US3307278A

US3307278A - Sonic dredging process and apparatus

Info

Publication number: US3307278A
Authority: US
Inventors: Jr Albert G Bodine
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-08-01
Filing date: 1964-11-24
Publication date: 1967-03-07
Anticipated expiration: 1984-03-07

Description

March 7, 1967 A. G. BODINE, JR 3,307,278

SONIC DREDGING PROCESS AND APPARATUS Filed Nov. 24, 1964 4 Sheets-Sheet 1 March '7, 1967 A. G. BOBINE, .IR 3,307,278

SONIC DREDGING PROCESS AND APPARATUS i A Filed Nov. 24, 1964 4 sheets-Sheena I Il I1: lf. l1 P so I 2 k: 8l

IN VENTOR.

March 7, 1967 A. G. BOBINE, JR

SONIC DREDGING PROCESS AND APPARATUS 4 Sheets-Sheet 5 Filed Nov. 2,4,` 1964 March 7, l967 A. G. BOBINE, JR 3,307,278

SONIC DREDGING PROCESS AND APPARATUS Filed Nov. 24, 1964 4 Sheets-Sheet 4 INVENTOR.

United States Patent Office Patented Mar. 7, 1967 3,307,278 SONIC DREDGING PROCESS AND APPARATUS Albert G. Bodine, Jr., 7877 Woodley Ave., Los Angeles, Calif. 91406 Filed Nov. 24, 1964, Ser. No. 413,495 21 Claims. (Cl. 37-195) This application is a continuation-in-part of my prior copending application Serial No. 299,209, filed August 1, 1963, now Patent No. 3,189,536, and of my parent application Serial No. 739,291, filed June 2, 1958, now Patent No. 3,123,546, of which said application Serial No. 299,209 was a continuation-in-part.

This invention relates generally to methods and apparatus for dredging the bottoms of bodies of Water, such as lakes, harbors, rivers, etc., by application of one or more sonic principles. These sonic principles involve elastic vibrations in elastically vibratory systems, the transmission of elastic waves or Vibrations therein or therealong, sonic phenomena occurring between two sonic wave transmission media, vibrations in the basi-c apparatus at resonant frequency and the effects of these sonic phenomena on earthern materials Worked on in dredging, both before and after separation thereof from the bottom or banks holding the body of water. The general object of the invention is to provide improved methods and apparatus for dredging, relying upon effects gained through use of such sonic principles.

In accordance with the invention, a sonic elastically vibratory action is applied to a shoe, cutter or bit member which is positioned adjacent or engageable with the earth at the bottom of the Water. In a preferred form of the invention, the bit member is carried at the lower end of a dredge tube which participates in the sonic, elastic vibrations. standing wave vibration is set up in the dredge tube, This vibration in and along the dredge tube keeps the dredge solid material in suspension in the water present, and acts also to reduce the friction at the walls of the tube so as to facilitate flow of the mixture of dredged solid material and water up the tube.

In addition,the sonic vibratory action transmitted down the dredge tube is applied to vibrate the shoe or bit at the bottom. Here the shoe or bit applies the sonic energy to the earth material to accomplish any one or all of several results, such as cutting and/or fracturing earth material loose from the bottom, and stirring up such separated earth material, and/or already loosened earth material, overburden, or ore, such that such materials become suspended in the water, and thus available or accessible for transmission up the dredge tube. The invention includes as an important step or feature the establishment of a cir-culatory'ow stream of water up the dredge tube, so as to carry up the loosened particles of earth material or ore.

The sonic vibratory action is very effective in stirring and mixing the earth material and water. Sonic waves are transmitted into the water as well as into the earth material with a resulting violent mixing action that generates a mud slurry capable of being circulated up the dredge tube.

The earth material fatigues and disintegrates rapidly under sonic vibration, helped along by the presence of water, which is cyclically injected and caused to penetrate into the soil, between thesoil parti-cles, so that they rapidly break apart.

Preferably, for example, resonant longitudinal As stated above, the bit or shoe transmits sonic vibratory energy into the water. The resulting sonic vibratory commotion in the water has a violent stirring, cavitating and agitating effect, stirring and sweeping up earth particles, overburden, ore, or newly broken loose or fragmented material, into suspension so as to be picked up by the flow stream going up the dredge tube. This commotion in the water results largely from acoustic coupling of the vibratory bit to the water. In this performance, sound waves are radiated from the bit into the water, not only downwardly but laterally. The sonic action can also be transmitted to the Water from the side walls of the lower region of the dredge tube, especially if there is a substantial component of lateral wave sonic transmission in the tube. The acoustic impedance (defined ratio of vibratory pressure amplitude to velocity amplitude in the media) of the water and the velocity of sound therein are sufficiently close to those of the coupling surfaces on the bit or tube to assure good transmission of acoustic energy into the water. In turn, the sound waves so radiated into the water reach and are transmitted into the earth. A useful phenomenon here is that there are suficient differences between the acoustic impedances and velocities of sound for water and earth media that sonic wave reflections and relative movements and stresses in the media occur, creating a condition highly conducive to disintegration and stirring up of the earth material. The activity can be heightened by driving the system hard enough to cause the vibrations to take place at a suficient amplitude to bring about the violent conditions of cavitation, and such constitutes one preferred practice of the invention.

