Water jet propulsion apparatus with inboard mounted power source

[0002] This invention generally relates to pump jet apparatus which are mounted to the hull of a boat or other water craft. In addition, the invention relates to mechanisms for transmitting motive power from an inboard marine engine to an outboard pump jet.

[0003] It is known to propel a boat or other water craft using a pump jet apparatus mounted to the hull, with the powerhead being placed inside (inboard) the hull. The drive shaft of the pump jet apparatus is coupled to the output shaft of the inboard motor. The impeller is mounted on the drive shaft and housed in a jet propulsion pipe or water tunnel.

[0004] To facilitate use of pump jet-propelled boats in shallow water, it is known to mount the pump jet at an elevation such that the pump jet does not project below the bottom of the boat hull. This can be accomplished, for example, by installing a duct in the stern of the boat, the duct being arranged to connect one or more inlet holes formed in the bottom of the hull with an outlet hole formed in the transom. The pump jet is then installed outside the hull in a position such that the pump jet inlet is in flow communication with the duct outlet at the transom. Such a system is shown in Australian Patent Specification No. 262306, published in 1963. Alternatively, the pump jet can be installed inside the duct built into the hull, as shown in U.S. Pat. No. 5,181,868.

[0005] Alternatively, a water tunnel can be formed in the stern of the boat hull, the water tunnel having a height which gradually increases from the hull bottom at a point in front of the transom to a maximum height at the transom. In one type of design, the pump jet is placed so that its inlet is in flow communication with the outlet of the water tunnel. One example of this type of system is shown in Italian Publication No. 724662.

[0006] In another type of design, part of the pump jet apparatus is installed inside the hull while the remaining part penetrates the transom and extends to the rear of the hull. An inlet housing of the pump jet has a horizontal opening and an inclined water tunnel for guiding water to the impeller. The horizontal opening of the inlet housing is mounted in a hole in the bottom or near the bottom of the hull. A similar design is disclosed in Swiss Patent No. 481788.

[0007] In many pump jet units powered by inboard engines, the drive shafts and pump mountings (which must penetrate the hull) are placed below the waterline. Such a mounting system has the disadvantage that various gaskets and seals are required to ensure the integrity of the installation. Leakage at any of the mounting and shafting locations can be disastrous.

[0008] In addition, in the event that the inlet to the pump jet becomes clogged with debris, permanent mounting of the pump jet makes it difficult to clean out the debris from the inlet. In some instances, removal of the ingested or entangled debris requires that the boat user enter the water or even that the boat be lifted out of the water.

[0009] Thus, an arrangement for mounting a pump jet in flow communication with a water tunnel wherein the hull penetrations are located above the waterline provides an advantage. Further, it would be advantageous to mount the pump jet in such a way that it can be removed from its position in flow communication with the water tunnel and into a position which allows easy access to any debris clogging the pump jet inlet.

[0010] One aspect of the present invention encompasses a boat or other water craft having a marine propulsion system comprising an inboard engine, an outboard pump jet apparatus and a transom plate on which the pump jet apparatus is pivotably mounted. In accordance with one preferred embodiment of the invention, the boat hull bottom has a water tunnel formed therein, the transom plate has a tube portion in flow communication with the water tunnel, and the pump jet apparatus has an inlet which, in the operating position of the pump jet, is in flow communication with the tube portion of the transom plate.

[0011] The present invention is also directed to an arrangement for providing a boat or other water craft with a pump jet apparatus which is selectively movable from an operating position to a service position and vice versa. In the operating position the pump jet inlet is inaccessible to an occupant of the boat, whereas in the service position the pump jet inlet is accessible, enabling a boat occupant to clear debris from the pump jet inlet. In accordance with a preferred embodiment, the pump jet apparatus is pivotably mounted on the transom plate. When the pump jet is pivoted away from the operating position, the pump jet inlet is disengaged from the tube portion of the transom plate, into a position which allows easy access to remove the debris clogging the pump jet inlet.

[0012] In accordance with a further preferred embodiment, the drive shaft connecting the inboard engine to the outboard upper gear assembly and the bolts used to mount the transom plate each penetrate the transom at an elevation above the waterline. This has the benefit that failure of any gasket or seal will not cause disastrous leakage so long as the penetrations remain above the waterline.

