Patent Publication Number: US-6213041-B1

Title: Speed sensor for personal watercraft

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a sensor device for use with a personal watercraft. More particularly, the present invention relates to a speed monitoring system adapted to be mounted to a ride plate of a personal watercraft. 
     2. Description of Related Art 
     Personal watercraft have become very popular in recent years. An enthusiasm for competition has grown with this popularity, and as a result personal watercraft have become increasingly fast. Many personal watercraft today are capable of speeds well in excess of 60 miles per hour. This type of watercraft is sporting in nature; it turns swiftly, is easily maneuverable, and accelerates quickly. Personal watercraft today commonly carry one rider and one or two passengers. 
     Personal watercraft often include some types of instrumentation to optimize the performance of the watercraft, as well as to monitor various operational characteristics of the watercraft&#39;s performance. In this regard, the personal watercraft usually includes a speedometer to allow the operator to monitor the speed of the watercraft. 
     Most speed indicators require a component of the indicator to be mounted on the underside of the hull. In this position, the component lies within the water and generates a signal indicative of the watercraft&#39;s speed. The hull of a personal watercraft, however, does not have large areas on which to mount conventional speed sensors. Most of the practical surface on the underside of the hull is occupied by a jet pump unit that is positioned within a tunnel formed on the underside of the watercraft hull. 
     As a result of the limited space on the underside of the hull, speed indicators are usually mounted proximate to the stern of the watercraft, near a nozzle section of the jet pump unit. This location of the speed indicator, however, often results in an overly complicated layout of the watercraft components, including the speed sensor, steering nozzle and associated level and cable arrangements. In addition, the speed indicator extends below the planing surface of the lower hull at this location and consequently is susceptible to damage. Moreover, the speed indicator is also visible from the rear of the watercraft when mounted at this location, which lessens the attractive, streamlined appearance of the watercraft. In addition, the speed sensor will often give false readings resulting from the disturbances the watercraft hull causes as it travels through the water. 
     SUMMARY OF THE INVENTION 
     The present invention involves in part the recognition that several problems arise in connection with employing a speed sensor with a personal watercraft. One such problem involves the fact that the watercraft disturbs the water in which it travels, which can result in false readings from a speed sensor attached to the watercraft. Another problem involves the fact that, as the watercraft maneuvers, much of the bottom surface of the watercraft can often lift out of the water, which can similarly affect speed readings from the attached speed sensor. 
     The present invention provides a speed measuring system whereby the speed of the watercraft can be accurately measured during watercraft operation, even when the watercraft is travelling at high speeds and/or undergoing violent maneuvers or sharp turns. 
     Accordingly, one aspect of the present invention involves a personal watercraft comprising a hull having a longitudinal axis. A generally longitudinally-extending elongated seat is positioned on an aft portion of the hull. An engine compartment is defined within the hull and an engine is mounted within the engine compartment. A tunnel is defined within a lower aft portion of the hull. A propulsion unit is preferably powered by the engine and mounted within the tunnel. A plate covers at least a portion of the tunnel proximate the propulsion unit and has a generally longitudinally-extending channel defined along at least a portion thereof. A sensor is mounted to the plate and has a moveable element that extends into the channel. A display is positioned proximate the straddle seat and communicates with the sensor. 
     Another aspect of the present invention involves a ride plate assembly for a personal watercraft. The ride plate assembly comprises a sensor and a plate. The sensor generally comprises a moveable element and a housing supporting at least a portion of the moveable element. The plate comprises a longitudinally-extending channel with the channel extending along at least a portion of the length of the plate. The housing is connected to an aft portion of the plate with at least a portion of the rotatable element being positioned in line with the channel. 
     A further aspect of the present invention involves a personal watercraft comprising a hull having a longitudinal axis. A generally longitudinally-extending elongated seat is positioned on an aft portion of the hull. An engine compartment is defined within the hull with an engine mounted within the engine compartment. A tunnel is defined within a lower aft portion of the hull and contains a propulsion unit powered by the engine. A ride plate assembly covers at least a portion of the tunnel proximate the propulsion unit and generally comprises a plate and a sensor apparatus. The sensor apparatus comprises a moveable element and a display in communication with the movable element. The display is positioned on the hull so as to be easily viewed by an operator. The ride plate assembly also comprises a means for channeling a flow of water into contact with at least a portion of the movable element of the sensor apparatus. 
