Note: Descriptions are shown in the official language in which they were submitted.
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IiAND/FOOT SELECTOR FOR ELECTRONIC CONTROLS
ON A SKID STEER LOADER
BACKGROUND OF THE INVENTION
The present invention deals with power
machines. More specifically, the present invention
deals with electronic controls of hydraulic cylinders on
a skid steer loader.
Power machines, such as skid steer.loaders,
typically have a frame which supports a cab or operator
compartment and a movable lift arm which, in turn,
supports a work tool such as a bucket. The movable lift
arm is pivotally coupled to the frame of the skid steer
loader and is powered by power actuators which are
commonly hydraulic cylinders. In addition, the tool is
coupled to the lift arm and is powered by one or more
additional power actuators which are also commonly
hydraulic cylinders. An operator manipulating a skid
steer loader raises and lowers the lift arm and
manipulates the tool, by actuating the hydraulic
cylinders coupled to the lift arm, and the hydraulic
cylinder coupled to the tool. Manipulation of the lift
arm and tool is typically accomplished through manual
operation of foot pedals or hand controls which are
attached by mechanical linkages to valves (or valve
spools) which control operation 'of the hydraulic
cylinders.
Skid steer loaders also commonly have an
engine which drives a hydraulic pump. The hydraulic
pump powers hydraulic traction motors which provide
powered movement of the skid steer loader. The traction
motors are commonly coupled to the wheels through a
drive mechanism such as a chain drive. A pair of
steering levers are typically provided in the operator
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compartment which are movable fore and aft to control
the traction motors driving the sets of wheels on either
side of the skid steer loader. By manipulating the
steering levers, the operator can steer the skid steer
loader and control the loader in forward and backward
directions of travel.
It is also common for the steering levers in
the operator compartment of the skid steer loader to
have hand grips which support a plurality"of buttons or
actuable switches. The switches are actuable by the
operator and are configured to perform certain
functions.
SUMMARY OF THE INVENTION
A control system controls actuation of a
hydraulic cylinder on a skid steer loader. The control
system includes two or more movable elements, such as a
foot pedal or a hand grip. Position sensors are coupled
to the moveable elements and provide element position
signals indicative of a position of the movable
elements. A selector is user actuable to select one of
{
the movable elements. A controller is coupled to the
position sensors to receive the element position signals
and provide a control signal based on the selected one
of the movable elements. A valve spool controls flow of
hydraulic fluid to the hydraulic cylinder. An actuator
is coupled to the controller and the valve spool and
moves the valve spool in response to the control signal
from the controller.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a skid-steer loader
according to the present invention.
FIGS. 2A-2C are block diagrams of a number of
embodiments of a control system in accordance with the
present invention.
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FIGS. 3A and 3B illustrate a hand grip
assembly according to one embodiment of the present
invention. FIGS. 4A, 4B, 4C, 4D and 4E are side sectional
views of a portion of the hand grip assembly according
to the present invention.
FIGS. 4F, 4G and 4H illustrate one preferred
embodiment of a resistive sensor configuration.
FIGS. 5A, 5B and 5C are side views of a
portion of a hand grip assembly according to the present
invention illustrating operation.
FIGS. 6A and 6B illustrate control band
adjustment according to the present invention.
FIG. 7 is a second embodiment of a hand grip
assembly according to the present invention.
FIGS. 8A and 8B are illustrations of preferred
embodiments of a valve spool position sensor according
to the present invention.
FIGS. 9A and 9B are a perspective view and
side view, respectively, of another embodiment of a hand
grip assembly according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a side elevational view of a skid
steer loader 10 according to the present invention.
Skid steer loader 10 includes a frame 12 supported by
wheels 14. Frame 12 also supports a cab 16 which
defines an operator compartment and which substantially
encloses a seat 19 on which an operator sits to control
skid steer loader 10. A seat bar 21 is pivotally
coupled to a front portion of cab 16. When the operator
occupies seat 19, the operator then pivots seat bar 21
from the raised position (shown in phantom in FIG. 1) to
the lowered position shown in FIG. 1.
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A pair of steering levers 23 (only one of
which is shown in FIG. 1) are mounted within cab 16.
Levers 23 are manipulated by the operator to control
forward and rearward movement of skid steer loader 10,
and in order to steer skid steerr loader 10.
A lift arm 17 is coupled to frame 12 at pivot
points 20 (only one of which is shown in FIG. 1, the
other being identically disposed on the opposite side of
loader 10). A pair of hydraulic cylinders 22 '(only one
of which is shown in FIG. 1) are pivotally coupled to
frame 12 at pivot points 24 and to lift arm 17 at pivot
points 26. Lift arm 17 is coupled to a working tool
which, in this preferred embodiment, is a bucket 28.
