Note: Descriptions are shown in the official language in which they were submitted.
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A TRACTOR DRAFT LOAD MONITORING SYSTEM
The present invention relates to a load
monitoring system.
U.S. Patent No. 3,575,241 issued April 20,
1971 to C.E. McKeon et al for a tractor Hydraulic Lift
System discloses a tractor provided with a torque
sensing device in the drive line to the tractor driving
wheels to control operation of an implement hydraulic
lift system for raising and lowering an implement as
required to maintain a constant torque on the drive
line. The patented system utilizes a torque sensitive
coupling in the driveline which through a complex
system of links and levers operates a valve means to
raise and lower the implement in response to changes in
driveline torque resulting from changes in implement
draft load.
This application is a division of copending
Canadian application Serial No. 316,205 filed November
14, 1978. As is set forth in the present application,
the invention relates to improvements in a tractor
having an engine and transmission power unit coupled to
a drive shaft. Resilient mounts mount the power unit
on the frame of the tractor and the ,esilient mounts
permit measurable angular displacement of the power
unit relative to the frame about the drive shaft axis
in reaction to changes in the drive shaft torque.
Hydraulic lift means is provided for raising and
lowering an earth working implement coupled to the
tractor. A control valve assembly is connected to a
source of fluid under pressure. Connecting means is
interposed between the power unit and the control valve
assembly to cause hydraulic actuation of the hydraulic
lift means to change the working depth of the implement
to compensate for changes in draft load.
In the structure claimed in the present
application, the resilient mounts are located
relatively high on the power unit thereby to increase
the degree of lateral movement of the bottom of the
power unit, such lateral movement being approximately
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proportional to the drive draft torque. The connecting
means is connected to the bottom of the power unit.
In accordance with the present invention, the
connecting means comprises a flexible cable means
attached at one end to the power unit and at its
opposite end to a lever means coupled to the control
valve assembly actuating member. The lever means
operable by the flexible cable means is coupled to a
manual operating means capable of operating the control
valve assembly actuating member independently of the
flexible cable means thereby to cause raising or
lowering of the implement by direct operation of the
servovalve. Movement of the manual operating means to
an extreme implement raising or lowering position
causes fluid flow to bypass the control valve assembly
thereby nullifying any effect the latter has on the
operation of the servovalve.
The present invention, therefore, relates to
details of manual actuation of the raising or lowering
of the implement to alter the position of the implement
in the ground and of the rapid raising or lowering of
the implement between operative and inoperative
positions. The use of a hydraulic system is much more
reliable than the prior art complicated mechanical
linkage.
The present invention is described further,
by way of illustration, with reference to the
accompanying drawings, in which:
Figure 1 is a schematic of the the principal
components of the load monitoring system embodying the
present invention; and
Figures 2a and 2b, together, are a detailed
schematic of the mechanical hydraulic components of the
load monitoring system.
Referring to the drawings, Figure
represents diagrammatically the relationship of a
tractor draft load monitoring system, generally
designated 10, to a tractor power unit 11. As
exemplified, the tractor power unit 11 is constructed
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with the engine, transmission and transfer case or drop
box as a single unit. The power unit 11 is coupled in
a conventional manner to a tractor drive shaft 12. The
power unit 11 is mounted to a tractor frame 13 by
resilient mounts 14 which permit the power unit to
rotate slightly, but measurably, about the longitudinal
axis of the drive shaft in reaction to the drive shaft
torque. The resilient mounts 14 are located relatively
high on the power unit 11 which causes the bottom 15 of
the power unit 11 to move sideways or laterally
relative to the drive shaft axis when the power unit
rotates in reaction to the drive shaft torque. Because
this sideways movement is approximately proportional to
drive shaft torque, this movement can be used as a
measure of implement draft or drawbar pull plus rolling
resistance of a tractor when the tractor is coupled to
an implement (not shown) in which the implement draft
is controlled by a single remote hydraulic lift means
for raising and lowering the implement.
The hydraulic lift means comprises a remote
hydraulic circuit generally designated 16 (See Fig. 2a)
that includes a double acting hydraulic lift cylinder
17 t a source of fluid under pressure indicated by an
inlet pipe 18 and a supply valve 19 interposed between
2~ the source of fluid and the lift cylinder. The supply
valve 19 is coupled to the lift cylinder 17 by a first
conduit 21 communicating with the head end 22 of the
lift cylinder and a second conduit 23 communicating
with the rod end 24 of the lift cylinder. The supply
valve contains a spool valve 25 which is maintained in
a neutral position by a centering spring (not shown) in
a conventional manner and when in this position no
fluid will flow to the hydraulic lift cylinder 17.
Movement of the spool valve 25 of the supply
valve 19 is controlled by a control valve assembly,
generally designated 26, that is also connected to a
source of fluid under pressure as indicated by an inlet
pipe 27 at the top of the control valve assembly, see
Fig. 2b. The control valve assembly 26 has several
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functions, the most important being to sense the
sideways movement of the power unit 11 and to transmit
that movement to the supply valve 19 to cause the
latter to supply fluid to either the head end 22 or the
rod end 24 of the lift cylinder 17 to raise or lower
the implement as may be required to adjust the draft
load on the tractor.