     Further aspects, features, and advantages of the present invention will become apparent from the detailed description of the preferred embodiments which follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features of the invention will now be described with reference to the drawings of preferred embodiments of the present watercraft. The illustrated embodiments of the watercraft are intended to illustrate, but not to limit the invention. The drawings contain the following figures: 
     FIG. 1 is partial cross-sectional view of a personal watercraft with a speed monitoring system configured in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a sectional side view of the personal watercraft of FIG. 1, with various components of the watercraft illustrated in phantom; 
     FIG. 3 is a cross-sectional view of the watercraft of FIG. 2 taken along line  3 — 3 ; 
     FIG. 4 is a partial sectional side view of the personal watercraft of FIG. 1, with various components of the watercraft illustrated in phantom; 
     FIG. 5 is a partial top plan view of the personal watercraft of FIG. 1, with various components of the watercraft illustrated in phantom; 
     FIG. 6 is a partial cross-sectional view of a personal watercraft with a speed monitoring system configured in accordance with another embodiment of the present invention; 
     FIG. 7 is a partial sectional side view of the personal watercraft of FIG. 6, with various components of the watercraft illustrated in phantom; 
     FIG. 8 is a partial cross-sectional view of the personal watercraft of FIG. 7 taken along line  8 — 8 ; 
     FIG. 9 is a partial top plan view of the personal watercraft of FIG. 6, with various components of the watercraft illustrated in phantom; and 
     FIG. 10 is a partial cross-sectional view of a personal watercraft with a speed monitoring system configured in accordance with another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     With initial references to FIGS. 1 and 2, a portion of a small watercraft, indicated generally by the reference numeral  100 , is partially illustrated in cross-section. The watercraft  100  includes an arrangement of an engine  102  and a speed monitoring system  200  mounted within a ride plate  140  of the watercraft  100  in accordance with a preferred embodiment of the present invention. 
     Although the present invention is illustrated and described with reference to the illustrated embodiments, various other engine types and configurations may also be used with the present invention. Moreover, it is understood that the speed monitoring system  200  can be used with other types of watercraft as well, for example, but without limitation, jet boats and the like. 
     The following describes the illustrated watercraft in reference to a coordinate system in order to ease the description of the watercraft. A longitudinal axis extends from bow to stem and a lateral axis from port side to starboard side normal to the longitudinal axis. In addition, relative heights are expressed in reference to the undersurface of the watercraft. And in FIG. 2, a label “F R ” is used to denote the direction the watercraft travels during normal forward operation. 
     Before describing the speed monitoring system  200  in the watercraft  100 , an exemplary personal watercraft  100  will first be described in general detail to assist the reader&#39;s understanding of the environment of use. The watercraft  100  has a hull, indicated generally by reference numeral  104 . The hull  104  can be made of any suitable material; however, a presently preferred construction utilizes molded fiberglass reinforced resin. The hull  104  generally has a lower hull section  106  and an upper deck section  108 . A bond flange or gunnel  112  may connect the lower hull section  106  to the upper deck section  108 . Of course, any other suitable means may be used to interconnect the lower hull section  106  and the upper deck section  108 . Additionally, the lower hull section  106  and the upper deck section  108  may be integrally formed. 
     As viewed in the direction from the bow to the stem of the watercraft, the upper deck section  108  includes a control mast  146  supporting a handlebar assembly  148  and a rider&#39;s area  109 . The handlebar  148  controls the steering of the watercraft  100  in a conventional manner. The handlebar assembly also carries a variety of controls of the watercraft  100 , such as, for example, a throttle control, a start switch and a lanyard switch. 
