Abstract: A modular dethatcher and seeder includes a housing having a rear opening, a removable rear cover substantially closing the rear opening, and a plurality of tines driven by a motor to rotate about a shaft within the housing. When the device is to be used as a seeder, a seeder attachment is inserted into the rear opening of the housing in place of the rear cover. The seeder attachment can be driven by the rear wheels of the device. Alternatively, when the device is to be used as a dethatcher, a chute can be removably attached to the rear opening and a collection bag is then attached to the chute to hold debris thrown by the tines.

Abstract: In the field of clearance of unexploded ordnance from land, there is a need for an improved apparatus for removing unexploded ordnance from the ground. A cutting apparatus includes a plurality of blades on a rotatable shaft, the blades being tapered towards their distal ends. When the blades are driven forwardly through soil while the shaft rotates, they tend to loosen items such as solid ordnance and bring such items to the soil surface. The blades simultaneously sever scissile matter in the soil, thereby facilitating removal of the ordnance. The cutting assembly includes a conveyor for conveying unexploded ordnance away from the soil. The cutting assembly may be mounted on a vehicle including further means for rendering harmless the unexploded ordnance.

Abstract: An edging and trimming apparatus for a lawn sprinkler head includes an elongate rotary shaft carrying an annular rotary blade at a lower end thereof. The opposite upper end of the shaft is releasably interconnected to a rotary auger motor. The motor drives the shaft axially and rotates the blade to perform edging and trimming of the grass surrounding a standard sprinkler head.

Abstract: An electrically powered lawn edger (10) having a wire wheel (26) specifically adapted for edging and trench cutting applications. The wire wheel includes pairs of twisted wire brush segments (34) which are held within a hub (32) of the wire wheel. The pairs of brush segments are spaced apart radially around a peripheral edge of the hub to produce evenly spaced gaps (36). The gaps help to prevent the edger from “loading up” with dirt and/or turf when edging or cutting a trench and possibly stalling the edger motor (21). A washer (40) having a key shaped boss (44) keys the wire wheel to an output spindle (21a) of the motor to prevent slippage of the wire wheel.

Abstract: The present invention is a self-propelled ground aerating system. The system comprises, in general, a wheeled platform that has disposed thereon a power pack, a steering mechanism, a hopper for distributing materials, and a spiked drum. The spikes disposed on the drum are selectively positioned to engage the ground at a selected angle. The depth of penetration of the spikes into the ground may also be selected. The power pack provides the required power to a drive mechanism which in turn provides power to rotate the spiked drum thus propelling the present invention.

Abstract: Implements for attaching to a hand-held, powered “Weed-Eater” type device to perform various work or chores (filament cutting, blade cutting, brushing, blowing, mixing, etc.). After disconnecting the device's original implement typically a spool of filament (6) with a bumper feed (7), an initial, cultivator/cutter implement (10), cylindrical in shape with a substantially solid, circular top (12) and a relatively thin, continuous wall of constant thickness, is attached by an appropriate threaded member (e.g. a nut or bolt, usually with one or more washers) to the bottom end of the powered device (FIGS. 1A-D) through a central opening (13). The cultivator's top includes a series of circumferentially spaced, “snap-in” openings (14; e.g. two or more) through and into which other implements (e.g. those of FIGS. 3-20) can be attached (FIGS.

Abstract: A hand-held portable lawn and garden tool having implements. A housing encloses a motor and at least two sets of gears arranged in cascade to provide low speed and high torque to the implements. Each set of gears is a sun gear with a plurality of planetary gears. Embodiments energized by battery packs, line power and internal combustion engines are disclosed.

Abstract: A method for increasing effectiveness of mine clearance when clearing landmines. A vehicle-mounted, mechanically driven, rotary cultivator type demining tool is provided. The demining tool includes a horizontal shaft, a demining unit rotating around the horizontal shaft, a plurality of parallel demining discs located at a distance from each other and rotating around the shaft which when the demining tool is in operation cut down into an upper ground layer to a pre-determined depth to cause mines in their path to detonate or to fragment into harmless fragments, and impact devices located between the demining discs for working the upper ground layer between the demining discs such that the impact devices impact with the upper ground layer between each pair of demining discs several times per rotation of the demining tool. An upper ground layer where mines may be deployed is worked with the demining tool.

