US2832485A - Power shovel - Google Patents

Description

K. SCHNEKDER POWER- SHOVEL Apr-H 29, 3958 I 4 Sheets-Sheet 1 Filed May 12, 1954 INVENTOR ATTORNEY Aprifi 9, 195% IN. SCHNEIDER POWER SHOVEL 4 Sheets-Sheet 2 Filed May 12, 1954 I INVENTOR MM ATTORNEY 1958 1K. SCHNEIDER 2,832,485

POWER SHOVEL Filed May 12, 1954 4 Sheets-Sheet 3 INVENTOR mam Qm//M AT TOR NEY K. SCHNEIDER POWER SHOVEL vApril 29, 1958 4 Sheets-Sheet 4 Filed May 12, 1954.

INVENTOR ATTORNEY Unite States Patent POWER SHOVEL Karl Schneider, Greenfield, Wis., assignor to Harnischfeger Corporation, Milwaukee, Wis., a corporation of Wisconsin Application May 12, 1954, Serial No. 429,235

8 Claims. (Cl. 214-136) This invention relates to excavating machinery and it more specifically resides in a power shovel having a forwardly inclined boom and a tiltable elongate mast rising above the boom that pivotally connects at the upper end with a forwardly extending dipper stick that has crowding and retracting motions imparted thereto by altering the degree of tilt of the mast, the mast being controlled by a crowd line extending forwardly from the mast to the boom and a retract line extending rearwardly from the mast, and the shovel further including hoist means for a dipper carried by the dipper stick that includes a line attached to the dipper that may be drawn upwardly to impart a digging motion to the dipper.

In a conventional power shovel the dipper stick is mounted directly upon the boom in a position substantially medial of the boom ends. In this position the dipper stick is pivoted about its mounting in response to movements of the hoist cable, and it is attached in a manner to permit longitudinal movement transversely of the boom to effectuate the crowd and retract motions. With the dipper lowered and moved rearwardly to commence a digging motion at the immediate front of the shovel the hoist line will run downwardly along and in close proximity to the underside of the boom. The line thus passes within a small distance of the dipper stick pivot and the moment arm is small. Upon drawing in the hoist line the digging capacity for this dipper position will accordingly be greatly diminished from that otherwise obtainable when the dipper is in a relatively forward position and the hoist line is at a substantial distance to the front of the dipper stick pivot.

. In the present invention the dipper stick is free of the boom and is, instead, attached at its rearward end to a tiltable mast. This mast is elevated toward the vertical when it is desired to lower dipper and shift it rearwardly to commence a digging stroke. With the mast elevated the pivot of the dipper stick is well to the rear .of the boom and the angular incidence of the hoist cable to the dipper stick is greater than for the conventional shovel. The effective digging capacity is thus enhanced for a dipper position to the immediate fore of the shovel cab. This form of apparatus is of particular advantage Patented Apr. 29, 1958 angle to both the dipper stick and the mast. As this crowd line is drawn in the pivoted connection of the mast and dipper stick is drawn forwardly, and with a lifting force being applied through the hoist cable to retain the dipper in raised position the crowd line urges the mast and dipper stick toward a longitudinal alignment. With suificient angular displacement between the crowd line and the mast and 'dipper stick being provided in the geometry of the structure the applied crowding force along the dipper stick will become materially greater than that applied through the crowd line. There is thus achieved the desired crowding force without need of employing undesirably large and bulky control apparatus in the cab of the shovel.

it is an object of this invention to provide a power shovel with improved digging characteristics wherein the dipper may be lowered to the immediate front of the cab and a digging force exerted through the hoist cable that provides enhanced digging capacity at this position.

it is another object of this invention to provide a power shovel wherein the crowding action is enhanced upon thrusting the dipper into a forwardly extended position.

It is another object of this invention to provide a power shovel having the dipper stick and dipper mounted on a mast independent of the boom, whereby a boom of lighter construction may be employed.

It is another object of this invention to provide a power shovel wherein the load of the dipper stick and dip-per is partially sustained by a supplementary mast to reduce the strain otherwise imposed upon the boom by the digging and swinging movements of the dipper.

It is another object of this invention to control the motion of a dipper stick through a pair of crowd and retract lines wound upon simultaneously driven drums that retain the lines taut at all times for immediate re sponse to either a crowd or retract action of the control cables.

