Patent Abstract:
A self-contained hydraulic thruster for vessel. The hydraulic thruster incorporates an elevated helm platform mounted to a base having reinforced base feet, and a hydraulic fluid reservoir mounted on the helm platform. The elevation of the hydraulic fluid reservoir facilitates flow of hydraulic fluid to a hydraulic power pack mounted on the base. A lower unit mounting tube is attached to the base, and at least one lower unit is mounted at an end of the lower unit mounting tube, laterally offset from the helm platform, so that when the lower unit is retracted and tilted up, it lies on one side of the platform, and the platform doesn&#39;t interfere with retraction and tilting of the lower unit. Lower units are pivotably mounted in lower unit housings with lower unit bushings, and steering is provided by a steering motor through an overhung load adaptor to a drive gear.

Full Description:
CLAIM FOR PRIORITY 
   This utility patent application is based upon and claims the benefit of the earlier filing date of U.S. provisional patent application Ser. No. 60/903,400 filed Feb. 26, 2007 entitled Self-Contained Hydraulic Thruster for Vessel. 

   BACKGROUND OF THE INVENTION 
   Field of the Invention 
   This invention relates to vessel propulsion systems, and in particular to a self-contained hydraulic thruster for vessel. 
   Background of the Invention 
   Marine thrusters typically mount on barges and flat boats, and are used as propulsion for these vessels. One type of marine thruster employs a prime mover such as a diesel engine driving a hydraulic pump, together known as a “power pack”, and the resultant pressurized hydraulic fluid may be employed to drive a propeller attached to a lower unit. 
   There are a number of problems associated with currently available marine thrusters. Where a centrally located tiltable lower unit has been retracted and tilted backwards for storage, maintenance, cleaning, etc., the protruding upper end of the lower unit interferes with the helm and helm platform, and prevents full upward tilting of the retracted lower unit. Therefore, it would be desirable to provide a marine thruster which may be retracted and then fully tilted. 
   Another problem with existing designs: the hydraulic fluid reservoir is disposed on the base of the marine thruster, where it is incapable of supplying enough fluid head to self-prime the power pack, and to facilitate hydraulic fluid flow to the hydraulic power pack. Thus, it would be desirable to provide a hydraulic fluid reservoir which is elevated above the level of the power pack. 
   Still another problem is where a marine thruster&#39;s single lower unit propeller does not supply enough power to adequately propel a vessel upon which it is mounted. It would therefore be desirable to provide a marine thruster with more than one lower unit, for increased power. 
   Other problems with existing designs include insufficient reinforcement at the lower unit tilt actuator attach point on the base, inadequate bearing surface at the lower unit pivot point, and excess steering motor stress. 
   Existing Designs 
     FIGS. 1 and 2  are illustrative of the tilt interference problem, and are rear views of a prior art marine thrusters  2 . The location of their lower units  4  directly behind their respective helms causes interference between lower unit  4  and the helm when attempting to fully tilt lower unit  38  up when lower unit  38  is fully retractable. This interference prevents lower unit  38  from fully tilting up when it is fully retracted, thus hindering stowing of lower unit  38  for storage, transportation, servicing, or cleaning. 
   In addition, the mounting of the hydraulic fluid reservoir on the base of this design provides inadequate flow from the hydraulic fluid tank for self-priming and gravitational flow from hydraulic fluid tank to power pack. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a self-contained hydraulic thruster for vessel with an elevated hydraulic fluid reservoir. Design features allowing this object to be accomplished include a hydraulic fluid reservoir mounted on a helm platform which is elevated a substantial height above a base to which a hydraulic power pack is mounted. Benefits associated with the accomplishment of this object include power pack self-priming, and facilitated hydraulic fluid flow from the hydraulic fluid reservoir to the hydraulic power pack. 
   It is another object of the present invention to provide a self-contained hydraulic thruster for vessel whose lower unit(s) may be retracted and tilted up without interference from the helm platform. Design features allowing this object to be accomplished include at least one lower unit mounted at an end of a lower unit mounting tube, the lower unit being laterally offset from a steering platform. Advantages associated with the accomplishment of this object include more efficient lower unit stowing for storage and/or transportation, greater tilt achievable (close to 90 degrees), the ability to tilt the propellers and lower unit completely out of the water for servicing and cleaning, decreased corrosion due to the ability of getting the lower units and propellers completely out of the water when not in use to reduce corrosion, and greater retraction of the lower unit. 
