Patent Description:
It is known to provide towed agricultural implements, such as mowers, which may be towed from an agricultural vehicle, such as a tractor. Such towed agricultural implements include left hand side and right hand side working implements for processing a crop, the working implements being carried from a central towing structure. A hitch provided on the towed agricultural implement connects the towing vehicle with the towed agricultural implement.

Conveniently a main chassis member of the towed agricultural implement is suspended about a horizontal pivot axis from the hitch. Preferably the horizontal pivot axis is aligned with the lateral centre of gravity of the towed agricultural implement. In practice, this is not always the case. For example for reasons of manufacturing efficiency, a common design of main chassis member may be designed for use with a variety of working implements, for example different mowing units, such as a mower with and without a conditioner unit. Such different working implements will result in the resulting towed agricultural implements all having slightly different centres of gravity offset to some degree from one another. As such the location of the horizontal pivoting axis will be designed to provide a best fit for the most common centres of gravity for a given main chassis member.

While this solution generally works well, in practice it leads to different bearing loads with potential disadvantages as explained below.

The towed agricultural implement is provided with prestressed springs to maintain the towed agricultural implement in a neutral or "zero position" when the towed agricultural implement is in either a headland or transport position. However, where the location of the horizontal pivoting axis is offset from the centre of gravity, these springs are loaded differently. This can lead to different strong deflections in the transport or headland position, especially when cornering. Also the different forces of the springs lead to different strong tracking weights on the sides of the towed agricultural implement, when the towed agricultural implement tilts out of the "zero position". <CIT> discloses a towed agricultural implement provided with an offset center of gravity compensating structure.

It is an advantage of the present invention that a solution to this problem is provided.

According to a first aspect of the present invention, a towed agricultural implement comprises a plurality of working elements carried from a chassis member, a first element for connection of the agricultural implement to a towing vehicle, a second element supporting the chassis member, a pivot pin connecting the first element and the second element and defining a horizontal axis of rotation between the first element and the second element, wherein due to unequal loads resulting from a distribution of a mass of the plurality of working elements a lateral centre of gravity is offset from the axis of rotation characterised in that the first element comprises first and second walls, a generally vertical member extending between the first wall and the second wall, the generally vertical member comprising a tubular support between smaller and larger portions of the generally vertical member, in that the second element is secured to the chassis and comprises a central web separating front and rear panels each provided with bushings, the pivot pin extending through the tubular support and the bushings, the central web also separating first and second side walls, the second element further comprising a pin extending between the first and second side walls, a stop plate located in a predetermined position on the pin, an abutment plate mounted on the pin for abutting the smaller portion of the first element, the biasing member being located on the pin between the stop plate and the abutment plate and in that the towed agricultural implement further comprises a biasing member acting between the smaller portion of the generally vertical member of the first element and the stop plate of the second element wherein the biasing member acts to balance the unequal loads causing a change in the lateral centre of gravity to the horizontal axis of rotation so that each side of the towed agricultural implement is subject to equal bearing loads.

The bearing load compensating structure compensates the unequal bearing loads for different towed agricultural implements with different centres of gravity.

The biasing member has resilient/resilient and damping properties to allow lateral oscillation of the towed agricultural implement to be damped. A further advantage is that swinging up of the agricultural implement in a transport position can be prevented.

Preferably, the stop plate is adjustable on the pin.

More preferably, the biasing member comprises an elastic spring element, for example a helical spring or rubber buffer mounted on a connecting member. Preferably, the working implements comprise cutting units for a mower. Alternatively, the working units comprises cutting units and a conditioner for a mower.

Reference to terms such as longitudinal, transverse and vertical are made with respect to a longitudinal vehicle axis which is parallel to a normal forward direction of travel.

