US3222871A - Method and apparatus for transporting material in a liquid having wave propagation - Google Patents

Description

Dec. 14, 1965 H. F. MILLER ETAL METHOD AND APPARATUS FOR TRANSPORTING MATERI IN A LIQUID HAVING WAVE PROPAGATION 5 Sheets-Sheet 1 Filed May 4, 1962 Dec. 14, 1965 H. F. MILLER ETAL 3,222,871

METHOD AND APPARATUS FOR TRANSPORTING MATERIAL Filed May 4, 1962 IN A LIQUID HAVING WAVE PROPAGATION 5 Sheets-Sheet 2 FIG. Z.

l pl l5 il l i 7 Y 27 23A` L 23 v \1\ zev MM5/ x l Ill 24A 24 Lm w WAVE PROPAGATION lNVENTGRS HENRY F. MILLER THOMAS J. RHODES BY O {({Oxuqrf U". k Gjfe @LM ATTORNEY.

Dec. 14, 1965 H. F. MILLER ETAL 3,222,871

METHOD AND APPARATUS FOR TRANSPORTING MATERIAL IN A LIQUID HAVING WAVE PROPAGATION Filed May 4, 1962 5 Sheets-Sheet 3 Q INVENToRs LL HENRY F. MILLER THOMAS J. RHODES B ,a L s". www

ATTORNEY.

Dec. 14. 1965 H. F. MILLER ETAL 3,222,871

METHOD AND APPARATUS FOR TRANSPORTING MATERIAL IN A LIQUID HAVING WAVE PROPAGATION Filed May 4, 1962 5 Sheets-Sheet 4 INVENTORS HENRY F. MLLER THOMAS J. RHODES Y (D l om?? Ik", loIf''QrsQn ATTORNEY.

Dec. 14, 1965 H. F, MILLER ETAL 3,222,871

METHOD AND APPARATUS FOR TRANSPORTING MATERIAL IN A LIQUID HAVING WAVE PROPAGATION 5 Sheets-Sheet 5 Filed May 4, 1962 INVENTORS HENRY F. MILLER THOMAS J. RHODES ATTORNEY.

3,222,871 METHD AND APPARATUS FOR TRANSPORT- ING MATERHAL IN A LIQUlD HAVING WAVE PROPAGATEN Henry F. Milier, Ciifton, and Thomas J. Rhodes, Smoke Rise, NJ., assignors to United States Rubber Company, New York, NSY., a corporation of New Jersey Filed May 4, i962, Ser. No. 192,504 3 Claims. (Ci. 61-5) This is a continuation-in-part of application Serial No. 178,842.

This invention relates to a method of dredging and to an apparatus therefor. More particularly, this invention relates to a novel device for dredging solid materials located in a bed beneath a liquid, which device utilizes the energy associated with waves propagated in the liquid to sustain its dredging action.

Heretofore numerous attempts have been Ina-de to devise dredging devices whereby large bodies of material beneath a liquid lcan be transported to desired locations. Numerous means have been employed heretofore to accomplish this end such as, for example, pump-actuated pipelines, motor-driven dredging buckets, etc.

However, heretofore none of the various prior-art techniques has been fully satisfactory. Thus, generally prior-art dredging devices have been massive and unwieldy so that it has been ditlicult and expensive to transport such devices. Further, such prior-art devices have been extremely expensive to operate because of the very high power requirements. In addition, the dredging operation can be severely hampered by wave action.

Other dredging devices have been suggested heretofore, which devices rely upon the energy associated with waves to sustain their dredging action. Reference is particularly made to U.S. patent application Serial Number 89,174, tiled February 14, 1961, which application relates in part to such a dredging system. The device utilized comprises horizontal float means and horizontal brake means spaced beneath the float means and provided with a plurality of valves to resist rising through a liquid in which waves are propagated. Wave energy is transmitted from the float means to the brake means, which transmission will, under appropriate conditions, also result in dredging, i.e., provided that the brake means are disposed near the bed beneath the liquid. Although this horizontal type of dredging device has been edective, it has been felt that improved devices could be obtained.

