GB2595686A - Chassis for trailed implement - Google Patents

Abstract

An articulated chassis for a trailed agricultural implement 2 having a drawbar 3 mountable on a tractive vehicle, a front frame 12 for supporting at least one agricultural implement 6, 8, the front frame including a pivotal coupling for receiving the drawbar; a rear frame 16 for supporting at least one agricultural implement which maybe a seed container and the rear frames including at least one pair of load bearing wheels 22, the rear of the front frame being connected to a front of the rear frame at a pivot point 14 and at least one pair of adjustable arms 18 extend between the frames, the arms being independently extendable in length, the chassis including at least one linkage 5 from the drawbar to the pivot point to impart movement to the pivot, the chassis further comprising an actuator 44 for controlling adjustment of the length of the arms in response to rotation about the pivot point. The linkage maybe a cable extending around a pulley 4 and the cable maybe in communication with a cam (14, figure 2A) mounted about the pivot point whereby rotation of the drawbar causes linear movement of the cable around the pulley to impart rotational movement to the cam. The arms may comprise a pair of hydraulic rams

Description

Chassis for Trailed Implement

Field of the Invention.

The present invention relates generally to an agricultural machine, and more particularly to an improved chassis for an agricultural implement or implements trailed behind a tractor, such as a soil cultivator seed drill.

Background

Tractors are widely used to tow various types of implement for working the land, such as trailers, inter row hoes or soil cultivator seed drills. Most are long and wide, requiring a large turning circle by the tractor. The increasing tendency to include implements for carrying out multiple functions on a single trailed machine also adds to the length of the device. For example, soil cultivator seed drills are popular because they enable opening the soil, seeding and fertilizing to be carried out in a single pass. A long narrow seed tank is carried on the trailed implement and multiple rows of spaced apart multiple soil cultivator seed drills are provided on a frame or chassis, being folded outwardly when in use or folded up against the sides of the tank for transportation. However, the maneuverability of such long implements is an issue because they do not accurately track movement of the tractor resulting in inaccurate seeding or application of fertilizer due to the inability of the trailed implement to follow in line with the tractor.

This is even more problematic with inter row drilling where the drill's seeding arms need to sit between established crop rows to prevent damage to the existing crop. It is often desirable to cultivate two different crops ("companion crops"), possibly at staggered times but currently available machines do not provide sufficiently accurate sowing to prevent damage of the existing crop.

When towing a trailing implement around a corner the implement will understeer and cut the corner, requiring the tractor to over steer on a bigger arc to avoid the trailed implement cutting too close to an obstacle, such as a gate post. Skilled steering of the tractor and trailed implement is required to enable efficient working of the land. However, this has become particularly problematic due to the widespread adoption of satellite steering of the tractor. Satellite steering enables the tractor to be autosteered 1.

by the use of military satellites. However, this can only be done for straight lines up and down fields and the actual turning needs to be done by a skilled labourer to ensure efficient use is made of all the field. The use of automated satellite steering increases the use of less skilled labourers but this can result in less efficient use of the field due to extensive oversteering during turning of the tractor by the less skilled labourer. Alternatively, damage may occur to the machinery or farm property due to obstacles being hit due to understeering. Satellite signals, although extremely accurate, can also be very temperamental, with the signal being broken if obscured by trees etc. Some countries are also ill equipped to work with such high-tech machinery.

It is known to provide trailed implements with a rear steering axle arrangement wherein wheels on the rear axle/trailer are fixed by king pins. These wheels may then be steered, typically by a controller, such as an in cab controller or other device. However, this arrangement creates "crabbing" or sideways movement of the back part of the trailed implement, again creating a large turning circle. The sideways movement is fine for trailed implements that operate above ground, such as trailers, but it is unsatisfactory for ground engaging equipment, for example drills or cultivators. This is because the crabbing creates a large strain on the ground engaging elements due to the implement wanting to crab sideways, increasing wear on the parts or causing expensive damage. This sideways movement also makes reversing the implement very difficult It is the aim of the present invention to provide an improved chassis for an agricultural implement, such as a soil cultivator seed drill, that is towed behind a tractor that overcomes, or at least alleviates, the abovementioned problems.