The conditions described in the preceding paragraph can be brought about with the bit or shoe positioned close to but spaced from the earthen bottom or formation, or with the bit or shoe pressed thereagainst. With the shoe or bit pressed tightly against the virgin earth material or formation, a large flow of sonic vibratory energy goes directly into the earth material or formation, and under these conditions earth material, even hard rock, can be caused to disintegrate rapidly by fatigue failure.

The invention will be further described with reference to the accompanying drawings showing illustrative embodiments thereof, and wherein:

FIG. l is a side elevational View, partly in medial section, showing largely diagrammatically an illustrative embodiment of the invention;

FIG. 2 is a plan view taken in accordance with the arrows 2--2 of FIG. 1;

FIG. 3 is a section on line 3--3 of FIG. 2;

FIG. 4 is a view similar to FIG. 1 but showing a modification;

FIG. 5 is -an end elevational view of the apparatus shown in FIG. 4, looking toward the right in said figure;

FIG. 6 is a transverse section taken on line 6 6 of FIG. 4; and

FIG. 7 is a section taken on line 7-7 of FIG. 6.

Referring first to FIG. 1, the numeral 10 designates generally a dredge barge floating in a body of water 11, and thus forming -a floating platform for the equipment. This body of water stands against an earth bank 12 rising thereabove in the right-hand portion of the picture thereabove, and opposite to bank 12 is an underwater bank 13.

-The banks 12 and 13 defining a channel which has been dredged out and which has a bottom 15. The barge 10 may be equipped with conventional propulsion and maneuvering equipment, not shown.

Erected on barge 1t) is a frame structure 16 rising from a bed frame 17, and the latter has at one end of the barge an overhanging or outwardly projecting bracket 18, formed with an aperture 19 which receives a vertically disposed dredge tube Ztl. The dredge tube 20 is composed of an elastic, elastically vibratory substance, preferably steel. It has fixed to its top end a mounting plate or flange 21 for vibrating generating means designated generally at 22.

The vibration generating means 22 is driven from a drive shaft 24 powered by an internal combustion engine 2S mounted on the frame structure 16.

The upper end portion of dredge tube 20 has an outlet to which is coupled a discharge hose 26 leading to the inlet of a centrifugal pump 27 driven by a small internal combustion engine 23. The pump outlet connects to a discharge pipe 29, which is shown as coupled to a hose 30, discharging on land beyond the bank 12. Alternatively, the hose 341 could of course discharge to another barge, or to a suitable pipeline, or otherwise, as desired. The pump 27 and engine 2S are mounted on a portion 32 of framework 16, as illustrated.

The upper end portion of dredge tube 20 is connected by parallel links 33 to a vertical component 34 of frame structure 16, and these links keep the dredge tube 20 in a generally vertical position.

Vertically positioned tube 20 has fixed thereto the piston 36 of an air spring device 37, the latter comprising, in addition to the piston 36, a cylindrical :piston housing 38 which is mounted on the aforementioned bracket 18. The housing 38 has a lower wall 38a which is apertured to slidingly pass the dredge tube 20, packing being used at 40, as illustrated. Packing 41 seals the piston 36 to the housing 3S. Air under pressure is introduced into the chamber housing 38 by an air line 37a from any suitable source of pressurized air, not shown, and the air pressure maintained inside the chamber of the air spring will be understood to be such as will counterbalance all or a predetermined proportion of the weight of the dredge tube 20 and other parts mounted thereon. This air spring 37 cushions the dredge tube, and isolates its vibration from the barge.

The dredge tube 20 extends downwardly through the body of water nearly to the bottom where the dredging operation is to be carried out. Surrounding the dredge tube 2t?, with annular clearance, as shown, is a jacket pipe 44, and screwed to the lower end thereof is a shoe, cutter or bit member 46 which is engageable with the earth material at the bottom, and also, in this embodiment of the invention, is engageable laterally with the bank 13 for cutting away of the latter. Acoustically speaking, this member 46 constitutes a sonic wave coupler and radiator. The details of this particular illustrative member 46 will be described hereinafter. i

The lower end of dredge tube 2t) has an external annular flange 47, which is received between internal

annular flanges

48 and 49 secured inside the l-ower end portion of the jacket pipe 44. Near the upper end of jacket pipe 44 said pipe has an internal annular ange 50 which is spaced slightly from pipe 2t) and which functions as a centering means or guide. At the upper end, the jacket pipe 44 has an inwardly turned ange 51 which is close spaced to the tu-be 2t).

Mounted inside dredge tube 2t) is a long venturi tube 52, the lower end portion of which is disposed closely adjacent the bit member 46, and is welded inside the flange 49. The upper end of venturi tube 52 is well up the dredge tube 26, and is welded thereto as at 52a.

