Abstract:
A method and apparatus for dredging sediment from aquatic environments and cutting aquatic vegetation therein includes using a cutterhead mounted to a dredge. The cutterhead may be mounted to a shroud, the cutterhead including a rotating drum having an array of teeth assemblies which auger cut vegetation toward a port in the shroud for discharge via a pump. The shroud also includes stationary cutterbars having cutterbar teeth assemblies. The teeth assemblies preferably include back-to-back tooth pairs wherein individual teeth have a flat backside and a raised or convex front side which may be provided with serrated cutting margins. Using back-to-back tooth pairs enables cutting of more types and sizes of aquatic vegetation, reducing downtime due to clogging, bending or breakage versus conventional single teeth cutterheads. The shroud may include an upwardly and/or forwardly extending shield along its top front edge to deflect water and/or vegetation back toward the drum.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/698,476 filed Sep. 7, 2012, U.S. Provisional Patent Application No. 
         [0002]    61/735,905 filed Dec. 11, 2012, and U.S. Provisional Patent Application No. 61/803,744 filed Mar. 20, 2013, the entire disclosures of which are incorporated hereby by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    This invention broadly concerns a cutterhead and associated method for cutting weeds and other aquatic vegetation which cuts the weeds using angled teeth mounted to a rotating drum. More particularly, the cutterhead hereof provides a tearing action which also directs the cut vegetation and any sediment into a pump for removal to a remote site, utilizing an improved teeth arrangement employing double, back-to-back cutting teeth. 
         [0005]    2. Description of the Prior Art 
         [0006]    Many types of dredging operations encounter weeds or massed vegetation which has grown on sludge deposited in lagoons, in channels, or in other waters where removal is periodically required. Often the weeds or other aquatic vegetation represents an impediment to the removal of the underlying sludge, sand, silt or other deposits, because of the clogging effect of the vegetation. Cattails and plants with longs stems and gnarly roots often grow in sediment lagoons and in channels, and when the sediment is to be removed during dredging, these plants are especially tenacious and prone to cause clogging of the pumps. Moreover, they tend to wrap around many types of cutterheads typically used for clearing sediment. The entire dredging head must then be removed so that the plants can be cut away from the cutterhead. Thus, dredging in areas which have a large amount of aquatic vegetation represents one of the most difficult environs for sediment removal. 
         [0007]    Many different types of apparatus have been used for cutting and removing aquatic vegetation. Exemplary devices of the prior art are shown in U.S. Pat. Nos. 669,820; 1,028,671; 1,795,003; 2,223,641; 2,486,275; 2,635,406; 2,702,975; 3,238,708; 3,407,577; 3,468,106; 3,653,192; 4,070,978; 4,095,545; 4,196,566; 4,205,507; 4,416,106; 4,248,033; 4,616,588; and 4,815,260. Unfortunately, none of these devices have solved the problems associated with wrapping of the plants around the cutterhead, nor have they adequately worked with the pumping system to remove the cut vegetation and the sediment to be removed. 
         [0008]    An improvement to existing cutterheads is also shown in U.S. Pat. No. 5,481,856, the entire disclosure of which is incorporated herein by reference. However, the cutterhead of U.S. Pat. No. 5,481,856 utilized single, flat-sided teeth which broke, folded or clogged when attempting to dredge and cut particularly tough aquatic vegetation such as reeds, cattails or tussiks. Furthermore, the prior cutterheads have experienced deficiencies when cutting and harvesting aquatic vegetation at the surface of a body of water resulting from temporary loss of liquid and solid intake resulting in starvation of the pump. Such pump starvation causes loss of pump prime and the necessity to stop harvesting until the pump is reprimed. 
         [0009]    Accordingly, there has developed a need for a weed-resistant cutterhead for use in aquatic environments, such as ponds, lakes, canals and waterways, which is capable of removing sediment and vegetation in plant-clogged areas. 
         [0010]    There has also developed a real need for a cutterhead which is resistant to wrapping of long plant growth around the ends of a rotatable drum or reel. 
         [0011]    There has also developed a need for a cutterhead which can direct the sediment and cut vegetation to an outlet port for pumping to a remote location. 
         [0012]    There is a further need for a cutterhead having improved capabilities for harvesting vegetation at the surface of a body of water. 
