Note: Descriptions are shown in the official language in which they were submitted.
CA 02488123 2004-11-22
CHASSIS SUPPORTED TRACK ASSEMBLY
BACKGROUND OF THE INVENTION
The present invention relates to a track assembly and, in particular, to an
improved
endless track assembly that rotationally couples to a vehicle drive power
source and
pivotally couples to a chassis support and whereby the chassis support
accommodates
heavy weight vehicles and ambulatory equipment.
Track systems have been developed for use over soft and unprepared natural
terrain
by a variety of vehicles and equipment in different recreational, commercial,
farm and
military applications. Such vehicles and equipment can include wheels and/or
endless
track assemblies to achieve traction over off road surfaces with relatively
low surface
pressure at the contact surfaces of the drive train. For example, large
capacity people
haulers, trailers, manure spreaders, irngation systems, and military vehicles
include tracks.
Many devices use tracks that extend a substantial length of the equipment and
are
supported by a single drive roller and/or numerous idler rollers. The
vehicle/equipment
weight is generally concentrated at the several axle-bearing surfaces that
extend from the
vehicle/equipment. That is, the vehicle weight is supported at the relatively
small surface
area of several drive train axles, while the loading relative to the ground is
determined at
the larger surface area of the track to ground interface.
The difficulty with such axle support assemblies is that the chassis/equipment
weight is supported by one or more bearing supports having relatively small
surface areas.
The weight of many types of vehicles and equipment however can exceed the
loading
tolerances of the bearing surfaces, unless more expensive bearing supports are
used.
Alternatively, a large number of less costly bearing supports can be designed
into any piece
of equipment.
CA 02488123 2004-11-22
Desirably a mounting is required whereby a bearing support with a large
surface
area is mounted intermediate the chassis of the vehicle/equipment to off load
the primary
weight from the bearings of the drive/idler axles. The present improved track
assembly
was developed to accommodate the foregoing need and provide a track assembly
wherein
the vehicle weight is supported at a chassis to track assembly bearing
surface.
The improved track assembly provides a framework having a number of idler
rollers that extend from and are displaced along a track frame to support an
endless track.
A separate drive sprocket/drum mounts to a rotational drive power source at
the
vehicle/equipment and controls track movement. The weight of the vehicle is
supported by
a flange that extends from the chassis and cooperates with a complementary
surface of the
track framework. An intermediate bearing liner mounts between the flange and
track
framework. The bearing support surface of the track framework allows the track
frame to
pivot relative to the chassis independent of the drive sprocket/drum and/or
idler wheels.
SUMMARY OF THE INVENTION
It is a primary object of the invention to provide a large bearing support
surface
area for an endless track framework assembly independent of support surfaces
provided at
drive and/or idler axles.
It is further object of the invention to provide an endless track framework
having a
drive power sprocket/drum and several idler wheels that extend and rotate at
the
framework independent of a framework bearing support that mounts between the
vehicle/equipment chassis and the track framework.
It is a further object of the invention to provide a track framework having a
circular
bearing support surface that interlocks with a circular chassis support
surface and an
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CA 02488123 2004-11-22
intermediate bearing liner, such as constructed from a slippery, high-density
material,
roller, ball or other bearings.
It is a further object of the invention to provide a resilient, torsional bias
between
the mating bearing surfaces to resist motion in one or both directions of a
reciprocating
relative movement between the bearing supports.
It is a further object of the invention to provide mating bearing surfaces
between
the vehicle/equipment chassis and a track framework with a resilient, torsion
bias and
which bearing surfaces are concentrically aligned to a drive power axle to the
track
assembly.
The foregoing objects, advantages and distinctions of the invention are
obtained in
the presently preferred track assembly of the invention. The assembly provides
a metal
support framework having a circular bearing support surface. Several vertical
risers and
cross supports of the track framework brace the bearing support surface.
Several sets of
large and/or small diameter idler wheels are arrayed about the framework and
mate with an
endless drive track. A replaceable drive sprocket/drum is coupled to a rotary
power source
at the chassis/equipment and couples to rotate the drive track.
