GROUND ATTITUDE CONTROL MEANS

Abstract: Means to enable an elongate boom (1) to maintain a constant attitude with respect to the ground, e.g. the boom of an agricultural spray apparatus comprising a carrier (12) on which the boom (1) is pivotally mounted for movement about a substantially horizontal axis (P1), a levelling member (3) pivotally mounted on the boom for movement about a substantially horizontal axis (P2) and linkage means (6) pivotally connected between the levelling member (3) and the carrier (12), the pivotal connections being disposed to cause the boom (1) to rotate at a desired angular velocity in response to rotation of the carrier (12).

Description: TITLE: GROUND ATTITUDE CONTROL MEANS DESCRIPTION TECHNICAL FIELD This invention relates to a ground attitude control means more particularly, but not exclusively, for use in agricultural crop-spraying equipment. BACKGROUND ART It is common practice to apply chemicals to a growing crop, for instance to help control pests, fungi or weeds. Ground-based crop-spraying equipment commonly comprises a vehicle-carried body, e.g. a tractor-carried body, having an elongate framework or boom which extends laterally from the body and which supports nozzles which apply a spray mist of chemical/water mixture to the crop and its surroundings. Such a boom is often used to cover a working width of between 12 and 30 metres to minimise the number of passes required to cover a given area of land. The requirement for such an elongate boom causes the designer of crop-spraying equipment many problems in dealing with the stresses imposed on the boom and its supporting framework and on the carrying vehicle. There is also the problem of maintaining a distance between the boom and the ground (or growing crop) whilst the carrying vehicle is travelling over uneven ground. Prior types of equipment have attempted to resolve the problems using various mechanisms. Previous designs are known which use a single pivotal connection between a carrying frame supported on the carrying vehicle and the boom which allows the boom to swing in the manner of a pendulum independently of the carrying frame. With this type of design it is possible for conditions to occur which cause the boom to swing uncontrollably and it is common practice to add springs and shock-absorbers between the carrying frame and the boom to afford some degree of control. This has the effect of tending to make the boom attempt to follow the movements of the carrying frame on the one hand and attempt to follow the horizon on the other hand. The resultant compromise angle is not always desirable. The addition of springs and shock-absorbers is beneficial in that the boom tends to follow the angle of the carrying frame (rather than following the horizon) when operating on a side-incline (or when the vehicle's wheels on one side are in a deeper rut than on the other side) but also causes an unwanted effect when conditions occur which require the boom to be set at an angle differing to that of the carrying frame. This can commonly occur, for example, when the suspension of the carrying vehicle or frame tends to cause the boom to favour the horizontal rather than following the angle of its wheels. An alternative known method adds a levelling bar to the above pendulum mechanism to allow the neutral pendulum point (that is where the springs on both sides of the pendulum pivot apply an equal force) to be biased to one side or the other. This allows the machine operator (or an automatic mechanism) to reset the correct distance between boom and ground for the duration of the aforesaid conditions. This mechanism commonly takes the form of a rocker bar pivoted on the carrying frame, the springs being attached to this bar rather than to the carrying frame. The present invention seeks to provide means to enable the boom more closely to follow the contours of the ground by at least partially isolating the boom from the movements of the carrying vehicle. An object of the invention is to seek better to isolate the boom from movements of the carrying frame while retaining the beneficial effects of the boom tending to follow the angle of the carrying frame and also retaining the ability to bias the neutral pendulum point. DISCLOSURE OF THE INVENTION The invention is ground attitude control means to enable a member, e.g. an elongate boom, to maintain a constant attitude with respect to a datum, e.g. the ground, comprising a carrier on which the boom is pivotally mounted for movement about a substantially horizontal axis, a levelling member pivotally mounted on the boom for movement about a substantially horizontal axis and linkage means pivotally connected between the levelling member and the carrier, the pivotal connections being disposed to cause the boom to rotate at a lower or higher angular velocity than the carrier in response to rotation of the carrier. Preferably one or more springs and/or shock absorbers or dampers will be connected between the boom and the levelling member. The linkage may be in the form of a length adjustable member, e.g. an hydraulic cylinder. The position at which the linkage is pivoted on the carrier may be adjustable longitudinally of the boom to vary the effect of the control means. The member to be attitude controlled may be an agricultural spray boom having spray nozzles. Thus in one aspect the present invention provides an agricultural implement having an elongate boom supporting spray nozzles for applying chemicals to a soil surface or growing crop the attitude of the spray boom being controlled by control means as described above. The pivoting of the levelling member on the boom rather than on the carrying frame, and suitably positioning the levelling member/carrier linkage, results in the production of the desired advantageous geometrical effect. The effect may be enhanced by attaching the shock absorbers between the levelling member and the boom rather than between the carrier and the boom as is conventional. Thus by suitably adjusting the position of the linkage between levelling member and the carrier, the damping effort of the shock absorbers can be altered without changing the shock absorbers themselves. As the carrier rotates due to rocking of the vehicle, the boom tends to maintain its rotational position due to its own inertia, the shock absorbers and springs (and the fact that the levelling member is pivotally attached to the boom) tend to cause the levelling member to copy the rotational position of the boom but the levelling member is linked to the carrier and so is forced to rotate or contra- rotate relative to the carrier. Thus the springs and shock absorbers cause the boom to rotate or contra-rotate relative to the carrier which tends to neutralise or enhance the effect on the boom of the initial rotational movement of the carrier. The overall effect is that the boom is caused to rotate at an angular velocity which may be lower or higher or the same as the carrier. By varying the geometrical relationship between the position of the pivots and the angle of the levelling member/carrier linkage it is possible to change the ratio of this effect. BRIEF DESCRIPTION OF DRAWINGS The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:- Figure 1 is a diagram showing an agricultural sprayer vehicle carrying a spraying boom on level ground and incorporating ground attitude control means according to the present invention; Figure 2 is a diagram showing the sprayer of Figure 1 on uneven ground and showing that the boom remains level, and Figure 3 is a diagram generally similar to that of Figure 1 and showing that the ground attitude control means may be adjustable. BEST MODE FOR CARRYING OUT THE INVENTION In the drawings ground attitude control means adapted for use to control the spray boom of an agricultural spray apparatus comprises a carrying vehicle (not shown) having an axle (9) supporting a pair of ground engaging wheels (2). A spray boom framework (1) having spray nozzles (7) is pivotally mounted at (PI) on a carrying frame (12) which is mounted on the vehicle, and a levelling bar (3) is pivotally mounted at (P2) on the boom (1) at a position generally vertically above pivot (PI) and is joined by a linkage (6) to the carrying frame (12). Thus, as shown, the upper end (10) of the linkage (6) is attached to the levelling bar (3) and the lower end (11) of the linkage is connected to the carrying frame (12). The linkage (6) may be in the form of an hydraulic piston and cylinder device whereby the linkage is of adjustable length. The levelling bar (3) and the boom (1) are also connected by springs (4) and shock absorbers (5) . In the geometrical arrangement as shown, said control means operates to isolate the boom (1) from the movements of the carrying frame (12) or at least to moderate the connection between the boom and carrying frame for the purpose of maintaining a set distance between the chemical- applying nozzles (7) of the boom and the surface of the soil or growing crop (8) . Thus the geometrical arrangement of the parts of the control means may cause the boom framework (1) to rotate at a lower angular velocity than the carrying frame (12). The invention may be particularly applicable to an automatic levelling systems, e.g. an hydraulic levelling system since the positioning of the dampers (5) between the boom (1) and levelling member (3) will tend to improve the speed of response of the system. As shown in Figure 3, the levelling system may be variable, e.g. by manual adjustment, to move the position of the pivot (11) of the linkage (6) where it is attached to the carrier (12) laterally (i.e. along the boom) between the position shown in full lines, which provides negative compensation, through the generally vertical arrangement of pivots, shown dotted at X, which provides neutral compensation, to the second dotted position shown at Y, which is opposite to the position shown in full lines and which provides positive compensation. In some conditions, such as a sudden large rotational movement of the tractor, the boom rotating at a lower angular velocity than the tractor is desirable. This is because the boom is less sensitive to the rotational forces transferred from the tractor. This is what is termed negative compensation. In other conditions, such as a slightly undulating field or rapid, small changes in direction of the tractor, or when the tractor is negotiating a long, sharp bend, a higher angular velocity may be desirable. This is probably because the suspension system reacts quicker to correct a change in rotational attitude (relative to the carrying frame) when the rotational forces come from the boom itself. This is what is termed positive compensation. It could be that a compromise position may be the optimum under some circumstances and this could be close to or at vertical, i.e. the position X of the linkage. This is what is termed neutral compensation. The linkage (6) may be made infinitely adjustable between the positions shown in Figure 3 under the control of a suitable automatic mechanism so that the operator can select the optimum position for a given set of circumstances. Adjustment of the position of the linkage can also be used to control the damping effort of the shock absorbers or dampers (5) as desired, without the need to adjust the dampers themselves. INDUSTRIAL APPLICABILITY The control apparatus described above thus provides a simple mechanism for controlling the attitude of a member, e.g. the spray boom of an agricultural sprayer.

