Patent Publication Number: US-6656004-B2

Title: Tilt-trim subsystem for boats using a stern drive system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present invention is a continuation and claims the priority of allowed U.S. patent application Ser. No. 09/468,569 filed Dec. 21, 1999 now U.S. Pat. No. 6,296,535 entitled “Tilt-Trim Subsystem for Boats Using a Stem Drive System.” 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is generally related to a tilt-trim subsystem assembly for marine propulsion devices, and, more particularly, to a tilt-trim subsystem assembly for a stern drive propulsion system. 
     In marine propulsion devices, it is common to have hydraulic cylinder/piston assemblies located externally of the boat for effecting pivotal movement of the propulsion unit relative to its mounting bracket. For example, in marine propulsion devices of the stern drive or inboard/outboard type, it is common to have hydraulic cylinder/piston assemblies connected between the gimbal ring and the propulsion unit for effecting tilting movement of the propulsion unit relative to the gimbal ring. In other types of marine propulsion devices, such as outboard motors, it is known to have hydraulic cylinder/piston assemblies connected between the mounting bracket and the propulsion unit for effecting steering and/or tilting movement of the propulsion unit relative to the mounting bracket. 
     In many of these marine propulsion devices having hydraulic assemblies located externally of the boat, means are provided for supplying hydraulic fluid to the hydraulic assemblies from a source of fluid inside the boat. The source of fluid may be connected to an hydraulic circuit also inside the boat that pressurizes and distributes the hydraulic fluid through a manifold interconnecting respective hydraulic lines to the respective hydraulic cylinder assemblies outside the boat. The hydraulic circuit may typically include a pressure pump, and an electric motor coupled to drive the pump. This configuration generally presents several issues. One issue is whether to run the hydraulic lines over the transom or through the transom and, if through the transom, how to seal the opening through which the hydraulic lines pass. Another issue is how to protect the portions of the hydraulic lines extending externally of the transom. For example, the hydraulic lines may be exposed to a relatively harsh external environment, e.g., ocean water, sun rays, and other factors that may promote galvanic corrosion, or other deterioration to the line material. Any deterioration of the lines may be further aggravated due to the bending that the lines may be subject to as the propulsion unit is tilted upwardly and downwardly. This may lead to leaks and a relatively short hydraulic line life. Further, such tilt/drive subsystems may take valuable room in the interior of the boat and require additional holding fixtures and additional labor to install on the boat floor or transom. U.S. Pat. No. 5,032,094 appears to describe a tilt-trim subsystem that uses an intricate external assembly including separate tilt and trim cylinders to provide tilt and trim to an outboard propulsion unit and that may somewhat alleviate some of the above-discussed issues that may develop in outboard units, unfortunately such subsystem does not overcome any of such issues as may be encountered in boats using a stern drive propulsion system since the configuration described in the foregoing patent is strictly limited to outboard designs. Thus, it is desirable to provide a tilt-trim subsystem assembly that, with a lesser number of components, and consequently even more inexpensively and reliably than known assemblies, allows for providing tilt and trim to a stern drive propulsion system that is not subject to the foregoing problems and that can be easily installed either as a replacement kit or as part of an original installation. The increased reliability of the tilt-trim subsystem of the present invention and its ease of service are likely to result in enhanced durability at a lower cost to pleasure boat users and others. 
     BRIEF SUMMARY OF THE INVENTION 
     Generally speaking, the present invention fulfills the foregoing needs by providing a stern drive system having an outdrive configured to be rotated about a generally horizontal axis to impart a desired trim or tilt to the drive system. A gimbal unit has means for pivotally receiving a first anchor pin. A tilt-trim subsystem assembly is affixed to the outdrive. The tilt-trim assembly has one respective end thereof configured to pivotally receive a second anchor pin supported by the outdrive. The assembly includes at least one cylinder having one end thereof connected to the first anchor pin so that when the cylinder is actuated the outdrive and the tilt-trim subsystem assembly are rotated about the generally horizontal axis during tilt-trim maneuvers. 
