US3148917A

US3148917A - Ice grader having vertical rotary cutters

Info

Publication number: US3148917A
Application number: US109119A
Authority: US
Inventors: Roy E Thompson
Original assignee: Western Gear Corp
Current assignee: Western Gear Machinery Co
Priority date: 1961-05-10
Filing date: 1961-05-10
Publication date: 1964-09-15
Anticipated expiration: 1981-09-15

Description

Sept 15, 1964 R, E. THoMPsoN 3,148,917

ICE GRADER HAVING VERTICAL ROTARY CUTTERS Filed May l0. 1961 5 Sheets-Sheer 1 www \llllll/ N l) 0 0 0 0 0 0 0 *l cvag viator/295 Sept 15, 1954 R. E. THOMPSON 3,148,917

ICE GRADER HAVING VERTICAL ROTARY CUTTERS Filed May 1o. 1961 3 SheelZs--Sheeii 2 (Joa #wor/235 Sept. 15, 1964 R. E. THOMPSON ICE GRADER HAVING VERTICAL ROTARY CUTTERS 5 Sheets-Sheen 3 Filed May l0, 1961 i 4 l l n INVENToR. ,@os/ ZZ/OMPso/U Jafar/aga 2W BY United States Patent O 3,148,917 ICE GRADER HAViNG VERTICAL RTARY CU'E'IERS Roy E. Thompson, Los Angeles, Calif., assigner to Western Gear Corporation, Lynwood, Calif., a corporation of Washington Filed May 10, 1961, Ser. No. 109,119 6 Claims. (Ci. 299-25) This invention deals generally with grading equipment and, particularly, with an ice grading machine.

Airelds, especially military airfields, are now located in the far-Hung corners of the globe. The main requisite of an airfield, of course, is that it have smooth runways for take-off, landing, and taxiing.

In airfield locations of extreme cold, such as the Arctic, an ice eld is conveniently leveled and smoothed to form runways. These runways must be periodically cleared of snow and resurfaced to maintain them in the proper condition. An ice field may be leveled for purposes other than making a runway, of course. The leveled ice area may serve as a foundation for a building structure, for example, or as a storage area.

Insofar as I am aware, existing ice graders utilize a forward, horizontal, rotating ice cutter. This cutter is supported at its ends in bearings which are carried on supporting arms extending forwardly of the ice grading vehicle. Such supporting arms limit the maximum depth of penetration of the cutter into the ice to less than the cutting radius of the cutter. In many instances, this cutting radius is not suicient to achieve a properly leveled ice surface. For example, it may be necessary, to attain such a properly leveled ice surface, to cut through a solid wall of ice which may have a height exceeding the cutting radius of the horizontally disposed rotary ice cutter and possibly even approaching the diameter of the rotary cutter. The existing ice graders, with their outboard supporting arms for the rotary cutter, cannot penetrate such a solid wall of ice because of the interference between these arms and the side walls of the cut made in the ice by the cutter. With the existing ice grading equipment it is also diiicult to attain a uniform cutting depth.

It will be appreciated that during operation of an ice grader, a larger amount of ice chip debris is created by the action of the rotary cutter. In the existing ice graders of which I am aware, there is no provision for removing this debris continuously from the vicinity of the cutter. The necessity of removing the debris, however, is not too critical with the horizontal rotary ice cutter. In the present ice grader, on the other hand, anrappreciably greater amount of debris is created which must be continuously removed during an ice grading operation.

A general object of the present invention is to provide anice grading machine which avoids the above noted and other deficiencies of existing ice graders.

Another object of the invention is to provide an ice grading machine which is capable of an appreciably greater depth of cut than the existing ice grading machines and which can perform ice grading operations of which the existing grading machines are incapable, such as penetrating solid walls of ice.

Another object of the invention is to provide an ice grading machine which accurately maintains a uniform cutting depth.

Another object of the invention is to provide an ice grading machine of the character described having provision for removal of the ice chip debris produced by the machine in operation.

Other objects, advantages, and features of the invention will become evident as the description proceeds.

Briey, the objects of the invention are attained by 3,148,9i'? Patented Sept. l5., 1964 providing an ice grading machine equipped with a vehicle for moving over the ice Vtield to be graded and at least one and preferably three vertical, rotary ice cutters ahead of the forward end of the vehicle. These cutters are supported at their upper ends on a vehicle supported frame so that the permitted cutting depth attained with the machine is limited only by the axial length of the cutters. A relatively deep cutting depth is thereby attained.

