Abstract:
An aquatic vegetation shredder includes a double hull watercraft, with a space being defined between the hulls. The machine also includes an aquatic vegetation shredding assembly mounted to the watercraft adjacent the bow end, and a pair of propellers rotatably mounted to the watercraft adjacent the stem end. The propellers are configured to propel the watercraft through the water and draw water through the space defined between the hulls. Such a design causes the vegetation to be drawn toward the vegetation shredding assembly, while preventing the shredded vegetation from accumulating at the assembly; thereby eliminating the need for feeding devices for feeding the vegetation to the shredding assembly and discharge chutes for discharging the shredded vegetation away from the assembly. In addition, the propellers are operable to shred vegetation, thereby ensuring destruction of vegetation below the water surface and further commination of vegetation received from the shredding assembly. These features cooperatively provide a low displacement vessel that is particularly effective in shallow water environments.

Description:
RELATED APPLICATION 
     This is a continuation of application Ser. No. 09/167,911 filed Oct. 7, 1998 now U.S. Pat. No. 6,116,004. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to equipment for shredding, harvesting, destroying or otherwise processing aquatic vegetation. More specifically, the present invention concerns an improved aquatic vegetation shredder that is more effective in destroying troublesome vegetation and versatile than most conventional devices. 
     2. Discussion of Prior Art 
     Aquatic vegetation can be devastating to both marine operations and the aquatic ecosystem. Unfortunately, most conventional expedients are ineffective in destroying or otherwise controlling such vegetation. These problems have previously been identified in our co-pending application for U.S. patent Ser. No. 08/993,072, filed Dec. 18, 1997, entitled APPARATUS FOR DESTROYING AQUATIC VEGETATION, assigned of record to the assignee ofthe present invention and now U.S. Pat. No. 6,023,920. 
     Our prior invention addresses these problems by providing, among other things, a design that is particularly successful in delivering vegetation to the shredding assembly. Accordingly, the vegetation is not simply pushed by the vessel as it moves through the body of water, nor does the vegetation pass around or under the vessel without being shredded. Our prior inventive design is also particularly useful in destroying aquatic vegetation without requiring removal ofthe vegetation from the body of water. That is to say, with our prior invention, the shredded vegetation is left in the body of water, with a minimum risk of regrowth. We have now determined that, in some instances, it would also be beneficial to have an aquatic vegetation shredder that is designed for shallow water, as well as deep water. It is also highly desirable to provide an aquatic vegetation shredder with means for shredding vegetation both generally at the water surface and well below the water surface to ensure that virtually all, or at least most, of the plant is shredded. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Responsive to these and other problems, an important object of the present invention is to eliminate the troubles presented by aquatic vegetation, as noted in our prior application. Particularly, an important object of the present invention is to provide a machine for destroying a dense, entangled mass of aquatic vegetation so as to improve marine navigation and reduce the risk of damage to the aquatic ecosystem. It is also an important object of the present invention to provide a machine for destroying aquatic vegetation that does not require the use of chemical or biological agents. Another important object of the present invention is to provide a machine that is particularly effective in presenting the vegetation to the shredder assembly and in destroying the vegetation without requiring removal of the vegetation from the water. In particular, it is an important object of the present invention to provide such a machine that is also designed for shallow water, as well as deep water. Yet another object of the present invention is to provide an aquatic vegetation shredder with means for shredding vegetation both at the water surface and well below the surface. 
     In accordance with these and other objects evident from the following description of the preferred embodiment, the present invention concerns an aquatic vegetation shredder including a double hull watercraft, with a space being defined between the hulls. An aquatic vegetation shredding assembly is mounted to the watercraft adjacent the bow end, and a pair of propellers are rotatably mounted to the watercraft adjacent the stern end. More importantly, the propellers are configured to propel the watercraft through the water and draw water through the space defined between the hulls. Such a design causes the vegetation to be drawn toward the vegetation shredding assembly, while preventing the shredded vegetation from accumulating at the assembly; thereby eliminating the need for feeding devices for feeding the vegetation to the shredding assembly and discharge chutes for discharging the shredded vegetation away from the assembly. In addition, the propellers are operable to shred vegetation, thereby ensuring destruction of vegetation below the water surface and further commination of vegetation received from the shredding assembly. These features cooperatively provide a low displacement vessel that is particularly effective in shallow, as well as deep, water environments. 
