U.S. patent application number 11/154187 was filed with the patent office on 2005-10-06 for lawnmower tilt sensor apparatus and method.
This patent application is currently assigned to Ariens Company. Invention is credited to Bucher, Corey W..
Application Number | 20050217230 11/154187 |
Document ID | / |
Family ID | 34595076 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050217230 |
Kind Code |
A1 |
Bucher, Corey W. |
October 6, 2005 |
Lawnmower tilt sensor apparatus and method
Abstract
A lawnmower comprising a frame, an engine supported by the
frame, a mower deck supported by the frame, a rotating cutting
blade disposed below the mower deck. A PTO is coupled to the engine
and the cutting blade to rotationally drive the cutting blade. A
drive system is connected to the frame and coupled to the engine to
drive or propel the lawnmower. The lawnmower includes a tilt sensor
for sensing a tilt angle representing the orientation of the
lawnmower with respect to a horizontal level plane. A signal
indicator may provide a notice signal when the tilt angle exceeds a
pre-determined check angle. A CPU is electrically coupled between
the tilt sensor and signal indicator, and activates the signal
indicator in response to the tilt sensor sensing that the lawnmower
is tilted beyond the threshold angle to warn the lawnmower operator
of a tilt condition.
Inventors: |
Bucher, Corey W.;
(Wrightstown, WI) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH, LLP
100 E WISCONSIN AVENUE
MILWAUKEE
WI
53202
US
|
Assignee: |
Ariens Company
|
Family ID: |
34595076 |
Appl. No.: |
11/154187 |
Filed: |
June 16, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11154187 |
Jun 16, 2005 |
|
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10781454 |
Feb 18, 2004 |
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60524087 |
Nov 21, 2003 |
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Current U.S.
Class: |
56/10.2R |
Current CPC
Class: |
A01D 75/28 20130101 |
Class at
Publication: |
056/010.20R |
International
Class: |
A01D 075/28 |
Claims
1. A riding lawnmower comprising: a frame; an engine supported by
the frame; a mower deck supported by the frame; a rotating cutting
blade disposed below the mower deck and selectively rotating under
the influence of the engine to cut vegetation under the mower deck;
a drive system connected to the frame for driving the lawnmower; a
tilt sensor for sensing a tilt condition of the lawnmower with
respect to horizontal; a CPU electrically communicating with the
tilt sensor to monitor a tilt angle of the lawnmower and creating
an output signal in response to the tilt sensor indicating that the
lawnmower is tilted beyond a selected angle; and a signal indicator
electrically communicating with the CPU and providing a notice
signal to an operator of the lawnmower in response to receiving the
output signal from the CPU.
2. The lawnmower of claim 1, wherein the drive system includes
first and second drive wheels and first and second control levers
for the independent forward and reverse operation of the respective
first and second drive wheels.
3. The lawnmower of claim 1, wherein the tilt sensor creates a
check signal in response to the tilt angle of the lawnmower
exceeding a check angle, and a limit signal in response to the tilt
angle of the lawnmower exceeding a limit angle, the limit angle
being larger than the check angle; wherein the signal indicator
includes a check indicator and a limit indicator different from the
check indicator; and wherein the CPU creates a first output signal
to activate the check indicator in response to the CPU receiving
the check signal and creates a second output signal to activate the
limit indicator in response to the CPU receiving the limit
signal.
4. The lawnmower of claim 3, wherein the tilt sensor includes a
check switch set to close a first electrical circuit and create the
check signal in response to the tilt angle of the lawnmower
exceeding the check angle, and a limit switch set to close a second
electrical circuit and create the limit signal in response to the
tilt angle of the lawnmower exceeding the limit angle.
5. The lawnmower of claim 3, further comprising a clock
electrically coupled to the CPU, wherein the CPU only creates the
first output signal in response to receiving the check signal for
at least one continuous second as measured by the clock; and
wherein the CPU only creates the second output signal in response
receiving the limit signal for at least five continuous seconds as
measured by the clock.
6. The lawnmower of claim 1, wherein the CPU, substantially
simultaneously with activating the output signal, causes the
cutting blade to be disengaged from the engine while maintaining
the drive system in control of driving the lawnmower.
7. The lawnmower of claim 1, wherein the tilt sensor includes an
inclinometer for measuring the tilt angle of the lawnmower; and
wherein the CPU causes the signal indicator to display the tilt
angle of the lawnmower as measured by the inclinometer.
