US3152409A

US3152409A - Dredging equipment

Info

Publication number: US3152409A
Application number: US211493A
Authority: US
Inventors: Charles D Ramsden; Russell J Robertson; William G Fraser; Ole P Erickson
Original assignee: PACIFIC COAST ENG CO
Current assignee: PACIFIC COAST ENG CO; PACIFIC COAST ENGINEERING Co
Priority date: 1962-07-23
Filing date: 1962-07-23
Publication date: 1964-10-13
Anticipated expiration: 1981-10-13
Also published as: GB1000618A; NL6705755A; NL295628A; NL137396C

Description

1964 c. D. RAMSDEN ETAL 3,152,409

DREDGING EQUIPMENT 5 Sheets-Sheet 1 Filed July 23, 1962 INVENTORS N Nw m TR vE WHE N E30 0 AORK T w v T DJGR /V A EL LEMP H n i. H M ML T RWO 1964 c. D. RAMSDEN ETAL 3,

DREDGING EQUIPMENT 5 Sheets-Sheet 2 Filed July 23, 1962 5 SN Y E E mo N NSF-EN EMBSO R m WJR T DJ mm PA MM. m fim E ASLE H WWW r Oct. 13, 1964 c. D. RAMSDEN ETAL 3,152,409

DREDGING EQUIPMENT 5 Sheets-Sheet 5 Filed July 23-, 1962 0 my w R: E ESN N AOR WRRF 0 I .6 T

L am T LM I. LEAD: R R AMME E mRmm M Y B 1964 c. D. RAMSDEN ETAL 3, 9

DREDGING EQUIPMENT Filed July 23, 1962 5 Sheets-Sheet 4 INVENTORS CHARLES 0. RAMSDEN RUSSELL J. ROBERTSON By WILLIAM G. FRASER OLE P. ERICKSON WWW THE IR ATTORNEYS C. D. RAMSDEN ETAL DREDGING EQUIPMENT 5 Sheets-Sheet 5 Filed July 25, 1962 3 N Y 0 P. MMBR N mD E 8530 0 fi r WRRFG M aJam w EL E LEAP. H mxufl T L mfimm Y B United States Patent 3,152,409 DREDGIN G EQUIPMENT Charles D. Ramsden, Alameda, and Russell J. Robertson, San Leandro, Calif, William G. Fraser, Tampa, Fla, and Ole P. Erickson, Castro Valley, Calif, assignors to Pacific Coast Engineering Company, a corporation of California Filed July 23, 1962, Ser. No. 211,493 13 Claims. (CI. 37-61) Our invention relates to under Water dredging and more particularly to improved dredging equipment for such purpose.

Barges designed for dredging purposes, conventionally utilize a dredge pump or pumps of the centrifugal type. A centrifugal pump for such purposes can be designed and built to produce a discharge pressure which is only limited by practical considerations of cost, power requirements and physical size. However, a centrifugal pump is limited in its ability to provide suction pressure or vacuum pressure by the fact that the maximum theoreical vacuum pressure is a perfect vacuum of 29 to 30 inches of mercury. Regardless of size, power, or other design considerations in the pump, the suction pressure cannot exceed atmospheric pressure as represented by the creation of a perfect vacuum at the intake or suction side of the pump.

A practical design of a dredge pump produce an effective vacuum pressure of the order of 23 to 26 inches of mercury. For a successful dredging operation, the velocity of the fluid mixture flowing through the suction pipe to the pump must be sufficiently high to carry and trans port the solid matter such as sand, gravel and rock, usually found in suspension. This suction pipe velocity is normally held at a minimum of 8 to 12 feet per second as a result of both laboratory tests and practical experience.

The differential pressure created between the existing atmospheric pressure and the negative suction pressure developed at the suction side of the pump is the only force available to perform two basic functions, namely (1) to overcome frictional losses occurring as the water and solid mixture enters the suction line and is transmitted therealong to the centrifugal pump itself, and (2) to provide power in the form of velocity and pressure to physically elevate the specific weight of solid material from the bottom of the body of the water up to the dredge pump.

