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BACKGROUND OF THE INVENTION
The present invention relates generally to leveling systems and more
particularly to automatic leveling systems for off-road equipment, such as
mobile vehicles for felling and handling timber. Off-road equipment for
use in forestry operations and other off-road construction or excavating
equipment generally comprises a tracked or wheeled carrier base having a
cab or swing-house assembly rotatably mounted thereto. A boom assembly,
including any necessary apparatus for felling and handling trees or for
other operations, is operably mounted to the cab assembly. The cab
assembly further includes an engine, hydraulic pump system and controls
for operating the equipment.
Such off-road vehicles are often required to operate on uneven terrain.
Accordingly, the carrier base of the vehicle may not be level when the
vehicle is positioned at the desired location for performing work.
Inclination of the base causes the center of gravity of the vehicle to
shift away from the point of maximum load stability. Thus, the vehicle
becomes unbalanced and may overturn unless adjustments are made to reduce
the deviation of the center of gravity from the point of maximum load
stability.
It will be appreciated by those skilled in the art that, in order to avoid
the safety concerns associated with operating the vehicle on uneven
terrain and the general discomfort to the operator, it is desirable that
the cab assembly be substantially horizontal during operation of the
vehicle. To this end, there have been several attempts to design leveling
mechanisms and systems for adjusting the orientation of the cab assembly
with respect to the base of the vehicle.
One such attempt was disclosed in U.S. Pat. No. 5,337,847, issued to Woods,
et al. on Aug. 16, 1994, which is incorporated by reference as if fully
set forth herein. The Woods, et al. invention is directed to a four-way
leveling mechanism for an off-road vehicle for maintaining a
superstructure of an off-road vehicle generally horizontal while the
vehicle is working on uneven terrain. The tilt mechanism incorporates a
spherical bearing mounted on a shaft perpendicular to the longitudinal
pivot axis of the tilt mechanism to eliminate end-play in the joint which
forms the longitudinal pivot axis. The longitudinal and transverse pivot
axes lie in the same plane so that many of the forces which are
transferred from the superstructure of the vehicle through the tilt
mechanism to the chassis of the vehicle cannot cause a torque on the
components of the tilt mechanism. The tilt mechanism provides for
independent adjustment of the angle of tilt relative to each of the two
pivot axes.
U.S. Pat. No. 4,991,673, issued to Ericsson on Feb. 12, 1991, which is
incorporated by reference as if fully set forth herein, is directed to a
cross-country vehicle or machine. The vehicle includes a mobile chassis
and a superstructure carrying a driver's cab wherein the superstructure is
mounted on the chassis for tilting movement about a horizontal axis and a
transverse axis. A hydraulic cylinder on each side of the longitudinal
axis acts between the chassis and the superstructure to tilt the
superstructure about either or both axes in order to position the
superstructure horizontally as the vehicle moves over rough ground.
U.S. Pat. No. 4,679,803, issued to Biller, et al. on Jul. 14, 1987, which
is incorporated by reference as if fully set forth herein, is directed to
an apparatus for maintain stability of mobile land vehicles on sloping
terrain. The vehicle includes apparatus for providing multi-directional
relative movement between a conventional tread assembly of the caterpillar
type and a swing-house assembly which includes a boom sub-assembly
supporting tree-felling and handling equipment, so that the swing house
assembly is maintained in a substantially level relationship with the
horizontal, regardless of the inclination of the ground on which the
vehicle rides, so that the center of gravity of the vehicle is optimized
by weight transfer corresponding to the type of ground inclination
encountered. The leveling system of Biller, et al. is manually operated.
U.S. Pat. No. 4,650,017, issued to Pelletier, et al. on Mar. 17, 1987,
which is incorporated by reference as if fully set forth herein, is
directed to a crawler-mounted machine for travel over natural terrain. The
vehicle includes a mobile carrier of any conventional structure and a work
base mounted over the carrier. A tilt mechanism joins the work base to the
carrier for relative tilting movement of the work base with respect to the
carrier about a pair of orthogonal axes to hold the work base level.
U.S. Pat. No. 3,835,949, issued to Whelan on Sep. 17, 1974, and
incorporated by reference as if fully set forth herein, is directed to a
hydraulic leveling-control system. The system automatically maintains a
height of a vehicle for all load conditions up to maximum load. The system
basically involves a control valve which responds to height signals from
hydraulically-operated levelers to direct fluid to the levelers when
leveler chain charge pressure is needed to increase vehicle height, or to
a circuit bypassing the levelers when the vehicle is at or above level
height.