A bearing support flange extends from the vehicle/equipment chassis and aligns
with the framework bearing support surface. A slippery, high density bearing
material
interfaces between the bearing support surfaces. The track framework is
thereby supported
to rotate relative to vehicle/equipment chassis independent of the rotary
drive power source
to the track assembly.
Resilient members are fitted to the bearing supports to provide a torsional
control
over reciprocating movement of the track assembly. Springs,
expansiblelcompressible
CA 02488123 2004-11-22
material, hydraulic/pneumatic cylinders, among other resilient mechanisms can
be used to
provide the desired torsion control. Stop limits are provided to limit the
range of motion of
the track assembly and/or relative movement of the bearing support surfaces.
Still other objects, advantages, distinctions and constructions of the
invention will
become more apparent from the following description with respect to the
appended
drawings. Similar components and assemblies are referred to in the various
drawings with
similar alphanumeric reference characters. The description should not be
literally
construed in limitation of the invention. Rather, the invention should be
interpreted within
the broad scope of the further appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an assembled perspective drawing of a track assembly wherein the
framework includes a chassis bearing support and wherein the track is shown in
partial
section.
Figure 2 is a perspective drawing of a track assembly wherein the framework
and
chassis bearing supports are shown in exploded assembly relative to the drive
sprocket/drum and equipment power take-off.
Figure 3 is a perspective drawing of a track assembly wherein the framework
and
chassis bearing supports are shown in exploded assembly relative to the drive
sprocket/drum and equipment power take-off head, which includes a variable
drive ratio
gear assembly.
Figure 4 is a perspective drawing of a track assembly wherein the framework
and
chassis bearing supports are shown in exploded assembly relative to the drive
sprocket/drum and an alternative equipment power take-off.
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Figure 5 is a diagrammatic representation showing resilient biasing members
supported in a neutral condition between end stops at the chassis and track
framework
bearing supports.
Figure 6 is a diagrammatic representation showing the track assembly rotated
against one of the stops with one torsion member compressed and the other
extended to
bias the support back to the neutral condition.
Similar structure throughout the drawings is referred to with the same
alphanumeric
reference numerals and/or characters.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Refernng to Figures 1-4, several assembled and exploded assembly views are
shown to improved track assemblies 2, 4 and 6 of the invention. The track
assemblies 2, 4
and 6 find particular use with relatively heavy weight vehicles and equipment,
such as
large trucks, irrigation systems and the like. Each of the track assemblies 2,
4 and 6
includes a load bearing support assembly 10, 12 or 13 that displaces the
weight of the
1 S associated vehiclelequipment over a large bearing surface area. The weight
of the
vehiclelequipment is thereby shifted off the drive power coupling and track
drive sprocket
14 onto the chassis support assembly 10, 12 or 13. The load bearing support
assemblies
10, 12 or 13 are concentrically arranged to the axis of the drive power
linkage to allow the
track assemblies 2, 4 and 6 to rotate and accommodate changes in the terrain.
Each of the track assemblies 2, 4 and 6 includes a reinforced, endless track
16,
shown only at Figure 1 but understood to be included with each of the
assemblies 2, 4 and
6. The track 16 is typically constructed of rubber with suitable belting and
reinforcing
fibers to withstand typically encountered terrain, including rocks, logs, mud,
sand etc. The
CA 02488123 2004-11-22
interior surface of the track 16 provides several laterally displaced rows of
lugs 18 that
engage lateral teeth 20 of the sprocket 14. The ground-engaging surface 22 of
the track 16
includes other lugs 24 that are shaped and arrayed to enhance traction and
travel over an
anticipated terrain.
The lateral edges of the track 16 are typically constructed to cup or flex
slightly
inward at the extreme peripheral edges, upon setting a preferred tension. The
cupping in
the space adjacent exposed sides of adjoining idler wheels 28-32 facilitates
retention of the
track 16 to the idler wheel suspension.
The track 16 is suspended around the drive sprocket 14 and a framework 26. Two
large diameter, forward and aft idler wheels 28 and 30 and several smaller
diameter interior
idler wheels 32 support the track 16. The idler wheels 28-32 are supported
from axles (not
shown) that extend from and to the lateral sides of the track framework 26.