Claims: CLAIMS 1. Ground attitude control means to enable a member (1) to maintain a constant attitude with respect to the ground, comprising a carrier (12) on which the member (1) is pivotally mounted for movement about a substantially horizontal axis (PI), a levelling member (3) pivotally mounted on the member (1) for movement about a substantially horizontal axis (P2) and linkage means (6) pivotally connected between the levelling member (3) and the carrier (12), the pivotal connections being disposed to cause the member (1) to rotate at a desired angular velocity in response to rotation of the carrier (12). 2. Means according to claim 1, comprising at least one spring (4) and/or shock absorber (5) connected between the member (1) and the levelling member (3). 3. Means according to claim 1 or claim 2, wherein the linkage (6) is in the form of a length adjustable member, e.g. an hydraulic cylinder. 4. Means according to any preceding claim, wherein at least one of the positions (10,11) at which the linkage (6) is pivoted on the levelling member (3) and carrier (12) is adjustable longitudinally of the member (1) to vary the angular velocity of the member (1) with respect to the carrier. 5. Means according to any preceding claim, wherein at least one of the positions (10,11) at which the linkage (6) is pivoted on the levelling member (3) and carrier (12) is adjustable longitudinally of the member (1) to vary the damping effort exerted by a shock absorber (5) connected between the member (1) and the levelling member (3) . 6. Means according to any preceding claim, wherein the pivots (P1,P2) are generally vertically aligned. 7. Means according to any preceding claim, wherein the member (1) is an agricultural spray boom having spray nozzles (7) . 8. An agricultural sprayer comprising a spray boom (1) and ground attitude control means (3,6,12) according to any preceding claim connected to control the ground attitude of the spray boom.

Inventors: KNIGHT BRIAN GEORGE, TAYLOR KENNETH FREDERICK, KNIGHT, BRIAN, GEORGE, TAYLOR, KENNETH, FREDERICK
Applicants: KNIGHT BRIAN GEORGE, TAYLOR KENNETH FREDERICK, KNIGHT, BRIAN, GEORGE, TAYLOR, KENNETH, FREDERICK
Application year: 1998
Main classification: A01M7
IPC codes: A01M7