Reference is also made to our U.S. patent application Serial Number 178,842, led on March l2, 1962, entitled Apparatus and Method, describing a novel apaparatus and method for attenuating liquid waves, and utilizing a system of vertical baies to etiect such attenuation. Certain aspects of the apparatus described herein are related to the construction of the apparatus described herein and, accordingly, the contents of such application are hereby incorporated by reference into the present application.

The apparatus described in our aforesaid U.S. patent application Serial No. 178,842 comprises two end baiies and at least one intermediate baie, means for iloatably suspending the baffles substantially vertically in a wavecontaining liquid, and means for anchoring the baffles. Each of the battles is valved to permit liquid dow therethrough in one direction only, and the end baffles are valved to open toward one another. As will be seen, certain of these features are also employed in the present application.

hired States Patent ice It is apparent that a dredging device which is of simple construction, is economical to operate, and can transport large quantities of solid material from one location to another, is highly desirable. Such a device could be used where constant beach erosion is a serious problem. For instance, such a dredging device could be installed offshore so as to nourish the beach by continually supplying sand to the beach area. Such buildup would compensate for any loss of beach sand that would otherwise occur due to the forces of erosion generated by the action of the waves as they beat upon the shoreline. In addition, such a dredging device could be used to dredge channels, to build up artiiicial sandbars offshore so as to thereby provide a bathing area that is shielded from the action of breakers from the sea, etc.

Accordingly, it is an object of our invention to provide a novel method for dredging material.

Another object is to provide a unique device to eilect such dredging.

A further object is to provide a novel dredging device, which device is actuated by energy associated with waves in the liquid in which the device is suspended.

Yet another object is to provide a dredging system which is economical to produce and to operate and which can be used to transport material beneath a liquid from one given location to another.

Additional objects will become apparent hereinafter.

The foregoing objects are achieved by the use of a dredging device of special construction. The device utilizes a bathe or series of battles. The baffle is suspended in the liquid in which the waves are propagated, and generally is disposed either vertically or is inclined at a suitable angle, depending upon the geometry of the bed beneath the liquid, the amount of material to be transported, the desired situs for deposit of the material, etc.

In accordance with our invention, the bathe is so designed and valved that it will permit the passage of liquid, eg., water, therethrough in one direction only. The bathe is oatably suspended in the liquid with the face of the bathe being disposed transversely of the direction of wave movement. The disposition of the baffle in the liquid is such that the valving thereof permits passage of the liquid from the seaward side therethrough and toward the shore but does not permit passage of liquid from the shoreward side therethrough and towards the seat. Floating means are provided for the baiiie so as to insure that the baie will be floatably suspended in the liquid. In addition, anchoring means are provided on both the seaward and shoreward sides of the baiiie so as to maintain the baie in a selected orientation within the liquid, eg., vertically disposed within the liquid, or inclined in the liquid at an appropriate angle.

Where long-period shallow-water waves occur, i.e., wherein the ratio of wave length, a, to mean water depth, l1, is very high \/1 the orbital path of the water becomes highly elliptical; that it, it follows the shape of an ellipse whose major axis is horizontal. This results in a condition where the water is moving toward shore and away therefrom in an essentially horizontal pattern. As a result of this elliptical conguration, the Water advances horizontally toward the shore at the crest of the wave and moves seawardly at a point onehalf wave length away. The horizontal velocities within the wave at these two points are substantially the same but the motions of the water are in opposite directions.

Our dredging device is so constructed that when the crest of a wave passes through the baille and toward the shore there is virtually no obstruction to the liquid flow. However, when the wave trough encounters the baiile (one-half wave length later), the direction of liquid ilow is seaward rather than shoreward, and the valves of the baille are closed. The closed valves prevent liquid from passing therethrough and actually dellect the liquid so that it ilows downward, beneath, and seaward of the baille. Provided that the bottom of the baille is appropriately spaced from the bed of material beneath the liquid, this downward liquid ilow will cause severe agitation oi such material and will actually induce a lifting from the bed of relatively large quantities of material and will maintain such material in suspension. As the next wave crest advances toward the shore, the baille valves are opened so that no impairment to liquid llow shoreward is eilered, and as the liquid ilows through the baille it also transports through the baille those particles of bed material which have been agitated and are in suspension, thereby eilecting a net transport shoreward of such particles.