     The present invention further fulfills the foregoing needs by providing a tilt-trim subsystem assembly affixed to an outdrive of a stern drive that may be supported by a gimbal unit and may be configured to rotate about a predetermined axis to impart a desired trim or tilt to the drive system. The tilt-trim assembly has one respective end thereof configured to pivotally receive one anchor pin supported by the outdrive. The assembly includes one or more cylinders having one end thereof pivotally connected to another anchor pin so that when the cylinder is actuated the outdrive and the tilt-trim subsystem assembly are jointly rotated about the predetermined axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which: 
     FIG. 1 is a side elevational view of a prior art stern drive system for a boat; 
     FIG. 2 is a side elevational view of an exemplary embodiment of the present invention showing a tilt-trim subsystem assembly in combination with a stern drive system; 
     FIG. 3 is an isometric view of the embodiment shown in FIG. 2; 
     FIG. 4 is an isometric view of the tilt-trim subsystem assembly of the present invention; 
     FIG. 5 is a partial cross-section view of an exemplary gimbal unit and gimbal housing configured to have a recess to accommodate leads that may be used for carrying control and power signals to an electric motor in the tilt-trim assembly; and 
     FIG. 6 is cross-section view along line VI—VI in FIG. 5 illustrating further details regarding the recess shown in FIG.  5 . 
    
    
     Before any embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the exemplary details of construction and arrangements of components set forth in the following description or illustrated in the drawings. For example, although the cylinder actuating means will be described in the context of hydraulic cylinders, it will be appreciated that in lieu of using hydraulic actuators, electromechanical actuators could be employed to impart the thrust required to tilt or trim the stern drive propulsion system. Thus, the invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of illustrative description and should not be regarded as limiting. 
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates an exemplary prior art marine propulsion device  10  mounted on a boat  12  having a transom  14 . The marine propulsion device  10  is of the stern drive or inboard/outboard type. As best shown in FIG. 1, the marine propulsion device  10  comprises an engine  16  securely mounted on the boat frame by suitable means such as rubber mounts (not shown). The marine propulsion device  10  also comprises a mounting bracket or gimbal housing  18  mounted on the outer surface of the boat transom  14  and fixedly attached to the boat transom  14 . The gimbal housing  10  can be attached to the boat transom  14  by any suitable means, such as by bolts extending through the transom  14 . 
     The marine propulsion device  10  also comprises a gimbal unit or gimbal ring  30 , connected to the gimbal housing  18  for pivotal movement relative to the gimbal housing  18  about a generally vertical steering axis  32 , and a pivot housing  34  connected to the gimbal ring  30  for pivotal movement relative to the gimbal unit  30  about a generally horizontal tilt-trim axis  36 . Such a construction is well known in the art and will not be described in detail other than as necessary for an understanding of the invention. 
     The marine propulsion device  10  also comprises an outdrive  37  that may be removably connected to the pivot housing  34  for common pivotal movement of the outdrive  37  with the pivot housing  34 . In the illustrated construction, the outdrive  37  is removably connected to the pivot housing  34  by a plurality of bolts  38 . The outdrive  37  includes a propeller  39  mounted on a propeller shaft  40 , and a generally horizontal drive shaft  42  having one end removably connected to the engine  16  and an opposite end having thereon a bevel gear  44 . A universal joint  46  attached to the horizontal drive shaft  42  allows pivotal movement of the drive shaft  42  with the propulsion unit  37 . The bevel gear  44  drives a bevel gear  48  on the upper end of a vertical drive shaft  50 . The lower end of the vertical drive shaft  50  has thereon a driving gear  52 . A reversible transmission selectively clutches a pair of driven gears  54  to the propeller shaft  40  to transmit forward or reverse motion to the propeller shaft  40  from the driving gear  52 . 
     The marine propulsion device  10  also comprises a pair of hydraulic cylinder/piston assemblies  60  pivotally connected between the gimbal housing  18  and the outdrive  37  for effecting pivotal movement (tilt and trim movement) of the outdrive  37  relative to the gimbal housing  18  and relative to the gimbal unit  30  about the tilt axis  36 . The hydraulic cylinder/piston assemblies  60  are connected between the lower end of the gimbal unit  30  and the outdrive  37 . The cylinder/piston assemblies  60  extend on opposite sides of the propulsion unit  37 . Each of the cylinder/piston assemblies  60  includes a cylinder  62  having an upper portion, a forward end pivotally connected to the gimbal ring  30 , and a rearward end. The cylinder/piston assemblies  60  each also include a piston  64  slidably received in the cylinder  62  for reciprocal movement therein, the piston  64  dividing the cylinder  62  into forward and rearward pressure chambers. The cylinder/piston assemblies  60  also include a piston rod  66  having a forward or inner end fixedly attached to the piston  64  and extending outwardly of the rearward end of the cylinder  62 , and a rearward or outer end pivotally attached to the propulsion unit  37 . Increasing the pressure in the forward pressure chamber of the cylinder  62  causes the piston rod  66  to extend, thereby causing the propulsion unit  37  to tilt upwardly, and increasing the pressure in the rearward pressure chamber of the cylinder  62  causes the piston rod  66  to retract, thereby causing the propulsion unit  37  to tilt downwardly. 