       SUMMARY OF THE INVENTION 
       [0013]    These and other objects are largely met by the cutterhead and method of harvesting aquatic vegetation of the present invention. That is to say, the cutterhead of the present invention is intended to operate underwater and at the surface of a body of water as well, and is more resistant to clogging or breakage than the prior art. It cooperatively removes sedimentation and cuts aquatic vegetation, and may be used in a variety of aquatic environments. 
         [0014]    The invention hereof broadly includes a drum mounted for rotation and carrying a plurality of teeth assemblies, and a shroud which is provided with at least one cutterbar with teeth assemblies arranged in a tearing relationship with the drum mounted teeth assemblies to cut, writhe and rend vegetation which undesirably wraps around the drum or drapes across the drum teeth assemblies. The shroud may be provided with a port for passing the material cut by the drum to a pump or pipe for passage to a remote site. The drum mounted teeth assemblies are preferably arrayed whereby they effectively operate not only to cut the plant material but also pass the cut vegetation along the drum in the manner of an auger during rotation. Further, the teeth assemblies are preferably oriented whereby the stationary teeth assemblies on the cutterbars pass through gaps at the points of the rotating drum mounted teeth assemblies during rotation to effect more complete cutting and a self-cleaning action. The teeth assemblies are provided as pairs of individual teeth members, each of the individual teeth members preferably having a substantially flat back side and a raised, somewhat convex front side and a cutting margin which most preferably includes a pair of serrated edges which intersect at a point. More preferably, the teeth assemblies are provided as back-to-back pairs of individual teeth members which have been welded to one another, most preferably by plug welding. 
         [0015]    Most preferably, the shroud for the cutterhead of the present invention may be provided with upper and lower stationary cutterbars for enhanced tearing action with the rotating drum-mounted teeth, whereby the stationary teeth assemblies may be suitably spaced for maintenance while providing enhanced transverse coverage to clear vegetation between the points of the drum-mounted teeth assemblies. In especially preferred embodiments, the cutterhead hereof may include teeth assemblies mounted adjacent the ends of the drum and projecting outwardly from the drum&#39;s axis of rotation to cut vegetation which may pass between the drum and the shroud and otherwise wrap around the shaft or hub rotatably carrying the drum. Because aquatic vegetation may pass through even tight tolerances, the inclusion of these outwardly projecting teeth assemblies enhances the operation of the drum by severing lengthy strings of plant material which would otherwise wrap around the shaft or hub. 
         [0016]    Preferably, while dredging silt, sand and clay, a conventional dredge cutterhead should be utilized. The cutterhead of the present invention may be most effectively directed into dense plant growth on submerged sediment deposits and simultaneously remove the sediment and cut plant stalks and root masses. The cutterhead hereof continues to be effective in removing sediment deposits after the plant material has been cut away, most preferably completely. Thus, optimal operating effectiveness and efficiency may be seen when the operator replaces the cutterhead of the present invention with a conventional dredge cutterhead once the weed cover on a lake, canal or other body of water is removed, as such conventional dredge cutterheads are more abrasive resistant and will last longer without maintenance in sand and coarse sediment environments. 
         [0017]    The cutterhead of the present invention may be provided with a shield which extends forwardly of a top edge of the cutterhead shroud with respect to the direction of movement of the cutterhead. By positioning such a shield at the top of the cutterhead shroud, several disadvantages of prior cutterheads have been overcome. The shield effectively blocks displacement of much water and cut vegetation from passing over the upper surface of the cutterhead shroud. By the provision of the shield, water and vegetation is directed back into the path of the cutterhead, yielding advantages not previously contemplated. For example, when the cutterhead is operating at or near the surface of a body of water, the shield helps to avoid pump starvation when too little liquid and cut vegetation enters the slurry pump, and thus more consistent and continuous operation is achieved, which is lost when the forward movement of the cutterhead must be stopped and the cutterhead lowered to again achieve a satisfactory priming of the pump and constant liquid flow during harvesting operations. Another advantage which may be obtained by the use of the shield is to direct the cut vegetation back into the cutterhead so that it may be pumped and moved to a remote location. It is desirable to remove as much vegetation from a body of water as possible because many species of aquatic vegetation are self-propagating. By inhibiting the passage of cut vegetation over the top of the cutterhead when the cutterhead is operating at the surface of a body of water, more cut vegetation is directed into the interior of the shroud and pumped to a remote location. 
