Title:
Automatic dredge system and method of operation
Kind Code:
A1


Abstract:
A method for automatically operating a dredge having a swingable and elevatable ladder with a cutting head having a speed comprising the steps of: providing an automatic swing sequence; providing a cutter head rate control; and providing an automatic ladder raise control sequences. A dredge in which this method is used is also disclosed.



Inventors:
Thomas, David F. (Danville, OH, US)
Application Number:
10/364121
Publication Date:
08/21/2003
Filing Date:
02/11/2003
Assignee:
THOMAS DAVID F.
Primary Class:
International Classes:
E02F1/00; E02F3/92; (IPC1-7): E02F1/00
View Patent Images:
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Primary Examiner:
PEZZUTO, ROBERT ERIC
Attorney, Agent or Firm:
SAND, SEBOLT & WERNOW CO., LPA (CANTON, OH, US)
Claims:
1. A method for automatically operating a dredge having a swingable and elevatable ladder with a cutter head having a speed comprising the steps of: (a) providing an automatic swing sequence for the ladder; (b) providing a rate control for the cutter head; and (c) providing an automatic raise control sequence for the ladder.

2. The method of claim 1 wherein step (a) includes the further step of providing an automatic swing rate control.

3. The method of claim 2 wherein step (a) includes the further step of providing an automatic swing rate speed decrease control.

4. The method of claim 1 wherein step (b) includes the further step of providing an automatic speed decrease control sequence for the cutter head.

5. The method of claim 1 wherein step (c) includes the further step of providing swing control sequence for the ladder.

6. The method of claim 1 including the step of automatically measuring the pressure at the cutter head.

7. The method of claim 6 including the steps of providing a material discharge line operatively connected to the cutter head and measuring the pressure of the discharge line.

8. A method for automatically operating a dredge having a swingable and elevatable ladder with a cutting head having a speed comprising the steps of: (a) providing an automatic swing sequence for the ladder, wherein said automatic swing sequence includes an automatic swing rate control and an automatic swing rate speed decrease control; (b) providing a cutter head rate control wherein said cutter head rate control includes an automatic head speed decrease control sequence which includes the further step of measuring the pressure at the cutter head; (c) providing an automatic ladder raise control sequence; and (d) providing a material discharge line including the step of measuring pressure at said discharge line.

9. The method of claim 8 including the step of measuring the speed of the material moving through the discharge line.

10. An automatic dredge comprising: a swingable and elevatable ladder; a cutter head mounted on the ladder; means for providing an automatic swing sequence for the ladder; means for providing a rate control for the cutter head; and means for providing an automatic raise control sequences for the ladder.

11. The dredge of claim 10 further comprising an automatic swing rate control for the ladder.

12. The dredge of claim 11 further comprising an automatic swing rate speed decrease control for the ladder.

13. The dredge of claim 10 further comprising an automatic speed decrease control sequence for the cutter head.

14. The dredge of claim 10 further comprising a material discharge line communicating with the cutter head; and a valve for admitting additional water into the discharge line.

15. The dredge of claim 14 wherein the valve is a butterfly valve.

16. The dredge of claim 10 further comprising a means for measuring pressure at the cutter head.

17. The dredge of claim 16 further comprising a material discharge line operatively communicating with the cutter head, and a means for measuring pressure at said discharge line.

18. The dredge of claim 10 further comprising a means for measuring line speed.

19. An automatic dredge comprising: a swingable and elevatable ladder; a cutter head mounted on the ladder; means for providing an automatic swing sequence for the ladder including an automatic swing rate control and an automatic swing rate decrease control; means for providing a speed control for the cutter head including an automatic speed decrease control; means for measuring pressure at the cutter head; means for providing an automatic ladder raise control sequence; and a discharge line and a means for measuring pressure at said discharge line.

20. The dredge of claim 19 further comprising means for measuring discharge line speed.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from U.S. Provisional Patent Application Serial No. 60/357,557, filed Feb. 15, 2002, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The present application relates to excavation and more particularly to excavation beneath a body of water. Still more particularly the present invention relates to dredge systems with means to control dredge operations in response to a sensed condition.