     The marine propulsion device  10  further comprises a conduit having one end communicating with a tank  70  inside the boat  12 . Tank  70  supplies and stores working hydraulic fluid that may be pressurized by a hydraulic circuit  71  having a motor pump also inside the boat. The conduit has an opposite end communicating with the hydraulic cylinder/piston assemblies  60 . The conduit may extend through an opening in the gimbal housing and may be exposed to the environment external to the boat at least between the gimbal housing  18  and the cylinders  60 . The conduit further includes a manifold  72 , a first fluid line means that allows communication between the manifold  72  and the hydraulic cylinder/piston assemblies  60  for supplying hydraulic fluid to the cylinder/piston assemblies  60 , and a second fluid line means extending through the opening in the gimbal housing  18  and having one end communicating with the source of fluid  70 , and an opposite end communicating with the manifold  72 . The first fluid line means includes a first pair of hydraulic lines communicating between the manifold  72  and the first or right cylinder  62 . One of the hydraulic lines of the right pair may be connected to the forward end, e.g., the forward pressure chamber, of the right cylinder  62 , and the other hydraulic line of the pair may be connected to the rearward end, e.g., the rearward pressure chamber of the right cylinder  62 . The first fluid line means also includes a second pair of hydraulic lines  78  and  80  communicating between the manifold  72  and the second or left cylinder  62 . One of the hydraulic lines of the left pair is connected to the forward end, e.g., the forward pressure chamber, of the left cylinder  62 , and the other hydraulic line  80  of the left pair being connected to the rearward end, e.g., the rearward pressure chamber, of the left cylinder  62 . As will be appreciated by those skilled in the art, although stern drive propulsions systems such as the above-described exemplary prior art system have proven to provide effective propulsion means to boat users, as suggested above and further described below, the present invention allows to even further enhance the reliability and ease of maintenance of such type of marine propulsion systems. 
     FIGS. 2 and 3 illustrate one exemplary embodiment of the present invention showing a tilt-trim subsystem assembly  100  in combination with a stern drive propulsion system. As shown in FIGS. 2 and 3, the tilt/trim subsystem assembly  100  may be affixed to the outdrive  37  using any suitable affixing means, such as pivot pins co-axially disposed relative to tilt-trim axis  36 , etc. As further shown in FIGS. 2 and 3, the gimbal unit  30  has means for receiving a first anchor pin  102 . As best appreciated in FIG. 4, the tilt/trim subsystem has one end configured to receive a second anchor pin  104  (FIGS. 2 and 3) supported by the outdrive  37 . The assembly  100  includes one or more cylinders  106 . In the event two cylinders are employed, then one of the cylinders  106  may straddle on one side of outdrive  37 , as seen in FIG.  2 . The other of the cylinders  106  may straddle on the other side of the outdrive  37 , as seen FIG.  4 . Each of the cylinders includes a respective slidable piston  107  that may be pivotally connected at one end thereof to the first anchor pin. It will be appreciated that the piston end need not be connected to the first anchor pin since the cylinder/piston could be arranged opposite to the illustrated arrangement so that the piston would be connected to the second anchor pin in lieu of the first anchor pin. As better appreciated in FIG. 4, cylinders  106  and the tilt-trim assembly comprise a unitized body, i.e., they comprise one integral unit that may be constructed using well-known and readily understood casting techniques to those of ordinary skill in the art, e.g., die casting, etc. An exemplary material for the assembly may be aluminum or any other relatively light weight and high strength, and substantially corrosion-resistant material. 
