Abstract: The hydraulic circuit of the present invention allows flotation of the header without extensive use of accumulators and is readily adaptable to present open center hydraulic systems. The present invention is also adaptable to closed center hydraulic systems with or without flow compensation. The hydraulic system has a pump selectively connected with the header cylinder. Pressure within the header cylinders is automatically maintained at a constant level by fluid addition to the cylinder or by extracting fluid from the cylinders.

Abstract: A unit for raising and lowering an agricultural implement, which unit is connected to a tractor. The unit includes an attachment device (6) for attaching the implement to the tractor, a raising and lowering device (2, 5) for raising and lowering the implement, and a control and regulation device including a linkage and regulation device including a linkage system and an operating lever (27) disposed between the attachment device (6) and the raising and lowering device (2, 5). The unit further includes a flexure bar (7) and is controlled by two control levers (36 and 38) which act on the operating lever (27) to determine the furrow depth and maximum force acceptable by the bar (7).

Abstract: An agricultural tractor having six wheels which are each hydraulically drivable by individual hydraulic motors through hydraulic fluid supplied by respective hydraulic pumps. With each pump driving only one wheel, skidding of a wheel does not affect drive to other wheels. The pumps are all driven by a single engine. Selectively operable automatic control means control the speed of the wheels when, for example, the tractor is turning. Control means are also responsive to the drag resistance of an implement hitched to the tractor's lifting members and cause such lifting members to raise when the implement's resistance exceeds a predetermined limit. In addition, speed of the vehicle is automatically reduced by reason of such resistance and, further, the position of the implement relative to the ground may be adjusted to offset at the location of the implement upward and downward movement of tandem wheel pairs at the rear of the tractor.

Abstract: An apparatus for a tractor having a rear and front implement attachment mechanism. Each such mechanism has a hydraulic power lift which acts on it. The power lifts have in common a regulator and control device with a changeover valve. By activating this changeover valve, selectively one of the power lifts can be regulated in conformity with the provided adjustment features, such as the actual values of the position, of the cylinder pressure, etc., while at the same time the other power lift is connected with a control member for random influence of this last-mentioned power lift.

Abstract: A tractor includes a hitch for pulling a ground-engaging implement. A hydraulic cylinder is extendable and retractable to lower and raise the implement. A control system senses operating parameters, including wheel slip, engine speed, draft force and implement or rackshaft position. Error signals derived from the sensed wheel slip, engine speed and draft force are combined into a composite or combined error signal. The larger of the combined error signal, or a separately determined position error signal, is selected and converted to a pulsewidth modulated valve control signal which is applied to a control valve which then actuates the cylinder to move the implement to reduce the magnitude of the selected error signal.

Abstract: A conventional non-electrical draft/position responsive hitch control system is modified to respond to an electrical control signal derived from sensed engine droop and wheel slip.

Abstract: A draft control system of the type in which a mechanical spring is employed to balance the draft forces of an implement trailed behind the tractor so as to correct the working depth of the implement in accordance with changes in draft forces, in which the feature is the use of a hydraulic force-amplifying device to increase the responsiveness of the system so as to minimize the forces required to effectuate regulation of the working depth of the implement.

Abstract: A control system for a tractor hydraulical power lift system having an electrohydraulic actuator (22) coupled to a main hydraulic valve (21), comprising a feedback electronic control circuit including a circuit for mathematically combining a plurality of transducer generated signals into a command signal. The command signal comprises the output signal of a first differential summing device (32) receiving a first input signal for a control handle transducer (24) from which is substracted a second input signal produced as the output of a signal mixer that combines input signals from a rockshaft transducer (25), a draft selector transducer (26) and a draft load transducer (27). The command signal and a signal from a transducer (28) coupled to the electrohydraulic actuator are fed into a differential summing device (49) that has as its output an error signal representing the actual and desired positions of an implement to be positioned by the power lift system.

Abstract: This lower link for a three-bar hitch provides a practical way to determine the tension force present in a lower link independent of any bending or other loadings. The link is formed of two bars which are bent out from each other to an intermediate point and then converge together forming a diamond-shaped opening between the bars and the distance between the intermediate points on the bars is measured by a length measuring device; the length being translatable into the tension force on the link.

Abstract: The tractor vehicle comprises a chassis supported by at least two sets of driving and steering wheels. A cab is fixed to the chassis and encloses the devices for driving the vehicle and the devices controlling tools coupled to the power take-off of the vehicle. The two sets of driving and steering wheels are driven in pairs located on the same side of the chassis by an independent drive. The two drives are interconnected by variator-inverter devices which act selectively on either of the two drives or on both thereof in a symmetrical or unsymmetrical manner. The vehicle may be employed not only in the agricultural field but in any other application such as public works.

