US3797139A

US3797139A - Floating dredge motion compensator

Info

Publication number: US3797139A
Application number: US00283473A
Authority: US
Inventors: E Larralde
Original assignee: Vetco Offshore Industries Inc
Current assignee: Vetco Gray LLC
Priority date: 1972-08-24
Filing date: 1972-08-24
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19
Also published as: JPS4970393A; JPS5411079B2; NL7311466A; NL155612B

Abstract

Apparatus automatically compensating for relative vertical movement between a dredging vessel and its cutter, or other formation removing mechanism, to maintain a predetermined vertical position of the cutter mechanism despite vertical motion of the floating dredge vessel caused by sea conditions. The compensating apparatus includes a cylinder and piston device containing a hydraulic fluid under pressure exerting a preselected lifting force on the cutter mechanism and automatically extensible and contractable to permit the vessel to move without effecting movement of the cutter mechanism and the force that such mechanism exerts on the formation.

Description

Larralde Mar. 19, 1974 FLOATING DREDGE MOTION COMPENSATOR [75] Inventor: Edward Larralde, Santa Barbara,

' Calif.

[73] Assignee: Vetco Offshore Industries, Inc.,

Ventura, Calif.

[22] Filed: Aug. 24, 1972 211 Appl. No.z283,,473

52 us. c1. 37/67,37/72 [51] Int. Cl E02f 3/90 [58] Field of Search 37/72, 67; 254/172 [56] References Cited v UNITED STATES PATENTS 3.579.872 5/1971 Jantzen ..37/72x 318.859 5/1885 Bowers 3.512.28l 5/1970 Hadjidakis ..37/72x FOREIGN PATENTS OR APPLICATIONS 851.333 /1960 Great Britain 37 72 32 I "39 y ,l/

PI-1 l g1 A 14 F V C 13 Primary Examiner-R0bert E. Pulfrey Assistant Examiner-Clifford D. Crowder Attorney, Agent, or Firm-Bernard Krieg'el [5 7] ABSTRACT Apparatus automatically compensating for relative vertical movement between a dredging vessel and its cutter, or other formation removing mechanism, to maintain a predetermined vertical position of the cutter mechanism despite vertical motion of the floating dredge vessel caused by sea conditions. The compensating apparatus includes a cylinder and piston device containing a hydraulic fluid under pressure exerting a preselected lifting force on the cutter mechanism and automatically extensible and contractable to permit the vessel to move without effecting movement of the cutter mechanism and the force that such mechanism exerts on the formation.

16 Claims, 3 Drawing Figures 1 FLOATING DREDGE MOTION COMPENSATOR The present invention relates to dredges, and more particularly to motion compensating apparatus for dredging vessels floating in a sea or other body of water, to isolate the cutter mechanisms of the dredges from the vertical or pitching motion of the floating vessels under sea conditions.

Floating dredging, vessels are subject to vertical motion caused by sea'conditions, such vertical motion seriously impairing the operation of the dredge in cutting the formation underlying the sea, ocean or other body of water, and also reducing the rate at which the spoil may be removed. In addition, such vertical motion of the dredge vessel imposes severe loads on the dredge ladder and the hull structure of the vessel. Long swells from the open sea are common in harbor mouth dredging, while short swells resulting from ships passing generally result in a complex hull motion. Swells having length similar to or longer than the dredge hull cause pitching of the hull, and, therefore, great variations in the force with which thecutter head bears against the formation.

By virtue of the present invention, a compensator apparatus is provided which is capable of isolating the vessel movement from its cutter mechanism, whereby the desired weight or drilling force is maintained on the cutter head irrespective of heaving of the vessel in a sea, ocean or other body of water.