The drive shaft 24 extends from engine 25 into suitable bearings 55 within a gear case `60, and carries inside case 60 a spur gear 61. On the other side of gear case 60, the shaft extends through

universal joints

62 and 63 to a vibration generator unit 22a forming one component of the generating means 22. Spur gear 61 meshes with a second spur gear 64 in gear case 60, and the latter is on a shaft 66 which extends through universal joints 67 and 68 to the second vibration generator unit 2lb of the generating means 22. The two generator units 22a and 2211 may be identical and a detailed description of one will suffice for both. The generator 22a has 4a housing 70 made up of an intermediate block 71 and two

end caps

72 and 73, together with a spacer 74 lbetween 4block 71 and cap 73, said members being of rectangular shape as seen in the aspect of FiG. 3.

The members 71 to 74 are secured in assembly with one another by bolts 72a. A bore 75 extends through block 71 `and is continued a short distance into end cap 72. and spacer 74. Mounted on this bore 75 is a hard steei raceway cylinder 76, in which is a cylindrical raceway bore 77. Washers 78 are preferably used in end cap 72 and spacer 74 at the ends of the cylinder 76. Cylinder 76 and washers 78 thus define a cylindrical raceway for a hardened steel cylindrical inertia roller 80, which is of somewhat lesser diameter than the internal diameter' of lbore 77, and is adapted to roll around the inside of the bearing surface defining said bore 77.

Inertia roller 80 has an axial bore 81 which rotatably receives an axle 82 projecting axially from a spur gear S4. The pitch circle of gear 84 corresponds to the diante' eter of inertia roller 80, and this gear 84 meshes with a stationary internal gear 86 which is formed in the aforementioned spacer member 74. The internal gear 86 has a pitch circle corresponding with raceway bore 77.

Projecting from spur gear 84 is a cup SSin which is `formed an internal gear 89, and this internal gear 89 meshes with a spur gear 96 on the end of drive sha-ft 24 the latter being journaled in the hub 92 of end Gap 73`J coaxially with raceway 77 The inertia roller S0 will be understood to fit closely but with working clearance within the overlapping portions of the washers 78. In operation, inertia roller 80 rolls around raceway bearing surface 77, and is held in engagement therewith by centrifugal force. While the generator is at rest, or coming up to speed, the roller S0 is maintained in close adjacency to bearing surface 77 by means of inter-engaging conical axial projections g4' and 95 on the gears 84 and 90, respectively.

Operation is as follows: Rotation of shaft 24 turns the spur gear 90, which, being in engagement with inl' ternal gear 8% on one side, causes rotation of the latter, The gear 84 integra-l with the thus-driven gear 89 is1 int mesh with internal gear 86, and when driven, rolls around the inside of gear 86. Inertia roller 80 is thereby caused to roll around the inside of cylindrical bearing surface 77. As mentioned, when the genera-tor is up to speed, Cen trifugal force developed by the rotation of the krol-ler gti causes it to bear with considerable pressure against the bearing surface 77, and a substantially non-slipping, roll-v ing engagement is thereby attained. As will appear, roller Sti rolls `around the inside of cylindrical bearing surface 77 substantia-lly in step with the rolling of the spur gear 84 around the internal gear S6. Any tendency for roller St) to describe this orbital path with a different rate of rotation on its axis from the ,rotation of spur gear 84 on the axis of the latter is accommodated by a slight rotation of roller 30 on the axle 32.

The centrifugal force developed by the relatively heavy inertia roller 86 rolling in its orbital path around the inside of bearing or raceway 76 results in exertion of a substantial gyratory force on Vthe vibrator housing 70. This gyratory force is transmitted from the generator housing 76 to the platform 21 on the upper end of dredge tube 2t). In View of the fact that there are two of the generator units 22a and 22h mounted on the platform 21, two gyratory force outputs are transmitted from the two generators to the platform 21, and the net effect on the platform 21 depends upon the phase relationship of the inertia roll ers Sti of the two generator units. Since the drive shafts 4 and 66 for the two generator units are geared together to turn in opposite directions, the inertia rollers 80 roll around their respective raceways in opposite directions, as indicated by the `arrows in FIG. 3. In addition, in the illustrative embodiment, the rollers 80 may be so phased as to move vertically in unison or in step with one another, but laterally in opposition to one another. Accordingly, lateral components of centrifugal force generated by the two inertia rollers 80 are cancelled out, whereas longitudinal or vertical components are additive. In net result, a vertically oriented alternating output force, such as indicated by the double headed arrow f in FIG. 3, is applied by the two generator units 22a and 22h to the platform 21 and therefore to the upper end of the dredge tube 20.

The sonic wave or vibration generating means 22 composed of the

units

22a and 22b is driven by engine 25 at a speed to generate its alternating output force at a frequency at which a longitudinal, resonant, elastic standing wave is set `up in the dredge tube 20, to the upper end of which this alternating output force is applied, in a vertical direction, as just explained. The generating means 22 will generate a half-wavelength longitudinal standing wave in the tube 20 if its frequency is made substantially equal to S/ 2L, where S is the speed of sound in the material of the tube and L is its equivalent length. Such halfwavelength standing wave operation is the fundamental mode of operation, and is preferred, though harmonic frequencies may be employed if desired. Assuming, however, the half-wave mode of standing wave vibration, the tube 20, under the influence of the alternating force impulses exerted on its upper end, alternately elastically elongates and contracts. The center region stands nearly sta tionary, the wave at this point having a node or pseudonode. The upper and lower end portions of the dredge tube, on the other hand, vibrate through magnified displacement distances, and these regions of the wave are known as velocity antinodes. A half-wavelength longitudinal standing wave pattern of the kind here referred to is depicted at W in FIG. 4 showing a modified apparatus. The housings of the

vibration generator units

22a and 22b will be seen to vibrate vertically at the amplitude encountered at the upper velocity antinode. Obviously, this vibration cannot be transmitted back through the

shafts

24 and 66 to the gear housing 60 because of the universal joints in said shafts, though said shafts do swing vertically with the generator housings, accommodated by th universal joints therein.