[0004] 2. Background Information

[0005] One manner of obtaining sand and gravel for subsequent use in various construction projects is by dredging these materials from beneath and adjacent to bodies of water. A barge or boat containing dredging equipment is anchored in a body of water generally closely adjacent the bank. A boom or ladder containing a cutter head and suction port or inlet is lowered into position, and an operator, by checking various gauges and by detection of vibrations, sound and feel, controls cutter speed, suction force, movement of the boom and other variables to dislodge the sand and gravel, and for transporting the sand and gravel through a suction passage in the boom and then through a discharge pipe which deposits the collected materials on shore or into an adjacent barge for subsequent processing.

[0006] The effectiveness of this equipment and mode of operation depends largely upon the experience and skill of the dredge operator. It requires the operator to devote his entire time and attention to controlling the speed of the cutter, amount of vacuum on the suction inlet, material discharge flow and pressure, and swing rate of the boom. This becomes very fatiguing on the operator which may effect the efficiency of the dredging. Likewise, it makes it difficult to maintain a constant flow of sand and gravel to the processing plant located on the adjacent bank or to the associated collection means.

[0007] The following prior art patents show a number of ways for controlling the operation of dredging systems.

[0008] U.S. Pat. No. 4,523,255 discloses a pressure displacement dredging system capable of operation, without surging, over a wide depth range and under varying bottom conditions. It comprises a submersible dredging head including at least three pressure vessels each having a material intake port and a material discharge port with appropriate check valves, each having an inlet port for air or other operating fluid connected to a high pressure fluid source through an inlet valve, each having an inlet portion for air or other operating fluid connected to a high pressure fluid source through an inlet valve, and each having an operating fluid exhaust port vented to the atmosphere through an exhaust valve. The system provides cycle control means actuated by low level sensors in each pressure vessel which actuates the vessels between discharge and filling phases in a predetermined closed sequence. When the level of material in a first discharging vessel drops below the low level sensor the cycle control opens the inlet valve and closes the exhaust valve for the next vessel in the sequence to initiate the pressure displacement discharge of material from that next vessel, and thereafter closes the inlet valve and opens the exhaust valve of the first vessel so that the first vessel fills by pressure displacement. The sequence is such that each pressure vessel is full before discharge of that vessel is initiated. One modification of the system provides a vacuum assist for dredging in extremely shallow conditions.

[0009] U.S. Pat. No. 4,351,122 discloses a dredge with a drag pipe consisting of a number of pipe sections interconnected by hinged joints, whereby drag lines are connected to the hinged joints and to the front and rear ends of the drag pipe. A rotatably supported front end of the drag pipe is guided into vertical guiding elements at the side wall of the ship and the rear end carries the drag head. The dredge contains for each drag line, a separate winch controlled by an electronic control unit for automatically moving the drag pipe outboard, and for lowering and rising the drag pipe and moving the drag pipe inboard. During the whole dredge operation from the outboard movement of the drag pipe until the inboard movement thereof, the unwound drag line length of each winch is measured, whereby an electronic control unit determines the position of the drag pipe based on measured drag line lengths at each moment.

[0010] U.S. Pat. No. 4,353,174 discloses a control system for a dredging device which includes a submersible pump having one or more chambers. Each chamber defines an air port through which air can be delivered to and exhausted from the chamber. A material discharge port is provided for discharging liquid and solid material from the chamber, and a chamber suction port admits liquid and solid material into and from the chamber. Air control valves are provided for alternately exhausting air from each chamber to admit material to the chamber through the suction port and for delivering air to each chamber to discharge material from the chamber through the discharge port. The control system operates these air control valves in accordance with a selectable timed cycle to achieve optimum efficiency in the dredging operation.

