Abstract:
A marine jet drive, for a boat having a transom and a drive shaft extending through the transom, the boat afloat in a water body, includes a support casing disposed aft of the transom and a pump shaft within the support casing, the pump shaft having an end connectable to the drive shaft. The jet drive includes a jet pump having a chamber and a blade coupled to a portion of the pump shaft extending into the chamber. The chamber is attached to and supported by the support casing aft of the support casing. The chamber has an inlet for receiving water into the chamber and an outlet. The blade is coupled to the portion of the pump shaft for co acting with the chamber to draw water into the chamber inlet and discharge water in a reactive jet out the chamber outlet to reactively propel the boat.

Description:
BACKGROUND OF THE INVENTION 
     Jet pumps are previously known for the propulsion of high-speed watercraft. In one type of installation, the hull of the watercraft is provided with an inlet aperture through the bottom of the hull adjacent to the transom. An axial or centrifugal pump takes suction through the inlet and discharges the water to a pressure chamber. The pressure chamber outlets an airborne jet of water. The resulting reactive force provides propulsion to the high-speed boat. Deflectors are typically mounted to the jet pump and are used to change the direction of the airborne jet of water thus altering the reactive force of the jet to steer the boat. Deflectors are commonly used to redirect the jet of water in a forward direction allowing the boat to back up. See, for example, the following U.S. Pat. Nos. 7,220,154; 4,073,257; and 3,336,752; the disclosures of which are incorporated by reference. 
     It is also known to provide jet pumps to outboard motors. Typically, a pump inlet is provided at the bottom of the motor adjacent to the surface of the water. The inlet communicates to an axial or centrifugal pump which discharges to an outboard motor-mounted pressure chamber. The pressure chamber discharges an airborne water jet at an outlet of a outboard motor. The reactive force acting on the outboard is commonly used to propel a small watercraft, typically at high speeds or in shallow water conditions. See, for example, the following U.S. Pat. Nos. 4,538,996; 4,281,996; and 3,105,353; the disclosures of which are incorporated by reference. 
     In my U.S. Pat. No. 4,645,463 entitled Marine Outdrive Apparatus, I disclosed marine outdrive attached to the transom of a boat having an inboard engine. The marine outdrive includes a tubular support casing securable to and extendable rearwardly of the boat&#39;s transom and having a ball socket at its rear end. The ball socket receives a ball at the front end of a tubular, propeller shaft carrier. A drive shaft connectable to the inboard engine is journaled in the support casing. A propeller shaft is journaled in the propeller shaft carrier and has a propeller mounted thereon at the rear end of the propeller shaft carrier. The propeller shaft transmits thrust to the ball at a conical thrust bearing. A double Cardan joint—sometimes called a universal joint—couples the two shafts together to transmit torque between the shafts, the center of such joint substantially coinciding with the point about which the ball pivots within the ball socket. Hydraulic steering cylinders are attached to the propeller shaft carrier to pivot the latter about a steering axis extending through the pivot point of the ball. A hydraulic trim cylinder extends between the transom and the propeller shaft carrier to swing the propeller shaft carrier about a laterally extending trim axis extending through the pivot point of the ball. The upper end of the trim cylinder is pivotally mounted on the transom at a location above and vertically aligned with the pivot point of the ball or at a location above and forwardly of such pivot point. Improved fins are provided on the propeller shaft carrier near the propeller to stabilize the boat. The drive shaft of the inboard motor can be directly connected to the joint or offset from the joint and coupled thereto by a vertically extending transmission. 