The idler
wheel axles project from the framework 26 as stationary stub axles. In a
through-frame
configuration, they can support a pair of the idler wheels 28, 30.
1 S A track tensioner assembly of conventional screw-follower construction
(not
shown) can be provided to cooperate with the fore and/or aft idler wheels 28
and 30.
Typically such assemblies incorporate a threaded member that cooperates with a
track
engaging piece to cause the track 16 to expand and contract in relation to the
adjustment of
the threaded member.
Alternatively, an eccentric coupling can be provided at the sprocket 14 or at
the
axles to the idler wheels 28 and 30. If such a coupling is provided between
the framework
26 and the drive linkage to the vehicle/equipment, the sprocket 14 is mounted
to rotate in a
cam fashion relative to the track 16 to establish the tension. That is, a
bearing housing
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having and eccentric outer surface is fitted over a drive axle to the sprocket
14 and is
aligned to the rotational axis of the sprocket 14. A similar mounting of an
eccentric
housing in the bores of the sets of idler wheels 28, 30 relative to a through
axle at either or
both of the fore and aft idler wheels 28, 30 can cause the sets of idlers
wheels 28, 30 to
expand and contract relative to the track 16. Rotation of the housing within
the bore of the
sprocket 14 or idler wheels 28,30 causes the sprocket 14 or idler wheels 28,30
to rotate
toward and away from the track 16. In all of the present track assemblies 2, 4
and 6, the
track tension is maintained independent of the mounting of the track
assemblies 2, 4 and 6
to the vehicle/equipment.
The idler wheels 28-32, which are shown in generalized forms, can be
constructed
to any desired size from any suitable material to support the intended
application and
loading at the track 16. The wheels 28-32 should also be constructed to
alleviate any
abrasion with the interior surface of the track 16. The configuration of the
hub, spokes etc.
of each idler wheel 28-32 can also be varied to the application. The wheels 28-
32 are also
constructed to be relatively intolerant to the adhesion of debris and to
promote the
discharge of debris from the wheels 28-32 and the track interior. The idler
wheels 28-32
are aligned at the framework 26 to run in longitudinal channels between the
lugs 18 at the
interior surface of the track 16.
The forward and/or aft idler wheels 28 and 30 can also be secured to the
framework
26 to permit an independent, resiliently biased rotation of the wheels 28, 30
relative to the
framework 26. An example of such a biasing assembly is disclosed at
applicant's co-
pending application serial no. 10/348,156. In such a track assembly, the idler
wheels 28
and 30 are mounted to rotate and pivot about the framework 26 subject to a
continuous,
resilient bias, such as established by a resilient member (e.g. spring,
compressible
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CA 02488123 2004-11-22
elastomer or expansible member etc.) secured between the wheels 28 and/or 30
and/or
intermediate linkage to the wheels and the framework 26. The
deformation/expansion/contraction of the resilient member might also be made
adjustable
to permit the setting of a preferred bias.
The drive wheel, drum or sprocket 14 is presently constructed of cast
aluminum,
although can be constructed of other materials to accommodate the loading.
Lateral teeth
20 extend between inner and outer annular bands 34 and 36 to engage the
leading surfaces
of the lugs 18 at the drive track 16. A mufti-spoke hub 38 is secured to a
drive power
linkage to the vehicle/equipment that supplies drive power to the track
assemblies 2, 4 and
6. The outer peripheral edges of the drive sprocket 14 are also shaped to
prevent the
buildup of debris between the drive sprocket 14 and track 16.
The track assemblies 2, 4 and 6 can be secured to a variety of different drive
power
couplings or linkages. Figure 2 shows a motor housing 70, such as provided at
a pivoting
irngation assembly (not shown), and a sprocket 72 that mate with the hub 38
and drum 14.
Drive power is directly provided from a drive shaft of the motor 70. For a
self powered
vehicle, power is typically applied from an axle to a driven wheel.
Figure 3 shows an alternative drive coupling wherein drive power is supplied
from
a sprocket 76 that is secured to a drive shaft (not shown) that rotates within
a shaft housing
78 that extends from the equipment/vehicle. A flange 80 secured to the shaft
housing 78 is
configured to mount to a flange 82 of a chassis support plate 84. Separately
mounted to
the equipment/vehicle chassis at a mounting plate 86 is a geared transfer case
88. A drive
shaft 90 and sprocket 92 extend from the case 88 and separately attach to the
hub 38 to
vary the rotational drive speed at the shaft 90.