U.S. Pat. No. 5,159,989, issued to Claxton on Nov. 3, 1992, and
incorporated by references fully set forth herein, is directed to an
automatic hydraulic leveling system. The leveling system includes a
low-pressure, high-flow source of hydraulic fluid which is connected for
one-way flow into the head end of all four of the cylinders to lower
outrigger pads of the vehicle to the ground and then maintain them in
contact with the ground. A level sensor senses the relative levelness of
the right-front and left-rear corners of the vehicle and high-pressure,
low-flow hydraulic fluid is connected to the head end of the cylinder at
the lower of those two corners to raise that corner of the vehicle
relative to the ground. Likewise, another level sensor senses the relative
levelness of the left-front and right-rear vehicle corners and the
high-pressure, low-flow hydraulic fluid is connected to the head end of
the cylinder at the lower end of those two corners to raise that corner of
the vehicle relative to the ground.
U.S. Pat. No. 4,746,133, issued to Hanser, et al. on May 24, 1988, and
incorporated by reference as if fully set forth herein, is directed to an
automatic leveling system for use in a vehicle having a front, a back, and
sides to level the vehicle relative to gravity. The system includes a
plurality of devices, each disposed at an individual position relative to
the vehicle and in a displaced relationship to the other devices for
adjusting the vertical position of the vehicle relative to gravity in
accordance with the operation of pairs of adjacent devices. A sensor is
disposed relative to the vehicle for sensing the tilting of the vehicle
from the level disposition relative to gravity. A system further includes
an operating structure responsive to the sensor for operating pairs of
adjacent devices in a particular order to obtain an adjustment in the
vertical position of the vehicle from side to side and front to back to
obtain a resultant leveling of the vehicle relative to gravity.
U.S. Pat. No. 4,288,196, issued to Sutton, II on Sep. 8, 1981, and
incorporated by reference as if fully set forth herein, is directed to a
computer-controlled backhoe have dual-access gyro which continuously
senses the position of the frame and senses corresponding signals to the
computer which adjusts the frame position through hydraulic actuators.
One drawback associated with many of these devices is that they include
complex control circuitry and are, thus, expensive to incorporate into
off-road equipment. Furthermore, rather than adjusting automatically to
changes in the orientation of the vehicle, many of these devices require
manual adjustment by an equipment operator in order to achieve proper
leveling. What is needed, then, is an automatic leveling system for
off-road equipment that incorporates a simplified sensing and control
system to automatically level the cab assembly of the vehicle in response
to changes in orientation. This device is presently lacking in the prior
art.
SUMMARY OF THE INVENTION
The present invention is directed to an automatic leveling system for
off-road vehicles, such as timber felling and handling equipment and other
construction or excavating equipment having a cab and boom assembly
rotatably mounted on a carrier base. The system includes a sensing device
and control circuit for adjusting the level of the cab assembly relative
to the base of the vehicle.
The sensing device comprises a gimbaled pendulum having a pilot bolt
extending upwardly therefrom and positioned proximate four microswitches
for sensing changes in the orientation of the cab assembly. The
microswitches are positioned ninety degrees relative to one another and
are electrically connected to control circuits for a hydraulic pump and
valve system. If the cab assembly tilts due to movement of the machine
over uneven terrain, the pilot bolt contacts and activates a corresponding
switch. A signal from the switch to the hydraulic pump system causes the
corresponding hydraulic cylinder to adjust accordingly to level the
turntable on which the cab assembly is mounted. A delay circuit is
provided to inhibit re-leveling during extension of the boom.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the leveling device of the present
invention;
FIG. 2 is an exploded perspective view of the leveling device of the
present invention;
FIG. 3 is a side view of the leveling device of the present invention shown
installed on an off-road timber felling and handling vehicle;
FIG. 4 is a cross sectional view of the leveling device of the present
invention;
FIG. 5 is a top view of the leveling device of the present invention shown
with the cover, the switches and the switch bracket base removed;
FIG. 6 is a top view of the switch bracket assembly of the present
invention; and
FIG. 7 is a wiring diagram for the control circuit of the leveling device
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to FIG. 1, the sensing device of the leveling system of the
present invention is designated generally by reference numeral 10. The
sensing device 10 comprises a housing 12, configured to receive a pendulum
assembly, a gimbal assembly, and a switch-bracket assembly. In the
preferred embodiment, the housing 12 comprises a cylindrical canister
having a removable cover 14. A mounting bracket 16 is attached to an
exterior surface of the housing 12 for mounting the sensing device 10 to
an off-road vehicle 18 having a cab 20 and a boom assembly 22 mounted on a
carrier base 24 via a tilt table 26.
With reference to FIGS. 2 and 4, the pendulum assembly comprises a pendulum
disc 28, a pendulum body 30, and a pendulum bolt 32. In the preferred
embodiment, the pendulum disc 28 comprises a substantially cylindrical
body having a longitudinal bore 34 extending therethrough for receiving
the pendulum bolt 32 to attach the pendulum disc 28 to the pendulum body
30. The pendulum disc 28 may further include a recess 35 formed in a
bottom surface 37 thereof such that a head 40 of the pendulum bolt 32 is
substantially flush with the bottom surface 38 of the pendulum disc 28. In
the preferred embodiment, the pendulum disc 28 is of a greater diameter
than the pendulum body 30 in order to limit the range of motion of the
pendulum body 30 within the housing 12.