Abstract: A tractor draft load monitoring system responsive to tractor and associated implement load changes. The system is particularly adapted for a tractor having an engine/transmission power unit coupled to its drive shaft. The power unit is mounted on the frame by resilient mounts that permit measurable angular displacement of the power unit relative to the frame about the drive shaft axis in reaction to changes in the drive shaft torque. The working depth of the implement, which may be tractor mounted, semi-mounted or a pull type implement, is raised or lowered by a hydraulic lift system that is controlled by a control valve assembly connected to a source of fluid under pressure.

Abstract: A control for the hydraulic power lift of a tractor, particularly one used in agriculture. The control includes a pre-control slide valve which is adjustable not only by the pick-up or indicator of the working resistance or the position of a working implement but also by a rated or desired value pick-up, by way of a control linkage, to the control positions "lift", "neutral", and "lower". A first spring which urges the pre-control slide valve toward the lifting position, engages the control linkage to transmit the values of the working resistance. The force of this spring is greater than the force of the spring which continuously urges the pre-control slide valve towards the lowering position. The pick-up or indicator for the working resistance of the working implement is linked to the control linkage, against the force of the first spring, by way of a rod having a slotted hole.

Abstract: A control system is provided for a hydraulically operated tractor hitch assembly including a rockshaft operated by a main cylinder which is controlled through a spool valve operated by a pilot cylinder which is controlled, in turn, through a solenoid operated pilot valve. The pilot valve is controlled in response to a command signal and first and second feedback signals which correspond to the position of the rockshaft and to the position of the spool valve member. The velocity of the downward movement is limited by limiting the amplitude of a first error signal which is developed by a first comparator responsive to the command and first feedback signals with the first error signal and the second feedback signal being applied to a second comparator. Such velocity-limiting operations are controlled through a manually operated switch or by a motion sense circuit responsive to the rate of change of the command signal.

Abstract: A control system is provided for a hydraulically operated tractor hitch assembly including a rockshaft operated by a main cylinder which is controlled through a spool valve operated by a pilot cylinder which is controlled, in turn, through a solenoid operated pilot valve. The pilot valve is selectively controlled from first and second detector circuits through a gating circuit which is controlled by a third detector circuit which responds to a first error signal developed by comparing a command signal which corresponds to a rockshaft target position and a first feedback signal which corresponds to the actual rockshaft position and which is generated by a potentiometer connected to the rockshaft.

Abstract: An improved draft and position control system for a tractor. Independent manually operable draft and position controls are provided for establishing a desired draft and/or position of an implement drawn by a tractor. The position control establishes the maximum lowered position to which the implement may descend and will override any draft signals which would tend to lower the implement beyond this point. The draft control includes the draft responsive member interconnected with a feedback mechanism which will tend to maintain the desired draft on the implement. An additional position feedback is provided which can moderate the draft feedback to prevent undue response of the implement during changes of the draft load. In accordance with the principles of this invention the position feedback which moderates the draft feedback can be infinitely varied between a first setting wherein it fails to moderate to a second setting where it substantially moderates.

Abstract: A subassembly for use in a position in draft control linkage for operation by cables connected to position and draft control levers. The subassembly includes a mechanical hydraulic valve operating linkage and a position and draft load and sensing linkage sensing position draft and load of the hitch on a tractor. The subassembly is removably mounted as a unit on the vehicle chassis and can be adjusted prior to positioning on the tractor.

Abstract: Hydraulic control system including a bypass provided in an intermediate portion of an oil passage extending from a position control valve to a hydraulic actuator for raising and lowering a working implement. A draft control valve disposed in the bypass controls the pressure of oil flowing into the bypass, in response to the displacement of a member for sensing the draft force of the working implement.

Abstract: Adjustable mixed automatic height and draft control apparatus for a tractor power lift mechanism includes a height control rocker actuated by the tractor's rockshaft, a draft control rocker actuated by the tractor's hitch linkage, and a first balance lever moveable relative to either one of the rockers by movement of the other. A control linkage has its point of connection to the first balance lever variable by a first hand lever to adjust the mixture of height and draft control, a second hand lever gives over-riding manual control of the power lift mechanism, and a second balance lever is moveable relative to either one of the control linkage and the other hand lever by movement of the second. The second balance lever actuates the control valve of the power lift mechanism.

Abstract: An electronic control system for controlling the depth of a vehicle drawn implement as a function of a plurality of sensed variables including a plurality of transducers one for sensing the value of each of the variables, and an electronic control circuit for initially generating a pulsating signal having a characteristic which varies in accordance with and is representative of the value of each variable, for converting that variable to a variable amplitude signal, for algebraically adding the various signals and for producing a control signal to operate an electrically operated valve in response to the polarity and amplitude of the signal to selectively raise and lower the implement to the desired depth.

