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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     The invention relates to improvements in dredges and, in particular, to an improved suction auger head used with a ladder suspended from a barge. 
     PRIOR ART 
     U.S. Pat. No. 5,060,404 discloses a suction auger-type dredge head on a ladder suspended from a barge. The ladder pivots at one end while the opposite free end, carrying the auger or cutter head, is lowered or raised to a depth to reach and work the bottom. The auger is partially surrounded by a shroud having a center section and outer sections pivotal at opposite edges of the center section. One or the other pivoting shroud sections is raised or opened to admit bottom material to the cutting side of the auger depending on the direction the head is being moved. The shroud serves to confine the suction developed by a pump to the zone of the auger. The head can be pivoted on the ladder about an axis displaced from the head to reduce, to some extent, the effect that a change in the ladder angle or inclination has on the attitude of the shroud relative to the bottom surface and cut that the auger is making. 
     SUMMARY OF THE INVENTION 
     The invention provides dredging apparatus with a suction auger head that achieves improved operating efficiency with a novel auger shroud assembly. The shroud assembly has a generally cylindrical arcuate configuration that is formed by a series of arcuate sections. The sections are movable relative to the ladder depending on the depth and direction of travel of the auger head. 
     In the disclosed arrangement, the auger head shroud assembly has a center section lying between oppositely extending forward and rear sections. All of the sections are pivotal, in unison, about an axis coincident with the axis of rotation of the auger. The forward and rear sections are each independently pivotal about a respective axis adjacent its edge proximal to the center shroud. Pivotal shroud assembly movement about the auger axis adjusts for differing depth angles of the ladder. One or the other of the forward and rear sections is pivoted open depending on the direction of movement of the dredge. More specifically, the forward or rear section leading the auger in the direction of movement is pivotally opened while the other section remains closed adjacent the periphery of the auger. 
     The disclosed shroud construction enables the shroud to closely hug the bottom surface immediately ahead of the auger in either forward or reverse directions. Consequently, turbidity is minimized at the auger head and, as a result, high dredging efficiency is achieved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a dredge barge embodying the present invention; 
     FIG. 2 is a somewhat schematic side elevational view of a lower section of the dredge ladder and suction auger head of the invention; 
     FIG. 3 is a somewhat schematic plan view of the lower section of the ladder and the suction auger head; 
     FIG. 4 is a schematic side elevational view of the suction auger head in a shallow forward digging mode; 
     FIG. 5 is a view similar to FIG. 4 illustrating the suction auger head in a shallow reverse digging mode; 
     FIG. 6 is a schematic side elevational view of the suction auger head in a deep forward digging mode; 
     FIG. 7 is a view similar to FIG. 6 with the suction auger head in a deep reverse digging mode; and 
     FIG. 8 is a schematic exploded perspective view of a shroud assembly of the suction auger head. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and, in particular, to FIG. 1, a dredge barge  10  of generally known construction has a lever room or cabin  11  and an engine or power plant  12  for driving a hydraulic pump for operating various hydraulic motors and actuators on the barge. Traverse cable  13  extends fore and aft of the barge  10  for pulling the barge forwardly or rearwardly via a hydraulic barge mounted winch as is known in the art. A hull  14  of the barge  10  includes a pair of pontoons  16  that straddle a dredge ladder or boom  17 . The ladder  17  is shown in a relatively shallow dredging position in solid line in FIG.  1  and in a relatively deep dredging position in phantom in FIG.  1 . The ladder can be raised above the solid line position of FIG. 1 to a point where it is entirely above the bottom of the hull  14 . 
     One end  18  of the ladder  17  is pivotally supported on the hull with trunnions  19 . An opposite end of the ladder carries a suction auger dredge head  21 . The angular position of the ladder  17  and, consequently, the depth of the dredge head  21  is controlled by a hydraulic piston and cylinder actuator  22 . The actuator  22  is carried on trunnions fixed to the deck of the barge and is coupled by a clevice to a bracket  24  fixed to the ladder  17 . 
     The major length of the ladder  17 , in the illustrated construction, is fabricated from a cylindrical steel tube that is mitered at a plane or joint  26  such that a lower relatively short section  27  of the ladder drops down in a vertical plane at an obtuse angle with respect to an upper longer section  28 . 