Abstract: A method and apparatus for producing a plurality of spaced apart cultivated spots in soil. A spot cultivator (1) is moved across the soil in a direction in which the spaced apart cultivated spots are to be formed. The spot cultivator (1) includes at least one tilling shaft (7) which is mounted to roll about a horizontal axis which moves with the spot cultivator (1) and which is rotatable about a longitudinal axis of at least one tilling shaft (7). At least one tilling shaft (7) is rolled about said horizontal axis in a plane which intersects the soil. The at least one tilling shaft (7) has a length sufficient to contact and penetrate the soil at a controlled spacing during each rotation about the horizontal axis.

Abstract: Equipment for digging ground in urban areas includes a hinged support and maneuvering arm (3), an omnidirectional damping device (36), a vibration or oscillation generator (38), a motor (40) and a tool (28) which is made to rotate by the motor and provide with a helical structure with a tip (28B) designed to penetrate in screw fashion into the ground and act thereon it by the vibrations received, so as to dislodge it and break it up.

Abstract: The present invention is a walk-behind power unit stabilizing system for use on portable trenchers and other equipment. The preferred application comprises a retractable wheel assembly mounted at the rear of a trencher where the invented device is allowed to be maneuvered by the user from a lower, stabilization position to an upper, transport position. The device has a handle that allows the user to move the device from the upper, transport position to the lower, stabilized position, and vice versa, easily by raising and lowering the handle, either by hand or by moving the handle up or down using the user's foot. Some of the main benefits of the invented device include: ease of use; a reduction in the physical labor required to operate a trencher; stability; the ability to more consistently control the depth at which the trench is dug; an increased ability to traverse perpendicular trenches; increased force exerted on the boom when inserting the boom into the ground; and trench straightening.

Abstract: Ground clearing apparatus (10) and a method for transporting the apparatus are provided. The ground clearing apparatus (10) includes a plurality of ground clearing tools (20) attached to a rotating shaft (18). The ground clearing tools include a chain (22) having a plurality of links and a hammer (24) attached to one end of the chain (22). The rotation of the shaft (18) causes the hammer (24) to strike objects in its path and generally mill the ground surface.

Abstract: A turf aerator is provided with two separate shafts, each having a plurality of tines mounted thereon for aerating the turf. Each shaft is selectively connected to an output shaft of a motor mounted on the frame of the aerator by two separate drive trains, each having a clutch arrangement therein. A pair of control levers are mounted on a handle assembly for operating the clutches in each drive train. Thus either or both of the tine carrying shafts may be rotated to facilitate a turning operation of the aerator or facilitating the operation of the aerator while traversing a sloping surface.

Abstract: A method and apparatus for clearing debris is disclosed. More particularly, a method and apparatus for clearing manure and other material from under a feedlot fence row is disclosed. The apparatus is preferably mounted to a vehicle such as a skid loader. The apparatus consists of a mounting structure for affixing to a vehicle, a pivotally mounted arm affixed to the mounting structure, and a motor driven wheel rotatably mounted proximate a distal end of the arm. The wheel has a plurality of teeth or shanks extending therefrom for digging out debris from under a fence row and throwing the debris away from the fence. In practice, an operator may drive a vehicle parallel to a fence row and selectively pivot the wheel in and out between fence posts to clear manure out from under the fence.

Abstract: Apparatus for in-situ remediation of contaminant-bearing earthen material includes a generally cylindrical tined assembly; a housing for mounting the tined assembly for rotational motion; an hydraulic driver for delivering torque to rotate the tined assembly; and an additive supply system configured to drop an additive into the space defined by and along the length of the cylindrical tined assembly.

Abstract: A trencher has an adjustable depth arbor support mechanism. The depth control mechanism includes a linkage which normally controls the depth of the trench being dug, but which also will allow the arbor to retract from the ground if it hits an obstacle. Preferably, the arbor support mechanism is at least partially counterbalanced by a spring, to allow the arbor to retract without undo force. The trencher has two wheels equidistant on either side of the arbor, and a third steerable wheel at the front of the trencher in line with the arbor. The cutting teeth are mounted to the arbor using a variety of chucks and mounting brackets, so the width of the trench is adjusted by adjusting the chucks and mounting brackets used.

Abstract: A soil tiller is provided including a hand held, portable frame having a handle. Also included is a drive assembly having a power source mounted within the frame and a motor for rotating upon the receipt of power from the power source. Next provided is at least one tine assembly rotatable with respect to the frame and further connected to the motor for rotating coincidentally therewith.