Abstract: The control system is provided with a detector that detects whether the ripper is operated in a piercing operating mode or a digging operating mode. In the piercing operating mode the angle of the shank is adjusted to a preset piercing angle, while in the digging operating mode the shank angle is adjusted to a preset digging angle thereby effecting optimum piercing and digging operations. Limit switches for detecting upper and lower limit positions of the shank are provided for raising and lowering the shank between these limit positions while adjusting the shank angle. Further an overload detector is provided for raising the shank when its load exceeds a predetermined load and lowering the shank when the load decreases below it. A manual preference control device also provided for enabling manual control during automatic control.

Abstract: The lower draft link of a tractor three-point hitch includes a sensor to sense draft loads imposed on the draft link by an earth-working implement. Variations in the draft load cause variations in the pressure of the fluid in the sensor from a preselected pressure. A pilot-operated, load control valve is connected to the sensor and is shiftable in response to pressure above and below the preselected pressure to actuate a control mechanism. The control mechanism actuates a direction control valve for directing fluid to and from a hydraulic lift cylinder for respectively raising and lowering the draft link to adjust the implement so as to maintain the preselected pressure and thus maintain the desired draft load.

Abstract: A seed drill for a field left in stubble, comprising a plurality of pairs of discs wherein each pair includes a forward coulter disc tangentially engaging a rearward furrow opening disc held by clevis members to a wheel supported framework. Seeds are directed between the disc pairs to fall therebetween to a point of convergence between the two discs. Forward rotation of the discs cause the seeds to be separated and evenly spaced apart as the seed drill is moved along a forward path of travel. A hydraulic system is provided wherein the pairs of discs are forced downwardy by ram cylinders connected between each clevis member and the framework. The ram cylinders are connected in a parallel hudraulic circuit to a pressure supply source so an even amount of downward pressure is applied to each of the disc pairs.

Abstract: An automatic control system for a ripper used on a construction equipment in which a load detector is provided on the ripper for detecting load acting on the ripper shank and lift cylinders are actuated to automatically raise the shank when overload is applied to the shank during ripping operation. The ripper is also provided with a depth detector for detecting upper and lower limit positions of the shank and the vertical movement of the shank can be limited between the upper and lower limits. When no overload is applied, the shank is maintained at the lower limit position to rip the ground at a predetermined penetration depth.

Abstract: A hydrostatic drive tractor having a hydraulically lowerable and raisable hitch to lower and raise an associated implement to respectively increase or decrease draft load includes a draft control system sensing increases and decreases in the hydrostatic drive pressure which are proportional to draft load as sensed by the drive wheels to activate valving to respectively raise and lower the hitch.

Abstract: A sensor for measuring the load exerted on a member includes two spaced apart, aligned stationary capacitor plates and a movable capacitor plate disposed intermediate the two stationary plates and spaced therefrom to form two air dielectric capacitors. The stationary plates are attached at one point to the member and the movable plate is connected by a shaft to a second point. Loading the member causes elastic deformation between the first and second points which causes the movable plate to move relative to the stationary plates. This relative movement causes differential changes in capacitance in the two capacitors which are detected and conditioned to form a usable control signal.

Abstract: A control valve that forms part of a draft control system is disclosed herein. The control valve is designed to raise the implement with respect to the vehicle at one rate of speed and automatically increase the rate of raising the implement when a predetermined magnitude of change of position is required.

Abstract: The sensing system disclosed herein is adapted to control the position and/or draft of an implement connected to a vehicle through draft arms that are positioned by a rock shaft. The setting of the rock shaft is accomplished by a hydraulic motor having fluid supplied thereto by a control valve and the desired setting is made by a manual control lever. The control lever, rock shaft and draft arms have sensing devices associated therewith, each of which includes a variable inductance coil fixed on the vehicle and a plunger movable with respect to the coil. Each sensing device has a continuous output which is the function of the position of the member associated therewith.

Abstract: The lower draft link of a tractor three-point hitch includes a sensor to sense draft loads imposed on the draft link by an earth-working implement. Variations in the draft load cause variations in the pressure of the fluid in the sensor from a preselected pressure. A pilot-operated, load control valve is connected to the sensor and is shiftable in response to pressure above and below the preselected pressure to actuate a control mechanism. The control mechanism actuates a direction control valve for directing fluid to and from a hydraulic lift cylinder for respectively raising and lowering the draft link to adjust the implement so as to maintain the preselected pressure and thus maintain the desired draft load.