[0011] U.S. Pat. No. 4,374,420 discloses a method of dredging to a desired profile contour with a cutting dredger. This involves the operation of a cutting assembly and cutting tools which describe a predetermined cutting envelope, and swinging the cutting assembly while the dredger is anchored at a known point. The known point is established by means of land-based radio beacons and an aerial aboard the dredger. The dredger is anchored at the known point while the longitudinal axis of the dredger is aligned or substantially aligned with the longitudinal axis of the desired profile contour. As the dredger is swung with the cutting tools engaging the material to be dredged, the location of geometric points of the dredger assembly are repetitively calculated with respect to the coordinate system of the desired profile contour, taking into account various angular relationships between and among such points and by taking into account motions of the dredger as affected by wave and/or tide actions. The swinging is terminated when the cutting point on the predetermined cutting envelope closely approaches the desired profile contour.

[0012] U.S. Pat. No. 4,387,519 discloses a method for controlling the position of the suction head of a dredge in relation to the sludge layer on the bottom of a waterway. Acoustic pulses are transmitted from the suction head from the dredge to the bottom. The reflected pulses are received and the time difference between the transmitting and the receiving moment is determined as well as the energy difference between the transmitted and received pulses. Based on these differences the configuration and composition of the sludge layers, as well as the preferred position of the suction head in relation to said sludge, is determined. Thereafter, the system for controlling the position of the suction head is operated to bring the suction head into the most favorable position.

[0013] U.S. Pat. No. 4,407,420 discloses a ship with one or more derricks, and in particular a dredge having at least one derrick for handling the suction pipe. The derrick can be moved between an inboard position and a vertical position. The derrick has guiding tracks for a crane jib which tracks in the vertical position of the derrick with guiding tracks inside the profile of the side wall of the ship. The cable for controlling the jib is protected by a channel inside the profile of the ship side wall between the latter guiding tracks. The guiding tracks have upper and lower stops for controlling the movements of the crane jib, which jib is pivotable about a horizontal axis between a position perpendicular to the derrick and a downwardly directed position.

[0014] U.S. Pat. No. 4,999,934 discloses a floating dredge and hydraulic dredging apparatus for mining underwater mineral bearing deposits. The dredge includes an overburden excavator and an ore excavator mounted to a pontoon for removing overburden and ore material, respectively. Processors on the pontoon receive material from the excavators. Dredging control components coordinate the operation of the ore and overburden excavators to efficiently remove and mine the desired material.

[0015] U.S. Pat. No. 5,421,105 discloses a dredging apparatus for dredging waterways containing sediment. The apparatus includes a hood having a passage for water and sediment to enter the hood under the influence of a submersible dredge pump apparatus. The dredge pump apparatus includes an inlet line having an inlet opening positioned in the passage of the hood, and an outlet line which communicates with the inlet line and extends exteriorly to a spoil collection area. A dredge pump draws water and sediment from within the passage into the inlet opening and through the inlet and outlet lines. To prevent clogging of the inlet line by sediment and to ensure a continuous dredging operation, replacement water is introduced adjacent to the inlet opening from a water source in response to sensed pressure variations in the inlet line caused by the onset of clogging. A closed dredging circuit is created by using the spoil collection area as the source of replacement water.

[0016] U.S. Pat. No. 6,263,594 discloses a system for dredging underneath a floating vessel where a conventional dredge cannot reach the location of the material to be dredged. A neutral buoyancy pipe is attached to the end of the suction pipe and acts as an extension of the suction pipe. The horizontal position of the neutral buoyancy pipe is controlled both by the anchoring system which sweeps the dredge back and forth and by a position adjusting system at the forward end of the neutral buoyancy pipe.

[0017] Although these prior art dredging systems and apparatus may perform their intended functions, there still exists the need for improved ways of controlling dredge operation, by relieving the dredge operator from having to continuously monitor and regulate the various controls to achieve the most efficient dredging results and reducing stress on the equipment.

SUMMARY OF THE INVENTION

[0018] The present invention provides a method for automatically operating a dredge having a swingable and elevatable ladder or boom with a cutting head on an extended end of the ladder, wherein the cutting head has an adjustable speed, and wherein the ladder has an adjustable swing rate and a vacuum pick-up for removing the dislodged sand and gravel and transporting it through the ladder and a discharge pipe onto an adjacent shore, barge, conveyor, or the like.