     BRIEF SUMMARY OF THE INVENTION 
     A marine jet drive, for a boat having a transom and a drive shaft extending through the transom, the boat afloat in a water body, includes a support casing disposed aft of the transom and a pump shaft within the support casing, the pump shaft having an end connectable to the drive shaft. The jet drive includes a jet pump having a chamber and a blade coupled to a portion of the pump shaft extending into the chamber. The chamber is attached to and supported by the support casing aft of the support casing. The chamber has an inlet for receiving water into the chamber and an outlet. The blade is coupled to the portion of the pump shaft for co acting with the chamber to draw water into the chamber inlet and discharge water in a reactive jet out the chamber outlet to reactively propel the boat. In one embodiment, the tubular support casing extends from a ball socket and power source connect shaft at the boat transom. The ball socket at the transom captures the ball and permits the tubular support casing to be adjustable in orientation in two directions of freedom about the ball socket. A double Cardan joint substantially coincident to the center of pivot of the ball and ball socket transmits torque between the power source shaft and drive shaft in the tubular support casing. At least one hydraulic trim cylinder extends between the transom and the tubular support casing to orient the jet pump through the pivot point of the ball. In operation, by adjustment of the tubular support casing and contained shaft, variable orientation of the jet pump at its intake and outlet is achieved allowing dynamic optimization of jet pump orientation relative to boat trim behind the boat transom during jet pump operation. 
     Over a conventional jet drive, the tubular support casing containing the drive shaft extending beyond the transom forms the sole support to the chamber. In some embodiments, the chamber is thus supported by the tubular support casing in the water body astern of the transom with both the chamber inlet and outlet of the jet pump disposed behind the transom. 
     In an embodiment, the marine jet drive may also have two dynamic positioning cylinders for moving the marine jet drive relative to the transom to allow for changes in the vertical and horizontal orientation of the marine jet drive in two directions of freedom. This enables movement of the marine jet drive to both change orientation of the pump with respect to the trim of the boat and allow jet pump side to side movement to provide an assist to boat steering. 
     In the prior art, water is transported from the water body to the jet drive in the boat. Here, the jet drive is moved to the water body from the boat. Change of jet drive immersion can occur with change of boat trim as the boat hull moves from standing displacement immersion in the water body to plane over the top of the water body. Further, the suspension of the jet drive augments jet drive boat steering. While conventional jet drives provide for boat steering by using steering deflectors at the discharging jet, the present jet drive can steer the entire immersed jet drive while still using standard deflectors. There results a jet drive having enhanced maneuvering characteristics compared to conventional jet drives. 
     The chamber may be flanked by fins or side panels adjacent the inlet. Dependent upon chamber orientation, these fins or side panels may serve to crowd water into the inlet during boat operation. In an additional embodiment, there may also be a scoop positioned proximate the water inlet opening. It has been discovered that performance can be improved by dynamically adjusting the flow of water into the jet pump intake. Such adjustment of water flow into the jet pump intake, such as through the change in orientation of the scoop, can typically be in response to the vertical orientation, or elevation, of the jet pump and the boat speed. The scoop can be individually adjustable with respect to the chamber. 
     Other features, aspects and advantages of the present invention can be seen on review of the figures, the detailed description, and the claims which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a perspective top port side view of a boat having a transom and a marine jet drive mounted to and extending aft of the transom with arrows demonstrating possible movements of the jet drive with respect to the boat; 
         FIG. 2  is a section taken through the structure of  FIG. 1  illustrating the ball socket, the power source connected shaft, the ball captured within the socket, the tubular support casing extending from the ball, the drive shaft within the tubular support casing, the chamber fastened to and supported by the tubular support casing, the chamber inlet, the chamber outlet, and shaft driven pump within the chamber; 
         FIG. 3  is an enlarged starboard side view of another embodiment of a marine jet drive similar to that of  FIG. 1  but including an adjustable scoop and a pair of downwardly extending fins on the sides of the scoop; 
         FIG. 4  illustrates perspective view of the underside of the novel jet pump chamber of the embodiment of  FIG. 3  showing the fins on either side of the chamber inlet, the fins here being parallel, extending vertically down into the water, and the jet drive being canted with respect to boat motion to crowd water into the inlet when the chamber moves through the water body, this embodiment also showing a scoop in the vicinity of the chamber inlet and between the fins, the scoop here shown being adjustable relative to the inlet to optimally meter water into the chamber of the jet drive; and 
         FIG. 5  illustrates a perspective view similar to  FIG. 4  of another embodiment without the scoop but with fins flared downwardly and outwardly from the vertical and inwardly in the aft direction to direct water into the pump chamber opening. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description will typically be with reference to specific structural embodiments and methods. It is to be understood that there is no intention to limit the claims to the specifically disclosed embodiments and methods but that the claims may be practiced using other features, elements, methods and embodiments. Preferred embodiments are described to illustrate, not to limit the claims. Those of ordinary skill in the art will recognize a variety of equivalent variations on the description that follows. Like elements in various embodiments are commonly referred to with like reference numerals. 
