Abstract:
A retaining member is provided and attached to a bevel gear in order to allow the bevel gear to be attached, prior to assembly, to a bearing adapter. The retaining member is provided with first and second protuberances that extend radially outwardly from diametrically opposite positions on the retaining member so that the protuberances can be inserted through first and second slots in a generally cylindrical member, or bearing adapter, during the assembly of individual components to form a subassembly. Since the bearing adapter is attached to a bearing carrier, misalignment of the protuberances and the slots allow the bevel gear and several other assorted components to be retained in contact with the bearing carrier so that the components are not free to move in axial directions away from each other to allow separation of these components. Since the individual components are retained in axial positions relative to each other and relative to the bearing carrier, insertion of this subassembly into a gearcase makes the assembly much easier than would otherwise be possible.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a structure of gears and bearings and, more particularly, to a particular structure relating to a bevel gear and a bearing adaptor which facilitates the manual assembly of the bevel gear and related thrust and roller bearings into a gearcase in combination with a bearing carrier assembly. 
     2. Description of the Prior Art 
     Those skilled in the art of marine propulsion systems are familiar with various types of gear and bearing structures contained within the gearcase of a marine propulsion system. Certain marine propulsion systems are provided with a gearcase internal assembly that is particularly configured to suit an opposite rotation of the propeller shaft. As an example, when two outboard motors are provided for use in a tandem operation on a single marine vessel, the gearing associated with the propeller shafts are selected and constructed to rotate in opposite directions. This technique is well known to those skilled in the art of marine propulsion systems. Because of the thrust forces resulting from the opposite rotation of the propeller and its shaft, the bearing arrangement in an opposite rotation marine propulsion system is designed differently than in a marine propulsion system with a conventionally rotating propeller shaft. These reverse rotating marine propulsion systems are sometimes referred to as “left hand” systems. 
     In a gearcase for an oppositely rotating propeller shaft, the bearing carrier assembly is provided with a clearance fit between the gear hub and the roller bearings. During assembly of the components into the gearcase, the bevel gear can slide out of the bearing carrier assembly because of this clearance fit and because the subassemblies are typically assembled in a direction with the axis of rotation of the bevel gears being vertical. This vertical assembly technique typically places the forward gear on the bottom of the subassembly with the bearing carrier above it. As a result of gravity and the clearance fit between the gear hub and the rollers, the bevel gear can easily separate from the bearing carrier during the assembly procedure. As a result, the assembly of the components into a gearcase for an opposite rotation marine propulsion system can be extremely difficult. Assembling the bevel gear into the other components of the bearing carrier requires precise alignment with numerous loose bearings, thrust rings, and O-rings being retained in a precise location as the components are fitted together. This difficult assembly and alignment of components increases the time necessary to assemble the marine propulsion system and, as a result, increases its cost and the likelihood that the components can be misassembled. 
     Various types of gearcase mechanisms and assemblies are known to those skilled in the art of marine propulsion systems. 
     U.S. Pat. No. 4,986,775, which issued to Wantz on Jan. 22, 1991, discloses a propeller shaft bidirectional thrust bearing system. The system for the propeller shaft of a marine propulsion system includes a substantially circumferential groove milled into the propeller shaft. A pair of substantially semicircular force transferring members are adapted for placement within the groove and front and rear bearing collars are placed adjacent the force transferring members. Front and rear needle bearings are provided adjacent the front and rear bearing collars, respectively. A front bearing adaptor, interconnected with the walls of the cavity within which the propeller shaft is disposed, transfers forward thrust to the propeller shaft in the gearcase. A rear bearing carrier, held in position by means of a ring nut mounted within the cavity, serves to transfer rearward thrust in the propeller shaft to the gearcase. 
     U.S. Pat. No. 4,897,058 which issued to McCormick on Jan. 30, 1990, discloses a marine device with an improved propeller shaft bearing carrier arrangement. A marine drive for a boat includes a construction wherein a propeller supporting bearing sleeve is disposed in a recess inside the propeller hub. A bearing carrier is concentrically associated with a propeller shaft. The carrier is provided with a rearwardly extending nose portion which is telescoped within the forwardly facing recess in an adjacent rearward propeller hub. The propeller shaft is journaled in the bearing device which is disposed between the carrier and the shaft and within the recess. In one aspect of the invention, the carrier is prevented from rotating about the shaft access. In another aspect, a sealing device is disposed between the propeller shaft and the rear end portion of an adjacent supporting gearcase. In the embodiment disclosed in this patent, dual propellers and dual bearing carriers are utilized, with bearing carrier noses disposed in recesses in both propeller hubs. 