In general, a compensator apparatus includes a cylinder and piston device connected between a dredge ladder and the supporting structure of the dredge, which is carried by the vessel hull. The ladder is pivotally mounted on the hull, carrying the drive mechanism and the cutter, which is to operate upon the formation underlying the body of water. The position of the ladder and the cutter mechanism carried thereby is determined by a cable support, which can be used to raise or lower the cutter relative to the hull. In apparatus embodying the present invention, the ladder and the cutter mechanism are supported hydraulically or fluidly by interposing a compensating apparatus between the travelling sheaves of the cable support and the free end of the ladder. The apparatus relies upon the maintenance of a required pressure ina fluid, such as a hydraulic fluid disposed within a cylinder and piston device of the apparatus, such pressure being maintained in the absence or presence of longitudinal movement of the cylinder and piston portion of the device with respect to each other, the hydraulic fluid exerting a continuous, substantially constant stress on the ladder. In other words, the hydraulic fluid supports a portion of the weight of the ladder and the cutter mechanism, the remainder of its weight being exerted on the cutter and against the formation being removed, such remainder of the drilling or cutter weight being maintained substantially constant since the relative longitudinal movement between the cylinder and piston, within the limits of their longitudinal travel with respect to each other, has no effect on the supporting force of the hydraulic fluid under pressure within the cylinder. Despite heaving or other vertical-movement of the hull portion of the dredge, the free end of the ladder and the cutter carried thereby will not move correspondingly to any appreciable degree, the movement of the dredging vessel or hull being incapable of transmission to the ladder and its cutter, which will remain in a predetermined position with respect to the formation being drilled.

It is, accordingly, apparent that the extensible hydraulic or fluid compensator maintains a generally constant suspension force on the ladder, causing the cutter to bear against the formation with the desired force, despite pitching or heaving of the dredge or its other vertical movement.

Another object of the invention is to provide an apparatus in which the cable system used for elevating the ladder and cutter mechanism carried thereby can function to raise or lower the cutter portion of the apparatus, including its ladder structure, to and from an operative position with respect to the formation without the necessity for such elevating force being transmitted through the fluid, such as hydraulic fluid, in the cylinder and piston compensator. In a more limited sense,

this aspect of the invention is achieved by providing a lock mechansim that secures the cylinder and piston together when the cylinder and piston are fully telescoped one with the other, such lock mechanism preferably being selectively operated from a remote location. Thus, the hydraulic fluid need not even be under pressure once the lock has been made effective, since the entire lifting force will be transmitted between the cylinder and piston portions of the compensator to the lock mechanism, and without the necessity for any of such force being transmitted through the hydraulic fluid within the cylinder. By virtue of providing a lock, such as a mechanical lock, between the cylinder and piston portions of the apparatus, the hydraulic fluid within the cylinder need not have an unduly high unit pressure imposed upon it. This is due to the fact that the load imposed upon the cable support mechanism in raising the ladder and the cutter mechanism out of the water is considerably greater than the hydraulic force required to support only a portion of the load or weight of the ladder and the cutter mechanism during the performance of a drilling operation, in which the hydraulic fluid maintains the ladder and the cutter mechanism in a predetermined position without any substantial adverse affect by the pitching or heaving of the vessel in the water.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This formis shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense.

Referring to the drawings:

FIG. 1 is a side elevational view, shown somewhat diagrammatically, of a dredge floating in a body of water for drilling a formation underlying a body of water;

FIG. 2 is an enlarged plan view, parts being shown in section, of the cylinder and piston portions of the apparatus in a fully collapsed position and locked to one another;

FIG. 3 is an elevational view, taken at right angles to the view illustrated in FIG. 2, disclosing the cylinder and piston portions of the apparatus in their unlocked or operative condition.

As disclosed in FIG. 1, a dredging vessel V is provided having a buoyant hull H floating in a sea, ocean or other body of water S, and adapted to cut into the formation F underlying the body of water through appropriate rotation and manipulation of a cutter head C brought to bear against the formation. A ladder structure L carries the cutter mechanism M, this ladder structure having its rear portion suitably pivotally supported by the buoyant hull H, such as by one or a plurality of pivot pins 10, the ladder structure being of a suitable length and extending forwardly of the hull a suitable distance from the pivot support 10, which, for example, may be about 200 feet, the ladder structure L and the cutter mechanism M carried thereby representing a total weight of perhaps 200,000 to 300,000 pounds.

The rear portion of the ladder structure carries a suitable drive motor 11 adapted to rotate a drive shaft 12 extending through a bearing support 13 secured to the forward end of the ladder structure, and further passing through a bearing support 14 behind the forward bearing support. The cutter head C is attached to the drive shaft 12 for bearing against and cutting the formation F. Such cutter head may be rather large, for example, weighing about 40,000 pounds. The weight of the ladder structure L not supported by the buoyant hull H is supported in part by the cutter head C bearing against the formation F, which effects the cutting action as a result of such weight, as well as by forward and lateral movements of the cutter head through use of suitable known mechanisms (not shown), and which per se form no part of the present invention. The weight of the ladder structure and the cutter mechanism M carried thereby, which is not to be imposed upon the cutter head C, is supported through a compensator apparatus A and a cable mechanism B attached thereto.