[0019] A further advantage of the present invention is to provide automatic controls for regulating the swing rate of the ladder, pressure of the vacuum pick-up and cutter head speed, to avoid blockage of the vacuum pick-up and discharge pipes, thereby reducing stress on the equipment and reducing the attention required by the operator in controlling the dredging equipment.

[0020] Another advantage of the present invention is the ability to control and keep the swing rate of the ladder constant, as well as maintaining the pick-up vacuum at a desired level depending upon the amount and type of sand and gravel being loosened by the cutting head and transported through the discharge pipe, which enables the equipment to most efficiently dislodge the sand and gravel from an adjacent bank and deliver it on shore for subsequent transportation to a processing plant, with the dredging equipment running at maximum efficiency.

[0021] Still another feature is the automatic movement of the ladder to prevent blockage in the even of an underwater cave-in or upon the cutter head striking a submerged object or obstruction, and in which various audible alarms can be sounded upon certain preset limits being exceeded to prevent damage to the equipment and to provide an immediate signal to the operator that a problem has occurred which must be corrected to maintain the efficient operation of the equipment and results achieved thereby.

[0022] The present invention provides a method and means for automatically operating a dredge having a swingable and elevatable ladder or boom, with a cutting head being maintained at a desired speed, while providing an automatic swing sequence to the ladder and cutter head, and in which the suction pressure of the material pick-up line is measured and maintained as well as the discharge pressure, to prevent blockage in the pick-up line and discharge pipe, while maintaining optimum pressure for the most efficient movement of the sand and gravel from adjacent the cutting head through the ladder and out of the discharge pipe.

[0023] Still another feature of the invention is to provide for the automatic starting and stopping of the equipment for a preset number of operations in combination with a valve, which enables the equipment to detect the presence and/or absence of problems occurring during the dredging operation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] A preferred embodiment of the invention, illustrative of the best mode in which applicant contemplates applying the principles, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims.

[0025] FIG. 1 is a diagrammatic side elevational view of a dredge representing a preferred embodiment of the present invention;

[0026] FIG. 2 is a diagrammatic top plan view of the dredge shown in FIG. 1;

[0027] FIG. 3 is a flow chart showing the automatic start sequence for the dredge of the present invention;

[0028] FIG. 4 is a flow chart showing the automatic swing sequence for the dredge of the present invention;

[0029] FIG. 5 is a flow chart showing the automatic swing rate control for the dredge of the present invention;

[0030] FIG. 6 is a flow chart showing the automatic swing rate speed decrease control for the preferred method of operating the dredge of the present invention;

[0031] FIG. 7 is a flow chart showing the automatic cutter head speed control for the dredge of the present invention;

[0032] FIG. 8 is a flow chart showing the automatic cutter head speed decrease control for operating the dredge of the present invention;

[0033] FIG. 9 is a flow chart showing the ladder automatic raise control for operating the dredge of the present invention; and

[0034] FIG. 10 is a flow chart showing the lower control for the ladder of the dredge of the present invention.

[0035] Similar numerals refer to similar parts throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Referring to FIGS. 1 and 2, a dredge 10 includes a barge 12 with a deck 14 and a hull 16. The dredge also includes a cabin 18 and a boom or ladder 20 which is pivotally connected at 21 to the barge for vertical movement only, as shown by arrows A, FIG. 1. Dredge 10 preferably is anchored to an adjacent bank of the body of water in which dredge 10 is floating by a plurality of aft anchoring cables 38, 42, and 46 which is standard for such dredges. Dredge 10 includes a suction pump 22 which is operatively connected to a suction pipe 23 which extends along ladder 20 for collecting the sand and gravel dislodged from an adjacent bank by a cutter head 25 which is mounted on the distal end of ladder 20. The collected sand and gravel travels through suction pipe 23 and then through a discharge pipe 27 extending along barge 12, for subsequent delivery to a discharge site on the adjacent shore by another discharge pipe 29. This discharged sand and gravel is then transferred to an adjacent or remote processing plant or storage site.