     The rider&#39;s area  109  lies behind the control mast  146  and includes a seat assembly  150 . In the illustrated embodiment, the seat assembly  150  has a longitudinally extending straddle-type seat which may be straddled by an operator and by at least one or two passengers. The seat assembly  150 , at least in principal part, is formed by a seat cushion  152  supported by a raised pedestal  154 . The raised pedestal  154  forms a portion of the upper deck section  108 , and has an elongated shape that extends longitudinally along the center of the watercraft  100 . The seat cushion  152  desirably is removably attached to a top surface of the raised pedestal  154  by one or more latching mechanisms (not shown) and covers the entire upper end of the pedestal  154  for rider and passenger comfort. 
     An engine access opening (not shown) is located in the upper surface of the upper deck section  108 . The access opening opens into an engine compartment  116  formed within the hull  104 . An engine access cover (not shown) normally covers and seals closed the engine compartment  116  in a watertight manner. When the engine access cover is removed, the engine compartment  116  of the hull  104  is accessible through the access opening. 
     The upper deck section  108  of the hull  104  advantageously includes a pair of level planes (not shown) positioned on opposite sides of the aft end of the upper deck section  108 . The level planes define a pair of foot areas that extend generally longitudinally and parallel to the sides of the pedestal  154 . In this position, the operator and any passengers sitting on the seat assembly  150  can place their feet on the foot areas during normal operation of the personal watercraft  100 . A non-slip (e.g., rubber) mat desirably covers the foot areas to provide increased grip and traction for the operator and passengers. 
     The hull  104  also includes one or more bulkheads  114  which may be used to reinforce the hull internally and which also may serve to define, in part, the engine compartment  116  and the propulsion compartment  118 . The engine  102  is mounted within the engine compartment  116  in any suitable manner. For instance, a set of resilient engine mounts (not shown) may be used to connect the engine  102  to a set of stringers (not shown). The engine is desirably mounted in a central transverse position. The engine  102  may be of any known configuration. For example, the engine  102  may be a two-stroke, four-stroke or rotary type of engine. Additionally, the engine  102  may comprise any number of cylinders. The illustrated engine is a four-stroke engine having four cylinders. The illustrated engine type, however, is merely exemplary. 
     Air intakes and air ducts (not shown) in the upper deck section  108  of the watercraft  100  typically allow atmospheric air to be used for cooling and combustion to enter the engine compartment  116 . Except for the air ducts, the engine compartment  116  is normally substantially sealed so as to enclose the engine  102  of the watercraft  100  from the body of water in which the watercraft  100  is operated. 
     The lower hull section  106  is designed such that the watercraft  100  planes or rides on a minimum surface area of the aft end of the lower hull section  106  in order to optimize the speed and handling of the watercraft  100  when up on plane. For this purpose, as best seen in FIG. 3, the lower hull section  106  generally has a V-shaped configuration formed by a pair of inclined sections that extend outwardly from the keel line  168  to outer chimes  170  at a dead rise angle. The inclined sections extend longitudinally from the bow toward the transom  174  of the lower hull section  106  and extend outwardly to side walls  172  of the lower hull section  106 . The side walls  172  are generally flat and straight near the stem of the lower hull section  106  and smoothly blend towards the longitudinal center of the watercraft  100  at the bow. The lines of intersection between the inclined section and the corresponding side wall  172  form the outer chines  170  of the lower hull section  106 . The lower hull section  106  can also include additional chines between the keel line  168  and the outer chines  170  for improved handling, as known in the art. 
     Toward the transom of the watercraft  100 , the inclined sections of the lower hull section  106  extend outwardly from a recessed tunnel  132  that extends upward towards the upper deck section  108 . The tunnel  132  has a generally parallelepiped shape and opens through a transom  174  of the watercraft  100 . 
     In the illustrated embodiment, a jet pump unit  126  propels the watercraft  100 . The jet pump unit  126  is mounted within the tunnel  132 , formed on the underside of the lower hull section  106 , by a plurality of bolts (not shown). An inlet opening  134  formed in the bottom of the hull  104  opens into a gullet  138  which leads to an impeller housing of the jet pump unit  126 . 
