US2597036A

US2597036A - Endless digger type mine dredger

Info

Publication number: US2597036A
Application number: US783564A
Authority: US
Inventors: Jonas L Roe
Original assignee: Quandro Mining & Equipment Cor
Current assignee: Quandro Mining & Equipment Cor; Quandro Mining & Equipment Corp
Priority date: 1947-11-01
Filing date: 1947-11-01
Publication date: 1952-05-20
Anticipated expiration: 1969-05-20

Description

J. L. ROE

ENDLESS DIGGER TYPE MINE DREDGER May 20, 1952 1 hm O wm mm wm Nm mm, Q s w wm R.,/ L@ Q H %.Q\ Wmv NA N mmv WQ w QW n N R .R N O m IJ l A Filed Nov. 1. 194'? Filed Nov. l. 1947 May 20, y .J'L' ROE ENDLESS DIGGER TYPE MINE DREDCER' 3 Sheets-Sheet 2 v vE/vroR, JONAS L. Q05,-

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May 20, 1952 J, ROE

ENDLESSYDIGGER TYPE MINE DREDGER 3 Sheets-Sheet 5 Filed Nov. l. 194'? Z'A/ VE/ ro R, JONAS L. Q0

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Patented May 20, 1952 STATES. P

TENT Quandro Mining & EquipmentCorp., a corporationof California Application November 1, 1947,l Serial No. '783;564

pClaims.. 11v

The presentl invention relates to dredgers. Particularly the invention has for an object the provision of" a dredgeradapted for tunneling, breasting and general excavation in drift-channel types of'v mines. The invention eliminates the use of drilling, blasting and manualhandling of materialgunder ground:

The invention has for an object Ythe provision of a dredger which is particularly adapted for themining ofrninerals. The device functions to remove the ground' andto separate thenes or shipping ore from the waste or tailings.

As an, example of how a device incorporating the invention may be used, it; is customary to irstl cutpinto the hillside and formfa main tunnel which may have aslight slope. Thereafter cross cuts1 are made whichinterconnect theA main tunnel, The present invention s-tarts with the end ofi av cross lc ut at what isV termed the breast. As the-dredger operates, ore which is beingY removed is. sorted by the device of' the invention, the fines being directed' rearwardly of` the device for-.movement outwardlyv of; the mainl tunnel while the tailings are built up adjacent. the breast. In this manner a tunnel4 is formed-andbuilt against the hreastatsnbstantially the same time so that the removedl cut is relled; This is known as the retreating methodK of tunnelling or dredging, I t 0f. QQurse, understood that the earth. prior to tunnelling has beenoompacted' by nature. The tunnelling operation breaks upthe earth. However, the refilling is such as to restore the earth substantially to, its original condition prior to c ompacting, In the typerof operation performed the. device operates upon minerals which are to be. mined andl a` method is followed wherein the gravelj ismixedwithweter as is likewise the tailings.. As.. rule. experience. has shown that e13- proximately 3,51% of thegravel' is removed to the surface for processing.

An objectof theinvention is the provision ofa dredger whichprogressively tunnelsthe earth formation in a simple and. expeditious manner- Afurther Objectis the provision efe. dredging machine incorporating a novel. ferm 0.1V boem which is ener ted a positive. manner and Whereby. tlfiebooml may b e raised; loweredV or turned to the right or ljet without they use of cables, jib arms, the. like.

A further object is the provision of a dredging machine incorporating ahydraulic means which is positivein its operation and adapted to control operation of a boom.

A further object, is the provision ina dredging machine of means which classifies on the job the oredredged,3

A further object is the provisioningJ dredger of aboom having. a bucket: line adapted to be drivenin a positive manner.

Another object is the provision` in. a. dredger o f an eicient type of mounting for aY boomA and whichpermits the boomfto be easilymoved;

A further object is the provision of a dredger construction which permits easy assemblage, of the various parts, which is, eilicientin opera-tion and. generally. superior to dredgersnow known to the inventor.

With the above mentioned and` other. objects in View, the invention consists. in thenovel` and useful provision, formation, construction, association and relative arrangement offparts, members and features, all as shownin one embodiment of the invention in theaccompanying drawings, described generally and more particularly. pointed out in the claims.

