DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Throughout the description of the several embodiments of the present invention, reference will be made to various elements, the construction of which is readily known to those skilled in the art. Accordingly, an exhaustive description of each and every component is not provided, only a description of those elements required for an understanding of the present invention.

[0039] FIG. 1 is a cross-sectional view of the watercraft of the present invention. In the illustrated embodiment, the watercraft 10 is a jet boat that includes a hull 20 with a bow 21 and a stern 22. While jet boats are the preferred focus for the present invention, those of ordinary skill in the art would readily recognize that the present invention may be applied to any style boat. Since the deck and hull configuration is not critical to an understanding of the present invention, the details of the deck and hull are omitted from the figures.

[0040] In the illustrated embodiment, the watercraft 10 of the present invention is powered by an internal combustion engine 30. While the internal combustion engine 30 is shown in a position where the bulk of the engine 30 extends toward the bow 21 of the watercraft 10, other arrangements are also possible without departing from the scope of the present invention. In particular, the body of the engine 30 may extend toward the stem 22 of the watercraft 10, which provides for a more compact construction of the drive unit if the watercraft 10 than the one illustrated in FIG. 1. Alternatively, the watercraft 10 could be powered by an inboard engine of any type, equipped with a propeller.

[0041] As shown, the engine 30 is vertically mounted along the longitudinal axis of the hull 20 near the stem 22 of the watercraft 10. The vertical orientation of the engine 30 and its position near the stem (or rear) 22 of the watercraft 10 are not required to practice the present invention, however. It would be understood by those skilled in the art that the engine 30 could be mounted in any other suitable location or in any alternative orientation. For example, the engine 30 could be oriented so that it is nearly horizontal in the center of a watercraft 10, which is a typical arrangement for personal watercraft.

[0042] In the embodiment illustrated in FIG. 1, the engine 30 is operatively connected to a jet propulsion unit 40 by an engine output shaft 35. Normally, the engine output shaft 35 is integrally formed with and extends from the crankshaft (not shown) of the engine 30. However, as would be appreciated by those skilled in the art, the engine output shaft 35 could be mechanically connected to the crankshaft so that the output shaft 35 comprises two or more shafts connected together. In addition, the shafts could be connected through a gearbox or clutch arrangement, if desired for the particular design of the watercraft 10. In other words, a multiple shaft arrangement may be disposed between the engine 30 and the jet propulsion unit 40.

[0043] FIGS. 2 and 3 illustrate the engine 30 and jet propulsion unit 40 in progressively greater detail. As shown, the jet propulsion unit 40 comprises a housing 41 defining a water passage 42 therein. Although the housing 41 can be integrally manufactured as part of the hull (as illustrated in FIG. 1), the housing 41 may be manufactured as part of the pump assembly 31 (see FIG. 16), which is integrated into the hull 20 along with the engine 30 during construction of the watercraft 10. The water passage 42 is a curved structure extending from a point at the bottom of the hull 20 to a point above the bottom, at the rear of the hull 20. The water passage 42 is open at both ends.

[0044] The rear of the water passage 42 includes a tunnel 55, which is the portion of the water passage above the ride plate 56 that surrounds the impeller 44.

[0045] The forward end of the water passage 42 (which is the end at the bottom of the hull 20) acts as an entry (or inlet) to the water passage 42. The rearward end of the water passage 42 (which is at the rear of the watercraft 10) acts as the discharge outlet for the water passage 42.

[0046] At the forward end of the water passage 42, a grate 46 is mounted to the hull 20 of the watercraft 10 or mounted to the pump assembly 31 directly. As illustrated, the grate 46 has openings such that the openings allow for a sufficient amount of water to flow into the water passage 42, but the structure of the grate 46 also is substantial enough to prohibit most foreign matter from entering the water passage 42. Alternatively, the grate 46 may be a solid component with perforations or slots, or the grate 46 may be a wire mesh.

[0047] In the embodiment depicted, a drive shaft 43 is rotationally coupled to the engine output shaft 35 at the forward end of the drive shaft 43. The drive shaft 43 is oriented substantially horizontally and extends through the housing 41 and into the water passage 42. Alternatively, the drive shaft 43 may be oriented in any position, as long as it is rotationally coupled to the engine output shaft 35. In this embodiment, the drive shaft is disposed parallel to the longitudinal center line of the watercraft 10. Alternatively, the drive shaft 43 may be angled to any degree relative to the centerline of the watercraft 10 (i.e., toward the port or starboard sides), depending on design considerations known to those skilled in the art. Also, while the drive shaft 43 shown is disposed horizontally within the hull 20, those of ordinary skill in the art would readily appreciate that the drive shaft 43 may be angled above or below horizontal without departing from the scope of the present invention.

