Abstract:
The support structure for an outboard motor provides a connection bar between an engine support structure and a steering structure. A tubular outer member is spaced apart from the attachment bar and connected to the attachment bar with an elastomeric member. Vibration isolation and consistency of deformation is achieved through the interaction of the individual elements of the structure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally related to a mount system for an outboard motor and, more particularly, to a mount system that incorporates an elastomeric member disposed between an inner attachment bar and a tubular outer member. 
     2. Description of the Related Art 
     Those skilled in the art of marine propulsion systems and, more particularly, outboard motors are aware of many different types of mounting systems that use resilient members to absorb vibration and dampen shock loads to prevent the transfer of noise and vibration from the engine of the outboard motor to the marine vessel to which it is attached. 
     U.S. Pat. No. 5,180,319, which issued to Shiomi et al. on Jan. 19, 1993, describes a joint structure with an elastic mount. The joint structure joins an outboard motor assembly to a boat hull. The outboard engine assembly has an engine, a case, a propeller rotatably supported on the case and drivable by the engine. The joint structure includes an attachment adapted to be coupled to the boat hull, the case having an inner surface defining an inner housing region, and elastic mount mechanism accommodated in the inner housing region for elastically supporting the case to the attachment. 
     U.S. Pat. No. 6,354,893, which issued to Sato on Mar. 12, 2002, describes a mounting structure for an outboard motor. The axis of a driveshaft is disposed at a position offset away from the axis of a crankshaft of an engine by a small amount to the rear of the outboard motor. A pair of left and right mount holders are formed adjacent to the center of gravity of the outboard motor within the engine holder. The mount units are inserted into mount holders from the front side of the engine holder. The driveshaft is inserted between the mount holders and the mount holders are formed as close as possible to a protective wall for the driveshaft so that the mount holders can clear the protective wall. 
     U.S. Pat. No. 6,390,863, which issued to Imanaga on May 21, 2002, describes an outboard motor which incorporates a mount unit including upper and lower mount devices for mounting the outboard motor to the hull and a bracket through which the upper and lower mount devices are mounted to the hull. It also incorporates an elastic thrust stopper disposed between the bracket and a body of the outboard motor and a propeller driven in accordance with the engine operation. The distance between an axis of the upper mount device and an axis of the elastic thrust stopper both extend in a direction parallel to an axis of the propeller. 
     U.S. Pat. No. 6,419,534, which issued to Helsel et al. on Jul. 16, 2002, discloses a structural support system for an outboard motor. The support system uses four connectors attached to a support structure and to an engine system for isolating vibration from being transmitted to the marine vessel to which the outboard is attached. Each connector comprises an elastomeric portion for the purpose of isolating the vibration. Furthermore, the four connectors are disposed in a common plane which is generally perpendicular to a central axis of a driveshaft of the outboard motor. Although precise perpendicularity with a driveshaft axis is not required, it has been determined that if the plane extending through the connectors is within forty-five degrees perpendicularity with the driveshaft axis, improved vibration isolation can be achieved. A support structure, or support saddle, completely surrounds the engine system in the plane of the connectors. All of the support of the outboard motor is provided by the connectors within the plane, with no additional support provided at a lower position on the outboard motor driveshaft housing. 
     The patents described above are hereby expressly incorporated by reference in the description of the present invention. 
     SUMMARY OF THE INVENTION 
     A support mechanism for an outboard motor, made in accordance with a preferred embodiment of the present invention, comprises an attachment bar having a first portion and a second portion. The attachment bar has a central axis and the first portion is attachable to a steering structure. A tubular outer member is spaced apart from the second portion of the attachment bar and disposed in generally coaxial relation with the attachment bar. An elastomeric member is attached to the tubular outer member and to the attachment bar. The tubular outer member is attachable to an engine support structure of the outboard motor. The tubular outer member is configured to attach the second portion of the attachment bar to the engine support structure in response to a compressive force being exerted on the tubular outer member in a direction parallel to the central axis of the attachment bar and against a surface of the engine support structure. 
     In a preferred embodiment of the present invention, the first portion of the attachment bar comprises a rod which is attachable to the steering structure and the second portion of the attachment bar comprises an extension member attached to the rod. The extension member is attached to the elastomeric member. A threaded member is configured to be received in threaded association with a threaded opening in the engine support structure and to exert the compressive force on the tubular outer member in the direction parallel to the central axis of the attachment bar and against the surface of the engine support structure. 
