Abstract: An improved cone crusher for crushing rock and the like has a welded metal hardfacing pattern made by welding beads of chromium carbide or similar hardfacing material to selected portions of its crushing surfaces. Tungsten carbide particles are introduced into the weld puddle as the beads are deposited. Predetermined spacing is maintained between adjacent beads to expose portions of the crushing surfaces. The beads can be deposited in recessed grooves in the crushing surfaces for increased lateral support. In the preferred embodiment, the beads are welded in a concentric circular pattern on the mantle and bowl liner of the cone crusher.

Abstract: A method and apparatus for pulverizing into fine powder in one step scrapped difficult to crush plastics of fiber reinforced thermosetting plastics by using a rotating diamond wheel having diamond grits of rough grain size of more than 270 mesh on the outer surface, a pushing unit to press plastic materials against the diamond wheel above and a powder collector.

Abstract: The invention relates to apparatus for material bed comminution of brittle material for grinding, with two roll-like comminuting tools, in which the length:diameter ratio is in each case less than 1 and of which one tool is fixed and the other is mounted so as to be movable, wherein a working gap distance is maintained between the two comminuting tools in the unloaded starting position and the comminuted material for grinding is substantially pressed to form agglomerated scabs. In order to ensure a relatively low wear and a relatively maintenance-free operation the length:diameter ratio of the comminuting tools is less than approximately 0.3 and the diameter of the roll-like comminuting tools is chosen to be sufficiently great that the scab thickness is always greater than the working gap distance.

Abstract: A hammermill is presented which includes a plurality of hammers each presenting an arcuate striking profile. The hammermill includes a rotor having rods for swingable carrying the hammers thereon and a motor for rotating the rotor. The hammers are longitudinally spaced along the rotor and preferably helically arrayed thereabout. The hammers present a head and a body, the head having an arcuate striking face which may include a point. As the rotor turns, the hammers are free to swing on the rods and comminute material fed into the hammermill. The hammers preferably present symmetrical striking profiles whereby after one profile becomes worn, the position of the hammer on the rod may be reversed to increase the useful life thereof.

Abstract: An insertless perforated mill roll body adapted to be detachably sleeved upon a roller shaft for the grinding of a fluid-containing material such as sugar cane and extracting fluid such as sucrose juice therefrom. The insertless perforated mill roll body includes a plurality of shish-ke-bab-like fluid channel strings to be encased in the roll body, each fluid channel string including a hollow fluid channel preferably defined by a channel wall member which generally extends between the two axial ends of the roll body with a plurality of fluid passage members affixed thereto. The roll body is formed by casting a castable material such as cast iron or steel to enclose the fluid channel strings, whereupon a hollow center bore is provided to receive the shaft therethrough. Each fluid passage member contains at least one generally radially extending fluid passage to allow communication between the outer periphery of the mill roll body and the fluid channel.

Abstract: Grinding equipment for a Jordan refiner for grinding paper pulp having a rotating part in form of a truncated cone and a stationary part in the form of a hollow truncated cone, on which bar-shaped knives are arranged at predetermined angles with respect to the conical shell generating lines. To improve the grinding equipment of the refiner, a pre-grinding zone is arranged upstream of one or more fine grinding zones whose configuration and arrangement are adapted to the state and desired development of the fibers in the grinding stock flowing through the grinding equipment.

Abstract: Reinforcement sections are provided at an outer surface and at an inner surface of a tire for a roll wheel assembly used in a pulverizer for crushing a material such as coal. These reinforcing sections cause the tire to be asymmetrical and are located on the tire only at areas where the wearing of the tire is highly predictable. The reinforcing sections provided on the inner surfaces of the tire are provided directly opposite of the reinforcing sections on the outer surface for preventing the localized thinning of the tire and extending the time interval between rotation and/or replacement of the tires.

Abstract: At least one core hole is provided adjacent an edge of a rock crusher component and removably receives a connector capable of attachment to a lifting line. In one embodiment, the connector is a bolt and the core hole has an enlarged portion for receiving a nut in a non-rotating fit. The nut receives a set screw plug when the bolt is removed. In another embodiment a hook and eye member is employed and the hook portion thereof engages the enlarged portion of the core hole. The connector includes a bracket that connects it with a lift line.