         [0018]    In particularly preferred embodiments, the shield is adjustably mounted to the top front edge of the shroud so that its angle relative to the shroud may be changed. In this way, the angle that vegetation enters the cutterhead may be changed and more vegetation may be directed into the cutterhead for harvesting. Preferably, the shield may be adjustably positioned through a range of angles between about 0° or parallel to the top of the cutterhead shroud, to about 90° or perpendicular to a plane along the top of the cutterhead shroud. For example, in cutting taller rooted vegetation, it is desirable to push the top of the vegetation away from the head and start cutting up the vegetation from the bottom or lower portion of the plant. The adjustable shield helps to accomplish this by positioning the shield at an angle of between about 30° to 40° from a plane extending forwardly along the top surface of the shroud, allowing for better operational efficiency. For entangled vegetation which is lower in height or vegetation that grows runners, the shield may be pivoted to a position closer to about 90° from a plane extending along the top surface of the shroud so that more of the vegetation can get processed by the cutting teeth and pull itself and adjoining plants into the cutterhead. In either position, the shield helps prevent the vegetation from getting behind the cutting head and between pontoons or into the hull area of the vessel performing the harvesting operations, which can interfere with raising and lowering a ladder or arms, or can entangle in propulsion systems. 
         [0019]    In one embodiment, the cutterhead of the present invention may include a first stationary cutterbar having a first set of spaced-apart cutterbar teeth assemblies mounted therealong and a second stationary cutterbar having a second set of spaced-apart cutterbar teeth assemblies mounted therealong, with the first and second stationary cutterbars mounted on a cutterhead shroud. This embodiment may further include a drum rotatably mounted proximate the cutterhead shroud, the drum having a substantially smooth drum surface and presenting a plurality of radially projecting drum teeth assemblies therealong, and having means for rotatably mounting the drum proximate the cutterheads. Also included are means mounting the drum teeth assemblies so as to present gaps between the points thereof, whereby some of the drum teeth assemblies pass closely adjacent the first set of cutterbar teeth assemblies in tearing relationship thereto and others of the drum teeth assemblies pass closely adjacent the second set of cutterbar teeth assemblies, in tearing relationship thereto, during rotation of said drum. In this embodiments, the drum teeth assemblies may also include a first tooth and a second tooth, each of the teeth having a flat back, a raised front and a cutting margin, the first and second teeth being mounted in back-to-back arrangement whereby their cutting margins are adjacent and the backs are substantially co-planar. 
         [0020]    In another embodiment, the present invention of cutting aquatic vegetation may include a cutterhead shroud having an port for passing cut vegetation therethrough, a drum and means mounting the drum for rotation relative to said shroud, a motor for rotating the drum, and an array of drum teeth assemblies projecting radially from the drum, the array being of a substantially helical configuration about the drum for promoting movement of the cut vegetation to the port during rotation of said drum, wherein the drum teeth assemblies include a first tooth and a second tooth, each of the teeth having a flat back, a raised front and a cutting margin, the first and second teeth being mounted in back-to-back arrangement whereby their cutting margins are adjacent and the backs are substantially co-planar. 
         [0021]    In yet another embodiment, the cutterhead of the present invention may include a first stationary cutterbar presenting a first set of spaced-apart cutterbar teeth assemblies mounted therealong, a second stationary cutterbar presenting a second set of spaced-apart cutterbar teeth assemblies mounted therealong, and a cutterhead shroud mounting the first and second stationary cutterbars. This embodiment may further include a drum rotatably mounted proximate the cutterhead shroud, the drum having a substantially smooth drum surface and presenting a plurality of radially projecting drum teeth assemblies therealong, and means rotatably mounting the drum proximate the cutterheads. This embodiment may also include means mounting the drum teeth assemblies to present gaps between the points thereof whereby some of the drum teeth assemblies pass closely adjacent said the set of cutterbar teeth assemblies in tearing relationship thereto, and others of the drum teeth assemblies pass closely adjacent the second set of cutterbar teeth assemblies in tearing relationship thereto during rotation of the drum. Further, this embodiment may include a shield mounted to the cutterhead shroud and extending forwardly and/or upwardly from a top front edge of the cutterhead shroud. 