It'is in some cases desirable to cause the dredge tube to vibrate wit-h a lateral component of vibration. This can be accomplished with the present apparatus by omitting one of the

generator units

22a or 22b, or making the inertia roller 80 of one of the units more massive than that in the other. Alternatively, the phasing of the two inertia rollers 86 can be adjusted for a lateral Wave output, in a known manner. The vibrations transmitted in the dredge tube will then have components both longitudinally and laterally of the dredge tube. Moreover, the frequency can be chosen for resonant standing wave vibration in either the longitudinal mode, as before, or in the lateral mode. The lateral mode is effective for transmitting sonic action into the water.

In effect, the shoe or bit 46 is on the lower extremity of the elastically vibrating dredge tube 20, at the point of the lower velocity antinode therein, and vibrates with this low-er extremity of the dredge tube. Usually, the principal mode of vibration is longitudinal, and this vibration of the shoe or bit 46 is then vertical. This vibration may take place with the .shoe or bit 46 on bottom, as illustrated, or separated a short distance above bottom, though ordinarily, the bit 46 is held firmly against the bottom. In addition to thus vibrating vertically against bottom, or closely adjacent thereto, the bit 46 is preferably given a slow oscillation about a vertical axis through a predetermined arc of travel. This may be accomplished by a rod 96 pivotally connected at one end to a pin 97 set into and projecting laterally from one side of jacket 44, and having at its opposite end an eccentric strap 98 surrounding an eccentric 99 driven from a small internal combustion engine E.

The bit, in the present illustrative embodiment, comprises a lower end formed by downwardly directed bit teeth 46. The throw of the eccentric 99 is preferably made such that the teeth 46 will work back and forth over the surface of the earth material or rock structure below them. The stroke should be at least equal to the distance between adjacent teeth.

In addition, in the preferred embodiment here illustrated, the bit 46 is formed with an exterior bellows-shape comprised of alternating circular ridges 46c and depressions 46d. These ridges and depressions have two separate functions, first, to work against the bank and cut material therefromV while undergoing the previously described vertical vibration, and, second, as acoustic coupling means to the surrounding water. The vertically projected area of the bellows formations will be understood to act as sonic wave radiators, radiating acoustic energy into the surrounding water. Because of the angular disposition of these formations, this acoustic agitation also is directed somewhat angularly outwardly from the bit 46. The projected downwardly facing surfaces including the areas between the bit teeth at the bottom of the bit also act as acoustic coupling means to the water and as sonic energy radiation means, and sonic radiation occurs from these surfaces whether or not the bit is in engagement with the bottom 1S.

In dredging service, the shoe or bit 46 on the lower end of the dredge tube 20 is positioned usually firmly against the bottom structure 15, taking advantage of at least a part of the weight of the jacket 44, the dredge tube 20 itself, and the generator means 22 mounted at the top. All or part of this weight can of course be counterbalanced by air pressure inside air spring 37. Thus, sufficient air pressure can be built up inside the chamber of the air spring to counterbalance the entire weight of the dredge tube and parts mounted thereon, so that, for example, the dredge tube can be supported with its bit olf bottom. T-he air spring, in this aspect, may be regarded as representative of a means for vertical positioning of the dredge tube. It will thus be clear that the air spring does afford a means for raising or lowering the dredge tube, and it will be evident to those skilled in the art how, by suitable, easily contrived reorganization, greater range of vertical movement can be achieved. It will also be clear that a larger range of vertical movement may be readily provided by incorporating suitable elevator means in the dredge tube supporting structure. For example, t-he whole supporting frame structure, or any necessary subcomponent thereof, can readily be provided with means for vertical adjustment. Such arrangements, being readily understood and well within the skill of the art, will not be necessary to be further illustrated or described herein. It will further be understood that, in practice, dredge tubes of different lengths may be provided and used interchangeably iin the apparatus, according to the necessary dredging depths in any given practical situation.

With this understanding, it will be clear that, using such facilities or methods as referred to, the dredge tube is rst positioned into the desired proximity to the bottom 15, and normally, or ordinarily, this involves actual forcible mechanical engagement with the bottom. Further, the quantity of air delivered into the air spring and the pressure established therein is usually, or preferably, such as to counterbalance a desirable share of the weight of the dredge tube and parts mounted thereon, so as to attain the desired position or force of the bit on bottom. With such conditions established, the vibratory dredge tube 20 is partially supported by the cushion of air contained in the air spring, and the vibration of the dredge tube thus is well isolated from the frame platform.