     Other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     Preferred embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein: 
     FIG. 1 is a perspective view of an aquatic vegetation shredder constructed in accordance with the principles of the present invention; 
     FIG. 2 is a rear perspective view of the machine shown in FIG. 1, particularly illustrating the space between the hulls of the boat and the large propellers mounted to the hulls; 
     FIG. 3 is an enlarged, fragmentary perspective view of the stem end of the starboard hull, particularly illustrating the structure for adjustably mounting the propeller to the hull, the drive mechanism for the propeller, and the recess defined in the hull immediately forward of the propeller; 
     FIG. 4 is a top plan view of the machine; 
     FIG. 5 is a side elevational view of the machine; and 
     FIG. 6 is an enlarged, fragmentary perspective view of the bow end of the starboard hull, particularly illustrating the construction of the vegetation shredding assembly, and the decking spanning the space between the hulls. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning initially to FIG. 1, the aquatic vegetation shredder  10  selected for illustration includes a twin hull boat  12 , with each hull  14  and  16  being generally identical in construction. For the sake of brevity only the port hull  14  will be described in detail, with the understanding that the starboard hull  16  is similarly constructed. As perhaps best shown in FIG. 3, the port hull  14  has a design similar to a barge-type vessel, with a pair of flat, substantially parallel top and bottom walls  18  and  20 , respectively, and a pair of flat, substantially parallel outer and inner side walls  22  and  24 , respectively. The stem wall  26  includes an upper section  26   a  that is perpendicular to the top wall  18  and a lower section  26   b  that extends downwardly and forwardly from the upper section  26   a  to the bottom wall  20 . For purposes which will subsequently be described, a recess  28  extends inwardly from the inner side wall  24  and stem wall  26 . Although not shown in detail, it will be appreciated that the bow wall includes an upper vertical section and a lower angled section similar to the stem wall  26 . However, the bow end of the hull  14  does not include a recess as defined in the stem end. 
     Although the above-noted hull construction is preferred, it is entirely within the ambit of the present invention to utilize various other double hull boat designs. However, in any case, it is critical that a space be defined between the hulls, for purposes which will subsequently be described. In this respect, with the illustrated boat  12 , the hulls  14  and  16  are spaced laterally apart (see FIG. 2) to define a space  30  between the inner side walls that has a lateral dimension slightly larger than half the width of each of the hulls. The space  30  extends along the entire length of the boat  12  and from the top walls to the bottom walls of the hulls. 
     The hulls  14  and  16  are maintained in the spaced apart relationship by a forward cross beam  32  extending laterally across the top walls ofthe hulls (see FIGS.  1 - 2 , 4  and  6 ). The cross beam  32  is fixed to the outer side walls of the hulls  14  and  16  by respective brackets  34  and  36 , with each of the brackets including a hole for facilitating hoisting and land transport of the boat  12 . A rear cross beam  38  is likewise secured to the hulls  14  and  16  by similar brackets  40  and  42 . In addition, a decking  44  spans the space  30  defined between the hulls  14  and  16 . The decking  44  includes a substantially flat plate  46  that marginally overlies the top walls of the hulls  14  and  16 , and a plurality of spaced triangular-shaped braces  48  fixed to the underside ofthe plate  46  (see FIG.  6 ). The braces  48  preferably have a length corresponding to the lateral dimension of the space  30  so as to extend from the inner side wall of one of the hulls to the inner side wall of the other hull. If desired, the plate  46  and braces  48  may be secured (e.g., by welding) to the adjacent portions of the hulls. It will be noted that the illustrated decking is sectioned along the length of the boat, with spaces often being defined between adjacent sections of the decking. For example, the decking  44  does not extend underneath the cross beams  32  and  38 , as perhaps best shown in FIG.  4 . It will also be noted that the bow end of the flat plate  46  has been partially cut away so as to expose the underlying space  30 . 
     Adjacent the stern end of the boat  12  is a cover  50  housing a power source (not shown) for providing operating power to the various components of the shredder  10 . In the preferred embodiment, the power source includes an internal combustion engine (not shown) and a pressurized hydraulic power unit (not shown) drivingly connected to the engine. A suitable engine is available from General Motors Corporation as Model No. ZZ4, rated at 350 horsepower. The engine and hydraulic power unit are conveniently controlled from a cab  52  located generally at the center of the boat  12 . In the illustrated embodiment, a fuel tank  54  for the engine is mounted to the decking  44  adjacent the bow end of the boat  12 . 