[0048] Additionally, while the drive shaft 43 is shown as a unitary shaft throughout the figures, those skilled in the art would readily appreciate that the drive shaft 43 could comprise two or more shafts operationally connected to and aligned with one another. For example, the drive shaft 43 could include two or more shafts mechanically connected (e.g., by a flange) to one another. Alternatively, the drive shaft 43 could be constructed from several shafts operatively connected to one another through a gearbox or clutch, if desired.

[0049] In one embodiment, as illustrated, the drive shaft 43 and the engine output shaft 35 are rotationally coupled such that the drive shaft 43 and the engine output shaft 35 are not substantially parallel. That is, an angle 60 greater than zero is formed between the longitudinal axis of the engine shaft 35 and the longitudinal axis of the drive shaft 43. As defined herein, the angle 60 formed between the longitudinal axis of the engine output shaft 35 and the longitudinal axis of the drive shaft 43 is, by definition, between about 5 degrees to about 175 degrees, no matter the configuration between the engine 30 and jet propulsion unit 40. Preferably, the angle 60 is between about 45 degrees to about 135 degrees. More preferably, the angle 60 is about 90 degrees. In the case of a personal watercraft, the preferred angle is about 180 degrees.

[0050] In the illustrated embodiment, the engine output shaft 35 and the drive shaft 43 are located in the plane that vertically bisects the hull 20 from the bow 21 to the stern 22. Alternatively, the engine output shaft 35 and the drive shaft 43 may not be disposed within the plane that bisects the hull 20 from the bow 21 to the stern 22. One of ordinary skill in the art would understand that the engine output shaft 35 and the drive shaft 43 can be oriented in any position within the hull 20 of the watercraft 10 suitable for propulsion of the watercraft 10 without departing from the scope of the present invention.

[0051] At the other end of the drive shaft 43 is the impeller 44. In this embodiment, the impeller 44 is fixedly attached to the rearward end of the drive shaft 43. Alternatively, the impeller 44 may be attached to the drive shaft 43 at some intermediate point along the drive shaft 43 other than at the end. The impeller 44 may be of any suitable design known to one skilled in the art. As illustrated in FIG. 3A, the impeller 44 is held in the water passage 42 by a stator 51. The stator 51 is a housing around the impeller that is connected to the walls of the water passage 42 by three or four vanes 53. Alternatively, the impeller 44 may be supported by a wear ring (not shown).

[0052] The shaft guard 45 of the watercraft 10 of the present invention is illustrated in FIGS. 3A and 3B. In the illustrated embodiment, the shaft guard 45 covers substantially the entire portion of the drive shaft 43 that is inside the water passage 42. The forward end of the shaft guard 45 is attached to the housing 41 and extends away from the housing towards the impeller 44, but does not cover, or interfere with, the operation of impeller 44. Embodiments illustrating this particular construction are set forth below and are illustrated in FIGS. 13-15 herein.

[0053] As illustrated in FIGS. 3A and 3B, the shaft guard 45 extends from the housing 41 to the point where the impeller 44 is connected to the drive shaft 43. While this embodiment is preferred, it should be noted that the shaft guard 45 may only extend to an intermediate point along the drive shaft 43 between the housing 41 and the impeller 44. Regardless of the extent to which the shaft guard 45 extends along the drive shaft 43, the shaft guard 45 should be positioned to discourage debris from becoming wrapped around the drive shaft 43.

[0054] It is preferred that the shaft guard 45 extend around the entirety of the drive shaft 43 because the shaft guard 45 acts as a buffer between the drive shaft 43 and the water being pumped through the water passage 42.

[0055] In prior art jet-propelled watercraft that do not include any shaft guard 45, the drive shaft 43 tends to impart rotation to the water being pumped through the water passage 42. As a result, when the watercraft is turned, the rotational momentum of the water in the water passage 42 can negate some of the momentum imparted to the water being circulated at the impeller 44. This can result in a slight (but noticeable) drop in output propulsion power for the vehicle.