Lift arm 17 is pivotally coupled to bucket 28 at pivot
points 30. In addition, another hydraulic cylinder 32
is pivotally coupled to lift arm 17 at pivot point 34
and to bucket 28 at pivot point 36. While only one
cylinder 32 is shown, it is to be understood that any
desired number of cylinders can be used to work bucket
28 or any other suitable tool.
The operator residing in cab 16 manipulates
lift arm 17 and bucket 28 by selectively actuating
hydraulic cylinders 22 and 32. In prior skid steer
loaders, such actuation was accomplished by manipulation
of foot pedals in cab 16 or by actuation of hand grips
in cab 16, both of which were attached by mechanical
linkages to valves (or valve spools) which control
operation of cylinders 22 and 32. However, in
accordance with the present invention, this actuati-on is
accompli shed-by moving a movable -element-; cuch as a foot
pedal or a hand grip on steering lever 23, and
electronically controlling movement of cylinders 22 and
32 based on.the movement of the movable element.
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By actuating hydraulic cylinders 22 and
causing hydraulic cylinders 22 to increase in length,
the operator moves lift arm 17, and consequently bucket
28, generally vertically upward in the direction
indicated by arrow 38. Conversely, when the operator
actuates cylinder 22 causing it to decrease in length,
bucket 28 moves generally vertically downward to the
position shown in FIG. 1.
The operator can also manipulate bucket 28 by
actuating cylinder 32. This is also preferably done by
pivoting a movable element (such as a foot pedal or a
hand grip on one of levers 23) and electronically
controlling cylinder 32 based on the movement of the
element. When the operator causes cylinder 32 to
increase in length, bucket 28 tilts forward about pivot
points 30. Conversely, when the operator causes
cylinder 32 to decrease in length, bucket 28 tilts
rearward about pivot points 30. The tilting is
generally along an arcuate path indicated by arrow 40.
System Block Diacrram
1. Control System 42
FIG. 2A is a block diagram which better
illustrates operation of a control system 42 according
to the present invention. Control system 42 includes an
operator moveable element such as hand grip assembly 44,
foot pedal assembly 45 or another suitable movable
element. Control system 42 also includes position
sensor 46, controller 48, actuator 50, valve spool 52
and hydraulic cylinder 54. In the preferred embodiment,
control system 42 is also coupled to an interface
control system 58 which includes a plurality of sensors
60, an operator interface 62 and an interface controller
64.
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It should be noted that the present invention
can be implemented using any suitable operator movable
element. Also, a combination of elements such as
movable hand grip 44 and foot pedal 45 can be provided
to accomplish desired movement of hydraulic cylinders.
FIG. 2A illustrates this embodiment which shows an
additional movable elements 44', an additional position
sensor 46', an additional actuator 50', an additional
valve spool 52' and an additional hydraulic cylinder
54'. Such movable elements can be used to accomplish
movement of a number of different cylinders. Also, two
or more different movable elements can be provided as
alternative elements usable to accomplish movement of a
single cylinder. In this latter case, switches (such as
optional switches 47 and 49) are provided for the
operator to select the particular movable element which
the operator desires to be the operator input mechanism.
For the sake of clarity, the present description
proceeds with respect to hand grip assembly 44 only. It
should be recognized that a similar assembly can be used
with a foot pedal or other movable element as well.
Hand grip assembly 44 is preferably pivotally
mounted to one of steering levers 23 in loader 10. The
hand grip is preferably mounted for pivoting in a
direction which lies in a plane substantially transverse
to the direction of movement of steering levers 23.
Position sensor 46, in one preferred embodiment, is a
potentiometer or resistive strip-type position sensor.
As hand grip assembly 44 is pivoted, position sensor 46
senses movement of hand grip assembly 44 and provides a
position signal indicative of the position of hand grip
assembly 44.
Controller 48 is preferably .a digital
microcontroller or microcomputer, and receives the
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position signal from position sensor 46. In response to
the position signal, controller 48 provides a control
signal to actuator 50. Actuator 50 is preferably a linear actuator
which is coupled to valve spool 52 by a suitable
linkage. In response to the control signal provided by
controller 48, actuator 50 moves valve spool 52 in a
desired direction. It should be noted that actuator 50
can also be any suitable actuator such as; for example,
one which is integrally formed with the valve which it
actuates or spool 52. The precise mode by which spool
52 is moved is not critical to the primary inventive
features of the invention. Valve spool 52 is coupled to
hydraulic cylinder 54 and controls flow of hydraulic
fluid to hydraulic cylinder 54 in response to the output
from actuator 50. In the preferred embodiment,
hydraulic cylinder 54 is one of hydraulic cylinders 22
and 32. Therefore, control system 42 manipulates lift
and tilt cylinders 22 and 32 based on pivotal movement
of hand grip assembly 44.