In the drawing-s:

Fig. 1 is a fragmentary side elevation. of.L the dredger` ofthe invention shown in the act. of excavating earth;

Fig. 2- is a transversesectional view on theline 2-.2 of Fig. 1, showingl the. portions of.V the boom and its operating mechanism;

Fig.A 3 is a fragmentary4 plan. view partially. in section, schematically showing the hydraulic system for operatin'gthe boom, together with an electrical circuit for motors associatedy With thehydraulic system, the saidviewbeing taken substantially on the line 3--3` of Fig. 1

Fig. 4 is a fragmentary elevation looking substantially in the direction of the arrows on line -l of Fig. 1;

Fig. 5 is a fragmentary sectional view on the line 5 5 of Fig. '7;

' Fig. 6y is a fragmentary sectional View on the line 6 6 of- 5; Fig. '7 is a sectional view on the line 1.-] of Fig. 5; l

Fig. 8 is 'an end elevation of the/invention looking toward theboomofFig. l;

Fig. 9 is a fragmentary View of ther dredger in the act of` tunneling, and showing movement of certain members thereof in one plane;l and,

Fig. 10-is a plan View of the showingin Fig. 9, and illustrating the sweep of an element ofthe dredger in a transverse direction.

Referring` now withv particularity to thedrawings, the dredger l includes a tractor 2A mounted on a pair of endless chains' 3 and` 4, which are ordinarily called Gaterpillars the chains being driven in any suitable manner for the purpose of propelling the vehicle4 forwardlyA or` backwardly, together. with a boom 5 atoneend of the tractor,

which boom includes a bucket line designated generally as 6, the buckets being of the excavating type and which boom, through mechanism designated generally as 1, is capable of being raised or lowered and swung on an arc, together with means 8 adapted to classify or separate certain sized ore from tailings or waste material, all of which means cooperate in the performance of a dredging operation.

While the dredger as an entirety has the appearance shown in Figure l, still no particular type of tractor or framing is contemplated. It is expected that a framing in a device of the character of this invention should be rigid in structure and adapted to resist stresses of large magnitude. As shown in Figures 5 and '7, the tractor, as to its framing, includes -a pair of spaced-apart side Walls 9 and I0, a bottom or base wall I I, and a top wall I2,both of which interconnect the side walls. These walls are brazed, welded, or otherwise secured in cooperative relationship.

The framing also includes end walls I3 and I4. the end walls are rigidly secured to top wall I2 in any approved manner, such as by welding. The end walls and side walls 9 and I0 extend above the top wall I2. This provides a space to confine other mechanism utilized in the practice of the invention, as hereinafter detailed.

The means 8, utilized for the purpose of classifying the ore, constitutes a trommel in theV form of a perforated drum I5. This drum has annular end members of reduced diameter shown at I6 and I1 which are secured to the main drum structure by annular flanges.l The end I6 is passed through an enlarged opening in the end I3 of the framing while end I1 thereof is passed through openings in a pair of members I8 and I9. The arrangement is such that the trommel is supported on rollers at both ends. For instance in Figure 6, a pair of rollers and 2| have trunnions passed between end wall I3 and a wall 22, the rollers being in engagement with the periphery of the reduced diameter member I6 of the trommel. The opposite supporting means for the trommel follows the same practice in that the rollers shown engage the periphery of the reduced end I1 of the trommel. These rollers are interposed between members I8 and I9 and held therebetween by means of trunnions.

whereas members I8 and I9 are removable from said frame so as to permit the trommel to be inserted within the frame and rotatably held therein.

The members I8 and I9 are held separated by an annular spacer piece 23, which spacer piece is provided with a flange 24. The end wall I4v has an enlarged opening and the flange 24 is adapted to be secured by bolts 26 to said end wall. The construction is such that end Wall I9 ts within the enlarged opening 25. Thus the walls I8 and I9 are removable as a unit With the opening 25 of such size as to permit ready passage of the trommel therethrough. The trommel is surrounded by a trommel casing 21 of circular form, said casing is welded or otherwise secured to end Walls I3 and 22. The opposite end of said trommel casing is xedly secured to the end Wall I4. Thus by providing framing top, bottom and side walls, together with the trommel casing, all secured together in stress-resisting relationship, a rigid frame structure results.

The perforated drum I5 of the trommel externally carries helical blades, blades 28 being It is to be v observed that end wall I3 is fixed to the frame,

pitched opposite to blades 29 for a purpose hereinafter set forth. The trommel drum is internally provided with a helical blade 30 which is pitched in one direction and extends between the ends thereof. It may be stated that the reduced diameter portion I6 is the inlet end for the trommel and reduced diameter portion I1 is the outlet. The external blades on the trommel are adapted to direct fines to a given location in the trommel casing 21. A motor 3|, is positioned on the top wall I2 adjacent the end Wall I4. The motor s'haft'32` carries a sprocket, not shown. The'reduced diameter portion I1 of the trommel drum is provided with a sprocket, not shown, and a continuous chain 33 is passed around the sprockets aforesaid for the purpose of rotating the trommel.

