Stump grinding machine having improved cutting boom support structure

An improved stump grinding machine includes a frame structure having an engine mounted thereon. A boom has a proximal end and distal end and is pivotally mounted to the frame structure at its proximal end. A grinding wheel is rotatably mounted to the distal end of the boom. A power train arrangement transmits power from the engine to the grinding wheel. The power train arrangement includes an idler shaft rotatably mounted on the frame structure. The boom is pivotally mounted to the frame structure independently of the idler shaft.

BACKGROUND OF THE INVENTION
 The present invention relates generally to stump grinding machines of the
 type having a grinding wheel located at the distal end of a movable boom.
 More particularly, the invention relates to a stump grinding machine
 incorporating a novel support structure for pivotally mounting the boom to
 the machine's frame.
 Stump grinding machines are widely used to remove tree stumps. These
 machines are constructed having a grinding wheel located at the distal end
 of a movable boom. Typically, the grinding wheel is swept back and forth
 in a generally horizontal plane across the tree stump. With each sweep,
 the grinding wheel is lowered slightly to remove more of the stump. The
 final sweeps of the grinding wheel may be below ground level to ensure
 elimination of the entire stump.
 Often, stump grinding machines have a wheeled frame structure to facilitate
 movement of the machine from place to place. The frame may be
 self-propelled or configured for towing behind a separate vehicle. An
 engine, typically a gasoline or diesel engine, located on the wheeled
 frame generates power to drive the grinding wheel.
 The grinding wheel generally receives power from the engine through a
 series of belts. In one known arrangement, a first belt connects the
 engine output to a rotatable idler shaft. A second belt is connected
 between the idler shaft and the grinding wheel. The idler shaft thus
 rotates at very high speeds to transmit power to the grinding wheel.
 In addition to facilitating the transmittal of power from the engine to the
 grinding wheel, the idler shaft serves to pivotally support the machine's
 boom. To allow the idler shaft to rotate, the boom is mounted about the
 rotating idler shaft by bearings. Such an arrangement is disclosed in U.S.
 Pat. No. 6,003,570 entitled "Stump Grinder Machine Having Turntable
 Mounted Engine Arrangement," incorporated herein by reference.
 Arrangements utilizing an idler shaft to transmit power to the cutting
 wheel have worked generally well for their intended purpose. It has been
 found, however, that vibrations generated at the stump grinding wheel may
 be transmitted to the bearings used to support the boom on the idler
 shaft. The combination of vibration and the rotational speed of the
 bearings' inner race gives rise to various maintenance considerations.
 SUMMARY OF THE INVENTION
 The present invention recognizes and addresses the foregoing
 considerations, and others, of prior art constructions and methods.
 Accordingly, it is an object of the present invention to provide a novel
 stump grinding machine.
 It is a further object of the present invention to provide a stump grinding
 machine having a novel support structure for pivotally mounting the boom
 to the machine's frame.
 It is a more particular object of the present invention to provide a novel
 support structure for pivotally mounting the boom to the machine's frame
 which isolates rotation of the idler shaft from the pivoting motion of the
 boom.
 Some of these objects are achieved by a stump cutting apparatus including a
 frame structure supported by at least one wheel to facilitate movement of
 the stump cutting apparatus from place to place. An engine is supported by
 the frame structure. A boom having a proximal end and a distal end is
 pivotally mounted to the frame structure at its proximal end. A grinding
 wheel is rotatably mounted to the distal end of the boom.
 The stump cutting apparatus further includes a power train arrangement for
 transmitting power from the engine to the grinding wheel. The power train
 arrangement includes an idler shaft mounted on the frame structure for
 rotation so as to be coaxial with the pivot axis of the boom. The boom is
 pivotally mounted to the frame structure independently of the idler shaft.
 In some exemplary embodiments, a boom tube fixed to the proximal end of the
 boom surrounds the idler shaft. Additionally, the boom tube may be
 supported by at least one bearing. For example, the boom tube may be
 supported by two bearings. In some exemplary embodiments, the idler shaft
 may be rotatably supported by two bearings coaxial with a pivot axis of
 the boom. Additionally, the boom bearings may be located between the idler
 shaft bearings.
 Preferably, the power train arrangement includes a first belt stage
 transmitting power between the engine and the idler shaft and a second
 belt stage transmitting power between the idler shaft and the grinding
 wheel. The first belt stage may include an engine pulley wheel, a first
 idler shaft pulley wheel fixed to the idler shaft and coaxial with the
 pivot axis of the boom, and a first belt transmitting power between the
 engine pulley wheel and the first idler shaft pulley wheel. The second
 belt stage may include a second idler shaft pulley wheel coaxial with the
 pivot axis of the boom fixed to the idler shaft, a grinding wheel pulley
 wheel, and a second belt transmitting power between the second idler shaft
 pulley wheel and the grinding wheel pulley wheel. In addition, the
 bearings supporting the idler shaft and the boom may be located between
 the first and second belt stages.
 In some exemplary embodiments, the frame structure includes a turntable
 assembly mounted for rotational movement in a first plane. The boom may be
 pivotally mounted on the turntable assembly for movement in a second plane
 generally perpendicular to the first plane.
