WO2010020607A1

WO2010020607A1 - Suspension for an agricultural machine

Info

Publication number: WO2010020607A1
Application number: PCT/EP2009/060606
Authority: WO
Inventors: Joris Jan Hiddema
Original assignee: Agco Netherlands B.V.
Priority date: 2008-08-22
Filing date: 2009-08-17
Publication date: 2010-02-25
Also published as: GB0815301D0; GB201103725D0; GB2474812B; GB2474812A

Abstract

An agricultural application machine comprising at least a pair of transversely spaced wheels is provided. Each wheel has an associated wheel carrier (18) mounted to a chassis by variable height suspension means to allow the ground clearance of the chassis underside to be adjusted. Each suspension means comprises an upper arm (23) and a lower arm (24) of unequal length, wherein each arm is connected between the chassis and the wheel carrier at respective pivotal joints (30, 31) thereby forming a four-bar linkage arrangement. The geometry of the arms and their pivotal mountings allows movement of the carrier in a plane which is substantially vertical and transverse to the longitudinal axis of the machine whilst the wheel track remains substantially constant over the range of possible heights.

Description

DESCRIPTION

SUSPENSION FOR AN AGRICULTURAL MACHINE

The invention relates to an agricultural application machine such as a self-propelled crop sprayer having single wheel suspension wherein each wheel has an associated wheel carrier mounted to a chassis by the suspension.

Agricultural application machines such as crop sprayers comprise a large volume tank carried on a chassis. Such machines can be trailed behind a tractor or provided as a self-propelled unit having an integral cab and engine. The machine further comprises an extending boom which provides a transverse line of uniformly spaced spray nozzles connected by pipes to the tank. During operation the application machine is moved across fields of crops such as cereals and maize to apply liquid fertilizer or chemical treatment such as herbicides, fungicides and pesticides to the crop in a controlled manner.

When fully laden the centre of gravity of the vehicle is primarily determined by the positioning of the tank on the vehicle. The operation over steep inclines dictates that the centre of gravity should be as low as possible so as to increase stability and reduce the risk of overturning of the vehicle. However, crops being treated often exceed one meter in height, particularly during the latter stages of the growth cycle and thus a machine having a profile with low ground clearance increases the risk of crop damage. It is thus desirable to provide an application machine having a variable ground clearance so that the centre of gravity can be kept as low as possible with the provision to raise the machine to avoid causing damage to the high crop over which the machine operates.

It is an object of the invention to provide an agricultural application machine which meets the above requirements and comprises an improved mechanism to vary the ground clearance of the machine.

In accordance with the present invention there is provided an agricultural application machine comprising at least a pair of transversely spaced wheels which each have an associated wheel carrier mounted to a chassis by variable height suspension means, each suspension means comprising an upper arm and a lower arm of unequal length, each arm being connected between the chassis and the wheel carrier at respective pivotal joints forming a four-bar linkage arrangement which allows movement of the arms and the carrier in a plane which is substantially vertical and transverse to the longitudinal axis of the machine, the height of the chassis above the ground being adjustable over a range, wherein the separation between the base of the wheels remains substantially constant over said range.

The invention involves the recognition that a variance in the ground clearance of a conventional application machine is often accompanied by a change in the wheel track, that is the distance between opposite wheels within a pair. An application machine usually operates over tramlines within a crop field wherein the same footprint is driven on by the machine wheels a number of times for multiple applications throughout the growing cycle. This minimizes the area of the field which cannot be used for growing a profitable crop and is a well established method of farming.

By providing a four-bar linkage arrangement in accordance with the invention the ground clearance of the machine can be varied over a large range without any significant change in the wheel track. This permits the same application machine to be employed over the same tramlines throughout the growing season and operable at a variable height to minimize the height of the centre of gravity.

For the purpose of describing the invention, it should be appreciated that the wheel carrier can be mounted to the chassis either directly or indirectly. For example, the wheel carrier and arms may be connected to a support structure which is itself mounted to the chassis in a manner which still allows the suspension means to vary the height of the chassis relative to the ground level upon which the wheels rest.

The upper arm and lower arm of the four bar linkage arrangement have a mutually unequal length which is chosen to minimize the variance in the transverse distance between the wheel base and the chassis of the machine. Therefore said transverse distance remains substantially constant over the range of heights, varying by no more than say 10mm over an example range wherein at least one of the upper and lower arms pivots between 20° below horizontal to 20° above horizontal.