8. The lawnmower of claim 1, further comprising a clock
electrically coupled to the CPU, wherein the CPU creates the output
signal only in response to the tilt sensor sensing that the
lawnmower is tilted beyond the selected angle for at least one
second as measured by the clock.
9. The lawnmower of claim 8, further comprising a memory device
electrically coupled to the CPU, wherein the CPU records in the
memory device information received from the clock substantially
simultaneously with creation of the output signal.
10. The lawnmower of claim 1, wherein the signal indicator includes
a speaker for providing an audible signal.
11. The lawnmower of claim 1, wherein the signal indicator includes
a strobe light for providing a visual signal.
12. A riding lawnmower comprising: a frame; an engine supported by
the frame; a mower deck supported by the frame; a rotating cutting
blade disposed below the mower deck and selectively rotating under
the influence of the engine to cut vegetation under the mower deck;
means for driving the lawnmower; means for sensing a tilt angle
representing the orientation of the lawnmower with respect to a
reference plane; a CPU coupled to the means for sensing, the means
for sensing providing a check signal to the CPU when the tilt angle
exceeds a pre-determined check angle, the means for sensing
providing a limit signal to the CPU when the tilt angle exceeds the
limit angle, the limit angle being greater than the check angle;
and a signal indicator providing a notice signal being at least one
of an audible signal and a visual signal in response to the CPU
receiving the check signal.
13. The lawnmower of claim 12, wherein the means for sensing
includes an inclinometer; wherein the signal indicator includes a
display screen; and wherein the notice signal includes a visual
display on the display screen of the current tilt angle of the
lawnmower.
14. The lawnmower of claim 12, wherein the means for sensing
includes separate check and limit switches for providing respective
check and limit signals when the tilt angle of the lawnmower
exceeds preset check and limit angles; wherein the CPU creates
first and second output signals in response to receiving the
respective check and limit signals from the means for sensing; and
wherein the signal indicator generates different notice signals in
response to receiving the respective first and second output
signals from the CPU.
15. The lawnmower of claim 12, wherein the CPU, substantially
simultaneously with activating the signal indicator, causes the
cutting blade to be disengaged from the engine while maintaining
the means for driving in control of driving the lawnmower.
16. A method of providing a signal for the operating angle of a
lawnmower having a frame, an engine supported by the frame, a mower
deck supported by the frame, a rotating cutting blade disposed
below the mower deck and a PTO connecting the cutting blade and the
engine and rotationally driving the cutting blade, and means for
driving the lawnmower, the method comprising the acts of: measuring
with a tilt sensor a tilt angle representing the orientation of the
lawnmower with respect to a reference plane; sending a check signal
from the tilt sensor to a CPU when the tilt angle exceeds a
pre-determined check angle; sending a limit signal from the tilt
sensor to a CPU when the tilt angle exceeds a pre-determined limit
angle, the limit angle being greater than the check angle; and
activating a notice signal including at least one of an audible
signal and a visual signal when the CPU receives the check
signal.
17. The method of claim 16, further comprising the act of logging
at least the time of activation of the check and limit signals in a
storage device.
18. The method of claim 16, wherein the act of activating the
notice signal further comprises activating the notice signal when
the CPU continuously receives the check signal for at least about
one continuous second.
19. The method of claim 16, further comprising the act of
activating an additional notice signal when the CPU receives the
limit signal for at least about five continuous seconds.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/781,454 filed Feb. 18, 2004, the entire
contents of which are incorporated herein by reference, which
claims priority to U.S. Provisional Application No. 60/524,087,
filed on Nov. 21, 2003, the entire contents of which is also
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to a tilt sensor apparatus and
method, and more particularly to a tilt sensor apparatus and method
for a lawnmower.
BACKGROUND
[0003] Power implements commonly include devices such as utility
tractors, lawnmowers, landscaping equipment, trimmers, tillers,
snow throwers, or other similar implements, and are used for
general outdoor applications such as landscaping, gardening, lawn
care, or snow removal. The implement may include at least one
mechanism to perform the desired application. If the implement is
self-propelled, the implement also includes a drive mechanism to
propel the implement. For example, if the implement is a lawnmower,
the lawnmower may include a drive mechanism, such as an engine and
driven wheels, to propel the lawnmower across a surface, and a
cutting blade to cut vegetation.
