CLAIMS
1. A tractor comprising^
a lift arm for hang-supporting a traction type implement;
5 a hydraulic actuator for pivotally driving the lift arm in a vertical
direction!
a control valve for controlling operation of the hydraulic actuator;
a height setting lever for setting a control target height of the
implement;
10 a first link mechanism for operably linking a spool of the control
valve to the height setting lever;
a load detecting member movable back and forth in accordance with a traction load;
a second link mechanism for operably linking the spool to the
15 load detecting member; and
a sensitivity adjusting mechanism for varying operational sensitivity of the spool when this spool is operably linked to the load detecting member;
wherein when the traction load exceeds a set value, the load
20 detecting member is displaced to a vehicle body front side in association
with rise of the traction load and the load detecting member is displaced
to a vehicle body rear side in association with drop of the traction load;
wherein the first link mechanism includes a pivot arm that
comes into contact with the height setting lever from a high-position
25 setting side of the height setting lever;
the first link mechanism operates the spool toward an elevated
position side when the pivot arm is pivoted in a high-position setting
direction in association with a pivotal operation on the height setting
lever in a high-position setting direction;
30 the first link mechanism allows movement of the spool toward a
lowered positon side in association with a pivotal operation on the height setting lever in a low-position setting direction; and
the first link mechanism operates the spool to a neutral positon
when the pivotal movement of the pivot arm is stopped in association
35 with stop of a pivotal operation on height setting lever!
wherein the second link mechanism includes an operational arm
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pivotally supported to the pivot arm J
the second link mechanism operates the spool toward the
elevated position side when the operational arm is pivoted in the
high-position setting direction to press the pivot arm in association with
5 a movement of the load detecting member toward the vehicle body front
side;
the second link mechanism allows a movement of the spool
toward the lowered-position side when the operational arm is pivoted in
the low-position setting direction to move away from the pivot arm in
10 association with a movement of the load detecting member toward the
vehicle body rear side;
the second link mechanism operates the spool to the neutral
positon when the pivotal movement of the pivot arm is stopped in
association with stop of a movement of the load detecting member! and
15 the second link mechanism includes a relay arm for relaying the
operative linkage of the operational arm with the load detecting member;
wherein the relay arm is pivoted about a pivotal support shaft
supported to a supporting member provided on the vehicle body side with
the pivotal support shaft being position-changeable relative to the
20 supporting member; and
wherein the sensitivity adjusting mechanism includes a
sensitivity adjusting lever disposed in a driving section and a linking
member extending from the sensitivity adjusting lever to the pivotal
support shaft: and
25 the sensitivity adjusting mechanism adjusts the operational
sensitivity by varying a gap between the pivot arm and the operational arm in association with change of a fixed position of the pivotal support shaft by an operation on the sensitivity adjusting lever.
30 2. The tractor according to claim 1. wherein the relas* arm is
disposed under a vertically oriented posture to be pivotahle hack and forth about the pivotal support shaft which is under a left/right oriented posture.
35 3. The tractor according to claim 2, wherein"
the relay arm is balance-pivoted in the front/rear direction about
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the pivotal support shaft; and
the second link mechanism includes a first linking member
extending from the load detecting member to an upper end portion of the
relay arm and a second linking member extending from a lower end
5 portion of the relay arm to the operational arm.
4. The tractor according to claim 3, wherein^
the first linking member is disposed on one left/right side of the
relay arm and connected to an upper end portion of the relay arm from
10 the one left/right side of the relay arm; and
the second linking member is disposed on the other left/right side
of the relay arm and connected to a lower end portion of the relay arm
from the other left/right side of the relay arm.
15 5. A tractor comprising^
a lift arm for hang-supporting a traction type implement; a hydraulic actuator for pivotally driving the lift arm in a vertical direction,'
a control valve for controlling operation of the hydraulic actuator;
20 an urging means for urging a spool of the control valve to return
to its lowered position!
