Draft and position control for tractor drawn implements

Claim 2

A control for an agricultural tractor hitch adapted to hitch a ground working implement to the tractor comprising: a. a hitch linkage extending trailingly from the tractor and movable in a generally vertical longitudinal plane; b. a power cylinder for raising and lowering the hitch linkage; c. a valve controlling the power cylinder having a valve member with a closed center equilibrium position shutting off fluid flow to or from the power cylinder when the hitch linkage is properly positioned to establish for an attached implement either a given working depth or desired draft response; d. a valve actuating linkage including a yoke means having separate arms, one arm receiving draft and the other arm position command signals, said valve actuating linkage being responsive to movement of said arms for shifting the valve from its closed center equilibrium position establishing the preset depth or draft conditions of the implement and said one arm also receiving draft and the other arm also receiving position feedback signals transmitted by movement of the hitch linkage, said valve actuating linkage being also responsive to said hitch linkage movement for restoring the valve to the closed center equilibrium position and including e. a single link element selectively engageable with each of the arms and connected to the valve member such that the single link element is responsive to both command and feedback signals along a line of movement common to each arm, said link element being movable longitudinally in said line of movement in response to movement of either arm for coordinating the command and feedback signals and thereby position said valve in accordance with the preset depth or draft requirements.

Claim 3

A control according to claim 1 wherein said single link element includes a plate element secured to said single link element and engageable by either of said arms in a plane transversely of the said common line of movement, the position of which plate element is established either by the draft Or position command limits of either of said arms, whichever is greater, and a spring yieldably resisting movement of said valve from its closed center equilibrium position in a direction tending to supply fluid to said power cylinder raising the hitch linkage while said link element is restrained from movement in the opposite direction by said plate element.

Claim 4

A control according to claim 1 wherein said valve comprises: a. a valve body having an axial bore open at one end; b. a valve spool reciprocated in said bore for movement in either direction from the closed center equilibrium position; c. said single link element extending into the open end of said bore and being secured to the valve spool; d. said yoke means comprising a pair of spaced arms extending parallel to each other on opposite sides of said single link element, one arm being actuated in response to position command and feedback signals and the other to draft command and feedback signals; and e. a plate element carried on said single link element engageable with each arm on a line transversely intermediate the ends thereof and passing through said common line of movement of said single link element.

Claim 5

A control according to claim 3 wherein a housing is provided combining said valve body with an enclosure for said actuating linkage, said actuating linkage comprising: a. a transverse shaft journaled in said wall portions and extending beyond one side of the enclosure; b. a sleeve rotatably received in one wall portion circumjacent said shaft; c. a pair of manual control levers, one affixed to the shaft and the other to the sleeve; d. a pair of connecting rods, one affixed to the shaft and the other rotatable on the shaft and affixed to the sleeve and each being connected to an end of one of said arms for transmitting position and draft command signals thereto; and e. a pair of push rods reciprocated in response to hitch linkage movement, each connected to the other end of one of said arms for transmitting position and draft feedback signals thereto.

Claim 6

A control according to claim 4 wherein said valve spool comprises: a. a first land portion reciprocated in said bore for controlling a fluid supply passage to the power cylinder; b. a second land portion reciprocated in said bore for controlling a primary fluid exhaust passage from said power cylinder; c. a third land portion reciprocated in said bore for controlling a secondary fluid exhaust passage and positioned relative to said second land portion wherein return fluid flow through said primary exhaust passage is shut off by movement of the valve spool prior to said third land portion shutting off said secondary exhaust passage; d. other passage means bypassing said second land portion permitting fluid return through said secondary exhaust passage when the primary exhaust passage is closed; and e. flow restriction means in said secondary passage for restricting the flow return and damping the final descent rate of said hitch linkage until said valve spool is returned completely to the closed center position.

Claim 7

In an agricultural tractor, the combination of a three-point implement hitch for hitching a ground-working implement to the tractor and a servo control for moving the hitch upwardly and downwardly, the hitch including a pair of trailingly extending lower struts and a single upper strut, the implement having a mast structure adapted to couple with said struts and being raised and lowered thereby relative to the tractor frame into and out of engagement with the ground and also being raised and lowered as it encounters varying working conditions of the soil, and a fluid operated power cylinder for raising and lowering said hitch, said servo control comprising: a. a valve controlling the power cylinder including a valve spool having a closed center equilibrium position shutting off fluid flow to or from the power cylinder when the implement position or draft Is in accordance with a given servo controlled setting; b. a valve actuating linkage including a pair of parallel arms extending transversely to the axis of the valve spool; c. a position responsive command and position sensing feedback linkage system pivotally connected to respective ends of one arm; d. a draft responsive command and draft sensing feedback linkage system pivotally connected to respective ends of the other arm, each said system having command signals imparted manually to establish said given servo controlled setting and being connected to the hitch to receive position and draft sensing feedback signals; and e. a single link element extending between said arms and being engageable by either arm on a line midway between their respective ends and said link element being secured to said valve spool so as to differentially shift said valve spool in response to either the position or draft command or feedback signals.