SUMMARY
[0004] The present invention provides a riding lawnmower comprising
a frame, an engine supported by the frame, a mower deck supported
by the frame, a drive system connected to the frame for driving the
lawnmower, and a rotating cutting blade disposed below the mower
deck and selectively rotating under the influence of the engine to
cut vegetation under the mower deck. The lawnmower includes a tilt
sensor for sensing whether the lawnmower is tilted beyond a
threshold angle with respect to horizontal, and a signal indicator
for providing to an operator of the lawnmower a signal indicative
of the lawnmower being tilted beyond the threshold angle. The
lawnmower also includes a central processing unit ("CPU")
electrically coupled between the tilt sensor and signal indicator
and activating the signal indicator in response to the tilt sensor
sensing that the lawnmower is tilted beyond the threshold
angle.
[0005] In some aspects and in some constructions, the drive system
includes two independently controlled drive wheels.
[0006] In some aspects and in some constructions, The tilt sensor
includes a check switch that creates a check signal in response to
the tilt angle of the lawnmower exceeding a check angle, and a
limit switch that creates a limit signal in response to the tilt
angle of the lawnmower exceeding a limit angle. The limit angle may
be larger than the check angle. The signal indicator may include a
check indicator and a limit indicator different from the check
indicator. The CPU may activate the check indicator in response to
the check sensor sensing that the tilt angle of the lawnmower
exceeds the check angle, and may activate the limit indicator in
response to the limit sensor sensing that the tilt angle of the
lawnmower exceeds the limit angle. The check switch and limit
switch may both be tip switches that close in response to the tilt
angle of the lawnmower exceeding the respective check angle and
limit angle. Alternatively, or in addition to one or more tip
switches, the lawnmower may include an inclinometer that reports to
the CPU and/or the lawnmower operator the actual tilt angle of the
lawnmower at any time.
[0007] In some aspects and in some constructions, the lawnmower may
include a clock electrically coupled to the CPU. To filter out
bumps and temporary rocking of the lawnmower, the CPU may only
activate the check and limit indicators in response to the check
sensor sensing that the tilt angle of the lawnmower exceeds the
respective check and limit angles for certain extended periods of
time, such as one to five continuous seconds, as measured by the
clock.
[0008] In some aspects and in some constructions, the CPU may,
substantially simultaneously with activating the limit indicator,
causes the cutting blade to be disengaged from the engine while
maintaining the drive system in control of driving the
lawnmower.
[0009] Other features and advantages of the present invention will
become apparent to those skilled in the art upon review of the
following detailed description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a perspective view of a lawnmower having a tilt
sensor embodying aspects of the present invention;
[0011] FIG. 2 shows a cross-sectional view of a portion of the
lawnmower of FIG. 1;
[0012] FIG. 3 shows a front view of the lawnmower of FIG. 1;
[0013] FIG. 4 illustrates a system block diagram of a control unit
according to aspects of the present invention;
[0014] FIG. 5 illustrates an operational flow diagram of the system
in FIG. 4 according to aspects of the present invention.
DETAILED DESCRIPTION
[0015] FIG. 1 illustrates a lawnmower 10 including a frame 14,
front wheels 18 and rear wheels 22 supporting the frame 14, a mower
deck 26 supported by the frame 14, an engine 28 supported by the
frame 14, a cutting blade 30 disposed under the mower deck 26 and
driven by the engine 28. As shown in FIG. 1, the cutting blade 30
is normally obscured from view, but is illustrated through a
cut-away portion of the mower deck 26. The engine 28 may be
enclosed within a housing, as shown in FIG. 1. The lawnmower may
also include a seat 34 supported by the frame 14 on which an
operator may sit and a foot board 35 supported by the frame 14 for
supporting an operator's feet. In the illustrated construction, the
two rear wheels 22 may be coupled on a single axle and may both
rotate about the same rotational axis 36.
[0016] In FIG. 1, the lawnmower 10 is a self-propelled riding
lawnmower including a drive system connected to the frame 14 and
coupled to the engine 28 for driving the lawnmower 10. The drive
system includes two independently controlled drive wheels
rotationally driven by the engine 28. As shown in FIG. 1, drive
wheels of the drive system include the rear wheels 22 of the
lawnmower 10. The drive system may include a transmission to direct
the power from the engine to drive the drive wheels 22 in a forward
or reverse direction.
