Depth control for farm implement

Claim 2

In a wheel-mounted implement frame adapted for mounting to a tractor, the latter having a hydraulic pump and a selector and adapted to provide hydraulic fluid under pressure to a respective first or second tractor hydraulic line in correspondence to movement of the selector to forward or reverse positions and to receive returning hydraulic fluid respectively through the second or first tractor hydraulic line, a control for automatically maintaining the height of a framemounted implement with respect to ground level comprising: a. a double-acting hydraulic cyliner operatively interconnecting the frame and frame wheels to raise and lower the frame with respect to the frame wheels; b. a control valve carried by the frame and in flow communication with the first and second tractor hydraulic lines, the valve communicating with the hydraulic cylinder through a pair of valve hydraulic lines and having a movable switch with raise and lower positions respectively communicating the hydraulic fluid in the first tractor hydraulic line through the valve with one or the other of the valve hydraulic lines to raise or lower the frame with respect to the wheels; c. a ground-sensing shoe movably mounted to the frame to permit vertical movement therebetween and having a lower, groundcontacting portion slidable across the surface of the ground and to move vertically with respect to the frame in response to variations in the height of the frame from the surface of the ground; d. motion-transmitting means for transmitting vertical movement of the sensing shoe to the valve switch to move the switch between its raise and lower positions; and e. a first bypass line communicating the second tractor hydraulic line through a check valve directly to the one valve hydraulic line, and a second bypass line communicating the othEr valve hydraulic line directly to the first tractor hydraulic line through a check valve, whereby movement of the selector to the reverse position causes hydraulic fluid to bypass the control valve and to energize the hydraulic cylinder, raising the frame with respect to the wheels.

Claim 3

The height control of claim 1 wherein the motion-transmitting means includes a resilient coupling adapted to absorb rapid upward and downward movements of the ground-sensing shoe as may be caused when the shoe encounters a rock or fissure.

Claim 4

The height control of claim 2 wherein the movable switch of the control valve has an intermediate position between raise and lower positions directly communicating the first and second tractor hydraulic lines and blocking flow through the valve hydraulic lines.

Claim 5

The height control of claim 2 wherein the motion-transmitting means includes upper and lower parallel links pivotally connecting the sensing shoe to the frame and adapted to maintain the shoe in flush orientation with respect to the ground surface.

Claim 6

The height control of claim 4 wherein the sensing shoe includes an upstanding shaft rotatively mounted within a sleeve pivotally coupled to the parallel connecting links to permit the shoe to rotate in a substantially horizontal plane so as to maintain orientation with the direction of travel of the implement frame when the frame is propelled by the tractor in a curved path.

Claim 7

The height control of claim 4 wherein one of the parallel links includes a motion-transmitting arm and wherein the valve switch includes a connector rod and a compression spring urging the connector rod into contact with the motion-transmitting arm, vertical movement of the sensing shoe being transmitted through the motion-transmitting arm and connecting rod to the valve switch, and the compression spring absorbing momentary movements of the motion-transmitting arm as may be caused by the sensing shoe encountering obstructions or fissures in the surface of the ground.

Claim 8

The height control of claim 6 wherein the control valve includes a plurality of facing cavities and wherein the valve switch comprises a plunger moving between opposed valve cavities to selectively communicate valve cavities with one another in response to position of the plunger.

Claim 9

The height control of claim 7 wherein the control valve includes a check valve preventing hydraulic fluid flow from the valve to the first tractor hydraulic line.