[0037] A forward winch 24 and an associated cable 26 which extends from the winch, is connected to ladder 20 for vertically raising and lowering the ladder. There is a forward starboard winch 30 and an associated forward starboard cable 32 which extends from the winch and connects to a forward starboard cable connector 34 attached to the ladder 20. A forward port winch 31 controls a cable 33 which is operatively connected to ladder 20 at connector 35. Cables 32 and 33 are anchored to the adjacent bank and control the horizontal swing of ladder 20 by pivotally moving barge 12 by selectively shortening and lengthening the cables. This procedure heretofore was done by manual controls instead of the improved automatic control system and method of the present invention.

[0038] On the aft end of the barge 12 there is a port winch 36 controlling cable 38, an aft center winch 40 controlling cable 42, and an aft starboard winch 44 controlling cable 46. These winches and cables are controlled manually and will be operated to reposition the barge before, during, and after dredging as the need arises.

[0039] A vacuum gauge 50 and a line speed gauge 52 which are located within cabin 18 and shown diagrammatically in FIG. 2, are operatively connected to cutter head 25 and discharge or suction pipe 23. Line speed gauge 52 measures the flow rate of the material moving through pipe 23, and subsequently through pipe 27 and discharge line 29, and vacuum gauge 50 measures the vacuum on pump 22. Cutter head 25 ultimately connects to discharge pipe 29 and includes a discharge pressure gauge 56 operatively connected to pipe 29 and located in cabin 18. There is also a swing pressure gauge 58, a ladder pressure gauge 60 and a cutter pressure gauge 62 located within cabin 18 providing the operator with a visual indication of the status of ladder 20 and cutter head 25.

[0040] In accordance with the invention, the control of ladder 20 and cutter head 25, including the flow of the sand, gravel, and debris collected and delivered thereby, is automatic as described below, instead of relying upon the constant monitoring and adjustment by the operator as heretofore required.

[0041] Referring to FIG. 3 the dredge automatic start sequence involves first making a start request as at block 64, afterwhich the determination is made if a first engine is within operating range set points at block 66. This first engine is the hydraulic engine which operates the hydraulic pumps for the various winches described above. Then a determination is made if a second engine is within operating set points of block 66, afterwhich a determination is made if ladder 20 is between swing limits at block 70. This second engine controls suction pump 22 for picking up and subsequently discharging the sand and gravel. If the engines are not within the operating range set points, a determination is made at block 74 to send a message to display at block 72, afterwhich there is an auto sequence stop at block 74. If ladder 20 is within swing limits the dredge auto sequence is enabled at block 76, afterwhich a determination is made if operator intervention is enabled at block 78. If operator intervention is not enabled, there is a start of auto swing control at block 80, start of the auto swing speed control at block 82, start of the auto cutter head control at block 84, and start of the ladder auto position control at block 86.

[0042] Referring to FIG. 4, the dredge automatic sequence begins with ladder 20 at the starboard limit at block 88 and the forward starboard winch out at block 90, afterwhich a determination is made if the forward starboard winch out cycle is complete at block 92, and if so, a determination is made as to whether the auto ladder drop cycle is completed at block 94 and, if it is, it enables forward port winch motion at block 96. If ladder 20 is not at the starboard point limit, a determination is made at block 100 if the ladder is at port limit and, if so, the forward port winch out at block 102 is determined, afterwhich the determination of the forward port winch out cycle is complete at block 104. Determination is then made as to whether the auto ladder drop cycle is complete at block 106, and if so, it enables forward starboard winch motion at block 108. A determination is made if the first swing cycle is complete at block 110 and, if not, the determination is made whether the start of the automatic swing to port at block 112, and if not, the determination whether the start automatic auto swing to starboard is made at block 114, and if not, the operator selects the start direction of ladder swing port to starboard at block 116. This operation automatically lowers the ladder and cutter head a predetermined amount at the end of a swing cycle for the start of another swing cycle.