With reference to <FIG>, a schematic view of the forces acting on a known towed agricultural implement is shown. A lateral axis <NUM> of a main chassis member of a towed agricultural implement is provided with a pivot axis <NUM> between the main chassis member and the hitch assembly. The main chassis member is fixed in a neutral or "zero position" by the use of balanced prestressed spring units. However, due to the distribution of a mass of the towed agricultural implement, a lateral centre of gravity <NUM> is offset from the pivot axis <NUM>. This results in an offset load <NUM> on the towed agricultural implement with a larger bearing load <NUM> on a first side of the towed agricultural implement and a smaller bearing load <NUM> on a second side of the towed agricultural implement.

Since the focal points of the working implements, such as mowing units, provided on the towed agricultural implement vary in the transverse direction, these springs are loaded differently. Accordingly, the working implements are not suspended in alignment with the centre of gravity in the transverse direction, and since the working implements are offset from the "zero position" different bearing loads result between the ground and the working implements. Also the uneven loading of the springs may lead to different strong deflections in the transport position, especially when cornering.

Referring now to <FIG>, <FIG>, <FIG> and <FIG>, there are shown elements of a hitch assembly for use in the present invention, including a first headstock element <NUM> and a second intermediate headstock element <NUM> in a neutral position.

The first headstock element <NUM> (<FIG>) comprises a frame structure comprising a substantially triangular back panel <NUM> connected to first and second inclined uprights <NUM>,<NUM>. The first and second inclined uprights are conveniently connected at their upper ends. A first upper hitch fixing is provided at the upper ends of the first and second inclined uprights. Each of the first and second inclined uprights is also provided a with a lower hitch fixing. It will be understood that the upper and lower hitch fixings are used when attaching the towed agricultural implement to a three point hitch of a towing vehicle.

The back panel <NUM> is provided with a longitudinally extending cover member <NUM>. The longitudinally extending cover member <NUM> comprises a generally inclined upper portion <NUM> with first and second side portions <NUM>,<NUM> extending downward at an angle thereto. Each of the first and second side portions <NUM>,<NUM> terminate with an inwardly directed generally horizontal portion <NUM>,<NUM>.

A front wall <NUM> is connected to the free end the cover member <NUM>. An upper part of the front wall <NUM> is inclined and a lower part depends substantially vertically therefrom. A second wall <NUM> is provided offset from the front wall and extends generally parallel to the front wall <NUM>.

Each of the front wall <NUM> and the second wall <NUM> are provided with a protrusion including a circular opening <NUM>,<NUM> offset to one side. A pair of substantially triangular vertical reinforcing members <NUM>,<NUM> are provided, each connecting the inclined upper portion <NUM> of the cover member and the second wall <NUM>. Each of the vertical reinforcing members <NUM>,<NUM> extend from the inclined upper portion <NUM> of the cover member towards the offset circular opening <NUM> of the second wall <NUM>. A generally vertical member extends from the inclined upper portion between the front wall and the second wall. The generally vertical member comprises a first larger portion <NUM> connected to the upper portion <NUM>, a second smaller portion <NUM> and a tubular support <NUM> between the first and second portions <NUM>,<NUM>, the ends of which are adapted, in use, to be aligned with the circular openings <NUM>,<NUM> of the front wall <NUM> and the second wall <NUM>.

The intermediate headstock element <NUM> (<FIG>) comprises a first front panel <NUM> and a second rear panel <NUM> joined by a central web <NUM>. Each of the first front panel <NUM> and the second rear panel <NUM> is provided with a bushing <NUM>,<NUM>. A spring centring structure <NUM> is provided on the central web <NUM>, comprising first and second upstanding elements <NUM>,<NUM> with angled fingers terminating in abutment surfaces <NUM>,<NUM>. Conveniently the first and second upstanding elements <NUM>,<NUM> are held spaced from one another by a suitable reinforcing member <NUM>.

The rear panel <NUM> is provided at an end remote from the central web with a mounting panel <NUM> extending away from and generally parallel to a plane of the central web <NUM>. Reinforcing members <NUM> are provided between the rear panel <NUM> and the mounting panel <NUM>. The mounting panel <NUM> is conveniently provided with a plurality of openings.