[0017] In the illustrated construction, the lawnmower 10 is a
belly-mount zero turn radius mower having a pair of control levers
38 for the independent forward and reverse operation of the drive
wheels. The lawnmower 10 may be considered a "transteer" lawnmower
and each control lever 38 independently controls the corresponding
drive wheel 22 on the respective side of the lawnmower 10. The
lawnmower 10 utilizes the independent drive wheels 22 to both
propel the lawnmower 10 and steer the lawnmower 10. For example, to
make a soft right turn, the lawnmower 10 may rotate the left wheel
in a forward direction relatively faster than the right wheel. To
make a hard right turn, the lawnmower 10 may rotate the left wheel
in a forward direction while stopping the right wheel. To make a
zero-radius right turn, the lawnmower 10 may rotate the left wheel
in a forward direction while rotating the right wheel in a reverse
direction. Therefore, in the lawnmower 10 the power transferred to
the drive system is also used to steer the lawnmower 10. The
invention is not limited to the illustrated lawnmower 10 and may
alternatively be embodied in other lawnmowers, such as a front
mount mower or even other similar power implements.
[0018] FIG. 2 illustrates a partial cross-sectional view of the
cutting blade 30 disposed below the mower deck 26. A shaft 44
extends through an opening in the mower deck 26, and the mower
blade 30 is connected to an end of the shaft 44. As shown in FIG.
2, a Power Take-Off (PTO) 48 is coupled to the end of the shaft 44
opposite the cutting blade 30. The PTO 48 may be mounted to the
mower deck 26. The PTO 48 is coupled to the engine and the rotating
cutting blade 30 and at least partially transfers rotational power
from the engine to the cutting blade 30 to rotationally drive the
cutting blade 30. The PTO 48 may be selectively engaged or
disengaged to control the transfer of power from the engine to the
cutting blade 30 and regulate rotation of the cutting blade 30. In
the illustrated construction, the PTO 48 includes an electric
clutch and brake. The PTO 48 may include a pulley 52 that may be
coupled to the engine with a belt 56 using a belt-and-pulley
system. Other similar systems may be used to transfer rotational
power from the engine to the PTO 48, such as a gearing system, a
chain-and-sprocket system, a direct shaft, or other similar
systems. The PTO 48 may regulate the rotational power transferred
from the input, or pulley 52, to the output, or shaft 44. The PTO
48 may be controlled electronically to engage or disengage the
electric clutch.
[0019] The lawnmower 10, as shown in FIG. 1, is generally driven on
an off-road surface to cut vegetation, such as grass. Due to the
off-road usage of the lawnmower 10, the lawnmower 10 may encounter
uneven terrain and may be operated on a hill or slope. FIG. 3
illustrates the lawnmower 10 positioned on a slope being tilted
from a horizontal plane. The position of the lawnmower 10 may
define a tilt angle representing the orientation of the lawnmower
10 with respect to a horizontal plane. The tilt angle is generally
zero when the lawnmower 10 is on a flat level horizontal surface.
While the lawnmower 10 is designed to be stable, operating the
lawnmower 10 on extremely steep slopes beyond the intended range of
use may present an unsafe operating condition. The lawnmower 10 may
include a control unit 60 that senses the tilt angle and helps
reduce the likelihood of an operator unknowingly encountering an
unsafe operating condition on a hill or slope. As shown in FIGS. 1
and 3, the control unit 60 may be connected to the lawnmower 10
near the seat 34.
[0020] FIG. 4 illustrates a circuit diagram representing the
control unit 60. The control unit 60 includes a CPU or processing
module 70 and a tilt sensor 74 coupled to the CPU 70. The tilt
sensor 74 senses a tilt angle representing the tilt of the
lawnmower 10 relative to a horizontal plane. For example, the tilt
sensor 74 is set to be about zero degrees when the lawnmower 10 is
on a horizontal level surface. When the lawnmower 10 is driven on a
hill or slope that is not horizontal, the tilt sensor 74 will sense
that the lawnmower is no longer horizontal and may determine the
tilt angle representing the orientation of the lawnmower 10 with
respect to a horizontal level plane. FIG. 3 illustrates an example
of the lawnmower 10 on a slope S with the tilt angle A representing
the orientation of the lawnmower 10 with respect to the horizontal
plane H.