     With particular reference to FIGS. 2 and 3, the free lower section  27  of the ladder  17  includes a pair of tubular arms  29  diverging at oblique angles to the axis of this lower section  27 . The arms  29  and lower ladder section have longitudinal axes that are coplanar. The arms  29  are welded to the wall of the lower ladder section  27 . Ends of the arms  29  distal from the lower ladder section are welded to respective parallel plates  31  that extend forwardly beyond the tubular main body of the lower ladder section  27 . 
     An elongated auger  36  extends between the plates  31 . The auger comprises left and right-hand helical sheet metal screw sections  37 ,  38  respectively, and a tubular shaft  39  about which the screws  37 ,  38  are wrapped and welded. The sheet metal screws  37 ,  38  provide peripheral cutting edges  41  and urge bottom material axially towards the longitudinal or lengthwise center of the auger head  21 . The auger  36  is rotationally supported by a bearing  42  on the starboard side plate  31  and by a hydraulic motor  43  at the opposite or port side plate  31 . 
     A shroud assembly  46  covers a major portion of the circumference of the auger assembly  36 . The shroud assembly  46  includes front, center and rear sections  47 - 49  respectively. Each of the sections  47 - 49  is fabricated of sheet steel rolled or otherwise formed into cylindrical shell segments with an inside radius moderately but not substantially larger than the outside diameter of the auger screws  37 ,  38  to provide a practical working clearance therewith. The rear shroud section  49 , as most clearly shown in FIG. 8, has two separate parts, one at the right (starboard) and one at the left (port). The front and rear shroud sections  47 ,  49  are each pivoted with respect to the center section  48 . Piano hinge-like structures  51 ,  52  coupling the front and rear sections to the center section  48 , respectively have a hinge or pivot center  53 ,  54  adjacent the proximate longitudinal edges of each of these sections and the respective proximate longitudinal edges of the center section. 
     The center shroud section  48  is bolted or otherwise fixed to end plates  56 , one at each of its ends. The end plates  56  have large circular holes  57  that are concentric with the center of curvature of the center shroud section. The end plates  56  are mounted on annular discs or tracks  58  fixed to the inside faces of the plates  31 . The holes  57  and tracks  58  are dimensioned to enable the end plates  56  to pivot freely on the tracks thereby allowing the center shroud section to pivot about the axis of the auger  36 . The angular position of the center shroud section  48  about the auger  36  relative to the ladder  17  is selectively adjustable by operation of a pair of hydraulic piston and cylinder actuators  61 . One end of each actuator  61  is connected to a bracket  62  fixed on the center shroud section  48  and the other end is connected to a bracket  63  fixed to an associated arm  29  of the lower ladder section  27 . 
     The position of the front shroud section  47  about the hinge axis  53  relative to the center shroud section  48  is selectively adjustable by operation of a pair of hydraulic piston and cylinder actuators  64  connected at one end to an associated bracket  62  on the center shroud section  48  and at the other end to a bracket  66  fixed on the front shroud section. Similarly, the position of each of the rear shroud section parts  49  about the hinge axis  54  relative to the center shroud section  48  is selectively adjustable by operation of an associated hydraulic piston and cylinder actuator  67  connected at one end to a respective bracket  62  and at the other end connected to a bracket  68  on the associated rear shroud section part  49 . 
     The rear shroud section parts  49  are separated by a gap  71  adjacent the mid-length of the auger  36 . A notch  72  is cut in the rear edge of the center shroud section  48  and forms an extension of the gap  71  in the circumferential direction with reference to the periphery of the auger. The opening in the wall of the shroud assembly  46  formed by the gap  71  and notch  72  is covered by a fixed inlet shroud  73 . The fixed inlet shroud  73  is a weldment of steel sheet stock that includes an arcuate sheet  74  having a radius of curvature to fit over the outside surface of the shell or wall of the center shroud section  48 . Additionally, the fixed inlet shroud  73  includes a steel tube that fits into the wall opening of the gap  71  and covers the notch  72 . 
     Mounted on the lower ladder section  27  closely adjacent the auger  36  is a suction pump  77 . The pump  77  is driven by a hydraulic motor (not shown) or other suitable means mounted within the lower ladder section  27  which motor is powered by the hydraulic pump operated by the power plant  12  in a conventional manner. 