A trough 34 is inclined downwardly Within the reduced end I6. This trough is used for feeding ore within the trommel and to assist in said feeding the trough is formed to carry a valved pipe 35 through which Water, under high pressure, is directed against any ore received on the trough for reception within the trommel.

Positioned beneath and depending from the base member II is a casing 35. This casing is in direct communication with the interior of the trommel casing. The bottom wall II and trommel casing 21 have axially aligned openings at 31 and 38 with a wall extending between said members and surrounding the openings. The casing 36 is adapted to house a pair of intermeshing bevel gears 39 and 40, bevel gear 39 being mounted on a shaft 4I suitably journalled in the casing with one end of said shaft carrying an mpeller blade 42. Gear 440 is passed through the side wall of the casing and is mounted upon shaft 43 of a motor 44, the motor being external of the casing and secured to the bottom Wall II. The casing 36 is involute in form and has its outlet at 45 (see Figure l). The outlet is in communication with a flexible hose 46. By way of example, when ore is fed into a rotating trommel, the nes of a given size will pass through the perforations in the trommel and be received upon the inner Wall surface of the trommel casing. The helical external blades 28 and 29 will move this material toward the opening which communicates with the casing 36 and the impeller blade Will then direct the material so received therein to the outlet of said casing and into the flexible hose. It is obvious that the casing 38 together with the impeller therein and the means for rotating the impeller constitutes one form of sand pump. That material which is received within the trommel and does not pass through the perforations thereof is directed outwardly of the trommel through end I 1, being fed by the helical blades 30.

In the practice of the invention, water is used and I provide a pipe 41 which is axially passed through the reduced end portion I1 and into the trommel. The pipe is provided with a series of perforations 48 whereby Water may be sprayed on the ore received within the trommel.

The boom 5, with its associated bucket line, is adapted to be moved in various directions so as to perform, in an eiiicient manner, an earth digging or tunnelling operation. This boom is mounted in a gimbal 49, the gimbal being substantially rectangular in form (see Figure 4), the gimbal having side members 5U and 5I interconnected by top and bottom transverse pieces 52 and 53. The top and bottom transverse pieces are centrally provided with studs 54 and 55 which are receivedinf bearings carried by top and bottom gimbal supports 56 and 51. The bottom support 51 is secured toithe bottom wall I I, while the topsupport '6 is secured between the end wall I3 and the side walls-9 and I0. As shown inv Figure 1, the-supporte may have offset portions so as to permit the gimbal to readily rotate between said supports.

TheY boom 5 is mounted in the gimbal 89 at one end thereof; The boom 5 includes a pair of spaced-apart elongated side plates 58 and 259 braced by a longitudinally extending, centrally positionedk rib 6I), the said rib provided with transverse end pieces lil and 52, which extend between the side plates. The rib, the transverse pieces, and the side plates are all rigidly secured together. Adjacentv the outermost end of the boom, and provided in` each side plate, are bearings 63 and 84 adapted to rotatably support therebetween a shaft'65. Positioned between the

side plates

58 and 59 and carried by the shaft 65 are. sprockets 66 and 61. The opposite end of' the boom has the side plates 58 and 59r thereof provided with

bearings

68 and 69, carrying a shaft 18'. Mountedv externally of the

side plates

58 and 59 are gears 1I' and 12. The sides 58 and 5I of; the gimbal are positioned between the side plates ofthe boom and a gear, as best shown in Figure 4, the gimbal being provided with bearing portions through which the shaft 1i) is passed. Sprockets 13' and 14 are mounted on shaft 18, which sprockets are in substantial parallelism with. sprockets 68 and 61. Forward of the transverse piece 62T are a pair of axially aligned shafts 15' andY 15'. These shafts are carried in suitable bearings provided in the side plates '58 and 59;. and. gears 11 and 18 are carried on ends of said respective shafts, the gear 11 being in mesh with gear ISI while gear 18 is in mesh with gear 12. Carried on the shafts 15` and 16 and within the confines of the

side plates

58 and 59 are bevel gears. 19 and 88, these bevel gears being in meshv with further independent bevel gears 8I- and 82. Bevel gears 8| and 82 are carried on shafts of motors 83 and 84. These motors aremounted in any convenient manner between the rib 68- and the side plates. It will be observedthat each motor, when in operation, drives a shaft, whichY independentA shafts 15 and 16 in turn cooperateto drive the single shaft 18. The advantages of this construction will be detailed in the statementv of the operation.