     An aquatic vegetation shredding assembly  56  is mounted to the boat  12  at the bow end. In particular, a frame  58  swingably mounted to the boat  12  includes a pair of fore-and-aft arms  60  and  62  and a transverse bar  64  (see FIGS. 2 and 4) fixed between the arms  60 , 62  adjacent their forward ends. The arms  60  and  62  are pivotally attached to respective ones of the hulls  14  and  16  by brackets  66  and  68  (see FIGS.  1  and  4 ), and are disposed outwardly from the hulls  14 , 16  so as to permit swinging of the frame  58  below the top walls of the hulls  14 , 16 . Swinging ofthe frame  58  is controlled by a double-acting hydraulic piston and cylinder assembly  70  pivotally mounted to the top wall of the starboard hull  16 . A cable  72  is connected between the hydraulic assembly  70  and the transverse bar  64 , such that the frame  58  swings downwardly as the assembly  70  extends and swings upwardly as the assembly  70  retracts. It will be noted that the cable  72  partially entrains a pulley  74  rotatably mounted to the starboard hull  16  by a stand  76 . 
     At the forward ends ofthe arms  60  and  62  are a pair of enlarged supports  78  and  80  (see FIG. 4) for supporting respective bearing assemblies  82  and  84  (see also FIG.  1 ). The bearing assemblies  82  and  84  journal respective stub shafts  86  and  88  that cooperatively support a cylindrical drum  90  therebetween, whereby the drum  90  is rotatably supported between the arms  60  and  62 . A plurality of knives  92  are swingably supported on the drum  90  similar to a conventional flail-type cutter used in the agricultural industry. As perhaps best shown in FIG. 6, each knife  92  includes a pair of outwardly diverging blades  94  and  96  fixed to one another and pivotally mounted between a pair of posts  98  and  100  projecting radially from the drum  90 . Although the blades  94  and  96  of the illustrated knives  92  are shown in a radial orientation, it will be appreciated that the blades  94  and  96  are free to pivot and therefore droop downwardly as a result of gravity when the drum  90  is stationary. It will also be noted that the knives  92  are arranged in rows spaced along the length ofthe drum  90 , with each of the rows including a pair of knives mounted to the drum  90  in diametrically opposite locations. A shield  102  covers generally the upper rear quadrant of the drum  90  so as to prevent water and debris from being thrown toward the cab  52 . 
     The drum  90  is driven by a reversible, variable speed hydraulic motor  104  mounted to the starboard side of the frame  58  adjacent the support  80  by a stand  106 , although a pair of motors may be used to drive the drum  90 , if desired. A chain and sprocket drive serves to couple the drum  90  to the motor  104 . In particular, a chain  108  entrains a sprocket  110  mounted to the output shaft  112  of the motor  104  and extends downwardly and forwardly to entrain a sprocket  114  mounted to the stub shaft  88  (see FIG.  6 ). The sprocket ratios (i.e., relative sizes) maybe varied for adjusting the rotational speed of the drum  90 . The hydraulic motor  104  is coupled to the power source via the cab  52  so that the operator may control driving power to the drum  90 . Preferably, the drum  90  is driven in the direction of arrow  116  shown in FIG. 5, at a speed dependent upon the type of vegetation encountered. For example, when the illustrated flail-type shredding assembly  56  is used to destroy water hyacinth, the drum  90  is preferably rotated at approximately 1000 revolutions per minute. Additionally, the hydraulic piston and cylinder assembly  70  is extended to swing the frame  58  downwardly until the knives project approximately three (3) to four (4) inches below the water surface. The hydraulic piston and cylinder assembly  70  is similarly coupled to the power source via the cab  52 , whereby the operator may similarly control swinging of the frame  58  from the cab  52 . 
     However, it is entirely within the ambit ofthe present invention to utilize other variously constructed shredding assemblies. For example, the present invention contemplates the use of a shredding assembly having a plurality of laterally spaced circular blades (similar to the machine disclosed in our prior application). 
     In any case, it is important that the shredder  10  includes structure for drawing water through the space  30  and for providing additional commination of the vegetation. In the illustrated embodiment, this structure includes a pair of large, high speed propellers  118  and  120  rotatably mounted to the hulls  14  and  16 , respectively. The propellers  118  and  120  are nearly identical in construction. Thus, for the sake of brevity, only the port propeller  118  will be described in detail herein with the understanding that the starboard propeller  120  is similarly constructed. 