     An inlet  82  of the pump is coupled by the fixed inlet shroud tube  76  so that the suction of the pump is applied through the shroud opening of the gap and notch  71 ,  72  to the working space of the auger surrounded by the shroud assembly  46 . A flexible duct or pipe  79  is connected to an outlet  81  of the suction pump  77  and carries material discharged by the suction pump to a remote location where it is received by a barge or other collection point. 
     In operation, the lower or free end section  27  of the ladder  17  is lowered with the actuator  22  to a depth preferably where a large fraction of the height of the auger  36  can work on the bottom. FIGS. 4 and 5 show forward and reverse dredging action where the bottom is at a relatively shallow depth. FIGS. 6 and 7 similarly show forward and rearward dredging where the bottom is relatively deep. 
     In the shallow dredging condition such as depicted in FIGS. 4 and 5, the actuators  61  have their piston rods extended to rotate the shroud assembly  46  about the axis of the auger  36  clockwise relative to the ladder  17 . Typically, this is done to position the center shroud section  48  with an attitude where the front and rear hinge axes  53 ,  54  are generally in a common horizontal plane. In the forward digging operation, the front shroud section  47  is opened so that a forward or free edge  86  is at least as elevated as its rear hinged edge and preferably is slightly higher. At the same time, the actuators  67  hold the rear shroud section parts closed so that they are close to the periphery of the auger  36 . 
     In the reverse shallow depth digging action, the center section  48  remains in the attitude where the hinge axes  53 ,  54  are at or near a common plane but the opened and closed positions of the front and rear shroud sections  47 ,  49  are reversed by selective operation of their respective actuators  64  and  67 . 
     With reference to FIGS. 6 and 7 showing deep dredging operation, the operational strategy is similar. The actuators  61  retract their piston rods to rotate the shroud assembly  46  counterclockwise relative to the ladder  17  again producing an attitude of the shroud assembly where the front and rear hinge axes  53 ,  54  are generally in a common horizontal plane. In the forward direction, the front shroud section  47  is fully opened and the rear shroud section  49  is fully closed. In the reverse direction, these positions are reversed by selective operation of their respective actuators  64 ,  67 . 
     A study of FIGS. 4-7 shows that in all the illustrated conditions of digging, the leading shroud section, i.e. the front shroud section  47  in forward operation or the rear shroud section  49  in reverse operation closely hover over the bottom surface. The same is true of the trailing shroud section, i.e. the rear shroud section  49  in the forward operation and the front shroud section  47  in the rearward operation. This close fitting of the leading and trailing shroud sections to the profile of the bottom as it is being dredged into the auger by the center section and the closed trailing one of the front or rear shroud sections substantially reduces turbidity in the flow of material being worked by the auger  36  and suctioned by the pump  77 . This reduction of turbidity produces a corresponding increase in efficiency. The articulation afforded by the front and rear shroud sections  47 ,  49  by their hinge or pivot mounting to the center section  48  and the pivotal mounting of the center section to the lower ladder section  27  produced by pivoting of the end plates  56  on the tracks  58  affords a suction auger dredge head that is essentially as efficient in the rearward dredging direction as in the forward dredging direction. 
     As shown, the center shroud section  48  wraps about the periphery of the auger through an angle of at least 90° while each of the front and rear shroud sections  47  and  49  wrap around the auger  36 , when closed, at least about 45°. When either the front or rear shroud section is closed, there is a shrouding effect directly around the auger of preferably at least about 180°. FIGS. 4-7 illustrate relatively full cuts by the auger; where it is desired to make less than a full cut the forward or rear shroud, whichever is leading, is opened by the respective actuators to a less than full open position. 
     It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.

Summary:
A dredge supporting a pivotal ladder with a suction auger on its free end. A shroud assembly including front, center and rear sections surrounds a large portion of the periphery of the auger. The shroud assembly is pivotal about the axis of the auger and the front and rear sections are each independently pivotal relative to the center section so that the center section can be maintained at a relatively constant attitude independent of the inclination of the ladder and only a leading one of the front and rear sections, depending on the direction of movement of the dredge, is necessarily opened while the trailing section can remain closed adjacent to the auger. The articulation of the several shroud sections enables the suction auger head to operate in both directions with reduced turbidity and, therefore, increased efficiency.