Extending between both ends of the boom and over the

sprockets

66, 61 and 13, 14 is the bucket line 6. The bucket line includes buckets 85 which are spacedly secured by solid links 86. IThis bucket line is conventional, and the said links thereof' are joined together in the usual manner, such as best,` illustrated in Figure 2, that is to say,` by means of pins passed through knuckles in both the links and the buckets.

The buckets are of the excavating type,l which is to say that a sharp tooth or teeth portions 81 are provided. for each bucket, which teeth cut thev earth formation and deposit the same in the scoop portion of the bucket and hold it therein during travel of, the bucket to, in turn, deposit such formation onto the trough 34. No particular form of the. bucket is contemplated, as buckets. arel common in the art.

The mechanism 1 for; controlling movement of the boom is` detailed in Figure 3. Positionedbetween the.v trommel casing 21Y and the bottom. and side wallsr of the tractor are elongatedl cylinders 6. 885 and 89. wall Ii3.

Each cylinder has an intermediate division wall. 98'. and 9i'. Each cylinder' forward of its division wall", toward the end wall I3, is openended' while a` second portion of. the cylinder is closed or provided with a head at 92 and 953. For convenience of' description, the open-end portions as applied to each cylinder are designated as Qliand and the closed portions as. 96 and 91. Within the, closed portions of the cylinders are pistons 9i; and' 99 and within the open-ended portionsof each cylinder are cross-heads l 88 and Ii". Piston rods designated generally as m2 interconnect the respective cross-heads with a piston= and said rods are passed through the division walls 88 and SBI- as shown in the figure. Each cross-head has` a socket portion EMS. Arms Iii and F85 are secured to

side plates

58 and 59, each arm at one end carrying a socket ISE, 81. Links Hi8 and its are provided with ball ends, as for instancel illustrated at Il, which ball ends are positioned between the sockets of the cross-heads and the arms. It is evident that movement of the links will swing thev arms IM and IE5 to in turn cause movement of the boom, as hereinafter set forth in the statement of operation.

A hydraulic system is utilized for actuating the pistons in the cylinders, which system is shown diagrammatically in Figure 3. I prefer to use a closed system and accordingly, I provide independent pumps of any type. In the drawing two gear pumps HI and HZ. are provided. A pipe iii-3 communicates with one end of cylinder portion 8S, the opposite end thereof being in cornmunication with pipe II leading to either the intake or outlet opening of the gear pump. Pipe II. connects with a check valve I i5, which check valve in turn communicates through pipe IIS with a tank ill and likewise with a check valve H8. Check valve IIS through the medium of pipe I I9 connects with the pump at the opposite port thereof, which may be either intake or outlet, and with the opposite end of the cylinder portion e5; Without detailing further, it may be said that the same procedure is followed for the opposite cylinder portion, it being noted that the pump H2 has check valves on opposite sides thereof and that the line H55 communicates with the said check valves. Electric motors It@ and I2-I- may drive their respective pumps by any suitablemeans. Each electric motor is in circuit with a reversing switch |22 and |23, the reversing switches leading tol overload circuit breakers igt and' H25, the said switches and the said circuit breakers in turn being connected with a source of power supply.

The operation., uses and advantages of the invention are as follows:

It is intended primarily that the Caterpillar cr tread portions 3 and should be positioned beneath the tractor frame rather than in the position shown in Figure 3. This will permit a greater swinging of the boom. To operate the boom in the manner depicted in Figures l0 and ll, the motors I2@ and I2! are energized upon the throwingk of the reversing switches in one or the other direction, it being intended in the present system that the pumps III and II2 should be reversed as to operation and as to the direction in which fluid is passed through the respective pipes. rlhe tank I i1 is filled with hydraulic fluid andv initially the closedv portions S5 and 91 ofv the cylinders arelled with fluidY on both sides of. the pistons se and 89. To prevent leak, pack- Each cylinder terminates in end ing is provided in the division walls 90 and `9| at the zone of passage therethrough of the piston rods. The cross-heads in the open-ended