     Referring to  FIG. 1 , marine jet drive J is intended for use with a boat B afloat in a water body W. With additional reference to  FIG. 2 , boat B has a transom T and a drive shaft S and tubular support casing C extending outwardly from the transom in the aft direction. Drive shaft S is contained within tubular support casing C (see  FIGS. 1 and 2 ). Jet pump P has a pump chamber  14  fastened to the distal end of the tubular support casing C remote from the boat. The pump chamber has an inlet  16  for receiving water and an outlet  18  for discharging a jet of water  20  for reactive propulsion of the boat, both pump chamber inlet and outlet being behind the boat transom. A pump impeller  22  within the chamber  14  is driven by the drive shaft S. The pump impeller  22  coacts with the chamber  14  to impel water from the chamber inlet  16  to the chamber outlet  18  to produce the jet  20  that reactively drives the boat. Jet pump P could be another type of axial pump, such as one using a propeller instead of an impeller. Also, impeller  22  could be a mixed flow impeller. In some examples, the blade is a propeller blade in which the tip of the propeller blade is trimmed off to lie close to the inner surface of chamber  14 . 
     In the embodiment shown here in  FIG. 2 , the tubular support casing C extends from a ball socket  24  and power source connect shaft  26  at the boat transom T. The ball socket  24  at the transom captures tubular support casing ball  28  and permits the tubular support casing C to be adjustable in orientation in two directions of freedom about the ball socket  24 . A double Cardan joint  30  substantially coincident to the center of pivot of tubular support casing ball  28  and ball socket  24  transmits torque between the power source drive shaft and pump shaft in the tubular support casing. Thrust from the jet pump J to boat B occurs solely through tubular support casing ball  28  and ball socket  24 . 
     Referring to  FIGS. 2 and 3 , provision is made for movement of the marine jet drive J relative to transom T. At least one hydraulic trim cylinder  32  extends between the transom T and the tubular support casing C to orient the jet pump P through the pivot point of ball socket  24  and tubular support casing ball  28 . Preferably, there is a second hydraulic trim cylinder  34  which in extension with hydraulic cylinder  32  orients jet pump P relative to transom T. In addition to hydraulic trim cylinders, other types of trim actuators can also be used. This enables movement of the marine jet drive to both change orientation of the pump with respect to the trim of the boat through trim cylinder  34  and allow jet pump side to side movement through trim cylinder  32  to provide an assist to boat steering. Examples of dynamic positioning apparatus are shown used with surface piercing propeller drives in the inventor&#39;s U.S. Pat. No. 7,335,074 and the patents cited therein, the disclosure of which is incorporated by reference. 
     Outlet  18  is created at a discharge assembly  42  including a discharge nozzle  44  which can be moved side to side for steering. Discharge nozzle  44  emits water jet  20  to provide propulsion for boat B. Jet discharge assembly  44  may also include a reverse thrust deflector  46  that can be pivoted downwardly to allow boat B to move in reverse. Jet discharge assembly  42  may also include additional steering deflectors. The operational lines and cables used to steer jet discharge assembly  42  and operate reverse thrust deflector  46  are not shown for clarity of illustration. The construction of jet discharge assembly  42  can be conventional. Jet discharge assemblies  42  are typically sold as portions of conventional watercraft waterjets such as those made by Doen Waterjets PTY LTD of Victoria, Australia. 