Abstract: A rotary grinder employing blades is disclosed, which comprises a substantially cylindrical rotor, on the periphery of which is mounted, along certain regularly spaced apart generatrix lines, a plurality of identical blades of short length with respect to the length of the rotor, wherein the blades are disposed at a rate of one blade per generatrix line and so that two blades located on adjacent a generatrix lines present therebetween, longitudinally, a distance approximately equal to or greater than a length of blade.

Abstract: A paper shredding knife structure includes a number of zigzag disk-like knife blades, each having a sharp outer edge, mounted on a knife support shaft, one by one closely adjacent each other so as to define a number of rhombic spaces between any two adjacent blades. A roller, preferably comprising a resilient material outer coating, is mounted in such a way to allow the knife blades to be in tight contact engagement with the roller so that when the knife support shaft and the roller are rotated with a sheet of paper feed through therebetween, the zigzag blades cut the paper sheet into small rhombic pieces.

Abstract: An improved roll for a roller press capable of withstanding very high nip forces in a press nip for interparticle crushing including embedding a plurality of spaced wear-resistant surface members in the pressing surface of the roll which are of a material harder than the material of the roll surface surrounding the inserts and by varying the size and number and material properties of the embedded pieces, the wear of the press roll is matched to the materials to be comminuted to minimize wear and to match the wear profile along the roll with extended pressing use.

Abstract: A high pressure roller press formed between opposed cylindrical rollers mounted to perform interparticle crushing or product bed comminution in the nip and having pockets in the surface of a size to retain compressed fine grained material which is pressed in the nip with the compressed material in the pockets being retained for full revolutions of the rollers and coacting with hard portions between the pockets to form the product bed comminution against material passing through the nip and drawing material into the nip.

Abstract: At least one core hole is provided adjacent an edge of a rock crusher component and removably receives a connector capable of attachment to a lifting line. In one embodiment, the connector is a bolt and the core hole has an enlarged portion for receiving a nut in a non-rotating fit. The nut receives a set screw plug when the bolt is removed. In another embodiment a hook and eye member is employed and the hook portion thereof engages the enlarged portion of the core hole. The connector includes a bracket that connects it with a lift line.

Abstract: Wear-resistant armoring on the outer surface of a roller for a high pressure roller press capable of interparticle crushing of granular material wherein the armoring is composed of axially extending welding beads horizontally welded along the roller either without spacing from one another or with slight spacing.

Abstract: A one-piece pulverizing mill roller assembly and method of rebuilding the same. The roller assembly comprises a body, an integral hub portion and an integral circumferential outside tread portion which mates with an annular groove in a grinding table. The roller assembly is composed of a relatively lower hardness steel which will accept hard surface weld beads to rebuild the circumferential outside tread portion as it wears. The rebuilding can be performed in-place in the pulverizing mill.

Abstract: An arrangement for fastening a grindstone (1) of a pulp grinder to a rotatory shaft (2). In the arrangement, the radial forces acting on the grindstone are transmitted from the fastening flange (3) of the grindstone (1) to the rotatory shaft (2) by means of a support member (12) which transmits the radial forces from the fastening flange (3) through the support member (12) to the rotatory shaft (2) in such way that they do not substantially affect the threads (8), (9) of the nut (7) and the rotatory shaft (2).

Abstract: A feeding device comprising a pair of oppositely driven rotational bodies is provided as an auxiliary aggregate arranged upstream of a continuously working presser belt separating machine for separating flowable and non-flowable constituents mixed with each other, one of the rotational bodies including a set of coaxially arranged circular knives spaced with regard to each other, while the other one is shaped as a prismatic body having at least one vane, the latter being provided with radial slots into which the circular knives can intrude.

Abstract: A pulverizer roll wheel assembly comprises a bracket with an opening therein for fixing the outer end of a roller shaft. Bearings mount a roller wheel with pulverizing tire to the inner end of the shaft for rotation of the pulverizer. A lip seal assembly separates an oil space around the inner end of the shaft with an air space around the outer end of the shaft. A pop off relief valve normally positioned near the lip seal is repositioned to the outer face of the shaft for easier access. A cover extends over the relocated valve for extending the air space around the relocated valve.

Abstract: A one-piece pulverizing mill roller assembly and method of rebuilding the same. The roller assembly comprises a body, an integral hub portion and an integral circumferential outside tread portion which mates with an annular groove in a grinding table. The roller assembly is composed of a relatively lower hardness steel which will accept hard surface weld beads to rebuild the circumferential outside tread portion as it wears. The rebuilding can be performed in-place in the pulverizing mill.