     As further shown in FIGS. 2 and 3, assembly  100  contains a fluid circuit, e.g., a hydraulic or pneumatic circuit that is completely self-contained within the assembly for actuating the cylinders  106  and thus avoiding the various issues generally associated with known tilt/trim subsystems for stern drives. In a preferred embodiment, the hydraulic circuit may be chosen due to its good shock absorbing characteristics. As will be appreciated by those skilled in the art, the hydraulic circuit may be configured using design techniques readily understood by those of ordinary skill in the art. For readers interested in background information regarding one exemplary hydraulic design, reference is made to U.S. Pat. No. 4,786,263 commonly assigned to the same assignee of the present invention and herein incorporated by reference. By way of example, the hydraulic circuit may include a pump  108  and a fluid storage tank  110  connected to pass hydraulic fluid to the pump. The pump  108  may be driven by a motor  112 , e.g., a reversible DC motor, in response to externally-derived signals supplied to the motor by way of suitable leads  150  (FIGS.  5  and  6 ). Both the motor and the pump and any associated hydraulic valves, e.g., relief valves, thermal relief valves, manual release valves, etc., may be disposed in respective compartments within the assembly sufficiently sealed to prevent entry of moisture therewithin. 
     By way of example and not of limitation, the tilt/trim assembly may include internal passages  114  and  116  (as represented by the dashed lines in FIG. 4) to provide fluid communication between the pump, the cylinders and the tank. For example, one of the passages may provide a path for supplying pressurized fluid to a pressure chamber of a respective cylinder, and the other passage may provide a return path for fluid returning to the pump and/or storage tank. The passages may be bored using standard drilling techniques or may be configured while the assembly is cast using a mold configured to define such internal passages. Alternatively, in lieu of providing internal passages, external tubing could be used to provide the supply and return paths to the fluid flowing into or out of the respective cylinders. It will be appreciated that since the assembly  100  rotates together with the outdrive, then in this embodiment the tubing would not be subject to any bending while the outdrive is being tilted. Similarly, since the length of the tubing is substantially short since the hydraulic circuit and the cylinders are contained substantially proximate to one another, then one could use an inexpensive shield to protect the tubing from the external environment. It will be further appreciated by those skilled in the art, that having shorter hydraulic conduits, either externally or internally located, will result in improved shock transient response from the hydraulic circuit in the event the propulsion unit were to strike an underwater obstruction or object. 
     FIGS. 5 and 6 illustrate an exemplary construction that may be provided in the gimbal ring  30  to accommodate one or more leads  150  that may carry the externally-derived signals to the motor  112  in the tilt/trim assembly. As shown in FIGS. 5 and 6, a recess  152 , such as a groove or notch, may be configured within the gimbal ring to accommodate leads  150 . To secure the leads suitable affixing means, such as clamps  154  may be used to affix the leads  150  within the gimbal ring. The leads need not uninterruptable since one or more connectors could be used at suitable connecting points to facilitate installation and/or servicing of the tilt/trim assembly. By way of example, a connector or plug  156  could be installed onto the trim/tilt assembly, e.g. near the motor compartment, so as to provide a suitable interconnecting point between any leads disposed within that motor compartment and leads  150 . It will be appreciated that any commercially available water-tight connector designed for a marine environment operation will provide a suitable seal so as to prevent entry of moisture into the tilt-trim assembly. 
     Thus, it should now be appreciated that with the present invention, as described above, since the cylinder or cylinders in the tilt/trim assembly comprise a unitized structure and are angularly movable in unison relatively to the gimbal housing, and further since the working hydraulic fluid conduits interconnecting the motor pump, and the tilt/trim cylinder or cylinders therein may now be defined, if so desired, without employing exteriorly installed tubing, then the present invention allows for either avoiding altogether, in the case of internal passageways, or substantially avoiding, in the case of short external tubing, the problem of fluid conduit corrosion, etc. Further, the tilt-trim subsystem may be constructed as a single assembly with the hydraulic pressure circuit incorporated in the assembly. Thus, the tilt-trim subsystem can easily be attached to and detached as a kit from the outdrive and the gimbal housing. As suggested above, the assembly of the present invention because of its integrated construction and improved transient response characteristics may provide increased protection against shocks that may be produced when the propulsion unit is hit by objects, such as driftwood, etc. 
     While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. For example, although some aspects of the present invention have been described in the context of an hydraulic circuit, it will be appreciated that in lieu of using hydraulic cylinders, torque-applying screws rotated by a respective electromechanical actuator could be employed to impart the torque required to tilt or trim the stern drive propulsion system. Thus, numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.