[0021] In some aspects and in some constructions, the tilt sensors
74 may include tip switches and/or inclinometers to sense the tilt
angle and provide an input for the control unit 60. A tip switch is
generally an on or off switch and is activated and turned on when
the tilt angle reaches a maximum threshold angle or trigger angle.
A tip switch may sense whether the tilt angle is greater than or
less than a certain angle, depending if the switch is on or off,
but does not measure the exact tilt angle. An inclinometer
generally measures the tilt angle and provides a numerical value
representing the tilt angle. For example, a tip switch may sense
that the tilt angle is greater than 10 degrees, and an inclinometer
may indicate that the tilt angle is about 13 degrees.
[0022] As shown in FIG. 4, the tilt sensor 74 has two tip switches
including a check switch 80 and a limit switch 84. An example of a
suitable tip switch includes the TAD II--Threshold Angle Detector
made by Spectron Systems Technology Inc. of Hauppauge, N.Y. The tip
switches 80, 84 function as electronic switches that are activated
when the tilt of the switch with respect to a horizontal plane
reaches a trigger angle. The check and limit switches 80, 84 may be
substantially the same, but may be set with different
pre-determined threshold or trigger angles. The activation of the
tip switch may provide a signal to the CPU 70 that the switch has
reached its trigger angle or threshold angle. The tip switches are
generally mounted in a horizontal plane and may read the tilt angle
along all angle orientations. For example, the tip switches 80, 84
read both the pitch and the roll of the sensor and may determine
the overall tilt angle of the sensor based on the pitch and roll
values.
[0023] The tip switches 80, 84 may be set for a range of
pre-determined trigger angles or threshold angles. The TAD
II--Threshold Angle Detector, described above, provides a threshold
range of about 0.2 degrees to 40 degrees. In this disclosure, the
trigger angle for the check switch 80 is referenced as the check
angle, and the trigger angle for the limit switch 84 is referenced
as the limit angle. For example, the check switch 80 will be
activated and turned on when the tilt angle reaches the check
angle, and the limit switch 84 will be activated and turned on when
the tilt angle reaches the limit angle. In the illustrated
construction, the check switch 80 may be set with a check angle of
about 10 degrees, and the limit switch 84 may be set with a limit
angle of about 20 degrees. These values may be selected based on
various features of the lawnmower 10 that may influence stability.
For example, the wheel base, height, weight, center of gravity,
seat location, weight of the operator, and other similar features
may influence stability and may be considered when selecting the
trigger angles.
[0024] As shown in FIG. 4, the check switch 80 is on or closed,
indicating that the tilt angle exceeds the check angle. The check
switch 80 provides a check signal to the CPU 70 indicating that the
tilt angle exceeds the check angle, or the threshold angle for the
check switch 80. In FIG. 4, the limit switch 84 is off or open,
indicating that the tilt angle is below the limit angle. If the
tilt angle exceeds the limit angle, the limit switch 84 closes and
provide a limit signal to the CPU 70 indicating that the tilt angle
exceeds the limit angle. In some aspects and in some constructions,
the control unit 60 may include only a single tip switch.
[0025] FIG. 4 also illustrates an inclinometer 88, or tip angle
input device, for measuring the tilt angle and providing an input
to the CPU 70 indicating the tilt angle. In some aspects and in
some constructions, the tilt sensor 74 may include the inclinometer
88 instead of the tip switches 80, 84. The inclinometer 88 may also
be used together with the tip switches 80, 84. The inclinometer 88
measures the tilt angle representing the orientation of the
lawnmower 10 with respect to a horizontal level plane and provides
the tilt angle data to the CPU 70. The CPU 70 may analyze the tilt
angle and determine if the tilt angle exceeds the pre-determined
check angle and/or limit angle. An example of a suitable
inclinometer includes the Spectrotilt.TM. II Micro-50 Dual Axis
Digital Inclinometer made by Spectron Systems Technology Inc. of
Hauppauge, N.Y.
[0026] The control unit 60 also includes an output device for
alerting the operator. If the tilt angle exceeds the check angle
and the CPU 70 receives the check signal, the CPU 70 may
automatically activate an output device. The output device of the
control unit 60 may include a signal indicator or a signal module
providing a notice signal including at least one of an audible
signal and a visual signal. In the illustrated construction, the
signal indicator or signal module may include a speaker 96 for
providing an audible signal and/or a strobe light 100 for providing
a visual signal. The control unit 60 may use just the speaker 96,
just the strobe light 100, both the speaker 96 and the strobe light
100, multiple speakers 96, multiple strobe lights 100, or other
various combinations of the speaker 96 and the strobe light 100.
