Deere + Company

William L Smith, Jr

Robert E Fox

Thomas Eugene Boe

Donald R Flugrad

A hydraulic rockshaft control circuit which includes a three-way valve that normally operates the rockshaft is connected to the lift cylinder on a trailing implement. A hitch lock valve connected to the rockshaft control valve maintains the rockshaft in a preselected position regardless of changes in pressure at the valve output. The extend side of the lift cylinder is connected to the control valve output so that the tractor hitch control is used to operate the trailing implement cylinder. To overcome the inability of the three-way valve to positively retract the trailing implement cylinder, a reducing/relieving valve is connected to the retract side of the cylinder and is adjusted to provide just enough pressure to retract the cylinder and raise the implement wheels from ground contact when the extend side is connected to return pressure. A position feedback system on the implement is connected to the hitch control unit (HCU) on the tractor. When the HCU senses a feedback signal from the implement, the HCU control mode changes from rockshaft control to trailing implement control wherein implement position is set and maintained in a manner similar to that for the conventional rockshaft control. A voltage readout from the feedback signal provides a visual indication of implement position.

Hydraulic system for a towed implement

A feedback mechanism for providing an implement position signal includes a rotary potentiometer mounted on the implement frame adjacent the rockshaft with the axis of the potentiometer shaft extending parallel to the rockshaft. A linkage structure includes a potentiometer arm connected to a rockshaft arm by a link such that the angle the potentiometer arm forms with the link is acute when the implement is in the transport position and obtuse when the implement is in the lowered field-working range. At the lowermost position of the implement, the link and potentiometer arm approach an overcenter position. The linkage structure provides amplified rotation of the potentiometer shaft relative to the rockshaft when the implement is in the field-working range of positions, while rotation of the shaft is reduced relative to rockshaft rotation when the implement is raised above the field-working position. In the preferred embodiment, rotation of the rockshaft 10.degree. in the field-working range results in rotation of over 30.degree. of the potentiometer shaft. Rotation of the rockshaft 10.degree. in the upper range of raised transport positions results in less than about 8.degree. of potentiometer shaft rotation. The amplified rotation in the field-working range significantly increases accuracy and repeatability of the feedback signal.

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Des Moines, IA, United States of America

William L Smith, Jr