Abstract: An apparatus for grinding hypodermic syringes or needles, IV needles and other medical waste into relatively fine particles. The apparatus includes a housing having a case therein defining an inlet and an outlet. A plurality of rotors are disposed in the case, and each of the rotors has a plurality of radially outwardly extending teeth therein which interact with teeth on the other rotors to grind the syringes or needles. A discharge valve is provided for controlling the flow of particles discharged from the case. The teeth on the rotors are longitudinally and circumferentially spaced. Generally, the teeth on at least one of the rotors extend between the teeth on another of the rotors. Also, the teeth on at least a pair of the rotors have angled sides which are angled in opposite directions such that the angled sides of the teeth on one rotor generally face, and are aligned with, the corresponding angled sides of the teeth on the other rotor.

Abstract: A shredding machine has a rotary cutter and a fixed cutter. The rotary cutter includes a cutter part with a spiral cutting edge and a flute, and a column part for rotatably holding by a holding member for rotation of the rotary cutter. The fixed cutter has a cutting edge contacting with the cutter part of the rotary cutter. In rotating the rotary cutter, longitudinal slips of documents are fed between the cutters so that the documents enter the flute of the rotary cutter to cut the slips into chips by cooperation between the cutting edge of the rotary cutter and the cutting edge of the fixed cutter.

Abstract: A two roll pressure developer for a microencapsulated web or medial material includes rolls which have a support shaft through the center, a hollow annular shell, and load-bearing elastomer material between the shaft and the shell supporting the shell and controlling the deflection of the shaft under development loads. The elastomer material is formed as a plurality of discrete annular segments with inside diameters mounted on the shaft and outer diameters mounted in the shell. The segments are distributed along the length of the shaft so as to provide the roll with a variable modulus of elasticity which is highest at the axial center of the shaft and lower at the ends. In one embodiment, the segments are identical in width and are varied in pitch or axial spacing. In another embodiment, the segments are spaced at the same pitch but are varied in axial thickness.

Abstract: An apparatus for improving the pulping characteristics of wood chips in which a pair of closely operating rolls are provided for supplying compressive force to chips passed therebetween, at least one roll having an aggressively contoured surface for causing chips to crack in the thickness dimension of the chip as compressive force is applied to the chip.

Abstract: An appliance for processing food items including a first housing and a second housing releasably attached to the first housing. The first housing has a handle to facilitate hand-held use. A cutting member is mounted in the second housing and apparatus is mounted in the first housing for driving the cutting member. The driving apparatus is connected to the cutting member and actuated by a switch. A locking member secures the two housings together and an alignment mechanism is provided to position the housings for proper operation of the locking member. In one embodiment the locking member is operatively connected to the switch so that when the appliance is turned on the two housing are simultaneously locked together. The cutting member is a plastic hollow frusto-conical housing with metal cutting blades integrally molded into the housing.

Abstract: A waste material shredder having a pair of counter-rotating cutter rollers with mutually meshing cutter disks mounted thereon, and fixed spacer members separating the cutter disks. Sheets of waste material are shredded into small chips by the action of sharp protruding teeth on the cutter disks which punch transverse slits and by subsequent shearing action between adjacent opposing cutter disks. Jamming of the shredder due to build-up of chips between the spacers is eliminated by a special configuration of the cutter disks, with chip clearance protrusions being formed between the teeth which act to completely remove the cut chips from the shredder, thereby overcoming a basic problem with prior art "cross-cut" type shredders.

Abstract: A grooved knife roller for paper shredders. The knife roller has helically extending grooves, wherein the lagging side of each groove in the direction of rotation of the roller and the circumferential surface of the roller include an acute angle to form a hook-like sharp point facing in circumferential direction for cutting paper material in the longitudinal and transverse directions thereof. The lagging side of the groove in the direction of rotation of the roller is rectilinear and is inclined so as to be directed against the direction of rotation of the roller. A transition portion of the groove immediately adjacent the lagging side of the groove is arc-shaped.

Abstract: In a roll grinding blade for the production of starch from starch plants such as potatoes and for the production of processed food or juice from root crops, fruits, vegetables or the like, the roll grinding blade comprises rhombic blade members having leading blade tips (5) formed at the top ends with an acute angle and cutting blade tips (6) formed at each of the edges where the side surfaces meet the upper and the lower surfaces and stacked by way of recessed grooves (7), and said stacked blade members are fitted to the circumference of a rotational roll. The number of the cutting blade edges (6) is increased by the stacking of the rhombic blade members which, coupled with the leading blade tips (5) of an acute angle, significantly improves the effect of grinding the matters to be processed.