[0013] Another aspect of the invention encompasses a transom plate for mounting on a boat transom. In accordance with a preferred embodiment, the transom plate comprises a plate having upper and lower portions, and a tube portion connected to the lower portion of the plate. The transom plate further comprises first and second journal boxes connected to the upper portion of the plate for housing a compound gear and various bearings which allow the pump jet apparatus to pivot relative to the transom plate.

[0014] The invention is further directed to a pump jet arrangement for mounting on a transom of a boat hull, comprising: a rotor shaft; a rotor (impeller) mounted on the shaft; a drive train coupled to the rotor shaft; a mounting plate having holes for mounting on a transom of a boat hull; a first water tunnel portion connected to the mounting plate and having an inlet and an outlet; a drive train casing pivotably coupled to the mounting plate and encasing a vertical portion of the drive train, the drive train casing being pivotable relative to the mounting plate between first and second positions; and a second water tunnel portion connected to the drive train casing and having an inlet and an outlet, the rotor being housed inside this second water tunnel portion. The inlet of the second water tunnel portion and the outlet of the first water tunnel portion are in abutment when the drive train casing is in the first position and are not in abutment when the drive train casing is in the second position. The inlet of the second water tunnel portion and the outlet of the first water tunnel portion present substantially the same cross-sectional shape to water flowing therethrough.

[0015] Another aspect of the invention is the provision of a sealed pivot arrangement which allows the drive train casing of the pump jet apparatus to pivot relative to the mounting plate. The horizontal portion of the drive train penetrates the drive train casing from the side, along the axis of pivoting. Thus the drive train casing and the horizontal portion of the drive train will have relative rotation but no relative displacement during pivoting of the drive train casing.

[0016] FIG. 1 is a schematic showing an isometric view of the stern a boat with an inboard engine and an outboard pump jet pivotably mounted on a transom plate in accordance with one preferred embodiment of the invention. Part of the transom is cut away to reveal the inboard engine, while the outline of the water tunnel is partly indicated by the dashed curved line.

[0017] FIG. 2 is a schematic showing a sectional elevational view of the preferred embodiment depicted in FIG. 1. The service position of the pump jet apparatus is indicated by dashed lines.

[0018] FIG. 3 is a schematic showing an isometric view of the gear drive train in accordance with the preferred embodiment shown in FIGS. 1 and 2. The outlines of the transom plate and the pump jet are shown in dashed lines.

[0019] FIG. 4 is a schematic showing a sectional elevational view of pat of an exemplary pump jet apparatus which can be pivotably mounted on the transom plate disclosed herein.

[0020] FIG. 5 is a schematic showing a sectional elevational view of the pivoting arrangement by which the drive train casing pivots relative to the mounting plate in accordance with the preferred embodiment.

[0021] FIG. 6 is a schematic showing an isometric view of the transom plate and attached pump jet apparatus according to the preferred embodiment. The outline of the water tunnel formed in the boat hull is shown in dashed lines.

[0022] FIG. 7 is a schematic showing an isometric view of a boat in accordance with the preferred embodiment, wherein the transom plate mounting holes and the drive shaft penetration are located above the waterline.

[0023] In accordance with the preferred embodiment shown in FIGS. 1 and 2, a boat has a hull 2 with a water tunnel 4 formed in its stern. The water tunnel 4 has a height which gradually increases from its starting point to a maximum height located at the transom 5. It should be understood that the water tunnel 4 forms a recess in the transom 5, as best seen in FIG. 7. Preferably, the water tunnel 4 is located along the centerline or keel of the hull 2. However, it will be readily appreciated that more than one water tunnel can be formed in the hull if multiple stern drive units are installed, one water tunnel for each pump jet.