Summary of the Invention

According to the present invention there is provided an articulated chassis for a trailed agricultural implement, the chassis comprising: a drawbar mountable on a tractive vehicle; a front frame for supporting at least one agricultural implement, the front frame including a pivotal coupling for receiving the drawbar; a rear frame for supporting at least one agricultural implement, the rear frame including at least one pair of loading bearing wheels; wherein a rear of the front frame is connected to a front of the rear frame at a pivot point and at least one pair of adjustable arms extend between the frames, the arms being independently extendable in length, the chassis including at least one linkage from the drawbar to the pivot point to impart movement to the pivot, the chassis further comprising an actuator for controlling adjustment of the length of the arms in response to rotation about the pivot point.

The at least one linkage from the drawbar to the pivot point preferably comprises at least one cable extending around a pulley provided on the drawbar. More preferably, the cable is a Bowden cable or fie bar. The opposing end of the at least one cable is preferably in communication with a cam mounted about the pivot point of the front and rear frame. In this manner, rotation about the drawbar coupling causes linear movement of the cable around the pulley to impart rotational movement to the cam.

Preferably, the at least one cable crosses over the front frame, i.e. passing from the right hand side of the pulley to the left hand side of the cam or vice versa.

The adjustable arms are preferably a pair of hydraulic rams extending between the front and rear frames either side of the pivot point.

The front or rear frame, preferably rear frame, is provided with a detector for detecting rotation of the cam. Preferably, the detector is at least one microswitch, micromagnet or other suitable detector for detecting the extent and direction of rotation of the cam. Preferably, the detector communicates with the at least one actuator to adjust the length of one or both adjustable arms depending upon the degree and direction of rotation of the cam. Preferably, the actuator comprises a valve block for controlling delivery of hydraulic fluid to and from the rams.

In a preferred embodiment of the present invention, the front frame is in the form of a longitudinal support bar having the drawbar coupled to it at one end thereof and having a pair of laterally extending wings at the other end. Preferably one end of each adjustable arm is attached to each wing. The other end of each arm is attached to a front part of the rear frame. The longitudinal axis of the rear frame is in line with the longitudinal axis of the front frame when the lengths of the adjustable arms are substantially equal, i.e the articulated chassis is straight and will travel in a straight line.

Adjustment of the length of one of the arms to provide arms of unequal length causes turning of the rear frame with respect to the front frame.

Preferably, adjustment of the arms only occurs when a predetermined range of motion has been imparted to the cam, thereby providing an articulated chassis with a degree of slack movement. For example, the cam may be provided with an extension extending from the cam in the direction of the rear chassis. The extension may have a curved surface corresponding to the curvature of the cam but includes an indent or recess extending across a part of the arc. This allows for a certain amount of rotation of the cam without detection by the detector thereby preventing any corresponding movement of the rams. The cam may also be spring loaded so that it reverts back to centre, i.e. to equalize the length of the arms and re-align the front and rear frame.

Ideally, locking means is provided to lock rotation of the cam, for example, if articulation of the chassis is not required for a particular purpose, i.e. road use.

It is to be appreciated that any type of implement may be attached to the front and to the rear frames that form the articulated chassis of the present invention. It is preferred for the heavier implement or implements to be supported on the rear frame having the load bearing wheels, more preferably being close to the pivot point.

In a preferred embodiment of the present invention, the front frame has at least one cross member for mounting a plurality of spaced apart soil cultivator seed drills. More preferably, at least two cross members extend transversely from the front frame, preferably wherein the soil cultivator seed drills on the first cross member are staggered with respect to those on the second cross member. Preferably, the container for the seeds and/or fertilizer is supported on the rear frame, preferably between the load bearing wheels. One or more other trailed implements may be attached to the rear of the rear frame. For example, the frame may includes a lever arm connected to a rear bar that includes a plurality of levelling fines.

Preferably, each soil cultivator seed drill comprises a toolbar connection member for attachment to the cross member, a soil loosening member having a leg inclined rearwardly and downwardly terminating in a forward-facing toe, a seed sowing member spaced rearwardly of the soil loosening member, the seed sowing member having a leg extending downwardly and terminating in a seed delivery foot. More preferably, each soil cultivator seed drill is pivotably mounted with respect to the cross member, the pivot having a longitudinal axis comprising a camber angle extending substantially from the pivot to a region of the forward-facing toe of the soil loosening member of the soil cultivator seed drill.

The toolbar connection member may comprise a clamp and/or a bracket. Preferably, the soil loosening member and seed sowing member are each pivotally attached to a bracket and the bracket is pivotally mounted to a clamp that comprises the toolbar connection member. Preferably, the pivot with the camber angle is provided between the clamp and the bracket.