[0043] Referring to FIG. 5, there is a dredge automatic swing rate control which begins with the load of maximum swing rate speed of 0-55% at block 116. Thereafter a determination is made if the cutter head pressure is above the set point at block 118, and if so, there is a start of the swing winch decrease sequence cycle at block 120. If the cutter head is not above the cutter head pressure set point the swing winch pressure above set point at block 122 is made, and if not, whether discharge pressure above set point is made at block 124, and if not, whether the vacuum differential pressure is above the set point at block 126. The determination is then made if the discharge flow rate is above the set point at block 128, and if not, whether the auto ladder depth adjustment is needed at block 130, and if not, a determination is made as to whether the cutter head is at the speed set point at block 132, and if it is not at the set point the existing swing speed output is held at block 134. If the cutter head is at the speed set point the determination is made whether the swing winch speed is at the set point at block 136 or, if it is not, the swing winch speed is increased to the set point at block 138. This automatically controls the swing rate of the ladder based upon the pressure on the cutter head, the pressure on the swing winches, and the flow rate of the materials moving through the discharge pump. This provides for the most efficient movement of the ladder as it moves through its swing cycle and anticipates system changes.

[0044] FIG. 6 is a more detailed description of block 120 of FIG. 5. The dredge automatic swing rate speed decrease control begins with decreasing swing winch speed at block 140. Next a determination is made if vacuum differential pressures is 0.250 above the set point at block 142, and if it is not, a determination is made if discharge flow is 0.250 below the set point at block 150, and if not, a determination is made whether discharge pressure is 0.250 above the set point at block 152. If any of these pressure conditions do exist, then the slow swing speed is set to ¾ of the set point at block 144, afterwards a determination is made if vacuum differential pressure is 0.500 above the set point at block 146. If it is, the speed of the swing is slowed to ½ of set point at block 148. If vacuum pressure is not above this level, a determination is made if discharge flow is 0.500 below the set point at block 154 and, if not, the determination is made whether discharge pressure is 0.500 above the set point at block 156. After the swing speed is slowed to ½ of the set point, a determination is made at block 156. If the vacuum differential pressure is 1 above the set point at block 158 then the swing speed is slowed to ¼ of the set point at block 160, afterwhich a determination is made if the vacuum differential pressure is 2 above the set point at block 162 and zero is then moved into the swing speed output at block 164 and there is a return to START at block 166. At block 168 a determination is made if the discharge flow is 0.75 below the set point and if not, a determination is made if there is discharge pressure 1 above the set point at block 170. A determination is also made if there is a discharge flow 1 below set point at block 172, afterwhich a determination is made if the discharge pressure is 2 above the set point at block 174, and if not, a determination is made whether the swing winch pressure is above the maximum set point at block 176.

[0045] Referring to FIG. 7, dredge automatic cutter head speed rate control is carried out by first loading maximum cutter head rate speed from 0-100% at block 178. A determination is then made at block 180 as to whether the cutter head pressure is above the set point and if it is, the cutter head decrease sequence is started at block 182. If it is not, a determination is made if the swing winch pressure is above the set point and if not, a determination is made as to whether the discharge pressure is at the set point at block 186. If not, a determination is made at block 188 if the vacuum differential pressure is above the set point, and if not, whether discharge flow rates are above the set point at block 190. The determination is made at block 192 if the cutter head is above the set point, and if not, there is an increase of cutter head speed to the set point at block 194. The cutter head pressure measures how hard the cutter head is working and then automatically controls its speed to provide the most efficient results while reducing stress and fatigue on the equipment.