   It is still another object of this invention to provide a self-contained hydraulic thruster for vessel whose lower units pivot smoothly and easily within respective lower unit bores in lower unit housings. Design features enabling the accomplishment of this object include at least one bushing inside a lower unit bore, and a lower unit bushing bore sized to slidably admit a lower unit. Advantages associated with the realization of this object include easier and smoother steering, and less force required to accomplish same. 
   It is another object of the present invention to provide a self-contained hydraulic thruster for vessel which is stable and well-supported on a vessel to which it is mounted. Design features allowing this object to be accomplished include a base having at least one base foot attached to a rear side of the base, with a base foot reinforcement plate and base foot center spar in the base foot. Benefits associated with the accomplishment of this object include better support for the self-contained hydraulic thruster for vessel, and greater operator security. 
   It is still another object of this invention to provide a self-contained hydraulic thruster for vessel whose steering is reliable and long-lived. Design features enabling the accomplishment of this object include a steering motor driving a drive gear through an overhung load adaptor. Advantages associated with the realization of this object include smoother steering function, longer-lived steering motor, and the associated reduced motor maintenance and replacement costs. 
   It is yet another object of this invention to provide a self-contained hydraulic thruster for vessel which is economical to build. Design features allowing this object to be achieved include the use of components made of readily available materials, and commercially available components such as an existing steering motor, overhung load adapter, hydraulic actuator, hydraulic power pack, hydraulic fluid reservoir, lower unit, propeller, steering gear, drive gear, and hydraulic lines. Benefits associated with reaching this objective include reduced cost, and hence increased availability. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with the other objects, features, aspects and advantages thereof will be more clearly understood from the following in conjunction with the accompanying drawings. 
     Ten sheets of drawings are provided. Sheet one contains  FIGS. 1 and 2 . Sheet two contains  FIG. 3 . Sheet three contains  FIG. 4 . Sheet four contains  FIG. 5 . Sheet five contains  FIGS. 6 and 7 . Sheet six contains  FIGS. 8 ,  9  and  10 . Sheet seven contains  FIG. 11 . Sheet eight contains  FIG. 12 . Sheet nine contains  FIG. 13 . Sheet ten contains  FIG. 14 . 
       FIGS. 1 and 2  are rear views of a prior art marine thruster. 
       FIG. 3  is a rear quarter isometric view of a self-contained hydraulic thruster for vessel. 
       FIG. 4  is a side view of a self-contained hydraulic thruster for vessel with its lower units tilted up. 
       FIG. 5  is a rear quarter isometric view of a self-contained hydraulic thruster for vessel, with its left lower unit housing, left lower unit, steering assembly, and steering gear removed. 
       FIG. 6  is an exploded view of a lower unit, lower unit bushings, and lower unit housing. 
       FIG. 7  is a front isometric view of a lower unit bushing. 
       FIG. 8  is a front quarter isometric view of a base foot. 
       FIG. 9  is a side cross-sectional view of a base foot taken at section IX-IX of  FIG. 8 , showing the lower unit tilted down. 
       FIG. 10  is a side cross-sectional view of a base foot taken at section IX-IX of  FIG. 8 , showing the lower unit tilted up. 
       FIG. 11  is a front isometric view of a steering assembly. 
       FIGS. 12-14  depict rear quarter isometric views of an alternate embodiment self-contained hydraulic thruster for vessel having a single lower unit  38  offset from the helm platform to permit full retraction and tilting up of the lower unit. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 3  is a rear quarter isometric view of self-contained hydraulic thruster  20 . Hydraulic thruster  20  comprises base  30  which supports hydraulic power pack  22  and helm platform  26 . Helm platform  26  in turn supports helm  24  and hydraulic fluid reservoir  28 . Helm platform  26  is elevated above base  30  to elevate hydraulic fluid reservoir  28  above the level of hydraulic power pack  22 , and for enhanced visibility for the vessel operator. 
   It is desirable to locate hydraulic fluid reservoir  28  above the level of hydraulic power pack  22  to render the hydraulic system self-priming, and to facilitate the flow of hydraulic fluid from hydraulic fluid reservoir  28  to the hydraulic fluid pump in hydraulic power pack  22 . Hydraulic power pack  22  is a conventional, commercially available prime mover, such as a diesel engine, coupled to a hydraulic fluid pump, which supplies hydraulic fluid under pressure to power hydraulic thruster  20 . 
   Base  30  may comprise one or more base feet  32  at its rear, each attached to a base side spar  33 , to increase the stability of base  30  on the vessel  10  upon which hydraulic thruster  20  is mounted. One or more vessel stops  44  are mounted to base rear spar  34 , and serve to help immobilize hydraulic thruster  20  atop a vessel  10  to which it is mounted, and also transmit force from propellers  39  to vessel  10 . 