     U.S. Pat. No. 4,373,922, which issued to Weed on Feb. 15, 1983, discloses an outboard propulsion gearcase. An outboard drive unit for a watercraft with a through-the-propeller hub exhaust system for engine exhaust has a bearing support member which carries the propeller shaft and separates the exhaust passages from the propeller shaft gears. Lubricant retaining surfaces are formed on the bearing support member to prevent corrosion between the support member and the housing. 
     The patents described above are hereby expressly incorporated by reference in the description of the present invention. 
     Although some of the specific components and structures within the gearcase of a marine propulsion system can vary from one design to another, the basic structure incorporates the same types of components. The patents described above, illustrate three examples of a gearcase structure. For example, U.S. Pat. No. 4,986,775 shows the arrangement of a bearing carrier in conjunction with thrust bearings and bevel gears for the purpose of providing a transmission for the marine propulsion system. Two bevel gears are usually provided, in opposing directions, which are continuously engaged with a bevel gear that is attached to a driveshaft. By selectively engaging either a forward or reverse bevel gear into driving relation with the propeller shaft, forward or reverse direction can be selected by the operator of a marine vessel. Thus, with a constant direction of rotation of the driveshaft, the selection of the forward or reverse bevel gears will cause the rotation of the propeller shaft to change in accordance with the position of a dog clutch that is movable by the operator of the marine vessel. When neither of the two bevel gears is engaged with the propeller shaft, the transmission is placed in a neutral gear position. 
     The basic structure of the gears and bearings within a gearcase are generally known to those skilled in the art and will not be described in significant detail below other than is necessary to describe the present invention. The structure of the internal components of a gearcase for a marine propulsion system can be significantly improved if the configuration of the components can be made to facilitate the assembly of the components into a gearcase housing, particularly in conjunction with an oppositely rotating propeller shaft. 
     SUMMARY OF THE INVENTION 
     A mechanism for a marine propulsion system, made in accordance with the preferred embodiment of the present invention, comprises a gear member having an axis of rotation and a generally cylindrical member having a first slot formed therein. A retaining member is attached to the gear member and is provided with a first protuberance shaped to pass through the first slot of the generally cylindrical member and moved into interfering relation with the generally cylindrical member in response to rotation of the gear member about the axis of rotation. As a result, the gear member is retained axially relative to the generally cylindrical member when the first protuberance is not aligned with the first slot, but the gear member is free to rotate and to move axially away from the generally cylindrical member when the first protuberance is aligned with the first slot. 
     The present invention further comprises a bearing carrier to which the generally cylindrical member can be attached. The generally cylindrical member, in a preferred embodiment of the present invention, is a bearing adapter and a roller bearing assembly is attached to the bearing adapter. A thrust bearing can be disposed between the gear member and the generally cylindrical member. The thrust bearing is generally concentric with the axis of rotation. A thrust ring and a seal ring are disposed between the gear member and the generally cylindrical member. The thrust ring and the seal ring are generally concentric with the axis of rotation. 
     In a particularly preferred embodiment of the present invention, the generally cylindrical member has first and second slots formed therein and the retaining member has first and second protuberances which are shaped to pass through the first and second slots, respectively, and move into interfering relation with the generally cylindrical member in response to rotation of the gear member about the axis of rotation. The first and second protuberances are disposed at diametrically opposite positions on the retaining member and the first and second slots are disposed at diametrically opposite positions on the generally cylindrical member. In a preferred embodiment, the gear member is a bevel gear. 
    
    
     
       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 an exploded view of a gear and bearing arrangement known to those skilled in the art; 
         FIG. 2  is a section view of an assembled version of the components shown in  FIG. 1 ; 
         FIG. 3  is an exploded view of the components made in accordance with the present invention; and 
         FIGS. 4 and 5  are two sectional views of the present invention. 
     
    
    
     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. 
     Before describing the concepts of the present invention, it is helpful to understand how the internal structure of a gearcase is constructed in known types of reverse rotation systems. 
       FIG. 1  is an isometric exploded view of an assembly of components that are inserted into the gearcase of a marine propulsion system in systems which are intended for reverse rotation. It should be understood that most marine propulsion systems, by convention, have propeller shafts that rotate in a clockwise direction when in forward gear and when viewed from a position behind the propeller. When two marine propulsion systems are used on a common marine vessel, one of the marine propulsion systems is designed to rotate in an opposite direction for the purpose of balancing propeller reacting moments so that the use of two marine propulsion systems does not adversely affect the operation of the marine vessel. It should be understood that the present invention is particularly useful during the assembly of the components for an opposite rotation system, but it is not restricted to this specific use. 
