom of a marine vessel. It also comprises a steering mechanism  46  which comprises a tubular member  64  and is supported by the bracket  40  for rotation about a generally vertical steering axis. A first bearing support structure  51  is configured to attach the steering mechanism  46  to the bracket  40 . The first bearing support structure  51  comprises a first generally semi-circular member  75  which is removably attachable to the bracket  40  with the tubular member  64  therebetween. A second bearing support structure  52  is configured to attach the steering mechanism  46  to the bracket  40 . The second bearing support structure  52  comprises a second generally semi-circular member  76  which is removably attachable to the bracket  40  with the tubular member  64  therebetween. The bracket  40  is shaped to cooperate with the first and second bearing support structures,  51  and  52 , to define generally circular openings to capture the tubular member  64  therein when the first and second bearing support structures,  51  and  52 , are attached to the bracket  40 . The steering mechanism  46  comprises an upper attachment bracket  60  and the lower attachment bracket  62 . The tubular member  64  is attached therebetween. The upper attachment bracket  60  is permanently attached to the tubular member  64  and the lower attachment bracket  62  is also permanently attached to the tubular member  64  in a preferred embodiment of the present invention. The upper attachment bracket  60  is configured to be attached to a support structure of an engine of an outboard motor and the lower attachment bracket  62  is configured to be attached to a driveshaft housing of an outboard motor. In a preferred embodiment of the present invention, it further comprises a first pair of semi-circular bearing segments disposed between the first bearing support structure  51  and the bracket  40 . The first pair of semi-circular bearing segments is disposed between the first bearing support structure  51  and the tubular member  64 . A second pair of semi-circular bearing segments,  81  and  82 , is disposed between the second bearing support structure  52  and the bracket  40 . The second pair of semi-circular bearing segments is disposed between the second bearing support structure  52  and the tubular member  64 . 
     Although the present invention has been described with particular detail and illustrated to specifically show a preferred embodiment of the present invention, it should be understood that alternative embodiments are also within its scope.