 In some preferred embodiments, the engine is gasoline powered and the
 bearings for mounting the boom and idler shaft to the frame structure are
 tapered roller bearings. Additionally, the first belt stage may include a
 multiple v-belt and the second belt stage may include a poly-chain.
 Other objects of the invention are achieved by stump cutting apparatus
 including a frame structure supporting an engine. The engine includes an
 engine pulley wheel rotationally driven by the engine. A boom having a
 proximal end and a distal end includes a boom tube pivotally mounted to
 the frame structure by at least one first bearing. A grinding wheel is
 mounted for rotation to a grinding wheel shaft at the distal end of the
 boom. An idler shaft, extending through the boom tube, is rotatably
 mounted to the frame by a plurality of second bearings.
 The apparatus further includes a power train arrangement for transmitting
 power from the engine to the idler shaft and from the idler shaft to the
 grinding shaft pulley wheel to rotationally drive the grinding wheel. In
 some exemplary embodiments, the idler shaft is mounted to the frame by two
 outer bearings that are coaxial with a pivot axis of the boom.
 Other objects of the invention are achieved by a mounting arrangement
 having a frame. A pivoting boom structure having a proximal end and a
 distal end is pivotally mounted to the frame by at least one first bearing
 at its proximal end. A first shaft is rotatably mounted to the frame and
 is coaxial with a pivot axis of the boom structure. The first shaft is
 mounted to the frame by a plurality of second bearings. A tool is
 rotatably mounted about a drive shaft at the distal end of the boom
 structure. A power train arrangement transmits power from the first shaft
 to the tool, with the boom structure being pivotally mounted to the frame
 independently of the first shaft.
 In some exemplary embodiments, a boom tube is fixed to the proximal end of
 the boom structure and is pivotally mounted to the frame by at least one
 first bearing so that it surrounds the first shaft. In another preferred
 embodiment, the at least one first bearing includes two bearings.
 The accompanying drawings, which are incorporated in and constitute a part
 of the specification, illustrate one or more embodiments of the invention
 and, together with the description, serve to explain the principles of the
 invention.

Repeat use of reference characters in the present specification and
 drawings is intended to represent same or analogous features or elements
 of the invention.
 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
 It is to be understood by one of ordinary skill in the art that the
 discussion herein is a description of exemplary embodiments only, and is
 not intended as limiting the broader aspects of the present invention,
 which broader aspects are embodied in the exemplary constructions.
 FIG. 1 illustrates an improved stump grinder machine 10 constructed in
 accordance with the present invention. As shown, machine 10 includes a
 frame structure 12 supported by a plurality of wheels 14 to facilitate
 movement of the machine from place to place. An engine 16 is mounted on a
 turntable assembly 18 for rotational movement through a predetermined
 horizontal arc.
 Typically, machine 10 will include a hydraulic system to power the various
 fluid-actuated cylinders and the like. A hydraulic pump 20 connected to an
 output shaft 21 (FIG. 2) of engine 16 supplies power to the hydraulic
 system.
 In the illustrated embodiment, machine 10 is a self-propelled device driven
 by a hydraulic motor 22 operatively connected to hydraulic pump 20. It
 should be distinctly understood, however, that the present invention
 includes towed stump grinding machines as well as stump grinding machines
 powered by other suitable methods.
 A grinding wheel 24 located at the distal end of a boom 26 performs the
 stump grinding operation. As shown, grinding wheel 24 has a plurality of
 radial teeth, such as teeth 28, that grind the stump as the rotating
 grinding wheel moves across it.
 Referring also to FIG. 2, grinding wheel 24 is rotatably driven by
 successive belt stages 30 and 32 configured between output shaft 21 and a
 drive shaft 29 of the grinding wheel. In the illustrated embodiment, belt
 stage 30 comprises a multiple v-belt stage extending from a pulley 33 on
 the engine's output shaft 21 to a pulley 34 mounted at one end of an idler
 shaft 36.
 As shown in FIG. 2, belt stage 32, which may include a poly-chain, is then
 driven from another pulley 38 located on the opposite end of idler shaft
 36. A grinding wheel pulley 41 is attached to the end of the grinding
 wheel's drive shaft 29. As shown in FIGS. 2 and 3, belt stages 30 and 32
 may be located inside of respective belt guards 42 and 44.
 As can be seen in FIG. 4, a boom tube 40 is pivotally mounted to turntable
 assembly 18 at flange supports 13 and 15. Frame structure 12 may comprise
 a generally flat bearing support (not shown) on which turntable assembly
 18 is mounted.
 A hydraulic cylinder 52, having one end pivotally connected to turntable
 assembly 18 and the opposite end connected to an upstanding connection
 member 53, may be utilized to pivot boom 26 in a generally vertical plane
 as shown in FIG. 2.
 Additionally, a hydraulic cylinder 56 may be utilized to expand the size of
 frame 12 for greater stability during the cutting operation. As shown in
 FIG. 4, portions of frame structure 12 may be telescopically configured to
 permit such expansion. Steering of this self-propelled machine is also
 preferably accomplished hydraulically, such as by a steering cylinder 58.
