Patent Description:
The invention is suitable for use with an agricultural harvesting machine, in particular, a forage harvester, provided with a chopper drum assembly comprising rotatable chopper drum having a plurality of knives, in use the chopper drum rotating opposite a stationary shear bar. There is a gap between the shear bar and the knives into which crop is fed during harvesting, the fed crop then being chopped between the chopper knives and the shear bar. Such harvesting machines require regular maintenance of the chopper drum assembly and the shear bar in order to maintain the quality of the chopping process.

The chopping of incoming crop causes wear on the chopper knives and on the shear bar of the chopping assembly. This action may also cause the shear bar to become incorrectly adjusted. If chopping is performed using blunt knives and/or with a shear bar that is incorrectly adjusted this leads to a reduction in the chopping quality and increased energy consumption in driving of the chopper drum assembly.

It is therefore necessary at periodic intervals to perform maintenance actions on the chopper drum assembly for example to replace blunt knives and/or to adjust the shear bar in order to obtain a suitable cutting gap. During such maintenance it is important to ensure the replacement chopper knives are located in the correct position. Aligning and fixing in place of the replacement chopper knives can be a time consuming operation.

The present invention has as an advantage that it addresses the above problems. Other advantages will become clear from the following description.

Alternative solutions are disclosed in <CIT>, in which, rather than adjusting the position of the chopper knives on the chopper drum as the chopper knives become worn, discloses both a displaceable shear bar adjustable towards the chopper drum and for a displaceable wear plate adjustable towards the chopper drum in order to maintain the desired separation between the cutting edges of the chopper drum knives and other elements of the chopper drum assembly. A further prior example of a adjustment apparatus for use with a chopper drum of a forage harvester is disclosed in <CIT>.

According to a first aspect of the present invention, in an adjustment apparatus for use with a chopper drum of a forage harvester, according to claim <NUM> is provided, in which when adjusting of the position of at least one chopper knife on a knife support of the chopper drum of a forage harvester relative to a shear bar of the forage harvester, in which forage harvester the chopper drum is supported from a housing and mounted for rotation about a rotational axis and further provided with a plurality of circumferentially spaced knife supports to which at least one chopper knife can be adjustably secured in relation to the shear bar located adjacent the chopper drum, the adjustment apparatus characterised in that the adjustment apparatus comprising a lateral element comprising first and second limbs fixedly secured to at least one location element , the at least one location element being provided with a locating surface for mating or engagement with a receiving surface of the forage harvester, thereby, in use, locating the adjustment apparatus with respect to the chopper drum and at least one radially inwardly directed guide surface, the or each radially inwardly directed guide surface provided on an individual spacer element (<NUM>), in use, with the adjustment apparatus located with respect to the chopper drum, the or each radially inwardly directed guide surface describing an outer path of an unworn chopper knife, the or each spacer element is provided with first and second openings, the lateral element is provided with complementary first and second openings in the region of the or each spacer element, and the or each spacer element comprises first and second portions, the first portion including the radially inwardly directed guide surface, the or each spacer element being adjustably located with respect to the lateral element such that the or each radially inwardly directed guide surface of the adjustment apparatus is adjustably located with respect to the lateral element of the adjustment apparatus.

This has as an advantage that the adjustment apparatus may be calibrated for different diameters of chopper drum.

Preferably, the first opening of the spacer element is provided in the second portion of the spacer element and the first opening of the lateral element is provided in the first limb of the lateral element. More preferably, the second opening of the spacer element is provided in the first portion of the spacer element and the second opening of the lateral element is provided in the second limb of the lateral element.

Preferably the first and second openings of the spacer element are threaded while the first opening of the lateral element is threaded and the second opening of the lateral element is elongate.

Preferably the first limb of the lateral element is provided with a further threaded opening.

Preferably, the adjustment apparatus is provided with first, second and third fastenings for location in the first, second and further openings of the lateral element.

According to a second aspect of the invention a calibration system, according to claim <NUM> is provided, which comprises an adjustment apparatus according to the first aspect of the invention and a chopper drum supported from a housing and mounted for rotation about a rotational axis and further provided with a plurality of circumferentially spaced knife supports to which at least one unworn chopper knife is correctly secured.