[0056] Additionally, any rotational energy imparted by the drive shaft 43 to the water being pumped through the propulsion unit 40 is energy “lost” by the propulsion unit 40. Ideally, to maximize thrust, the energy imparted by the impeller 44 to the water would direct the water in a straight line from nozzle 48. Of course, the impeller 44 naturally imparts at least some rotational motion to the water in the water path 42. This motion is directed around the drive shaft 43 and not out of the nozzle 48. Accordingly, this energy is lost—the energy is not being utilized to propel the watercraft 10. The drive shaft 43 also can impart some rotational energy to the water in the water passage 42, contributing to the losses inherent in the jet propulsion unit 40. The addition of the shaft guard 45, especially if it covers the full length of the drive shaft 43 in the water passage 42, helps to minimize rotational losses because the shaft guard 45 acts as a barrier to prevent the drive shaft 43 from contributing to rotational energy losses.

[0057] If the shaft guard 45 extends from the housing 41 to the impeller 44, the entirety of the drive shaft is covered. This minimizes energy losses due to rotational energy being imparted to the water in the water passage 42. Of course, the drive shaft 43 need not be fully encased by the shaft guard 45, as would be appreciated by those skilled in the art.

[0058] The shaft guard 45 is attached to the housing 41 by an adhesive 47, as illustrated by FIG. 4. The adhesive may be of any type suitable for holding the shaft guard 45 in fixed relation to the drive shaft 43.

[0059] Alternatively, the shaft guard 45 may be affixed to the housing 41 through a suitable flange 49, as illustrated by FIG. 5. The flange 49 may be affixed both to the shaft guard 45 and to the housing 41 by a suitable adhesive. FIG. 6 shows a further embodiment where a flange 49′ is positioned on the interior of the shaft guard 45.

[0060] Alternatively, the connection may be made by any other suitable fastener such as the combination of nuts and bolts.

[0061] In the embodiment depicted in FIG. 3A, the shaft guard 45 completely surrounds the circumference of the drive shaft 43. In this regard, the shaft guard 45 is a tube that completely surrounds the circumference of the drive shaft 43. Alternatively, the shaft guard 45 can partially surround the circumference of the drive shaft 43 such that only the bottom half of the drive shaft 43 is covered, leaving the top exposed.

[0062] The shaft guard 45 also may have any cross-sectional shape, e.g., a circle, an ellipse, a triangle, a rectangle, an octagon, or the like, or any portion thereof. The shaft guard 45 shown throughout the figures has a cross-sectional shape of a circle. The shaft guard 45 can be perforated or slotted or be configured as a mesh or a cage. In the illustrated embodiment, the shaft guard 45 is solid (i.e., not perforated). In addition, the shaft guard 45 is preferably streamlined to minimize turbulence as the water flows around its exterior surface.

[0063] The shaft guard 45 can be formed from any material that will survive a salt water environment for a sustained period of time. Preferably, the shaft guard 45 is made from a plastic or a composite material (e.g., the material used to construct the housing 41). Alternatively, the shaft guard 45 is made from aluminum, stainless steel, or the like.

[0064] In another embodiment, illustrated by FIGS. 3A and 3B, the rearward end of the shaft guard 45 is attached to the drive shaft 43 by a supporting member 50 such that the drive shaft 43 is free to rotate. In this embodiment, the supporting member 50 is a bushing, which may or may not be lubricated. The bushing 50 permits free rotation of the drive shaft 43 while also maintaining the orientation of the drive shaft 43 roughly in the center of the guard shaft 45. Alternatively, the supporting member 50 may be a bearing such as a ball bearing, which may be open or closed, lubricated or not.

[0065] A further embodiment of the present invention is illustrated in FIGS. 7-11. As shown, the shaft guard 72 is essentially a cylindrical structure with an angled end 74 and a end 76 that has been cut essentially perpendicularly to the longitudinal axis 78 of the shaft guard 72. The angled end 74 is shaped to mate with the housing 41 of the water passage 42 in the same manner that shaft guard 45 mates with the housing 41 as illustrated in FIGS. 3A, 4, 5, and 6. As illustrated in FIG. 8, the angled end 74 appears elliptical in shape when viewed end-on. Since the other end 76 is cut substantially perpendicularly to the longitudinal axis 78 of the shaft guard 72, that end 76 has a circular cross-section when viewed end-on, as illustrated in FIG. 9.