Abstract: A waste material shredder having a pair of counter-rotating cutter rollers with mutually meshing cutter disks mounted thereon, and fixed spacer members separating the cutter disks. Sheets of waste material are shredded into small chips by the action of sharp protruding teeth on the cutter disks which punch transverse slits and by subsequent shearing action between adjacent opposing cutter disks. Jamming of the shredder due to build-up of chips between the spacers is eliminated by a special configuration of the cutter disks, with chip clearance protrusions being formed between the teeth which act to completely remove the cut chips from the shredder, thereby overcoming a basic problem with prior art "cross-cut" type shredders.

Abstract: A juice extracting mill roll is provided with a plurality of juice channels connected with a plurality of juice inlet passages. The juice inlet passages have a longer dimension in an axial direction and a shorter dimension in a circumferential direction. Each juice inlet passage has a passage extension projecting into the juice channel to form a juice trap. Alternatively, a juice trap can be formed with each juice inlet passage intersecting the respective juice channel at a leading or lagging portion of the juice channel relative to the direction of rotation of the roll, and the opposite lagging or leading portion of the juice channel being shut off from the juice inlet passage.

Abstract: An apparatus and method for the comminution of plant matter, particularly of moist plant matter, for the production of corn cob mix, for example, provides that a rotor is rotationally mounted in a housing and provided with a drive, the rotor carrying movable blades and the housing carrying stationary blades so that there is a mutual interaction of the blades for comminution. The moving blades are slanted back in the direction of motion of the rotor. The blades are formed of sheet steel preferably manufactured by punching and have a thickness of 0.3 through 3 mm, preferably 0.5 through 1 mm. The comminution occurs in such a manner that the plant matter is non-uniformly accelerated and pre-comminuted between a plurality of high-speed intercutters moving a circular orbit and is finish-comminuted by a plurality of outer-stationary cutters.

Abstract: A rotary shearing/cutting machine, capable of comminuting article of many diverse materials and widely varying dimensional characteristics (i.e., plastic barrels and other containers, plastic and metal films, rubber tires, etc.) has four rotary driven shafts extending across a comminution chamber in parallel spaced relation to each other, with two center shafts rotating in opposite directions and with the shafts rotating at different speeds; a series of primary shear blades interspersed one-for-one with a series of secondary cutter blades are mounted on each shaft for rotation therewith, each shear blade projecting into the space between the shear blades on any adjacent shaft in close overlapping proximity thereto. Each shear blade and each cutter blade is of disc-like configuration having at least one radially projecting C-shaped cutting element affording a transverse cutting edge facing in the direction of rotation; the cutter blades are substantially smaller in diameter than the shear blades.

Abstract: A method of producing a long-life roll for a rolling mill manufacturing a rolled sheet having brightness. At least the surface of the roll barrel is made of steel containing carbide, the average grain size of which is not greater than 0.6 .mu.m, and the areal ratio of the carbide in the matrix is 6-30%. The roll is manufactured by canning steel powder produced by an RST process into a metal cylindrical container in a vacuum, sintering the powder in the cylindrical container by hot isostatic pressing, working the sintered body into the cnfiguration of a roll by machining and further giving it a heat treatment and finishing work. The roll and a rolling mill incorporating the roll are also disclosed.

Abstract: A waste material shredder having a pair of counter-rotating cutter rollers with mutually meshing cutter disks mounted thereon, and fixed spacer members separating the cutter disks. Sheets of waste material are shredded into small chips by the action of sharp protruding teeth on the cutter disks which punch transverse slits and by subsequent shearing action between adjacent opposing cutter disks. Jamming of the shredder due to build-up of chips between the spacers is eliminated by a special configuration of the cutter disks, with chip clearance protrusions being formed between the teeth which act to completely remove the cut chips from the shredder, thereby overcoming a basic problem with prior art "cross-cut" type shredders.