The intermediate headstock element <NUM> further comprises first and second side walls <NUM>,<NUM> extending from the central web <NUM> away from the spring centring structure <NUM>. Each of the first and second side walls <NUM>,<NUM> is conveniently provided with a plurality of openings. The openings may conveniently be provided with threaded bushings <NUM>.

In use the first headstock element <NUM> and the intermediate headstock element <NUM> are connected together such that the bushings <NUM>,<NUM> in the intermediate headstock element <NUM> are aligned with the tubular support <NUM> of the first headstock element <NUM> such that a suitable pivot pin <NUM> may extend through the tubular support <NUM> and the bushings <NUM>,<NUM> to support the intermediate headstock element <NUM> from the first headstock element <NUM>. The intermediate headstock element <NUM> is secured to a main chassis member <NUM> of the towed agricultural implement in any suitable manner using the mounting points provided on the intermediate headstock element <NUM>.

A prestressed biasing element <NUM> is mounted within the first headstock element <NUM> between the front and second walls <NUM>,<NUM>. In use, the prestressed biasing element <NUM> extends between the first and second upstanding elements <NUM>,<NUM> of the spring support structure <NUM>. The restressed biasing element <NUM> comprises a elongate member provided with end stops at each end. First and second adjustable stops are provided on the elongate member. First and second biasing members <NUM>,<NUM> are also provided on the elongate member. Each biasing member <NUM>,<NUM> is located between a fixed end stop and an adjustable stop. The biasing members <NUM>,<NUM> may take any suitable form. In the illustrated embodiment, helical springs are shown.

A first end of a generally L-shaped bracing element <NUM> is secured to one of the side portions of the first headstock element <NUM> and a second end of the bracing element <NUM> is secured to the first larger portion <NUM> of the vertical member between the front wall <NUM> and the second wall <NUM>. The bracing element <NUM> extends between the first and second upstanding elements <NUM>,<NUM> of the spring centring structure <NUM> and in use between the adjustable stops of the prestressed biasing element <NUM>.

A drive connection <NUM> for the drive means for the working implements is conveniently mounted to the mounting panel <NUM> of the intermediate headstock element <NUM>. In use, the drive connection <NUM> is connected in any suitable known manner to a PTO of a towing vehicle.

An compensating structure <NUM> is provided on the intermediate headstock element <NUM>. A pin <NUM> extends between the first and second side walls <NUM>,<NUM> of the intermediate headstock element <NUM> and through the second smaller portion <NUM> of the vertical member of the first headstock element <NUM>. The second smaller portion <NUM> is conveniently provided with a cutaway portion to allow the presence of the pin the stop plate <NUM> and the abutment plate <NUM>. A stop plate <NUM> and an abutment plate <NUM> are mounted on the pin <NUM>. The abutment plate <NUM> abuts the smaller portion <NUM>. The stop plate <NUM> is located in a preselected position. Conveniently the pin <NUM> may be threaded, for example it may take the form of a threaded bolt, and the stop plate <NUM> is screwed onto the pin <NUM> into the desired preselected position and the abutment plate <NUM> is slid onto the pin <NUM>. A biasing member <NUM> in the form of an elastic spring element is mounted between the stop plate <NUM> and the abutment plate <NUM>. In the illustrated embodiment, the elastic spring element takes the form of a helical spring. Other suitable means for providing an elastic spring element may be used. For example a rubber buffer may be used as the elastic spring element.

The purpose of the compensating structure can be understood with reference to <FIG>. Like reference numerals are used to refer to like parts.

The forces <NUM> provided by the biasing means in the compensating structure balance the lateral centre of gravity <NUM> to the pivot axis <NUM> such that each side of the towed agricultural implement is subject to equal and reduced bearing loads <NUM>.

In <FIG>, <FIG> and <FIG> the hitch for use in the present invention is shown set up for use with a first towed agricultural implement in which the centre of gravity is on the right hand side of the pivot axis, for example a mower with a conditioner. It can be seen that the biasing member <NUM> in the compensating structure <NUM> has been set up to the left side of the second smaller portion <NUM>.