[0066] The shaft guard 72 is constructed from a material that is resistant to corrosion in a salt water environment. Specifically, the shaft guard 72 is constructed from stainless steel, aluminum or a material containing aluminum. More specifically, the shaft guard 72 is constructed of 304 stainless tubing. Alternatively, the shaft guard 72 may be constructed from a plastic or composite material so long as the material can withstand: (1) the forces generated within the water passage 42 during operation of the watercraft 10 and (2) the forces exerted by an elongated object that becomes entangled in the impeller 44 and wraps around the shaft guard 72.

[0067] To attach the angled end 74 of the shaft guard 72 to the housing 41 within the water passage 42, a pair of eyelets 80 are affixed thereto or are fashioned as a part thereof. Fasteners, such as bolts (not shown) are inserted through the eyelets 80 to attach the shaft guard 72 to the housing 41. The eyelets 80 are made from a corrosion-resistant material, such as stainless steel, aluminum or a material containing aluminum. Specifically, the eyelets 80 are made from 304 stainless steel. Alternatively, the eyelets 80 could be fashioned from a plastic or composite material so long as the material can withstand the dynamic forces within the water passage 42. In the embodiment shown, the shaft guard 72 and eyelets 80 are made of 304 stainless steel. When made of steel, the eyelets 80 are welded to the angled end 74 of the shaft guard 72. If manufactured as a part of the shaft guard 72, the eyelets 80 understandably will be made from the same material as the shaft guard 72.

[0068] To provide support for the shaft guard at the transversely cut end 76, a support member 82 is provided. The support member 82 preferably is a bushing that is press-fitted into the end 76. The bushing 82 preferably is constructed from bronze, stock SAE 841. As would be understood from the FIG. 11, the interior surface of the bushing 82 engages the exterior surface of the drive shaft 43. While a bronze bushing is preferred for the shaft guard 72 of the present invention, alternatively, a bearing could be used.

[0069] FIG. 13 illustrates a side view of another alternative for connecting the shaft guard 45 to the hull 41. Here, the shaft guard 45 is welded to a flat washer or collar 84. The collar 84, in turn, is welded to two keys 86, 88 that interlock with the through-hull fitting 90. The through-hull fitting 90 is a member that extends through the hull to permit the drive shaft 43 to be operatively connected to the engine 30.

[0070] Since the through-hull fitting 90 is connected to the hull 41 so that the through-hull fitting 90 cannot rotate, the keys 86, 88 that interlock with the through-hull fitting 90 prevent the shaft guard 45 from rotating. To permit the drive shaft 43 to rotate with respect to the shaft guard 45, two support members 82, preferably bushings, are disposed within the shaft guard 45 at forward and rearward ends thereof. While a bronze bushing is preferred for the support member 82 of the present invention, alternatively, a bearing could be used.

[0071] To prevent the shaft guard 45 from moving axially along the drive shaft 43, a compression spring 92 is positioned between the collar 84 and a carbon seal 94. The compression spring 92 biases the shaft guard 45 in a forward direction. In addition, a C-clip also assists in maintaining the shaft guard 45 in its forward direction by preventing the carbon seal 94 from slipping rearwardly along the drive shaft 43.

[0072] FIG. 14 is a side view of yet another embodiment of a connection between the shaft guard 45 and the through-hull fitting 90. Here, instead of a pair of keys 86, 88 that hold the shaft guard 45 in a fixed relationship to the hull 41, three bent spring steel forms 96 are used. To simplify illustration of this connection, only two bent steel spring forms 96 are illustrated in FIGS. 14 and 15. As would be appreciated by those skilled in the art, while this embodiment contemplates reliance on three bent steel spring forms, any number greater than one is all that is required to hold the shaft guard 45 in a fixed relationship to the through-hull fitting 90.

[0073] As illustrated in FIG. 14, the bent steel spring forms 96 have a forward end 97 and a rearward end 98. The forward ends 97 engage small holes 99 in the through-hull fitting 90. The rearward ends 98 of the bent steel spring forms 98 engage notches (or other similar structure(s) in the rear end of the through-hull fitting 90 to maintain the shaft guard 45 in a fixed positional relationship thereto.

[0074] FIG. 15 illustrates the shaft guard 45 and bent steel spring forms 96 as they would appear when disconnected from the through-hull fitting 90. As illustrated here and also in FIG. 14, the bushing 82 may be bronze. However, as would be appreciated by those skilled in the art, any alternative support, such as a bearing, could be substituted therefor without deviating from the scope of the present invention.

[0075] From the invention just described, it will be obvious that the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.