The apparatus being thus positioned, and the ygenerator means 22 being in operation, the longitudinal standing wave is set up in the dredge tube 20, causing the bit 46 to vibrate vertically on bottom 15. Several advantageous performances are attained. First, the shoe or bit vibrating against bottom structure or formation 15 sets the latter into sonic vibration at an amplitude of the same approximate order as the bit. This sonic vibration causes the earth material to fatigue and disintegrate rapidly. Moreover, this fatigue and disintegration process is promoted by the presence of the water, which, because of acoustic coupling to the vibratory bit, is subject to cyclic oscillation and thus cyclically injected and caused to penetrate into the soil, between the soil particles, so -as to force them to break apart. This fracturing effect, by fatigue action, is particularly promoted when the bit is forced very tightly against the formation, so that when fatigue action and disintegration are particularly desired, the process will generally consist in or include the step of maintaining the shoe or bit forcibly against the bottom formation. Further, the sonic energy applied to the formation has the effect of stirring up such separated earth material, -and/or already loosened earth material, overburden, or ore, such that such materials become suspended in the water, and thus available or accessible for transmission up the dredge tube. This stirring up and suspension action is further very importantly promoted by sonic wave commotion or vibration in the water around the shoe or bit and the bottom formation or loose material thereon. Such sound wave commotion or vibration results, of course, from acoustic coupling of the shoe or bit to the water and such coupling takes place from the downwardly and laterally facing formations on the bit, such as th-e annular downwardly and -outwardly facing bellows surfaces 46e, and such as the downwardly facing edge surfaces between the bottom engaging bit teeth 46a and 46h. Of course, such sound wave radiation into the water takes place irrespective of whether the -bit is in engagement with the bottom. Accordingly, one process in accordance with the invention is to operate with the bit slightly off bottom, relying upon the sound wave radiation into the water and loose earth material on bottom to stir up such material yand carry it into suspension in the water so that it can be readily picked up and circulated up the dredge tube.

The above described lateral sonic vibration of the dredge tube, when used, is especially beneficial if the dredge is progressed along the bottom of the body of water. Here the sonic action may be radiated effectively against the ledge or bank 13 so as to cut and mix sonically in a forward direction as the barge progresses along.

To accomplish good transmission of `acoustic vibratory energy from the vibr-ation generating means 22 at the top of the dredge tube to the formation at the bottom, and to the water surrounding the shoe or bit, requires that consideration be given to the matter of acoustic impedance in the equipment. Acoustic impedance is defined as the ratio of the magnitude of cyclic force amplitude to cyclic displacement velocity, and it is first of all important that the generator means be designed to have an acoustic impedance which is comparable with that of the vibratory dredge tube 2t) at the point of coupling therebetween. It will of course be readily apparent that a steel tubing, such as the dredge tube 20, will have a large acoustic impedance, since a large axial force must be applied to such a tube to elastically compress it and move its upper end axially through a short displacement distance. A vibration generating means of comparable acoustic impedance is mandatory if good energy transmission is to be accomplished from the generator into the dredge tube. Acoustic generator units of the type herein provided are admirably suited to this application, since they comprise a relatively large mass which moves a short displacement distance but with high force when coupled to the system to be vibrated thereby. In brief,

.earth material.

8 the requirement that the vibration generating lme-ans and the dredge tube have output and input impedances, respectively, which are of the sarne order, is well satisfied by the particular generating means herein disclosed for present illustrative purposes.

Second, it is also of importance that the output imped ance of the vibratory system, at the point of coupling with the earthen formation, have a magnitude of the `same order as that of the earthen structure to be vibrated. The output impedance of the bit on the lower end of the dredge tube Zt is of an order of magnitude sufficiently matched to earthen rock structure to assure effective transmission of acoustic energy from the bit into the formation.

The output impedance at the bit, however, is of somewhat greater magnitude than the impedance of the water to which the bit is acoustically coupled, though the differences in impedance are not so great las to prevent good radiation of acoustic energy into the water. Large wave radiation into the water immediately surrounding and under the bit is thus accomplished, and this vibratory sonic energy in the water is very effective in promoting the agitation, stirring and sweeping up of the loose accumulation of earth material on the rock bottom 15, so that such material goes into suspension. Final-ly, the sound waves radiated from the shoe or bit into the water reach and are transmitted into the earth. There are sufficient differences between the acoustic impedances and velocities of sound for water and earth media that sonic wave refiections and relative movements and stresses in the media occur, particularly at the interface between the water and the earth. These conditions create a condition highly conducive to disintegration and stirring up of the The sonic vibrations are heightened by driving the system hard enough to cause the vibrations to take place at an amplitude great enough to cause sonic cavitation, causing an even greater order of agitation, stirring up, and breaking up of the earth material, all to the end of bringing such material into suspension in the water.

By the practices of the invention, a violent stirring and mixing action is produced that generates a mud slurry capable of being circulated up the dredge tube. When this slurry has been produced, it is circulated up the dredge tube by operation of centrifugal pump 27, as previously described. An increasein flow velocity obtained by use of the venturi tube 52 aids in keeping the ymaterial in suspension. Thus, broadly, the invention comprises the use of acoustic waves for stirring up of earthen material into the water, and then the pumping of the resulting slurry up the dredge tube.