It follows from this that the more friction losses there are in the suction line, the less power is available for lifting solid material. Thus, the dredge designer attempts to reduce friction losses by providing the largest diameter and shortest length of suction line possible, consistent with requirements for a suction pipe velocity sufficient to lift, carry in suspension, and transport the mixture of Water and solids in suspension therein.

If it were possible to eliminate all friction losses in the suction line, the full available suction pressure could be utilized for lifting solids. However, such a condition cannot be achieved because of the required rate flow in the suction line. Even if it were possible to eliminate friction losses and to utilize all of the available suction pressure for lifting solids, there exists the maximum limit of available power, as represented by the creation of a perfect vacuum at the suction side of the pump.

The power available for lifting solids in a simple hydraulic suction dredge using a single centrifugal dredge pump mounted on the dredge has been shown by calculation and actual experience when dredging at moderate depths to be suificient to transport only 15-20 percent solid mixtures. As depths increase, the percentage of solid mixtures pumped decreases, until it approaches 0 3,152,409 Patented Oct. 13, 1964 percent solids at feet. The limiting factor in this connection is the limiting pressures capable of being developed at the suction side of the pump despite the fact that the dredge pump has the inherent ability to pump much higher percentages of solid mixtures, if such mixtures could be brought to the suction inlet of the pump.

Accordingly, if some means could be provided to accomplish this under the conditions prevailing in connection with such dredging operations, the conventional centrifugal dredge pump could be made to pump mixtures up to 50 to 60 percent solids as compared to the 15 to 20 percent solids under the previously existing conditions. This could double the output of a given pump, or in the alternative, a comparable output could be realized with a pump of smaller size than previously deemed necessary.

By the same token, if it were possible by practical means, to bring the solids in suspension to the suction side of the pump, dredging at greater depths can be made possible, for example, to depths beyond 140 feet which appears to be the practical limit of present day equipment.

Among the objects of the present invention are:

(1) To provide novel and improved dredging equipment;

(2) To provide novel and improved dredging equipment capable of considerably increased output capacity over and above that of prior equipment of comparable s1ze;

(3) To provide novel and improved dredging equipment of substantially lighter weight than prior equipment of comparable output capacity;

(4) To provide novel and improved pump means for dredging;

(5) To provide novel and improved dredging equipment for dredging to depths considerably beyond that of prior equipment of like type.

Additional objects of our invention will be brought out in the following description of a preferred embodiment of the same, taken in conjunction with the accompanying drawings, wherein:

FIGS. 1A and 1B together constitute a side view in elevation of dredging equipment embodying the features of the present invention;

FIGS. 2A and 2B, together constitute a plan view of the equipment depicted in FIGS. 1A and 1B;

FIG. 3 is a view partly in section, depicting details of a jet pump assembly and associated cutter constituting important features of the dredging equipment of the preceding figures;

FIG. 4 is a transverse view taken in the plane 44 of FIG. 3:

FIG. 5 is a transverse view taken in the plane 5-5 of FIG. 3:

FIG. 6 is a longitudinal view, partly in section, depict ing with greater clarity, jet construction details of the jet pump assembly of FIG. 3; and

FIG. 7 is a View in section taken in the plane 7-7 of FIG. 6.

Referring to the drawings for details of our invention in its preferred form, all the power equipment is installed on a barge 1 having parallel spaced forward extensions 3 and 5, leaving a channel '7 of exposed water between them, for the anchored end of a digging ladder 9, which is hingedly secured to the barge by a hinge mounting, thus permitting of the digging ladder being lowered and raised with respect to a horizontal stored position.

This digging ladder, in the main, is of girder construction involving four

longitudinal corner members

15, 17, 19, 21, inter-connected by a lattice work of angle iron members 25. At the barge end, the ladder includes tapered side plates 29, with the two upper corner members and 17 extending therealong and terminating in shaft bearing 31 for hingedly securing the digging ladder at the barge.