FIG. 4 also illustrates a LCD display screen 104 that may provide
messages for the operator. The screen may be used to provide the
notice signal. The control unit 60 may also include an input keypad
permitting user interface with the control unit 60.
[0027] As shown in FIG. 4, the control unit 60 also includes a
current driver 108 coupled to the CPU 70 and the PTO 48. The
current driver 108 may be activated by the CPU 70 to engage or
disengage the PTO 48. As described above, the PTO 48 controls
rotation of the cutting blade 30 (FIG. 2), and is electrically
controlled by the CPU 70. The control unit 60 also includes a PTO
input switch 112 that senses when the PTO 48 is engaged or
disengaged. The PTO input switch 112 is coupled to the CPU 70 and
provides an input to the CPU 70 to indicate whether the PTO 48 is
engaged or disengaged.
[0028] FIG. 4 also illustrates a clock 116 and a memory or storage
device 120 coupled to the CPU 70. The clock 116 may provide time
information to the CPU 70, such as date, time of day, and duration
of various events. The memory 120 saves data input from the CPU 70
and may record the occurrence of various events, such as the CPU 70
receiving signals, providing signals, the tilt angle, the
activation of the speaker 96 and/or strobe light 100, an input from
the PTO input switch 112, the disengagement or engagement of the
PTO 48, or other similar events. The memory 120 may also save the
information or data received from the clock 116 to indicate time
and date information for when a specific event occurred and the
duration of the event.
[0029] FIG. 5 illustrates an operational flow diagram 200 of the
control unit 60 and lawnmower 10 outlining one example of the
control unit 60 sensing the tilt angle of the lawnmower 10. The
control unit 60 begins monitoring the lawnmower 10 when the
ignition of the lawnmower 10 is turned on. If the tilt angle is
less than a pre-determined check angle and the tip switches 80, 84
are off or open, the PTO 48 may be energized and engaged to rotate
the cutting blade 30. At step 204, the PTO input switch 112 senses
if the PTO 48 is engaged or disengaged. If the PTO 48 is engaged,
the control unit 60 checks if the tilt angle exceeds the check or
limit angles. At step 208, the check switch 80 senses if the tilt
angle exceeds the check angle. In the illustrated construction, the
check angle is about 10 degrees. If the tilt angle does not exceed
the check angle, the check switch 80 remains open or off and the
control unit 60 continues to check the check switch 80. If the tilt
angle does exceed the check angle, the check switch 80 is closed or
off and the control unit 60 proceeds to step 212.
[0030] At step 212, the limit switch 84 senses if the tilt angle
exceeds the limit angle. In the illustrated construction, the limit
angle is about 20 degrees. If the tilt angle does not exceed the
limit angle, the limit switch 84 remains open while the check
switch 80 is closed and the control unit 60 proceeds to step 216.
In step 216, the control unit 60 checks if the check switch 80
remains continuously closed for a pre-determined period of time. In
the illustrated construction, the pre-determined period of time is
about 2 continuous seconds. If the check switch 80 remains closed
for about 2 continuous seconds, the control unit 60 proceeds to
step 220.
[0031] Checking for the check switch 80 being closed for a
continuous period of time provides a buffer and helps filter out
false signals due to rough terrain. For example, if the lawnmower
10 briefly hits a bump, hole, or is somehow jarred, the lawnmower
10 may be temporarily tilted and the tilt angle may exceed the
check angle due to the shock on the lawnmower 10. If the lawnmower
10 quickly returns to a level position the signal will not continue
for the required period of time, and the control unit 60 will not
proceed to the next step. The continuous signal check helps prevent
false alarms for the operator.
[0032] At step 220, the signal indicator or signal module provides
a notice signal for the operator. As described above, the notice
signal may comprise an audible signal from the speaker 96, a visual
signal from the strobe light 100, a message on the display screen
104, and/or some other similar signal to be perceived by the
operator. The notice signal may be an intermittent signal, such as
a beep or flash. If the tilt angle drops below the check angle and
the check switch 80 returns to the open or off position for a
pre-determined period of time, such as 2 continuous seconds, the
control unit 60 returns to step 204 and restarts the sensing
process. If the tilt angle remains above the check angle and the
check switch 80 remains on, the control unit 60 again performs step
212.