Abstract: An alloy characterized by its highly abrasive resistant qualities which render it particularly suitable for use as the material from which to fabricate the external surface of a grinding, i.e., pulverizer, roll (18) of the type that is designed to be employed in a bowl mill (10) so as to be operative therein for purposes of effecting the pulverization of a material such as coal through the coaction of the grinding roll (18) with another surface (14) with which the bowl mill (10) is provided for this purpose. The subject alloy which is capable of being cast or applied to the grinding roll (18) in the form of a weld overlay comprises, by weight percentages, 4.0-6.0% Carbon; 3.0-14.0% Manganese; 1.0-2.5% Silicon; 15.0-30.0% Chromium; and 4.0-6.0% Molybdenum; with 0.5-2.0% Boron being added thereto, the balance being iron and incidental impurities.

Abstract: A stone roller for paper making machines having a tubular body made of stone with an axial borehole. A plurality of tie-rods extend along the inner wall of the borehole and parallel to its axis. The tie-rods are used to clamp plates against the two ends of the roll body. A corepiece, sealingly connected to both clamping plates, is disposed within the borehole, creating an annular space sealed off from the central region of the bore. The tie-rods extend through the annular space. The space is filled with a plastic which is introduced in liquid form at room temperature and then hardened. The hardened plastic prevents the tie-rods from vibrating and shields them from corrosive elements.

Abstract: The cutting arrangement for a paper shredder consists of two cutting rolls with interengaging star-shaped cutting discs. The points of the teeth of the cutting wheels extend approximately up to the groove base of the grooves adjacent cutting discs on the other roll. The cutting rolls, which in each case are arranged synchronized "tooth to gap" have an effective intersection surface relative to one another the real overlap between them which is substantially smaller in area than the overall theoretical intersection surface, i.e. the lenticular overlap between the outer peripheral circles of the cutting discs.

Abstract: A roller mill in which raw material fed between the upper surface of a pulverizing table and a pulverizing roller is pulverized by compression therebetween, wherein at least one annular recess coaxial with a roller shaft being formed on the pulverizing roller, thereby attaining reduction of self-excited vibrations of the roller mill and improvement of the pulverization efficiency. Further, in order to enhance these effects, the depth of the recess is set larger than the average grain size of the raw material. Moreover, the gap between the pulverizing table and the pulverizing roller has a wedge-like sectional shape which becomes narrower toward the outside of the pulverizing table, whereby the raw material which has been pulverized by compression between the table and the roller is prevented from escaping in the axial direction of the roller shaft, thereby attaining reduction of the self-excited vibration and improvement of the pulverization efficiency.

Abstract: A lamp crushing machine comprises a casing which may be divided into upper, central and lower zones. Lamps which are to be disposed of are loaded into the upper zone. In the central zone there is a horizontally mounted drum with a number of radial vanes and possibly also circumferential vanes. When this drum is rotated the lamps are progressively broken by the shearing action of the vanes as they pass close by the edges of walls which project inwardly from the casing. Unbreakable parts such as lamp and caps are carried around the drum in pockets arranged between the vanes. The debris falls into a hopper in the lower zone which can be removed and emptied periodically. Throughout operation of the machine the lamps are doused by water issuing from a nozzle to quench any igniting sodium. Dangerous vapors pass out through special vents and other contaminents are filtered out of the water draining from the machine.

Abstract: A vertical type roller mill for grinding a material including a grinding table and grinding rollers of a tire shape in contact with each other. The grinding table has a grinding surface composed of a surface portion constituting a portion of an imaginary conical surface having a apex located on a center axis of the table, and a curving surface portion located outwardly of and contiguous with the surface portion constituting the imaginary conical surface. The grinding rollers each have a grinding surface composed of a surface portion constituting a portion of another imaginary conical surface sharing the apex with the first mentioned conical surface, and a curving surface portion located outwardly of and contiguous with the surface portion constituting a portion of the last mentioned imaginary conical surface and having a greater curvature than the curving surface portion of the grinding surface of the grinding table.

Abstract: An alloy characterized by its highly abrasive resistant qualities which render it particularly suitable for use as the material from which to fabricate the external surface of a grinding, i.e., pulverizer, roll (18) of the type that is designed to be employed in a bowl mill (10) so as to be operative therein for purposes of effecting the pulverization of a material such as coal through the coaction of the grinding roll (18) with another surface (14) with which the bowl mill (10) is provided for this purpose. The subject alloy which is capable of being cast or applied to the grinding roll (18) in the form of a weld overlay comprises, by weight percentages, 4.0-6.0% Carbon; 3.0-14.0% Manganese; 1.0-2.5% Silicon; 15.0-30.0% Chromium; and 4.0-6.0% Molybdenum; with 0.5-2.0% Boron being added thereto, the balance being iron and incidental impurities.