Controller 48 also receives a feedback signal
which indicates the position of valve spool 52. In one
embodiment, controller 48 receives the feedback signal
from actuator 50 indicating the position of actuator 50.
This, in turn, indicates the position of valve spool 52.
In another embodiment, controller 48 receives the
feedback signal from valve spool 52 which directly
indicates the position of valve spool 52. Upon
receiving the feedback signal from either actuator 50 or
valve spool 52, controlier 48 compares the actual
position of valve spool 52 to the target or input
position from hand grip assembly 44 and makes necessary
adjustments. Thus, controller 48 operates in a closed
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loop fashion. This process is described in greater
detail later in the specification.
FIG. 2B is a block diagram of another
embodiment of control system 42 in accordance with one
aspect of the present invention. A number of the blocks
shown in FIG. 2B are similar to those shown in FIG. 2A,
and are similarly numbered. However, instead of having
a single position sensor 46, as illustrated in FIG. 2A,
FIG. 2B illustrates that position sensbrs associated
with hand grip 44 and foot pedal 45 can be two separate
position sensors 46 and 51, respectively. In addition,
rather than having a switch assembly upstream of the
position sensors, FIG. 2B illustrates that selector 53
is provided between the position sensors and controller
48. In one illustrative embodiment, selector 53 is an
electronic switch mounted on the dashboard, on a hand
grip, or on some other suitable location within the
operating compartment of the loader, so that it can be
easily accessed by the operator. Of course, selector 53
can be any number of other items, such as an input
button on a keypad, an input on a touch sensitive
screen, a toggle switch which changes the selected input
device with each actuation thereof, a rotatable switch
on the dashboard, a depressible button, etc. The
operator provides an input to selector 53 which selects
one of the position signals from position sensor 46 or
position sensor 51, and provides that position sensor
signal to controller 48. Optionally, selector 53 can
provide an output to a visual display (not illustrated
in FIG. 2B) or to operator interface 62 which displays
to the user which particular input device (hand grip 44
or foot pedal 45) is currently selected.
FIG. 2C illustrates another embodiment of
control system 42 in accordance with one aspect of the
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present invention. A number of the blocks shown in FIG.
2C are similar to those shown in FIGS. 2A and 2B, and
are similarly numbered. However, FIG. 2C illustrates
that the signals from position sensors 46 and 51 can be
provided as inputs to controller 48 (which is shown with
associated memory 57). In addition, selector 55 is
shown as providing an output to controller 48. In one
illustrative embodiment, selector 55 is any suitable
operator input device (such as the selectors mentioned
above) and can receive an operator input and provide an
output signal indicative of the operator input. In one
embodiment, selector 55 also provides an output to a
visual display item.
Therefore, the operator provides an input to
selector 55 which is indicative of a desired one of hand
grip 44 and foot pedal 45, which the user desires for
manipulation of valve spool 52. That signal is provided
to controller 48. Controller 48 then controls the
actuator or valve spool 52 based upon the selected
signal from the appropriate position sensor, and simply
ignores the position signal from the other position
sensor. When the operator again provides an input to
selector 55 selecting the other of the operator input
devices (hand grip 44 or foot pedal 45) controller 48
configures itself appropriately so that it controls
actuator 50 or valve spool 52 based upon the newly
selected input device.
Similarly, FIG. 2C shows that control system
42 includes memory 57. While controller 48 will likely
have associated memory in all embodiments, FIG. 2C
specifically illustrates memory 57 for the sake of
clarity. In one illustrative embodiment, a number of
criteria are programmed into memory 57 which can be
accessed by controller 48. Such criteria indicate
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certain conditions under which controller 48 will allow,
or disallow, the user to make a selection, or change the
selection, of hand grip 44 and foot pedal 45. -
For instance, memory 57 can be programmed with
a procedure by which controller 57 receives necessary
data from the operator through operator interface 62 and
interface controller 64 such that only authorized
personnel can select between hand grip 44 and foot pedal
45. Such a procedure may include the entry of a
password, or other suitable authentication information,
before controller 48 will allow the user to select
between hand grip 44 and foot pedal 45.