[0024] In addition, the preferred embodiment comprises an outboard pump jet 6 powered by an inboard engine 8. Preferably the engine 8 is mounted on a pair of hull stringers 10 by means of a plurality of motor mounts 12. Also shown in FIGS. 1 and 2 is a transom plate 14, comprising a plate 15 having a lower portion connected to a tube portion 16 and an upper portion connected to an upper gear housing 26. The tube portion 16 effectively becomes an extension of the water tunnel 4, i.e., is in flow communication with the water tunnel 4. Preferably the shape of the tube portion 16, at the inlet where it meets the water tunnel 4, should conform to the shape of the latter, thereby allowing water to flow along a smooth transition from the water tunnel 4 into the tube portion 16. Similarly, the inlet to the pump jet 6 is in flow communication with the outlet of tube portion 16. Thus tube portion 16 of the transom plate 14 guides flowing water from the water tunnel 4 into the pump jet 6. The water exits the pump jet 6 via a conventional steering nozzle 20. The water flow exiting the steering nozzle 20 can be reversed by activation of a conventional reverse gate 22, which causes exiting water to flow through a slot 21 formed in the steering nozzle and in a reverse direction. The steering and shifting controls for controlling the positions of the steering nozzle and the reverse gate comprise well-known structures such as cables, links and levers, the bulk of which are not shown in the drawings to avoid unnecessary complication in the depiction of the preferred embodiment.

[0025] The pump jet 6 is preferably pivotably coupled to the upper gear housing 26 of the transom plate 14 via a drive train casing 24 (see FIG. 1). Casing 24 houses the upper portion of the vertical gear drive train; the upper gear housing 26 houses the aft portion of the horizontal drive train which couples the pump jet to the inboard motor 8. The upper gear housing 26 rotatably supports the drive train casing 24 to allow tilt pivoting of the jet pump 6 and drive train casing 24, hereinafter collectively referred to as the “pump jet apparatus”.

[0026] Referring to FIGS. 2 and 3, a preferred embodiment of the drive train from the engine 8 to the pump jet 6 will now be described. This drive train powers the pump jet in the operating position, but allows the pump jet to be tilted from the operating position to the service position, the latter being indicated by dashed lines in FIG. 2. Referring to FIG. 2, the drive train comprises an engine output shaft 50 coupled to a horizontal drive shaft 28 by means of a coupling 52. A vibration damper 51 made of rubber is installed inside the coupling, i.e., surrounding a splined end of drive shaft 28. The drive shaft 28 penetrates the transom 5 via a hole 60, penetrates the plate 15 via a hole 61 and extends into the upper gear housing 26. The interface between the transom plate and the transom and surrounding the hole 60 is sealed by a seal 54.

[0027] A bevel drive gear 30 is mounted to the end of drive shaft 28. The teeth of bevel drive gear 30 engage a large-diameter bevel gear 32 of a compound gear, which also has a small-diameter bevel gear 36 which is coupled to bevel gear 32 (best seen in FIG. 5). Thus rotation of drive gear 30 causes bevel pinion 36 to rotate. The teeth of bevel gear 36 mesh with a bevel gear 38 mounted to the end of a vertical drive shaft 40, which penetrates the pump jet housing. The opposite end of the vertical drive shaft 40 has a bevel gear 42 mounted thereto. The bevel gear 42 in turn meshes with a bevel gear 44 mounted on a rotor shaft 46 which has a portion extending forward of the vertical shaft 40. The rotor (i.e., impeller) 48 is mounted on the forward end of the rotor shaft 40 and may have a conventional structure. The rotor shaft 40 is supported by bearings (not shown) arranged inside a hollow hub 66 having a streamlined exterior surface. The hub 66 is surrounded by a housing 64 having an inlet which is in flow communication with the outlet of tube portion 16 of the transom plate. The interface between the housing 64 and the tube portion 16 is sealed by a seal 56. The interior surface of a housing 64 is streamlined, so that the opposing surfaces of the housing 64 and hub 66 define a circumferential passageway 68 through which the impelled water flows. The housing 64 and 66 are preferably connected by a plurality of stator vanes 70.

[0028] In accordance with the foregoing drive train, the engine 8 drives the rotor shaft 46 to rotate via drive shafts 28 and 40, and gears 30, 32, 36, 38, 42 and 44. Rotation of the rotor shaft 46 in turn causes the rotor 48 to rotate. During rotation, the angled blades of the rotor 48 impel water in the aft direction through the circumferential passageway between housing 64 and hub 66. The stator vanes 70 function to redirect the swirling flow out of the rotor and eliminate swirl. Provided that the reverse gate 22 is in the raised position, the water exits the steering nozzle 21 as a downstream jet. FIG. 2 shows the reverse gate 22 in the lowered position, which would cause the flow to reverse, as previously described.