         [0022]    In a further embodiment, the present invention includes a method for cutting aquatic vegetation. That method can include the steps of providing a dredge having a pump and means for conveying cut vegetation from the pump, the pump mounting a cutterhead having a shroud and a drum, the drum having a substantially helical array of drum teeth assemblies, the teeth assemblies including a first tooth and a second tooth, each of the teeth having a flat back, a raised front and a cutting margin, the first and second teeth being mounted in back-to-back arrangement whereby their cutting margins are adjacent and the backs are substantially co-planar, and the shroud having at least one stationary cutterbar presenting a plurality of cutterbar teeth assemblies, at least some of the cutterbar teeth assemblies being oriented in vegetation tearing relationship to the drum when the drum is rotated relative to the shroud, with the shroud further including a port for passing cut vegetation to the pump; placing the cutterhead in engagement with aquatic vegetation; rotating the drum to cut the vegetation; moving the vegetation transversely along the drum by augering action of the helical array of teeth; and passing the vegetation through the port and into the pump. 
         [0023]    In a still further embodiment, the present invention includes a method for cutting aquatic vegetation, wherein the method includes the steps of providing a dredge including a pump and means for conveying cut vegetation from the pump, the pump mounting a cutterhead having a shroud and a drum, the drum presenting a substantially helical array of drum teeth assemblies, the shroud having at least one stationary cutterbar presenting a plurality of cutterbar teeth assemblies, at least some of the cutterbar teeth assemblies being oriented in vegetation tearing relationship to the drum when the drum is rotated relative to the shroud, the shroud further including a port for passing cut vegetation to the pump, and a shield extending upwardly and/or forwardly of a top front edge of the shroud; placing the cutterhead in engagement with aquatic vegetation; rotating the drum to cut the vegetation; moving said vegetation transversely along said drum by augering action of said helical array of teeth; deflecting water and/or vegetation contacting the shield towards the rotating drum; and passing the vegetation through the port and into the pump. 
         [0024]    These and other advantages of the cutterhead and method of the present invention will be evident to those skilled in the art with reference to the drawings and the detailed discussion which follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a perspective view of the cutterhead of the present invention mounted on a boom connected to a dredge; 
           [0026]      FIG. 2  is an enlarged fragmentary side elevational view showing the cutterhead hereof coupled to a pump and motor for passing the cut vegetation through the boom; 
           [0027]      FIG. 3  is an enlarged top plan view of the cutterhead drum and shroud, with a portion of the shroud broken away to show an upper cutterbar and its teeth assemblies, the remainder of which is shown in phantom; 
           [0028]      FIG. 4  is an enlarged front elevational view showing the drum and shroud, with portions one of the drum end halves removed to show the drum end mounting arrangement, and with some of the teeth assemblies shown in phantom; 
           [0029]      FIG. 5  is an enlarged front elevational view similar to  FIG. 4  but showing the port through the shroud in phantom, and portions of the drum end halves removed to show the shaft and motor for rotating the drum; 
           [0030]      FIG. 6  is an enlarged vertical cross-sectional view taken through line  6 - 6  of  FIG. 4 , showing the mounting relationship of the teeth assemblies on the drum, the upper and lower cutterbars and the respective teeth assemblies thereof, and adjacent the ends of the drum; 
           [0031]      FIG. 7  is an enlarged, fragmentary view of the arrangement of teeth assemblies for the drum teeth assemblies of the array, with mounting plates and threaded fasteners removed for clarity; 
           [0032]      FIG. 8  is an enlarged exploded view of one of the teeth assemblies as used for the drum teeth assemblies, for the first and second cutterbar teeth assemblies, and for the guard teeth assemblies, showing the individual teeth which may be bolted to the drum mounting plates, flanges or ear plates, showing the serrated cutting edges and a plug weld further joining the individual teeth; 
           [0033]      FIG. 9  is an enlarged, front end view of one of the teeth assemblies of  FIG. 8 , showing a flange of a cutterbar in broken lines, and with the mounting bolts and nuts removed for clarity to show the configuration of the teeth assemblies and one of the serrated cutting edges; 
           [0034]      FIG. 10  is an enlarged, elevational view of a cutterbar teeth assembly with the mounting nut and flange shown in broken lines, to show the mounting arrangement of one of the teeth assemblies; 
           [0035]      FIG. 11  is top plan view of a cutterhead drum and shroud similar to that shown in  FIG. 3 , but including a shield mounted along and extending from a top edge of the cutterhead shroud; 
           [0036]      FIG. 12  is an enlarged left top rear perspective view of the cutterhead shown in  FIG. 11 , showing the positioning of the shield in a generally upright orientation and the brackets for adjustably mounting the shield to the cutterhead shroud, and further showing the port through the shroud; 
           [0037]      FIG. 13  is an enlarged right side elevational view of the cutterhead shown in  FIG. 11 , showing the positioning of the shield relative to the top front edge of the shroud and the rotating drum; and 
           [0038]      FIG. 14  is an enlarged top left front perspective view of a section of the cutterhead shown in  FIG. 11 , showing in detail the relative positioning of cutterhead teeth assemblies, and one of the pivot mounts which permit adjustment of the shield relative to the cutterhead shroud. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0039]    Referring now to the drawings, a cutterhead  10  in accordance with the present invention broadly includes a rotatably mounted drum  12 , a shroud  14 , drum mounting structure  16  and motor  18 . The cutterhead  10  is used in conjunction with a dredge  20  which includes engine compartment  22 , pontoon hull  24 , deck  25 , cab  26 , and a boom  28  pivotally mounted at the rear of the dredge. As shown in greater detail in  FIG. 2 , the boom  28  carries a pump  30  and pump motor  32  for operating the impeller located within the pump  30  and which receives material from the shroud  14  for delivery through the boom  28  to a remote location. The pump motor  32  and the motor  18  are both preferably hydraulically driven by hydraulic fluid under pressure by power supplied by a hydraulic pump in the engine compartment  22  and delivered through hydraulic conduits  34  (to pump motor),  36  and  38  (to motor  18 ). 