For a more complete understanding of the nature of our invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of one embodiment of our dredging device, which device comprises a baille iloatably suspended within a wave-containing liquid;

FIG. 2 is a vertical cross-sectional view taken along the line 2 2 of FIG. l;

FIG. 3 is a partial elevational view of the baille and shows the panels and mounting therefor;

FIG. 4 shows an alternate construction and is a partial elevational view of a baille wherein each panel is made up of overlapping components;

FIG. 5 shows another alternate construction and is a partial elevational view of one of the bailles wherein a plurality of holes are provided, with valve ilaps for each hole;

FIG. 6 is a cross-sectional view along the line 6 6 of FIG. 5;

FIG. 7 is a schematic, longitudinal, cross-sectional view through a long-period wave;

FIGS. 8 12 are schematic proiile views of our dredging device and show its operation as a wave passes therethrough;

FIG. 13 is a perspective view of one embodiment of a panel used in our baille and shows a curvature at the lower edge thereof;

FIG. 14 is a perspective view of another embodiment of our panel wherein there is no curvature, the panel being planar;

FIG. l5 is a perspective View of another embodiment of our panel wherein the panel is curved transversely;

FIG. 16 is a perspective View of another embodiment of our panel wherein two portions thereof converge at the center of the panel;

FIG. 17 is a perspective view of a further embodiment of our panel wherein the lower edge is provided with a series of V-notches;

FIG. 18 is a perspective view of yet another embodiment of our panel wherein the lower edge is provided with a series of apertures having helical ridges therein; and

FIG. 19 is a schematic proille view of another embodiment of our invention wherein an oppositely valved baille is employed along with the dredging baille.

One embodiment of our invention is shown in FIG. 1, wherein our dredging device is generally designated by the reference numeral 1t). The dredging device comprises one or more bailles 12, such baille shown suspended in the water by means of buoyant floats 14. As shown in FIG. l, a pair of tloats 14 are provided for the baille 12, one such float 14 being on either side of the baille. Each such iloat 14 is pivotally mounted on horizontal supporting member 16 by means of pivot pin 18 which extends through both supporting member 16 and iloat 14. Supporting member 16 is pivotally mounted on inclined member 20, which member 2i) is provided with 4 a slot 22 whereby the relative depth of baille 12 beneath the water can be controlled and adjusted.

Referring to FIG. 2, which is a cross-sectional view taken along the line 2 2 of FIG. 1, means are shown for pivotally mounting iloats 14 on inclined member 20. These means include ilanged cylinder 23, flanged sleeve 24, screw 25, and washer 27. Flanged cylinder 23 bears internal threads 23A. Flanged sleeve 24 is slidably mounted on the cylindrical portion of flanged cylinder 23. Screw 25 contains external threads 25A which engage with matched internal threads 23A. In order to iirmly clamp supporting member 16 to inclined member 20 at a selected position in slot 22, screw 25 is simply tightened, whereupon Washer 27 is biased against sleeve 24 so that ilanges 24A and 23B are forced toward one another and hence tightly grip inclined member 20 at the edges of the slot.

Batlle 12 contains one or more rectangular panels 26, each of which is pivotally mounted to a substantially rigid member 28, e.g., a tube, rod or the like, which extends transversely of the dredging device 10. It will be seen that members 20 in conjunction with transverse members 28 deiined a grid type structure, as shown in FIG. 3.

Panels 26 may conveniently be made of a relatively rigid or still material, certain types of plastics being particularly suitable, e.g., plastic sheetings or moldings made of ABS polymer, e.g., a blend of rubbery butadieneacrylonitrile copolymer with resinous styrene-acrylonitrile copolymer as disclosed in U.S. Patent No. 2,439,202, graft polymers formed by grafting styrene and acrylonitrile onto polybutadiene, etc.