When three rotary cutters are employed, one is located ahead of the other two and approximately on the longitudinal center line of the machine so that they cut a continuous wide path through the ice. The cutters are rotated in such a way that they tend to direct ice chips into the space between the three cutters. This ice chip debris is continuously removed from this space and delivered to the rear end of the vehicle, from whence it may be discharged into a truck for transportation to a suitable point of disposal, by a unique conveyor which extends along the underside of the vehicle. The forward end of this conveyor mounts a skid on which the rotary cutters of the machine are supported. In this way, an accurately uniform cutting depth is attained.

When the rotary ice cutters of the machine are cutting through a body of ice, the rotary cutters are subjected to numerous torsional impacts. For this reason, the present ice grading machine embodies a unique torsional drive for each rotary cutter, which drive absorbs the torsional impacts.

A better understanding of the invention may be had from the following detailed description thereof, taken in connection with the annexed drawings, wherein:

FIG. 1 is a view in perspective of a presently preferred embodiment of the present ice grading machine;

FIG. 2 is a top plan view of the ice grading machine of FIG. 1 on reduced scale and with the tractor of FIG. l shown in phantom lines for clarity;

FIG. 3 is a side elevation of the structure shown in FIG. 2;

FIG. 4 is an enlarged section taken along line 4 4 of FIG. 3;

FIG. 5 is an enlarged section taken along line 5 5 of FIG. 4;

FIG. 6 is an enlarged section taken along line 6 6 of FIG. 4; and

FIG. 7 is an enlarged section taken along line 7 7 of FIG. 4.

Referring rst to FIG. 1, and speaking generally, the illustrated ice grading machine comprises a mobile support shown as a vehicle 10 on which is mounted a vertically swingable frame 12. Rotatably mounted on the forward end of this frame, ahead of the vehicle 10 and with their axes of rotation vertical, are three

rotary icc cutters

14 and 16.

The

cutters

14 and 16 are driven from an engine 18 at the end of the vehicle in such directions that they tend to throw ice chips or debris into the space between the rotors. The debris is continuously carried from the cutters to the rear of the Vehicle by conveyor 20. A rear, upwardly inclined conveyor 22 receives the debris from the conveyor 20 and discharges it into a truck 100 for transportation to a suitable disposal point. The forward end of the conveyor 2i) serves as a skid on which the forward end of the frame 12 is supported to attain accurate control of the cutting depth of the

cutters

14 and 16.

The ice grading machine will now be described in great-er detail. Vehicle 1t) has been illustrated as comprising a self-propelled vehicle, namely, a Caterpillar tractor. It will become evident as the description proceeds, however, that the vehicle may be a specially designed, self-pr-opelled vehicle rather than a conventional dieser? vehicle, such as a Caterpillar tractor. ln the alternative, the vehicle may consist of a towed vehicle with wheels or skids.

Frame 12 is a generally open, rectangular structure which includes longitudinally extending arms 24. The rear ends of lthese arms are pivotally connected to the ends of a cross member 26 which is rigidly attached to the tractor frame by means of braces 2S. Frame 12 is thereby vertically swingable on the tractor vehicle 19.

At the forward ends of the arms 24, frame 12 comprises a hollow, supporting part 30. This part has a generally equi-lateral, triangular configuration and is rigidly attached, at two of its base apices, to the forward ends of the frame arms 24.

Referring to FiG. 5, part 3d will be seen to comprise a hollow, open-topped part 32, to the upper edges of the side walls of which is bolted a cover plate 34. Also, as shown best in FIG. 5, ice cutter 14 comprises a hollow, cylindrical drum 36. Extending across the inside of the drum is a circular ange 33. Flange 3S has a central hole in which is fixed a lbearing 40. Rigidly attached within the drum 36, adjacent its lower end, is a ring 42 to which is joined, by a conical wall 44, a second bearing 46.

Bearings

40 and 46 are rotatably fitted on a vertical, hollow supporting shaft 48. The upper end of this shaft extends through the lower wall of the supporting part 30 and is welded or otherwise rigidly joined thereto. Braces 50 may be placed, as shown, to lend rigidity to the supporting shaft 43. The reason why the supporting shaft 48 must be so rigid will become evident as the description proceeds. Fixed to the supporting shaft 48, above the upper drum bearing dil and below the lower drum bearing 46, are thrust bearings 52 which restrain the drum against axial movement on the supporting shaft.