         [0040]    In greater detail, the drum  12  is substantially cylindrical and presents a smooth outer surface  40  with the exception of an array  42  of spirally oriented, convergent patterned, radially projecting drum teeth assemblies  44 . The drum  12  is preferably made of mild steel which provides sufficient strength and durability, while the teeth assemblies  44  are hardened to cut aquatic vegetation encountered during dredging while at the same time withstanding impacts from rocks or other debris which may have settled into the sediment or other deposit to be dredged. 
         [0041]    Turning next to  FIGS. 3 and 4 , the drum  12  includes a center section  46  and a pair of end sections  48  and  50 , each including a pair of end halves  52  and  54 . The center section includes an end wall  56  at each longitudinal end, and a plurality of circumferentially spaced mounting flanges  58  which project longitudinally at each end and include nuts  60  welded thereto for receiving bolts which project through the surfaces of the end halves  52  and  54  and are threaded into the nuts. This enables easy removal of the end halves  52  and  54  for access to the drum mounting structure  16 . As is easily seen in  FIGS. 3 and 4 , the array  42  extends through the end sections  48  and  50  whereby the spiral orientation of the array  42  is continuous from the ends of the drum  12  across the end sections  48  and  50  and into the center section  46 . 
         [0042]    The array  42  includes two convergent helically oriented flights  41  and  43  of mounting plates  62  which are welded to the drum surface  40 . The mounting plates  62  are spirally arrayed as shown in  FIGS. 3 and 4  to provide a toothed cutting surface across virtually the entire width of the drum  12  when teeth assemblies  44  are mounted to the plates  62 . Each of the teeth assemblies  44  is mounted by two bolts into nuts  61  positioned on the opposite sides of the plates  62 , so that every other of the teeth assemblies  44  spans two plates  62 , as best seen in  FIG. 6 . Each of the teeth assemblies  44  has a cutting margin which may include a leading cutting edge  64 , a tip  66 , and a trailing cutting edge  68 , which features are also seen in  FIG. 7 , although the motor  18  is preferably a reversible hydraulic motor which permits clearing of the teeth assemblies  44  by backwards rotation when necessary. In normal rotation of the drum  12 , the array  42  converges to an apex  69  to effectively auger the cut and dredged material toward the center of the drum  12 . 
         [0043]    As best seen in  FIGS. 3 ,  5  and  6 , the shroud  14  includes a pair of opposed end panels  68  and  70  for supporting drum mounting structure  16 , upper and lower walls  72  and  74  respectively, angled walls  76  and  78  and back wall  80 , all preferably of steel plate. The back wall  80  presents a facing  82  which extends normally above the upper wall  72 . A port  84  is centrally located in the back wall and presents a plurality of surrounding holes to facilitate mounting to the pump  30 . 