The compensator apparatus also permits relative vertical movement of the floating vessel V and the structures carried thereby with respect to the cutter head C, and without substantially modifying the weight imposed on the cutter head, or its position against the formation F. As disclosed, a suitable frame 15, such as an A frame, has its lower end pivotally mounted on the hull H by means of a pivot pin 16, its upper end rotatably supporting one or a plurality of upper sheaves 17, the A frame being suitably supported in an upwardly and forwardly inclined position through an intervening tension line or cable 18 extending between the upper end of the frame and the forward portion of a fixed frame structure 19 secured to the buoyant hull H. The upper portion of the compensating apparatus A is connected by a pivot pin 20 to one or more links 21, the upper part of which carries one or a plurality of rotatable sheaves 22 movable toward and away from the upper portion of the A frame 15. A suitable cable system 23 extends around the upper and lower sheaves 17, 22, and around a pulley 24 rotatably mounted on the forward portion of the frame 19, the cable being wound upon the drums 25 of a suitable winch 26 which is manipulatable in a known manner to pull the travelling sheaves 22 towards the upper sheaves 17, or allow the travelling sheaves to move downwardly from the upper sheaves. Through appropriate manipulation of the winch, the ladder structure L and cutter mechanism M carried thereby can be swung about the pivot support 10, the tension in the cables 23 being transmitted through the compensator apparatus A to the forward portion of the ladder bearing support 14. As described hereinbelow, the ladder structure L and the cutter mechanism M can be elevated completely from the water, or they can be lowered to a desired position below the surface of the water.

The compensator apparatus includes an elongate cylinder structure 30, the upper end of which is pivotally connected through the pivot 20 to the lower portion of the links 21. The cylinder structure includes an upper cylinder portion 31 whose lower cylinder head 32 is suitably secured to a connector 33 having upper pivot pins or trunnions 34 extending laterally therefrom, on which are pivotally mounted links 35 extending downwardly to a lower guide 36, the lower ends of the links being pivotally mounted on pins 37 suitably affixed to the upper portion of the guide. Movable longitudinally within the cylinder structure 30 is a piston structure 38 including a piston 39 slidable along the inner wall of the cylinder 31 and having a piston rod 40 attached thereto and extending slidably through the lower cylinder head 32 to a position below the connector 33. The piston rod structure 38 further includes a lower portion 41 pivotally secured to the upper rod portion 40 by a clevis 42 attached to the lower end of the upper rod portion and a pin 43 passing through the arms 44 of the clevis and through the upper end 45 of the lower portion 41 straddled by the clevis arms. The lower rod portion 41 is slidable longitudinally through the lower guide 36, extending downwardly a sufficient distance for pivotal attachment to the bearing support 14.

When the piston rod structure 38 is in its uppermost position within and relative to the cylinder 31, as determined by the abutting of a stop or limit sleeve 50 suitably welded or otherwise affixed to the lower rod structure 41 with the lower end of the guide 36 (FIG. 2), the piston rod structure and cylinder structure 30' can be mechanically secured to one another to prevent their relative movement. With the piston rod structure in its uppermost position with respect to the cylinder structure, a suitable lock pin 51 can be inserted through opposed holes or bores 52 in the guide 36 and through a central hole 53 in the lower rod structure aligned therewith. This pin 51 is inserted hydraulically into the locked position illustrated in FIG. 2, or removed therefrom, from a remote point on board the dredging vessel. As specifically illustrated, a lock cylinder 54 is suitably secured, as by screws 55, to the exterior of the guide 36, this cylinder containing a piston 56 secured to the lock pin 51. The introduction of suitable fluid under pressure through a suitable line 57 into the rod end of the cylinder 54 will cause the piston 56 to move longitudinally toward the head end of the cylinder to fully withdraw the lock pin from the rod structure, thereby permitting relative longitudinal movement to occur between the piston rod structure 38 and cylinder structure 30. On the other hand, the bleeding of the fluid under pressure from the rod end of the cylinder and its introduction through a suitable line 58 into the head end of the structure will shift the piston 56 in a direction away from the head end of the cylinder and insert the lock pin 51 through the aligned

holes

52, 53 in the guide 36 and lower rod 41, thereby locking the

parts

38, 40 together.

