Patent Publication Number: US-2005124235-A1

Title: Reverse system for water-jet propulsion personal watercraft

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a reverse system configured to move a water-jet propulsion personal watercraft rearward.  
      2. Description of the Related Art  
      In recent years, water-jet propulsion personal watercraft have been widely used in leisure, sport, rescue activities, and the like. The personal watercraft is configured to accommodate an engine within a body formed by a hull and a deck covering the hull from above. The engine is configured to drive a water jet pump, which pressurizes and accelerates water sucked from a water intake generally provided on a hull bottom surface and ejects it rearward from an outlet port. Thereby, the personal watercraft is propelled.  
      In water-jet propulsion personal watercraft, a steering nozzle is provided behind the water jet pump to be pivotable either to the right or to the left, and connected to a bar-type steering handle through a cable. By operating the steering handle, the steering nozzle is pivotable to the right or to the left so that a flow direction of water ejected from the water jet pump can be changed.  
      Japanese Patent Nos. 2756434 and 3358718 disclose a personal watercraft equipped with a reverse system configured to move the watercraft rearward. In this personal watercraft, a reverse bucket is provided behind the water jet pump to cover the steering nozzle. The reverse bucket is connected to a reverse lever mounted to a deck through a cable. By operating the reverse lever, the reverse bucket is vertically pivotable within a predetermined range.  
      To move the watercraft forward, the reverse bucket is held at an upper position, and the water ejected from the steering nozzle is directed substantially rearward. As the resulting reaction, the watercraft is propelled forward. On the other hand, to move the watercraft rearward, the reverse bucket is held at a lower position, and the water ejected from the steering nozzle collides with an inner wall of the reverse bucket and thereby directed substantially forward. As the resulting reaction, the watercraft is propelled rearward.  
      In the above described reverse system, it is necessary to temporarily hold the reverse bucket at the upper position or the lower position. Specifically, when the watercraft is traveling forward, it is necessary to hold the reverse bucket at the upper position so as not to interfere with the water ejected rearward from the steering nozzle, while when the watercraft is traveling rearward, it is necessary to hold the reverse bucket at the lower position to cause the water ejected from the steering nozzle to collide with the inner wall of the reverse bucket and to be thereby directed substantially forward.  
      In order to reliably hold the reverse bucket at the upper or lower position, the reverse system is typically equipped with a stopper device. The stopper device is constructed by assembling numerous parts, and has a relatively intricate structure. Such a stopper device is expensive because of the numerous parts, and may make it difficult to hold the reverse bucket at the upper or lower position with high positioning precision.  
     SUMMARY OF THE INVENTION  
      The present invention addresses the above described condition, and an object of the present invention is to provide a reverse system capable of holding a reverse bucket with a relatively simple structure and with high positioning precision.  
      According to the present invention, there is provided a reverse system of a water-jet propulsion personal watercraft, comprising a water jet pump configured to propel the watercraft; a reverse bucket disposed rearward of the water jet pump to be vertically pivotable and configured to receive water ejected rearward from the water jet pump and to direct the water substantially forward; and a pump cover configured to cover the water jet pump from below, wherein the pump cover includes a restricting portion, and the reverse bucket includes a stopper, the restricting portion and the stopper being configured to contact each other to restrict upward pivot movement or downward pivot movement of the reverse bucket within a predetermined range.  
      In this construction, the stopper of the reverse bucket and the restricting portion of the pump cover can restrict the upward pivot movement or the downward pivot movement of the reverse bucket within a predetermined range. Such a simple construction can improve positioning precision of the reverse bucket.  
      The pump cover may further include a mounting portion configured to pivotally mount the reverse bucket. By reducing the number of parts, a simple construction is achieved. Also, the restricting portion may be integral with the mounting portion. Because the mounting portion for the reverse bucket may serve as the restricting portion, a simpler construction is achieved.  