     In a preferred embodiment of the present invention, the support mechanism further comprises a spacer which is disposed axially between the tubular outer member and the threaded member and a retaining device is associated with the attachment bar. The retaining device, which can be a washer, and the spacer are shaped to prevent the attachment bar from passing through the spacer in the event that the elastomeric member is damaged. The preferred embodiment of the present invention can further comprise a pin extending from the attachment bar in an axial direction. The pin is shaped to be received in a hole formed in the steering structure. It facilitates installation of the present invention in an outboard motor. 
     The tubular outer member and the elastomeric member are configured to respond to a radially inward force exerted on the tubular outer member with radial compression of the elastomeric member between the attachment bar and the exerted radial force in combination with radial tension of the elastomeric member on a side of the attachment bar which is radially opposite to the exerted radial force. The tubular outer member, the attachment bar and the elastomeric member are configured to respond to an axial force exerted on the tubular outer member, relative to the attachment bar, with a shear reaction within the elastomeric 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  is a section view of a preferred embodiment of the present invention; 
         FIG. 2  shows the present invention associated with a steering structure and an engine support structure, in section view; and 
         FIG. 3  is an exploded isometric view of the present invention associated with a steering structure and an engine support structure. 
     
    
    
     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 the support mechanism  10  of a preferred embodiment of the present invention. An attachment bar  12  has a first portion  14  and a second portion  16 . The attachment bar  12  has a central axis  18 . The first portion  14  is attachable to a steering structure which will be described in greater detail below in conjunction with  FIGS. 2 and 3 . 
     A tubular outer member  20  is spaced apart from the second portion  16  of the attachment bar  12  and disposed in generally coaxial relation with the central axis  18  of the attachment bar  12 . An elastomeric member  24  is attached to the tubular outer member  20  and to the attachment bar  12 . The tubular outer member  24  is attachable to an engine support structure which will be described in greater detail below in conjunction with  FIGS. 2 and 3 . 
     The tubular outer member  20  is configured to attach the second portion  16  of the attachment bar  12  to the engine support structure in response to a compressive force exerted on the tubular outer member  20  in a direction parallel to the central axis  18  of the attachment bar  12  and against a surface of the engine support structure. This compressive force is represented by the arrows C in  FIG. 1 . 
     With continued reference to  FIG. 1 , the first portion  14  of the attachment bar  12  comprises a rod which is attachable to the steering structure. The threads  30  facilitate this attachment. The second portion  16  of the attachment bar  12  comprises an extension member which is attached to the rod of the first portion  14 . The extension member of the second portion  16  is also attached to the elastomeric member  24 . 
     As illustrated in  FIG. 1 , the first portion  14  of the attachment bar  12  is threaded, with threads  34 , into the extension member which is the second portioned  16  of the attachment bar  12 . 
     A threaded member  40 , which can be a spanner nut, is configured to be received in threaded association with a threaded opening in the engine support structure. This relationship will be described in greater detail below. The threaded member  40  exerts the compressive force, represented by the arrows C in  FIG. 1 , on the tubular outer member  20  in a direction which is generally parallel to the central axis  18  of the attachment bar  12  and against a surface of the engine support structure. 
     With continued reference to  FIG. 1 , a spacer  44  is disposed between the tubular outer member  20  and the threaded member  40 . A retaining device  46 , such as a washer, is associated with the attachment bar  12 . The retaining device  46  and the spacer  44  are shaped to prevent the attachment bar  12  from passing axially through the spacer in the event that the elastomeric member  24  is damaged. In other words, if a force is exerted on the attachment bar  12  in a direction toward the left in  FIG. 1  or if a force is exerted toward the right in  FIG. 1  on the spacer  44 , the retaining device  46  will not permit the attachment bar  12  to pass completely through the opening  50  provided within the structure of the spacer  44  even if the elastomeric member  24  is damaged. In other words, the washer, or retaining device  46 , cannot move toward the left in  FIG. 1  relative to the spacer  44  by a sufficient distance to allow separation between the attachment bar  12  and the engine support structure to which the threaded member  40 , the spacer  44 , and the tubular outer member  20  are attached. This retention of the engine support structure to the steering structure is therefore not dependent on the continued integrity of the elastomeric member  24 . 
     With continued reference to  FIG. 1 , a pin  56  extends from the second portion  16  of the attachment bar  12  in an axial direction (i.e. generally parallel to central axis  18 ). The pin  56  is shaped to be received in a hole formed in the steering structure (not shown in  FIG. 1 ) to prevent rotation of the attachment bar  12  during installation and attachment to the steering structure. The retaining device  46 , which is a washer in a preferred embodiment of the present invention, is also provided with a hole, as shown in  FIG. 1 , that allows the pin  56  to extend therethrough so that the pin can be received in a hole formed in the steering structure. 