Abstract: A vertical drive shaft lawn edger is disclosed having a non-integral flywheel with the edger engine. This allows for the interchangeability of different flywheels for the same engine or different engines. The flywheel disclosed is preferably a combination flywheel/drive pulley. The flywheel/drive pulley is mounted directly to the drive shaft of the engine. The drive pulley is mounted to the top side or bottom side of the flywheel. Preferably, the flywheel/drive pulley in an integral piece.

Abstract: Apparatus for in-situ remediation of contaminant-bearing earthen material includes a generally cylindrical tined assembly; a housing for mounting the tined assembly for rotational motion; an hydraulic driver for delivering torque to rotate the tined assembly; and an additive supply system configured to drop an additive into the space defined by and along the length of the cylindrical tined assembly.

Abstract: A clay surface scarifier includes a portable frame with a first axle and a second axle rotationally connected thereto. At least one scarifying blade, having a cutting edge orthogonal to the first axis, is attached to the first axle and rotatable therewith about the first axis. At least one scarifying blade, having a cutting edge orthogonal to the second axis, is attached to the second axle and rotatable therewith about the second axis. The axes of rotation of the first and second axles are intersecting.

Abstract: A lawn aerator has a series of tine assemblies spaced along a driven shaft driven by a motor. Each fine assembly has a plurality of tines for aeration extending in a substantially radial pattern about the driven shaft. The inner tine assemblies along the middle portion of the driven shaft are secured to the driven shaft to drive the aerator along the lawn as the driven shaft rotates. The outer tine assemblies adjacent to the ends of the driven shaft are rotatably mounted to the driven shaft. This permits the outer tine assemblies to rotate independently and thereby makes the aerator more maneuverable and easier to turn. Removable weights can be attached to either side of the aerator housing to help maintain a straight course when traversing a slope.

Abstract: A snow grooming devise is provided with a carrier frame consisting of at least one transverse supporting member and two longitudinal supporting members so that it is adapted to be attached to a vehicle with the aid of a coupling means. A vertically adjustable snow propeller and a smoothing board are mounted on the carrier frame. The carrier frame is mounted on said coupling means such that it is adapted to be pivoted about an essentially horizontal longitudinal axis and an essentially horizontal transverse axis. The snow propeller is dragged by the front ends of the longitudinal supporting members and is pivotably mounted thereon and the transverse supporting member is associated with the coupling means so as to support the carrier frame.

Abstract: A blade assembly for a lawn edging machine. The blade assembly includes a hub, at least two spaced-apart blade members having two or more blade arms extending radially therefrom, and a horizontal blade member connecting the two blade members at their radially extended arm ends.

Abstract: An implement for preparing a field includes a ground engaging device that allows the implement to be pushed or pulled on the field. The ground engaging device includes a reversible roller with projections joined to an outer surface thereof to engage the ground. The projections do not extend along the complete length of the roller but rather a portion thereof thereby reducing the power necessary to rotate the roller. The implement includes reversible guards for keeping the disturbed ground in front of the roller.

Abstract: The object of the invention is a soilworking rotary machine in which there are kinematic and shape soilworking elements that obtain a cultivation effect to open and turn the soil. The fundamental unit of the machine is the cultivation unit compounded to tillage sections. The tillage sections are built with blades joined to the common holder. The blades are twisted, the holder is cone shaped and tillage sections are positioned at approximately a 450.degree. angle to the direction of linear velocity. The tillage sections, together with a transmission and support wheels, is affixed to the common frame.

Abstract: A soil aerator comprising a planetary aeration system, a frame, an attachment mechanism and a drive unit to form aeration holes the soil aerator having an attachment mechanism to allow it to be attached to a conventional farm tractor, a friction drive pulley system to permit slippage to protect the drive train if the soil aerator hits an obstruction, an adjustment mechanism to set different angles of penetration of the aeration tools into the ground to allow use of the soil aerator on different soils such as loam, clay, soft dirt and the like and a spring system to absorb impact energy as the soil aeration tools penetrate the soil.

Abstract: A method and apparatus for filling holes which have been made in the ground, by causing a machine which includes a rotary rake at its extreme front end to pass over the ground. In the case in which the ground area planted with grass is a racecourse or equestrian training ground, the machine is preferably driven over the course in a direction opposite to the direction in which the horses have been moving, the rotary rake being driven so as to rotate with a forward velocity tangential to the ground. The machine also includes a soil consolidating device disposed behind the rotary rake to tamp the soil which is replaced in the holes by the rake so that the soil will remain in place.