      The reverse bucket may have a substantially bowl-shaped base portion, the mounting portion may include mounting portions vertically provided on an upper surface of the pump cover to be located at right and left positions inward of the base portion of the reverse bucket, and the stopper of the reverse bucket may be configured to protrude inward from an inner wall of the base portion.  
      The pump cover may have a mounting portion configured to pivotally mount the reverse bucket, and the reverse bucket may be pivotally mounted by the mounting portion at a position lower than substantially a center line of a flow cross-sectional area of water ejected from the waterjet pump.  
      With the reverse bucket pivoted downward to a lower position, the water ejected from the water jet pump collides with the inner wall of the reverse bucket above the position at which the reverse bucket is pivotally mounted, and the resulting downward moment acts on the reverse bucket. Therefore, when the reverse bucket is pivoted downward to a lower position to move the watercraft rearward, the downward moment acts to inhibit the upward pivot movement of the reverse bucket. Consequently, the reverse bucket is stably held at the lower position.  
      The reverse bucket may include a substantially bowl-shaped base portion, and a flange portion configured to extend outward and rearward in a longitudinal direction of the body from a rear end of the base portion, and the flange portion may be coupled to the base portion to form an angle (reflex angle) larger than 180 degrees between an inner wall of the flange portion and an inner wall of the base portion.  
      In this personal watercraft, if the reverse bucket is pivoted downward while the watercraft is traveling forward with the reverse bucket held at an upper position, the water ejected from the water jet pump collides with the flange portion, which is thereby subjected to an upward external force. Therefore, the reverse bucket can be held at the upper position during the forward travel of the watercraft.  
      The above and further objects and features of the invention will more fully be apparent from following detailed description with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of a personal watercraft according to an embodiment of the present invention;  
       FIG. 2  is a plan view of the personal watercraft in  FIG. 1 ;  
       FIG. 3  is a rear view of the personal watercraft in  FIG. 1 ;  
       FIG. 4  is an enlarged side cross-sectional view showing a rear portion of a water jet pump in  FIG. 1 ;  
       FIG. 5  is a perspective view of a reverse bucket in  FIG. 4 ;  
       FIG. 6A  is a side view of the reverse bucket in  FIG. 5 ;  
       FIG. 6B  is a cross-sectional view of the reverse bucket taken along line VIb-VIb in  FIG. 5 ;  
       FIG. 7  is an enlarged side view of a rear portion of the water jet pump, a part of which is illustrated in cross-section, showing a reverse system of the watercraft in  FIG. 1  traveling rearward; and  
       FIG. 8  is an enlarged side view of the rear portion of the water jet pump, a part of which is illustrated in cross-section, showing the reverse system of the watercraft in  FIG. 1  traveling forward. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Hereinafter, a reverse system of a water-jet propulsion personal watercraft according to an embodiment of the present invention will be described with reference to drawings. The personal watercraft in  FIG. 1  is a straddle-type personal watercraft equipped with a straddle-type seat  7  configured to be straddled by a rider. A body  1  of the watercraft is formed by a hull  2  and a deck  3  covering the hull  2  from above. A line at which the hull  2  and the deck  3  are connected over the entire perimeter thereof is called a gunnel line  4 . The gunnel line  4  is located above a waterline  5  of the personal watercraft being at rest on the water. Herein, directions are described as seen from the perspective of the rider straddling the seat  7 , and looking ahead over the bow of the watercraft. The term “longitudinal direction” is used to refer to an orientation extending from bow to stem of the watercraft, while the term “lateral direction” is used to refer to an orientation extending from starboard to port of the watercraft.  
      As shown in  FIG. 2 , a deck opening  6 , which has a substantially rectangular shape seen from above, is formed on an upper portion of the body  1  at substantially a center section of the deck  3  in the longitudinal and lateral directions of the body  1  to extend in the longitudinal direction of the body  1 . The straddle-type seat  7  is removably mounted over the deck opening  6  and configured to be straddled by the rider.  
