Servo-control for an agricultural tractor hydraulic lift

Claim 2

A tractor hydraulic lift system for adjusting an associated implement and including a hydraulic actuator for raising, lowering and holding the implement, valve means movable from a neutral position to raise and lower positions for controlling the actuator, selectively settable manual means for operating the valve means, implement-responsive means for operating the valve means and servo means cooperative among the valve means, the implement responsive means and the manual means characterized in that the servo means includes a flexible element connected at opposite ends to the valve means and manual means for predetermined tensioning between the neutrally positioned valve means and a selected position of the manual means and engageable intermediate said ends by a movable guide of the implementresponsive means to vary said tensioning to move the valve means out of and back to its neutral position.

Claim 3

The invention defined in claim 1 in which the implement-responsive means is an element movable in response to implement position.

Claim 4

The invention defined in claim 1 in which the implement-responsive means is an element movable in response to variations in draft forces imposed between the implement and tractor.

Claim 5

The invention defined in claim 1 in which the implement-responsive means includes a first element movable in response to implement position and a second element responsive to variations in draft forces imposed between the implement and tractor, and selector means is provided for optionally selecting which element is to be effective in varying the tensioning in the flexible element.

Claim 6

The invention defined in claim 4 in which the selector means is further operative to cause both elements to be effective in varying the tensioning in the flexible element.

Claim 7

The invention defined in claim 1 further characterized in that the valve means includes first and second spaced apart valve members arranged in side-by-side parallel relationship, the first valve member being biased to open and the second valve member being biased to close an operating member spans and is pivotally connected at its opposite ends to the valve members, the members flexible member is connected at one end to a midportion of the operating member and at its other end to the settable means for predetermined tensioning to keep both valve members closed so that, upon relaxation of said tensioning by the implement-responsive means the first valve opens under influence by its bias and, upon increase of said tensioning by the implement-responsive means the second valve opens against its bias.

Claim 8

The invention defined in claim 6 in which said valve members are of the poppet type.

Claim 9

The invention defined in claim 6 including guide means about which the flexible element is trained to provide a bight portion in said element, and said implement-responsive means engaging said bight portion.

Claim 10

The invention defined in claim 1 including a second implement-responsive means also engageable with said element intermediate its ends to vary said tensioning to move the valve means out of and back to i neutral position.

Claim 11

The invention defined in claim 9 including selector means for conditioning either implement-responsive means to engage the element exclusively of the other implement-responsive means.

Claim 12

The invention defined in claim 10 in which the selector means is operative to condition both implement-responsive means for engagement with said element.

Claim 13

In a hydraulic lift for a tractor having a fore-and-aft body including a housing, a hitch system having a transverse lift rockshaft rockable in the housing, a hydraulic motor for rocking the rockshaft, motor-controlling valve means in the housing spaced from the rockshaft in a first direction and selectively settable means for the valve means spaced from the rockshaft in a second direction, the improvement residing in means interconnecting the valve means and the settable means, comprising a flexible element connected at one end to the valve means, and having a bight looped loosely around the rockshaft to extend away from the settable means and then toward and connected at its other end to the settable means, a plurality of guides engaging the bight to retain it free of the rockshaft, and one of said guides being movable in response to rocking of the rockshaft to engage the bight for varying the tension in the flexible element.

Claim 14

In a hydraulic lift for a tractor having a fore-and-aft body including a housing, a hitch system having a transverse lift rockshaft rockable in the housing, a hydraulic motor for rocking the rockshaft, motor-controlling valve means in the housing spaced from the rockshaft in a first direction and selectively settable means for the valve means spaced from the rockshaft in a second direction, the improvement residing in means interconnecting the valve means and the settable means, comprising a flexible element connected at one end to the valve means, and having a bight looped loosely around the rockshaft to extend away from the settable means and then toward and connected at its other end to the settable means, a plurality of guides engaging the bight to retain it free of the rockshaft, and one of said guides being movable in response to rocking of the rockshaft to engage the bight for varying the tension in the flexible element.

Claim 15

The invention defined in claim 12, in which the hitch system includes a part responsive to variations in draft forces and one of the guides is movable in response to draft forces imposed on the hitch to engage the bight for varying the tension in the flexible element.

Claim 16

The invention defined in claim 12 in which one of the guides is movable in response to rocking of the rockshaft to engage the bight for varying the tension in the flexible element, the hitch system includes a part responsive to variations in draft forces, and another of the guides is movable in response to draft forces imposed on the hitch to engage the bight for varying the tension in the flexible element.

Claim 17

The invention defined in claim 1 in which one of the guides is movable in response to rocking of the rockshaft to engage the bight for varying the tension in the flexible element, the hitch system includes a part responsive to variations in draft forces, and another of the guides is movable in response to draft forces imposed on the hitch to engage the bight for varying the tension in the flexible element, and selector means is operative to selectively disengage either the first or second guide from the bight of the flexible Element.

Claim 18

The invention defined in claim 15 in which the selector means is operative to engage both the first and second guides said bight.

Claim 19

The invention defined in claim 1 in which a pair of transversely spaced apart supports embrace the rockshaft and the guides are carried by and between the supports.

Claim 20

The invention defined in claim 17 in which the supports are provided with cooperative side-by-side slots and one of the guides is selectively movable in the slots.

Claim 21

The invention defined in claim 17 in which the supports are provided with a swingable arm and one of the guides is carried by the arm for movement therewith and means is provided for moving the arm.

Claim 22

The invention defined in claim 19 in which the means for moving the arm includes an element movable in response to rocking of the rockshaft.

Claim 23

The invention defined in claim 19 in which the tractor includes a hitch responsive to variations in draft forces and the means for moving the arm includes an element movable in response to movement of the hitch.