     The propeller  118  includes six blades  122  projecting radially from a central hub  124  mounted to a rearwardly extending shaft  126 . The illustrated propeller blades  122  are fixed at a thirty degree pitch, although a variable pitch propeller may be used, if desired. As shown in FIG. 3, the shaft  126  is journaled by a pair of bearing assemblies  128  and  130  adjustably mounted to respective vertical support plates  131  and  132 . The support plates  131 , 132  are fixed to the recessed wall  133  of the port hull  114 , and include a series of threaded holes into which fasteners are selectively inserted for fastening the bearing assemblies in an adjustable position. Accordingly, the propeller  118  rotates about a vertically shiftable fore-and-aft axis defined by the shaft  126 . Those ordinarily skilled in the art will appreciate that other variously constructed structure may be utilized to permit depth adjustment of the propeller  118 , such as a swingable frame similar to the frame  58  of the shredding assembly  56 . 
     As perhaps best shown in FIG. 4, the diameter of the propeller  118  is greater than the width and height of the hull  14  (one suitable propeller diameter is approximately forty-eight inches). Moreover, the rotational axis (i.e., shaft  126 ) of the propeller  118  is located slightly closer to the inner side wall  24  than the outer side wall  22 , such that the propeller  118  projects only slightly outwardly beyond the outer side wall  22  but well beyond the inner side wall  24 . This configuration ensures that the propeller  118  effects water flow through the space  30 , as will subsequently be described. Further, the propellers  118  and  120  cooperatively extend across the full width of the boat  12  (except for the small space defined therebetween) and project outwardly beyond the port and starboard sides. It may therefore be said that the propellers  118  and  120  are operable to chop vegetation across at least substantially the full width of the boat  12 . 
     The propeller  118  is driven by a reversible, variable speed hydraulic motor  134  mounted to the top wall  18  of the port hull  14  by a generally U-shaped stand  136 . In particular, the propeller  118  is drivingly connected to the motor  134  by a chain  138  entraining a sprocket  140  supported on the output shaft  142  of the motor  134  and a relatively larger sprocket  144  supported on the propeller shaft  126 . The links of the chain  138  are preferably interconnected by cotter keys for providing quick and easy addition or subtraction of links, thereby facilitating adjustment of the chain length as the propeller  118  is moved up or down. The motor  134  is connected to the power source via the cab  52  so that the operator controls the speed and direction of the propeller. 
     In the illustrated embodiment, the propellers  118  and  120  are independently controllable so as to improve maneuverability. However, the term “independent” as used herein shall not be interpreted to mean that the propellers  118  and  120  must operate at different speeds or directions of rotation relative to one another, nor that the propellers cannot be operated simultaneously by suitable controls in the cab  52  that ensure the propellers rotate at the same speed and direction. In any case, the blades of the starboard propeller  120  preferably have the same degree of pitch as the blades of the port propeller  118 , but are pitched in an opposite direction. Accordingly, when it is desired to propel the boat  12  in a forward direction, the propellers  118  and  120  are rotated in opposite directions as indicated by the arrows  146  and  148  in FIG.  2 . The direction of rotation of both propellers  118 , 120  would be reversed when propelling the boat in the rearward direction. It will also be noted that the propellers  118 , 120  may be rotated at different speeds to turn the boat  12  in a direction opposite from the relatively faster turning propeller, and the propellers may be rotated in the same direction to perform a so-called “zero radius turn.” 
     Although the illustrated propellers  118  and  120  are independently vertically adjustable, it is preferred that the propellers be at the same vertical location so as to have substantially the same or equal impact on operation. It will also be appreciated that the propellers  118 , 120  are depth adjustable for a variety of reasons. For example, in some plant environments, the shredding assembly  56  is incapable of projecting sufficiently below the water surface to destroy the vegetation. Accordingly, the propellers  118 , 120  can be positioned as low as necessary to shred the lower portions of plants. It is believed that the cutting action provided by the propellers  118 , 120  is primarily attributable to their multi-bladed, axial configuration and the relatively high speed (e.g., 350 revolutions per minute) at which they are rotated. On the other hand, in relatively shallow conditions, the propellers  118 , 120  may be raised, as necessary, to avoid interference with the bed yet still provide their intended chopping, water-drawing and propulsion functions. In the illustrated position, the propellers  118 , 120  project upwardly out ofthe water, which is particularly useful during rearward travel of the boat  12 . Specifically, it is believed that vegetation is not likely to collect on the propellers  118 , 120  primarily because the propellers shed vegetation and water as they project upwardly out of the water. 