Preferably the chopper drum and the housing comprise a part of a forage harvester. Alternatively, the chopper drum and the housing comprise a part of a calibration rig. According to a third aspect of the invention a method of calibration for an adjustment apparatus forming part of the system according to the second aspect of the invention, according to claim <NUM> is provided, the
method comprising the steps of: locating the at least one locating surface of the adjustment apparatus with respect to a receiving surface of the chopper drum housing or a receiving surface of a chopper drum, aligning the at least one locating surface with a side of the chopper drum housing to allow engagement of engagement means to secure the adjustment apparatus in relation to the chopper drum housing, inspecting the spacer elements on the adjustment apparatus adjacent to the chopper drum and adjusting the or each of the spacer elements with respect to the lateral element as required, once all of the spacer elements have been inspected and any necessary action taken, releasing the engagement means and removing the adjustment apparatus.

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>, in a schematic side view the main components of a forage harvester <NUM> are shown. The forage harvester <NUM> is provided with a front attachment <NUM> which contains cutting equipment for cutting a crop. The cut crop is then fed through a series of compression rollers <NUM> in a compression roller housing <NUM> to a chopper drum <NUM> where the crop is chopped into smaller pieces between a shear bar and a plurality of chopper knives mounted on the chopper drum <NUM>. The chopped crop next passes through a first duct <NUM> and, in the illustrated embodiment, is fed through a cracker unit <NUM> where the crop is further crushed and threshed. The harvested crop is then blown upwards along a second duct <NUM> by an accelerator <NUM> and exits through a spout <NUM>. In an alternative embodiment, the chopped crop may optionally pass directly from the chopper drum to the first duct.

As noted, over time chopping of the incoming crop causes wear on the chopper knives and on the shear bar, and can cause the shear bar to become incorrectly adjusted. While it is known to provide knife sharpening apparatus within such forage harvesters, which is operated from time to time to maintain the sharpness of the cutting knives, it remains the case that after repeated sharpening, the cutting knives wear away and the cutting knifes need to be replaced.

It is therefore necessary over time as part of the ongoing maintenance of the chopper drum to perform a number of tasks including i) replacing worn, blunt knives with new knives in a suitable position to ensure correct interaction in use with the shear bar; ii) where knifes may be adjusted rather than replaced, adjusting the position of the knives relative to the shear bar to ensure correct interaction between each knife and the shear bar; and iii) precisely adjusting a location of the shear bar in order to obtain or maintain a suitable cutting gap.

In short, during such maintenance it is important to ensure the (worn or replacement) chopper knives are located in the correct position in relation to a correctly adjusted shear bar to result in proper operation of the chopping drum - both for chopping of crop and to guarantee that the chopper knives are in the correct position to be sharpened by the knife sharpening apparatus.

The present invention relates to an adjustment apparatus for use during such maintenance. In describing the adjustment apparatus of the present invention the term 'inner' is used to describe that portion of the adjustment apparatus which is, in use, oriented toward the chopper drum and 'outer' the opposite. Similarly references to 'upper' and 'lower' are to be understood with the adjustment apparatus in this position.

<FIG> illustrate an adjustment apparatus <NUM> according to a first embodiment of the present invention.

<FIG> shows a frame <NUM> in which a chopper drum <NUM> is mounted. An upper end of the frame <NUM> is provided with a housing <NUM> within which a sharpening apparatus (not shown) may be located. The frame <NUM> is provided with first and second parallel side walls <NUM>,<NUM>. A lower end of each side wall <NUM>,<NUM> is provided with a mounting means to support a shear bar <NUM> in an adjustable manner.

A chopper drum assembly is mounted in central portion of the frame <NUM> supported between the side walls <NUM>,<NUM>.

The frame <NUM> is further provided with further mounting means to enable the frame <NUM> to be located in a suitable position within the forage harvester. Each side wall <NUM>,<NUM> is further provided with a mounting opening <NUM> as described below.

The chopper drum assembly is shown in more detail in <FIG> and <FIG>.

The chopper drum assembly comprises a chopper drum <NUM> supported for rotation about a longitudinal axis on a drive shaft <NUM>. The chopper drum <NUM> is further provided with a plurality of chopper knives <NUM> mounted about a peripheral circumferential surface of the chopper drum <NUM>. The chopper knives <NUM> may be mounted to the chopper drum <NUM> in any suitable manner. Conveniently, a first set of knives extend across a first half of the drum (from a first end to a mid point) and a second set of knives extend across a second half of the drum (from the mid point to a second end).

The adjustment apparatus <NUM> according to the first embodiment of the present invention comprises a lateral element <NUM>. In the illustrated embodiment the lateral element <NUM> is of substantially L-shaped section. The lateral element <NUM> is secured between first and second location elements <NUM>,<NUM>.