The upper and lower

piston rod portions

40, 41 of the apparatus are articulated with respect to one another through their pin interconnection 43 to avoid bending and binding in the parts because of the very substantial weight imposed upon them by the ladder structure L and the cutter mechanism M carried thereby. The inclination of the compensating apparatus A relative to the ladder structure L introduces a bending moment into the compensator structure, which would tend to bind the upper piston rod structure 40 within the cylinder 31 and introduce undue friction resisting relative movement between the cylinder 31 and the piston 39 and rod 40, as well as effect leakage of the seals 60 in the system between the head 32 and rod 40. The articulated relation between the upper and lower

piston rod structures

40, 41 prevents or minimizes such binding. The angle Y between the upper and lower piston rod structures has been exaggerated in FIG. 3 of the drawings. Actually, the included angle is about 83 to 85, the misalignment between the upper and lower rod structures being only a matter of about 5 to 7.

The compensator cylinder 31 contains a liquid 70 under pressure derived from a suitable accumulator 71 mounted on the drilling vessel, the liquid passing through a suitable hose 72, controlled by a valve 73, and into the head end 32 of the cylinder below the piston 39. The pressure of the liquid is maintained by a suitable compressed gas 74, such as compressed air, in the upper portion of the accumulator 7,1, the pressure of the gas being transferred through a suitable floating accumulator piston 75 to the liquid 70. The compressor piston 39 is movable longitudinally relatively within the cylinder 31, the liquid pressure therein being maintained at all times since the liquid 70 can pass through the hose 72 into and from the accumulator 71. The hydraulic and compressed airsystem for maintaining the liquid in the cylinder under pressure per se forms no part of the present invention. A description of such system is set forth in the application of Edward Larralde, Ser. No. 222,919, filed Feb. 2, 1972, for Variable Rate Hydraulic-Pneumatic Weight.Control and Compensating Apparatus, to which attention is directed.

In the operation of the apparatus illustrated in the drawings, the pressure of the compressed gas or air 74 is selected which will conform to the desired unit pressure of the liquid 70 acting within the compensator cylinder 30, such liquid pressure depending upon the formation being cut by the cutter head C, the pressure relieving the cutter head of a required portion of the weight of the ladder structure L and the cutter mecha-v nism M mounted thereon. The vertical position of the cutter head is controlled by the winch 26, which will either feed off cable 23 or pull in cable to raise or lower the ladder L and the cutter head C supported thereby. Actually, it is not necessary to continually manipulate the winch to determine the vertical position of the cut ter head Csince the position 39 can lower in the cylinder 30 as the cutter head drills in a downward direction, the cuttings being suitablyremoved from the location of the head C in any suitable manner, as through use of suction equipment, which forms no part of the present invention and which is therefore neither illustrated nor described herein. The pressure of the liquid 70 in the cylinder remains substantially constant and will determine the net weight of the ladder structure L and cutter mechanism M imposed on the cutter head C. Pitching or heaving of the vessel in the water, as, for example, as a result of swells, will not modify the position of the cutter head or the net drilling weight imposed thereon, since elevation of the hull H and of the compensator cylinder structure 30 can readily occur with respect to the piston structure 38, such extensible movement of the cylinder structure relative to the piston structure merely resulting in the liquid 70 flowing through the hose 72 toward the accumulator 71, but without modifying the pressure of the liquid acting in an upward direction in the piston 39, the tensile force imposed by the liquid on the piston structure remaining unchanged. On the other hand, lowering of the hull H will result in a corresponding relative descent of the cylinder structure 30 along the piston structure 38, the liquid moving from the accumulator 71 through the hose 72 back into the cylinder 31 without the unit pressure of the liquid being modified, such liquid under pressure still maintaining the same degree of tension in the piston rod structure 38, resulting in the forward portion of the ladder and the cutter head C remaining in position and without partaking of any degree of vertical movement that would substantially modify the drilling weight of the cutter head C against the formation F and of the continuous drilling effectiveness of the head in the formation being removed.