Similarly, operating conditions may be
programmed into memory 57 which controller 48 accesses
prior to allowing a selection between hand grip 44 and
foot pedal 45 based on an input to selector 55. For
instance, if the hand grip 44 is selected, and it is in
the actuation position such that actuator 50 is
currently moving valve spool 52 (or holding it in an
open position, for instance), it may be desirable to
preclude controller 48 from allowing the user to select
foot pedal 45, at that moment. Instead, controller 48
may access the operating criteria stored in memory 57
and the valve spool position provided by valve spool 52
and realize that the currently selected operator input
device is being used to actuate actuator 50. Controller
48 can then disallow the selection and provide a display
(such as at operator interface 62) indicating to the
operator that the selection cannot be honored until the
operator de-actuates actuator 50 by moving the selected
operator input device (in this case hand grip 44) to its
neutral position. Any other desirable operating
conditions, or selection criteria, or selection
procedures, can also be programmed into memory 57 for -
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access by controller 48 in changing the selected
operator input device.
2. Interface Control System 58 Interface control system 58 is described in
greater detail in U.S. Patent No. 5,425,431, issued on
June 20, 1995, to Brandt et al., entitled INTERLOCK
CONTROL SYSTEM FOR POWER MACHINE, assigned to the same
assignee as the present application, and hereby
incorporated by reference. Briefly, interface control
system 58 receives input signals from a plurality of
sensors 60 which indicate operating parameters such as
operator presence from a seat sensor, and such as seat
bar position from a seat bar sensor. Interface
controller 64 also receives inputs from operator
interface 62 which, in one preferred embodiment, is
simply an ignition switch and a display. Based on the
inputs received, interface controller 64 controls
certain hydraulic and electrical components in skid
steer loader 10. Interface controller 64 preferably
inhibits certain operation of loader 10 until some
certain combination of inputs from sensors 60 is
received. For instance, upon receiving appropriate
signals, interface controller 64 may enable operation of
wheels 14, or may enable certain hydraulic functions
performable by skid steer loader 10.
Interface controller 64 is also preferably a
digital computer, microcontroller, or other suitable
controller. Interface controller 64 is connected to
controller 48 by a serial bus, a parallel bus, or other
suitable interconnection.
3. Interaction Between Systems 42 and 58.
Interface controller 64 is also configured to
disable operations performable by controller 48 under
certain circumstances. For example, upon power-up,
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interface controller 64 inhibits the operators
performable by controller 48 until sensors 60 indicate
that seat bar 21 is in the lowered position and that the
operator is in seat 19. At that point, interface
controller provides controller 48 with a signal enabling
controller 48 to perform functions. If, however,
sensors 60 were to indicate that the operator is not in
seat 19, or that the seat bar 21 is not in the lowered
position, interface controller 64 would continue to
provide controller 48 with a signal inhibiting actuation
of cylinders 22 or 32 until the sensors 60 provide
appropriate signals.
Once sensors 60 provide signals which allow
controller 64 to "unlock" controller 48, controller 48
also performs certain diagnostic or calibration
functions. For instance, hand grips 44 are preferably
biased to a neutral position. Upon power-up or at
predetermined intervals, controller 48 determines
whether hand grip 44 is in the neutral position (or
.20 within some predetermined range of the neutral position)
based on the position signal from position sensor 46.
If not, controller 48 preferably provides a signal to
controller 64 causing controller 64 to continue to
inhibit any selected operations of loader 10, such as
actuation of the particular hydraulic cylinder to which
controller 48 is attached, until hand grip 44 is brought
into the neutral position for a suitable time period.
This essentially prevents immediate actuation of
cylinders 22.and 32 upon power-up of control system 42.
Instead, hand grip 44 must preferably start in the
neutral position at power-up, or come within the neutral
position and remain there for some predetermined time
period before actuation can occur.
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In addition, controller 48 also initially
determines whether valve spool 52 is in a neutral
position or within a predetermined range of the neutral
position (i.e., a position in which actuation of
cylinder 54 is not taking place) based on the feedback
signal. If not, interface controller 64 simply
continues to lock out selected operations of loader 10.
For diagnostic purposes, controller 48 may attempt to
drive valve spool 52 into the neutral position by
controlling actuator 50 accordingly. If controller 48
cannot drive valve spool 52 to the neutral position,
controller 48 preferably signals to interface controller
64 that valve spool 52 cannot be driven to neutral.
Interface controller 64 then takes appropriate action,
such as disabling certain functions of skid steer loader
10 and indicating to the operator that operation will
not commence until remedial action is taken.
Controller 48 also provides calibration
functions. For example, upon startup, and assuming hand
grip 44 and valve spool 52 are within a given range of
neutral, controller 48 stores the values of the position
signal from position sensor 46 and from the feedback
signal as the neutral values for hand grip 44 and valve
spool 52, respectively. Controller 48 then centers a
control band used by controller 48 to control actuator
50 around the neutral valves. This is described in
greater detail later in the specification.
While the above description has proceeded
describing controllers 48 and 64 as separate
controllers, it is to be understood--that the functions
performed by each can be combined into a single
controller, or can be divided among a greater number of
controllers. Such a combination or division of
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functions may be desirable depending on a given
application.