Each location element <NUM>,<NUM> corresponds to the other and only one will be described here. Each end of the lateral element <NUM> is fixedly secured in any suitable manner to the location element <NUM>,<NUM>. In the illustrated embodiment (cf <FIG> and <FIG>) tabs projecting from the ends of the lateral element <NUM> are received in corresponding openings (slots or recesses) of the respective location elements <NUM>,<NUM>. An opposite end is provided with a locating surface <NUM>. At least one opening <NUM> for a fastening is provided between the ends of the location element <NUM>. A lower surface of each location element <NUM> is provided with a shoulder <NUM> beneath the region of the lateral element <NUM> in use secured to the location element <NUM>. Each shoulder <NUM> comprises an elongate portion <NUM> and shorter portion <NUM>.

The adjustment apparatus <NUM> further comprises a plurality of spacer elements <NUM>. In the embodiment illustrated three such spacer elements <NUM> are shown. One spacer element <NUM> is located centrally and the other two spacer elements <NUM> are each located adjacent a respective location element <NUM>,<NUM>.

Each spacer element <NUM> is fixedly secured to the L-shaped lateral element <NUM>. Each spacer element <NUM> is generally L-shaped having a generally horizontal portion <NUM> connected to a generally depending portion <NUM>. A lower surface <NUM> of the generally horizontal portion <NUM> extends across an upper surface <NUM> of the lateral element <NUM> (cf <FIG>). An outer surface <NUM> of the generally depending portion <NUM> extends along an inner vertical surface <NUM> of the lateral element <NUM>. A lower part of the generally depending portion <NUM> conveniently comprises a shoulder portion <NUM> such that in use the vertical portion of the lateral element <NUM> is seated between the shoulder portion <NUM> and the lower surface <NUM> of the generally horizontal portion <NUM>. (cf <FIG>).

A lower surface <NUM> of the depending portion <NUM> of the spacer element <NUM> is preferably aligned with the elongate portions <NUM> of the shoulder <NUM> of the location elements <NUM>,<NUM>. A guide surface <NUM> of the depending portion <NUM> of each spacer element <NUM> is shaped to describe the desired path of an unworn chopper knife (cf dotted line in <FIG>).

The upper surface <NUM> of the lateral element <NUM> is conveniently provided with manipulation means <NUM> in the form of two spaced handles. Each of the handles is located between a respective set of spacer elements <NUM>.

In use the adjustment apparatus <NUM> is manoeuvred generally into position using the manipulation means <NUM>. Each of the locating surfaces <NUM> is placed against a suitable surface on the chopper drum assembly, for example a surface of the drive shaft <NUM>.

In an alternative embodiment (not shown) the lateral elements are configured such that each of the locating surfaces instead may be placed against other surfaces of the chopper drum assembly such as the ring flanges securing the chopper drum to the drive shaft <NUM> or shaft bearings provided on the drive shaft.

In a still further alternative embodiment (not shown) the lateral elements are configured such that each of the locating surfaces is placed against a suitable surface of the frame in which the chopper drum is mounted.

It will be understood that given the need for correct alignment of the chopper knives in use, the arcuate inner surfaces <NUM> of each the spacer elements <NUM> are arranged to be concentric with the rotational axis of the drive shaft <NUM>.

The adjustment apparatus <NUM> is then adjusted such that the openings <NUM> in each of the location elements <NUM>,<NUM> align with the mounting openings <NUM> in the respective side walls <NUM>,<NUM> of the frame <NUM>. Suitable fasteners <NUM> are passed through the aligned openings <NUM>,<NUM> (for example threaded fasteners are secured in threaded bores) to locate and fix the adjustment apparatus <NUM> with respect to the frame <NUM> (and so the rotational axis of the drive shaft <NUM> of the chopper drum <NUM>).

Once the adjustment apparatus <NUM> is in the desired position the shear bar <NUM> may be released and adjusted as necessary and then secured into the correct position. As shown in <FIG>, a sectional view taken through one of the location elements <NUM>,<NUM>, the elongate portion <NUM> of the shoulder <NUM> of each location element <NUM>,<NUM> serves to provide a first shear bar adjustment surface by which an upper surface <NUM> of the shear bar <NUM> may be located and the shorter portion <NUM> of each shoulder <NUM> serves to provide a second shear bar adjustment surface by which a side surface of the shear bar <NUM> adjacent the chopper drum <NUM> may be located.

<FIG> shows a section in line with one of the spacer elements.