These and other objects and advantages of this invention will appear in the description to follow. In the description reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration and not of limitation a specific form in which this invention may be embodied.

In the drawings:

Fig. 1 is a side view in elevation of a power shovel in i which this invention is embodied,

for stripper shovels, wherein extended digging motions are made along a horizontal terrain to shovel.

The invention also presents an apparatus that provides crowding forces at the dipper of large magnitude, that may exceed the operating forces applied to the dipper stick, upon moving the dipper into a position requiring the application of the larger magnitudes of crowding force. As a dipper is moved through its digging stroke and is thrust b'oth outwardly and upwardly into an ex-. tended raised position, *beyond the end of the boom, the required crowding force reaches maximum values. To

the front of the apply an ample crowding force to a dipperin an extended raised position there is employed a crowding line running from the mast to the boom at a substantial Fig. 2 is a fragmentary top plan view of the power shovel showing the boom, mast and portions of the dipper stick, with the mast and dipper stick extended longitudinally along the boom,

Fig. 3 is a fragmentary side view in elevation of the lower ends of the boomand mast showing the pivotal connection therebetween,

Fig. 4 is a clear view in elevation and partly in section of cable drums for the control of crowd and retract cables that are joined to the mast, viewed through the plane 4-4, and

Fig. 5 isa side view in elevation and in section of the cable drums for the crowd and retract cables viewed through the plane 5-5 shown in Fig. 4.

Referring now to the drawings,- for the purpose of describing a specific embodiment of the present invention. there is shown in Fig. 1 a stripper shovel 1 having a cab 2 mounted upon a crawler frame 3. A gantry 4 is provided for the shovel 1 that comprises a pair of vertical tension members 5, one of which is seen in the side view of Fig. 1, that are secured at the lower ends to the cab' platform within the interior of the cab .2, and which extend upwardly above the roof of the cab 2 to connections with plates 6. A pair of compression 6 and extend forwardly u and downwardly to connections with the platform of the cab 2, which connections are not shown. An operators station 8 is provided at the right forefront of the cab 2, and mounted at the forward end of the cab 2 is an upwardly extending tilted boom 9. A set of staylines extend between the upper end of the boom 9 and the gantry 4 to retain the boom 9 in a fixed position. Also carried by the cab 2 is a hoist cable drum 11 and a crowd and retract cable drum assembly 12, which will be hereinafter more fully described when reference is made to Figs. 4 and 5. The drum 11 and drum assembly 12 are driven and controlled by machinery not shown.

As is clearly shown in Figs. 2 and 3, there is pivotally mounted to the upper side of the base of the boom 9 a tiltable mast 13. The mast 13 includes a pair of parallel legs 14 spaced from one another at a distance slightly greater than the breadth of the main run of the boom 9. The lower end of each mast leg 14 is hinged to a set of plates '15 attached to the top side of the boom 9, and a reinforcing member 16 is extended between the lower ends of the mast legs 14. A bracket 17 is attached to the upper side of the reinforcing member 16 and supports a rotatable cable sheave 13, the pivot of which is displaced as the mast 13 is tilted with respect to the boom 9, as is shown in Figs. 1 and 3.

A fabricated reinforcing 19 extends between and spaces the upper ends of the mast legs 14. The reinforcing 19 presents a pair of brackets 29 on the topside of the mast 13 for connection to a pair of retract lines 21 and a pair of brackets 22 on the underside of the mast 13 for connection to a pair of crowd lines 23. The underside of the reinforcing 19 presents an abutment 24 to a set of shock absorbers 25 mounted upon several bracket plates 26 on the topside of the boom 9 in a position to limit the forward tilt of the mast 13. Also mounted by the bracket plates 26 are a pair of rotatable sheaves 27 about which are passed thecrowd lines 23.

After passing about the sheaves 27 the crowd lines 23 pass downwardly along the upper side of the boom 9 toward the cab 2. The lines 23 terminate in connections with a cross tie 28 that is in turn joined to a single crowd cable 29 that passes beneath the cable sheave 18 and hence to the drum assembly 12. The pair of retract lines 21 extend rearwardly from the upper end of the mast 13 and pass about two of a set of sheaves 30 mounted upon the gantry 4. The lines 21 are then connected through a cross tie 31 to a single retract cable 32 which leads downwardly to the drum assembly 12. Upon operation of the drum assembly 12 the crowd cable 29 and retract cable 32 will be simultaneously operated, whereby one will be drawn in while the other paid out so as to shift the mast 13 from one position of tilt to another.