     A steering nozzle  143  is supported at the downstream end of the discharge nozzle  142  by a pair of vertically extending pivot pins (not shown). In an exemplary embodiment, the steering nozzle  143  has an integral level on one side that is coupled to the handlebar assembly  148  through, for example, a bowden-wire actuator, as known in the art. In this manner, the operator of the watercraft  100  can move the steering nozzle  143  to effect directional changes of the watercraft  100 . 
     A ride plate  140  covers a portion of the tunnel  132  behind the inlet opening  134  to enclose the jet pump unit  126  within the tunnel  132 . As best seen in FIG. 1, the ride plate  140  is comprised of a center plate section  144  and opposing side plate sections  145  which extend outward from the center plate section  144 . A bulge or bead  128  is secured within a cutaway section  170  of the ride plate  140 . The bead  128  is desirably fastened to the ride plate  140  by welding or other fastening means well known in the art. Bolts  120  secure the ride plate  140  to the lower hull  106  with the side plate sections  145  of the ride plate  140  blending with the rear inclined sections of the lower hull  106 . In this manner, the lower opening of the tunnel  132  is closed to provide a planing surface for the watercraft  100 . A pump chamber  141  then is defined within the tunnel section covered by the ride plate  140 . 
     An impeller shaft  124  supports the impeller  128  within the impeller housing  130 . The aft end of the impeller shaft  124  is suitably supported and journalled within the compression chamber  136  of the housing  130  in a known manner. The impeller shaft  124  extends in a forward direction through a bulkhead  114 . A protective casing surrounds a portion of the impeller shaft  124  that lies forward of the intake gullet  138 . 
     The engine  102  powers the impeller shaft  124  about an impeller axis  169 . The engine  102  is positioned within the engine compartment  116  and is mounted primarily beneath the rider&#39;s area  109 . The engine is mounted in approximately the centerline of the watercraft  100 . 
     A fuel supply system delivers fuel to the engine  102  in a manner known in the art. The fuel supply system includes a fuel tank  176  located in front of the engine  102 . Although not illustrated, at least one pump desirably delivers fuel from the fuel tank  176  to the engine  102  through one or more fuel lines. 
     The engine  102  typically draws air from the engine compartment  116  through an engine air intake system (not shown). Although not illustrated, the engine air intake system typically comprises an engine air intake which draws air from the engine compartment  116  and supplies this air to an air intake manifold and carburetor, which supply a fuel/air charge to a plurality of engine cylinders in a known manner. Of course, other arrangements, such as direct or indirect fuel injection, could be used to provide a fuel charge to the engine  102 . 
     The engine exhaust system  180  typically comprises an exhaust manifold which transfers exhaust gases exiting the combustion chamber to an engine exhaust pipe  180 . The exhaust manifold thus generally comprises a merge chamber and a plurality of exhaust runner passages as known in the art. The engine exhaust pipe transfers exhaust gases to a watertrap. The watertrap is a well known device that allows the passage of exhaust gases, but contains baffles which prevent water from passing back through the engine exhaust pipe into the engine  102 . In the present embodiment, the watertrap is located behind the engine  102 . The watertrap transfers exhaust gases to a watercraft exhaust pipe. The watercraft exhaust pipe discharges the exhaust gases to the pump chamber  141  and the atmosphere. Desirably, at least one section of the watercraft exhaust pipe is positioned higher than the watertrap and the pump chamber  141 , such that the passage of water W through the atmospheric exhaust pipe into the watertrap is inhibited. 
     As best seen in FIG. 3, the tunnel  132  in general is formed by a ceiling  156 , opposing side walls  158 , the ride plate  140  and a front plate  160 . A water pipe  164 , which forms a portion of the impeller housing  130 , is secured to the front plate  160  by fasteners  164  or other means well known in the art. 
     As previously noted, the engine  102  desirably is an internal combustion engine of a known four-stroke variety. Because the engine is conventional, the internal details of the engine are not believed necessary for an understanding of the present speed monitoring system. 
