Patent Publication Number: US-6033272-A

Title: Marine jet drive system with debris cleanout feature

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a jet drive system for marine applications and, more particularly, to a marine jet drive system having a novel arrangement for removing debris from the jet drive inlet opening without requiring the operator of the boat in which the system is installed to exit the boat. 
     2. Description of the Related Art 
     Jet drive systems of known design for use in marine applications such as jet boats or the like, typically include a power plant comprising an internal combustion engine connected by a drive train to a housed impeller which creates a high pressure stream of water to propel the boat. The inlet to the impeller is usually an opening in the underside of the boat communicating with the impeller. The impeller creates a high pressure water stream discharging to the rear of the boat through a nozzle. Typically, the nozzle is pivotable to allow for steering of the boat. Also, it is known to provide a reverse gate which is selectively operable to cover the exit nozzle and redirect the water stream forwardly of the boat. Thus, the boat can be controlled to move both forward and backward. 
     In heretofore known marine jet propulsion systems, the drive train of the system has been designed to turn the impeller only in one direction. Moreover, debris such as weeds or other floating objects are often known to enter the impeller housing through the inlet opening and cause clogging of the impeller or inlet opening which is unacceptable to the performance of the boat. When such clogging occurs, the operator of the boat has no means from inside the boat for removing the debris. Accordingly, the boat must be physically removed from the water to expose the jet inlet, or in some cases the operator has the alternative of entering the water and manually removing the debris. 
     Accordingly, it is desirable to provide a jet drive system for a boat or the like wherein clogging of the impeller or water inlet opening of the drive unit can be alleviated by the boat operator while the operator is simply seated at the controls of the boat. It is further desirable to provide such a system which is readily manufacturable and reliable in use. Still further, it is desirable to provide such a system which can be produced cost effectively and which has perceived value to the ultimate consumer. 
     SUMMARY OF THE INVENTION 
     The present invention improves over the prior art by providing a marine jet propulsion system for a boat or the like comprising a power plant for rotating a drive shaft. A gear system is connected to the drive shaft and is configured to engage and rotate an impeller shaft. An impeller mounted to the impeller shaft is enclosed within a housing having a water inlet opening and a jet stream exit opening. The gear system includes a pinion gear connected to the drive shaft and engaging a pair or opposed ring gears, the ring gears being thus rotatable by the pinion gear in opposite directions. A clutch system is provided for selectively causing the impeller shaft to alternatively be engaged by one or the other of the ring gears and thereby selectively rotating the impeller in opposite directions. By this arrangement, rotation of the impeller in a first direction draws water through the housing in normal fashion to provide thrust at the exit opening, while rotation of the impeller in the opposite direction reverses the flow through the housing, causing debris to be flushed out of the impeller or inlet opening. A simple control system allows the boat operator to perform the flushing process while occupying the control station of the boat. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other novel features and advantages of the invention will be better understood upon a reading of the following detailed description taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a right rear side perspective view of a prior art marine jet propulsion device shown partially broken away. 
     FIG. 2 is a partial side schematic view of a marine jet propulsion device constructed in accordance with the preferred embodiment of the invention; and 
     FIG. 3 is a schematic view of a control system for the jet propulsion device illustrated in FIG. 2. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and initially to FIG. 1, a prior art marine jet propulsion device is designated generally by the reference numeral 10 and includes as a principal assembly a power plant 12 which is characteristically a multi-cylinder internal combustion engine of known design. The power plant 12 drives a drive shaft 14 to which a pinion gear 16 is fixed. The pinion gear 16 in turn engages a ring gear 18 connected to an impeller shaft 22. Fixed to the impeller shaft 22 is an impeller 24 which is journaled for rotation within a housing 26. The housing 26 is provided at its rearward end with a pivotable steering nozzle 28 and with a reverse gate 30 which may be operated by a suitable cable 32. The forward end of the housing 26 is provided with an inlet opening 34 which extends through the underside hull of a boat (not shown). In operation, water is drawn through the inlet opening 34 and is discharged in a high pressure jet stream through the nozzle 28 by the rotating impeller 24. The nozzle 28 may be pivoted by the boat operator to change the direction of the jet stream and thereby steer the boat. Also, the reverse gate may be actuated to reverse the flow direction and consequent thrust of the jet stream and thus shift the boat into reverse. It is noted that in the prior art system only one ring gear and pinion set is provided and, therefore, the impeller is driven in one direction only. 
     Turning now to FIGS. 2 and 3, a marine jet propulsion system constructed in accordance with the preferred embodiment of the invention is designated generally by the reference numeral 40. The system 40 includes a power plant 42 in the form of an internal combustion engine which drives a drive shaft 44 having a pinion gear 46 fixed to an end thereof The pinion gear 46 in turn engages a pair of ring gears 48 and 50 which are configured to spin freely on a splined impeller shaft 52. A shifter system includes a clutch 54 which is selectively slidable axially of the splined shaft 52 and has suitable lugs 56 for alternatively engaging lugs 58 and 60 of the gears 48 and 50, respectively. An impeller 62 is fixedly mounted to impeller shaft 64 which is connected to shaft 52 by a torque coupling 66. 