Pivotally joined to the upper end of the mast 13 is a 7 two armed dipper stick 33 that extends forwardly and passes to the front of the boom 9. Each arm of the dipper stick 33 is closely spaced to one of a pair of bearing bars 86 on the sides of the boom 9, against which the stick 33 may bear either during a digging operation or a swinging of the cab 2. A dipper 34 is mounted on the forward end of the dipper stick 33, and a dipper sheave 35 is pivotally mounted through a bail 36 to the top of the dipper 34. To control raising and lowering of the dipper 34 a hoist cable 37 is led upwardly from the hoist drum 11 around one of the set of sheaves 30 on the gantry 4 and hence forwardly to the top of the boom 9, where it passes about one of a pair of boom sheaves 38 and then runs to the dipper sheave 35. The hoist line 37 passes about the dipper sheave 35 and returns to the boom sheaves 38 and then extends rearwardly to a dead end connection with the gantry 4.

Referring now specifically to Figs. 4 and 5, there is shown the retract and crowd cable drum assembly 12. A drive shaft 39 is-borne'at its ends by bearings 40 mounted within support housings 41. Keyed to the right hand end of the shaft 39 is a gear wheel 42 of large diameter that is in mesh with a driving gear, not shown. Rotation of the gear wheel 42 will cause similar rotation of the drive shaft 39, and keyed to the shaft 39 at the side of the gear wheel 42 to rotate therewith is a sun gear 43 forming apart of a planetary system to be described. The planetary system includes a support 44 for a set of planet gears 45 that is rotatably mounted by a bearing 46 seated upon the hub of the gear wheel 42 and a bearing 47 seated upon the sun gear 43. The planet gears 45 are in mesh with an internal orbit gear 48 that is bolted to a crowd cable drum 49.

A plurality of spokes 59, each braced by a web 51, extend radially outwardly from the planet gear support 44 to support a brake drum 52 that is encircled by a brake lining 53. Disposed in facing relation to the lining 53 is a brake band 54 that is shown in brake released position, and which may be brought into braking engagement with the lining 53 by operation of means not shown. Upon engaging the brake members 53, 54 the planet gear support 44 is held in stationary position, and each planet 45 will be rotated by the sun gear 43 to drive theorbit gear 48 in a direction of rotation opposite that of the drive'shaft 39. The crowd cable drum 49 is moved in a likedirection. The drum a9 is rotatably supported at one end upon the drive shaft 39 by a bearing set 55, and extends axially to the left, as viewed in Fig. 4, to terminate in a hub 56 that encircles and is borne by a hub 57 of a retract cable drum 58. A sleeve bearing 59 separates the hubs 56 and 57 to permit a limited angular displace ment to occur between the drums 49 and 58. To rotatably mount the retract cable drum 58 a roller bearing set 69 supports the hub 57 upon the drive shaft 39, and a set of tapered bearings 61 are interposed between the shaft 39 and the left side of the drum 58.

Bolted to the left side of the retract cable drum 58 is a double brake and clutch rim 62 that presents an outer brake member 63 with a brake lining 64 and an inner clutch member 65. A brake band 66 surrounds andis in facing relation to the brake lining 64 for a braking engagement therewith. It is the purpose of the brake members 64, 66 to restrain rotation of the cable drums 49, 58, upon setting the band 66 in engagement with the liningfid, to hold the mast 13 in desired position. Within the clutch member 65 is an outwardly movable clutch band 67 carried by a clutch member 63 that is keyed to the drive shaft 39 for rotation therewith. Means, not shown, are provided for moving the clutch band 67 into engagement with the clutch member 65, whereby the retract cable drum 53 may be driven by the shaft 39 in a like direction of rotation.

Formed as an integral part of the hub 56 of the crowd cable drum 49 are two pair of radially extending brackets 69 that are diametrically opposed from one another, as shown in Fig. 5. Each pair of brackets is notched, as at 70, to receive trunnions 71 from the sides of the heads 72of eac-h of pair of cylinders 73. Each cylinder 73 is free to ro'ck within the associated notches 7'1) and an inlet connection 74 at the after end is made with a flexible hose 75 through which a fluid under pressure may be introduc'ed to the interior of the respective cylinder 73 to work against a piston, that is not shown.