In a preferred embodiment, the machine further comprises for each wheel a respective height adjustment actuator connected between a point fixed relative to the chassis and one of the upper and lower arms, wherein the length of the actuator is varied to adjust the height of the chassis above the ground. The actuator may take the form of a hydraulic or pneumatic cylinder wherein the operation thereof controls the movement of the four bar linkage relative to the chassis and thus the ground clearance height of the vehicle. This provision of fluid- operated cylinders allows the height of the machine to be changed at any point during operation by appropriate application of a hydraulic or pneumatic signal.

Together with restrictors and accumulators, the fluid controlled cylinders may also serve as suspension dampers to maintain the height of the chassis above the ground at a desired level during operation. By closing the valves connected to the cylinders thus forming a closed system the variation in height around the preset level is limited and damped.

At least one of the upper and lower arms is preferably H-shaped having a pair of pivot joints at each end thus providing sturdy support for the wheel carriers.

In one preferred embodiment the variable height suspension means for each wheel are mounted to a respective wheel support structure which is mounted to the chassis in a manner which allows the transverse distance between the wheel support structure and the chassis to be varied. Therefore, the track width of the wheels can be varied as required.

Further advantages of the invention will become apparent from the following description of the specific embodiments with reference to the appended drawings in which-

Figure 1 is a perspective view of a self-propelled agricultural sprayer;

Figure 2 is a side view of the sprayer of Figure 1 ;

Figure 3 is a perspective view of variable height suspension means, wheel carrier and wheel support structure for a pair of wheels of the sprayer of Figure 1 and in accordance with an embodiment of the invention;

Figure 4 is another perspective view of the variable height suspension means of Figure

3;

Figure 5 is a perspective view of the variable height suspension means of Figure 4 shown with one wheel attached;

Figure 6 is a perspective view of the variable height suspension means, wheel carrier and wheel support structure for one wheel of Figure 3; Figure 7 is a rear elevation view of the variable height suspension means, wheel carrier and wheel support structure of Figure 6;

Figure 8 is a plan view of the variable height suspension means, wheel carrier and wheel support structure of Figure 6;

Figure 9 is a plan view of an upper arm forming part of variable height suspension means in accordance with the invention;

Figure 10 is a perspective view of the chassis of the sprayer of Figure 1 ;

Figure 11 is a perspective view of the rear part of the underside of the sprayer of Figure

1;

Figure 12 is an underside view of the sprayer of Figure 1; and,

Figures 13a to e show the arm arrangement of Figure 6 (shown with wheel attached) at different ground clearance heights in accordance with the invention;

With reference to Figures 1, 2 and 12, a self-propelled arable crop sprayer 10 comprises a pair of front wheels 12 and pair of rear wheels 14 each wheel being separately mounted to a chassis 100 by respective variable height suspension means. The sprayer 10 further comprises a tank 15, a boom assembly 16 and driver's cab 17. The tank 15 accounts for the majority of the sprayer's volume and serves to hold the liquid material which is to be applied to a field. By way of example, the liquid material may comprise fertilizer or other chemical treatment such as herbicides, fungicides, pesticides or growth restrictors.

The liquid material is delivered in a controlled manner to spray nozzles (not shown) located on the boom assembly 16 by a network of supply pipes (not shown). In the transport mode (shown in Figures 1 and 2) the boom assembly 16 is retracted so as to remain substantially within the profile of the vehicle body thus allowing safe movement on the highway. In an operating mode the boom assembly 16 is extended so as to provide a transversely extending boom, having a width of 24 meters for example. Driven across an arable field, the liquid material is sprayed onto the crop in strips 24 meters wide at a time. The driver located in cab 17 controls the steering of the sprayer and the control of the liquid material application. It should be understood that Figures 1 and 2 show only one half (right-hand side) of the folded boom assembly 16.

The weight of a fully laden tank 15 accounts for a significant proportion of the overall vehicle weight. Therefore, the centre of mass of the sprayer 10 is located within the volume of the tank 15 as referenced at M in Figure 2. To maximize the stability of the sprayer 10 it is desirable to minimize the height of the centre of mass M above the ground. The requirement to avoid crop damage caused by the underside of the sprayer 10 dictates that the chassis 100 should be raised at least during operation on the field. Therefore variable height suspension means are provided to adjust the ground clearance of the underside of the sprayer 10.