   One or more lower unit mounting tube supports  40  extend aft from base rear spar  34  and support lower unit mounting tube  36 . One or more lower units  38  are mounted to lower unit mounting tube  36  by means of respective lower unit housings  42 . In the preferred embodiment, two lower units  38  were mounted to opposite ends of lower unit mounting tube  36  by means of respective lower unit housings  42 , laterally offset from helm platform  26  in order to permit full retraction and tilting up of lower units  38  to stow same for storage, transportation, servicing, cleaning, etc. 
   Each lower unit  38  is free to rotate within its respective lower unit housing  42  as indicated by arrow  18  in  FIG. 3 . Steering assembly  50  mounted to at least one lower unit housing  42  drives steering gear  52  attached to a lower unit  38 . Steering assembly  50  causes steering gear  52  to rotate, which in turn causes an associated lower unit  38  to rotate as indicated by arrow  18  in  FIG. 3 , thus providing a steering function to hydraulic thruster  20 . Tie rod  54  connects lower units  38  together, so that as steering assembly  50  causes one lower unit  38  to rotate, tie rod  54  causes the other lower unit(s)  38  entrained by tie rod  54  to rotate the same way. 
   Hydraulic fluid under pressure from hydraulic power pack  22  powers propeller(s)  39  on lower unit(s)  38 , and may also serve as a power source for steering assembly  50 . 
   In the preferred embodiment, each lower unit housing  42  was free to rotate on lower unit mounting tube  36  as indicated by arrow  16  in  FIG. 3 . This rotational attachment of lower unit housing  42  on lower unit mounting tube  36  permits lower unit(s)  38  to tilt upwards close to 90 degrees from the down position depicted in  FIGS. 3 and 5 .  FIG. 4  is a side view of a self-contained hydraulic thruster  20  with its lower units  38  tilted up. 
     FIG. 5  is a rear quarter isometric view of a self-contained hydraulic thruster  20  for vessel, with its left lower unit housing  42 , left lower unit  38 , steering assembly  50  and steering gear  52  removed. Lower unit housing  42  comprises mounting tube bore  14  sized to slidably admit lower unit mounting tube  36 , and lower unit bore  12  sized to slidably admit lower unit  38 . 
   Due to the slidable attachment between mounting tube bore  14  and lower unit mounting tube  36 , lower unit  38  is free to rotate on lower unit mounting tube  36  in order to tilt up and down, as indicated by arrow  16  in  FIG. 3 . Similarly, due to the slidable attachment between lower unit bore  12  and lower unit  38 , lower unit  38  is free to pivot within lower unit bore  12  in order to provide a steering function, as indicated by arrow  18  in  FIG. 3 . 
   Lower unit housing  42  can be re-mounted on lower unit mounting tube  36  simply by sliding lower unit mounting tube  36  into mounting tube bore  14  as indicated by arrow  70  in  FIG. 5 . Lower unit  38  can be re-inserted into lower unit housing  42  by sliding it into lower unit bore  12  as indicated by arrow  74 . Steering gear  52  can then be attached to lower unit  38 , and steering assembly  50  mounted on lower unit housing  42 , as indicated by arrow  72 . 
     FIG. 6  is an exploded view of lower unit housing  42 , lower unit bushings  46 , and lower unit  38  with propeller  39  attached. In the preferred embodiment, lower unit housing  42  comprised lower unit housing roof  62  with lower unit housing roof bore  65 , lower unit housing walls  63 , each with a lower unit housing wall bore  66 , and lower unit housing floor  64  with lower unit housing floor bore  67 . Lower unit housing wall bores  66  are sized to slidably admit lower unit mounting tube  36 . Lower unit housing roof bore  65  and lower unit housing floor bore  67  are sized to slidably admit lower unit  38 . 
   An alternate embodiment hydraulic thruster  20  comprises lower unit bushings  46 . As may be observed in  FIG. 7 , a front isometric view of lower unit bushing  46 , lower unit bushing  46  comprises lower unit bushing lesser outside diameter  48 , lower unit bushing greater outside diameter  49 , and lower unit bushing bore  47 . Lower unit bushing lesser outside diameter  48  is sized to slidably fit into lower unit housing roof bore  65  or lower unit housing floor bore  67 . Lower unit bushing greater outside diameter  49  exceeds the diameter of lower unit housing roof bore  65  and the diameter of lower unit housing floor bore  67 . Lower unit bushing bore  47  is sized to slidably admit lower unit  38 . 