To provide a fluid pressure source an accumulator vessel 76 is mounted within the crowd cable drum'49, as is shown in Fig. 4, and a fluid line 77 that connects with the outlet of the accumulator vessel 76 extends touch of the hoses 75. Extending from the head 72 of each cylinder 73 is-a piston ram 78 each of which will be urged outwardly from its-respective cylinder 73 upon the introduction of a fluidunder pressure to within the cylinder 73. The end ofeach piston ram 78 carries a fitting 79 that'is disposed within asocket 80 attached to the retract cable drum'58 by a pair of brackets 81 and 82. A pin "83 passes through side walls of each'socket 80 and throu'gh the associated fitting 79 to retain the fitting 79 within the socket 80 and fixed with respect to the retract cable drum 58. a

Upon the piston rams 78 being moved outwardly from the cylinders 73 the sockets 80 will be displaced away from the brackets 69 and a rotational displacement between the cable drums 49 and 58 will occur. This angular displacement will be restricted by the crowd cable 29 and retract cable 32 which are wound about the drums 49 and 58in a fashion to lead from the drums 49, 58 in opposite directions. As the drums 49, 58 are angularly displaced by action of the cylinders 73 the cables 29, 32 are ,each wound upon the respective drums 49, 58 and placed in tension. With a suflicient tension in the cables 29, 32 the pressure in the cylinders 73 will be balanced. The radially inner faces of the sockets 80 are formed to present lobes 84 that will engage with and abut against a pair of radially extending stops 85 on the hub 56 of the crowd cable drum 49. The lobes 84 and stops 85 limit the angular displacement of the drums 49, 58 that may occur in response to the tensioned crowd and retract cables 29, 32. In Fig. the lobes 84 and stops 83 are shown in abutting position, as may be assumed upon rigging the cables 29, 32 and lines 21, 23 and before fluid pressure is introduced in the hydraulic cylinders 73. In the usual course of operation the lobes 84 and stops 85 will be separated by angular displacement sufficient to permit relative movement between the cable drums 49, 58in either direction.

The crowd cable and lines 23, 29 and the retract cable and lines 21, 32 are connected between the drum assembly 12 and the upper end of the mast 13 to form a closed circuit. This circuit has a geometrical perimeter defined by the crowd cable leading from the drum assembly 12 forwardly to and about the cable sheave 18 at the base of the mast 13 and hence along the upper face of the boom 9 where connection is made with the crowd lines 23, that pass about the sheaves 27 to a connection with the brackets 22 at the upper end of the mast 13. The circuit is continued from the brackets 20, also at the upper end of the mast 13, by the retract lines 21 that ex tend rearwardly and pass about a pair of the group of sheaves 30 to connect with the retract cable 32 that is in turn wound upon the drum assembly 12.

Toperform a digging stroke for the shovel 1 the clutch band 67 is engaged with the clutch member 65 to rotate the drum 58 for drawing in the retract cable 32. The mast 13 will rise and the crowd cable 29 will necessarily be drawn from the drum 49, which therefor rotates with the drum 58. The connections between the drums 49, 58 formed by the cylinders 73 and piston rams 78, urge the drums, as has been noted, to move relative to one another to retain both the retract and crowd cables taut. In this fashion the mast 13 may be raised to the position shown in phantom in Fig. 1, and the hoist cable 37 is simultaneously payed out to allow the dipper 34 to swing downwardly to the fore of the crawler frame 3,. as is also shown in phantom in Fig. 1.

Digging is now commenced by drawing in the hoist cable 37 to pivot the dipper stick 33 and dipper 34 about the connection with themast 13. This pivotal connection is disposedat .a substantial distance from the run of hoist cable 37 extending from the boom sheave 38 downwardly and rearwardly along the underside of the boom 9 to the dipper sheave 35. The moment arm for the digging force applied through the hoist cable 37 is consequently substantial and the digging action is materially enhanced over that of a shovel mounting the dipper stick directly upon the boom wherein the moment arm for the digging force will be quite small.

The operator coordinates the digging motion with a crowding motion effected by releasing the clutch band 67, that had been employed for retracting the mast 13,

as shown in Fig. l.