Such panels 26 are desirably molded so as to have a cavity at the top thereof, through which cavity extends member 28 (FIG. 3). This method of securing panel 26 to member 28 insures a freely pivoting action whereby the panel will readily respond to any water motion. In order to promote a prompt response, eg., a snapping action downward, of the panel 26, e.g., when a wave trough is passing, there may be secured to the bottom (free) edge 30 of each such panel a weighted strip 32.

Where the Width of our dredging device is relatively great, the construction shown in FIG. 4 may be used, wherein several panel segments are utilized rather than single panel 26. In this construction, successive panel segments are alternately overlapped and underlapped so that the vertical edges 36 of a given panel segment 34 are overlapped by the edges 38 of adjacent panel segments 34', etc. Successive rows of panel segments can be staggered as shown.

In general, the bailles should oiler, in their open position, the maximum possible void area for passage of liquid therethrough, so as to give our device an overall eillciency. From a consideration of FIGS. 1 and 3, it will be seen that when the panels 26 of a baille are displaced outward by the action of a wave, the void area approaches since the only impediments to liquid flow are the members 28 on which the panels are mounted, the panel material disposed therearound, and the submerged portions of the iloat system and of inclined members 20. Accordingly, the eiliciency of the system is virtually the optimum attainable. Since each panel 26 is itself a thin strip of substantially rigid material, it will readily hinge and pivot away from its stop position when any force is exerted on it by a liquid pressing against it in a direction to swing or pivot the panel 26 away from the member 28 on which the lower (free) edge 30 of the panel rests and overlaps. However, when the liquid ilows in the opposite direction, it forces the panel 26 to pivot downward to a position such that its lower (free) edge overlaps and presses against member 2S, so that when all the panels 26 are in such position the baille is closed.

In accordance with another embodiment of our invention, a baille 12 may be substituted for paneled baille 12. Each such baille 12 comprises a sheet 4i) provided with a multiplicity of holes 42 therethrough (FIGS. 5 and 6). Preferably, the sheet 4t? is made of segments of coated fabric of convenient length. At each side the perforated sheet 40 is folded over and secured, e.g., cemented, heat sealed, or stitched to itself, to form a pocket 44 in which is placed a member 46 which may be rigid, e.g., a rod, or flexible, eg., a cord or the like. As shown in FIG. 5, the adjacent rods 46 in adjacent pockets 44 are butted and tied together.

In order to impart transverse reinforcement to the sheet 4t), a plurality of rods 48 are mounted horizontally to the sheet so as to form a grid-type structure with rods 46. As shown in FIGS. 5 and 6, each such rod 48 passes through a pocket Si), and also is secured to rods 46.

Although the perforated baille 12 is made from a material impervious to water, it is provided with a multiplicity of holes 42 therethrough, in order to enable the water to pass therethrough.

Additionally, means are attached to each baille 1.2. to enable the baille to restrict passage of Water therethrough in one direction, but to permit the water to ilow readily through each baille in the opposite direction. These means may desirably comprise tlapper strips 52 which are arranged to overlie holes 42 at least partially. In the embodiment illustrated in FIGS. 5 and 6, ilapper strips 52 are narrow rectangular strips of coated fabric which cover holes 42 completely in a shingle-like fashion. Each flapper strip is attached along its upper edge 54, as by heat sealing, stitching, or the like to the perforated bafe, while the sides and the lower edge are left free.

Since the ilapper strips 52 are themselves thin flexible sheets of coated fabric, they will hinge and bend away from the perforated baflle when any force is exerted on them by liquid passing through the holes in a direction that lifts the strips S2 away from the perforated sheets; when the liquid moves in the opposite direction, it will force the lapper strips 52 flat against the perforated sheets, thereby to close the holes therein. Thus, each of the thin flexible flapper strips 52 is affixed along an upper edge 54 to the baille and is `adapted to overlie a hole 4?. when arranged llat against the sheet.

Referring again to FIG. 1, lloats 14 are attached to the baille at some point above the panels 26 and thereby maintain the baille suspended in the water in an inclined or in a vertical position. Any suitable floating means may be employed. For example, each float 14 may simply be a large, sealed container. Alternatively such lloat may be made of an imperforate, unicellular, eg., closedcell, expanded elastomer having a specific gravity less than one.