[0029] As best seen in FIGS. 2 and 6, the preferred embodiment of the transom plate further comprises a shovel-shaped scoop 65 which projects into and under the water tunnel 4 in the hull 2. Scoop 65 serves to guide water into the tube portion 16 of the transom plate.

[0030] In accordance with the preferred embodiment, the pump jet apparatus can be pivoted between an operating position (shown by solid lines in FIG. 2) and a service position (shown by dashed lines in FIG. 2). When the pump jet apparatus is pivoted from the operating position to the service position, the bevel gear 38 will travel freely along the periphery of gear 36, which is stationary. Thus the gear train poses no impediment (other than frictional forces) to tilt pivoting of the pump jet apparatus about a horizontal pivot axis. Conventional latching mechanisms may be used to latch the pump jet in its operating or service positions. Optionally, a handle or eyehook may be attached to the drive train casing 24 or to the pump jet housing for facilitating tilt pivoting of the pump jet by a person standing in the boat stern.

[0031] The respective geometries and the positional relationship of the drive train casing 24 and the upper gear housing 26 can be seen in FIG. 4. The upper gear housing 26 comprises a pair of pivot supports 18 and 18′. The drive train casing 24 is received between the pivot supports. Each pivot support has a respective opening 76, while the opposing walls of casing 24 have respective openings 78, only one of which is visible in FIG. 4. The openings 76 have the same diameter and are coaxial. Similarly, the openings 78 have the same diameter as that of openings 76 and are coaxial. The bevel gear 32 of the compound gear is rotatably housed in the recess 72 of pivot support 18′. An opening 74, which communicates with recess 72, is provided in the wall of pivot support 18′ to allow the outer perimeter of the drive gear 30 to penetrate into the recess 72 and mesh with the outer perimeter of the bevel gear 32.

[0032] The arrangement for pivotably coupling the drive train casing 24 to the upper gear housing 26 is generally shown in FIG. 5. In the assembled condition, the openings 76 of the upper gear housing 26 and the openings 78 of the drive train casing 24 are mutually coaxial. One bearing retainer 80 in the shape of a bushing is fastened by fasteners 82 to the pivot support 18, while another bearing retainer 84 in the shape of a bushing is fastened by fasteners 82 to the pivot support 18′. The bearing retainer 78 retains a bearing assembly 86 which supports a journal 88 of a compound shaft. The bearing retainer 82 retains a bearing assembly 90 which supports a journal 92 of the compound gear. The compound shaft also includes a small-diameter shaft 94. Both ends of shaft 94 (not visible in FIG. 5) are splined. One splined end fits inside a splined bore in the journal 88; the other splined end fits inside a splined bore in the compound gear.

[0033] In response to rotation of the drive gear 30, the compound gear and compound shaft assembly rotates about axis A. The meshing of bevel gear 36 with bevel gear 38 causes the vertical drive shaft 40 to be driven. During this rotation (and at all times), the fastened bearing retainers 80 and 84 are stationary. In accordance with the preferred embodiment of the invention, the drive train casing 24 is rotatable on the bearing retainers, thus enabling the casing 24 to pivot relative to the transom plate in the manner depicted in FIG. 2. The pivot axis is axis A in FIG. 5. Seals 96 and 98 serve to seal the interfaces between the drive train casing and the bearing retainers, thereby sealing against water leakage into the drive train casing. Because the pivot axis and the axis of the compound shaft/compound gear assembly are coaxial, the beveled teeth of the bevel gear 38 will intermesh with and travel along the beveled perimeter of bevel gear 36 when the drive train casing 24 is pivoted.

[0034] In accordance with the preferred embodiment, the transom plate of boat 58 is mounted to the transom so that the mounting holes 61 (see FIG. 7) are located above the waterline 62 in the hull. The circle designated by numeral 60 in FIG. 7 represents the shafting hole in the hull, which is penetrated by the drive shaft. However, if additional securement at lower positions on the transom is required, it is within the scope of the invention to mount the transom plate using extra mounting holes located below the waterline and therefore suitably sealed against leakage of water into the hull.

[0035] While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the essential scope thereof. For example, the tube portion of the transom plate may have a cross section which is not circular. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.