A raising, or lowering, of the mast 13 causes a change in the perimetrical length of the circuit defined by the crowd cable and lines 29, 23 and the retract cable and lines 32, 37. To accommodate for this variation the cable sheave 18 mounted at the lower end of the mast 13 will swing with a shift in tilt of the mast. 13, as is shown in Figs. 1 and 3. With a rise of the mast 13, the sheave 18 will move to a lower position, and consequently the required run of cable and line between the crowd cable drum 49 and the sheaves 27 on the boom 9 is increased. The increase compensates for a decrease that would otherwise occur in the amount of cable and line required to complete the circuit. Conversely, as the mast 13 is lowered the cable sheave 18 rises to effectively decrease the circuit length and compensate for increased length of cable and line otherwiserequired for the circuit.

It is not intended that the movements of the cable sheave 18 at the base of the mast 13 compensate precisely for the variations in circuit length caused by a shift of the mast 13. Such actual change in circuit length that may occur will be accommodated, however, through the.

action of the cylinders 73, which permit limited angular displacement to occur between the drums 49 and 58. If the circuit perimeter decreases the piston rams 78 move outwardly from cylinders 73 to draw in either, or both,

the cables 29, 32 and retain each under tension. On the other hand, an increase in circuit perimeter will cause more cable to be payed out than is wound in and the piston rams 78 will be retracted within the cylinders 73.

The crowding motion of the shovel of this invention is enhanced through a desirable employment of a mechanical advantage. As the dipper stick is raised and crowded forwardly the run of crowd line between the mast end brackets 22 and the sheaves 27 will assume a position at a substantial angle with both the mast 13 and dipper stick 33. The lower end of the mast 13 being fixed, and the forward end of the dipper stick being supported by the hoist cable 37, the downward pull of the retract lines 23 urges the mast 13 and dipper stick 33 toward a position of alignment with a toggle like action. The crowding force transmitted through the dipper stick 33 to the dipper 34 is of considerably greater magnitude than that applied through the crowd lines 23. Thus, to retain a loaded dipper in a raised and forwardly extended position the crowd cable and lines are called upon to apply a force to the dipper stick 33 that is considerably less than the crowding force applied to the dipper.

I claim:

1. In a power shovel the combination comprising a forwardly inclined boom, an upwardly extending elongate mast pivotally mounted at its lower end to permit forward and rearward movement of the upper end, a dipper stick pivotally secured to the upper end of and extending forwardly from said mast including a dipper at its forward end, drum means adapted to draw in and pay out line, a sheave on said boom forward of said mast, a crowd line connected at one end to said mast and extending to the forward side of the mast toward and about said sheave on said boom and hence to said drum means to be drawn in thereby for tilting the mast forwardly independently of said boom and be payed out thereby to permit rearward elevation of the mast, a retract line connected at one end to said mast and extending to the rearward side of the mast and hence to said drum means to be drawn in thereby for moving the mast rearwardly independently of said boom and be payed out thereby :to permit forward motion of the mast, and a hoist cable attached to said dipper extending upwardly to :said boom .for drawing the dipper upwardly to pivot the dipper stick about its connection with'said mast in a digging motion.

2. In a power shovel the combination comprising a forwardly inclined boom, an elongate mast 'pivotally mounted at its lower end and rising upwardly above said boom in a substantially common vertical plane whereby pivot may be made to cause forward and'rearward movement of the upperend of themastga dipper stick pivotally secured to the upper .end of .saidLmast and extending forwardly of said boom, a dipper .mounted on 'the forward end of said dipper stick to the front of said boom, a sheave on said boom, .drum means adapted to draw in and pay outline, 'a crowd line connected at one end .to said mast and extending to .the forward side of the mast toward and about said isheave .on said boom and :hence to said drum :means to be drawn in thereby for tilting the mast forwardly independently of said boom and to .be payed outthereby to permit .rearward.elevation .ofrthe mast, a retract line connected at one endzto said mast and extending to the rearward side of 'theamast and hence to said drum means to .be drawn in thereby for moving the mast rearwardly independently of said boom and to be payed out thereby "to permit 'forwardxmotion of the mast, and a hoist .cable attached to said :dipper extending upwardly to said boom .for .drawing the dipper upwardly to pivot "the dipper stick about its connection with said mast in adigging motion.