     A shroud  150  connected to the stern end of the hulls  14 , 16  projects rearwardly to overhang the portions of the propellers  118 , 120  projecting upwardly out of the water. Accordingly, the shroud  150  prevents water and vegetation from being thrown upwardly onto the boat  12  by the propellers  118 , 120 . To accommodate vertical adjustment of the propellers, the shroud  150  may likewise need to be adjustably mounted to the hulls  14 , 16 . 
     In use, the illustrated vegetation shredder  10  is designed for forward travel, with the shredding assembly  56  essentially cutting a path through the vegetation as the boat  12  is propelled through the water by the propellers  118 , 120 . However, that is not to say that the shredder  10  is incapable of moving rearwardly through a vegetation infested body of water. In fact, when the boat  12  is moved in a rearward direction, the propellers  118 , 120  convey vegetation outwardly to the sides of the boat  12  so that the hulls  14 , 16  are able to move through the water without accumulating vegetation thereon. This is primarily attributable to the direction of rotation of the propellers and the pitch of the propeller blades. In addition, the vegetation is comminuted by the propellers, thereby cutting a path in the vegetation similar to the shredding assembly  56 , as previously noted. Again, operation in the rearward direction is not likely to be affected, when the propellers  118 , 120  are in their illustrated positions, primarily because the propellers shred vegetation and water as they project upwardly above the water surface. 
     As noted above, when the boat  12  is propelled in the forward direction, the shredding assembly  56  is positioned so that the swingable knives  92  project several inches below the water surface. It has been determined that such a configuration ensures adequate comminution of surface plants to prevent regrowth. The vegetation shredded by the assembly  56  is either picked up by the spinning knives  92  and directed forwardly by the shield  102  or simply left in the water. As the boat  12  travels forwardly, the shredded vegetation in the water passes through the space  30  or around the outside of the hulls  14  and  16 . It will be appreciated that movement of shredded vegetation through the space  30  is promoted by the propellers  118 , 120 . In particular, the propellers  118 , 120  draw water rearwardly through the space  30  at a velocity greater than the forward speed of the boat  12 . This is also important in drawing uncut vegetation toward the shredding assembly  56 . It is believed that the “water-drawing” action of the propellers  118 , 120  is at least in part attributable to the fact that the propeller blades extend inwardly beyond the inner side walls of the hulls  14  and  16 . The large size and high speed rotation of the propellers  118 , 120  are also believed, to contribute to the desired water-drawing action. It is also believed that this action of the propellers  118 , 120  is enhanced by the recesses defined in the stern ends of the hulls  14 , 16  (possibly as a result of the recesses serving a function similar to a plenum for a fan). Similar to the shredding assembly  56 , the vegetation encountered by the propellers  118 , 120  is comminuted. In all most all cases, this will involve further shredding of vegetation previously processed by the shredding assembly  56 , thereby providing dual-stage shredding of the vegetation. In addition, the propellers  118 , 120  will shred any material at the water surface which was not previously processed by the shredding assembly  56 . The propellers  118 , 120  are also likely to draw vegetation from depths below the shredding assembly  56  and shred such vegetation. Moreover, the propellers  118 , 120  may be positioned at a depth to ensure shredding of vegetation at depths below the shredding assembly  56 . 
     In any case, the large, high speed propellers  118 , 120  serve the triple purpose of propelling the boat  12 , drawing water through the space  30 , and chopping vegetation encountered by the propellers  118 , 120 . As noted above, the water-drawing function promotes movement of the shredded vegetation around the hulls and also serves to draw uncut vegetation toward the shredding assembly  56 . The vegetation chopping function of the high speed propellers  118 , 120  provides dual-stage comminution of the vegetation generally at the water surface, and shredding of vegetation below the shredding assembly  56  which might not otherwise be processed by the shredder  10 . It will also be appreciated that the present invention also provides a design that is well-suited for shallow water conditions. The displacement of the illustrated shredder  10  is such that the boat  12  is operable in water depths as shallow as eighteen inches. It will be noted that the depth adjustability ofthe propellers  118 , 120  and the swingability of the frame  58  permits the propellers  118 , 120  and shredding assembly  56  to be positioned above the bottom of the hulls  14  and  16 , as shown in the drawings, thereby ensuring operability in shallow water conditions. 
     The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
     The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.