The camber angle is preferably between 10 and 45 degrees, more preferably 18-30 degrees, off vertical inclined forwardly towards the clamp. In particular, the longitudinal axis of this pivot may extend from the pivot substantially in line with the front point of the toe of the soil loosening member, albeit the exact positioning of the toe does vary with the depth of the soil loosening member.

It is to be appreciated that the soil loosening member and/or seed sowing member of each soil cultivator seed drill may be provided with a socket for connection to a delivery tube for delivery of seed and/or fertiliser from the container on the rear frame.

In a preferred embodiment of the present invention, the seed sowing member includes a depth wheel located rearwardly thereof, preferably being pivotally mounted with respect to the seed sowing member.

Additionally, the clamp of the toolbar connection member may comprise a substantially L-shaped portion with its apex extending vertically downwardly towards the ground. Preferably, one end of the clamp has an inclined socket to receive the pivot pin of the bracket and the other end forms a lip or rim. Suitable fastening means are provided for attachment of the clamp to a box section of a toolbar assembly. Preferably, the clamp is forwardly inclined.

Preferably, the at least one cross member has a box-section whereby the clamp of the implement may be fastened at any point along the length of the cross member by suitable fastening means, such as a nut and bolt.

One or more parts of the front and/or rear frame may be hingedly mounted to the frame, thereby enabling the machine to be folded up for transport, supported by the frame.

It is to be appreciated that the articulated chassis according to the present invention may include additional features that are conventional for carrying agricultural implements and machines in the art. For example, some or all of the parts may be foldable and/or liftable to allow their easy transportation when not in use and that the different types of movement of the component parts, such as folding, lifting, rotating etc are achieved by suitable actuation means. Preferably, hydraulic means is provided, ideally being controlled from within the tractor.

A metering unit may be included for delivery of seed and/or fertiliser to each implement. Preferably, an in-cab drill management system provides on-the-move seed rate adjustment plus all of the normal essential seed drill control and monitoring functions.

Brief Description of the Drawinqs

For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made by way of example only to the accompanying drawings in which: Figure 1 is a top view of a trailed implement having an articulated chassis according to an embodiment of the present invention, shown in a turning position; Figures 2A to 2C are expanded views of an articulated joint of one embodiment of an articulated chassis of the invention, shown in different turning positions; Figure 3 is a top view of a trailed implement having an articulated chassis according to an embodiment of the present invention, shown in a straight position; Figure 4 is a top view of the trailed implement shown in Figure 3, shown in a turning position; Figure 5 is a side view of the embodiment shown in Figure 3; Figure 6 is a perspective front side view of the embodiment shown in Figure 3, shown in the straight position; and Figure 7 illustrates the embodiment shown in Figure 6, shown in a turning position.

Detailed Description

Agricultural machinery typically include a long, trailed implement or implements attached to the back of a tractor, such as a drill, trailer or cultivator. Due to the length of the trailed implements, a large turning space is required. Conventionally, when a tractor tows a non-articulated implement around a corner using a fixed long drawbar, the trailed implement will understeer and cut the corner. In order to compensate for this, the tractor must steer on a bigger arc to avoid the trailed implement cutting too close to an obstacle, such as a gate post or tree. This is particularly apparent when an implement such as a seed drill, must turn on the headlands of a field in order to change direction. Thus, a long and wide implement will need a correspondingly wide headland to manoeuvre.

The present invention provides an articulation between a front frame and a rear chassis of an agricultural trailer or trailed implement that serves to reduce the space required to change direction, thereby providing more efficient use of space within a field and enabling a tractor to more accurately and efficiently manoeuvre the trailer or trailed implement around obstacles, such as trees. In essence, the invention provides two trailers in a row with the second being able to follow the tractor correctly.

The articulated chassis of the present invention enables the trailed implement to track movement of the tractor, effectively self-steering the rear trailer. Figure 1 of the accompanying drawings shows an example of an agricultural trailed implement 2 which may be attached to the rear of a tractor by a linkage drawbar 3. In this embodiment, the implement consists of two rows of a plurality of soil cultivator drills with seeding members 6, 8 attached to two cross bar members 10 on a front frame 12. The front frame is pivotally attached to a rear chassis 16 having a pair of load-bearing wheels 22 and a plurality of tines 30 extend from the rear of the trailed implement.

However, it is to be appreciated that the invention is not limited to this arrangement of implements and that the front frame 12 and rear chassis 16 may carry any other type of trailed agricultural machinery in any order, albeit it is preferred that the heavier machinery/implements are provided on the rear chassis 16, being supported by the wheels 22 and close to the articulation between the front and rear frames.