The buoyance provided by the float must be sufllciently great that the baflle supported thereby will follow the vertical wave displacement virtually instantaneously. This is best attained by designing the float to cover a relatively large Water surface area as shown in FIG. 1.

Means to anchor the baille on both the seaWard and shoreward side are provided. The anchoring means desirably comprises an array of long tie ropes 56 and 57 fastened to anchors 58 set in the bottom. Tie lines 56 are secured to the baille by being tied to lug 59 mounted at the top of inclined member Ztl, and tie lines 57 are secured to a lower part of the baflle by being fastened to a lug 6@ mounted on inclined member Ztl.

Referring to FIG. l, it will be seen that the panels 26 are so arranged on the baille 1.2 that they open when the motion of the water is in the direction of the shore, and close when the motion of the water is in the direction of the sea.

Referring to FIG. 7, there is shown a schematic, longitudinal cross-sectional view through a long-period wave. The ellipses represent the orbital paths described by individual particles at various depths. The Wave energy is distributed throughout the entire water depth. As a result, particles at the bottom describe a linear path whereas particles at lesser depths describe elliptical paths. The paths of all particles within any particular vertical crosssection will describe confocal ellipses. During the time required for one complete wave length to pass a given vertical cross-section, e.g., section AA, any individual particle will have traversed one complete elliptical orbit. Assuming that a baille is located in the plane A-A and valved to open shoreward as shown by the dotted line, the panels will be Wide open (position O) when the crest passes through plane A-A, and will be completely closed (position C) when the trough passes plane A-A (one-half wave length later).

Referring to the dredging device shown in FIG. l, its operation is best understood by a consideration of FIGS. 8-12, which `schematically illustrate its dredging action as successive waves pass therethrough and toward the shore. (The anchoring lines are not shown.) FIG. 8 represents the dredging device anchored in position and at rest in the water, no waves having been encountered, and the bed 62 of material, eg., sand, silt, etc. not yet having been subjected to dredging and hence being comparatively flat.

As a Wave crest advances shoreward and reaches the dredging device (FIG. 9), the direction of water flow is also shoreward (FIG. 7 so that panels 26 open effortlessly, and water flows through the baffle. As the Wave trough then advances to the dredging device (FIG. 10), the direction of Water flow is seaward rather than shoreward (FIG. 7), and the panels close. Since the stream of water impinging upon the closed panels cannot pass seawardly through the closed panels, it is deilected downward and beneath the baffle and then passes to the seaward side thereof. The water velocities associated with the Wave motion are considerable, so that this dellected stream of Water exerts great agitation on particles 64 in the bed 62, and actually lifts these particles and maintains them in suspension above the bed seaward of the baffle (FIG. 9).

As the next successive Wave crest advances to the dredging device (FIG. 11) the direction of water flow is again shoreward, so that the panels Z6 again swing open. As the water passes through the baille the water :carries `with .it all of the suspended particles 64, and deposits such particles in a zone 66 which is markedly closer to shore than the zone 63 in which the particles were originally located.

Upon permitting the dredging device to continue to encounter successive waves over a period of time, a remarkable quantity of material can be transported from its original zone 68 and deposited shoreward thereof in a zone 66, to actually build up a deposit of appreciable proportions (FIG. ll).

It will be obvious from FIGS. 8, l0 and 12 that the spacing between the bottom edge 76 of the lowest panel 26 and the surface 72 of the bed 62 will affect the dredging operation. This spacing can be controlled and adjusted as desired by simply adjusting the relative position of the slot 22 with respect to horizontal member 16.

In addition, the relative orientation of the baille 12 in the water will also affect the dredging efiiciency. In certain instances it is desirable that the baille be disposed substantially vertically, e.g., when commencing the dredging. In other instances, better results are obtained when the baffle is inclined with the bottom thereof nearer the shore (as shown in FIGS. 8-12), e.g.., after the dredging is well underway, Where the particular geometry of the bed renders such orientation advisable, etc. The appropriate battle orientation is readily secured and maintained by means of either tie ropes 56 or 57 or both.