Where the lower surface <NUM> of the middle spacer element is aligned with the elongate portion <NUM>, since the ends of the shear bar <NUM> are correctly located with respect to the chopper drum <NUM>, a user can swiftly, as a result of visual inspection, determine if the shear bar <NUM> is correctly aligned at the midpoint, that is that the upper surface <NUM> of the shear bar <NUM> mates with the lower surface <NUM> of the middle spacer element <NUM> (that is the shear bar alignment surface formed by the lower surface <NUM>). If it does not, for example because the shear bar <NUM> has become damaged or unevenly worn, the user can replace the shear bar <NUM> as required.

In addition, the position of the position of the chopper knives <NUM> with respect to the shear bar <NUM> may be adjusted by adjusting the edges of the choppers knives <NUM> to bring the edges into contact with the arcuate surface of the inner surface <NUM> of the depending portions of the spacer elements <NUM>. Once each chopper knife <NUM> has been adjusted the chopper drum <NUM> is rotated to bring the next chopper knife <NUM> into proximity with the adjustment apparatus <NUM>.

<FIG> illustrate a second embodiment of an adjustment apparatus <NUM> according to the present invention. The chopper drum assembly of <FIG> corresponds to the chopper drum assembly of <FIG> and like reference numerals are used to refer to like parts. Similarly, to the extent that elements of the second embodiment of the adjustment apparatus correspond to similar elements of the first embodiment of the adjustment apparatus, similar reference numerals are used.

The adjustment apparatus according to the second embodiment of the present invention comprises a first lateral element <NUM>. In the illustrated embodiment the first lateral element <NUM> comprises a bar having a flat lower surface. The first lateral element <NUM> is secured between first and second location elements <NUM>,<NUM>.

Each location element <NUM>,<NUM> corresponds to the other and only one will be described here. Each location element <NUM> is generally arcuate and comprises a first radial member <NUM> and a second radial member <NUM>. Each radial member is provided with at least one opening <NUM> for a fastening. An inner end of each radial member <NUM>,<NUM> is joined by an inner arcuate member <NUM>. An inner surface of the inner arcuate member <NUM> is formed as a locating surface <NUM>. An outer end of each radial member <NUM>,<NUM> is joined by an outer arcuate member <NUM>. The outer end of each first radial member <NUM> is provided with a shoulder <NUM>. The shoulder <NUM> is provided with an elongate part <NUM> and a shorter part <NUM>. The elongate <NUM> part is provided with a cut away portion <NUM> in which an end of the first lateral element <NUM> may be located and secured. The outer end of each second radial member <NUM> is provided with a cut away portion <NUM> in which an end of a second lateral element <NUM> may be located and secured. Each location element <NUM>,<NUM> may be formed in any suitable manner, for example as a unitary part as in the illustrated embodiment. Each lateral element <NUM>,<NUM> may be secured in relation to each location element <NUM>,<NUM> in any suitable manner.

The adjustment apparatus <NUM> further comprises a plurality of spacer elements <NUM>. Each of the spacer elements <NUM> extends between the first lateral element <NUM> and the second lateral element <NUM>. Each spacer element <NUM> is provided at each end with a cut away portion <NUM>,<NUM> to receive one of the lateral elements <NUM>,<NUM>. An arcuate surface <NUM> of each spacer element <NUM> is shaped to describe the desired path of an unworn chopper knife (as shown by the dotted line in <FIG>).

In the embodiment illustrated four such spacer elements <NUM> are shown. Two of the spacer elements <NUM> are located adjacent a respective location element <NUM>,<NUM>. The other two spacer elements <NUM> are located to either side of a central region of the adjustment apparatus <NUM>. From <FIG> it can be seen that two of the spacer elements <NUM> to one side of the adjustment apparatus <NUM> are generally aligned with the chopper knives <NUM> on one side of the chopper drum <NUM> and the other two of the spacer elements <NUM> to the other side of the adjustment apparatus <NUM> are generally aligned with the chopper knives <NUM> on the other side of the chopper drum <NUM>.

In use the adjustment apparatus is manoeuvred generally into position. Each of the locating surfaces <NUM> is placed against a suitable surface on the chopper drum assembly, for example a surface of the drive shaft <NUM> (cf <FIG>).

Given that, as noted above, the arcuate surface <NUM> of each spacer element <NUM> is shaped to describe the desired rotational path of an unworn chopper knife it will be understood that in order to correctly align the chopper knives, the arcuate surfaces <NUM> of each the spacer elements <NUM> are arranged to be concentric with the rotational axis of the drive shaft <NUM>.

