Actuator for setting seed depth for a row unit on a planter
An agricultural planter row unit has a trench opener fixed to a support frame and a gauge wheel supported by a gauge wheel arm to control planting depth. An electric actuator drives movement of a linkage with a mechanical stop that bears against the gauge wheel support arm to position the gauge wheel to obtain the desired planting depth. A seed depth control system receives an operator input, from an operator compartment of a towing vehicle, and automatically controls actuation of the seed depth actuator.
1 . A row unit on a planting machine, comprising:
a support frame;
a trench opener;
a gauge wheel;
a gauge wheel arm operably coupling the gauge wheel to the support frame; and
a planting depth actuator assembly including,
a linkage operably coupled to the gauge wheel arm to limit a range of motion of the gauge wheel arm,
a screw member operably coupled to the linkage, the screw member having a threaded portion, and wherein the screw member has a longitudinal axis and is configured to move axially along the longitudinal axis to drive the linkage without rotating about the longitudinal axis,
a motor operably coupled to the screw member through a plurality of gears providing a mechanical advantage sufficient to prevent rotation of the motor when the motor is not energized to lock an axial position of the screw member, wherein energization of the motor causes the screw member to move axially.
2 . The row unit of claim 1 and further comprising a shank movably mounting the gauge wheel arm to the support frame, and wherein the planting depth actuator assembly includes an actuator body mounted to the shank and containing the screw member.
3 . The row unit of claim 2 wherein the screw member includes a slot configured to engage a key that is mounted relative to the actuator body to inhibit rotation of the screw member.
4 . The row unit of claim 2 , wherein the linkage is pivotally mounted to the shank.
5 . The row unit of claim 1 and further comprising a load cell operably interposed between the linkage and a mechanical stop in contact with the gauge wheel arm.
6 . The row unit of claim 1 , wherein the motor is a brushless DC electrical smart motor having a rotary encoder to sense output shaft position of the brushless DC electrical smart motor.
7 . The row unit of claim 1 , wherein the motor is configured to communicate digitally on a communication bus.
8 . The row unit of claim 7 , wherein the communication bus is a Controller Area Network (CAN) bus.
9 . The row unit of claim 1 , wherein the plurality of gears is disposed within the actuator body.
10 . The row unit of claim 9 , wherein the plurality of gears includes a gear having a threaded surface engaged with the threaded portion of the screw member such that rotation of the gear causes axial movement of the screw member.
11 . The row unit of claim 10 and further comprising a thrust bearing disposed between a face of the gear and the actuator body, the thrust bearing being configured to transfer axial loads from the screw member to the actuator body.
12 . The row unit of claim 1 , wherein the plurality of gears provides a ratio of at least about 32:1.
13 . A planting machine, comprising:
a tow bar; and
a plurality of row units coupled to the tow bar, each row unit comprising:
a support frame;
a double disk opener;
a gauge wheel;
a gauge wheel arm that couples the gauge wheel to the support frame; and
an automatic planting depth actuator assembly including,
a linkage operably coupled to the gauge wheel arm to limit a range of motion of the gauge wheel arm,
a screw member operably coupled to the linkage, the screw member having a threaded portion, and wherein the screw member has a longitudinal axis and is configured to move axially along the longitudinal axis to drive the linkage without rotating about the longitudinal axis, and
a motor operably coupled to the screw member through a plurality of gears providing a mechanical advantage sufficient to prevent rotation of the motor when the motor is not energized to lock an axial position of the screw member, wherein energization of the motor causes the screw member to move axially to adjust a position of the gauge wheel relative to the double disk opener.
14 . The planting machine of claim 13 , wherein the automatic planting depth actuator assembly further comprises a load cell operably interposed between the linkage and a mechanical stop in contact with the gauge wheel arm.
15 . The planting machine of claim 14 , and further comprising a control system operably coupled to the motor and the load cell, the control system being configured to generate a planting depth actuation signal to the automatic planting depth actuator based on a target planting depth.
16 . The planting machine of claim 15 , wherein the motor is a smart motor and is configured to communicate on a digital communication bus.
17 . The planting machine of claim 16 , wherein the motor is configured to provide an indication of motor torque and motor position to the control system.
18 . A method of calibrating an automatic planting depth control system of row unit on a planting machine, the method comprising:
causing an electric motor, coupled to a screw member, to fully retract the screw member to a motion limit;
lowering the row unit onto a flat surface;
causing the electric motor to advance the screw member until contact with a gauge wheel arm of the row unit is detected while monitoring revolutions of the electric motor;
saving the number of revolutions of the electric motor as a zero-depth position of the automatic planting depth control system; and
employing the zero-depth saved position during operation of the automatic planting depth control system to control depth of the row unit.
19 . The method of claim 18 , wherein the electric motor is a smart motor and detection of at least one of the motion limit and contact with the gauge wheel arm is done by sensing torque of the electric smart motor.
20 . The method of claim 18 , wherein the electric motor is a smart motor and detection of at least one of the motion limits is done by sensing torque of the electric smart motor and contact with the gauge wheel arm is detected by sensing a load through a load cell on the linkage between the actuator and gauge wheel arm.