From a consideration of FIG. 12 it will be apparent that at some point the distance between the bottom panel edge 76 and the surface 72 of the bed becomes so great that the agitation of particles in the bed by the water stream is relatively small, whereupon the ethciency of the dredge is minimal. At such time the baille can either be lowered by recourse to slot 22 or, alternatively, the dredge can be moved seaward an appropriate distance and the whole operation can be then commenced anew. Such seaward positioning is readily obtained by appropriate adjustment of tie ropes 56 and 57.

From the preceding, it will be seen that our invention readily lends itself to the use of a series of our dredging devices appropriately spaced from one another, whereby the most seaward dredge will transport material thereunder to a more shoreward zone, the dredge adjacent to such most seaward dredge will transport material thereunder (and material transported thereto by the most seaward dredge) to a still more shoreward zone, etc.

Referring again to FIGS. 8-12, it will be seen that each panel 26 is slightly curved at the bottom part thereof. (See also FIG. 12.) We have found this construction desirable in that it appears to promote the piling up of the material on the shoreward side of the baille.

The simpler straight or planar panel (FIG. 14) can, of course, also be used and very satisfactory results are obtained.

Other alternative panel constructions are illustrated in FIGS. 15-18. Where it is desired to dredge a channel or the like, either of plow type constructions shown in FIGS. 15 and 16 is particularly suitable. Utilizing such a construction, material in the bed will be pushed to the sides of the panel, thereby effectively dredging a channel.

FIGS. 17 and 18 illustrate two additional embodiments wherein the panel is so designed as to induce additional turbulence in the water stream passing thereunder. Thus, FIG. 17 shows a panel wherein the lower (free) edge has been V-notched, whereas in FIG. 18 the free edge has been provided with a series of helically ridged apertures. In the former instance the V-notches will promote additional swirling and turbulence as the water passes through the notch and beneath the panel. Similarly, in the latter instance the helically ridged apertures will promote actual water vortexes and thereby increase the agitation.

The anchoring loads will depend upon the number of panels used. For example, for a given baille if the panels extend through the entire water depth the anchoring loads will be appreciable on the shoreward side, since the closed panel area will be considerable. However, if panels are used only at and near the bottom of the baille as shown in FIG. 1, the anchoring loads are considerably reduced because water ilowing seaward will impinge on a much smaller total panel area.

In accordance with yet another embodiment of our invention, we have found that the anchoring loads can be markedly reduced by incorporating one or more bailles shoreward of the one or more dredging bafiles, which shoreward baille(s) is valved seawardly, so as to permit the passage of liquid therethrough in a seaward direction but to prevent passage of liquid therethrough in a shoreward direction. This embodiment is schematically illustrated in FIG. 19.

The seawardly valved shoreward baille 76 may be constructed in a similar manner as dredging baille 12, although its depth is not so great since it is not serving as a dredge but merely to reduce the anchoring loads on the shoreward tie ropes 56 and 57 secured to the shoreward baille. Shoreward baille 76 is secured to dredge baille 12 both at or near the water line and at or near the bottom by means of tie lines 78. As is fully explained in our application Serial No. 178,842, iiled March 12, 1962, provision of a pair of oppositely valved bailles, in instance bailles 12 and 76, causes a damping or attenuation of waves as they pass therethrough and toward the shore. Shoreward baille 76 thus cooperates with dredge baille 12 so as to eilect a degree of attenuation, and its presence substantially reduces the mooring loads on the shoreward tie ropes 56 and S7 of shoreward baille 76.

The following example will further illustrate our invention.