4. Float and Detent
Controller 48 also preferably controls
cylinder 54 to accomplish another function. It may be
desirable, at certain times, for the operator of skid
steer loader 10 to cause lift arm 17 (or the tool, such
as bucket 28) to float. By floating it is meant that
there is no positive hydraulic control of 'the particular
cylinder which is floating.
For instance, the operator of skid steer
loader 10 may wish to operate skid steer loader 10 so
that bucket 28, and lift arm 17, follow the terrain over
which loader 10 is traveling. In that case, the
operator simply pivots hand grip 44 to a predetermined
position (such as to one extreme end of pivoting
travel), and this indicates to controller 48 that the
operator wishes to cause the particular hydraulic
cylinder under control to float. In response,
controller 48 provides a control signal to actuator 50
causing actuator 50 to move valve spool 52 to a position
which effectively connects both hydraulic inputs to
hydraulic cylinder 54 together. In this way, the oil
which actuates hydraulic cylinder 54 is not pressurized
and is free to move from one end of.cylinder 54 to the
other in response to forces exerted on the cylinder by
changes in the terrain. In the preferred embodiment,
and'as will be described later in the specification,
hand grip 44 is moved to one extreme end of travel where
a detent engages to hold hand grip 44 in the float
position until the operator wishes to remove hand grip
44 from the float position.
Hand Grip Assembly 44
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FIGS. 3A and 3B are rear and side views,
respectively, of a left hand steering lever 23 including
a hand grip assembly 44 according to the present
invention. FIG. 3B is a view of steering lever 23 taken
in the direction indicated by'line 3B-3B in FIG. 3A.
Hand grip assembly 44 includes handle 66 and channel arm
68. Channel arm 68 is coupled to a curved tubular
member 70 which is, in turn,-coupled to a lower portion
of steering lever 23.
Handle 66 is pivotally coupled to channel arm
68 at pivot point 72. Position sensor 46 is mounted to
channel arm 68 and is also coupled to handle 66 at pivot
point 74. In the preferred embodiment, and as will be
described in greater detail with respect to FIGS. 4A-4E,
position sensor 46 includes a plunger 76 which is
pivotally coupled to handle 66 at pivot point 74 and is
reciprocable within cylinder 78. Plunger 76 is biased
to a neutral position (shown in FIGS. 3A and 3B) so that
handle 66 is slightly tilted inwardly from vertical
(with respect to the operator) and pivotable about pivot
point 72 in both directions, from the neutral position,
generally in a direction indicated by arrow 80. As
handle 66 is pivoted, plunger 76 reciprocates within
cylinder 78. Plunger 76 and cylinder 78 have elements
which interact to provide a signal, on a plurality of
conductors 82 which is indicative of the position of
handle 66. This signal is provided to controller 48.
Position sensor 46 is pivotally mounted to
channel arm 68 at pivot points 84.. This is to
accommodate the slight arc through which pivot point 74
travels during pivoting of handle 66.
Position Sensor 46
FIGS. 4A, 4B and 4C illustrate position sensor
46 with the outer portions of housing 78 cut away for
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clarity. FIGS. 4D, 4E and 4F illustrate one embodiment
of position sensor 46 in partial schematic form. FIG.
4A shows position sensor 46 in the extremely retracted
position, FIG. 4B shows position sensor 46 in a neutral
position, and FIG. 4C shows position sensor 46 in the
extremely extended position.
FIGS. 4A-4C show that housing 78 of position
sensor 46 has first housing portion 78A and second
housing portion 78B which are bolted together'. Cap 86
is bolted to portion 78A and secures a washer 88 and
gasket 90 to housing portion 78A.
Plunger 76 has a first shaft portion 92 which
extends within an aperture in cap 86 and into housing
portion 78A, through a spacer 93. Spacer 93 is
preferably contained within housing portion 78A and may
also be securely attached to housing portion 78A to
position plunger 76 radially within housing 78. Plunger
76 also has a second portion 94 which carries a tab
support member 96 on its outer periphery. Tab support
member 96 is preferably frictionally fit on the outer
periphery of shaft portion 94. A spacer block 98 is
also preferably frictionally fit on the outer periphery
of shaft portion 94.
A pair of annular standoffs 100 and 102 are
disposed about shaft portion 94. Standoffs 100 and 102
are movable in a longitudinal direction (defined by axis
106) relative to one another and are preferably urged
away from one another by a bias member (e.g., a spring)
103. Shaft portion 94 is also attached to a cylinder
member 108 which moves reciprocally within a cylinder
receiving cavity defined by cavity member 110 in housing
portion 78B.