         [0044]    Stationary cutterbars  86  and  88  are mounted to the upper and lower walls  72  and  74  respectively, and are best seen in  FIGS. 5 and 6 . Each cutter bar  86  and  88  presents a plurality of cutterbar teeth assemblies  90  which are configured substantially the same as the teeth assemblies  44  which are parts of the array  42 , and mount to upstanding flanges  92  on each stationary cutterbar  86 ,  88  by bolts threaded onto nuts on the other side of the flanges. The spacing of the flanges  92  of each cutterbar  86  and  88 , and therefore the teeth assemblies  90  carried thereby, is staggered whereby the cutterbar teeth assemblies  90  on cutterbar  86  are not vertically aligned with the corresponding cutterbar teeth assemblies  90  on cutterbar  88 . However, the alignment of the cutterbar teeth assemblies  90  corresponds to gaps  94  between the teeth assemblies  44  of the array  42  on the drum  12 , whereby the slight transverse space between the teeth assemblies  44  receives the substantially fore and aft aligned teeth assemblies  90  of the stationary cutterbars  86  and  88 , with the distance between the drum teeth assemblies  44  and the cutterbar teeth assemblies  90  being preferably about ½″ at the closest point of approach to yield good cleaning and tearing action during rotation. In order to facilitate access to the teeth assemblies  90  for maintenance by providing adequate spacing therebetween, not every gap  94  receives one of the teeth assemblies  90  therebetween, but in the preferred embodiment shown, approximately two out of every three gaps  94  will receive a teeth assembly  90  therebetween to provide a tearing relationship between the teeth assemblies  90  of the cutterbars  86  and  88  and the teeth assemblies  44  for cutting, writhing and rending any vegetation which wraps around the drum or drapes across the teeth assemblies  44  or teeth assemblies  90 . 
         [0045]    The shroud  14  additionally may optionally mount guard teeth assemblies  96  and  98 , which are bolted to ear plates  100  and  102  respectively at each end panel  68  and  70  respectively. The guard teeth assemblies  96  and  98 , as seen in  FIG. 4 , present cutting edges  104  which are pointed outwardly relative to the axis of rotation A of the drum  12 , and are positioned radially outside the drum mounting structure  16  but radially interior to the end sections  48  and  50 . The guard teeth assemblies  96  and  98 , when employed, may be located proximate the end panels of the shroud to cut vegetation which passes through the space defined between the longitudinal margins  106  and  108  of the drum and the end panels  68  and  70  respectively of the shroud  14  before such vegetation passes longitudinally toward to the center of the drum  12  and wraps around the drum mounting structure  16 . 
         [0046]    As best seen in  FIG. 5 , the drum mounting structure  16  is largely conventional and includes hub  110  which permits rotation between the shroud  14  and the drum  12 . The hub  110  is bolted to the end panel  70  and to the end wall  56  at one end of the center section of the drum  12 . Another hub  112  rigidly connects the motor  18  and the center section  46 , and is bolted to the end wall  56  and the motor  18 . In turn, the motor  18  is rigidly bolted to the end panel  68  and is preferably a reversible hydraulic motor which enables reversing of the drum  12  to clear any rocks, stumps or other large objects stuck between teeth assemblies  44  or teeth assemblies  90 . The motor  18  is driven by hydraulic fluid supplied under pressure and delivered through conduits  36  and  38 . Hubs  110  and  112 , as well as guard teeth assemblies  96  and  98  are located in open-ended cavities  114  and  116  positioned outboard of end walls  56  and radially interior to end sections  48  and  50 . 
         [0047]    The drum teeth assemblies  44 , the cutterhead teeth assemblies  90  and the guard teeth assemblies  96  and  98  are shown in greater detail in  FIGS. 7 ,  8 ,  9  and  10 . Each of the teeth assemblies  44 ,  90 ,  96  and  98  may include a pair of individual teeth  118  which beneficially are common to each of the teeth assemblies  44 ,  90 ,  96  and  98  to reduce the number of parts which must be maintained in inventory. Thus, the exploded view of  FIG. 8  shows the same individual teeth  118  which are used in each of the teeth assemblies  44 ,  90 ,  96  and  98  and which are mounted to the respective mounting plates  62 , flanges  92 , and ear plates  100 ,  102 . The individual teeth  118  may be provided with a substantially flat back side  120  and a raised or somewhat convex front side  122 , and have a point  124  upon which converge two serrated cutting edges  126  and  128 . Holes  130  are provided on each of the individual teeth  118  and aligned in registry when combined in back-to-back relationship in the