It is, accordingly, apparent that the liquid pressure in the compensator remains substantially constant, the compensator being capable of extending or contracting in accordance with vertical movement of the vessel in the water without essentially modifying the position of the cutter head C or of its drilling weight or force against the formation F being cut.

In the event it is desired to elevate the ladder structure L and the cutter mechanism M from the water, the winch 26 is appropriately manipulated to cause the travelling sheaves 22 to lower with respect to the upper sheaves 17, until the cylinder structure 30 moves downwardly to its fullest extent along the piston structure 38 and the guide 36 abuts the limit sleeve 50 affixed to the lower piston rod member 41, thereby aligning the holes or bores 53, 52 in the rod member 41 and the guide 36. Fluid pressure can then be directed into the cylinder 54 through the head end fluid-line 58 to move the piston toward the rod 41 and shift the lock pin 51 through the aligned

holes

52, 53, thereby locking the cylinder structure 30 and piston structure 38 to one another. The winch 26 can then be manipulated to move the travelling sheaves 22 toward the upper sheaves 17 and elevate the ladder L completely from the water S, the hydraulic fluid in the cylinder 31 not being required to transmit any of the load being lifted. Accordingly, when the comparator system A is to be made functional, only that liquid pressure is required in the cylinder 31 for relieving part of the weight of the ladder L and cutter mechanism M fromthe cutter head C. A unit liquid pressure for supporting the entire load of the ladder L and cutter mechanism M is not required.

In the event it is desired to vary the lifting force on the piston structure 38 and, therefore, the resultant load imposed on the cutter head C, it is only necessary to change the unit pressure of the compressed air 74, or other gas, in the accumulator 71, which will correspondingly change the unit pressure of the liquid 70 in the system, as set forth in the above-identified patent application, Ser. No. 222,919. Usually, if soft formations are being cut, the unit pressure will be greater in order that the cutter head be relieved of a greater portion of the weight of the ladder L and of the cutter mechanism M. In drilling hard formations, the unit pressure will be decreased to cause a corresponding greater load to be imposed on the cutter head C. The resultant load on the cutter head will remain substantially constant despite extensive pitch or heave of the dredge in the water, as described above.

I claim:

1. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said mechanism; means extending forwardly of said vessel and supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure.

2. In dredging apparatus as defined in claim 1; said one of said means being said cylinder means; said other of said means being said piston means.

3. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said mechanism; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure; said supporting means including means for raising and lowering said one of said means with respect to said vessel, said supporting means extending above and connected to the upper portion of said one of said means.

4. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said mechanism; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of saidcutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure; said one of said means being said cylinder means; said other of said means being said piston means; said supporting means including means for raising and lowering said cylinder means with respect to said vessel; said supporting means extending above and connected to the upper portion of said cylinder means.

5. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; said supporting means including means for raising and lowering said one of said means with respect to said vessel; and releasable lock means for securing said cylinder means and piston means to each other whereby raising and lowering of said one of said means raises and lowers said cutter mechanism with respect to said vessel.

6. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; said one of said means being said cylinder means; said other of said means being said piston means; said supporting means including means for raising and lowering said cylinder means with respect to said vessel; and releasable lock means for securing said cylinder means and piston means to each other whereby raising and lowering of said cylinder means raises and lowers said cutter mechanism with respect to said vessel.

7. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said mechanism; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure; said supporting means extending above and connected to the upper portion of said one of said means; said supporting means including one or more lower sheaves connected to said one of said means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved thereby for raising and lowering said one of said means with respect to said vessel.

8. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said mechanism; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure insaid cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure; said supporting means extending above and connected to the upper portion of said cylinder means; said supporting means including one or more lower sheaves connected to said cylinder means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved therebyfor raising and lowering said cylinder means with respect to said vessel.

9. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to to said one of said means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved thereby for raising and lowering said one'of said means with respect to said vessel; and releasable lock means for securing said cylinder means and piston means to each other whereby raising and lowering of said one of said means raises and lowers said cutter mechanism with respect to said vessel.