The cavity member 110 has an annular notch 112
formed therein. Cylinder member 108 has a pair of
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oppositely disposed spring receiving notches 114 formed
therein. Compression springs 116 are provided in
notches 114, and a small ball bearing, or detent member
118 is also provided in notches 114. Cylinder member
108 also has a second pair of oppositely disposed spring
receiving notches 113 formed therein (shown in FIG. 4B).
Compression springs 115 are provided in notches 113 and
a small ball bearing or detent member 117 is also
provided in notches 115.
As plunger 76 is moved to the extremely
retracted position shown in FIG. 4A, annular standoff
100 compresses spring 103 against standoff 102 and
cylinder member 108 moves toward the position shown in
FIG. 4A. Detent members 117 engage a shoulder on cavity
member 110 and springs 115 are compressed so detent
members 117 move within notches 113. This provides the
operator with a feeling of a slight change in resistance
to movement of the hand-grip, indicating that the hand
grip is about to enter the detent position. Continued
movement. of cylinder member 108 causes compression
springs 116 to force detent members 118 out away from
the radial center of cylinder member 108. This causes
detent members 118 to engage annular notch 112 formed in
cavity member 110. This acts as a detent, holding
plunger 76 in the extremely retracted position until the
operator manually moves plunger 76 from that position by
forcibly pivoting the hand grip to extend plunger 76
from within housing 78. This causes detent members 118
to retract within notches 114, compressing springs 116
so that cylinder member 108 is free to move within
cavity member 110.
In the preferred embodiment, plunger 76 is
biased into the neutral position shown in FIG. 4B by an
appropriate bias means such as spririg 103. Spring 103
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forces the plunger 76 into the neutral position shown in
FIG. 4B when no operator force is applied to plunger 76,
and when plunger 76 is not in the detent position.
Housing portion 78A has disposed on its inner
radial surface a resistive strip or film 120. A number
of different sensor configurations can be used. In one
preferred configuration, a conductive tab 122 is
supported on tab support member 96 which is fixedly
attached to plunger 76. Both resistive''strip 120 and
tab 122 are electrically coupled, through conductors 82
shown in FIGS. 3A, 3B and 4E, to controller 48.
Essentially, tab 122 acts as a wiper along a linear
potentiometer formed by tab 122 and resistive strip 120.
As tab 122 moves along resistive strip 120, the signal
provided to controller 48 on conductors 82 changes thus
indicating the longitudinal position of plunger 76
within housing 78. Based on this position, controller
48 determines the degree to which the operator has
pivoted handle 66, and the direction of the pivot. This
allows controller 48 to appropriately control actuator
50 to accomplish the desired operation.
FIGS. 4F, 4G and 4H illustrate another
preferred sensor configuration. FIG. 4F shows resistive
strip 120 applied to the inner cylindrical surface of
housing portion 78A. Resistive strip 120 is preferably
applied as a resistive film. A flexible bubble-type
member 121 (preferably made of mylar) is disposed above
resistive strip 120 and is coated, on its interior
surface, with a conductive strip or film, such -as a
silver metalized film 123. Both sides of resistive
strip 120 preferably have conductors (such as wires or
printed copper or other suitable conductors) 125 and 127
connected thereto. Silver strip 123 preferably also has
a conductor 129 coupled theret'o.
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Operation of the configuration shown in FIG.
4F is better illustrated in FIG. 4G. A fixed voltage is
preferably applied across conductors 125 and 127: This
is schematically illustrated in FIG. 4H. Tab 122 (shown
in FIGS. 4A-4C, is slidably disposed relative to mylar
bubble 121 so that it is movable along mylar bubble 121
in the direction indicated by arrow 131 (along with
reciprocal plunger 76). As tab 122 moves in the
direction indicated by arrow 131, it cau8es a'different
portion of silver strip 123 to contact resistive strip
120. Controller 48 measures the signal produced as a
voltage position signal (Vpos) across conductors 125 and
129. The signal Vpos thus gives an indication of the
position of tab 122 along resistive strip 120, and hence
it gives an indication of the position of the plunger 76
relative to housing 78. This signal is digitized by A/D
controller 133 and provided to controller 48. This
allows controller 48 to appropriately control actuator
50 to accomplish the desired operation.
The output of A/D converter 133, in the
preferred embodiment, is 8 digital bits representing a
value ranging from 0 to 255.
Operation and calibration of the control
system is better illustrated in FIGS. 6A and 6B. At
power-up, controller 48 reads the position of hand grip
44 from the A/D converter 133 in position sensor 46. If
the position of hand grip 44 is within a predetermined
range of neutral, such as range A shown in FIG. 6A,
(i.e., if the value provided by A/D converter 133 is
between 117 and 137) then controller 48 assumes that
hand grip 44 is in the neutral position. In the
embodiment shown in FIG. 6A, hand grip 44 is in a
position corresponding to the value 127 provided by the
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A/D converter 133. This is within range A and
controller 48 proceeds.