On the median axis of the barge and at substantially water level, a conventional centrifugal type dredge pump 35 is mounted and powered by a prime mover 37 coupled thereto. This pump is the main pump, there being auxiliary pump equipment involved in the system to which reference will later be made. A suction line 41 connected at one end to this main pump, is formed with an intermediate flexible section 43 to permit the suction line to pass longitudinally into and along the digging ladder and flex with each hinge movement of such ladder, that portion of the suction line Within the ladder being supported therein in any suitable manner.

Supported within the ladder adjacent the outboard end thereof is a jet pump assembly 47 coupled to the suction line 4-1 of the main centrifugal pump 35 on the barge. This jet pump assembly includes a jet casting 4-9 having a cylindrical interior approaching in diameter, that of the suction line, the casting being formed with a plurality of jet passageways 53 in the wall thereof, at equally spaced points about the periphery of the casting, the passageways being formed to function as jets. Lining the interior of the casting from the discharge lips of the jets is a nickel alloy liner 55 to provide increased wear and durability.

At one end, the casting is flanged for bolting to the smaller end of a Venturi 57, which, in turn, at its larger end, is bolted to the suction line 41. The opposite end of the jet casting is likewise flanged, and to this end, is bolted a hollow cylindrical mounting 59 for a cutter head 61, such hollow cylindrical mounting including a threaded tip 63 welded at one end within a cylindrical pipe section 65, the other end of which is welded between an outer and inner section 67, 69 respectively of a flange for aflixing the same to the proximate end of the jet pump assembly casting 49. The cutter head mounting is finished 01f by a liner 71 anchored into position by a weld 73 at the tip of the mounting.

To operate a jet type pump, Water must be fed to the jets at high pressure, to create at the discharge end of the jets, a region of reduced pressure, which, in turn, due to atmospheric pressure, serves to bring in Water and solid matter in suspension from the cutter head end of the line and causes it to be directed up the suction line 41 to a point within reach of the main centrifugal pump 35.

To supply water at the needed high pressure, which may be of the order of 200 lbs. per square inch or more, we provide an auxiliary or pressure pump 79 on the barge, preferably one of the centrifugal type, and of a size adapted to handle the requirements of the installation. This latter pump has a suction line 81, with its intake end submerged in the water. The discharge side of this pump is flow connected to a pressure housing 85 surrounding and enclosing that portion of the jet casting 49 in Which the jet passageways are located and forms part of the jet pump assembly.

Rather than flow connect the pressure pump 79 to this pressure housing by a separate and independent pressure line, we prefer to form the upper two

corner members

15 and 17 of the ladder, of coupled pipe sections, to provide twin pressure lines. To each of these pressure lines, at the hinge end of the ladder, a flexible hose coupling 87 from the discharge of the pressure pump may be connected. At the jet pump assembly housing, each of these twin pressure lines is extended through a wall of the pressure housing 85 and Welded thereto. Thus, these upper corner members of the digging ladder, not only function as structural members of the ladder, but serve the additional function of pressure lines for the jet pump assembly.

With the cutter head 61 supported on the end of its mounting 59, provision must be made for rotating the same in order for the cutter head to function. We provide for such rotational movement of the cutter head, by utilizing the suction line 41 of the main pump, as a drive coupling or drive shaft, adapted to be driven from a prime mover 91 on the barge, and through its rotation, cause rotation of the cutter head. As an alternative, the prime mover may be mounted on the ladder itself, preferably in proximity to the hinge line.

Such rotational movement of the suction line must be accomplished without disturbing the ability of the suction line to function as such and carry the water and suspended solids to Within reach of the main centrifugal pump 35 on the barge.

Toward this end, the flexible section 43 of the main pump suction line is terminated in a thrust box 95 supported within the digging ladder. In an opposite wall of the thrust box, the initial section of the continuing suction line is rotatably anchored in suitably sealed bearings, and provided externally of the thrust box, with a gear 97 which may be coupled through a suitable drive assembly 99 to the cutter drive engine 91, which, in the embodiment illustrated, is located on one of the forward extensions of the barge alongside the hinged end of the digging ladder.

The thrust box serves as an end support for that portion of the suction line extending down through the digging ladder, which at spaced points along the ladder, will be rotatably supported in suitable bearings carried within the ladder for such purpose.