In the first tilt position of <FIG>, the biasing member <NUM> in the compensating structure <NUM> is compressed as have each of the biasing members <NUM>,<NUM> of the prestressed biasing element <NUM>, by the action of the bracing element <NUM> on the upper biasing member <NUM> and the lower abutment surfaces <NUM> of the fingers on the first and second upstanding elements <NUM>,<NUM> on the lower biasing member <NUM>. In the second tilt position of <FIG>, the biasing member <NUM> of the compensating structure <NUM> is allowed to extend and the biasing members <NUM>,<NUM> of the prestressed biasing element <NUM> are again compressed, by the action of the bracing element <NUM> on the lower biasing member <NUM> and the upper abutment surfaces <NUM> of the of the fingers on the first and second upstanding elements <NUM>,<NUM> on the upper biasing member <NUM>.

In <FIG>, <FIG> and <FIG> the hitch for use in the present invention is shown set up for use for a second towed agricultural implement in which the centre of gravity is on the left hand side of the pivot axis, for example a mower without a conditioner. Like reference numerals are used to refer to like parts. It can be seen that the biasing member <NUM> in the compensating structure <NUM> has been set up to the right side of the second smaller portion <NUM>.

In the first tilt position of <FIG>, the biasing member <NUM> of the compensating structure <NUM> is allowed to extend, whereas each of the biasing members <NUM>,<NUM> of the prestressed biasing element <NUM> are compressed, by the action of the bracing element <NUM> on the upper biasing member <NUM> and the lower abutment surfaces <NUM> of the fingers on the first and second upstanding elements <NUM>,<NUM>. In the second tilt position of <FIG>, the biasing member <NUM> of the compensating structure <NUM> is compressed as are the biasing elements <NUM>,<NUM>, by the action of the bracing element <NUM> on the lower biasing member <NUM> and the upper abutment surfaces <NUM> of the fingers on the first and second upstanding elements <NUM>,<NUM> on the upper biasing member <NUM>.

Claim 1:
A towed agricultural implement comprises a plurality of working elements carried from a chassis member, a first element (<NUM>) for connection of the agricultural implement to a towing vehicle, a second element (<NUM>) supporting the chassis member, a pivot pin (<NUM>) connecting the first element (<NUM>) and the second element (<NUM>) and defining a horizontal axis of rotation between the first element (<NUM>) and the second element (<NUM>), wherein due to unequal loads resulting from a distribution of a mass of the plurality of working elements a lateral centre of gravity is offset from the axis of rotation, characterised in that the first element (<NUM>) comprises first and second walls (<NUM>,<NUM>), a generally vertical member extending between the first wall and the second wall, the generally vertical member comprising a tubular support (<NUM>) between smaller and larger portions (<NUM>,<NUM>) of the generally vertical member,
in that the second element (<NUM>) is secured to the chassis and comprises a central web (<NUM>) separating front and rear panels (<NUM>,<NUM>) each provided with bushings (<NUM>,<NUM>), the pivot pin (<NUM>) extending through the tubular support (<NUM>) and the bushings (<NUM>,<NUM>), the central web (<NUM>) also separating first and second side walls (<NUM>,<NUM>), the second element (<NUM>) further comprising a pin (<NUM>) extending between the first and second side walls (<NUM>,<NUM>), a stop plate (<NUM>) located in a predetermined position on the pin (<NUM>), an abutment plate (<NUM>) mounted on the pin (<NUM>) for abutting the smaller portion (<NUM>) of the vertical member, a biasing member (<NUM>) being located on the pin (<NUM>) between the stop plate (<NUM>) and the abutment plate (<NUM>) and in that the biasing member (<NUM>) acts between the smaller portion (<NUM>) of the generally vertical member of the first element (<NUM>) and the stop plate (<NUM>) of the second element (<NUM>) wherein the biasing member (<NUM>) acts to balance the unequal loads causing a change in the lateral centre of gravity to the horizontal axis of rotation so that each side of the towed agricultural implement is subject to equal bearing loads.