Controller 48 then determines whether the
control band is set properly. In the embodiment shown
in FIG. 6A, the control band extends from the value 25
to the value 230 and is designated by the letter B.
Since the position of hand grip 44 corresponds to the
value 127, which fits squarely between 25 and 230,
controller 48 need not adjust control band B at all, and
can simply continue with normal operation.
In the embodiment disclosed in FIG. 6B, upon
power-up, controller 48 reads the A/D converter 133 and
finds that the hand grip 44 is in a position
corresponding with the value 120. While this is seven
digits shifted to the left of the optimal center, it is
still within range A. Therefore, controller 48
effectively shifts the control band B seven digits to
the left and continues control.
In the preferred embodiment, rather than
physically changing the boundaries of range B in memory,
controller 48 simply subtracts seven digits from any
number it subsequently reads from the A/D converter 133.
In other words, if the operator moves hand grip 44 to a
position such that the A/D converter 133 provides a
value of 140, controller 48 subtracts seven to yield a
result of 133. Controller 48 then operates actuator 50
as if the operator had requested actuator 50 to be moved
to a position corresponding to the value 130.
In the preferred embodiment, each digit in the
control band B set out in FIGS. 6A and 6B, is equal to
approximately five thousands of an inch of travel of
plunger 76. This will, of course, vary with different
implementations of position sensor 46. In addition, in
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the preferred embodiment, control band B is adequate to
allow 0.28 inches of movement on both sides of neutral.
Also, in the present invention, it has -been
found that a tolerance of one count in either direction
provides adequate results. In other words, if the
operator requests (through actuation of hand grip 44)
that controller 48 move actuator 50 to a position
corresponding to the number 16 from the A/D converter
133, then controller 48 moves actuator 50 until it is
one of numbers 15, 16 or 17. This eliminates the vast
majority of hunting, yet maintains adequate accuracy.
FIG. 4D is a similar illustration to that
shown in FIGS. 4A-4C, except that it is rotated 90
about axis 106. FIG. 4D better illustrates the
connections (by bolts 124) between housing portions 78A
and 78B and cap 86.
Further, FIG. 4D illustrates another feature
preferably used in accordance with the present
invention. A constant volume boot 128 is preferably
disposed about an upper portion of plunger 76. Boot 128
has a first end which is snugly secured above an annular
shoulder 130 of plunger 76. Boot 128 also preferably
has a lower portion which is snugly secured about
plunger 76 within a cavity 132 defined by cap 86. Boot
128 is preferably formed of a pliable and resilient
material which allows reciprocation of plunger 76 within
housing 78. However, by providing boot 128, debris or
other foreign matter is substantially incapable of
entering housing 78 and inhibiting operation of position
sensor 46.
FIG. 4E is a cross-sectional view of position
sensor 46 taken along section lines 4E-4E in FIG. 4D.
FIG. 4E shows that conductors 82 are preferably
connected to resistive strip 120 and.exit housing 78A
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through a conduit 134. One of conductors 82 is also
preferably connected to silver strip 123, and exits
through conduit 134 as well.
FIGS. 5A-5C are similar to FIGS. 4A-4C, except
that they show handle 66 mounted to plunger 76. FIGS.
5A-5C show the extremely retracted, the neutral, and the
extremely extended, positions of plunger 76 in position
sensor 46, respectively. In the preferred embodiment,
the extremely retracted position results from the
operator pivoting handle 66 through an arc 142 which is
approximately 42 . In the neutral position, the handle
rests at a position which is displaced from axis 143 by
approximately 14 . In the extremely extended position,
handle 66 has a longitudinal axis which preferably lies
on axis 143.
FIG. 7 illustrates another feature useable
with position sensor 46. FIG. 7 shows that handle 66 is
fitted with an ergonomic hand grip 146. The hand grip
146 shown in FIG. 7 is a left handed grip. A number of
switches 148, 150 and 152 are preferably provided on
hand grip 146 and can be actuated by the thumb of the
operator. Other items are similar to those shown in the
previous figures and are similarly numbered.
Actuator 50 and Valve Spool Position Sensor
One actuator which has been observed to be
suitable as actuator 50 is a linear actuator more
specifically described in the Nicholson et al. U.S.
Patent No. 5,187,993 which issued February 23, 1993.
Such a linear actuator is commercially available-from
Addco Manufacturing Inc. of St. Paul, Minnesota.