The adjustment apparatus <NUM> is then adjusted, as necessary, such that the openings <NUM> in the radial members <NUM>,<NUM> of the location elements <NUM>,<NUM> align with corresponding openings <NUM> in the respective side walls <NUM>,<NUM> of the frame <NUM>.

Suitable fasteners <NUM>,<NUM> are passed through the aligned openings <NUM>,<NUM> to locate the adjustment apparatus <NUM> with respect to the frame <NUM> (and so the rotational axis of the drive shaft <NUM> of the chopper drum <NUM>).

Once the adjustment apparatus <NUM> is in position the shear bar <NUM> may be released and adjusted as necessary and then secured into the correct position. As shown in <FIG>, a sectional view taken through one of the location elements <NUM>,<NUM>, the elongate portion <NUM> of the shoulder <NUM> of each location element <NUM>,<NUM> serves to provide a first shear bar adjustment surface by which an upper surface <NUM> of the shear bar <NUM> may be located.

<FIG> shows a section in line with one of the spacer elements <NUM>. Since the ends of the shear bar <NUM> are correctly located with respect to the chopper drum <NUM>, and the lower ends of the spacer elements (and in particular the lower surface of the first lateral element <NUM> and lower end <NUM> of the spacer elements <NUM> are aligned with the elongate portion <NUM> of the shoulder <NUM> of each location element <NUM>,<NUM>), a user can swiftly, as a result of visual inspection, determine if the shear bar <NUM> is correctly aligned across the working width of the shear bar <NUM>, that is that the shear bar <NUM> mates with a lower surface defined by the lower end <NUM> of the spacer element <NUM> and the lower surface of the first lateral element <NUM> (that is the shear bar alignment surface). If it does not, for example because the shear bar <NUM> has become damaged or unevenly worn, the user can replace the shear bar <NUM> as required.

Also the position of the position of the chopper knives <NUM> with respect to the shear bar <NUM> may be adjusted by adjusting the edges of the choppers knives <NUM> adjacent to the spacer elements <NUM> to bring them into contact with the arcuate surfaces <NUM> of the spacer elements <NUM>. It may be seen that, in comparison with the first embodiment, the longer arcuate surfaces <NUM> of the spacer elements <NUM> of the second embodiment enable adjustment of more chopper knives <NUM> for a particular rotational position of the chopper drum <NUM>. Once each set of chopper knives <NUM> has been adjusted the chopper drum <NUM> is rotated to bring the next set of chopper blades <NUM> into proximity with the adjustment apparatus <NUM>.

<FIG> illustrate a third embodiment of an adjustment apparatus <NUM> according to the present invention. The chopper drum assembly of <FIG> corresponds to the chopper drum assemblies of <FIG> and <FIG> and like reference numerals are used to refer to like parts. Similarly, to the extent that elements of the third embodiment of the adjustment apparatus correspond to similar elements of the first and second embodiments of the adjustment apparatus, similar reference numerals are used.

It can be seen that the third embodiment is most similar to the first embodiment, with the principal difference being the elongate nature of the spacer elements <NUM> and, in particular, it can be seen that the inner surface <NUM> of each spacer element <NUM> extends from a lower point adjacent the generally depending portion of the lateral element <NUM> (in common with the first embodiment) and extends substantially upwards. In practice it is preferred that that the inner surface <NUM> of each spacer element <NUM> extends such that two circumferentially adjacent chopper knifes <NUM> of the chopper drum assembly are covered (in common with the second embodiment).

It will be understood that the advantages of the first and second embodiments also follow from this construction.

The adjustment apparatus may be manufactured in any suitable manner. For example the various elements may be first welded together and then the inner surfaces of the spacer elements and the appropriate shear bar adjustment surfaces milled or otherwise machined to the desired shapes and tolerances.

A fourth embodiment of the present invention is shown in <FIG>. This embodiment is substantially similar to the first embodiment, and to the extent that elements of the fourth embodiment of the adjustment apparatus correspond to similar elements of the previous embodiments of the adjustment apparatus, similar reference numerals are used.