   As may be observed in  FIG. 6 , a lower unit bushing  46  is inserted into lower unit housing roof bore  65  as indicated by arrow  68 , and a lower unit bushing  46  is inserted into lower unit housing floor bore  67  as indicated by arrow  69 . Then lower unit  38  is inserted through the lower unit bushing bores  47  as indicated by arrow  76 . In this embodiment, lower unit  38  turns within lower unit bushing bores  47 , thus avoiding direct contact between lower unit  38  and lower unit housing roof bore  65  and lower unit housing floor bore  67 . 
   Lower unit bushings  46  serve to cushion and reduce friction associated with the slidable attachment between lower unit housing  42  and lower unit  38 . In the preferred embodiment, lower unit bushings  46  were made of nylon, synthetic, plastic, teflon, stainless steel or other metal or coated material, or other appropriate low-friction, corrosion-resistant material. 
     FIG. 8  is a front quarter isometric view of base foot  32 . As may be observed in  FIGS. 3 and 5 , a base foot  32  may be disposed on either side of the aft end of base  30 . In the preferred embodiment, base  30  incorporated base side spars  33 , at whose aft end base feet  32  were attached, although it is intended to fall within this disclosure that base foot  32  may be attached to base  30  at any appropriate location or component of base  30 . 
   Base foot  32  comprises base foot rear spar  80 , and base foot side spar  82  attached at one end to base foot rear spar  80 , and at the other to base side spar  33 . In the preferred embodiment, base foot rear spar  80  was an end of base rear spar  34 . Base foot  32  further comprises base foot reinforcement plate  86  attached to base foot rear spar  80  at vessel stop  44 , and base foot center spar  84  attached at one end to base foot reinforcement plate  86 , and at an opposite end to base foot side spar  82 . Base foot reinforcement plate  86  and base foot center spar  84  serve to reinforce the structurally critical attach point of vessel stop  44  to base foot  32 . In the preferred embodiment, base  30 , base foot rear spar  80 , base foot reinforcement plate  86 , base foot side spar  82 , and base foot center spar  84  were of welded metal construction. 
     FIG. 9  is a side cross-sectional view of a base foot  32  taken at section IX-IX of  FIG. 8 , showing lower unit  38  tilted down.  FIG. 10  is a side cross-sectional view of base foot  32  taken at section IX-IX of  FIG. 8 , showing lower unit  38  tilted up. Lower unit  38  is tilted up and down by actuator  88 . Actuator  88  is attached at one end to lower unit housing  42 , and at its other end to vessel stop  44 . In the preferred embodiment, actuator  88  was a hydraulic actuator powered by pressurized hydraulic fluid from hydraulic power pack  22 , and controlled from helm  24 . Lower unit  38 , steering assembly  50 , and actuator  88  may be connected to hydraulic power pack  22  by any appropriate means, including hydraulic lines, which are not shown in the figures in interest of clarity. 
   When actuator  88  is extended or retracted as indicated by arrow  92  in  FIG. 10 , such movement by actuator  88  causes lower unit  38  to tilt up or down as indicated by arrow  92  in  FIG. 10 . The installation of lower unit(s)  38  laterally offset from elevated helm platform  26  permits lower unit(s)  38  to be tilted up close to 90 degrees from full down, even when lower unit(s)  38  are fully retracted, as depicted in  FIG. 14 . 
     FIG. 11  is a front isometric view of steering assembly  50 . Steering assembly  50  comprises drive gear  60  sized to mesh with steering gear  52 , and steering motor  56 . Drive gear  60  is attached to steering motor  56  through overhung load adaptor  58 . Overhung load adaptor  58  is attached to steering motor  56 , and serves to transfer rotational motion from the output shaft of steering motor  56  to drive gear  60 , while minimizing stress put on the internal bearings of steering motor  56 , thus prolonging the life of steering motor  56 . In the preferred embodiment, overhung load adaptor  58  was a commercially available overhung load adaptor. 
     FIGS. 12-14  depict rear quarter isometric views of an alternate embodiment self-contained hydraulic thruster  20  for vessel comprising a single lower unit  38  mounted to a single base foot  32 . In this embodiment, a single lower unit  38  is mounted at an end of lower unit mounting tube  36  offset from helm platform  26 . The offset mounting of lower unit  38  incorporated into this embodiment is important to stow lower unit  38 , for transportation, storage, servicing, and cleaning of hydraulic thruster  20 . 