With further reference to the venturi tube 52, which is an optional but preferred feature, when this tube is used, it elastically elongates and contracts with the portion of the dredge tube 20 within which it is welded, both top and bottom. it accordingly becomes a Iunitary part of the dredge tube and moves correspondingly therewith in vibratory action. The vibratory action of the interior surface is also useful in reducing friction between the upwardly circulated stream or column of earth material in suspension in water with the lining surface of the dredge tube. This frictional drag against the upwardly owing stream of slurry is normally quite material, and is reduced to a relatively negligible factor by the vibratory action produced in the practice of the invention.

The dredging operation has been described in the foregoing primarily in the aspect of breaking up the earthen formation at the bottom, stirring up such material into suspension in the water, and then circulating it up the dredge tube. Also mentioned has been the process of operating with the shoe or bit somewhat off bottom 15, where the effect is primarily to stir loose material already on bottom, bring it into good suspension, and then circ-ulate it up the dredge tube. The process may also be used, as intimated earlier, to cut back the bank 13 by vertical vibration of the laterally projecting ridge formation 45C of the bit when 'these formations are laterally engaged with the bank.

Reference is next directed to FIGS. 4-8, showing an alternative 4embodiment of the invention, which is particularly intended for dredging up ore, such as gold, along river bottoms, though of course it will be understood that the invention is not restricted to that specific application. The apparatus in this case uses a relatively small float 90 in place of the fairly sizable barge of the earlier embodiment, and this oat 90 is shown floating in body of water 91 standing over river bottom 92. The bottom at 92 is to be understood as typically the hard upper surface of bed rock or other strata, which may be covered over to some depth by a more easily penetrable overburden 93 which is at the bottom of the body of water 91. It may be stated that an accomplishment of the invention is to gain access to ore lying on the bottom hard layer 92 through the overburden 93, without the necessity of first removing such overburden.

The dredge tube is designated generally in this instance by the reference num-eral 96, and is positioned on an incline, with its upper end portion over one edge portion of the float, and its lower end provided with a shoe 98 working on or positioned in operative relation to bottom 92. In this embodiment, the shoe 9S is provided with a supporting roller 98a which rolls on bottom 92 and properly positions the shoe relative to the bottom. The dredge tube 96 is provided with a jacket pipe 99 which extends from a point somewhat short of the upper end of the dredge tube to a point along the dredge tube well down into the water, typically as indicated in FIG. 4. Upper and lower spacer rings 100 and 101 connect the upper and lower ends of jacket 99 to the dredge tube 96.

The dredge tube 96, a later described sonic vibration generator mounted thereon, and the jacket 99 are all supported, in the present instance, by means of a U-shaped or horseshoe-shaped vibration isolation spring 104 which is connected to the bottom of spacer ring 100 on one side, and to the underside of a sloping rife board 105 on the other. Riffle board 105, provided with riies 105a of a conventional nature, is in turn supported from the oat by means of bent leaf springs 106 and 107. Isolation spring 104 largely isolates the vibration in dredge tube 96 from the riile board, but does transmit a useful amount of 1ongitudinal vibration to the rife board` for effective separation of the heavier ore from sand and rock. This heavier material is collected in the pockets of the ritile board, as at 1051). The two springs 106 and 107 fairly effectively isolate the vibration in the riffle board from the oat, so that the latter is Inot strongly shaken. The dredge tube jacket is shown to be provided with handles 108.

The vibration generator, designated generally by reference numeral 109, and whose interior details will be described presently, is here shown to embody a generally rectangular housing 110 mounted on a mounting plate 111, which in turn seats on a platform or filler plate 112 located between the underside of plate 111 and the upper side of the upper end portion of dredge tube 96, which ripper end portion will be seen to have a curve therein so as to discharge horizontally onto the upper end of riiiie board 105. Cap screws 113 extend downwardly through mounting plate 111, filler block 112, and into the dredge tube 96 to secure the generator 109 firmly to the upper end portion of the dredge tube.

Generator 109 is an air-driven type, having air intake hose 115 leading from an air compressor 116 driven from lan internal combustion engine 117, the compressor 116 and engine 117 `being mounted on a common platform 118, supported by arches 119 mounted on float 90. Spent air from generator 109 is conducted via discharge pipe 120 to the upper end of the annular jacket space 121 inside jacket 99, flowing downwardly within this space to ports 122 formed in dredge lnube 96 inside the jacket but near the lower end shoe 98. This air mixes with the water inside dredge pipe 96, lightening its density, so that an up- 10 ward circulation of the water and material in suspension therein is established within the dredge tube. It will be clear that with the density of the fluid in the dredge tube reduced by the presence of the air thus circulated therethrough, the hydrostatic pressure on the exterior body of water will force a flow upwardly through the pipe 96.