      An engine room  8  is formed by a space defined by the hull  2  and the deck  3  below the deck opening  6 . An engine E is accommodated within the engine room  8  and configured to drive the watercraft. The engine room  8  has a convex-shaped transverse cross-section and is configured such that its upper portion is smaller than its lower portion. The engine E is accommodated within the engine room  8  such that a crankshaft  9  extends along the longitudinal direction of the body  1  as shown in  FIG. 1 .  
      An output end of the crankshaft  9  is rotatably and integrally coupled with a pump shaft  11  of a water jet pump P disposed at a rear portion of the body  1  through a drive shaft  10 . An impeller  12  is attached on the pump shaft  11  of the water jet pump P. Fairing vanes  13  are provided behind the impeller  12 . The impeller  12  is covered with a pump casing  14  on the outer periphery thereof.  
      A water intake  15  is provided on the bottom of the body  1 . The water intake  15  is connected to the pump casing  14  through a water passage. The pump casing  14  is connected to the pump nozzle  16  provided at the rear portion of the body  1 . The pump nozzle  16  has a cross-sectional area of flow that is gradually reduced rearward. As shown in  FIG. 3 , an outlet port  17  is formed at a rear end of the pump nozzle  16 .  
      The water jet pump P pressurizes and accelerates the water sucked from the water intake  15 , and the fairing vanes  13  guide the water. The pressurized and accelerated water is discharged rearward through the pump nozzle  16  and from the outlet port  17 , and as the resulting reaction, the watercraft obtains a propulsion force.  
      A bar-type steering handle  19  is attached to a front portion of the deck  3 . The steering handle  19  is connected to the steering nozzle  20  (see  FIG. 3 ) disposed behind the pump nozzle  16  through a cable (not shown). By operating the steering handle  19  clockwise or counterclockwise, the steering nozzle  20  is pivoted clockwise or counterclockwise. By operating the steering handle  19 , the direction of the water ejected outside through the pump nozzle  16  is changed, and the turning direction of the watercraft is changed, while the water jet pump P is generating the propulsion force.  
       FIG. 4  is an enlarged side view of the rear portion of the waterjet pump P. As shown in  FIG. 4 , a substantially bowl shaped reverse bucket  22  is positioned behind and above the steering nozzle  20 . A pump cover  23  is provided on a lower surface of the body  1  under the pump casing  14  to cover the pump casing  14  from below. Mounting portions (pivot portions)  25  are vertically provided on an upper surface of a rear portion of the pump cover  23  to allow the reverse bucket  22  to be pivotable around pivot shafts  24 . As shown in  FIG. 3 , the mounting portions  25  are located on right and left positions inward of a base portion (indicated by reference numeral  30  in  FIG. 5 ) of the reverse bucket  22 . The left mounting portion  25  is shown in  FIG. 4 . As shown in  FIG. 4 , one end of the cable  26  is connected to the reverse bucket  22  at a position upwardly distant from the pivot shaft  24  and the other end thereof is connected to a reverse lever  27  attached to the deck  3  in the vicinity of the handle bar  19  as shown-in  FIG. 1 .  
      By operating the reverse lever  27 , the reverse bucket  22  is vertically pivotable around the pivot shafts  24  provided in the mounting portions  25  of the pump cover  23  as shown in  FIG. 4 . When the reverse bucket  22  is pivoted downward to a lower position around the pivot shafts  24  to be positioned behind the steering nozzle  20 , the water ejected rearward from the steering nozzle  20  collides with an inner wall  30 A (see  FIG. 6B ) of the base portion  30  of the reverse bucket  22  and is directed substantially forward. Thereby, the watercraft is propelled rearward. In  FIG. 4 , a center line  28  of a flow cross-sectional area of the water ejected from the steering nozzle  20  is represented by a dashed line.  
      With reference to  FIGS. 5, 6A , and  6 B, a structure of the reverse bucket  22  will be described in detail. As shown in  FIGS. 5 and 6 A, the inner wall  30 A of the base portion  30  of the reverse bucket  22  is substantially bowl-shaped and a number of ribs  31  are arranged in the longitudinal direction of the body  1  on an outer wall of the base portion  30  to extend in the lateral direction of the body  1 . The reverse bucket  22  is made of synthetic resin. The ribs  31  provide rigidity to the reverse bucket  22 . It will be appreciated that ribs  31  may be omitted, for example, if the reverse bucket  22  is made of a rigid material sufficient to avoid performance degrading deformation during use.  