Claim 8

In an agricultural tractor, the combination of a three-point implement hitch for hitching a ground-working implement to the tractor and a servo control for moving the hitch upwardly and downwardly, the hitch including a pair of trailingly extending lower struts and a single upper strut, the implement having a mast structure adapted to couple with said struts and being raised and lowered thereby relative to the tractor frame into and out of engagement with the ground and also being raised and lowered as it encounters varying working conditions of the soil, and a fluid operated power cylinder for raising and lowering said hitch, said servo control comprising: a. a valve controlling the power cylinder including a valve spool having a closed center equilibrium position shutting off fluid flow to or from the power cylinder when the implement position or draft Is in accordance with a given servo controlled setting; b. a valve actuating linkage including a pair of parallel arms extending transversely to the axis of the valve spool; c. a position responsive command and position sensing feedback linkage system pivotally connected to respective ends of one arm; d. a draft responsive command and draft sensing feedback linkage system pivotally connected to respective ends of the other arm, each said system having command signals imparted manually to establish said given servo controlled setting and being connected to the hitch to receive position and draft sensing feedback signals; and e. a single link element extending between said arms and being engageable by either arm on a line midway between their respective ends and said link element being secured to said valve spool so as to differentially shift said valve spool in response to either the position or draft command or feedback signals.

Claim 9

In an agricultural tractor according to claim 6 wherein said draft responsive command and feedback linkage system comprises: a. a link connected to the hitch to sense draft forces for transmitting the feedback signal to the valve actuating linkage; b. a draft spring compressible by movement of the link in response to said draft forces and to return the link; and c. adjustable connection means for the link to vary the draft feedback amplification sensed by the valve actuating linkage.

Claim 10

In an agricultural tractor according to claim 7, wherein the adjustable connection means is between the link and the valve actuating linkage so as to provide adjustable amplification of the draft feedback signal.

Claim 11

A control for use with a tractor implement hitch adapted to be raised and lowered by means of a power cylinder, said control comprising: a. a valve including a valve spool having a closed center equilibrium position for shutting off fluid flow to or from the power cylinder when the implement position or draft load on the implement is in accordance with a given position or draft control signal; b. a valve actuating linkage including a differential mechanism coordinating position and draft control signals and transmitting said control signals to the valve spool, said control signals being either position responsive command and feedback signals transmitted by the differential mechanism to the valve spool or draft responsive command and feedback signals transmitted by the differential mechanism to the valve spool, whichever is of greater magnitude; c. a single link element interconnecting the differential mechanism and valve spool for transmitting the command and feedback signals to the valve spool whereby said valve spool is shifted in response to either the position or draft command or feedback signals in accordance with the present position or draft requirements; d. a pair of parallel arms extending transversely to the axis of the valve spool, said position responsive command and feedback signals being received by the respective ends of one arm and said draft responsive command and feedback signals being received by the respective ends of the other arm; e. said single link element being floatingly supported jointly between said arms intermediate their respective ends and in engagement with one of the arms; and, f. biasing means maintaining said link element in engagement with at least one of the arms.

Claim 12

A control for use with a tractor implement hitch adapted to be raised and lowered by means of a power cylinder, said control comprising: a. a valve including a valve spool having a closed center equilibrium position for shutting off fluid flow to or from the power cylinder when the implement position or draft load on the implement is in accordance with a given position or draft control signal; b. a valve actuating linkage including a differential mechanism coordinating position and draft control signals and transmitting said control signals to the valve spool, said control signals being either position responsive command and feedback signals transmitted by the differential mechanism to the valve spool or draft responsive command and feedback signals transmitted by the differential mechanism to the valve spool, whichever is of greater magnitude; c. a single link element interconnecting the differential mechanism and valve spool for transmitting the command and feedback signals to the valve spool whereby said valve spool is shifted in response to either the position or draft command or feedback signals in accordance with the present position or draft requirements; d. a pair of parallel arms extending transversely to the axis of the valve spool, said position responsive command and feedback signals being received by the respective ends of one arm and said draft responsive command and feedback signals being received by the respective ends of the other arm; e. said single link element being floatingly supported jointly between said arms intermediate their respective ends and in engagement with one of the arms; and, f. biasing means maintaining said link element in engagement with at least one of the arms.

Claim 13

The control of claim 9 wherein the biasing means is a spring yieldably holding said single link element in engagement with one of said arms.