     By virtue of the gear drive arrangement of the system 40, the gears 48 and 50 rotate in opposite directions when driven by the pinion 46. Thus, the clutch 54 may selectively be moved along the splined shaft 52 to alternatively engage one or the other of the gears 48 or 50, causing the shaft 52 and thus the impeller 62 to selectively turn in opposite directions. One advantage of the system 40 is that the impeller 62 may be driven in a normal thrust direction whereby water is drawn into an impeller housing 70 through a conventional inlet opening 72 and is forced as a high pressure jet stream out of an exit opening 74 of the housing 70 by inter-engagement, for example, of the gear 50 and clutch 54. However, when it is desired to clear the inlet opening 72 or impeller 62 of debris, the gear 48 may be engaged by the clutch 54, causing the impeller 62 to counter-rotate, drawing water into the housing 70 through the normal exit opening 74 and forcing it out the inlet opening 72. Thus, the boat operator need not exit the boat to clear a clogging situation, but can simply operate the reverse flushing function from within the boat. 
     FIG. 3 shows one possible control mechanism 80 for the system 40. In the illustrated example, the mechanism 80 includes a clutch actuator 82 which is moved axially of the shaft 52 by a bellcrank 84. The bellcrank 84 is, in turn, operated by engaging a shaft 86 with a manually operable push rod 88. The shaft 86 is provided at one end with a cam follower 90. A cam plate 92 is configured to be movable from right to left, as viewed in FIG. 3, and includes a cam surface 94 which extends generally upwardly and to the right as well as a cam surface 96 which extends generally upwardly and to the left. The plate 92 is moved by a cable 98 and associated manual control lever assembly 100. The cam plate 92 also includes a first slot 102 disposed generally vertical and leading to a second generally horizontal slot 104. The push rod 88 includes a link portion 106 having a generally vertical slot 108 which captures the cam follower 90. 
     In operation of the control mechanism 80, and as viewed in FIG. 3, the system 40 is in a neutral condition, as illustrated, with the cam follower 90 aligned with the slot 108 of the cam plate 92. In such a condition, the clutch 54 is centered between and out of engagement with both gears 48 and 50. Thus, the impeller 62 is stationary and the boat is in neutral. In a manner well-known in the art the control lever assembly 100 may be configured to thus idle or rev the boat engine as desired without turning the impeller 62. When it is desired to engage the impeller 62 and move the boat forward, the cam plate 92 is moved to the right, causing the cam surface 96 to engage the cam follower 90 and lift the shaft 86. This action, in turn, rotates the bellcrank 84 counterclockwise, causing the clutch 54 to engage drive gear 50, and thereby rotate the impeller 62 in the normal forward thrust direction. Alternatively, when the cam plate 92 is moved to the left, again as viewed in FIG. 3, the cam surface 94 lifts the cam follower 90 and shaft 86, causing the clutch to engage drive gear 50 and apply normal torque to the impeller 62. However, in this mode the cam plate 92 is connected by a cable 112 to a reverse gate 114 at the exit of the impeller housing 70. The reverse gate 114 is suitably configured to actuate in this mode to thereby reverse the thrust direction of the water jet exiting the housing 70. The boat is, therefore, operable in a reverse direction of movement. It is noted that when the cam plate 92 is moved either to the right or left, the push rod 88 remains stationary as the cam follower 90 moves within the slot 108. 
     It can be seen from FIG. 3 that when it is desired to reverse direction of the impeller 62 and thus flush the impeller 62 and inlet opening 72 with a reverse stream of water, the push rod 88 is moved downwardly which forces the cam follower down through slot 102 and into slot 104 of the cam plate 92. This action rotates the bellcrank 84 clockwise, causing the clutch to engage gear 48. In this condition, either forward or reverse actuation of the control lever assembly 100 will cause water to flow reversely through the impeller housing 70, thereby flushing the inlet opening 72 of any debris clogged therein. A suitable water pump 110, as illustrated in FIG. 2, may be added to the engine 42 to cool the engine 42 during reverse impeller 62 operation. 
     It can now be appreciated that the system 40 of the present invention offers considerable advantages over prior art marine jet propulsion systems, particularly in situations whereby a jet boat is operated in water conditions laden with debris. With the present system 40, the boat operator can potentially clear obstructions in the impeller housing or inlet without leaving the driver&#39;s seat of the boat. Thus, the boat need not be removed from the water to clear a clog. The system 40 also offers the advantage of allowing the boat propulsion system to have a true neutral, unlike prior art designs wherein the impeller is always turning when the engine is running. Although the present invention has been illustrated with one form of control mechanism 80, it will be appreciated that numerous modifications may be made to this mechanism 80 and still allow the gear system to function acceptably. For example, suitable cables may be used to replace the bellcrank 64 and associated parts. Likewise, a cable arrangement may replace the push rod 88 and related linkage. 
     While the present invention has been described in connection with preferred embodiments thereof, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the true spirit and scope of the present invention. Accordingly, it is intended by the appended claims to cover all such changes and modifications as come within the spirit and scope of the invention.