In this embodiment, the spacers <NUM> are adjustable with respect to the lateral element <NUM>. In the illustrated embodiment, the lateral element <NUM> is secured in a fixed position between first and second location elements (only one of which <NUM> is shown in <FIG>). However the limbs of the lateral element <NUM> are provided with first and second openings <NUM>,<NUM> through which the spacer elements <NUM> may be secured to the lateral element <NUM>. The spacer elements <NUM> are further provided with first and second openings <NUM>, <NUM> through which the spacer elements <NUM> and the lateral element <NUM> can be secured together. The lateral element <NUM> is additionally provided with at least one further opening <NUM> through which the position of each of the spacer elements <NUM> can be set with respect to the lateral element <NUM>.

The first opening <NUM> is provided in a substantially horizontal limb of the lateral element and adapted to aligned with the first opening <NUM> in the substantially horizontal portion <NUM> of the spacer element <NUM>. Preferably, the opening in the substantially horizontal portion <NUM> of the spacer element <NUM> comprises a threaded bore adapted to receive a suitable threaded fastener <NUM>, such as a headed bolt. The first opening <NUM> in the substantially horizontal limb of the lateral element <NUM> is sized to allow a shaft of the threaded fastener <NUM> freely to pass through.

The second opening <NUM> is provided by a threaded bore in a depending portion <NUM> of the spacer element <NUM>. The second opening <NUM> in the lateral element <NUM> is provided as a substantially vertically disposed slot. The slot is aligned with the threaded second opening <NUM> in the depending portion <NUM> of the spacer element <NUM>. A threaded headed fastener <NUM> passes through the slot into the threaded bore. It will be understood that in this way the spacer <NUM> may be adjusted substantially vertically with respect to the lateral element <NUM> in a manner to be described.

The further opening <NUM> in the substantially horizontal limb of the lateral element is a threaded bore adapted to receive a threaded headed fastener <NUM>.

The lateral element <NUM> and the location elements are assembled together in any suitable manner. The spacer units <NUM> are then located in an approximate position with respect to the lateral element <NUM> of the adjustment apparatus. It will be understood that the horizontal relationship can be set by inserting the threaded headed fastener <NUM> thorough the opening <NUM> and into the bore <NUM> and tightening the threaded headed fastener <NUM> to draw the spacer against the depending portion <NUM> of the spacer element <NUM>. The second fastener <NUM> can be used to roughly locate the substantially horizontal portion <NUM> of the spacer element <NUM> with respect to the lateral element <NUM>. The third threaded fastener <NUM> can be located in the further opening <NUM> of the lateral element <NUM>.

The adjustment assembly is then placed in position against a chopper drum assembly that does not require adjustment (or a corresponding rig set up to replicate such an assembly). By adjustment of the second and third threaded members <NUM>,<NUM> the vertical positioning of the spacer element <NUM> with respect to the lateral element <NUM> can be adjusted, for example in <FIG> by movement from the position shown in unbroken lines to the position shown in dashed lines.

Claim 1:
An adjustment apparatus for use with a chopper drum (<NUM>) of a forage harvester (<NUM>) when adjusting the position of at least one chopper knife (<NUM>) on a knife support of the chopper drum (<NUM>) of a forage harvester relative to a shear bar (<NUM>) of the forage harvester, in which forage harvester the chopper drum (<NUM>) is supported from a housing and mounted for rotation about a rotational axis and further provided with a plurality of circumferentially spaced knife supports to which at least one chopper knife (<NUM>) can be adjustably secured in relation to the shear bar (<NUM>) located adjacent the chopper drum (<NUM>), the adjustment apparatus further comprises
a lateral element (<NUM>) comprising first and second limbs fixedly secured to at least one location element (<NUM>), the at least one location element (<NUM>) being provided with a locating surface for mating or engagement with a receiving surface of the forage harvester, thereby, in use, locating the adjustment apparatus with respect to the chopper drum (<NUM>) and
at least one radially inwardly directed guide surface, the or each radially inwardly directed guide surface provided on an individual spacer element (<NUM>), in use, with the adjustment apparatus located with respect to the chopper drum (<NUM>), the or each radially inwardly directed guide surface describing an outer path of an unworn chopper knife,
characterized in that,
the or each spacer element (<NUM>) is provided with first and second openings (<NUM>,<NUM>) the lateral element (<NUM>) is provided with complementary first and second openings (<NUM>,<NUM>) in the region of the or each spacer element (<NUM>), and
the or each spacer element (<NUM>) comprises first and second portions, the first portion including the radially inwardly directed guide surface, the or each spacer element (<NUM>) being adjustably located with respect to the lateral element (<NUM>) such that the or each radially inwardly directed guide surface of the adjustment apparatus is adjustably located with respect to the lateral element (<NUM>) of the adjustment apparatus.