A centrally bored plate 54 is fixed to the lower side of the drum ring 42. Extending through the central opening in the plate 54, and keyed to the latter, is the lower end of a drive shaft S6. The upper end of this drive shaft is keyed to a relatively large gear 58 which is rotatably mounted on the upper end of the supporting shaft;Y 4S.

From this description, it lis evident that ywhen the gear 5S is driven, the rotary cutter 14 is driven in rotation through the drive shaft S6. A study of FG. 5 will show that the drive shaft 56 is quite slender, in Vcomparison to the diameter of the cutter, for example, and has been even shown as being reduced in diameter to enhance the slenderness of the drive shaft. Drive shaft 56 is thus proportioned so that it will form a torsionally elastic connection between the gear 58 and the cutter. This torsional elasticity of the drive shaft is necessary to absorb the torsional impacts which occur on the cutter in operation.

The cutting action of cutter 14 is furnished by a mul-tiplicity of spikes 60 fixed to and extending outwardly from the cylindrical wall of the drum 36. Fixed to the lower end of the drum 36 are downwardly and outwardly inclined spikes 62. During operation of the machine, the spikes 60 cut through the ice wall confronting the cutter, while the lower spikes 62 perform not only this function but the additional function of facing or smoothing the yhorizontal ice surface exposed by the cutter.

As may be best observed in FIGS. 2 and 4,

cutters

14 and 16 are located at the apices of an equilateral triangle. Cutter 14 is located ahead of cutters 16 and approximately on the center line of the vehicle 10. Behind the cutter 14 are the two cutters 16 which are located at opposite sides of that center line. Cutters 16 are substantially identical and are rotatably mounted -on the supporting part 30 of the frame 12 in precisely the same way as described inV connection with cutter 14 and illustrated in FIG. 5. For this reason, it is not necessary to describe further these cutters 16 or their manner of support on the supporting part 30. Actually, the upper cutter 16 in FIG. 4 is identical to cutter 14, while the lower cutter 16 in FIG. 4 is identical with cutter 14 except that the spikes 66 on the latter cutter 16 extend in the opposite tangential direction from those on the cutter 14.

It will be observed that the center distance of each cutter 16 from the center line C is slightly -less than the sum of the cutting radii of the forward cutter 14 and the respective cutter 16. In this way, the three cutters are arranged to cut a continuous swath or path through the ice. It is obvious, of course, that lthe cutting diameters of the cutters must be such that the width of this path is somewhat greater than the width of the vehicle 1t) to permit the latter to travel in the path.

To theV upper ends of the drive shafts 56 of the two rear cutters 16 are fixed large gears 5S (FIG. 2) like that on the drive shaft of cutter 14. The gears 58 on the drive shafts of cutter 14 and the upper cutter 16 will be seen to be drivably coupled by an idler gear 64. Idler gear 64 is rotatably mounted within the supporting part 36 in any convenient way. From this description, it is evident that cutter 14 and the upper cutter 16 in FiG. 2 rotate in the same direction.

The

cutters

14 and 16 are driven as follows: Within the rear supporting member 26 is a rotary drive shaft 66. This shaft is driven from the engine 13. At its ends, shaft 66 mounts bevel gears 68. T hese bevel gears mesh with bevel gears 76 on the rear ends of two long, longitudinally extending drive shafts 72 within the frame arms 24. At their forward ends, shafts 72 are drivably connected to the two cutters 16 by means of gearing 74, stub shafts 76, and meshing

bevel gears

78 and 86 on the stub shafts 76 and the drive shafts 56 of cutters 16. As shown in FIG. 4, the forward cutter 14 and the upper rear cutter 16 in that figure are driven in counterclockwise directions of rotation, as the cuters are viewed in FIG. 4. The lower rear cutter is driven in a clockwise direction of rotation.

Because of their directions of rotation, the

rotary ice cutters

14 and 16 tend to throw ice chips into the space between the cutters, which chips would rapidly accumulate and produce a large quantity of debris between the rotors if the debris were not continuously removed during an ice surfacing operation. For this reason, the present ice grading machine is provided with conveyors 29 and 22 for removing the debris. As shown best in FlGS. 2, 3, 4, 6 and 7, conveyor 20 comprises a long conduit or frame member 82 on the longitudinal center line of the vehicle. This frame member is formed with two upwardly open channels or troughs 84. The forward end of the frame member 82 extends into the space between the

ice cutters

14 and 16. The side walls 36 of the troughs 84 terminate some distance from this forward end of the frame member. Accordingly, at the forward end of the member, the troughs 84 are laterally open to permit the ice debris to enter the forward ends of the troughs 84.