teeth assemblies to permit bolts  136  to pass therethrough for mounting purposes. Thus, when the individual teeth  118  are placed back to back and secured together by threaded fasteners such as bolts and nuts or the like, they may comprise teeth assemblies  44 ,  90 ,  96  and  98 , which assemblies each may have a leading cutting edge  64 , a tip  66 , and a trailing cutting edge  68 . As may be seen in  FIGS. 7 through 10 , and especially in the exploded view  FIG. 8 , the individual teeth  118  of each of the teeth assemblies are plug welded together. A hole  132  is provided, for example by drilling, at least part way (e.g., approximately ¼ inch) through approximately the center of one or both of the teeth  118 . The teeth  118  so drilled are placed in back to back relationship with their holes  130  in registry, and then plug welded such that a plug  134  is positioned and secured in the hole  132 , thereby further securedly fixing the teeth  118  in the teeth assemblies  44 ,  90 ,  96  and  98 . By this arrangement and configuration involving back-to-back placement of the individual teeth  118  with the raised or convex surface exteriors facing outwardly and the flat back surfaces  120  together, the teeth assemblies  44 ,  90 ,  96  and  98  are not only substantially strengthened against bending or breakage, but vegetation may also pass over the teeth assemblies after being more effectively cut by the serrated leading  64  or trailing  68  cutting edges. Moreover, it has been discovered that the use of plug welding to connect the individual teeth  118  of the teeth assemblies provides exceptional and surprising strength, providing lamination in the teeth assemblies so that the teeth assemblies last longer and avoid bending. Thus, such plug welded teeth assemblies  44 ,  90 ,  96  and  98  significantly enhance productivity during weed harvesting by reducing downtime which might otherwise be required to repair the cutterhead and replace broken or bent teeth or teeth assemblies. 
         [0048]    Turning now to  FIGS. 11-14 , the cutterhead  10  may be provided with a shield  136  which is preferably adjustably mounted to the shroud  14  along or adjacent a top front edge  138  of the shroud  14 . The shield  136  may preferably extend the width of the shroud  14 , and may have a height which may be greater than the radius of the cylindrical drum  12  and most preferably greater than the radial distance from the axis of rotation of the drum  12  to the point  124  of the teeth  118  on the drum  12 . The teeth may be either back to back teeth  118  as shown and described with reference to  FIGS. 6-10  as teeth assemblies  44 ,  90 ,  96  and  98 , or alternatively relatively thick individual teeth  118 A as shown in  FIG. 14 , having serrated leading and trailing cutting edges. 
         [0049]    The shield  136  may be fabricated of metal, such as aluminum or steel, and preferably presents a relatively flat, planar front panel  140  which thus resists collection of liquid and cut vegetation thereon, but rather deflects any such liquid or vegetation contacting the front panel  140 . The shield  136  preferably includes a proximate margin  142 , a remote margin  144 , and left and right side margins  146  and  148  which are angled relative to the front panel  140  to provide rigidity and reinforcement. The remote margin  144  and side margins  146  and  148  may extend rearwardly of the front panel  140  and be angled approximately 90° from the front panel to enhance strength and rigidity, while the proximate margin  142  may be angled approximately 45° from the front panel to both enhance the strength and the range of pivotal adjustment of the shield  136  relative to the shroud  14 . An inner proximate wall  150  oriented substantially perpendicular to the front panel  140  encloses the space within the proximate margin  142  to resist collection of cut vegetation and water therein. A plurality of tabs  152  extend from the proximate margin  142  and are laterally spaced along the width of the shield  136 . The tabs  152  are positioned adjacent laterally spaced reinforcing bars  155  which preferably extend between the remote margin  144  and the inner proximate wall  150 . The tabs  152  may have holes into which couplers  154  such as pivot pins, bolts or other threaded fasteners are received to pivotally mount the shield  136  to the shroud  14 . 
         [0050]    In order to most advantageously mount the shield  136 , a mounting bar  156  may extend along the top front edge  138  of the shroud  14 . The mounting bar  156  may carry a plurality of generally forwardly and/or upwardly extending mounting flanges  158  which have holes complementally sized and positioned relative to the holes in the tabs  152  for receiving the couplers  154  therethrough. Thus, the shield may swing about the couplers  154  for positioning on one of a plurality of preselected desired orientations. 