   Due to the slidable attachment of lower unit  38  and lower unit housing  42 , lower unit  38  is not only free to pivot, but can also be retracted as indicated by arrow  78  in  FIG. 13 . Lower unit  38  can be retracted not only for transportation and storage of hydraulic thruster  20 , but also to allow hydraulic thruster  20  to be used in shallow water. 
   Lower unit(s)  38  may be then stowed for transportation, servicing, cleaning and/or storage by tilting up lower unit  38  as indicated by arrow  94  in  FIG. 14 . It can be readily appreciated that if lower unit  38  were to be centrally mounted on lower unit mounting tube  38 , as is depicted in the prior art marine thrusters of  FIGS. 1 and 2 , the elevated nature of helm platform  26  would interfere with the tilting up of lower unit  38  for storage and transportation: it would not be possible to fully tilt up lower unit  38  due to interference between the upper part of lower unit  38  and helm platform  26 . Thus, the mounting of lower unit  38  at an end of lower unit mounting tube  36  laterally offset from elevated helm platform  26  permits more efficient storage and transportation of hydraulic thruster  20 , by permitting lower unit  38  to be fully tilted when it is fully retracted, as depicted in  FIG. 14 . 
   When mounted on a vessel  10 , the alternate embodiment hydraulic thruster  20  depicted in  FIGS. 12-14  is positioned such that lower unit  38  is at the centerline of vessel  10 , so as to provide laterally symmetrical thrust, and to avoid a turning tendency due to non-centrally located propulsion. It may be noted that the mounting of lower units  38  at either end of lower unit mounting tube  36  in the embodiment depicted in  FIGS. 3 and 5 , laterally offset from elevated helm platform  26 , also permits these lower units to be completely tilted when retracted, for optimal storage and/or transportation. 
   In the interest of saving material and cost, a single base foot  32  may be incorporated into the single lower unit hydraulic thruster  20  embodiment depicted in  FIGS. 12-14 , on the same side as the single lower unit  38 . In addition, lower unit mounting tube  36  could extend laterally only to the width of the base side spar  33  on the side of base  30  opposite the single lower unit  38 , and the vessel stop  44  on that side could then be attached to base rear spar  34 , not base foot  32 . This single base foot  32  embodiment is depicted in  FIG. 12 . 
   In the preferred embodiment, base  30 , helm platform  26 , helm  24 , hydraulic fluid reservoir  28 , base feet  32 , lower unit mounting tube supports  40  and lower unit housing(s)  42  were made using metal, synthetic, corrosion resistant metal, corrosion resistant metal fasteners, welded construction, or other appropriate materials and processes. 
   Base  30  structural members such as base side spars  33 , base rear spar  34 , base foot  32 , and lower unit mounting tube support(s)  40  may be plates, C beams, I beams, or any other appropriate structural member shape. Steering motor  56 , overhung load adaptor  58 , drive gear  60 , steering gear  52 , and hydraulic power pack  22  were commercially available items. 
   While a preferred embodiment of the invention has been illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit of the appending claims. 
   DRAWING ITEM INDEX 
   
       
         2  prior art marine thruster 
         4  prior art marine thruster lower unit 
         10  vessel 
         12  lower unit bore 
         14  mounting tube bore 
         16  arrow 
         18  arrow 
         20  hydraulic thruster 
         22  hydraulic power pack 
         24  helm 
         26  helm platform 
         28  hydraulic fluid reservoir 
         30  base 
         32  base foot 
         33  base side spar 
         34  base rear spar 
         36  lower unit mounting tube 
         38  lower unit 
         39  propeller 
         40  lower unit mounting tube support 
         42  lower unit housing 
         44  vessel stop 
         46  lower unit bushing 
         47  lower unit bushing bore 
         48  lower unit bushing lesser outside diameter 
         49  lower unit bushing greater outside diameter 
         50  steering assembly 
         52  steering gear 
         54  tie rod 
         56  steering motor 
         58  overhung load adaptor 
         60  drive gear 
         62  lower unit housing roof 
         63  lower unit housing wall 
         64  lower unit housing floor 
         65  lower unit housing roof bore 
         66  lower unit housing wall bore 
         67  lower unit housing floor bore 
         68  arrow 
         69  arrow 
         70  arrow 
         72  arrow 
         74  arrow 
         76  arrow 
         78  arrow 
         80  base foot rear spar 
         82  base foot side spar 
         84  base foot center spar 
         86  base foot reinforcement plate 
         88  actuator 
         90  arrow 
         92  arrow 
         94  arrow

Technology Classification (CPC): 1