      Shaft holes  32  are formed on side portions of the base portion  30  to allow the pivot shafts  24  to be inserted therethrough. The reverse bucket  22  is mounted to be vertically pivotable around the pivot shafts  24  mounted in the mounting portions  25  and extending horizontally through the shaft holes  32 . As shown in  FIG. 5 , the shaft holes  32  are provided on the base portion  30  laterally symmetrically to conform to the pivot shafts  24  provided on the right and left mounting portions  25 . As shown in  FIG. 6A , a cable connecting portion  33  is provided at a position upwardly spaced apart a predetermined distance from the right shaft hole  32 , and the one end of the cable  26  ( FIG. 4 ) is connected to the cable connecting portion  33 . As shown in  FIG. 4 , with the reverse bucket  22  positioned behind the steering nozzle  20 , i.e., with the reverse bucket  22  located at the lower position, the cable connecting portion  33  and the shaft holes  32  are located above and below with respect to the center line  28  of the jet flow ejected from the steering nozzle  20 .  
      As shown in  FIG. 6B , the flange portion  34  extends outward and rearward in the longitudinal direction of the body  1  from a rear end of the base portion  30 . The flange portion  34  is coupled to the base portion  30  to form an angle (reflex angle) larger than 180 degrees between an inner wall  34 A of the flange portion  34  and the inner wall  30 A of the base portion  30 .  
      A crank-shaped stopper  35  is vertically provided on the inner wall of the reverse bucket  22  in the vicinity of the left shaft hole  32 . The stopper  35  is in contact with a restricting portion  25   a  ( FIG. 4 ) formed on an end surface of a rear portion of the mounting portion  25  formed on the pump cover  23  for mounting the reverse bucket  22 , when the reverse bucket  22  is located at the upper or lower position. As shown in  FIG. 4 , with the reverse bucket  22  located at the lower position during the rearward travel of the watercraft, a first stopper surface  35   a  of the stopper  35  is in contact with a lower portion of the restricting portion  25   a  formed at the end surface of the rear portion of the left mounting portion  25 , thereby restricting the downward pivot movement of the reverse bucket  22 . By operating the reverse lever  27  ( FIG. 1 ) to cause the reverse bucket  22  to be pivoted downward, the reverse bucket  22  is held at the lower position defined by the restricting portion  25   a  and the stopper  35  in contact with each other.  
      As represented by a two-dotted line in  FIG. 4 , with the reverse bucket  22  located at the upper position during the forward travel of the watercraft, a second stopper surface  35   b  of the stopper  35  is in contact with an upper portion of the restricting portion  25   a  formed at the end surface of the rear portion of the mounting portion  25 , thereby restricting the upward pivot movement of the reverse bucket  22 . By operating the reverse bucket  22  ( FIG. 1 ) to cause the cable  26  to be pulled forward, the reverse bucket  22  is pivoted upward and held at the upper position defined by the stopper  35  and the restricting portion  25   a  in contact with each other. As should be appreciated, the reverse bucket  22  is vertically pivotable within a predetermined range defined by the restricting portion  25   a  and the stopper  35 , and is typically incapable of being pivotable outside this range. In addition, by operating the reverse lever  27 , the reverse bucket  22  is held at the upper or lower position defined by the restricting portion  25   a  and the stopper  35  in contact with each other.  