     With reference to FIGS. 1-5, the speed monitoring system  200  comprises a speed sensor  110  at least partially disposed within a channel  122  formed in a lower surface of the ride plate  140 . While the disclosed channel extends longitudinally along a substantial portion of the ride plate  140 , it could also extend the entire length along the ride plate, with no loss of utility. In addition, while the disclosed channel  122  varies in depth along its length, if desired the channel  122  could be of a constant depth along its entire length, or could be enclosed along some or all of its length. 
     The speed sensor  110  comprises a sensor body  182  which is positioned over the bead  128  of the ride plate  140 . The sensor body  182  is secured to the ride plate by fasteners  184  or other means well known in the art. A paddle wheel or rotator  166  is secured to the sensor body  182  by a shaft, which allows the rotator  166  to rotate freely. 
     The rotator  166  includes a plurality of blades  167  which extend from the hub of the rotator  166 . Desirably, the hub rotates about an axis transverse to the forward motion F R  of the watercraft  100 , although other orientations could be used, if desired. Each blade is sized such that the tip of the blade  167  extends through an opening  176  formed in the bead  128 . In the disclosed embodiment, the blade does not extend beyond the channel  122 , however, if desired the blade could extend beyond the channel  122  and/or below the bottom surface of the ride plate  140 . Each blade  167  is configured principally for rotation in a water flow moving along the longitudinal axis of the watercraft  100 . 
     The speed sensor  110  also includes a rotation detector (not shown) that is used to determine the rotational speed of the rotator  166 . By way of example, and not by limitation, the rotational detector could include a “hall-effect” transducer that cooperates with the blades  167  of the rotator  166 , such as disclosed in U.S. Pat. No. 5,699,749 to Yamada, which is incorporated by reference herein. For this purpose, the blades  167  of the rotator would desirably be made of a magnetic material and are alternately polarized. The paddle wheel would thus include an even number of blades. When the rotator  166  is rotated, the transducer produces a signal which can be used to determine the speed of the watercraft. 
     When the watercraft is operating in the forward direction F R , water W will flow past a lower hull portion  139  and the ride plate  140 . This water W tends to enter the channel  122 , and travels longitudinally along the channel  122  and past the speed sensor  110 . Because the blades  167  of the rotator  166  extend into the channel  122 , this motion of the water W will interact with the blades  167 , spinning the rotator  166 . 
     Because the channel  122  is positioned on the underside of the ride plate  140 , desirably on the keel line  168  of the watercraft  100 , the channel  122  will typically be in contact with and/or submerged under water W. Consequently, during forward operation of the watercraft  100 , water W will continually pass through the channel  122 , even when the watercraft  100  undergoes violent maneuvers and/or high-speed turns. In addition, the length of the channel improves the accuracy of the speed sensor  110  by isolating the sensor  110  from disturbances in the water W caused by the passage of the watercraft  100 . Thus, the disclosed speed monitoring system  200  provides consistently accurate speed data to the operator of the watercraft during all aspects of watercraft operation. 
     FIGS. 6-9 illustrate another embodiment of a speed monitoring system  200  within a small watercraft  100  in accordance with a preferred embodiment of the present invention. The principal differences between the embodiment of FIGS. 1-5 and the embodiment of FIGS. 6-9 lie with the positioning and arrangement of the speed monitoring system on the ride plate  140  of the watercraft hull  104 . Therefore, for ease of description, similar features are ascribed the same reference numerals used for corresponding elements from the embodiments of FIGS. 1-5. Unless otherwise indicated, the above description of similar components should be understood as applying equally to the following embodiment. 
     As with the first embodiment, while the watercraft is operating in the forward direction F R , water W will desirably pass through the channel  122 . In the embodiment shown in FIGS. 6-9, the speed monitoring system  200  comprises a speed sensor  110  at least partially disposed within a channel  122 . However, in this embodiment, the center plate section  144  of the ride plate  140  is wider than that of the previously disclosed embodiment. In addition, in this embodiment, a liner plate  192  is secured to the underside of the ride plate  140  by fasteners  186  or other means well known in the art. 