[0046] Referring to FIG. 8, dredge automatic cutter head speed decrease control is carried out by decreasing cutter head speed at block 196, afterwhich a determination is made as to whether vacuum differential pressure is 0.25 above the set point, and if not, whether discharge flow is 0.25 below the set point at block 200, and if not, whether discharge pressure is 0.25 above the set point at block 202. If the vacuum differential pressure is 0.25 above the set point the cutter head is slowed to ¾ of the set point at block 204, afterwhich vacuum differential pressure is 0.500 above the set point at block 206, afterwhich the cutter head is slowed to ½ of the set point at 208. A determination is then made if the discharge flow is 0.50 below the set point at block 210, afterwhich a determination is made if the discharge pressure is 0.50 above the set point at block 212. A determination is then made as to whether vacuum differential pressure is 1 above the set point at block 214, and if so, the cutter head is slowed to ¼ of the set point at block 216. A determination is then made as to whether the vacuum differential pressure is 2 above the set point at block 218, and if so, the cutter head output is moved to zero at block 220. At block 222 a determination is made as to whether discharge flow is 0.75 below the set point, and if it is not, a determination is made whether the discharges pressure is 1 above the set point at block 224. At block 226 a determination is made as to whether the discharge flow is 1 below the set point, and if not, a determination is made at block 228 if discharge pressure is 2 above the set point, and if not, a determination is made whether the swing winch pressure is above the maximum set point at block 230, and if not, there is a return to START at block 232.

[0047] Referring to FIG. 9, ladder automatic raise control is carried out by starting the ladder control at block 234. A determination is then made as to whether the vacuum differential pressure is greater than the set point at block 236. If it is, a determination is made as to whether the swing speed is zero at block 238 and if so, whether the cutter head speed is zero at block 240. If it is, a water butterfly valve 66, which is located in suction pipe 23 between pump 22 and cutter head 25 (FIG. 2), is started at open sequence block 242 and a determination is made whether the vacuum differential pressure is greater than the set point at block 244. If it is not, the water butterfly valve close sequence is started at block 250. If it is, a determination is made as to whether the ladder reached the raised set point at block 246. If it is, the dredge arm is pulled back to set alarm at block 248, and if not, the ladder is raised to the set point at block 252. At block 254 a determination is made as to whether discharge flows are greater than the set point and if not, a determination is made whether the discharge pressure is 0.25 above the set point at block 256, and if not, whether the ladder raise count is greater than zero at block 258. If so, a determination is made as to whether the cutter head is at the speed set point at block 260 and if so, the ladder is lowered to set point to −1 from the ladder count at block 262. Butterfly valve 66 lets additional water into pipe 23 if the vacuum is too high to regulate the flow of collected material through pipe 23 which may reduce the need to physically move ladder 20. However, if this corrective action is unsuccessful, then an alarm sounds which then may require physically moving the barge and ladder back, as could occur in the event of a cave-in on top of the cutter head.

[0048] Referring to FIG. 10, the ladder and the swing control begins with positioning the swing at set point block 262. A determination is then made whether the vacuum differential pressure is greater than the set point at block 266 and if not, whether the discharge flow is greater than the set point at block 268. If not a determination is made as to whether the discharge pressure is greater than the set point at block 270, and if not, a determination is made as to whether the cutter speed equals the speed set point at block 272, and if so, a determination is made as to whether the cutter speed is less than the set point at block 274 and, if it is, whether the ladder raise count equals zero at block 276. If it is the ladder then is dropped to the set point at block 278.

[0049] In summary, the improved method and apparatus of the present invention automatically controls the swing sequence of the dredge ladder having the cutter head mounted on the distal end thereof by automatically controlling the cutter head speed and swing speed of the ladder. This in-turn controls the amount and speed of the collected material through the suction pipe and discharge pipe to provide for the most efficient pickup and delivery of the materials. This is further accomplished by automatically measuring the flow rate of the material, cutter head pressure, winch pressure, and other operating parameters, which heretofore required constant supervision and adjustment by the dredge operator, and then automatically making any necessary adjustment to enable the equipment to perform at peak efficiency.

[0050] It will be understood that a method and apparatus has been described which allows dredging operations to be controlled in an efficient, reliable and cost effective manner.

[0051] In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.

[0052] Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.