Utilizing the suction line as a drive shaft for the cutter head, necessitates construction of the pressure housing of the jet pump assembly, to permit of such rotation, without causing corresponding rotation of the pressure housing and the digging ladder to which it is connected, for such rotation of the digging ladder, not only could not be tolerated, but would create insurmountable problems.

Accordingly, the specific construction of the pressure housing 85 is such as will permit rotational movement of the suction line independently of the pressure housing, while maintaining a proper sealed condition between the housing and its mounting, to minimize loss of pressure from the inside of the housing, and the probable entrance of murky water and abrasive from outside the housing, particularly during quiescent periods.

Specifically, it includes a large end wall of substantially rectangular configuration having a large central opening 107, permitting the wall to loosely fit about the jet casting, and a smaller end wall 109 of substantially circular configuration, this smaller end wall also having a central opening 111 therethrough of sufficient size to fit over the cutter head mounting 59. An outer Wall 113 of heavy sheet metal, welded at one end to the periphery of the large rectangular wall 105, tapers to closely fit the circumference of the circular end wall 109 to which it is also welded.

At the location of the larger Wall, the jet casting is formed with parallel peripheral ribs 117, 119 adapted to support a bearing ring 121 welded thereto against which an inturned sealing ring 123 may be maintained in relative sliding relationship by supporting it on a flange 12S bolted to the larger end wall about the circumference of the opening therein.

At the location of the smaller end Wall of the pressure housing, a similar flange 129 bolted about the circumference of the opening therethrough, carries a bearing housing 131 in which is disposed a plurality of phenolic staves 133 for relative sliding contact with a sleeve 135 surrounding the cutter head mounting cylinder 65 and welded thereto, the sleeve preferably being chrome plated.

The bearing housing 131 at its inner end, which brings it within the jet or pressure housing 85, carries a sealing ring 139 in sealing engagement with the sleeve, and exposed to the pressure of water in the pressure housing to maintain sealing. Between this sealing ring 139 and the bearing staves 133 is a chamber 141 exposed to the admission of liquid from the pressure housing through small openings 143 provided in the bearing housing at this region, to effect and maintain water lubrication of the bearing staves at this end thereof.

The pressure housing is stabilized as to its location, as previously indicated, by its connection to the end of the digging ladder. Relative to the specific pressure housing under consideration, such connection to the digging ladder is effected by welding the ends of the two lower corner members 19 and 21 of the ladder to the larger end wall at the lower corners thereof, While the twin

pressure line members

15 and 17 of the ladder pass through the upper corners of the larger end wall, to which they are welded.

By reason of the drive connection to the suction line, and the construction and manner of mounting of the pressure housing of the jet pump assembly, the suction line may be rotated and function as a drive shaft, so as to drive the cutter head, and without affecting either the ability of the suction line to function as such, or to interfere with efficient supply of water at high pressure to the jets of the jet pump assembly.

Because of the ability of the jet pump assembly to enhance the capacity capability of the main centrifugal pump, the entire system may function for shallow dredging operations with substantially double the capacity of conventional available equipment of corresponding size, at the same time, permitting of dredging to depths far in excess of that capable with present-day conventional equipment. For example, depths of the order of about 140 feet represent the maximum economical capability of comparable present-day equipment, while, with equipment constructed in accordance with the present invention, dredging at depths exceeding 200 feet and more may be readily accomplished.

When dredging at such depths, however, digging ladders of considerable longer lengths than those previously employed, must be utilized. Conventionally, it has been the practice to support the outboard end of such a digging ladder from a derrick or hoist mounted on the barge, whereby the digging ladder may be raised or lowered at will on its hinge axis. With the longer digging ladders required through the use of the present invention, the tipping moment exerted by such ladder becomes quite large, and in fact could be sufficient to tip the barge up on end, unless the barge were well weighted down to counteract such tipping moment.

In accordance with our present invention, we have eliminated all such tipping moments regardless of the length of the digging ladder, and as a result, avoid any need for concern as to whether the barge possesses sufficient weight to counteract the tipping movement to which it might otherwise be exposed when using conventional equipment.