Within each trough 84 is a helical conveyor S8. These conveyors are rotatably mounted at 'their forward and rear ends in bearings 90. At their rear ends, the helical conveyors 88 are driven from the cutter drive shaft 66 through a chain drive generally denoted by the numeral 92. The helical conveyors are driven in the directions of rotation indicated in FIG. 7 to feed the ice debris entering the forward ends of the troughs 84 along the troughs to the rear ends of the latter.

The rear conveyor bearings 90 (only one shown) are located some distance from the rear ends of the troughs 84. The lower end of the rear, inclined conveyor 22 is located below the rear ends of the troughs 84. In this Way, the ice debris carried along the troughs by the helical conveyors 88 is discharged onto the lower end of the conveyor 22. Conveyor 22 comprises an endless conveyor member 94 having cross ribs 96. A chain drive 98 driven from the cutter drive shaft 66 drives the endless conveyor member 94 in the direction indicated in FIG. 3. Accordingly, the ice debris discharged onto the conveyor member 94 by the helical conveyors 8S is carried upwardly to the upper end of the conveyor member 22 from whence the debris drops into a truck 100. This truck travels along with the ice grader and, when lled, transports the debris to a sui-'table disposal point.

It will be observed in FIGS. 2 and 3 that the engine 18 is supported on two longitudinal frame members 102 which are welded or otherwise rigidly attached at their forward ends to the cross member 26 and are pinned or otherwise attached at their rear ends to the rear conveyor 22. Frame members 162, then, support the conveyor 22 in its inclined position.

At the forward end of the longitudinal conveyor frame member 82, the center rib 104 of the member is enlarged and projects some distance above the edges of the trough side walls 86 and the center rib 104, as indicated at 1%. The bottom wall 108 of the troughs S4 curves up and around the forward end of this enlarged rib portion 106 to form a skid 11G. During operation oft the grading machine, this skid rides on the surfaced ice behind the forward rotary ice cutter 14. Fixed to the upper edge of the enlarged rib portion 106 is a plate 112. Rotatably connected at its lower end to this plate is a jackscrew 114. Jackscrew 114 extends upwardly through the supporting part 30 of the hinged frame 12 and passes through an axially fixed, rotary nut 116 driven by a motor 11S. Motor 118 is controllable from the cab of .the Vehicle 10.

From this description, it is evident that the hinged frame part 3i), and the

rotary ice cutters

14 and 16 carried thereon, are supported on the skid 11i). By controlling the motor 11S, the frame part 30 and

ice cutters

14 and 16 may be raised and lowered. The pulpose of this adjustment is to achieve a uniform cutting depth. Such a uniform cutting depth is attained when the lower cutter spikes 62 are coplanar with the lower surface of the skid 110. Hence, the adjustment alforded by the lead screw 114.

In operation of the present ice grading machine, the vehicle is operated to move the

rotary ice cutters

14 and 16 over the ice surface to be leveled. It is obvious that the vertical disposition of the ice cutters enables the latter to penetrate any ice wall having a height not greater than the length of the cutters. This penetration depth is obviously appreciably greater than that of which horizontally mounted ice cutters are capable. As the cutters cut through the ice, the debris thrown into the space between the cutters is continuously carried away and deposited in a truck 160 by the conveyors 20l and 22. While in the illustrative embodiment, the ice debris is deposited in a truck for transportation to a suitable disposal point, the debris might be expelled or thrown to the side of the machine by a suitable blower or the like.

As the

cutters

14 and 16 move over the ice, the lower spikes 62 smooth off the horizontal ice surface exposed by the cutting action of the cutters. The cutters are raised or lowered, as required, by operation of the motor 118 to place the lower ends of the lower cutter spikes 62 in coplanar relationship to the lower surface of the skid 11i) so as to assure maintenance of a constant cutting depth. As mentioned earlier, the torsionally elastic drive shafts 56 for the rotary cutters absorbs the torsional impacts which are produced on the rotary cutters in operation.

Clearly, then, the invention hereinbefore described and illustrated is fully capable of attaining the several objects and advantages preliminarily set forth. While a presently preferred embodiment of the invention has been described and illustrated, numerous modifications in the design, arrangement of parts, and instrumentalities of the invention are obviously possible within the spirit and scope of the following claims.