     With continued reference to  FIG. 1 , a forward gear  10  for an opposite rotation system is provided with a thrust bearing  12  and a thrust ring  14 , or thrust collar. An O-ring  16  is provided as a seal ring. A bearing adapter  20 , or generally cylindrical member, is attached to a bearing carrier  24 . The bearing adapter  20  is disposed in an opening  26  of the bearing carrier  24  with an interference fit relationship. A shim  28  is provided to axially position the bearing adapter  20  relative to the bearing carrier  24 . A roller bearing assembly  30  is pressed into the bearing adapter  20 . 
     With continued reference to  FIG. 1 , it should be understood that the components shown in  FIG. 1  are assembled into a gearcase in the direction represented in the illustration. In other words, the gearcase is turned to a position that will accept the bevel gear  10  in a downwardly moving direction prior to the other components shown in  FIG. 1 . After the bevel gear  10  is located in the gearcase, the thrust bearing  12 , thrust ring  14  and the O-ring  16  are placed in the gearcase above the bevel gear  10 . The bearing adapter  20 , with its roller bearing  30  inserted within it, is pressed into the bearing carrier  24  prior to assembly into the gearcase. As a subassembly, the bearing carrier  24 , the bearing adapter  20 , and the roller bearing  30  are then moved downwardly into the gearcase, in a direction generally parallel to axis  40 , and fitted to the existing position of the bevel gear  10 . This requires the generally cylindrical portion  42  of the bevel gear  10  to pass into the internal cylindrical opening  44  of the roller bearing assembly  30 . During this assembly procedure, the thrust bearing  12 , the thrust ring  14 , and the O-ring  16  can easily be moved out of their proper locations which are concentric with axis  40 . The assembly of these components shown in  FIG. 1  can result in an excessively difficult process which takes excessive time and which can frequently result in a misalignment of the individual components. 
       FIG. 2  is a section view of the components shown in  FIG. 1  after they are assembled together. At the bottom of the assembly is the bevel gear  10 . It should be understood that the bevel gear  10  is shown with its teeth  50  which, for simplicity, were not illustrated on the bevel gear  10  in  FIG. 1 . 
     Also shown in  FIG. 2  is the thrust bearing  12  and its associated thrust ring  14 . The O-ring  16  provides a seal between the bearing carrier  24  and the thrust ring  14 . The bearing adapter  20  is attached to the bearing carrier  24  with an interference fit and the lower bearing assembly  30 , with its roller bearings  60  located radially inward from the roller bearing structure  30 , disposed radially inwardly from the bearing adapter  20 . Although the roller bearings are not specifically shown in the Figures, reference numeral  60  shows where they are relative to the roller bearing assembly  30 . The bearings  60  are located radially inward from the main structure of the roller bearing assembly  30 . The roller bearings  60  are disposed in rolling contact with the outer cylindrical surface of the cylindrical portion  42  of the bevel gear  10 . 
     Also shown in  FIG. 2  are two seals  71  and  72  and a drain plug  74 . These components, in addition to the tapered roller bearing  78 , are contained within the bearing carrier  24 , but do not relate directly to the advantages provided by the present invention. 
     With reference to  FIGS. 1 and 2 , it should be understood that the bearing adaptor  20  has an upwardly positioned portion  80  that also extends radially inward from the generally cylindrical portion of the structure. This upper portion  80  is provided with two slots  84  that are used by a bearing removal tool in a manner that is generally known to those skilled in the art. 
     In order to understand the problem for which the present invention provides a solution, it is necessary to understand that the structure shown in  FIG. 2  would axially separate when the bearing carrier  24  is lifted upwardly relative to the bevel gear  10 . In other words, if the bearing carrier  24  was moved in a direction identified by arrows U, which is generally parallel to the central axis  40 , the bearing adapter  20  and roller bearing assembly  30  would move upwardly with the bearing carrier  24  because of the interference fits between these components. However, the roller bearing assembly  30  and its roller bearing  60  would also move upwardly relative to the cylindrical portion  42  of the bevel gear  10 . As a result, the thrust bearing  12 , the thrust collar  14 , and probably the O-ring  16 , would remain with the bevel gear  10  as the bearing carrier  24  is moved upwardly in the direction of arrows U. Reversing this procedure, it can be seen that an attempt to preassemble the components shown in  FIG. 2  prior to inserting the subassembly into the gearcase of a marine propulsion system would not be easily successful because of the tendency of the bevel gear  10 , thrust bearing  12 , thrust collar  14 , and O-ring  16  to fall downwardly away from the bearing carrier  24  as this assembly or insertion into the gearcase is attempted. The present invention is directed to solving this problem of assembly. 