With reference to Figures 3 to 9, each wheel 12, 14 has an associated wheel carrier 18 comprising a carrier element 19 and a wheel hub 20 rotatably mounted to the carrier element 19. The associated wheel 12 (Fig. 5) is bolted to the respective wheel hub 20, rotation of which is driven by a hydrostatic motor 21 which is mounted to the respective carrier element 19.

Each wheel carrier 18 is mounted to a respective wheel support structure 22 by an upper arm 23 and a lower arm 24, altogether forming a unit termed hereinafter a 'corner module'. The wheel support structure 22 for each corner module is a cast unit which is, in this embodiment, attached to the chassis 100 by a track varying mechanism which allows the track width, that is the distance between wheels within a respective pair, to be changed. The track varying mechanism will be described in more detail below. However, it should be appreciated that a mechanism to provide variable track width is not necessary and that the wheel carriers 18 can be suspended directly from the chassis 100 without deviating from the scope of the invention. In fact, an application machine having such fixed track width particularly benefits from the invention because of the variable height provided accompanied with minimal track variance.

In any case, the wheel support structure 22 is mounted so as to maintain a constant height relative to the chassis 100.

All four wheels 12, 14 are steerable. However, it should be appreciated that a self-propelled vehicle may be provided with only two-wheel steering. To enable steering, each carrier element 19 is pivotally mounted to an upright king pin 27 which forms part of the wheel carrier 18 as shown in Figure 6. Welded to one side of each carrier element 19 is a steering lever 28 in the form of a bracket. At the end remote the carrier element 19 a steering cylinder 29 is pivotally connected to the steering lever 28. The other end of the steering cylinder 29 is secured relative to the wheel carrier 18. Pressurise fluid supplied to each of the steering cylinders 29 controls the steering of the associated wheel.

For each of the four corner modules, each of the upper arm 23 (Figure 9) and lower arm 24 have an H- shaped construction having a pair of transverse extensions 23 a connected by a longitudinally (relative to the normal direction of vehicle travel) extending tie 23b. Each arm 23, 24 is pivotally connected to the wheel support structure 22 by a respective pair of pivotal joints 30 which allow pivotal movement of the arms about a longitudinal axis, Xl, X2 (Figure 6). Each joint 30 comprises a pin 30a which retains the associated arm extension 23a between a respective pair of jaw elements 30b provided by the associated wheel support structure.

At the opposite (outside) end of each arm 23, 24 a respective pair of pivotal joints 31 connect each arm to the wheel carrier 18. In the embodiment shown, the outer joints 31 for each arm

23, 24, share a common pin 31a to retain the associated wheel carrier 18 although separate pins may be employed instead. In accordance with the invention, the upper arm 23, lower arm

24, wheel carrier 18 and wheel support structure 22 connected at the respective pivoting joints 30, 31 provide a four-bar linkage arrangement which allows movement of the arms 23,24 and the carrier 18 in a plane which is substantially vertical and transverse to the longitudinal axis of the machine 10. By a pivoting motion of the arms 23,24 the ground clearance of the chassis can be adjusted over a large range.

The unequal lengths of the upper and lower arms 23,24 are chosen to minimize the variation in transverse separation between the base of the wheel and the chassis as discussed in more detail below.

A hydraulic cylinder 40 is provided for each of the suspension units to adjust the height of each wheel 12, 14 relative to the chassis 100. A first upper end 40a of each hydraulic cylinder 40 is fixed relative to the associated wheel support structure 22 by means of a pivoting link supported on a pin 41. In this case, the upper end 40a is fixed relative to the associated wheel support structure 22 by an appropriate attachment point 101 on the chassis 100. A second lower end 40b of each cylinder 40 is pivotally connected to the associated lower arm 24 by a joint 42. Each cylinder 40 has connected thereto fluid pipes 40c which deliver a supply of oil to the cylinder chambers so as to control movement of the piston located therein. A pair of accumulators 43 are provided for each cylinder 40 to provide a spring function which damps vibrations transmitted from the wheels to improve the comfort for the driver and reduce the effect of the vibrations on the boom assembly 16. In response to an appropriate hydraulic signal applied to the cylinders 40, the four-bar linkage arrangement attached thereto is moved thus adjusting the height of the chassis 100 above the ground. The cylinder 40 controls movement of the four bar linkage over the entire range of available heights from a fully raised position to a fully lowered position.