EXAMPLE A baille similar to that shown in FIG. l was constructed. This baille contained two panels 26 made of relatively rigid plastic (Royalite). Each panel was 16S/s inches wide, 3%; inches deep, and l/l inch thick. The panels were slightly curved at the free edge thereof as shown in FIG. 8. The panels were mounted on stainless steel rods 28 as shown in FlG. 1. Each such rod was connected at the ends thereof to inclined member 20, which member was 1/2 inch wide. The spacing between members 20 was 163/4 inches, so that the panels could swing freely. Rods 28 were spaced 2% inches from each other so that each panel pivotally mounted on one such rod would, when vertically inclined, have its lower side abut and rest against the next lower rod 28. A pair of iloats 14 were secured to the baille as shown in FIG. l. The iloat was made of Ensolite brand extended elastomer. Each float was 18 inches long, 161K? inches wide, and 3 inches deep. To the lower edge of each panel was secured a thin GAO inch) strip of lead, whereby to insure a prompt snapping action of the panel.

The wave channel in which our baille was used consisted of a transparent, steel reinforced basin 3i) feet in length, 27 inches deep, and 18 inches wide. A sand layer 3 inches in depth was evenly distributed over the bottom of the channel. The still water depth in the channel was maintained at 16% inches as measured from the bottom of the channel. Waves were generated by a bottom-hinged, ilat plate wave generator driven by a pneumatic servo motor. The generator was 17% inches wide and 32 inches deep, so that the top thereof extended above r the channel. Wave conditions could be altered by means of a pressure regulator, ilow control valves and proximity switches (not shown). Perforated wooden block wave absorbers were located at each end of the channel to minimize wave reilections from the ends of the channel. The baille was held in substantially vertical position by wires 56 and 57 attached to lugs 59 and 6i).

Initially the bottom of the baille, that is, the free edge of the lowest panel 26, was suspen-ded about 3 and 1/2 inches above the three-inch layer of sand. The distance from the water line to the bottom edge of the lowest panel was 9% inches. The wave generator was then turned on and waves having a wave length of 9.4 feet and an amplitude, a, of three inches, were propagated. Note that when the ilrst trough comes through, the distance from the free edge 70 of the lowest panel 26 to the bed 72 is one-half inch. As the generated waves pass through the dredging baille one could visually observe the dredging of sand. That is, particles of sand were picked up by the water stream ilowing down the shoreward side of the baille, beneath it, and seaward thereof. These particles were highly agitated by the water stream and were held in suspension until the crest of the next wave passed through the dredge baille, whereupon the suspended sand was also transported through the baille openings and deposited shorewardly of the baille. During the course of about eight hours time, the horizontal, vertical, and angular orientations of the baille were varied so as to provide continuous effective dredging. After such time a sand pile 14% inches high and 41/2 feet long was obtained.

It will be apparent from the foregoing that our dredging device is markedly effective in transporting large quantities of solid material from a given location to another desired location.

Naturally, the size of a dredging device constructed in accordance with our invention may vary, depending upon the area to be dredged, the distance which the dredged material is to be transported, the width and depth of the channel to be dredged, the particular water conditions to be encountered, eg., wave length, water depth, wave amplitude, etc.

In one desired application, our dredging device can be disposed relatively close to the shore line, that is, along a relatively shallow zone wherein the bed gradually slopes upwardly toward the shore. The characteristics of shallow-water waves are altered as such Waves advance and `break upon the sloping bed. Accordingly, when 'our device is disposed relatively close to the shore, intead of causing bed material to be lifted and deposited to form a mound immediately shoreward of the device, the sodredged material is actually carried by the breaking wave and is deposited over the sloping beach to thereby build up the beach and compensate for erosion.

Variations can, of course, be made without departing from the spirit of our invention.

Having thus described oui invention, what we desire to secure and claim by Letters Patent is:

1. A dredging device for transporting material beneath a liquid surface from one zone to another, said device being actuated by energy associated with waves propagated in said liquid, said device comprising a oat means, a horizontal support member attached to each side of said float means, an elongate member movably attached to each of said support members and depending into said liquid to a level beyond said lloat means, a baille mounted between the lower ends of said elongated members and spaced from said float means to define an unobstructed passageway therebetween, said baille having a series of openings disposed at different levels in substantially a common plane with pivotally mounted closure means depending from horizontal pivot means at different levels over each of said openings, each of said closure means being larger than said openings and swingable in the same direction from each level of pivot means to uncover said openings so as to permit liquid to ow therethrough in one direction only, said elongate members being pivotally mounted to said horizontal members to fxedly position the baille with said plane of the openings at a selected angle relative to the support members and further being movable vertically relative to said horizontal members to shift the closure means vertically with respect t said iloat means, and said device having inextensible and flexible anchoring lines connected thereto and extended beyond said loat means in opposite directions from said plane of the openings and secured to ilxed anchors provide in the bed of the liquid for positioning said floats on the liquid.