The front frame 12 and rear chassis 16 are connected via a mechanical linkage and cam (see, in particular Figures 2A to 2C) to provide an articulated implement which is able to follow the tractor axle in line, creating no understeer. The front frame 12 includes a central bar terminating in a pair of wings 12a, 12b extending laterally outwardly from the bar. These wings 12a, 12b are each pivotally connected to the front of the rear chassis 16 by a hydraulic ram 18, movement of which is affected by operation of a valve block 44.

The linkage drawbar 3 is pivotally attached to the rear of the tractor (not shown) and a pulley 4 is provided about the pivot point and carries a cable 5, such as a Bowden cable or tie bar, which extends from the pulley 4 along and across the front frame central bar 12 and is connected to a rear cam 14 mounted about a pivot connecting the central bar 12 to the rear chassis 16. A switch 40, such as a micromagnet switch, electric switch or mechanical idler roller, is carried on the rear chassis for detection of movement of the rear cam. This communicates with a valve block 44 on the chassis which acts to open/close valve ports that provide a passageway for hydraulic fluid to flow to or from the hydraulic rams 18 affecting movement of the rear chassis in response to rotational movement of the cam 14. For example, when the tractor is travelling straight the rams are of equal length in a neutral position but shifting the valve to the right or left routes fluid to one or other of the piston rods of the hydraulic rams to cause right or left turning of the rear chassis (as shown in Figure 1).

Thus, the articulated two-frame trailer as shown in Figure 1 is able to follow and track accurately the tractor that is pulling it. When the tractor is travelling straight, the drawbar 3 lies substantially perpendicularly to the front frame central bar 12, and the pulley 4 and rear cam 14 remain in the neutral position wherein the rams 18 between the wings 12a, 12b of the front frame and rear chassis 16 are of identical length (see, for example, Figure 2C, 3 and 6). This ensures that the two-frame trailer is pulled in a straight line, tracking the straight line of the tractor. As the tractor turns, for example turning towards the left as shown in Figure 1, the linkage draw bar 3 turns which imparts a corresponding movement of the cable 5 via the pulley 4. The movement of the cable 5 causes a corresponding rotational movement of the rear cam 14 which is detected by at least one switch 40 and causes operation of valve block 44 to transfer hydraulic fluid, such as oil, to the rams 18 thereby shortening the ram on the left hand side and equally delivering oil to lengthen the right hand ram, causing turning of the rear chassis 16 to track movement of the tractor. As the tractor straightens up, the drawbar straightens back up causing a corresponding movement of the cable 5 about pulley 4 to affect rotation of the rear cam 14, thereby signalling to the valve block 44 via switch 40 to increase the length of the ram on the left hand side and straighten up the rear frame with respect to the front frame.

In this manner, the trailed machine, in particular the rear chassis of the two-part trailer, will articulate and track the tractor that is towing the machine, effectively self-steering. The connection between the pulley on the drawbar and the rear cam of the rear frame which affects operation of the valve block enables the action of the rams 18 to mirror the angle of the tractor's axle, self-steering the implement to the follow the tracks of the tractor.

In a preferred embodiment and as shown in the accompanying drawings, rear cam 14 is provided with an extension 14b extending from the cam in the direction of the rear chassis. The extension 14b has a curved surface corresponding to the curvature of the cam but includes an indent or recess extending across a part of the arc. This allows for a certain amount of rotation of the cam without any corresponding movement of the rams, preventing turning of the rear chassis until a predetermined angle of rotation of the front draw bar (and thus corresponding amount of rotation of the cam) has occurred, thereby allowing for a certain degree of slack movement. The cam may also be spring loaded so that it reverts back to centre to re-align the front and rear frames Any suitable switch may be used to detect movement of the cam to operate the valve block but preferably a magnetic eye (micromagnet) switch is used. This involves the use of a metal cam which is detected by the micromagnet when it is in proximity thereto. It is very accurate and subjected to less wear and tear due to lack of contact between the respective parts.