It should be appreciated that each wheel carrier is raised and lowered as a single unit. Therefore, the carrier element 19, king pin 27 and steering cylinder 29 move up and down in unison.

With reference to Figure 13 a, the hydraulic cylinder 40 is shown in a fully retracted state corresponding to a minimum length. When in this fully retracted state the upper and lower arms 23,24 are in a fully raised state corresponding to a fully lowered state (minimum ground clearance) of the sprayer chassis 100.

By the application of an appropriate hydraulic signal to hydraulic cylinder 40 the length thereof is increased thus lowering the upper arm 23 and lower arm 24 to an intermediate position as shown in Figure 13b wherein the lower arm 24 is horizontal with respect to the ground. At this point the transverse separation between the wheel support structure 22 and the base of the wheel 12 has increased by no more than 8mm.

Extending the hydraulic cylinder 40 further still the upper and lower arms 23,24 are moved to a fully lowered position as shown in Figure 13c which corresponds to a fully raised position of the chassis 100 having maximum available ground clearance. The transverse separation of the base of the wheel 12 from the wheel support structure 22 in this full raised position (Figure 13c) is less than 6mm as compared to the separation in the fully lowered position (Figure 13a).

By forming the upper and lower arms 23, 24 of an appropriate length, the four-bar mechanism delivers minimal transverse movement thus keeping the track width substantially constant (within 10 mm) over the range of possible ground clearance settings.

From the above discussion it should be appreciated that the fully lowered position of Figure 12a is suitable for use during transport of the sprayer, on highways for example, wherein the centre of mass M is at it lowest possible height thus providing maximized stability of the vehicle. In contrast, the fully raised of Figure 12c is employed when operating over high crops which are susceptible to damage from an underside of a sprayer. The use of hydraulic cylinders 40 for each corner module not only allows the operator to vary the overall height of the sprayer 10 but allows the chassis 100 to be levelled when operated on a side bank for example by appropriate lowering of the downhill side wheel carrier.

Although the operator of the sprayer 10 can set the ground clearance of the chassis 100 manually from a preset choice of heights, it is envisaged that the height may be set over a continuous range and which may be controllable by a simple lever in the cab 17 connected to a spool valve. Furthermore, raising and lowering of the chassis 100 above the ground may be automated in conjunction with ground clearance sensors located on the underside of the vehicle wherein the height is automatically increased when an increase in crop height is detected. This is particularly advantageous when the height of the crop varies across the working area.

Turning back to the construction of the corner modules, and particularly to the aforementioned variable track mechanism, each wheel support structure 22 includes a pair of bearing blocks 50 which are cast into the unit. Each bearing block 50 comprises a transversely extending bush-lined sleeve 52 which receives a respective transversely extending shaft 54 which is secured by a series of brackets 102 bolted to the underside of the chassis 100 (Figure 11). Each wheel support structure 22 is slidably mounted on a pair of transversely extending shafts 54 so that the wheel track of the vehicle can be varied as required. As can be seen from Figures 3 to 5, each pair of wheels 12, 14 shares a pair of mounting shafts 54.

To control the track width, each pair of wheels has associated therewith a pair of hydraulic actuators 56. As can be seen in Figure 4 for example, the actuators are each connected between mounting pins 57 provided on transversely opposing wheel support structures 22, one disposed forwardly of the front-most shaft 54 and the other disposed rearwardly of the rear-most shaft 54. Each actuator 56 comprises a piston (not shown) slidably contained within a cylinder 56a. A piston rod 56b is connected to the piston. The two actuators 56 associated with a given pair of wheels are mechanically connected in an opposing parallel relationship wherein the piston rod 56b of one actuator is connected to the left-hand wheel support structure 22 and the piston rod 56b or the other actuator is connected to the right-hand wheel support structure 22.