Briefly, as illustrated in FIG. 8B, the linear actuator
has a motor 45 that receives an electrical input and
causes corresponding rotation of a high pitch screw
threaded shaft 45 in a cylinder frame.. A push-pull rod
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47 is connected with a threaded nut 49 which moves along
the high pitch screw threaded shaft 45 in response to
rotation of the shaft 45. This essentially transforms
the rotational motion of the motor into linear movement.
The push-pull rod 47 from the actuator is preferably
coupled to valve spool 52 to cause linear positioning of
valve spool 52 in response to the control signal from
controller 48. Controller 48 preferably provides a
pulse width modulated signal to actuator'50 to control
actuator 50 as a function of the position signal
provided by position sensor 46.
Actuator 50 also has a tab 57 and resistive
strip 53 arrangement similar to that described with
respect to position sensor 46. The electrical signals
output by that arrangement are provided as the feedback
signal to controller 48 so that controller 48 can
determine the position of valve spool 52.
FIG. 8B illustrates another preferred
embodiment in which actuator 50 need not have any type
of position sensing mechanism. Rather, valve spool 52
is fitted with a position sensor arrangement 160 which
can be similar to position sensor 46. A plunger 170 is
provided at the base of the valve spool 52 and is urged
against the base of the valve spool 52. The plunger 170
moves along a linear resistor 168 and. provides an output
on conductors 172 which is indicative of the position of
plunger 170 relative to linear resistor 168. This
sigrial is provided to controller 48. Based on this
signal, controller 48 determines the precise position of
valve spool 52. This arrangement essentially acts as a
linear potentiometer.
Controller 48 monitors the feedback signal and
controls actuator 50 in a similar fashion to that with
respect to the position signal fed forward from position -
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sensor 46. In other words, upon power-up, controller 48
reads the position of actuator 50 (or valve spool 52)
and determines whether it is within a de"sired,
predetermined range. If not, controller 48 provides a
signal to interface controller 64 indicating that
interface controller 64 should maintain loader 10 in a
locked state.
However, if the position of actuator 50 (or
valve spool 52) is within the desired 'neutral range,
then controller 48 centers the control band around the
neutral position read by controller 48. As with the
embodiment shown in FIGS. 6A and 6B, this is typically
done by simply subtracting or adding a desired value to
the signal actually read from the A/D converter in the
position sensor which senses the position of actuator 50
(or valve spool 52). Then, when controller 48 receives
a desired position signal from position sensor 46, it
controls actuator 50 (or valve spool 52) until the
feedback signal indicates that the position of valve
spool 52 is at the desired position. Again, controller
48 preferably controls actuator 50 (or valve spool 52)
within plus or minus one count of the desired value.
Also, controller 48 controls actuator 50 (or
valve spool 52) in one of two ways at the extreme end of
travel. In other words, if controller 48 receives a
value from position sensor 46 indicating that controller
48 is to drive the actuator 50 (or valve spool 52) to a
point which is beyond one of the extreme ends of travel
of actuator 50 (or valve spool 52), controller 48
controls in one of two ways. In the preferred
embodiment, controller 48 drives actuator 50 (or valve
spool 52) to the extreme end of travel and monitors
movement. If it does not move for some predetermined
length of time (such as 100 milliseconds), then -
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controller 48 simply stops actuator 50 (or valve spool
52) at that position. In another, more simple
embodiment, controller 48 simply continually tries to
drive actuator 50 (or valve spool 52) to the requested
position, regardless of whether the requested position
is beyond one of the extreme ends of travel.
Alternative Hand Grip 44
FIGS. 9A and 9B are a perspective view and
side view, respectively, of another embod"iment of a hand
grip assembly 44' according to the present invention.
FIGS. 9A and 9B illustrate hand grip assembly 44'
implemented as a right hand grip mounted on a right hand
steering lever 23. Hand grip assembly 44' is similar to
hand grip assembly 44, and similar items are similarly
numbered. However, hand grip assembly 44' includes a
handle portion 200 which includes base portion 202. In
the preferred embodiment, handle portion 200 and base
portion 202 are integrally formed with one another by
die casting. This allows hand grip assembly 44' to be
manufactured very accurately, and with minimal
machining.
Base portion 202, in the preferred embodiment,
is a substantially hemispheric section. This allows the
operator to grasp both handle 200 and base portion 202
at the same time. Because of the large contact area
between the operator's hand and hemispheric base portion
202, the operator can achieve very fine control. it
should also be noted that handle 200 is slightly skewed
from base portion 202. This allows an ergonomic fit
between handle 200 and the operator's hand.
Although the present invention has been
described with reference to preferred embodiments,
workers skilled in the art will recognize that changes
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may be made in form and detail without departing from
the spirit and scope of the invention.