Claim 10

In a farm implement frame adapted for mounting to a tractor, the tractor having a hydraulic pump and a selector and adapted to provide hydraulic fluid under pressure to a first or a second tractor hydraulic line in correspondence to movement of the selector to forward or reverse positions, the returning hydraulic fluid passing through the second or first tractor hydraulic lines, respectively, a control for automatically maintaining the height of a frame mounted implement with respect to ground level comprising: a. wheels bearing the frame and swingable upwardly and downwardly with respect to the frame; b. a double-acting hydraulic cylinder coupling the wheels and frame and adapted to swing the wheels downwardly and upwardly to raise and lower the frame with respect to the wheels; c. a control valve mounted to the frame and in flow communication with the first and second tractor hydraulic lines, the valve communicating with the hydraulic cylinder through a pair of valve hydraulic lines and having a movable switch with raise and lower positions and an intermediate neutral position, the raise and lower positions respectively communicating the hydraulic fluid in the first hydraulic line through the valve with one or the other of the valve hydraulic lines to respectively raise or lower the frame with respect to the wheels, and the neutral position directly communicating the first and second tractor hydraulic lines through the valve; d. a ground height sensor including a vertically movable ground-sensing shoe adaptEd to slide across the surface of the ground and having an upstanding shaft, a sleeve in which the upstanding shaft of the shoe is rotatably mounted, upper and lower parallel links pivotally connecting the frame and the sleeve to maintain the shoe in flush orientation with respect to the ground, a motion-transmitting arm connected to a parallel link, a connector rod attached to the valve switch, and a compression spring resiliently coupling the connector rod to the motion-transmitting arm, the connector arm moving the valve switch between raise and lower positions in response to upward and downward movements of the ground-sensing shoe and the compression spring absorbing momentary movements of the sensing shoe as when the latter encounters obstructions or fissures in the ground surface; and e. a first hydraulic bypass line communicating the second hydraulic line directly to the one valve hydraulic line through a check valve and a second hydraulic bypass line communicating the other valve hydraulic line directly to the first tractor hydraulic line through a check valve, whereby movement of the selector to the reverse position causes hydraulic fluid to bypass the control valve and to energize the hydraulic cylinder, raising the implement frame with respect to the wheels.

Claim 11

In a farm implement frame adapted for mounting to a tractor, the tractor having a hydraulic pump and a selector and adapted to provide hydraulic fluid under pressure to a first or a second tractor hydraulic line in correspondence to movement of the selector to forward or reverse positions, the returning hydraulic fluid passing through the second or first tractor hydraulic lines, respectively, a control for automatically maintaining the height of a frame mounted implement with respect to ground level comprising: a. wheels bearing the frame and swingable upwardly and downwardly with respect to the frame; b. a double-acting hydraulic cylinder coupling the wheels and frame and adapted to swing the wheels downwardly and upwardly to raise and lower the frame with respect to the wheels; c. a control valve mounted to the frame and in flow communication with the first and second tractor hydraulic lines, the valve communicating with the hydraulic cylinder through a pair of valve hydraulic lines and having a movable switch with raise and lower positions and an intermediate neutral position, the raise and lower positions respectively communicating the hydraulic fluid in the first hydraulic line through the valve with one or the other of the valve hydraulic lines to respectively raise or lower the frame with respect to the wheels, and the neutral position directly communicating the first and second tractor hydraulic lines through the valve; d. a ground height sensor including a vertically movable ground-sensing shoe adaptEd to slide across the surface of the ground and having an upstanding shaft, a sleeve in which the upstanding shaft of the shoe is rotatably mounted, upper and lower parallel links pivotally connecting the frame and the sleeve to maintain the shoe in flush orientation with respect to the ground, a motion-transmitting arm connected to a parallel link, a connector rod attached to the valve switch, and a compression spring resiliently coupling the connector rod to the motion-transmitting arm, the connector arm moving the valve switch between raise and lower positions in response to upward and downward movements of the ground-sensing shoe and the compression spring absorbing momentary movements of the sensing shoe as when the latter encounters obstructions or fissures in the ground surface; and e. a first hydraulic bypass line communicating the second hydraulic line directly to the one valve hydraulic line through a check valve and a second hydraulic bypass line communicating the other valve hydraulic line directly to the first tractor hydraulic line through a check valve, whereby movement of the selector to the reverse position causes hydraulic fluid to bypass the control valve and to energize the hydraulic cylinder, raising the implement frame with respect to the wheels.