The vibration generator 109 is shown more particularly in FIGS. 6 and 7. The housing 110 has a cylindrical raceway therein, and within and coaxial with this raceway is a pipe 131, closed at one end, and coupled at the other to air supply pipe 115. Pipe 131 has tangential discharge jets 133 extending from its interior bore to its exterior periphery. Surrounding the pipe 131 is a gyratory ring 134, of a diameter somewhat larger than the outside diameter of the pipe 131 and such that, when in engagement on one side of the pipe 131, it just slightly clears the surface of the bore 130 on the opposite side. Air under pressure entering the bore of pipe 131 is ejected in tangential direction toward the ring 134, and drives the ring s0 as to spin or whirl on the pipe 131, in the direction of the arrow, as indicated in FIG. 6. The spent air, after impinging on the ring 134, escapes from within the ring by way of grooves 136 formed in the side walls of the housing, and then discharges by way of outlet passage 137 leading to the aforementioned hose 120.

The shoe 98 shown for illustrative purposes is of a type which might be compared to a vacuum cleaner nozzle, having an open aperture `98b at the bottom spaced shortly above the supporting rock l'ioor 92 by wheel 98a. In other applications, the shoe can be modified, and can, for example, be given cutter or cutting bit characteristics, and be arranged for engagement with and acoustic coupling to the structure of the floor or bottom 92, or merely, in some cases, to the overburden 93 on floor 92.

It will be noted that this nozzle 98 has a lower edge which will engage with projections of the earthen structure 92, to apply sonic energy thereto and cause sonic cutting in the manner of a sonically activated bit. Various teeth members of the type shown in connection with FIG. 1 may be formed in this lower edge, as shown. Deletion of roller 98a, if desired, will increase this bit cutting action.

The operation of the modified system of FIGS. 4 8 is in general respect similar to that of FIGS. l-3. The vibration generator 109 clamped to the upper end of elastic dredge tube 96 applies to said dredge tube a gyratory force, one component of which is oriented longitudinally of the dredge tube, and the other laterally of the dredge tube. The generator is driven at the frequency for resonant, longitudinal, half-wave standing wave vibration of the dredge tube, producing a half-wavelength standing wave in the dredge tube as diagramrned at W in FIG. 4. The component of the gyratory output force of the vibration generator which is a right angles to the longitudinal axis of the dredge tube creates lateral or transverse vibration in the dredge tube, but since, in general, the resonant standing wave frequencies for longitudinal and lateral vibrations differ considerably from one another, if the generator is driven at the Ifrequency for longitudinal resonant vibration, such frequency will ordinarily be somewhat removed from the resonant frequency for lateral resonant vibration. Accordingly, the dredge tube may Abe vibrated predominantly in the longitudinal standing wave mode, though some lateral vibration will be attained. The longitudinal standing wave, as diagrammed in FIG. 4, is preferred, but useful effects can also be obtained by tuning for a lateral standing wave, which constitutes an alternative practice of the invention.

In FIG. 4, the shoe on the lower end of the dredge tube is not of a cutter type, and is, in fact, supported above rock bottom 92 by roller 98a. Sonic wave radiation takes place from the shoe, which is in acoustic coupling Irelationship to the water, and sound wave action is thus transmitted into the water, producing the stirring and agitating effect described in connection with the earlier embodiment of the invention. The dredge tube is shown, for illustrative purposes, in this case, as reaching down through a layer of loose or soft overburden 93, as earlier described, so as to work on hard bottom 92. The described stirring and agitating action as a result of sound wave radiation from the shoe brings this overburden material, as well as sand and rock on bottom, together with particles of ore resting on bottom, up into suspension in the liquid immediately below or within the shoe. A circulation of liquid is established up the dredge tube by which this suspended material, inclusive of the ore particles raised off bottom, may be lifted up the dredge tube. This may of course be accomplished by use of the system illustrated in FIG. l, namely, by use of a centrifugal pump. The system of FlG. 4, however, shows an alternative arrangement by which the air exhausted from the Vibration generator is used to reduce density and establish this circulation of water and suspended material up the dredge tube, as describe-d in more particular hereinabove. Thus, the suspended material is circulated up the dredge tube, and deposited on the riflie boar-d 195, along which it travels to the discharge end thereof. This ritile board receives a degree of vibration from the standing wave vibration in the dredge tube 99, sufficient to promote dropping of the high-density ore particles into the pockets between the riffies.

yThe over-all action is unique, in that the lower end of the dredge tube is moved along the river bottom through the overburden, parting the latter and working directly on bottom, so as to pick up the valuable ore most likely to be found in that location.

It will of course be understood that various modifications of the shoe 98 may be employed, and the shoe may drag directly on the bottom, may have cutter teeth thereon, or even be pressed against 1bottom or acoustically coupled thereto in any desired manner.

It will be understood that the drawings and descriptions are merely illustrative of the invention in presently conceived |forms, and that various changes in design, structure, and arrangement may be made without departing from the spirit and scope of the broad invention or of the claims appended hereto.

I claim:

1. In a sonic apparatus for dredging earth material from the earthen bottom of a body of water, the combination of:

a dredge tube extending downwardly to a position adjacent to said earthen bottom,

a resonant sonic vibration radiator at the lower end of said dredge tube lfor stirring up earthen material at said bottom and bringing it into suspension in the water so as to form a slurry adjacent said lower end of said dredge tube,

a resonant elastic vibration system vibratorily coupled to said radiator,

sonic generating means for driving said sonic wave radiator, said generating means Ibeing operable at a frequency which will produce Sonic wave vibration, and

means for circulating said slurry up said dredge tube.