What is claimed is:

1. A grading machine, comprising a mobile support having upper and under sides and front and rear ends, a. frame extending longitudinally of said support adjacent the upper side thereof, means pivotally connecting the rear end of said frame to said support for vertical swinging movement of the frame relative to the support, the forward end of said frame extending forwardly of the forward end of said support, a plurality of rotary cutters arranged below said forward end of said frame with their axes of rotation generally vertical, means rotatably mounting said cutters on said forward end of said frame, means for driving said cutters in rotation, a member extending longitudinally of said support adjacent the under side thereof, means pivotally connecting the rear end of said member to said support for vertical swinging movement of the member relative to the support, the forward end of said member extending forwardly of the forward end of said support, a skid on the forward end of said member for engaging a surface to be graded, means supporting said forward end of said frame on said forward end of said member with the lower ends of said cutters disposed at the approximate level of the under surface of said skid for engagement with the surface to be graded, and said cuters being offset laterally of said support to cut a path along said surface at least as wide as said support.

2. The subject matter of claim 1 wherein said frame extends along the upper side of said support to the rear end of the support and the frame is pivotally connected to the latter end of the support, and said member extends along the under side of said support =to the rear end of the support and is pivotally connected to the latter end of the support.

3. A grading machine, comprising a mobile support having upper and under sides and front and lrear ends, a frame extending longitudinally of said support adjacent the upper side thereof, means mounting said frame on said support, the forward end of said frame extending forwardly of the forward end of said support, three rotary cutters arranged below said forward end of said frame with their axes vertical and with their lower ends coplanarly disposed for engagement with a surface to be graded, one of said cutters being located approximately on the longitudinal center line of said support and the remaining two cutters being located rearwardly of said one cutter and at opposite sides of said center line so as to cut a path along said surface at least as wide as said support, a conduit extending longitudinally of said support along the under side thereof approximately on said center line, means mounting said Conduit on said support, the forward end of said conduit being located between and having lateral `openings facing said remaining cutters, the lower edges of said openings being located at the approximate level of the lower ends of said cutters, means for driving said cutters in rotation in such manner that the forward side of each of said remaining cutters rotates toward said center line, whereby rotation of said cutters tends to discharge material removed from the surface being graded into the forward end of said conduit through said openings therein, conveyor means in said conduit for conveying the material entering the conduit rearwardly through the latter, and the rear end of said conduit being open and located at the rear end of said support.

4. The subject matter of claim 3 wherein said conveyor means comprise rotary helical conveyor means extending longitudinally through said conduit.

5. The subject matter of claim 3 wherein the interior of said conduit is divided by a vertical, longitudinally extending wall, and said conveyor means comprises a pair of rotary helical conveyor members extending longitudinally through the conduit at opposite sides of said wall.

6. The subject matter of claim 3 wherein said frame mounting means comprises means pivotally connecting the rear end of said frame to said support for vertical swinging movement of the frame relative to the support and said conduit mounting means comprises means pivotally connecting the rear end of said conduit to said support for vertical swinging movement of the conduit 7 relative to the support, the forward end of said conduit having an under skid surface at the approximate level of the lower ends of said cutters, and means supporting the forward end of said frame on the forward end of said conduit.

References Cited in the le of this patent UNITED STATES PATENTS 721,697 Hanneborg Mar. 3, 1903 1,615,461 Lichtenberg Jan. 25, 1927 2,066,207 Lestina Dec. 29, 1936 8 Hargrove et al. Apr. 16, 1940 Lewis May 6, 1952 Hui Dec. 7, 1954 Newcomer July 5, 1955 Kozub Oct. 20, 1959 Wilcox Ian. 10, 1961 Aibley Sept. 4, 1962 FOREIGN PATENTS Australia Sept. 4, 1958 Germany July 11, 1957