.3. In a power shovel the combination comprising a platform, a forwardly inclined boom rising from said platform, a sheave mounted by said boom, an elongate mast pivotally'mounted at its lower end to permit forward and rearward movement of the upper end, .a dipper stick pivotally connected to the upperend of "said'mast extending forwardly therefrom and terminating in a forward end mounting a dipper, a crowd line drum carried by said platform, a retract line drum carried by said platform, a crowd line connected at one end to'said mast and led to the front of the :mast toward and about said boom sheave and .hence toward said crowd line drum to be wrapped thereon, a retract line connected at one end of said mast running .rearwardly therefrom .eand hence toward .said retract line drum ;to..be wrapped thereon, a coupling between said crowd and retract line drums applying a bias force toithedrums urging a relative rotation between said drums whereby said ..crowd .and. retract lines would .both be wound upon the drums, and driving means for saidcrowd and retractline drums to selectively drive either of said drums to draw in theassociated line whereby theother of said linesis payedout from its respective drum and said'mastis pivoted to produce movement of the upper end thereof.

4. In a power shovel .the combination comprising a platform, a forwardly extending inclined boom secured to and rising from said platform, a mast pivotally mounted at its lower end and rising above said boom, a dipper stickincluding a dipper pivotally attached to the upper endof said mast extending acrosssaid boom with said dipper to the front of the boom, a crowd line drum mounted upon said platform, -a retract line drum mounted upon said platform, said drums .being coaxially arranged forrotation in a like direction, a sheave attached 6 tothe lower end of said mast displaced imposition with a motion of said mast about its pivot, a crowd line connectedat one end to'said mast running toward said boom and hence along said boom and aboutsaid sheave to an attachment with said crowd line .drum, a :retract line connected at one end to said mast running rearwardly from said mast and hence to an attachment with said retract line drum whereby a rotation of said drums in like direction will draw in one and pay out the other of said lines, a coupling disposed between said crowd line and retract line drums including bias means urging a limited angular displacement between said drums that draws insaid crowd and retract lines to retain the same taut and driving means for said drum for selectively rotating either of the drums to draw in the associated line and pay out the other line to pivot said mast and impart movement to said dipper stick and dipper, whereby said sheave is displaced to maintain the combined length of crowd and retract lines extending between said drums and connections with said mast nearly constant and said coupling permits of angular displacement between said drums to compensate for variation in the combined length of crowd and retract lines between said drums and mast and to-retain the lines taut.

5. in a power shovel, the combination comprising a forwardly inclined boom, an upwardly extending elongate mast pivotally mounted at its lower end .to permit forward and rearward movement of the upper :end, a dipper stick pivotally secured to the upper end of and extending -forwardly from said mast including a dipper at .its forward end, a sheave on said boom forward of said mast, a crowd line connected at one end to said mast and extending to the forward side of the mast toward and about said sheave on said boom, a retract line connected at one end to said mast and extending to therearward side of the mast, crowd and retract line actuating means to selectively draw in on saidlines for tilting the mast forwardly and rearwardly independently of said boom, and means for maintaining both ,crowd and retract lines taut notwithstanding changes in line geometry resultant from changes in the position of the mast.

6. The device of claimv5 -in which the means last mentioned comprises a line sheave about which said crowd line is reeved and means mounting said sheave .on ,the mast whereby the sheave partakes of mast movement and comprising a movement arm on which said sheave swings to take up and supply line slack when the mastis pivotaliy moved.

7. The device of claim 5 in which the crowd and retract line actuating means comprises drums, the .means last mentioned comprising means for displacing said drums about their axes of rotation to substantially maintain a predetermined tension insaid lines.

8. In a power shovel the combination comprising an inclined boom, an upwardly extending elongate mast pivotally mounted at its lower end to permit forward and rearward movement of its upper end, a dipper stick pivotally connected to the upper vend of and extending forwardly from said mast, a dipper thereon and ahoist cable attached to said dipper and extending upwardly to said boom, a crowd line sheave mounted on the boom forward of said mast, a crowd line connected to said mast and reeved about said sheave and means for tensioning said crowd line whereby to 'tend to draw the 'boomand mast toward each other.

References Cited in the file'of this patent UNITED STATES PATENTS

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