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CA 02488123 2004-11-22
Alternatively, it is to be appreciated that the flange 80 might be mounted to
the
plate 86. In this instance, the drive power might be supplied from a motor
(not shown) or
the adjacent vehicle/equipment directly through the transfer case 88 via the
single shaft 90.
In this instance the shaft housing 78 et al. would not be required.
Figure 4 shows yet another drive coupling wherein a vehicle/equipment steering
housing 94 supports a drive shaft (not shown) and sprocket 96 that mates to
the hub 38 and
drum 14. Flanges 98 extend from the housing 94 and couple to a
vehicle/equipment
chassis support plate 100. The flanges 98 particularly attach to offset
flanges 102 and 104
at the chassis support plate 100. More of the details to the novel
significance of the chassis
support plates 48, 84 and 100 are discussed below.
The framework 26 generally includes a longitudinal section 40 that supports
the
idler wheels 28-32. Riser sections 42 and 44 project from the section 40 and
mount to a
curved or arcuate bearing support plate 46. A stationary chassis plate 48
extends from the
vehicle/equipment and the plate 46 is arranged to interact with and rotate
relative to the
plate 48. The chassis plate 48 is typically mounted to the vehicle/equipment
at a flange 50.
Slots 52 are formed into the plate 48 and fasteners 54 extend between the
bearing plates 46
and 48. The weight of the vehicle/equipment is thereby transferred to the
bearing support
plates 46 and 48 and the track framework 26, which relieves loading at the
coupling to the
drive sprocket 14 or other axle surfaces.
Returning attention to Figure 2, the track framework 26 is free to rotate to
and fro
along the chassis support plate 48, limited by the fasteners 54 and slots 52,
independent of
the rotation of the drive coupling to the sprocket 14. A layer of bushing
material or a
bearing surface 56 is fitted between the plates 46 and 48 to facilitate
relative movement.
The bearing 56 can be constructed of a variety of commercially available,
slippery
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materials, for example high density nylon, oil lite brass or UHMW plastic.
Ball and/or
roller bearings might also be included at/between the plates 46 and 48 to
promote free
relative movement and whereby the track assemblies 2, 4 and 6 can rotate
relative to the
vehicle/equipment chassis with terrain changes.
Figures S and 6 separately depict in diagrammatic form two generalized
conditions
wherein the plates 46 and 48 are biased at opposite ends relative to one
another. A torsion
suspension is provided to oppose and control relative movement of the track
assemblies 2,
4 and 6 to the vehiclelequipment and in relation to a neutral center position.
Movement of
the plate 46 to either side of a central position is particularly opposed by
at least one
biasing member that resiliently operates to direct the member back to the
neutral position.
The depicted torsion control provides for the placement of two resilient bias
members 58 at or between opposing end flanges 60 and 62 at the moveable track
support
plate 46 and stationary chassis support plate 48. Figure 5 depicts a neutral
condition,
wherein the expansion/contraction of the members 58 are balanced. Figure 6
depicts a
limit condition wherein one member 58 is fully extended and the other is fully
compressed.
The extended member 58 seeks to pull the moveable plate 46 back to center and
the
compressed member 58 seeks to push the plate 46 to the center. The bias
members 58 can
comprise springs, hydraulic or pneumatic cylinders, elastomers or any other
material,
device or assembly that provides a resilient, push-pull operation relative to
the chassis and
track support plates. It is to be appreciated also that the positioning of the
bias members
can be varied relative to the chassis support plates 48, 84 and 100 relative
to the track
support plate 46.
While the invention has been described with respect to a number of preferred
constructions and considered improvements or alternatives thereto, still other
constructions
CA 02488123 2004-11-22
may be suggested to those skilled in the art. It is also to be appreciated
that selected ones
of the foregoing features can be used singularly or can be arranged in
different
combinations to provide a variety of other improved track assemblies. The
foregoing
description should therefore be construed to include all those embodiments
within the
spirit and scope of the following claims.
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