It). In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; said supporting means including one or more lower sheaves connected to said cylinder means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved thereby for raising and lowering said cylinder means with respect to said vessel; and releasable lock means for securing said cylinder means and piston means to each other whereby raising and lowering of said cylinder means raises and lowers said cutter mechanism with respect to said vessel.

1 1; In dredging apparatus: a vessel floating in a body of water; a ladder pivotally connected to said vessel and extending therefrom; a cutter mechanism carried by said ladder and including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said ladder; means extending forwardly of said vessel and supporting said cylinder means from said vessel; means operatively connecting said piston means to said ladder; and means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said ladder and cutter mechanism to support at least a portion of the weight of said ladder and cutter mechanism and thereby retain the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure.

12. In dredging apparatus: a vessel floating in a body of water; a ladder pivotally connected to said vessel and extending therefrom; a cutter mechanism carried by said ladder and including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said ladder; means supporting said cylinder means from said vessel; means operatively connecting said piston means to said ladder; and means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said ladder and cutter mechanism to support at least a portion of the weight of said ladder and cutter mechanism and thereby retain the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure; said supporting means including means for raising and lowering said cylinder means with respect to said vessel; said supporting means extending above and connected to the upper portion of said cylinder means.

13. In dredging apparatus: a vessel floating in a body of water; a ladder pivotally connected to said vessel and extending therefrom; a cutter mechanism carried by said ladder and including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting said cylinder means from said vessel; means operatively connecting said piston means to said ladder; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move laterally with respect to each other to provide an upwardly directed force on said ladder and cutter mechanism to support at least a portion of the weight of said ladder and cutter mechanism and thereby retain the drilling weight of said cutter device against the formation at a selected value; said supporting means including means for raising and lowering said cylinder means with respect to said vessel; and releasable lock means for securing said cylinder means and piston means to each other whereby raising and lowering of said cylinder means raises and lowers said ladder and cutter mechanism with respect to said vessel.

14. In dredging apparatus as defined in claim 13; said cylinder means including a guide; said piston means including a piston in said cylinder means, an upper piston rod portion secured to said piston and extending from said cylinder means, a lower piston rod portion pivotally connected to said upper rod portion and slidable in said guide; said lower rod portion being connected to said ladder; said releasable lock means securing said guide to said lower rod portion whereby raising and lowering of said cylinder means raises and lowers said ladder and cutter mechanism.

15. In dredging apparatus: a vessel floating in a body of water; a ladder pivotally connected to said vessel and extending therefrom; a cutter mechanism carried by said ladder and including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting said cylinder means from said vessel; means operatively connecting said piston means to said ladder; means for maintaining a fluid medium under pressure in saidv cylinder means on one side of said piston means as said piston means and cylinder means move laterally with respect to each other to provide an upwardly directed force on said ladder and cutter mechanism to support at least a portion of the weight of said ladder and cutter mechanism and thereby retain the drilling weight of said cutter device against the formation at a selected value; said cylinder means including a guide; said piston means including a piston in said cylinder means; an upper piston rod portion secured to said piston and extending from said cylinder means, a lower piston rod portion pivotally connected to said upper rod portion and slidable in said guide; said lower rod portion being connected to said ladder.

16. In dredging apparatus: a vessel floating in a body of water; a ladder pivotally connected to said vessel and extending therefrom; a cutter mechanism carried by said ladder and including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting said cylinder means from said vessel; means operatively connecting said piston means to said ladder; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move laterally with respect to each other to provide an upwardly directed force on said ladder and cutter mechanism to support at least a portion of the weight of said ladder and cutter mechanism and thereby retain the drilling weight of said cutter device against the formation at a selected value; said supporting means including one or more lower sheaves connected to said cylinder means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved thereby for raising and lowering said cylinladder and cutter mechanism.

29 3 32 "um rmo s'm'mss' iuxrmazwr 01mm;

CEREIFICZHE G1 CORRECTIUN 3,797,139 Dated March 19 9 1g Ed v ard Larra lde v Patent No.

Iuvuntorh'.)

u certified that error zrppcnrs in the abovw-idcntifivd patent 'r' I J- and that said Letters Patent are heuquby corrected as shown below:

Column '2, line 21f canc l "wifih" and substitute -with1n--. Column. 5, line 24:" cancel oompress'oxg" and substitute I i I I -comp'enstor---.