With reference to FIG. 4, pendulum body 30 comprises a substantially
cylindrical body having a central longitudinal bore 36 formed in a distal
end 38 thereof, which is threaded to receive the pendulum bolt 32. In a
similar manner, a central longitudinal bore 40 is formed in a proximate
end 44 of the pendulum body 30 and is threaded to receive a cooperatively
threaded pilot shaft 42. An axial bore 46 extends through the pendulum
body 30 intermediate the proximate end 44 and a midpoint of the pendulum
body 30.
Other pendulum assemblies are contemplated to be within the scope of the
present invention. For example, the components of the pendulum assembly
may be integrally formed such that the pendulum assembly comprises a
single component.
With reference to FIGS. 2, 4 and 5, the gimbal assembly of the present
invention comprises a ring 50 and a pendulum support shaft 52. The
pendulum support shaft 52 extends through axial bore 46 in the pendulum
body 30 and has spaced apart ends, which are received within a first pair
of oppositely disposed bores 54 and 56 formed in the ring 50. Each end of
the pendulum support shaft 52 is retained in operable engagement with the
ring 50 by a pin 57 (see FIG. 5). The ring 50 is pivotally suspended
within the housing 12 by a pair of ring retainer bolts 58 and 60, which
threadably engage nuts 59 and 61, and extend through a pair of bores 62
and 64 formed in the housing 12 and through a second pair of oppositely
disposed bores 66 and 68 formed in the ring 50. Bores 66 and 68 formed in
the ring 50 are aligned along an axis X normal to an axis Y along which
bores 54 and 56 are positioned. Thus, each of bores 54, 56, 66 and 68 is
located at a position that is ninety degrees relative to the adjacent
bore. Accordingly, the ring 50 is pivotal about axis X, and the pendulum
assembly is pivotal about axis Y.
With reference to FIGS. 4 and 5, a pendulum bushing 70, configured to
receive the pendulum support shaft 52, may be disposed within axial bore
46 of the pendulum body 30. The pendulum body 30 is disposed between a
pair of retainer rings 72 and 74 slidably mounted to the pendulum support
shaft 52. In the preferred embodiment, a threaded set screw 76 extends
through a bore 78 formed in the retainer rings 72 and 74 and frictionally
engages the pendulum support shaft 52 to retain the pendulum body 30 in a
desired position along the pendulum support shaft 52.
With reference to FIGS. 2 and 6, the switch bracket assembly comprises a
switch bracket 78 supported by a switch bracket base 80. The switch
bracket base 80 may be secured to the sensor housing 12 by screws any
other suitable means of fastening, such as bolts, pins, tack welds, etc.
In the preferred embodiment, four switches 82, 84, 86 and 88 are mounted
to the switch bracket assembly. Switch contacts 90, 92, 94 and 96 are
positioned proximate pilot shaft 42, which extends through a central bore
98 in the switch bracket base 80. Accordingly, when the pendulum assembly
moves in response to a change in orientation of the tilt table 26, the
pilot shaft 42 engages at least one of the switch contacts 90, 92, 94 and
96.
With reference to FIGS. 2 and 4, a cover 14 for the housing 12 is provided
to protect switches 82, 84, 86 and 88. The cover 14 preferably includes a
lip 99 around the periphery which engages the housing 12 in an overlapping
relationship when installed thereon. The cover 14 is secured to the
housing 12 by screws or any other suitable means of attachment, such as
bolts or pins, which will enable removal of the cover 14. The electrical
wiring associated with switches 82, 84, 86 and 88 passes through a conduit
100 in the cover 14 to solenoids associated with a hydraulic system (not
shown).
With reference to FIG. 7, the control circuit for the sensing device 10
includes a manual/automatic control switch 102, a fusible link 104 to a
power supply, and switches 82, 84, 86 and 88 for signaling a change in
orientation of the tilt table 26. Typically, extension of the boom
assembly 22 will result in a temporary change in orientation of the
vehicle 18. Accordingly, delay relays 106, 108, 110, and 112 are provided
to inhibit re-leveling of the tilt table 26 during extension of the boom
assembly 22.
Thus, although there have been described particular embodiments of the
present invention of a new and useful automatic leveling system for
off-road vehicles, it is not intended that such references be construed as
limitations upon the scope of this invention except as set forth in the
following claims. Further, although there have been described certain
dimensions used in the preferred embodiment, it is not intended that such
dimensions be construed as limitations upon the scope of this invention
except as set forth in the following claims.
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