cylinder portions

94 and 95 stabilize the thrust on the links |08 and |09 and likewise that on the piston rods |02. If the boom is positioned centrally of the tractor frame, and it is desired to raise the boom from its lowered position of Figure 10 to its upper position as indicated by the dotted line position thereof, hydraulic fluid is pumped behind each piston, that is to say, into the space included between the respective pistons 99 and 99, and the end walls or heads 92 and 93. As fluid lls the space between the pistons and the division walls 90 and 9|, it is necessary to bleed this fluid. Hence, assuming proper rotation of each hydraulic pump, the fluid is removed from one side of each piston and directed through the pipes, assu-ming one side explanation, into pipe |20 through the pump into pipes ||4 and ||3 rearward of the piston. The other side is operating the same way, with the result that there is a direct thrust upon the piston rods and the associated links which interconnect the arms |04 and and the boom will be moved upwardly, the boom revolving on the shaft 10. To swing the boom transversely or on an arc, as illustrated in Figure l0, one of the reversing switches is thrown, say the switch at |23, whereupon fluid included between the piston 99 and the head 93 is removed or bled and passed to the other side of said piston or between the piston 99 and the wall 9 l. This is accomplished by reversing the direction of movement of the motor, which reverses the movement of gear pump ||2. The operator need not watch the boom movement, as when the boom has swung its full arc, the overload circuit breakers |24 and |25 will operate and brea-k the circuit. In the event that the piston in one or the other of the cylinders does not complete its stroke, one or the other of the one way check valves in the pipes ||4 and ||9 will open and direct fluid into the line from the tank 1. After suicient iiuid has been obtained the check valves will close. is being removed from one end of the cylinder and directed to the opposite end, that there is a negative pressure on one side of the line and a positive pressure on the other. If this negative pressure is less than atmospheric, a check valve will open and admit liquid from the supply tank. If we assume that the sweep of movementy for the boom is at a lower level or in the plane of the solid lines for the said boom, shown in Figure 10, the boom may be held in this position during a sweep by reversing the turning direction of both motors |26 and |21 upon operation of the switches |22 and |23. Liquid is directed behind one of the pistons under pressure, whereas the opposite cylinder removes fluid from behind a piston and directs the uid under pressure forwardly thereof. This swings the boom. If it is also desired to raise the boom, one or both pistons are moved forwardly to a given position. If a single piston is moved forwardly to a given position, and the other piston retracted, the boom will be brought to a given level and turned, depending upon which piston is actuated. I, therefore, have complete control of boom movement with a device that does not incorporate cables, jibs, or other projecting members, and one ythat is simpler to operate and more positive in its action.

As illustrated in both Figures 1 and 8, the arms |94 and |85 are curved in part and secured to the side plates of the boom adjacent the low- It is evident that when liquid j 8i ermost edges thereof. This construction affords for leverage so that the device will readily lift the boom as well as swing the same. Y Y

The motors 83 and 84 may be of small size and positioned between the rib 6i) and a side plate. Thus, the boom is stabilized by this construction and a large single motor is unnecessary. Movement of shaft 19 is controlled by the independent motors which revolve the independent shafts 15 and 16. This construction, in actual practice, gives iiexibility to the structure and permits proper movement of the bucket line, particularly when the bucket line is engaging formation which is diicult to cut. The buckets excavate the formation, as 'shown in Figure 1, and carry the formation along the upper course of the continuous bucket line, the buckets finally depositing the ore onto the trough 34 for reception within the trommel. During movement of the bucket line, the trommel is being rotated by motor 3|, motor 44 is energized to revolve the impeller 42, and Water is being forced under pressure through line 35 over the trough, while at the same time, water is being passed through pipe 41, through openings 4.8, and into the trommel. Pipe 41 is eccentric to the axis of the trommel so as not to interfere with ore received therein. I provide a pair of pipes at |26 and |21 which are secured to the trommel casing, as shown inrFigure 7, and which pipes have openings communicating with openings in the trommel casing throughout its length. Pipes |26 and |21 communicate with a source of water supply. Thus', as the ore is removed and carried by the bucket line, and dumped onto the trough, water under pressure through line 35 aids in directing such ore within the trommel. The trommel, as it rotates, will feed the ore therein from one endthereof to the other, through the medium of the blades 30, and the nes of a certain size will pass through the perforations of the trommel and be received in the space included between the periphery of the trommel and the inner surface of the trommel casing. The oppositely pitched blades 23 and 29 will feed the material in this spaceV toward the opening which communicates with theA casing 36, to be acted on by the impeller 42, 'and thence directed from said casing 36 rearwardly of the dredger through the flexible hose 46. The tailings of a size not sufficient to allow passage through the perforations are fed outwardly of the trommel through the reduced diameterportion i1, and the flared outlet mouth member |28. Finally, I may protect motor 3| by providing a cover |29, carried by the framing.