[0033] As mentioned above, at step 212, the limit switch 84 senses
if the tilt angle exceeds the limit angle. If the tilt angle does
not exceed the limit angle, the limit switch 84 is open and the
control unit returns to step 204. If the tilt angle exceeds the
limit angle, the limit switch 84 is closed and the control unit 60
proceeds to step 224. At step 224, the control unit 60 checks if
the limit switch 84 remains continuously closed for a
pre-determined period of time, such as 1 continuous second. The
control unit 60 will return to step 204 if the limit switch 84 does
not remain on or closed for 1 continuous second, and will proceed
to step 228 if the limit switch 84 does remain on or closed for 1
continuous second. Once again, checking for the limit switch 84
being closed for a continuous period of time provides a buffer and
helps filter out false signals due to rough terrain.
[0034] At step 228, the signal indicator or signal module may
provide an additional notice signal for the operator. The
additional notice signal may also comprise an audible signal from
the speaker 96, a visual signal from the strobe light 100, a
message on the display screen 104, or some other similar signal to
be perceived by the operator. The additional notice signal may be
more conspicuous than the first notice signal to inform the
operator that there has been a change in the tilt angle and allow
the operator to differentiate between the notice signals. The
additional notice signal may be a continuous signal, such as a
continuous noise or light, while the first notice signal may be an
intermittent signal, such as a flash or beep. The control unit 60
will then proceed to step 232 in which the control unit 60 checks
if the limit switch 84 remains continuously closed for an
additional pre-determined period of time, such as 5 continuous
seconds. Checking the limit switch 84 for a continuous period of
time provides the operator with an opportunity to steer the
lawnmower 10 to more level terrain and avoid a potentially unsafe
operating condition. If the control unit 60 senses that the limit
switch 84 if off or open, the control unit 60 returns to step 204.
If the control unit 60 senses that the limit switch 84 remains
closed for 5 continuous seconds, the control unit 60 proceeds to
step 236.
[0035] At step 236, the control unit 60 provides a signal to the
PTO 48 to disengage the PTO 48 and stop rotation of the cutting
blade 30. In some aspects and in some constructions, the control
unit 60 may not provide an additional indicator signal and may skip
step 228 and proceed directly to step 236 to disengage the PTO 48.
The control unit 60 may record that the PTO 48 was disengaged and
the corresponding date and/or time data in the memory 120 or
storage device.
[0036] When the PTO 48 is disengaged due to the tilt angle
exceeding the limit angle, power is cut to the cutting blades 30 to
stop rotation, but power is still provided to the drive system. The
drive system remains operable to drive the lawnmower 10 when the
PTO 48 is disengaged. Maintaining power to the drive system is
helpful when the lawnmower 10 is zero-radius turn mower having two
independently controlled drive wheels 22. As described above, the
drive system uses power to the drive wheels 22 to both propel the
lawnmower 10 and steer the lawnmower 10. Maintaining power to the
drive system permits the operator to steer the lawnmower 10 off the
hill or slope to a more level terrain and decrease the tilt angle.
Decreasing the tilt angle helps lessen the likelihood of an
operator unknowingly encountering an unsafe operating condition.
Therefore, the powered drive system helps the operator avoid a
severe hill or slope.
[0037] The various pre-determined periods of time in which the
control unit 60 checks for a continuous signal, such as 1, 2, or 5
seconds, may vary depending on features of the lawnmower 10. As
described above, the stability of the lawnmower 10 may be
influenced by various factors, such as the wheel base, height,
weight, center of gravity, seat location, weight of the operator,
and other similar features. The pre-determined period of time may
be selected based on these other features that influence
stability.
[0038] In some aspects and in some constructions, the control unit
60 may only include the limit switch 84 and may not have the check
switch 80. In this construction, the control unit 60 may bypass
steps 208, 216, and 220 and may proceed directly to step 212 to
check if the limit switch 84 is on or off. Additionally, the
control unit 60 may also bypass steps 228 and 232 and proceed
directly to step 236 to disengage the PTO 48. The control unit 60
may also perform other combinations of the steps shown in FIG.
5.
[0039] The foregoing detailed description describes only a few of
the many forms that the present invention can take, and should
therefore be taken as illustrative rather than limiting. It is only
the claims, including all equivalents that are intended to define
the scope of the invention.
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