       FIG. 3  is an isometric exploded view showing a structure made in accordance with the present invention. As described above, the bevel gear  10 , with its cylindrical portion  42 , thrust bearing  12 , thrust collar  14 , and O-ring  16  are generally similar to those associated components described above in conjunction with  FIGS. 1 and 2 . Similarly, the bearing carrier  24 , the shim  28 , and the bearing adapter  20  are generally similar those described above in conjunction with  FIGS. 1 and 2 . The present invention, however, provides a retaining member  100  that is insertable into the inner cylindrical cavity of the cylindrical portion  42  of the bevel gear  10 . In a preferred embodiment, the retaining member  100  is press fit into this cylindrical surface of the cylindrical portion  42 . The retaining member  100  is provided with first and second protuberances  110  (only one protuberance  110  is visible in  FIG. 3 ) which can be aligned with first and second slots  84  in the bearing adapter  20  (only one slot  84  is visible in  FIG. 3 ). This allows the components shown in  FIG. 3  to be assembled together as a subassembly, with the protuberances  110  passing through the slots  84  in a vertical direction to allow the components to be aligned and assembled prior to insertion into the gearcase. Then, by rotating the bearing carrier  24  slightly about the axis of rotation  40 , the protuberances  110  and slots  84  can be misaligned so as to prevent axial movement of the bevel gear  10  relative to the bearing adapter  20  and bearing carrier  24 . This locks the component shown in  FIG. 3  into a single subassembly which allows that subassembly to be easily lowered into a gearcase as an integral unit and assembled with the other components in the gearcase. 
       FIGS. 4 and 5  are section views of the present invention in two different stages of assembly. In  FIG. 4 , the first and second protuberances  110  are aligned with the first and second slots  84  in the upper portion  80  of the bearing adapter  20 . When positioned as shown in  FIG. 4 , the first and second protuberances  110  can move upwardly or downwardly through the first and second slots  84  to place the bevel gear  10  upwardly relative to the bearing carrier  24  in order to achieve the arrangement of components shown in  FIG. 4 . After this arrangement is achieved, the bearing carrier  24  can be rotated about the axis of rotation  40  relative to the bearing adapter  20  to place the first and second protuberances  110  into interfering relation with the upper portion  80  of the bearing adapter  20 . This retains the bevel gear  10 , the thrust bearing  12 , the thrust collar  14 , and the O-ring  16  in their positions axially relative to the bearing carrier  24 . In other words, when in the position shown in  FIG. 5 , the first and second protuberances  110  cannot pass downwardly because of the misalignment of those protuberances with the first and second slots  84  described above in conjunction with  FIG. 4 . As a result, the assembly shown in  FIG. 5  is attached together as a subassembly that can be more easily lowered into the gearcase for purposes of assembling the bevel gear  10 , which is a forward gear, with the bevel gear which is attached to the driveshaft as described above. The individual components of the subassembly shown in  FIG. 3  cannot move relative to each other axially in a direction parallel to the axis of rotation  40 . As a result, they cannot separate from each other and can therefore be assembled as a subassembly rather than as individual components in the manner generally known to those skilled in the art. 
     With reference to  FIGS. 3 ,  4 , and  5 , it can been seen that the mechanism for a marine propulsion system made in accordance with the preferred embodiment of the present invention, comprises a gear member  10  having an axis of rotation  40  and a generally cylindrical member  20 , or bearing adapter, having first and second slots  84  formed therein. A retaining member  100  is attached to the gear member  10  and is provided with first and second protuberances  110  which are shaped to pass through the first and second slots  84  and move into interfering relation with the bearing adapter  20 , or generally cylindrical member, in response to rotation of the gear member  10  about the axis of rotation  40 . As a result, the gear member  10  is retained axially relative to the generally cylindrical member  20  when the first and second protuberances  110  are not aligned with the first and second slots  84 , but the gear member  10  is free to move axially away from the generally cylindrical member  20  when the first and second protuberances  110  are aligned with the first and second slots  84 . A bearing carrier  24  is attached to the generally cylindrical member  20  and, as described above, the generally cylindrical member  20  is a bearing adapter in the preferred embodiment of the present invention. A roller bearing assembly  30 , with roller bearing  60 , is attached to the bearing adapter  20 . A thrust bearing  12  is disposed between the gear member  10  and the generally cylindrical member  20 , with the thrust bearing  12  being generally concentric with the axis of rotation  40 . A thrust ring  14  and a seal ring  16 , such as the O-ring, are disposed between the gear member  10  and the generally cylindrical member  20 , with the thrust ring and seal ring being generally concentric with the axis of rotation  40 . In a particularly preferred embodiment of the present invention, the first and second protuberances  100  are disposed at diametrically opposite positions on the retaining member  100 . Similarly, the first and second slots  84  are disposed at diametrically opposite positions on the generally cylindrical member  20 . 
     Although the present invention has been described in particular detail and illustrated to show a preferred embodiment, it should be understood that alternative embodiments are also within its scope.