Ground opening device

Abstract

A ground opening device includes a ground-penetrating element configured to penetrate a ground surface, a down drive element configured to apply a downward force to the ground-penetrating element, a reaction force sensor configured to sense a ground reaction force in response to the action of the ground-penetrating element, and a controller configured to adjust the downward force on the ground-penetrating element in response to the sensed ground reaction force.

Description

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

FIG. 1 shows a schematic of a ground-opening device; and

FIG. 2 shows a schematic of a Force Control System; and

FIG. 3 shows a schematic of another Force Control System.

BEST MODES FOR CARRYING OUT THE INVENTION

FIG. 1 shows a side view of a typical non tillage seed drill opener generally indicated by arrow 1.

The basic elements of the seed drill opener (1) consist of a ground penetrating disc (2), one or more rigid ground penetrating side blades (3), an hydraulic ram (4) and a gauge wheel (5).

The seed drill opener (1) is attached to a rigid frame (6) that is attached to a tractor (not shown). The arms (7) and (8) are attached pivotally at points (9) at each end of the arms, one end of each arm to the rigid frame mounting plate (10) and the other end of each arm to the rigid frame (11) onto which the ground penetrating disc (2) is attached.

An hydraulic ram (4) attached to the lower pivoting arm (8) is used to exert a down force that causes the disc (2) and side blades (3) to penetrate beneath the surface (12) of the ground.

At a certain hydraulic pressure the hydraulic ram (4) will not only cause the disc (2) and side blades (3) to penetrate beneath the surface (12), but will also cause the gauge wheel (5) to press upon the ground surface (12).

The configuration of the gauge wheel (5) is such that it will not normally penetrate the ground but will press upon its surface (12).

The magnitude of the force exerted by the gauge wheel (on the ground surface) is equal and opposite to the up-thrust force (13) from the ground.

The magnitude of the up-thrust (13) is measured by a ground reaction force sensor (14) located in an appropriate component of the mounting bracket (15) for the gauge wheel (5). In the example shown in FIG. 1, the mounting bracket (15) also has an adjustable component (16) that facilitates alterations in depth of sowing by altering the position of the gauge wheel (5) relative to the position of the side blades (3) which are the devices that implant the seed and fertiliser in the soil.

The system will remain in equilibrium until the soil's resistance to penetration changes. This may occur due to a change in the composition of the soil, the compaction of the soil, or the moisture content of the soil. Other factors may also influence the resistance to penetration, such as the speed at which the disc is drawn through the soil.

Any change in soil resistance is first registered as a change in the magnitude of the up-thrust force (13) exerted by the soil on the gauge wheel (5) and recorded by the ground reaction force sensor (14).

Typically the ground reaction force sensor (14) includes one or more electronic strain gauges mounted on or in a metallic block that come under strain as the up-thrust (13) changes. The strain gauge produces a voltage proportional to the strain. This output is sent via cables to a controller (17) on the machine or tractor.

FIG. 2 shows a schematic outline of a typical force control system as used with the present invention. A continuous small sensitising voltage (18) is sent from a controller (17), typically located in the tractor cab, in order to sensitise the ground reaction force sensor (14). The sensitising voltage (18) is sent several times per second. The return signal voltage (19) from the ground reaction sensor (14) is a measure of the magnitude of strain (load) that the ground reaction force sensor (14) is experiencing at that particular point in time. The sensitising voltage (18) and return signal voltage (19) are transported from and to the controller (17) and the ground reaction force sensor (14) via insulated electrical cables.

The controller (17) averages and filters the electrical information received from the return signal voltage (19) several times per second. When the return signal voltage (19) differs (within pre-set sensitivity limits) from the pre-set values that the operator has set for the controller (17) for the field conditions in which the drill is operating, the controller (17) sends separate electrical control signals (20) via other electrical cables, to electro-hydraulic solenoids in a hydraulic controller (21) mounted on the tractor or on the drill.

The electro-hydraulic solenoids in the hydraulic controller (21) are able to draw “instant” oil under pressure (or alternatively return oil to) the tractor's internal hydraulic system or from a separate closed circuit hydraulic system operating remotely from the tractor.

The electro-hydraulic solenoids are opened and closed in order to increase or decrease the pressure of the hydraulic oil in the hydraulic ram (shown as 4 in FIG. 1) and thus increase or decrease the down force applied to the disc (shown as 2 in FIG. 1) and blades (shown as 3 in FIG. 1) that penetrate the soil, so as to return the up-thrust (shown as 13 in FIG. 1) to its pre-selected value as chosen by the operator.

Typically in a field situation, the up-thrust (13 in FIG. 1) is checked and the down force is reset if necessary approximately every metre of forward travel of the drill, although faster or slower sensitivity is also possible.

On larger machines multiple ground reaction force sensors (14) are positioned across a seed drill. A schematic of a typical force control system for multiple reaction force sensors (14) is shown in FIG. 3. A separate averaging device (22) blends and averages the signals from these multiple ground reaction force sensors (14) so that a single average return signal voltage (19) is sent to the controller (17) and processed substantially as described above. The frequency of load sensing in hydraulic control of the down force is adjustable at any time by the operator.

In rough ground conditions that might otherwise cause the return signal voltage (19) to change excessively, the sensitivity of the controller (17) can be decreased. Alternatively, the system may be deactivated altogether in rough ground conditions, stony soils and when the openers are carried clear of the ground for transport purposes.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Claims

1. A ground opening device which includes, a ground-penetrating element configured to penetrate a ground surface,a down drive element configured to apply a downward force to the ground-penetrating element,a reaction force sensor configured to sense a ground reaction force in response to the action of the ground-penetrating element,characterised in thatthe ground opening device includes a controller configured to adjust the downward force on the ground-penetrating element in response to the sensed ground reaction force.

2. The ground opening device of claim 1 wherein the ground opening device is a seed drill opener.

3. The ground opening device of claim 1 wherein the reaction force sensor senses the load on a gauge wheel.

4. The ground opening device of claim 1 wherein the reaction force sensor is an electronic strain gauge.

5. The ground opening device of claim 1 wherein the controller adjusts the downward force on the ground-penetrating element in response to the sensed ground reaction force such that the reaction force of the ground limiting device is kept substantially constant at a preset level.

6. A method of controlling a ground opening device having a ground-penetrating element, a down drive element, a ground reaction force sensor and a controller, characterised by the steps ofa) applying a downward force to the ground-penetrating element using the down drive element, andb) sensing a ground reaction force using the ground reaction force sensor; andc) using the controller to adjust the downward force of the ground-penetrating element in response to the sensed ground reaction force.