It is clear that the articulated trailer of the present invention could be used for a wide range of implements including a seed drill, cultivator, inter row hoe or a trailer. However, the present invention is particularly suitable for strip tillage, for example using a soil cultivator seed drill as described in the Applicant's co-pending GB Application No. 2005758.4. These soil cultivator seed drill implements 6, 8 each include a soil loosening member 60 and a seed sowing member 70 having a depth wheel 80 (see, for example, Figures 3 to 7). The front soil loosening member 60 is pivotably attached to a bracket about a horizontal axis and an adjustable hydraulic ram applies pressure to the member to ensure consistent contact with the ground. The soil loosening member or coulter 60 includes a leg inclined rearwardly and downwardly which terminates in a forward-facing pointed toe with parallel planar flanges extending rearwardly from the toe, substantially at right angles thereto. Optionally, seed or fertiliser may be delivered through delivery tubes (not shown) connectable to a socket member. The seed sowing member or coulter 70 is connected to the bracket via a parallel four-bar linkage to locate the member at a rearwardly spaced apart distance from the soil loosening member 60 and includes a leg extending downwardly from the rearmost bar of the linkage, the leg terminating in a seed delivery foot having laterally extending wings. A socket member is provided in fluid communication with the foot for connecting to a seed delivery conduit (not shown for sake of simplicity) which can deliver seed into the foot for placement in the soil. The depth wheel 80 is pivotably mounted to a rear end of the lower bar of the four-bar linkage about a horizontal axis via arms to allow for up and down movement of the depth wheel. An adjustable link may be varied in length to adjust the depth of the wheel.

Each cross member 10 is connected to the front frame by a ram 99, typically being lengthened or shortened to raise the implement carrying cross members 10 in and out of work. i.e. raising the cross member 10 to turn on the headlands and then lowering it back towards the ground once positioned ready to work. Similarly, a ram 99 is provided on the rear toolbar which serves to raise or lower an implement such as a rear harrow in and out of work.

The soil cultivator seed drill implements 6, 8 are preferably pivotably connected to a cross bar 10 by an adjustable clamp, the pivot preferably being a camber angle between 10 and 45 degrees, more preferably 18-30 degrees, off vertical inclined forwardly towards the clamp as discussed in the Applicant's co-pending GB Patent Application No. 2005758.4.

As shown in Figures 3 to 7, a plurality of soil cultivator seed drill implements 6, 8 are attached at spaced apart intervals to a front and rear transversely extending box section cross member 10 mounted on the front frame 12. Generally, the front and rear rows are staggered with respect to each other. The rear chassis 16 having the load bearing wheels 22 carries the seed container 100 with a plurality of levelling tines 30 extending from the rear of the rear chassis 16 behind the seed container 100. The seed container 100 has standard delivery tubes and a metering system (not shown) to deliver seed and/or fertilizer through the pipes to the seed sowing members and/or soil loosening members.

The provision of a seed cultivator machine on an articulated chassis according to the invention provides increased accuracy of towing and in particular enables the wheels 22 to accurately track the wheels of the tractor. This in turn enables accurate tilling and seeding by the machine and prevents damage occurring to any companion crops previously sown into the ground.

Furthermore, the articulated chassis according to the present invention is also beneficial when soil engaging implements are located on the rear frame. Without articulation, tines or other soil engaging equipment are pushed around the corner causing sideways pressure on the implement. This limits its effectiveness and also increases wear on the metal. It also makes it more difficult for the tractor to tow the implement due to it trying to move sideways through the soil rather than following the track of the tractor. The articulated chassis of the invention enables any implement on the rear frame to travel in the direction of the tractor and in the direction it was intended, reducing sideways pressure, limiting wear on these parts and making the implement easier to pull through the soil The articulated chassis also enables a much larger capacity seed container to be supported on the rear chassis between the loading bearing wheels, increasing the efficiency of operation further. The seed container is also more accessible than those provided along the longitudinal axis of a conventional fixed frame. Locating the seed container on the rear chassis also increases visibility for the driver and improves the loading of the trailed implement with respect to the tractor.

The ability to effectively track the movement of the front tractor using a mechanical linkage lowers the skill level required for accurate driving of the tractor. The flexible linkage also allows turning as well as up and down movement which is required with strip-tillage of the land. The ability to track the tractor also has the advantage that the rear frame (section two located behind the pivot or frame 16) will naturally track the front frame (section one) when seeding the perimeter of the field, i.e. drilling the headlands which are often curved. The provision of a central pivot between the two sections improves the accuracy of the ground engaging implements, thereby increasing the accuracy of drilling or potentially inter row hoeing or seeding around curved headlands or obstacles. The two-section articulated frame also increases the flexibility as to where on the machine these implements can be located (i.e. either front or rear frame) A further significant advantage provided by the articulated chassis of the present invention is that it works equally well in reverse as it does going forward. In contrast, when reversing a conventional trailer with a fixed axle the driver must turn the vehicle in the opposite direction. With the present invention, the driver is able to reverse the vehicle as normal and the articulated axle follows the line created by the axle of the tractor, effectively following the same circle. This significantly reduces the level of skill required to successfully reverse a tractor towing a trailed implement.