 Power generated from engine 16 may also be used to sweep grinding wheel 24
 in a horizontal plane as shown in FIG. 3. Specifically, rotation of
 turntable assembly 18 causes the grinding wheel to sweep in a horizontal
 plane.
 As is typical, the hydraulic system or other method of controlling the
 location of grinding wheel 24 may have multiple control levers, as
 indicated at 68 in FIGS. 2 and 3. Thus, an operator can use the controls
 at 68 to rotate turntable assembly 18 with respect to frame 12, thereby
 pivoting grinding wheel 24 in a horizontal plane. Additionally, the
 operator can actuate hydraulic cylinder 52 to pivot boom 26 in a generally
 vertical plane enabling grinding wheel 24 to gradually grind a stump below
 the surface of the ground.
 Before discussing various aspects of the present invention in further
 detail, it is helpful to review certain prior art. In this regard, FIG. 5
 illustrates a boom-to-frame mounting arrangement in accordance with the
 prior art. As shown, the prior art machine includes a frame 108. An idler
 shaft 110 is connected to engine driven first belt 112 and a grinding
 wheel second belt 114, each of which is housed respectively within belt
 guards 116 and 118. Idler shaft 110 is mounted to frame 108 by pillow
 block bearings 120 and 122 mounted to upstanding supports 130. A boom 124
 is pivotally mounted to the idler shaft by pillow block bearings 126 and
 128.
 As known to those of ordinary skill in the art, a typical bearing
 arrangement includes a housing, an inner race, an outer race, and a
 plurality of rolling elements disposed between the inner and outer races.
 Thus, in the prior art stump grinder boom mounting arrangement illustrated
 in FIG. 5, the inner race of all four bearings 120, 122, 126, and 128 is
 configured to rotate with idler shaft 110.
 Now that certain prior art has been discussed in greater detail, reference
 is made to FIG. 6 for further discussion of the present invention. As
 illustrated, boom 26 is mounted about idler shaft 36 in a manner that
 permits the idler shaft to freely rotate with respect to the boom and
 frame structure 12. A boom tube 40 is coaxial with a pivot axis of boom
 26, which corresponds with a rotational axis of idler shaft 36. As
 mentioned above, boom tube 40 is pivotally mounted to the frame structure
 on turntable 18 at flange supports 13 and 15 by respective inner bearings
 46 and 48, which in one preferred embodiment include bearings of
 approximately three inches in size. Boom tube 40 is fixed to boom 26 such
 as by welding.
 Referring now also to FIG. 7, inner bearing 46 includes a housing 60, an
 inner race 62, an outer race 64, and a plurality of rolling elements 66
 disposed between the inner and outer races. Inner bearing 48 is similarly
 configured. As illustrated, inner bearing spacers 50 and 51 may be
 provided between inner bearings 46 and 48 and respective flange supports
 13 and 15. It should also be understood that even though the illustrated
 embodiments show a nut and bolt fastening the bearings to their respective
 flange supports, any suitable fastening mechanism could be employed for
 this purpose.
 Idler shaft 36 is rotatably supported by a plurality of outer bearings, for
 example outer bearings 47 and 49, respectively, mounted to frame structure
 12 at flange supports 13 and 15. In one preferred embodiment, outer
 bearings 47 and 49 are approximately 13/4 inches in size. As should be
 understood, the size of the inner and outer bearings will vary according
 to the diameter of the respective boom tube or shaft to which they are
 attached.
 Referring specifically to FIG. 7, outer bearing 47 includes a housing 70,
 an inner race 72, an outer race 74, and a plurality of rolling elements 76
 disposed between the inner and outer races. Outer bearing 49, illustrated
 in FIG. 6, is similarly configured. As shown, outer bearings 47 and 49 are
 separated from respective flange supports 13 and 15 by a pair of outer
 bearing spacers 78 and 80.
 As shown in FIG. 7, a set collar 82 mounted about idler shaft 36 connects
 inner race 72 to idler shaft 36. A second set collar 84 mounted about boom
 tube 40 connects inner race 62 to the boom tube. Referring also to FIG. 6,
 set collars 86 and 88 are similarly configured to mount the inner races of
 bearings 49 and 48 respectively to idler shaft 36 and boom tube 40.
 Since the inner races of the inner bearings rotate independently of the
 inner races of the outer bearings, the novel construction of the present
 invention isolates rotation of idler shaft 36 from the pivoting action of
 boom 26. Additionally, idler shaft 36 does not support the weight of boom
 26 and cutting wheel 24.
 It can thus be seen that the present invention provides a novel stump
 grinding apparatus in furtherance of the noted objects. While preferred
 embodiments of the invention have been shown and described, modifications
 and variations thereto may be practiced by those of ordinary skill in the
 art without departing from the spirit and scope of the present invention,
 which is more particularly set forth in the appended claims. In addition,
 it should be understood that aspects of the various embodiments may be
 interchanged both in whole or in part. Furthermore those of ordinary skill
 in the art will appreciate that the foregoing description is by way of
 example only, and is not intended as a limitation of the invention so
 further described in such appended claims.