2. The apparatus of claim 1, including means causing forcible engagement of said sonic radiator means with said earthen bottom below said body of water.

3. The apparatus of claim 1, including means supporting said sonic radiator means with a gap between said radiator means and the earthen bottom below said body of water.

4. The apparatus of `claim 2, wherein said sonic radiator means comprises a bit.

5. In a sonic apparatus for dredging earth material from the earthen bottom of a body of water, the combination of:

a platform for floating on said body of water,

an elastically vibratory dredge tube extending downwardly from said platform to a position adjacent to said earthen bottom,

a vibratory sonic wave radiator shoe coupled to the lower end of said dredge tube so as to vibrate therewith,

sonic vibration generating means acoustically coupled to the upper end of said dredge tube for setting up sonic resonant standing wave vibration in said dredge tube and thereby vibrating said sonic wave radiator shoe, said generating means being operable at a frequency which will produce sonic wave vibration, and

means for circulating slurry up said dredge tube.

6. The subject matter of claim 5 wherein said vibration generator means is operable at a frequency for a longitudinal mode of standing wave vibration in said dredge tube.

7. The subject matter of claim 5 wherein said vibration generator means is operable at a frequency for a lateral mode of standing wave vibration in said dredge tube.

8. The subject matter of claim 5, including dredge tube support means affording forcible engagement of said sonic radiator shoe with said earthen bottom below said body of water.

9. The subject matter of claim 5, wherein said radiator means comprises a bit.

10. The subject matter of claim 5, including spring means yieldingly vertically supporting said dredge tube from said platform.

11. The subject matter of claim 10, wherein said spring means comprises an air spring.

12. The subject matter of claim 5, wherein said means for circulating slurry up the dredge tube comprises a slurry discharge conduit connected to the upper end portion of said dredge tube and a pump connected into said discharge conduit.

13. The subject matter of claim 5, wherein said means for circulating slurry up the dredge tube comprises a means for introducing a gas into a lower rregion of said dredge tube.

14. The subject matter of claim 5, including also a venturi tube liner in said dredge tube.

15. The subject matter of claim 5, wherein said radiator means comprises a bit rotatably mounted relatively to the lower end of said dredge tube, and including also means for rotating said bit.

16. The subject matter of claim 5, wherein said radiator means comprises a bit rotatably mounted relatively to the lower end of said dredge tube, and including also means for oscillating said bit about the longitudinal axis of said dredge tube.

17. The subject matter of claim 5, including also an elongated jacket rotatably surrounding a substantial length of said dredge tube below said platform, said wave radiation shoe being fixed to said jacket and rotatable therewith relatively to said `dredge tube, and means for preventing relative longitudinal movement of said lower end of said dredge tube and said shoe.

1S. The subject matter of claim 5, including means on said shoe for supporting it on and at a predetermined distance above bottom.

19. The apparatus of claim 1 wherein said generating means is operable at the resonant frequency of said resonant elastic vibration system coupled to said generating means and said radiator.

2d. The process of sonic dredging which includes:

coupling a sonic frequency resonator to a sonic vibration radiator means;

positioning said radiating means adjacent the bottom of a body of water;

operating said resonator at sonic frequency so as to activate said radiator means for sonically stirring up earthen material at said bottom; and

conducting water with said stirred-up earthen material up a dredge ow passage from the region of said stirred-up earthen material.

21. The subject matter of claim 20, including also the step of pressing said radiator means forcibly against said Ibottom.

FOREIGN PATENTS 697,311 11/1964 Canada'. 72,377 11/ 1943 Czechoslovakia. References Cited by the Examiner 1,069,453 2/1954 France.

UNITED STATES PATENTS 5 10/ 1887 Howell 35-58 ABRAHAM G. STONE, Primary Examiner.

4/ 1909 Eiiel et a1. 37-58 12/1936` Ram-my 37 195 X JOE O- BOLT, Exmme 5/1951 Bodine. t E 11/1961 Skakel et al. ,57195 10 J. R. OAKS, Asszs ant xamznef.

Claims

1. IN A SONIC APPARATUS FOR DREDGING EARTH MATERIAL FROM THE EARTHEN BOTTOM OF A BODY OF WATER, THE COMBINATION OF: A DREDGE TUBE EXTENDING DOWNWARDLY TO A POSITION ADJACENT TO SAID EARTHEN BOTTOM, A RESONANT SONIC VIBRATION RADIATOR AT THE LOWER END OF SAID DREDGE TUBE FOR STIRRING UP EARTHEN MATERIAL AT SAID BOTTOM AND BRINGING IT INTO SUSPENSION IN THE WATER SO AS TO FORM A SLURRY ADJACENT SAID LOWER END OF SAID DREDGE TUBE, A RESONANT ELASTIC VIBRATION SYSTEM VIBRATORILY COUPLED TO SAID RADIATOR, SONIC GENERATING MEANS FOR DRIVING SAID SONIC WAVE RADIATOR, SAID GENERATING MEANS BEING OPERABLE AT A FREQUENCY WHICH WILL PRODUCE SONIC WAVE VIBRATION, AND MEANS FOR CIRCULATING SAID SLURRY UP SAID DREDGE TUBE.