It is to be appreciated that modifications to the aforementioned implement and machine may be made without departing from the principles embodied in the examples described and illustrated herein.

Claims (19)

1. CLAIMS.1 An articulated chassis for a trailed agricultural implement, the chassis comprising: a drawbar mountable on a tractive vehicle; a front frame for supporting at least one agricultural implement, the front frame including a pivotal coupling for receiving the drawbar; a rear frame for supporting at least one agricultural implement, the rear frame including at least one pair of loading bearing wheels; wherein a rear of the front frame is connected to a front of the rear frame at a pivot point and at least one pair of adjustable arms extend between the frames, the arms being independently extendable in length, the chassis including at least one linkage from the drawbar to the pivot point to impart movement to the pivot, the chassis further comprising an actuator for controlling adjustment of the length of the arms in response to rotation about the pivot point.C\I 2. The articulated chassis as claimed in claim 1 wherein the at least one linkage from the drawbar to the pivot point comprises at least one cable extending around a pulley provided on the drawbar.
2. CD
3. C3) 3. The articulated chassis as claimed in claim 2 wherein the opposing end of the at least CD one cable is in communication with a cam mounted about the pivot point of the front and rear frame whereby rotation about the drawbar coupling causes linear movement of the cable around the pulley to impart rotational movement to the cam.
4. 4. The articulated chassis as claimed in claim 3 wherein the at least one cable crosses over the front frame.
5. 5. The articulated chassis as claimed in any one of the preceding claims wherein the adjustable arms comprise a pair of hydraulic rams extending between the front and rear frames, either side of the pivot point.
6. 6. The articulated chassis as claimed in claim 3, claim 4 or claim 5 wherein the front or rear frame, preferably rear frame, is provided with a detector for detecting rotation of the cam.
7. 7. The articulated chassis as claimed in claim 6 wherein the detector is at least one of a microswitch, micromagnet or other suitable detector for detecting the extent and direction of rotation of the cam.
8. 8. The articulated chassis as claimed in claim 6 or claim 7 wherein the detector communicates with the at least one actuator to adjust the length of one or both adjustable arms dependent upon the degree and/or direction of rotation of the cam.
9. 9. The articulated chassis as claimed in claim 8, wherein the actuator comprises a valve block for controlling delivery of hydraulic fluid to and from the rams.
10. 10. The articulated chassis as claimed in any one of the preceding claims, wherein the front frame is in the form of a longitudinal support bar having the drawbar coupled to it at one end thereof and having a pair of laterally extending wings at the other end.CD
11. C\I 11. The articulated chassis as claimed in claim 10 wherein one end of each adjustable arm is attached to each wing and the other end of each arm is attached to a front part of the rear o frame, the longitudinal axis of the rear frame being in line with the longitudinal axis of the a) front frame when the lengths of the adjustable arms are substantially equal.
12. 12. The articulated chassis as claimed in any one of claims 8 to 11 wherein adjustment of the arms only occurs upon detection of a predetermined minimum range of motion imparted to the cam.
13. 13. The articulated chassis as claimed in claim 12 wherein the cam is provided with an extension extending from the cam in the direction of the rear chassis, the extension having have a curved surface corresponding to the curvature of the cam and including an indent or recess extending across a part of the arc to allow for a predetermined amount of rotation of the cam without detection by the detector.
14. 14. The articulated chassis as claimed in claim 13 wherein the cam is spring loaded to centre.
15. 15. The articulated chassis as claimed in any one of claims 3 to 14 wherein locking means is provided to lock rotation of the cam.
16. 16. The articulated chassis as claimed in any one of the preceding claims further comprising at least two types of implement attached respectively to the front and to the rear frames, wherein the heavier type of implement or implements is supported on the rear frame having the load bearing wheels, more preferably being close to the pivot point.
17. 17. The articulated chassis as claimed in claim 16 wherein the front frame has at least one cross member extending transversely therefrom for mounting a plurality of spaced apart soil cultivator seed drills.
18. 18. The articulated chassis as claimed in claim 17 wherein at least two cross members extend transversely from the front frame, wherein the soil cultivator seed drills on the first o cross member are staggered with respect to those on the second cross member. C\I
19. 19. The articulated chassis as claimed in any one of claims 16 to 18 wherein a seed and/or o fertilizer container is supported on the rear frame, preferably between the load bearing wheels. a)