Signediand ise aled this 1st day of Octobe'r l974'.

(SEAL) Attest: s McCOY M. oussoN JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents

Claims

4. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said mechanism; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure; said one of said means being said cylinder means; said other of said means being said piston means; said supporting means including means for raising and lowering said cylinder means with respect to said vessel; said supporting means extending above and connected to the upper portion of said cylinder means.

8. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said mechanism; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure; said supporting means extending above and connected to the upper portion of said cylinder means; said supporting means including one or more lower sheaves connected to said cylinder means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved thereby for raising and lowering said cylinder means with respect to said vessel.

9. In dredging apparatus: a vessel floating in a body of water; a cutter mechanisM carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; said supporting means including one or more lower sheaves connected to said one of said means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved thereby for raising and lowering said one of said means with respect to said vessel; and releasable lock means for securing said cylinder means and piston means to each other whereby raising and lowering of said one of said means raises and lowers said cutter mechanism with respect to said vessel.

10. In dredging apparatus: a vessel floating in a body of water; a cutter mechanism carried by and extending forwardly from said vessel and movable with respect thereto, said mechanism including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting one of said means from said vessel; means operatively connecting said other of said means to said cutter mechanism; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said cutter mechanism supporting at least a portion of the weight of said cutter mechanism and thereby retaining the drilling weight of said cutter device against the formation at a selected value; said supporting means including one or more lower sheaves connected to said cylinder means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved thereby for raising and lowering said cylinder means with respect to said vessel; and releasable lock means for securing said cylinder means and piston means to each other whereby raising and lowering of said cylinder means raises and lowers said cutter mechanism with respect to said vessel.

11. In dredging apparatus: a vessel floating in a body of water; a ladder pivotally connected to said vessel and extending therefrom; a cutter mechanism carried by said ladder and including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; both of said means being located above and overlying said ladder; means extending forwardly of said vessel and supporting said cylinder means from said vessel; means operatively connecting said piston means to said ladder; and means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move longitudinally with respect to each other to provide an upwardly directed force on said ladder and cutter mechanism to support at least a portion of the weight of said ladder and cutter mechanism and thereby retain the drilling weight of said cutter device against the formation at a selected value; and means for maintaining said fluid medium in said cylinder means at a substantially constant selected pressure.

15. In dredging apparatus: a vessel floating in a body of water; a ladder pivotally connected to said vessel and extending therefrom; a cutter mechanism carried by said ladder and including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting said cylinder means from said vessel; means operatively connecting said piston means to said ladder; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move laterally with respect to each other to provide an upwardly directed force on said ladder and cutter mechanism to support at least a portion of the weight of said ladder and cutter mechanism and thereby retain the drilling weight of said cutter device against the formation at a selected value; said cylinder means including a guide; said piston means including a piston in said cylinder means; an upper piston rod portion secured to said piston and extending from said cylinder means, a lower piston rod portion pivotally connected to said upper rod portion and slidable in said guide; said lower rod portion being connected to said ladder.

16. In dredging apparatus: a vessel floating in a body of water; a ladder pivotally connected to said vessel and extending therefrom; a cutter mechanism carried by said ladder and including a cutter device for cutting a formation submerged in the body of water; cylinder means; piston means slidable in said cylinder means; means supporting said cylinder means from said vessel; means operatively connecting said piston means to said ladder; means for maintaining a fluid medium under pressure in said cylinder means on one side of said piston means as said piston means and cylinder means move laterally with respect to each other to provide an upwardly directed force on said ladder and cutter mechanism to support at least a portion of the weight of said ladder and cutter mechanism and thereby retain the drilling weight of said cutter device against the formation at a selected value; said supporting means including one or more lower sheaves connected to said cylinder means, one or more upper sheaves carried by said vessel, a winch, and cable means passing over said upper and lower sheaves and connected to said winch to be moved thereby for raising and lowering said cylinder means with respect to said vessel; said cylinder means including a guide; said piston means including a piston in said cylinder means, an upper piston rod portion secured to said piston and extending from said cylinder means, a lower piston rod portion pivotally connected to said upper rod portion and slidable in said ladder; and releasable lock means for securing said guide to said lower rod portion whereby raising and lowering of said cylinder means raises and lowers said ladder and cutter mechanism.