Abstract: A gardening utility machine having a counter-rotation twin shaft system can perform multiple types of work required for gardening (tilling, soil removal, weeding, raking and shredding of leaves), snow/ice removal and for power de-thatching and mowing of lawn grass. This can be done by exchanging attachments on the counter-rotating twin shafts: if tines are installed on the twin shafts, soil tilling, weeding can be done; if auger blades with or without digging bits are in place instead, the machine can simultaneously till and remove soil or can remove ice/snow, or rake and shred leaves; if the front shaft is installed with a spiked roller and the rear shaft, a shearing reel, then the machine can power de-thatch and mow grass at the same time, and additional grass clipping mulching ability can be performed if a fan blower equipped with a mulching fan blade and a retractable bedknife is in place.

Abstract: There is disclosed a plow constructed for displacement, by a traction vehicle, a predetermined direction. It comprises a cultivator having a generally U-shaped frame with a pair of lateral arms parallel to the above direction and interconnected by a bight. The cultivator further has a soil-chiselling assembly mounted on and transversely between the arms, this assembly including a horizontal rotary shaft provided with longitudinally spaced sets of coplanar flat radial shares. The cultivator is mounted on retractable wheels movable between the first position, wherein the wheels engage the soil for displacement of said cultivator with the soil-chiselling assembly stands inoperative above the soil, and a second position, wherein the wheels are retracted and stand above the soil and the soil-chiselling assembly operatively engages the soil.

Abstract: A trencher for digging a trench having a vertical face and a sloping face. The trencher includes a frame and means for moving the trencher over the surface of the ground. A rotor is connected to drive means which rotate the rotor, thereby digging the trench. The rotor includes a longitudinal rotor member coupled to a transverse rotor member. The rotor may also include a plurality of teeth-like elements coupled to the transverse rotor member.

Abstract: A gardening utility machine having a counter-rotation twin shaft system can perform multiple types of work required for gardening (tilting, soil removal, weeding, racking and shredding of leaves), snow/ice removal and for power de-thatching and mowing of lawn grass. This can be done by exchanging attachments on the counter-rotating twin shafts: if tines are installed on the twin shafts, soil tilling, weeding can be done; if auger blades with or without digging bits are in place instead, the machine can simultaneously till and remove soil or can remove ice/snow, or rack and shred leaves; if the front shaft is installed with a spiked roller and the rear shaft, a shearing reel, then the machine can power de-thatch and mow grass at the same time, and, additional grass clipping mulching ability can be performed if a fan blower equipped with a mulching fan blade and a retractable bedknife is in place.

Abstract: There is provided a cultivator blade supporting structure including at least one cultivator blade having a shank and a blade portion, at least one blade holder having a cavity for removably receiving the shank of the cultivator blade, and a rotational driving shaft to which the blade holder is fixed, wherein at least a part of the cavity is defined by first confronting oppositely inclined interior surfaces and second confronting oppositely inclined interior surfaces which have a different inclination angle from the first inclined interior surfaces, so that contact portions of the shank are wedged between and into the first and second inclined interior surfaces when the rotational shaft rotates to cultivate the ground.

Abstract: A rotor tiller having a counter-rotating twin shaft system and counter-rotating digging means such as tines, paddles, or blades for efficient tilling of soil. In another embodiment, the tines on the twin shafts can be replaced by counter-rotating helical auger blades for removal of loose soil or snow. Furthermore, digging bits of suitable kind and size can be affixed to the helical auger blades for simultaneous digging/tilling and removing of soil, snow. This new design eliminates many problems associated with conventional tillers and increases the utility of the subject tiller.

Abstract: The farm machine 1 for working the soil comprises tools 21 each of which consists of a concave disk 47 provided with a plurality of spades 48 at its periphery. The concavity of the concave disk 47 is directed toward the forward end 12 of the rotor 16, considering the work direction 3 of the farm machine 1. A lateral stabilizing element 41 comprising at least one share 43 extends behind the rearward lateral end 11 of the frame 9 of said farm machine 1. The farm machine 1 also comprises support wheels 36, 38, one 36 of which extends in front of the forward lateral end 12 of said frame 9.