         [0051]    A plane P extends forwardly from the upper wall  72  of the shroud  14 , which in  FIG. 13  is generally flat, and thus the plane lies along the flat upper surface of the upper wall  72 . Brackets  160  may be laterally spaced along the upper wall  72  of the shroud  14 . The brackets  160  are generally oriented fore-and-aft along upper wall  72 , and are preferably positioned in planes generally perpendicular to both plane P and the axis A of rotation of the drum  12 . Each of the brackets  160  may include a series of fore-and-aft spaced holes  162 , four such holes  162  being illustrated on each of the brackets  160  in the drawing of  FIGS. 12 and 13 . The holes  162  are positioned and configured to mount a proximate end  164  of struts  166  by the use of couplers  154 , such that each of the holes  162  (i.e.,  162 A,  162 B,  162 C and  162 D) on a bracket  160  provides an alternate mounting location. The struts  166  are also provided with a remote end  168 , which is pivotally mounted by couplers  154  to a hole in a respective one of the reinforcing bars  155 . By removing the couplers  154  from the proximate ends  164  of the struts  166  and repositioning the holes through proximate ends  164  of the struts  166  in alignment with a different one of the holes  162  of a bracket  160  and then reattaching the couplers  154 , the angle of the front panel  140  relative to the plane P along the surface of the upper wall  72  may be adjusted. For example,  FIG. 13  shows the proximate ends  164  of struts  166  attached in the rearmost hole  162 D of the bracket  160 , whereby the front panel  140  of the shield  136  is oriented at about 70° from the plane P. However, by removing the couplers  154 , pivoting the shield forwardly (clockwise as depicted in  FIG. 13 ) about a pivot axis defined by the holes in the tabs  152  and the couplers  154  passing therethrough, the angle may be adjusted and maintained by reattaching the proximate ends  164  of the struts  166  to the brackets  160  by securing the couplers  154  through either hole  162 C,  162 B or  162 A. When the frontmost hole  162 A is used, the angle may be reduced to about 10°. By lengthening the brackets  160  or providing additional holes  162 , additional preselected angles for pivoting the shield  136  may be provided. 
         [0052]    In preparation for use of the cutterhead  10 , the shroud  14  is bolted to the pump  30 , the conduits  36  and  38  are connected to the hydraulic pump in the engine housing, and the boom  28  is lowered by the operator in the cab to begin dredging. Any aquatic vegetation encountered during dredging is severed and cut by the cutting action of the teeth assemblies  44  while the drum  12  rotates, and further enhanced by the tearing action between the cutterhead teeth assemblies  90  mounted on the stationary cutterbars when teeth  44  pass thereby. In addition, when guard teeth assemblies  96  and  98  are employed, additional cutting action is presented for cutting or tearing vegetation which passes between the longitudinal margins  106  and  108  of the drum and the end panels  68  and  70  of the shroud  14 , preventing such vegetation from passing longitudinally toward the center of the drum  12  and wrapping around the drum mounting structure  16 . The teeth assemblies  44  present a cutting surface which may extend transversely across substantially the entire length of the drum  12 , and thus any vegetation passing across the path of the drum  12  will be engaged by one or more of the teeth assemblies  44 . As noted, except for the teeth assemblies  44 , the drum  12  presents a substantially smooth surface which inhibits the ability of any vegetation to cling to the drum and become draped across it, thereby accumulating and fouling the cutterhead  10 . 
         [0053]    The array  42  of teeth assemblies  44  acts further as an auger to move any dredged sediment and cut vegetation to the center of the drum  12  and thus immediately proximate the port  84  for passage into the pump  30 . The cutterhead  10  chops the vegetation into small enough pieces to avoid jamming the pump  30 , and thus the cut vegetation and the sediment or other deposits can be effectively dredged. Many types of aquatic vegetation including floating plants like hyacinth, submerged vegetation such as milfoil and hydrilla, and emergent vegetation such as cattail and small willows can be cut and removed using the cutterhead  10  hereof, as well as aquatic plants sometimes called tussiks. As in conventional dredging practice, the boom  28  is raised or lowered by a winch mounted on the dredge  20  to engage the vegetation and sediment or other deposits to the desired depth, and the dredge  20  may be self-powered or positioned by shore-anchored cables to direct the cutterhead  10  laterally into position. The angle of the shield  136  relative to the plane P of the top wall  72  of the cutterhead shroud  14  may be adjusted as desired according to whether the cutterhead is to be operated at a depth or along the surface of the body of water in which the vegetation to be harvested is located. The shield  136  may also be adjusted as desired with respect to its relative orientation to the top wall  72  based on the type of vegetation being cut and how the vegetation may thus most effectively be fed into the shroud  14 . 
         [0054]    Although preferred forms of the invention have been described above, it is to be recognized that such disclosure is by way of 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. 
         [0055]    The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of their invention as pertains to any apparatus not materially departing from but outside the liberal scope of the invention as set out in the following claims.