The sideways movement of the power unit 11 is
sensed by a flexible transmission cable 28 (of the
Bowden cable type) that has its transmission wire or
control core coupled at one end 29 (see Fig. 2a) to a
retainer 31 secured to the bottom of the power unit 11.
The other end 32 of the transmission wire 28 has a
spring-loaded connection through spring 33 to a clevis
34 having a pin 35 and slot 36 connection to a summing
bar 37 pivoted at its upper end 38 to a link 39
pivotally secured at one end 41 to an arm 42. The arm
42 is pivotally mounted intermediate its ends on a
bracket 43 attached to a tractor frame portion 44.
- 20 ~ At its lower end 45 the summing bar 37 is
pivotally connected to a clevis 46 coupled to one end
of a spool 47 of an input valve 48. The input valve 48
is shown as an integrated part of the control valve
assembly 26 and its spool 47 may be considered as the
actuator member of the control valve assembly.
To summarize to this point: The power unit
11 is connected through a connecting means, cable 28,
to the actuator member or spool 47 of the input valve
48 of the control valve assembly 26. The operation is
as follows. First, it is assumed that the tractor is
pulling an implement at a steady drawbar pull and that
the remote or hydraulic lift cylinder 17 controlling
the working depth of the implement is only partially
extended from a fully retracted position so that it can
move in either direction. Under steady conditions, the
input valve spool 47 will be centered as shown in Fig.
2b and no fluid will be flowing into the control valve
assembly 26.
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If the draft of the implement now increases
due to a change in soil conditions, the drive shaft
torque will increase and cause the power unit 11 to
move about the axis of the drive shaft 12. For
purposes of discussion, it will be assumed the motion
is clockwise as viewed in Fig. 2a. When this occurs,
the bottom of the power unit 11 moves to the left and
pulls on the transmission wire 28. The other end 32 of
the wire pulls on the summing bar 37 causing it to
pivot in a counter-clockwise direction about the link
39, as viewed in Fig. 2b. The movement of the summing
bar 37 pushes the input valve spool 47 to the right so
that fluid flows from the input conduit 27 to a passage
49a into a bore 51 in the control valve assembly 26.
The bore 51 contains a flow control spool 52 that
normally is centered, as seen in ~ig. 2a. The fluid
flows past the centered spool 52 into passage 53a into
a bore 54 containing an end of stroke spool 55a which
is at its outermost position. The fluid continues to
passage 56a into a servovalve cylinder 57 containing a
double acting piston 58. The fluid pressure causes the
piston 58 to move to the left.
The piston 58 is mounted on a piston rod 59
that extends outwardly of the control valve assembly
casing 61. The piston rod 59 and the spool valve 25
are coupled to each other by a coupling 62. Thus,
movement of the piston 58 to the left causes
corresponding movement of spool valve 25 directing
fluid to port 63 of the supply valve 19. Fluid from
port 19 flows through conduit 21 to the head end 22 of
the lift cylinder 17 causing the latter to extend. The
extension of the lift cylinder causes ta) the implement
to raise thereby reducing the draft load, and (b) fluid
to flow out of the rod end 24 of the lift cylinder
through the conduit 23 toward the supply valve outlet
port 65.
The conduit 23 contains a check valve 64
having a poppet 66 with an orifice hole 67 in it. At
low fluid flow, the oil flows through the orifice 67
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causing a pressure drop across the check valve 64. As
the flow increases, the pressure drop or pressure
differential increases until the pressure entering the
check valve 64 is greater than the pressure leaving the
check valve plus the force of a check valve spring 68
causing the poppet to open and thereby permitting fluid
flow around the latter.
The conduit 23 is tapped above and below the
check valve 64 by conduits 69 and 71. Whenever there
is fluid flow through the check valve 64, the pressure
in conduit 69 is higher than that in conduit 71. This
pressure differential acts on the flow control spool 52
causing the latter to move to the left, shutting
passage 49a and permitting fluid to flow from passage
53a through passage 72a to a sump 73. Thus, pressure
is removed from the servovalve piston 28 permitting the
supply valve centering spring to return the supply
valve spool 25 to neutral. This cuts off fluid to
conduit 21 stopping the operation of the remote
Cylinder 17.
If the position of the flexible cable 28
remains displaced from the original steady state
position, the input valve spool 47 will remain
displaced to the right, directing fluid into passage
49a. Since the supply valve spool 25 has returned to
neutral, pressures in passages 69 and 71 will be equal,
allowing the flow control spool 52a to return .to
center. This permits fluid to flow from passage 49a to
passage 53a and to the servovalve piston 51, thereby
initiating another implement raise cycle. The load
monitor will continue raising the implement in small
increments until the position of the flexible cable 28
indicates that the desired drawbar pull has been
attained.
Now, if soil condition, etc. change to reduce
drawbar pull, the load monitor will function in a
similar manner but in opposite direction. When the
draft is reduced, the power unit 11 rotates
counter-clockwise allowins the attached cable 28 to
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move to the right. When this occurs, the su~ming bar
37 pivots left about its pivotal connection with upper
link 39 pushed by the summing bar preload spring 74.