Abstract: The invention relates to a soil working device, comprising a substantially cylindrical soil working member, which is mounted between two main supporting arms for rotation about a substantially horizontal axis and is axially composed of a number of sections which are mutually connected and connected with two shaft end sections journalled in said main supporting arms respectively through couplings of the universal type, the coupling between each two sections being supported by an auxiliary supporting arm which extends into the travelling direction and pivotally engages a connecting bar extending between said main supporting arms parallel to and in front of said soil working member.

Abstract: A cultivating tool for a soil cultivating machine includes a holder adapted to be mounted on a rotatable shaft and having a generally U-shaped channel receiving a working implement. A pin is disposed in the channel, and the implement has a hook which receives the pin. Cooperable retainers in the channel and on the implement are cooperable for retaining the implement in the channel, the implement being mountable on the holder by hooking the hook on the pin and effecting engagement between the retainers, the implement being demountable from the holder by disengaging the retainers from the implement and unhooking the hook from the pin.

Abstract: A garden tiller tine assembly for use with a tiller assembly which includes a drive shaft having a longitudinal axis of rotation includes a rotary blade aligned at a predetermined angle with respect to the axis of rotation. The planar body of the rotary blade is angled at a dihedral angle with respect to a plane normal to the axis of rotation. Upon rotation of the tine assembly about the axis of rotation, the rotary blade oscillates laterally from side to side along the axis of rotation to cut a wider path through the soil than conventional rotary blades.

Abstract: A cultivation implement which is comprised generally of forward and rear thatching reels which rotate in opposite directions relative to each other under positive drive power from a tow vehicle, such as a tractor. Each reel unit is rotatably disposed in its own carriage or frame, which carriages are hingedly connected to each other and to said tow vehicle. Each carriage rides, when the implement is not in use, on free spinning road wheels. For use, each carriage may be selectively lowered from the non-use, raised, position to a lowered, in-use, position, by actuation of hydraulic means. To assure even and smooth operation of the implement while the reel units are engaging the ground, unique ground engaging members, or skids, are connected to each carriage and positioned relative to each said reel unit so as to be interengaged by the vertical blade members.

Abstract: The farm machine 1 for working the soil comprises tools 21 each of which consists of a concave disk 47 provided with a plurality of spades 48 at its periphery. The concavity of the concave disk 47 is directed toward the forward end 12 of the rotor 16, considering the work direction 3 of the farm machine 1. A lateral stabilizing element 41 comprising at least one share 43 extends behind the rearward lateral end 11 of the frame 9 of said farm machine 1. The farm machine 1 also comprises support wheels 36, 38, one 36 of which extends in front of the forward lateral end 12 of said frame 9.

Abstract: A wheeled vehicle having a pair of forwardly projecting support arms carrying a rotary dethatching drum. A volute housing encloses the upper portion of said dethatching drum and opens for tangential forward discharge above the drum. The drum includes axially-spaced blades mounted in circumferentially staggered array upon a polygonally cross-sectioned shaft. The drum is supported upon a vertically adjustable gauge roller used to set the working depth of the dethatching blades. The dethatching drum is driven in rotation from the wheeled vehicle. L-shaped lever arms project from the wheeled vehicle toward the dethatching drum and support a foot pedal subassembly which permits the dethatching drum and its housing to be lifted upwardly by foot pressure applied by the operator.

Abstract: A device for picking rocks from a field includes a frame which is mounted on a pair of wheels. A hitch is pivotally attached to the frame and is adapted for engagement with a conventional tractor. The offset of the hitch is adjusted by a hydraulic cylinder to adjust the tracking of the frame behind the tractor. A reel is mounted for rotation on the frame and is powered by a chain and sprocket drive from a rotary hydraulic motor. The reel has a plurality of radially extending spokes, each terminating in a stone picking rake formed by a plurality of spaced teeth. The elevation of the reel with respect to ground level is adjusted by a pair of hydraulic cylinders connected to a pivotal reel mounting frame. A depth stop mechanism is provided to lock the reel in an adjusted elevational position. In a first embodiment, a semi-cylindrical stone collecting box is mounted within the reel frame. As each of the reel spokes rotates to a top position, collected stones fall by gravity into the open stone box.