a height setting lever for setting a control target height of the implement;
a first link mechanism for operably linking the spool to the
25 height setting lever;
a feedback link mechanism for operably linking the spool to the lift arm;
a load detecting member movable back and forth in accordance
with a traction load;
30 a second link mechanism for operably linking the spool to the
load detecting member; and
a sensitivity adjusting mechanism for varying operational
sensitivity of the spool when this spool is operably linked to the load
detecting member;
35 wherein when the traction load exceeds a set value, the load
detecting member is displaced to a vehicle body front side in association
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with rise of the traction load and the load detecting member is displaced
to a vehicle body rear side in association with drop of the traction load; wherein the first link mechanism includes a pivot arm that
comes into contact with the height setting lever from a high-position
5 setting side of the height setting lever;
the first link mechanism operates the spool toward an elevated
position side when the pivot arm is pivoted in a high-position setting
direction in association with a pivotal operation on the height setting
lever in a high-position setting direction,;
10 the first link mechanism allows movement of the spool toward a
lowered positon side in association with a pivotal operation on the height
setting lever in a low-position setting direction; and
wherein the second link mechanism includes an operational arm
pivotally supported to the pivot arm;
15 the second link mechanism operates the spool toward the
elevated position side when the operational arm is pivoted in the
high-position setting direction to press the pivot arm in association with
a movement of the load detecting member toward the vehicle body front
side? and
20 the second link mechanism allows a movement of the spool
toward the lowered-position side when the operational arm is pivoted in
the low-position setting direction to move away from the pivot arm in
association with a movement of the load detecting member toward the
vehicle body rear side!
25 wherein the feedback link mechanism operates the spool to a
neutral position in response to arrival of the implement at the control
target height or stop of the pivotal movement of the load detecting
member; and
wherein the sensitivity adjusting mechanism adjusts the
30 operational sensitivity by varying a gap between the pivot arm and the
operational arm in response to an operation on. a sensitivity adjusting
lever disposed in a driving section.
6. The tractor according to claim 5, wherein the second link
35 mechanism includes a relay arm which is disposed under a vertical
posture and is balance-pivoted in the front/rear direction about a pivotal
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support shaft which is disposed under a left/right oriented posture, a
first linking member extending from the load detecting member to an
upper end portion of the relay arm and a second linking member
extending from a lower end portion of the relay arm to the operational
5 arm.
7. The tractor according to claim 6, wherein:
the first linking member is disposed on one left/right side of the
relay arm and connected to an upper end portion of the relay arm from
10 the one left/right side of the relay arm? and
the second linking member is disposed on the other left/right side
of the relay arm and connected to a lower end portion of the relay arm
from the other left/right side of the relay arm.
15 8. The tractor according to claim 6 or 7, wherein:
the pivotal support shaft is supported to a supporting member provided on the vehicle body side, with the pivotal support shaft being position-changeable relative to the supporting member;
the sensitivity adjusting mechanism includes a linking member
20 extending from the sensitivity adjusting lever to the pivotal support
shaft: and
the sensitivity adjusting mechanism varies a gap between the
pivot arm and the operational arm in association with change of a fixed
position of the pivotal support shaft by an operation on the sensitivity
25 adjusting lever.
9. A tractor comprising1
a lift arm for hang-supporting a traction type implement;
a hydraulic actuator for pivotally driving the lift arm in a vertical
30 direction;
a control valve for controlling operation of the hydraulic actuator;
a load detecting member displaceably supported to a supporting member which is fixed to a vehicle body rear portion;
an urging mechanism for urging displacement of the load
35 detecting member in a direction against a traction load applied to the
load detecting member; and
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a link mechanism for operably linking a spool of a the control valve to the load detecting member;
wherein the urging means includes a coil spring configured to
allow displacement of the load detecting member according to the
5 traction load when the traction load exceeds a set value.
10. The tractor according to claim 9, wherein:
the load detecting member is supported via a supporting shaft to
the supporting member to be pivotally displaceable relative thereto; and
10 the urging mechanism is disposed between the supporting
member and a free end portion of the load detecting member.
11. The tractor according to claim 10, wherein^
there is provided a restricting mechanism for restricting
15 displacement of the load detecting member? and
the restricting mechanism is disposed at a position between the supporting shaft and the urging mechanism, which position is between the supporting member and the load detecting member.
20 12. The tractor according to claim 11, wherein the restricting
mechanism includes an elongate hole which is formed in one of the supporting member and the load detecting member and formed elongate in a displacing direction of the load detecting member, and a pin attached to the other of the supporting member and the load detecting
25 member and inserted into the elongate hole.
13. The tractor according to anj^ one of claims 9-12, wherein the urging mechanism includes a spring force adjusting portion for allowing change of the set value.
Dated (his 13 day of June 20<6
(R RNair) Reg. No.: !\VPA -121 Of De Penning & i)e Penning Agent for the Applicants
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