We accomplish the foregoing broadly, by supporting the outboard end of the digging ladder in a manner which will not transfer the carried load to the barge itself. A pair of

pontoons

151, 153 of sufiicient displacement to support the outboard end of the digging ladder, are disposed, one to either side of the ladder, and are maintained in such spaced relationship by a bridge 155 connecting the two pontoons. The resulting pontoon assembly is maintained at a distance from the barge by a pair of floating

booms

157, 159, each connected at one end to the barge, and at its other end to one of the pontoons. Rigidity is secured by means of cross cables 163, each connecting at one end to the anchor point of one of the floating booms, and at its other end to an upper corner of the bridge connecting the pontoons.

Supported at an intermediate point of the bridge, is a sheave 171 constituting a component of a sheave system which includes a power driven winch 175 located on the barge, and a sheave 177 mounted on the digging ladder toward the outboard end thereof. A cable 179 inter-coupling the winch and the aforementioned sheaves,

enables an operator on the barge to control the lifting and lowering of the digging ladder on its hinge axis, between a substantially horizontal position of the digging ladder, and any depth within the range of the equipment. With the outboard end of the digging ladder thus supported from the bridged pontoons, it becomes apparent that regardless of the length of the digging ladder, the barge will not be subjected to any tipping moments.

From the foregoing description of our invention in its preferred form, it can be readily appreciated that the same fulfills all the objects of our invention, and while we have illustrated and described the same in considerable detail, the same is subject to alteration and modification without departing from the underlying principles involved, and we accordingly do not desire to be limited in our protection to the specific details illustrated and described, except as may be necessitated by the appended claims.

We claim:

1. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted to be lowered to a depth below the surface of water on which said barge may be floating,

a centrifugal type dredge pump on said barge and having a suction line extending along and supported by said ladder,

a jet pump assembly carried by said ladder and connecting to said suction line, said jet pump assembly including jet means of generally cylindrical shape flow coupled to said suction line and including at least one jet in the wall thereof,

a pressure housing afiixed to said digging ladder and surrounding said jet means and enclosing said jet,

means rotatably mounting said jet means with respect to said surrounding pressure housing,

additional pump means on said barge,

means directing the output of said additional pump means along said ladder to said pressure housing to pressure feed said jet,

a cutter head and means coupling the same to the outboard end of said jet means,

means for rotating said suction line and jet means to rotate said cutter head without interrupting the functioning of said jet pump, and

means for raising and lowering said ladder.

2. Dredging equipment comprising a barge,

additional pump means on said barge,

a cutter head and means coupling the same to the out board end of said jet means,

means for rotating said suction line and jet means to rotate said cutter head without interrupting the functioning of said jet pump,

said suction line and jet rotating means including a rotatable thrust bearing coupled in said suction line,

to divide said suction line into a non-rotating portion connecting to said centrifugal dredge pump, and an adjacent portion rotatable with respect thereto and connecting with said cutter head by way of said jet means and said coupling means,

rotation permitting seal means between said jet means and said pressure housing, and

means for rotatably driving the rotatable portion of said suction line, and

means for raising and lowering said ladder,

said ladder raising and lowering means including a pair of pontoons one to either side of said ladder,

a bridge connecting said pontoons,

floating booms connecting said pontoons to said barge at a distance from said barge, and

a sheave system including a Winch on said barge, a sheave on said bridge and cables from said winch, about said sheave and to said ladder.

3. Dredging equipment comprising a barge,

a jet pump assembly carried by said ladder and connecting to said suction line, said jet pump assembly including jet means of generally cylindrical shape flow coupled to said suction line and including a plurality of jets in the wall thereof,

a pressure housing surrounding said jet means and enclosing said jets,

means rotatably supporting said jet means relative to said surrounding pressure housing,

additional pump means on said barge,

means directing the output of said additional pump means along said ladder to said pressure housing to pressure feed said jets,

said suction line and jet rotating means including a rotatable thrust bearing coupled in said suction line, to divide said suction line into a non-rotating portion connecting to said centrifugal dredge pump, and an adjacent portion rotatable with respect thereto and connecting with said cutter head by way of said jet means and said coupling means,