Pressurised fluid is supplied to the actuators 56 so as to control the separation of the wheel support structures 22 and thus the track width of the vehicle. It may be necessary to ensure the vehicle is moving in order to effect smooth adjustment of the track width without subjecting the corner modules to unnecessary transverse strain.

Although the invention has been described above with reference to a self-propelled crop sprayer 10 it is envisaged that the invention is also applicable to trailed application machines which are towed behind tractors for example. Such trailed sprayers suffer from the same problems associated with instability and ground clearance.

The pivoting range of the lower arm 24 in the above-described embodiment is from 20° below horizontal to 20° above horizontal. However, it is envisaged that this range may be greater or smaller as required.

Thus far, the adjustment of the vehicle's ground clearance has been effected by operation of a set of hydraulic cylinders in response to applied hydraulic signals. However, it is envisaged that in a more technologically simplistic arrangement, the height adjustment of the chassis relative to the wheel carriers may be carried out manually, perhaps by jacking up the chassis and releasing/replacing locking pins.

In the preferred embodiment described, each of the upper arms 23 and lower arms 24 are H- shaped to deliver a sturdy support for each wheel. However, it is envisaged that one or both arms may take a different form, say wishbone shaped having a single universal joint to the wheel carrier to allow for a steering movement.

In summary, there is provided an agricultural application machine comprising at least a pair of transversely spaced wheels. Each wheel has an associated wheel carrier mounted to a chassis by variable height suspension means to allow the ground clearance of the chassis underside to be adjusted. Each suspension means comprises an upper arm and a lower arm of unequal length, wherein each arm is connected between the chassis and the wheel carrier at respective pivotal joints thereby forming a four-bar linkage arrangement. The geometry of the arms and their pivotal mountings allows movement of the carrier in a plane which is substantially vertical and transverse to the longitudinal axis of the machine whilst the wheel track remains substantially constant over the range of possible heights.

From reading the present disclosure, other modification will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the field of agricultural application machines and component parts therefore and which may be used instead of or in addition to features already described herein.

Claims

1. An agricultural application machine comprising at least a pair of transversely spaced wheels which each have an associated wheel carrier mounted to a chassis by variable height suspension means, each suspension means comprising an upper arm and a lower arm of unequal length, each arm being connected between the chassis and the wheel carrier at respective pivotal joints forming a four-bar linkage arrangement which allows movement of the arms and the carrier in a plane which is substantially vertical and transverse to the longitudinal axis of the machine, the height of the chassis above the ground being adjustable over a range, wherein the separation between the base of the wheels remains substantially constant over said range.

2. An agricultural application machine according to Claim 1 , wherein at least one of the upper and lower arms pivots over a range of 20 degrees below horizontal to 20 degrees above horizontal.

3. An agricultural application machine according to Claim 2, wherein said separation over said range varies by less than 5mm.

4. An agricultural application machine according to any preceding claim, further comprising for each wheel a respective height adjustment actuator connected between a point fixed relative heightwise to the chassis and one of the upper and lower arms, wherein the length of the actuator is varied to adjust the height of the chassis above the ground.

5. An agricultural application machine according to Claim 4, wherein each actuator comprises a hydraulic cylinder and piston.

6. An agricultural application machine according to Claim 4, wherein each actuator comprises a pneumatic cylinder and piston.

7. An agricultural application machine according to Claims 4 or 5, wherein the cylinder is connected to a control unit by a fluid line which actuates the cylinder in response to a signal from an operator.

8. An agricultural application machine according to any one of Claims 4 to 7, wherein during operation the actuator serves as a damper to maintain the height of the chassis above the ground at a desired level.

9. An agricultural application machine according to any preceding claim, wherein at least one of the upper and lower arms is H-shaped.

10. An agricultural application machine according to any preceding claim, wherein the variable height suspension means for each wheel are mounted to a respective wheel support structure which is mounted to the chassis in a manner which allows the transverse distance between the wheel support structure and the chassis to be varied.

11. An agricultural application machine according to Claim 10, wherein each wheel support structure is mounted to the chassis by slideable mounting means comprising a shaft which is slideable within a bearing block.

12. A self-propelled sprayer according to any preceding claim.

13. A trailed sprayer according to any one of Claims 1 to 11.

14. A self-propelled sprayer constructed and arranged substantially as hereinbefore described with reference to, and as shown in the accompanying Figures.