     The liner plate  192  comprises a rear plate  188  and a front plate  190 . As previously noted, the rear plate is secured to the underside of the ride plate  140  by fasteners  186 . Similarly, the front plate  190  is secured to the underside of the ride plate  140  by fasteners  186 , at a location forward of the rear plate  188 . A portion of the channel  122  is formed in the underside of each plate  188 ,  190 . As can best be seen from FIGS. 7 and 9, the front and rear plates  190 ,  188  are desirably in contact with each other, such that they form the channel  122  which extends longitudinally along the underside of the skid plate  140 . 
     The speed sensor  110  comprises a sensor body  182 , and a rotator  166 , with a portion of the rotator  166  extending into the portion of the channel  122  formed in the rear plate  188 . The sensor body  182  is secured to flanges  194  of the liner plate  192  by fasteners  184 . As with the embodiment of FIGS. 1-5, the rotator  166  includes a plurality of blades  167  which extend from the hub of the rotator  166 . Each blade is sized such that the tip of the blade  167  extends into the channel  122 . Each blade  167  is configured principally for rotation in a water flow moving along the longitudinal axis of the watercraft  100 . The speed sensor  110  also includes a rotation detector (not shown) that is used to determine the rotational speed of the rotator  166 , such as the previously-described “hall-effect” transducer. 
     This embodiment allows the speed monitoring system to be utilized with watercraft having little or no clearance above the ride plate  140 . By extending the speed sensor through the ride plate  140 , and securing the speed sensor  110  to the liner plate  192 , the present embodiment eliminates the need for substantial clearance between the ride plate  140  and the water pipe  164 . In addition, the incorporation of the liner plate  192  assists the ride plate  140  in supporting the weight of the watercraft  100  when up on plane. 
     As with the previously-described embodiment, when the watercraft is in operation in the forward direction F R , water W will flow through the channel  122  and will activate the speed sensor  110 . Consequently, during forward operation of the watercraft  100 , water W will continually pass through the channel  122 , even when the watercraft  100  undergoes violent maneuvers and/or high-speed turns. 
     FIG. 10 illustrates another embodiment of a speed monitoring system  200  in a small watercraft  100  in accordance with a preferred embodiment of the present invention. The principal differences between the present embodiment and the embodiment of FIGS. 1-5 lie with the positioning and arrangement of the speed monitoring system on the ride plate  140  of the watercraft hull  104 . Therefore, for ease of description, similar features are ascribed the same reference numerals used for corresponding elements from the embodiments of FIGS. 1-5. Unless otherwise indicated, the above description of similar components should be understood as applying equally to the following embodiment. 
     As with the first embodiment, while the watercraft is operating in the forward direction F R , water W will desirably pass through the channel  122 . In the embodiment shown in FIG. 10, the speed monitoring system  200  comprises a speed sensor  110  at least partially disposed within a channel  122  formed in a lower surface of the ride plate  140  of the watercraft  100 . In this embodiment, the center plate section  144  of the ride plate  140  is thicker than that of the embodiment of FIGS. 1-5. This increased thickness of the center plate section  144  permits the channel  122  to be formed in the ride plate  140  without significantly weakening the ability of the ride plate to support the planing watercraft. The speed sensor  110  fits into a recess formed in the upper surface of the ride plate  140 . 
     By forming the channel  122  within the ride plate  140  in the disclosed manner, the present embodiment significantly reduces the complexity of the present speed monitoring system without sacrificing the strength of the ride plate  140 . In a similar manner, if desired, the ride plate  140  of FIGS. 1-5 could similarly be strengthened by increasing the thickness of the ride plate  140 , or by forming a channel  122  in a projection which extends downward from the ride plate  140 . 
     As with the previously described embodiments, the positioning and arrangement of the disclosed speed monitoring system provides the watercraft operator with accurate speed data during high speed operation of the watercraft and during violent maneuvers and/or high-speed turns. 
     Although this invention has been described in terms of certain embodiments, other embodiments apparent to those of ordinary skill in the art also are within the scope of this invention. Thus, various changes and modifications may be made without departing from the spirit and scope of the invention. For example, various combinations of the preferred embodiments are possible. Accordingly, the scope of the invention is intended to be defined only by the claims that follow.