I have heretofore detailed in the preamble, a method of removing ore by forming a rst out or main tunnel in the side of a hill, followed by making cross cuts, and then cutting the formation adjacent the breast and by a retreating method, removing the fines and building up the tailings against the breast. The tailings are directed so as to buildup against the breast in each case, whereas the fines are directed through the exible hose 45 for disposition outside the tunnel, the said hose being laid adjacent the main tunnel so that the flow will be outwardly of the hill. In mining operations of the character contemplated for this invention, substantially 35% of the gravel which contains the nes is removed, the remaining percentage largely being tailings or rejects. It is the gravel that is desired as it contains the minerals. For this reason, a suicient quantity of water is used for mixing with the tailings and the gravel.

The Caterpillar or tread portions are operated in the usual manner so that the tractor is at all times moved in accordance with the desires of the operator. The device functions rapidly to cut the formation, to separate the gravel from the tailings or rejects, is of easy operation, and not particularly tiresome to an operator. The operator simply moves switches in one or the other direction to actuate the motors driving the pumps, while other switches control the operation of the bucket line. No particular skill is required, and the operator may stand at one side of the tractor and watch operation while tunneling proceeds.

I claim:

1. A dredger including a tractor frame; a gimbal at one end of said frame; upper and lower gimbal supports secured to the frame whereby the gimbal may rotate on a vertical axis; a shaft mounted on said gimbal transverse to the mounting axis thereof; a boom mounted at one end on said shaft; hydraulic means for swinging the boom vertically on said shaft and transversely upon rotation of the gimbal; said hydraulic means comprising a pair of cylinders, a piston for each cylinder, separate hydraulic pumps, and flow lines leading from said pumps through both ends of the cylinders, the said pistons being connected to the boom.

2. A dredger, including a framing; a gimbal mounted for movement in said framing; a boom mounted for vertical swinging movement in said gimbal, said boom provided with a continuous excavating bucket line; a pair of spaced-apart hydraulic cylinders mounted in said framing, a piston with its arm for each cylinder, links swivelly connected at one end to each piston arm, and at the opposite end swivelly connected to the boom, and means for hydraulically controlling movement of the pistons within said cylinders whereby simultaneous like movement of both pistons in one of two directions vertically swings the boom, and movement of one piston swings the boom transversely.

3. A dredger, including a framing; a gimbal mounted for movement in said framing; a boom having side plates mounted for vertical swinging movement in said gimbal, said boom provided with a continuous excavating bucket line; and hydraulic means for swinging the boom vertically and transversely comprising a pair of cylinders, each cylinder having: a 4closed end and an intermediate wall forming a cylinder head .between which wall and the closed end is positioned a piston, that portion of the cylinder out-- ward from the intermediate wall being open ended, a piston arm extending through the intermediate wall, a cross head in the open end of the cylinder, secured to said piston arm; an arm for each side plate of the boom, and separate links swivelly connected at each end between an arm and a cross head, simultaneous movement of the pistons within the cylinder in one of two directions swinging the boom vertically upon the shaft, and movement of one of said pistons in one of two directions turning the gimbal to move the boom transversely.

4. A dredger, including a tractor framing, a gimbal and gimbal supporting means secured to said framing, a yboom provided with side plates, a shaft transversely carried by said gimbal and securing one end of said boom, and a pair of motors carried between the side plates of the boom for independently and simultaneously rotating the said shaft.

5. A dredger, including a tractor framing, a gimbal and gimbal supporting means secured to said framing, a boom provided with side plates,

a bucket line positioned between the side plates, a V

shaft carried by said gimbal and securing one end of said boom, a pair of axially aligned shafts carried between the side plates, separate motors for driving each shaft and gearing between each axially aligned shaft and an end of the firstnamed shaft, and means on said first-named shaft for producing movement of the bucket line when both motors are energized.

JONAS L. ROE.

REFERENCES CITED The following references are of record in the lze of this Ipatent:

UNITED STATES PATENTS Number Name Date 750,005 Quertier Jan. 19, 1904 884,960 Suiter Apr.114, 1908 1,859,659 Elliott May 24, 1932 1,948,606 Weining Feb. 24, 1934 2,131,189 Osgood Sept. 27, 1938 2,320,196 Roe May 25, 1943 2,323,493 Sloane July 6, 1943 2,489,635 Gruber Nov. 29, 1949