     Referring to the view of  FIG. 4 , chamber  14  at inlet  16  may be flanked by fins  36  adjacent the inlet  16 . With chamber orientation slightly depressed relative to the surface of water body W, these fins  36  serve to crowd water into the inlet during boat operation. Fins  36  in  FIG. 4  are shown depending vertically downward relative to jet pump P. There may also be a scoop  38  positioned proximate the inlet  16 . The scoop may either be fixed or individually adjustable with respect to the chamber  14 . As indicated by arrow  39  in  FIG. 3 , scoop  38  is adjustable through hydraulically actuated lever  40 . The actuator for lever  40  is not illustrated for clarity of illustration. 
     Referring to  FIG. 5 , fins  36 ′ may be other than vertical. Here fins  36 ′ are shown flared outward from inlet  16  at angles ranging between about 15-20° from vertical. Again, this flaring together with the orientation of jet pump P allows water to be crowded into the inlet  16  of jet pump P. Fins  36 ′ also converge in the aft direction to define an included angle of about 40°. 
     In operation, by adjustment of the tubular support casing C and contained shaft S using trim cylinders  32 ,  34 , variable orientation of the jet pump J at its inlet  16  and outlet  18  is achieved allowing dynamic optimization of jet pump orientation relative to boat trim behind the boat transom T during jet pump operation. 
     One of the primary advantages of some examples of the invention is the improvement in performance provided by the ability to dynamically adjust the vertical orientation of marine jet drive J and the angular inclination of scoop  38 . This provides the operator with the ability to make a change to the vertical orientation of marine jet drive J, or the angle of scoop element  38 , or both, and to achieve substantially immediate feedback based upon the changes. This permits the user to place marine jet drive J at an optimal orientation depending on the particular operating conditions, including the speed of boat B and the load within the boat. 
     The tubular support casing C containing the drive shaft S extending beyond the transom T forms the effectively sole support to the jet pump P. Trim cylinder  34  typically provides only a small portion of the vertical support to prevent the downward pivotal movement of jet pump P when at rest. Trim cylinder  34  may act to prevent the upward inclination of jet pump J when moving at higher speeds. The chamber  14  is thus effectively supported by the tubular support casing C in the water body W astern of the transom T with both the chamber inlet  16  and outlet  18  of the jet pump disposed behind the transom. 
     In an aspect, this disclosure describes an improvement in a marine jet drive for a boat. Among others, the improvement in the marine jet drive eliminates the need for an opening in the hull for water intake to the marine jet assembly. In an embodiment, the marine jet drive has a jet pump that includes a chamber with an inlet for providing water to the marine jet drive. The chamber inlet provides the sole source of water for the jet pump, eliminating the need for water intake through the boat hull and for passing the water back to the marine jet drive rotating blades. 
     Another improvement in marine jet drives disclosed herein is the selection of the blades for an axial pump that turn at the same speed as the power source connected drive shaft thereby eliminating the need for a transmission to convert the drive shaft speed into a rotational speed compatible with the blade design. 
     This disclosure also illustrates that the marine jet drive may be equipped with a dynamic positioning apparatus that provides for adjusting the vertical orientation of the marine jet drive so that the jet pump chamber inlet can be movably positioned relative to the water body, allowing for control of the water intake flow depending upon changing boat trim during startup and speed operation. Other improvements and enhancements will be discussed below with regard to particular components or features. 
     Examples of boats B with marine jet drives J have another advantage over conventional marine jet drives. During turning, especially hard turns, the operator can orient marine jet drive J to ensure that it remains in a properly submerged state relative to water body W. This is not possible with conventional marine jet drive mounted beneath the hull of the boat. 
     Further, the buoyancy of the hull is minimally affected by water within the jet pump P as the entire marine jet drive J is maintained outside the floating hull of boats B. This is in contrast with conventional jet drive boats which can see an increase in the weight of the boat by 10% or more because of the water drawn into the jet drive apparatus within the hull of the boat. 
     While the present invention is disclosed by reference to the preferred embodiments and examples detailed above, it is to be understood that these examples are intended in an illustrative rather than in a limiting sense. It is contemplated that modifications and combinations will occur to those skilled in the art, which modifications and combinations will be within the spirit of the invention and the scope of the following claims.