Abstract: The present invention entails an automatic soil sampling machine that is pulled through the field by a prime mover. A disk is utilized and is power driven by an internal combustion engine or other power source. About the outer circumference of the disk there is provided structure that effectively engages the soil as the disk is powered therethrough and flings the soil upwardly out of the ground into a rooster tail airborne configuration. A catching basket or container is mounted on the soil sampling machine and catches the soil particles being flung from the ground.

Abstract: The farm machine includes a frame 9, a hitching structure 4, a rotor 16 supported by the frame 9, and spades 21 mounted on the rotor 16. The active parts of the spades 21 are curved. The curvature of all of the spades 21 is directed in the same direction and toward the forward end of the rotor 16, considering the work direction 3.

Abstract: A rotary tilling device has a cutting device having a plurality of cutters each of which is rotatably mounted on a supporting member. The cutter has a vertical portion and a lateral portion at an end of the vertical portion and has edges on both sides of the vertical and lateral portions. The cutter is held by a stopper in a tilling position when rotated in a tilling direction, and is released in a grass cutting position when rotated in the opposite direction.

Abstract: The apparatus for making a substantially vertical slot in the ground in a step in making a sealing or supporting wall comprises a frame member, a supporting shield, at least two cutting wheels and a drive unit. The supporting shield is attached to the frame member and supports the cutting wheels and the drive unit. The cutting wheels are mounted on a common shaft and at least a portion of the drive unit is enclosed by at least one of the cutting wheels. A housing projecting pipe like on both of its opposing sides is attached to the supporting shield. Each of the cutting wheels have a hub which is mounted on a common shaft mounted in the housing. A hollow drive wheel is provided for the cutting wheels and is mounted advantageously on a stepped in seat on one of the hubs. It fits in the housing with play. The hollow drive wheel meshes with a plurality of drive gears each connected to a drive motor.

Abstract: A rotary tiling device has a cutting device having a plurality of cutters each of which is mounted on a supporting member at a base end thereof in such a manner that the cutter is rotatable about a first center. The cutter has a vertical portion and a lateral portion at an end of the vertical portion and has edges on both sides of the vertical and lateral portions. The base end has an arcuated periphery about a second center. The first center is offset from the second center, so that in grass cutting operation, the arcuated periphery is positioned in a position which is further outward than its position in the soil cutting operation.

Abstract: A road working machine for cutting into a road surface includes a power driven, cutting tooth carrying rotor comprising a plurality of rotor segments removably attached to a shaft to vary rotor width. Each of the segments includes a plurality of subsegments attached to one another and to the rotor by threaded fasteners. Rings supporting a higher concentration of cutting teeth angled toward the ends of the rotor can be secured to the endmost rotor segments for edge cutting. A cover for the rotor includes an adjustable baffle which may be secured at any of a plurality of positions in the cover to lie adjacent an end segment of the rotor in use regardless of the rotor width.

Abstract: There is provided a cultivator blade supporting structure. The structure comprises at least one cultivator blade comprising a shank and a blade portion; at least one blade holder having a hollow sleeve for removably receiving the shank of the cultivator blade; and a rotational driving shaft to which the blade holder is fixed, wherein at least a part of the sleeve for receiving the shank of the cultivator blade comprises confronting oppositely inclined interior faces between which the shank is wedged when the cultivator blade is rotated to cultivate the ground.

Abstract: A garden tiller tine assembly having an axle with a plate rigidly attached thereto. First blade structures are provided for engaging the soil and the blades are planar in configuration and have longitudinal axes. These blades are attached rigidly to the plate on one side in a plane obliquely disposed with respect to the horizontal axis of the axle, positioning a proximal edge of the first blade structure closest to the blade and a distal edge of the first blade farther from the plate than a proximal edge. Consequently, when the axle is rotated by a motor or the like in a first rotational direction, the proximal edge of the first blade will always be in front of the distal edge thereof whereby soil contact by the first blade will be thrown in a first lateral direction away from the plate. A second blade is attached to the other side of the plate.

Abstract: Cultivating tines, each having opposite cutting edge portions, are pivotably supported by mount brackets on a tine shaft reversibly rotatable about a horizontal lateral axis. One of the edge portions of each tine is positionable in a position rearward with respect to the direction of forward rotation, while the other edge portion is positionable in a position rearward with respect to the direction of reverse rotation. The edge portions differ in upstanding posture when positioned for rotation in the intended direction. The curved edge line of the reverse-rotation edge portion is more upstanding than that of the forward-rotation edge portion when coming into contact with the ground.