      As shown in  FIG. 6B , a number of fins  40  are formed on the inner wall  30 A of the base portion  30 . Side fins  41  are provided on right and left sides of the inner wall  30 A of the base portion  30 . Two center fins  42  are provided on the inner wall  30 A of the base portion  30  to be located between the side fins  41 . The side fins  41  and the center fins  42  are configured to extend in substantially the longitudinal direction of the body  1 . The side fins  41  and the center fins  42  are structured such that their rear portions protrude less than their front portions. In  FIG. 6B , the left side fin  41  and the left center fin  42  are illustrated. The side fins  41  and the center fins  42  are provided on the inner wall  30 A of the base portion  30  such that the side fins  41  are laterally symmetric and the center fins  42  are laterally symmetric.  
       FIG. 7  is an enlarged side view of the rear portion of the waterjet pump P, a part of which is illustrated in cross-section, showing the reverse system of the watercraft traveling rearward. As shown in  FIG. 7 , to move the watercraft rearward, the reverse lever  27  ( FIG. 1 ) is operated to cause the reverse bucket  22  to be pivoted downward around the pivot shafts  24 . The water ejected from the steering nozzle  20  collides with the inner wall  30 A of the reverse bucket  22  and is directed substantially forward, thus generating a propulsion force for moving the watercraft rearward.  
      The water colliding with the inner wall  30 A of the base portion  30  and directed substantially forward is controlled by the side fins  41  and the center fins  42 . Consequently, the water ejected from the steering nozzle  20  is smoothly directed substantially straight forward by inhibiting the water from being scattered to the right or to the left. Therefore, the propulsion force generated in the water jet pump P is efficiently changed into the propulsion force for moving the watercraft rearward.  
      Since the shaft holes  32  of the reverse bucket  22  are located lower than the center line  28  of the water flow ejected from the steering nozzle  20 , which substantially conforms to a center line of the steering nozzle  20  in a horizontal direction, a downward moment acts on the reverse bucket  22  when the water ejected from the steering nozzle  20  collides with the reverse bucket  22  during the rearward travel. When the reverse bucket  22  is located at the lower position and receiving the water ejected from the steering nozzle  20 , it is stably held at the lower position by the downward moment, the restricting portion  25   a  and the stopper  35  for restricting the downward pivot movement.  
       FIG. 8  is an enlarged side view of the rear portion of the waterjet pump P, a part of which is illustrated in cross-section, showing the reverse system of the watercraft traveling forward. As described previously, by operating the reverse lever  27  ( FIG. 1 ) to cause the cable  26  to be pulled forward, the reverse bucket  22  is held at the upper position. As a result, the water from the steering nozzle  20  is ejected rearward without colliding with the inner wall  30 A of the reverse bucket  22  and thereby being directed substantially forward, thereby generating the propulsion force for moving the watercraft forward.  
      Here it is assumed that the reverse bucket  22  is pivoted slightly downward when the watercraft is traveling forward. In this case, as shown in  FIG. 8 , the water ejected from the steering nozzle  20  collides with the inner wall  34 A of the flange portion  34  of the reverse bucket  22 . As the resulting reaction, a lifting force is applied to the reverse bucket  22 . When the reverse bucket  22  is in a position that is pivoted slightly downward when the watercraft is traveling forward, the reverse bucket is urged upward by the lifting force generated by the collision of the water with the flange portion  34 . So, the reverse bucket  22  is stably held at the upper position.  
      In accordance with the reverse system constructed as described above, the reverse bucket  22  is stably held at the upper or lower position with a simple construction, i.e., by the restricting portion  25   a  and the stopper  35 . Specifically, since the shaft holes  32  are located lower than the center line  28  of the water flow ejected from the steering nozzle  20 , the reverse bucket  22  is stably held at the lower position during the rearward travel, while the reverse bucket  22  is stably held at the upper position because of the flange portion  34  during the forward travel. Such a simple construction can enhance precision with which the reverse bucket  22  is positioned at the upper or lower position.  
      While the reverse bucket  22  is pivotally mounted by the mounting portions  25  and a pivot movement range of the reverse bucket  22  is restricted by the restricting portions  25   a,  which are integral with the mounting portions  25 , as well as by the stopper  35 , the restricting portion for restricting the pivot movement range and the mounting portion for mounting the reverse bucket may alternatively be separately provided.  
      As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.