means for rotatably driving the rotatable portion of said suction line, and

means for raising and lowering said ladder,

a bridge connecting said pontoons,

means connecting said pontoons to said barge at a distance from said barge, and

4. Dredging equipment comprising a barge,

a pressure housing surrounding said jet means and enclosing said jets,

additional pump means on said barge,

means for rotatably driving the rotatable portion of said suction line,

means for raising and lowering said ladder at its free end,

a bridge connecting said pontoons,

5. Dredging equipment comprising a barge,

said digging ladder including a pipe line as a longitudinal structural member thereof,

a centrifugal type dredge pump on said barge and having a. suction line extending along and supported by said ladder,

a pressure housing afiixed to said digging ladder with said pipeline terminating therein, said pressure housing surrounding said jet means and enclosing said j additional pump means on said barge,

means directing the output of said additional pump means down said pipe line structural member of said ladder to said pressure housing to pressure feed said j a cutter head and means coupling the same to the outboard end of said jet means in longitudinal spaced relationship to said pressure housing,

means for rotating said cutter head without interrupting the functioning of said jet pump,

and means for raising and lowering said ladder.

6. Dredging equipment comprising a barge,

a pressure housing afl'ixed to said digging ladder with said pipeline terminating therein, said pressure housing surrounding said jet means and enclosing said jets,

additional pump mean on said barge,

means directing the output of said additional pump means down said pipe line structural member of said ladder to said pressure housing to pressure feed said jets,

said cutter head rotating means including a rotatable thrust bearing coupled in said suction line, to divide said suction line into a non-rotating portion connecting to said centrifugal dredge pump, and an adjacent portion rotatable with respect thereto and connecting with said cutter head by way of said jet means and said coupling means,

and means for rotatably driving the rotatable portion of said suction line,

and means for raising and lowering said ladder.

7. Dredging equipment comprising a barge,

a pressure housing surrounding said jet means and enclosing said jets,

additional pump means on said barge,

means for rotatably driving the rotatable portion of said suction line,

and means for raising and lowering said ladder.

8. Dredging equipment comprising a barge,

a digging ladder extending from said barge and adapted 10 to be lowered to a depth below the surface of Water on which said barge may be floating,

said digging ladder including a pipe line as a longitudinal strutural member thereof,

a dredge pump on said barge and having a suction line extending along and supported by said ladder,

a jet pump assembly carried by said ladder and conmeeting to said suction line, said jet pump assembly including at least one jet,

additional pump means on said barge, and

means directing the output of said additional pump means down said pipe line structural member of said ladder to said jet pump assembly to pressure feed said jet.

9. Dredging equipment comprising a barge,

a pressure housing atfixed to said digging ladder with said structural pipeline member terminating therein, said pressure housing surrounding said jet means enclosing said jet,

additional pump means on said barge, and

means directing the output of said additional pump means down said pipe line structural member of said ladder to said pressure housing to pressure feed said jet.

10. Dredging equipment comprising a barge,

said digging ladder being fabricated of longitudinal corner structural members including a pipe line as at least one of said structural members thereof,

a jet pump assembly carried by said ladder and connecting to said suction line, said jet pump assembly including jet means of generally cylindrical shape flow coupled to said suction line and including a plurality of jets in the wall thereof and a lining of nickel hardened alloy extending downstream from the lips of said jets,

a pressure housing affixed to said digging ladder with each said pipeline terminating therein, said pressure housing surrounding said jet means and enclosing said jets,

additional pump means on said barge,

means directing the output of said additional pump means down each said pipe line structural member of said ladder to said pressure housing to pressure feed said jets,

means for rotating said cutter head without interrupting the functioning of said jet pump, said cutter head rotating means including a rotatable thrust bearing coupled in said suction line, to divide said suction line into a non-rotating portion connecting to said centrifugal dredge pump, and an adjacent portion rotatable with respect thereto and connecting with said cutter head by way of said jet means and said coupling means.