Claims

1. A GRADING MACHINE, COMPRISING A MOBILE SUPPORT HAVING UPPER AND UNDER SIDES AND FRONT AND REAR ENDS, A FRAME EXTENDING LONGITUDINALLY OF SAID SUPPORT ADJACENT THE UPPER SIDE THEREOF, MEANS PIVOTALLY CONNECTING THE REAR END OF SAID FRAME TO SAID SUPPORT FOR VERTICAL SWINGING MOVEMENT OF THE FRAME RELATIVE TO THE SUPPORT, THE FORWARD END OF SAID FRAME EXTENDING FORWARDLY OF THE FORWARD END OF SAID SUPPORT, A PLURALITY OF ROTARY CUTTERS ARRANGED BELOW SAID FORWARD END OF SAID FRAME WITH THEIR AXES OF ROTATION GENERALLY VERTICAL, MEANS ROTATABLY MOUNTING SAID CUTTERS ON SAID FORWARD END OF SAID FRAME, MEANS FOR DRIVING SAID CUTTERS IN ROTATION, A MEMBER EXTENDING LONGITUDINALLY OF SAID SUPPORT ADJACENT THE UNDER SIDE THEREOF, MEANS PIVOTALLY CONNECTING THE REAR END OF SAID MEMBER TO SAID SUPPORT FOR VERTICAL SWINGING MOVEMENT OF THE MEMBER RELATIVE TO THE SUPPORT, THE FORWARD END OF SAID MEMBER EXTENDING FORWARDLY OF THE FORWARD END OF SAID SUPPORT, A SKID ON THE FORWARD END OF SAID MEMBER FOR ENGAGING A SURFACE TO BE GRADED, MEANS SUPPORTING SAID FORWARD END OF SAID FRAME ON SAID FORWARD END OF SAID MEMBER WITH THE LOWER ENDS OF SAID CUTTERS DISPOSED AT THE APPROXIMATE LEVEL OF THE UNDER SURFACE OF SAID SKID FOR ENGAGEMENT WITH THE SURFACE TO BE GRADED, AND SAID CUTERS BEING OFFSET LATERALLY OF SAID SUPPORT TO CUT A PATH ALONG SAID SURFACE AT LEAST AS WIDE AS SAID SUPPORT.

3. A GRADING MACHINE, COMPRISING A MOBILE SUPPORT HAVING UPPER AND UNDER SIDES AND FRONT AND REAR ENDS, A FRAME EXTENDING LONGITUDINALLY OF SAID SUPPORT ADJACENT THE UPPER SIDE THEREOF, MEANS MOUNTING SAID FRAME ON SAID SUPPORT, THE FORWARD END OF SAID FRAME EXTENDING FORWARDLY OF THE FORWARD END OF SAID SUPPORT, THREE ROTARY CUTTERS ARRANGED BELOW SAID FORWARD END OF SAID FRAME WITH THEIR AXES VERTICAL AND WITH THEIR LOWER ENDS COPLANARLY DISPOSED FOR ENGAGEMENT WITH A SURFACE TO BE GRADED, ONE OF SAID CUTTERS BEING LOCATED APPROXIMATELY ON THE LONGITUDINAL CENTER LINE OF SAID SUPPORT AND THE REMAINING TWO CUTTERS BEING LOCATED REARWARDLY OF SAID ONE CUTTER AND AT OPPOSITE SIDES OF SAID CENTER LINE SO AS TO CUT A PATH ALONG SAID SURFACE AT LEAST AS WIDE AS SAID SUPPORT, A CONDUIT EXTENDING LONGITUDINALLY OF SAID SUPPORT ALONG THE UNDER SIDE THEREOF APPROXIMATELY ON SAID CENTER LINE, MEANS MOUNTING SAID CONDUIT ON SAID SUPPORT, THE FORWARD END OF SAID CONDUIT BEING LOCATED BETWEEN AND HAVING LATERAL OPENINGS FACING SAID REMAINING CUTTERS, THE LOWER EDGES OF SAID OPENINGS BEING LOCATED AT THE APPROXIMATE LEVEL OF THE LOWER ENDS OF SAID CUTTERS, MEANS FOR DRIVING SAID CUTTERS IN ROTATION IN SUCH MANNER THAT THE FORWARD SIDE OF EACH OF SAID REMAINING CUTTERS ROTATES TOWARD SAID CENTER LINE, WHEREBY ROTATION OF SAID CUTTERS TENDS TO DISCHARGE MATERIAL REMOVED FROM THE SURFACE BEING GRADED INTO THE FORWARD END OF SAID CONDUIT THROUGH SAID OPENINGS THEREIN, CONVEYOR MEANS IN SAID CONDUIT FOR CONVEYING THE MATERIAL ENTERING THE CONDUIT REARWARDLY THROUGH THE LATTER, AND THE REAR END OF SAID CONDUIT BEING OPEN AND LOCATED AT THE REAR END OF SAID SUPPORT.