Abstract: A shredding apparatus is disclosed, which comprises rotary cutting disks and back plates. The rotary cutting disks each have peripheral edges serving as blades. The rotary cutting disks serve to shred sheets in the direction in which they are withdrawn. The rotary cutting disks each have large tooth portions formed on the outer periphery at a uniform circumferential spacing for co-operation with a back surface of the associated back plate to cut the sheets in the direction perpendicular to the direction of their withdrawal, they also each have small tooth portions formed on the outer periphery between adjacent large tooth portions, the small tooth portions being co-operative with the back surfaces of the associated back plates to compress chips produced as a result of shredding.

Abstract: A replaceable roll for mounting on a tapered threaded shaft of a roller mill includes a generally cylindrical roll member of wear-resistant cast material having an axial bore defined by a central bore wall portion raised with respect to a first bore end wall portion and recessed with respect to an opposite second bore end wall portion. The first bore end wall portion is of a preferably noncircular, polygonal configuration and receives a removable complementary annular end insert which abuts an annular shoulder formed at the interface of the central bore wall portion and first bore end wall portion. The bore of the end insert and the second bore end wall portion are axially tapered to correspond to the taper of the shaft onto which the roll is to be mounted. The taper of the second bore end wall portion forms a progressive continuation of the taper of the bore of the end insert for receiving the tapered threaded shaft.

Abstract: The disclosure is directed to an improved roll crusher comprising a central hub mounted on a rotatable shaft, a roll member carried by the hub in concentric relation thereto, and a pair of clamping rings for securing the components together. The roll member and hub have angular surfaces disposed in opposed relation to define a pair of annular, axially facing recesses having V-shaped sides. The clamping rings are constructed to fit into the recesses, each defining inner and outer circumferential surfaces which are angled to correspond to the angled surfaces of the hub and roll member. A plurality of equiangularly spaced bolts connect the clamping rings and hub, drawing the clamping rings toward each other to wedge the roll member radially outward relative to the hub. As a result, the roll member is fixed in a centered, balanced position relative to the hub. A plurality of lugs and lug receiving recesses cooperate to prevent relative rotation between the roll member and hub.

Abstract: A grinding roller for roll crushing mills, in which the axle is retained in a roller amount provided with a barrier air connection. The axle, furthermore, carries a roller hub connected with a roller shell, over inner bearings lubricated by splash lubrication. A measuring sensor reaches into the oil sump and is led through a core bore in the axle. End faces of the axle are surrounded by covers placed on the roller hub and on the roller mount while leaving gaps. Bores connect the respective gaps with the core bore, and these bores pass from both facing ends through the axle. One of the bores extending out from the rspective gap facing the interior of the mill, passes above the oil level and parallel to the oil surface. An extension pipe having a ventilating filter therein, is placed on the bore line on the side of the roller mount.

Abstract: Method and apparatus for comminuting a tree stump in its entirety while still rooted in the ground, utilizing a large, heavy cylindrical roller or drum rotating at high speed and having cutters mounted on a peripherical surface thereof for engaging and comminuting the stump from the side thereof. The roller is journaled for rotation about a horizontal axis in a carrier attached to the front end of a heavy four-wheel vehicle which is driven hydraulically over the ground surface from a selfcontained power source such as an internal combustion engine. The hydraulic system which drives the vehicle also includes a hydraulic motor mounted on the carrier for rotating the roller. The roller, through the carrier, is mounted to the vehicle frame for swinging movement in a vertical plane relative to the ground and a hydraulic cylinder included in the hydraulic circuit is provided for effecting said vertical swinging movement.

Abstract: Method and apparatus for comminuting a tree stump in its entirety while still rooted in the ground, utilizing a large, heavy cylindrical roller or drum rotating at high speed and having cutters mounted on a peripherical surface thereof for engaging and comminuting the stump from the side thereof. The roller is journaled for rotation about a horizontal axis in a carrier attached to the front end of a heavy four-wheel vehicle which is driven hydraulically over the ground surface from a selfcontained power source such as an internal combustion engine. The hydraulic system which drives the vehicle also includes a hydraulic motor mounted on the carrier for rotating the roller. The roller, through the carrier, is mounted to the vehicle frame for swinging movement in a vertical plane relative to the ground and a hydraulic cylinder included in the hydraulic circuit is provided for effecting said vertical swinging movement.