     The tubular outer member  20  and the elastomeric member  24  are configured to respond to a radially inward force F exerted on the tubular outer member  20  with radial compression of the elastomeric member  24  between the attachment bar  12  and the exerted radial force F. In other words, the region of the elastomeric member  24  identified by reference numeral  60  experiences radial compression when the radially inward force F is exerted on the tubular outer member  20 . Simultaneously, the region of the elastomeric member  24  identified by reference numeral  62  experiences tension. This results from the fact that the tubular outer member  20  and the second portion  16  of the attachment bar  12  are bonded to the elastomeric member  24 . When the radially inward force F is exerted on the tubular outer member  20 , it radially compresses region  60  and radially expands region  62 . 
     With continued reference to  FIG. 1 , the tubular outer member  20 , the attachment bar  12  and the elastomeric member  24  are configured to respond to an axial force exerted on the tubular outer member  20 , relative to the attachment bar  12 , with a sheer reaction within the structure of the elastomeric member  24 . In other words, if an axial force toward the left in  FIG. 1  is exerted on the attachment bar  12  and an axial force toward the right in  FIG. 1  is exerted on the tubular outer member  20 , these opposing axial forces are resisted by the elastomeric member  24  which experiences shear within its structure. These opposing axial forces are not resisted by the elastomeric member  24  acting in either compression or tension. Significant improvements in consistency of operation result from this structure. 
       FIG. 2  is a section view of the support mechanism of the present invention associated with a steering structure  70  and an engine support structure  72 . The spacer  44  is shown compressed between the threaded member  40  and the tubular outer member  20 . This axially compresses the tubular outer member  20  between the spacer  44  and a surface  74  within the engine support structure  72 . The threaded member  40 , the spacer  44 , the elastomeric member  24 , and the surface  74  cooperate with each other to attach the second portion  16  of the attachment bar  12  to the engine support structure  72 . The first portion  14  of the attachment bar  12  is attached to the steering structure  70  by passing the first portion  14  through an opening formed in the steering structure  70  and retaining the first portion  14  in position with a threaded component, such as the nut  78 . It can be seen in  FIG. 2  that the connection between the steering structure  70  and the engine support structure  72  is through the elastomeric member  24 . As described above, the radially and axial forces exerted by the engine support structure  72  are all transmitted through the elastomeric member  24  which dampens their effect on the steering structure  70  and the marine vessel to which it is attached. For reference, a steering axis  80  is shown in  FIG. 2 . 
       FIG. 3  is an exploded isometric view of the present invention associated with a steering structure  70  and an engine support structure  72  of an outboard motor. Although not shown specifically in  FIG. 3 , those skilled in the art of marine propulsion systems are familiar with the manner in which an engine is supported by the engine support structure  72 , or adapter plate. In  FIG. 3 , a locking mechanism  90  is associated with the threaded member  40  to prevent it from rotating about the central axis  18  and becoming loose from the engine support structure  72 . 
     With continued reference to  FIG. 3 , it should be understood that the present invention is intended to be used in pairs to attach the engine support structure  72  to the steering structure  70 . Although only a single support mechanism is shown in  FIG. 3 , it should be understood that an identically configured support mechanism would normally be provided in parallel association and disposed about central axis  19 . 
     The present invention is assembled by inserting the tubular outer member  20  into the opening identified by reference numeral  92  until the inward axial end  94  of the tubular outer member  20  moves into contact with the surface  74  of the engine support structure  72  as described above in conjunction with  FIG. 2 . The retaining device  46  and the spacer  44  are also disposed within the opening  92 . The threaded member  40  is then threaded into mating threads of the opening  92  and tightened sufficient axial force is exerted through the spacer  44  against the outer axial surface  96  of the tubular outer member  20 . This attaches the tubular outer member  20  to the engine support structure  72 . The first portion  14  of the attachment bar  12  then extends outwardly from the engine support structure  72 . It is inserted through a hole  100  within the steering structure  70  and the nut  78  is used to attach the attachment bar  12  to the steering structure  70 . A similar support mechanism is attached to the engine support structure  72  in relation to opening  104  and aligned with central axis  19 . 
     Although the present invention has been described in considerable detail and illustrated with specificity, it should be understood that alternative embodiments are also within its scope.