2. The device of claim 1, wherein a series of said baflles are disposed in spaced apart relation from one another and interconnected by inextensible flexible lines for defining, said spacing such that material being transported by one baille is deposited in a zone suillciently close to an adjacent baille to permit said adjacent baille to transport said material to a zone close to a next adjacent baille.

3. A method of dredging material from a pre-selected zone in the bed of a body of water in which waves are propagated, said waves being characterized by having a shoreward ilow of water as the wave crest passes shorewardly over said zone and a seaward ow of water as the wave trough passes shorewardly over said zone, comprismg:

permitting the shoreward llow of water of a rst wave crest to pass immediately above and unimpededly over said zone;

dellecting the seaward iloW of water of the trough irnrnediately following, said rst wave crest rapidly downwardly against said zone and therealong in a path of llow seawardly, thereby to agitate particles of material in said bed and cause said particles to go into suspension in the water immediately seawardly of said zone;

and then permitting the shoreward flow of water associated with the next wave crest to pass immediately above and unimpededly over said zone, thereby to carry said suspended particles shorewardly over said zone and deposit them on the bed shorewardly of said zone.

References Cited by the Examiner UNITED STATES PATENTS 436,644 9/1890 White 61--5 604,810 5/1898 Waddell 61--4 1,080,049 12/1913 Dean 61-4 1,583,132 5/1926 Falley 61-5 2,655,790 10/1953 Daley 61-3 2,658,350 11/1953 Magill 61-5 3,011,316 12/1961 Wilson 61-4 FOREIGN PATENTS 1,203 1860 Great Britain. 1,804 1870 Great Britain. 4,826 1886 Great Britain. 134,874 11/1919 Great Britain. 260,939 2/1927 Great Britain.

EARL J. WITMER, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

Claims (1)

1. A DREDGING DEVICE FOR TRANSPORTING MATERIAL BENEATH A LIQUID SURFACE FROM ONE ZONE TO ANOTHER, SAID DEVICE BEING ACTUATED BY ENERGY ASSOCIATED WITH WAVES PROPAGATED IN SAID LIQUID, SAID DEVICE COMPRISING A FLOAT MEANS, A HORIZONTAL SUPPORT MEMBER ATTACHED TO EACH SIDE OF SAID FLOAT MEANS, AN ELONGATE MEMBER MOVABLY ATTACHED TO EACH OF SAID SUPPORT MEMBERS AND DEPENDING INTO SAID LIQUID TO A LEVEL BEYOND SAID FLOAT MEANS, A BAFFLE MOUNTED BETWEEN THE LOWER ENDS OF SAID ELONGATED MEMBERS AND SPACED FROM SAID FLOAT MEANS TO DEFINE AN UNOBSTRUCTED PASSAGEWAY THEREBETWEEN, SAID BAFFLE HAVING A SERIES OF OPENINGS DISPOSED AT DIFFERENT LEVELS IN SUBSTANTIALLY A COMMON PLANE WITH PIVOTALLY MOUNTED CLOSURE MEANS DEPENDING FROM HORIZONTAL PIVOT MEANS AT DIFFERENT LEVELS OVER EACH OF SAID OPENINGS, EACH OF SAID CLOSURE MEANS BEING LARGER THAN SAID OPENINGS AND SWINGABLE IN THE SAME DIRECTION FROM EACH LEVEL OF PIVOT MEANS TO UNCOVER SAID OPENINGS SO AS TO PERMIT LIQUID TO FLOW THERETHROUGH IN ONE DIRECTION ONLY, SAID ELONGATE MEMBERS BEING PIVOT-

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