11. Dredging equipment comprising a barge,

a dredge pump on said barge and having a suction line extending along and supported by said ladder, and

means for raising and lowering said ladder,

said means including a float assembly and means fixedly maintaining said float assembly at a distance from said barge, and

a sheave system including a winch on said barge, a sheave carried by said float assembly, and a cable from said winch, about said sheave and to said ladder.

12. Dredging equipment comprising a barge,

means for raising and lowering said ladder,

said means including a pair of pontoons one to either side of said ladder,

a bridge connecting said pontoons,

means maintaining said pontoons at a fixed distance from said barge, said means including a pair of floating booms, each connected at one end to said barge and at its other end to one of said pontoons, and

a sheave system including a winch on said barge, a sheave on said bridge and a cable from said winch, about said sheave and to said ladder.

13. Dredging equipment comprising a barge,

means for raising and lowering said ladder,

said means including a pair of pontoons one to either side of said ladder,

a bridge connecting said pontoons,

means maintaining said pontoons at a fixed distance from said barge, and

References Cited in the file of this patent UNITED STATES PATENTS 632,126 Kirk Aug. 29, 1899 868,774 Goth Oct. 22, 1907 1,619,850 Casey Mar. 8, 1927 1,759,490 Neveling May 20, 1930 1,861,349 Lockett May 31, 1932 FOREIGN PATENTS 851,790 Great Britain Oct. 19, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,152,409 October 13, 1964 Charles D. Ramsden et al,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 1 to 4, for "Charles D. Ramsden, of Alameda, and Russell J. Robertson, of San Leandro, California, William G. Fraser, of Tampa, Florida, and Ole P, Erickson, of Castro Valley, California," read Charles D. Ramsden, of Alameda, Russell J, Robertson, of San Leandro, and William G, Fraser, of Castro Valley, California and Ole P. Erickson, of Tampa, Florida, in the heading to the printed specification lines 3 to 5, for "Charles D, Ramsden, Alameda, and Russell J. Robertson, of. San Leandro, Calif. William G. Fraser, Tampa, Fla, and Ole P. Erickson, Castro Valley, Calif, read Charles D. Ramsden, Alameda, Russell J. Robertson, San Leandro, and William G. Fraser, Castro Valley, Calif and Ole P. Erickson, Tampa, Fla.

Signed and sealed this 23rd day of February 1965.

(SEAL) Attest:

ERNEST W, SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. DREDGING EQUIPMENT COMPRISING A BARGE, A DIGGING LADDER EXTENDING FROM SAID BARGE AND ADAPTED TO BE LOWERED TO A DEPTH BELOW THE SURFACE OF WATER ON WHICH SAID BARGE MAY BE FLOATING, A CENTRIFUGAL TYPE DREDGE PUMP ON SAID BARGE AND HAVING A SUCTION LINE EXTENDING ALONG AND SUPPORTED BY SAID LADDER, A JET PUMP ASSEMBLY CARRIED BY SAID LADDER AND CONNECTING TO SAID SUCTION LINE, SAID JET PUMP ASSEMBLY INCLUDING JET MEANS OF GENERALLY CYLINDRICAL SHAPE FLOW COUPLED TO SAID SUCTION LINE AND INCLUDING AT LEAST ONE JET IN THE WALL THEREOF, A PRESSURE HOUSING AFFIXED TO SAID DIGGING LADDER AND SURROUNDING SAID JET MEANS AND ENCLOSING SAID JET, MEANS ROTATABLY MOUNTING SAID JET MEANS WITH RESPECT TO SAID SURROUNDING PRESSURE HOUSING, ADDITIONAL PUMP MEANS ON SAID BARGE, MEANS DIRECTING THE OUTPUT OF SAID ADDITIONAL PUMP MEANS ALONG SAID LADDER TO SAID PRESSURE HOUSING TO PRESSURE FEED SAID JET, A CUTTER HEAD AND MEANS COUPLING THE SAME TO THE OUTBOARD END OF SAID JET MEANS, MEANS FOR ROTATING SAID SUCTION LINE AND JET MEANS TO ROTATE SAID CUTTER HEAD WITHOUT INTERRUPTING THE FUNCTIONING OF SAID JET PUMP, AND MEANS FOR RAISING AND LOWERING SAID LADDER.