This pulls the input valve spool 47 left, directing
fluid from the input conduit 27 to passage 49b, then to
53b and 56b to the servo cylinder 57 moving the servo
piston 58 and remote valve spool 25 to the right. This
directs fluid from the remote supply to port 65 through
the orifice 67 in the check valve poppet 66 and to the
head end 24 of the remote cylinder 17. Retracting the
piston 75 of remote cylinder 17 will increase the draft
of the implement. As the fluid goes through the
orifice 66 in the check valve 64, there will be a
pressure drop and the pressure in passage 71 will be
higher than in passage 69. This causes the flow
control valve spool 52 to move to the right closing off
passage 49b and allowing the remote valve spool
centering spring to center the spool 25 and shut, thus
to stop the motion of the remote cylinder. This cycle
will repeat until the position of the flexible cable 28
indicates that the desired drawbar pull has been
reached.
When the operator desires to operate at a
different value of drawbar pull, he has to change the
position of a control lever 76. Assume that a
reduction in drawbar pull is desired. Moving the upper
end of the control lever 76 (shown in Fig. 2b) to .the
left will, through an adjustable link 77, move the
upper end 38 of the summing bar 37 to the left. As the
upper end 38 moves left, the bar 37 pivots about the
cable clevis 34 and its lower end 45 moves to the right
pushing the input valve spool 47 to the right. This
directs fluid to passage 49a then to 53a and 56a moving
the servo piston 58 and remote valve spool 25 to the
left. Thus, fluid from the remote supply is directed
to port 63 which extends the remote cylinder and raises
the implement reducing drawbar pull. Fluid passing
through the check valve 64 orifice 67 causes the
pressure in passage 69 to be higher than in passage 71
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moving the flow control spool 52 to the left stopping
the motion of the remote cylinder. As a result of the
reduction in drawbar pull, the cable clevis 34 moves to
the left moving the input valve spool 47 to the left
5 towards the center position. If the drawbar pull
reduction is sufficient, the input valve spool will be
centered and no further load monitor action will occur.
If the drawbar pull is still too high, the cycle will
repeat until the desired drawbar pull level is reached.
When an increase in drawbar pull is desired,
the operator moves the control lever to the right. The
load monitor system responds as above except in the
opposite direction.
A fast raisetfast lower mode is provided when
the remote cylinder 17 is to be moved to fully extended
or fully retracted position unhampered by the flow
control cycling. For fast raise (lift cylinder extend)
mode, the operator moves the control lever 76 to the
left extreme of its travel. This moves the top of the
summing bar 37 to the left first pivoting the summing
bar about the pin 78 of the clevis 34. When a pin 78
through the summing bar 37 and through a slotted hole
79 in link 81 reaches the left end of its travel, the
summing bar 37 then pivots about this pin 78. This
compresses the preload spring 74, releases the load on
clevis 34, and pushes the input valve spool 47 to its
extreme right position. Then the input fluid fl,ows
through the center axial hole 82 in the input spool 47
and to passage 83a. Passage 83a bypasses the flow
control spool 52 and the fluid flows directly to
passage 53a. Thus, in fast raise/fast lower mode,
movement of the flow control spool 52 will not affect
the fluid flow within the servovalve 51. The fluid
from 53a flows through the end of stroke bore 54 and
through passage 56a causing fluid to be directed to the
servovalve piston 58. Remote supply valve 19 fluid is
then directed to port 63 and the remote cylinder
extends.
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When the cylinder 17 reaches the end of its
travel, the pressure rises in the line 21 between port
63 and the remote cylinder 17 and this pressure is
transmitted by line 84 to the servovalve 51. When the
pressure ~limited by a supply valve pressure relief
valve 85) acts on a pin 86a, the pin 86a pushes the
right hand spool 55a to the left. This shuts off
passage 53a, shuts off the left end of passage 87a, and
opens passage 56a to sump 88a. The centering spring in
the supply valve returns the supply valve spool 25 to
neutral position and the remote cylinder 17 is held in
its extended position. The pressure from passage 53a
acts on the right end of the right hand spool 55a and
keeps it in its extreme left position until the input
valve spool 47 is centered again.
For fast lower mode, the control lever is
moved to the extreme right position. The system then
functions similar to the fast raise mode except in the
opposite direction with the control valve assembly
components marked with the postscript "b" being
involved. Similarly, when the cylinder 17 reaches the
end of its travel, the pressure build up in line 69 and
its branch 69a causes the pin 86b to push the left hand
spool 55b to the left. This shuts off passage 53b,
shuts off the left end of passage 87b, and opens
passage 56b to sump 88b. The supply valve centering
spring returns the supply valve spool 25 to a neutral
position and the remote cylinder is held in its
retracted position. The pressure from passage or
conduit 53b acts on the left end of the left end spool
55b and keeps it in its extreme right position until
the input valve spool 47 is centered again.
It is to be understood this invention is not
limited to the exact construction illustrated and
described above, but that various changes and
modifications may be made without departing from the
spirit and scope of the invention as defined by the
following claims.
